hepatic encephalopathy ||

CLINICAL GASTROENTEROLOGY

Series EditorGeorge Y. WuUniversity of Connecticut Health Center, Farmington, CT, USA

For further volumes:http://www.springer.com/series/7672

Kevin D. Mullen ● Ravi K. PrakashEditors

Hepatic Encephalopathy

EditorsKevin D. Mullen, MD, FRCPIDivision of GastroenterologyMetroHealth Medical CenterCleveland, OH, USA

Ravi K. Prakash, MD, MRCPDivision of GastroenterologyMetroHealth Medical CenterCleveland, OH, USA

ISBN 978-1-61779-835-1 e-ISBN 978-1-61779-836-8DOI 10.1007/978-1-61779-836-8Springer New York Dordrecht Heidelberg London

Library of Congress Control Number: 2012936298

© Springer Science+Business Media, LLC 2012All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Humana Press, c/o Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden.The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identi fi ed as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights.While the advice and information in this book are believed to be true and accurate at the date of going to press, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein.

Printed on acid-free paper

Humana Press is part of Springer Science+Business Media (www.springer.com)

We would like dedicate this book to Sheila Sherlock who had a major interest in hepatic encephalopathy and also inspired many people to join the fi eld of hepatology.

vii

Preface

It is with great pleasure that we write this preface. Relatively few books, especially in recent years, have been published on the topic of “Hepatic Encephalopathy” (HE). Considerable changes have occurred in this fi eld over the last few decades so a comprehensive update is in order. We have called upon virtually all of the leaders in this fi eld to contribute with their colleagues chapters on HE in their speci fi c area of expertise.

The fi rst introductory chapter outlines the major changes in nomenclature and classi fi cation in the last few decades. Speci fi cally, a new term, Covert HE, has been introduced to replace the less satisfactory term minimal HE.

The roles of ammonia, neural in fl ammation, general in fl ammation, oxidative stress, and endogenous benzodiazepines in the pathogenesis of HE are discussed by the leading authorities in these areas. This is followed by chapters on the diagnosis of overt and covert (or minimal) HE followed by EEG changes and brain imaging seen in HE.

The treatment section features the long-standing nonabsorbable disaccharides for the treatment of HE. Antibiotic treatment is discussed as well as the newer agent ornithine phenylacetate. We intended to have Gerald Kircheis contribute a chapter on l-ornithine l-aspartate treatment, but he was incapacitated by a signi fi cant medi-cal problem which precluded his participation.

The last section of special topics features a hodgepodge of interesting topics within the fi eld of HE.

We hope you enjoy this new book on “Hepatic Encephalopathy” as much as we did in putting it together.

Cleveland, OH, USA Kevin D. Mullen

ix

Contents

1 Introduction, Nomenclature, and Classi fi cation of Hepatic Encephalopathy ...................................................................................... 1Kevin D. Mullen and Ravi K. Prakash

Part I Pathogenesis

2 Role of Ammonia in the Pathogenesis of Hepatic Encephalopathy ...................................................................................... 7Jan Albrecht

3 Neuroin fl ammation in the Pathogenesis of Hepatic Encephalopathy ................................................................... 19Roger F. Butterworth

4 In fl ammation and Hepatic Encephalopathy ........................................ 35Shabnam S. Shabbir, Amit Singh Seyan, and Debbie Lindsay Shawcross

5 Oxidative Stress in Hepatic Encephalopathy ...................................... 47Arumugam R. Jayakumar and Michael D. Norenberg

6 The Role of Natural Benzodiazepines Receptor Ligands in Hepatic Encephalopathy ................................................................... 71E. Anthony Jones and Kevin D. Mullen

Part II Diagnosis

7 Diagnosis of Overt Hepatic Encephalopathy ....................................... 97Karin Weissenborn

8 Diagnosis of Minimal Hepatic Encephalopathy .................................. 103Jennifer Y. Montgomery and Jasmohan S. Bajaj

x Contents

9 The Electroencephalogram in Hepatic Encephalopathy .................... 113Piero Amodio

10 Brain Imaging in Hepatic Encephalopathy ......................................... 123Rita García-Martínez and Juan Córdoba

Part III Treatment

11 Disaccharides in the Treatment of Hepatic Encephalopathy ............. 141Praveen Sharma and Shiv Kumar Sarin

12 Antibiotic Treatment for Hepatic Encephalopathy............................. 159Kevin D. Mullen and Ravi K. Prakash

13 Ornithine Phenylacetate: A Novel Strategy for the Treatment of Hepatic Encephalopathy ................................................................... 165Maria Jover-Cobos, Nathan A. Davies, Yalda Shari fi , and Rajiv Jalan

Part IV Special Topics

14 Sleep Disorders and Hepatic Encephalopathy .................................... 177Sara Montagnese

15 Hepatic Encephalopathy and Driving .................................................. 187Matthew R. Kappus and Jasmohan S. Bajaj

16 Nutrition and Hepatic Encephalopathy ............................................... 199Manuela Merli, Michela Giusto, and Oliviero Riggio

17 Hepatic Encephalopathy in Patients with Transjugular Intrahepatic Portosystemic Shunt (TIPS)............................................ 211Martin Rössle and Wulf Euringer

18 Quality of Life in Hepatic Encephalopathy ......................................... 221Jillian Kallman Price and Zobair M. Younossi

19 Liver Transplantation and Hepatic Encephalopathy ......................... 233Dileep K. Atluri and Kevin D. Mullen

20 Future of Hepatic Encephalopathy ...................................................... 241Kevin D. Mullen and Ravi K. Prakash

Index ................................................................................................................ 245

xi

Contributors

Jan Albrecht , PhD Department of Neurotoxicology , M. Mossakowski Medical Research Centre, Polish Academy of Sciences , Warsaw , Poland

Piero Amodio , MD Department of Medicine , University Hospital of Padova , Padova , Italy

Dileep K. Atluri , MD, MRCP (UK) Department of Gastroenterology , Metrohealth Medical Center , Cleveland , OH , USA

Jasmohan S. Bajaj , MBBS, MD, MS Department of Gastroenterology, Hepatology and Nutrition , Virginia Commonwealth University and McGuire VA Medical Center , Richmond , VA , USA

Roger F. Butterworth , PhD, DSc Neuroscience Research Unit , Hôpital Saint-Luc (CHUM) , Montreal , QC , Canada

Juan Córdoba , PhD Liver Unit, Department of Internal Medicine , Vall d’Hebron Hospital , Barcelona , Spain

Nathan A. Davies , PhD, BSc UCL Institute of Hepatology , Royal Free Hospital, University College of London , London , UK

Wulf Euringer , MD Department of Radiology , University Hospital Freiburg , Freiburg , Germany

Rita García-Martínez , PhD Liver Unit, Department of Internal Medicine , Vall d’Hebron Hospital , Barcelona , Spain

Michela Giusto , MD Department of Clinical Medicine , University “Sapienza” Roma , Rome , Italy

Rajiv Jalan , MBBS, MD, PhD, FRCPE, FRCP UCL Institute of Hepatology , Royal Free Hospital, University College of London , London , UK

xii Contributors

Arumugam R. Jayakumar , PhD Department of Neuropathology , South Florida Foundation for Research and Education Inc., Miami VA Medical Center , Miami , FL , USA

E. Anthony Jones , MD, DSc Winchester , Hampshire , UK

Maria Jover-Cobos , PhD UCL Institute of Hepatology , Royal Free Hospital, University College of London , London , UK

Matthew R. Kappus , MD Department of Internal Medicine , Virginia Commonwealth University Health Systems and Physicians , Richmond , VA , USA

Manuela Merli , MD Department of Clinical Medicine , University “Sapienza” Roma , Rome , Italy

Sara Montagnese , MD, PhD Department of Medicine , University of Padova , Padova , Italy

Jennifer Y. Montgomery , MD Department of Internal Medicine , Virginia Commonwealth University Health System , Richmond , VA , USA

Kevin D. Mullen , MD, FRCPI Department of Internal Medicine, Division of Gastroenterology , Metrohealth Medical Center , Cleveland , OH , USA

Michael D. Norenberg , MD Department of Pathology, Biochemistry and Molecular Biology , Jackson Memorial Hospital, Miami VA Medical Center, University of Miami Hospital , Miami , FL , USA

Ravi K. Prakash , MBBS, MD, MRCP (UK) Department of Internal Medicine, Division of Gastroenterology , Metrohealth Medical Center , Cleveland , OH , USA

Jillian Kallman Price , MS Outcomes Research Program , Betty and Guy Beatty Center for Integrated Research, Inova Fairfax Hospital , Falls Church , VA , USA

Oliviero Riggio , MD Department of Clinical Medicine , University “Sapienza” Roma , Rome , Italy

Martin Rössle , MD Department of Gastroenterology and Radiology , University Hospital Freiburg , Freiburg , Germany

Shiv Kumar Sarin , MD, DM, FNA, FNASc Department of Hepatology , Institute of Liver and Biliary Sciences , New Delhi , India

Amit Singh Seyan , MBBS, BSc (Hons) King’s College School of Medicine , King’s College London , London , UK

Shabnam S. Shabbir , BSc, MBBS King’s College School of Medicine, King’s College London , London , UK

Yalda Shari fi , MD, BAO, BCh, LRCP, SI, MRCP (UK) UCL Institute of Hepatology , Royal Free Hospital, University College of London , London , UK

xiiiContributors

Praveen Sharma , MD, DM Department of Hepatology , Institute of Liver and Biliary Sciences , New Delhi , India

Debbie Lindsay Shawcross , BSc, MBBS, FRCP, PhD Institute of Liver Studies, King’s College School of Medicine at King’s College Hospital, London, UK

Karin Weissenborn , MD Department of Neurology , Hannover Medical School , Hannover , Germany

Zobair M. Younossi , MD, MPH Beatty Liver and Obesity Research Center , Inova Fairfax Hospital , Falls Church , VA , USA

1K.D. Mullen and R.K. Prakash (eds.), Hepatic Encephalopathy, Clinical Gastroenterology,DOI 10.1007/978-1-61779-836-8_1, © Springer Science+Business Media, LLC 2012

Keywords Hepatic encephalopathy • Terminology • Overt hepatic encephalopathy • Covert hepatic encephalopathy

The area of hepatic encephalopathy (HE) has seen considerable changes in the last decade. Nomenclature and classi fi cation of HE was formalized for the fi rst time with a report by the Hepatic Encephalopathy Consensus group in the World Gastroenterology Congress meeting in Vienna in 1998 [ 1 ] . Terminology was devised (Fig. 1.1 ) and in the ensuing decade we have seen virtually all publications using this system. There was always recognition that this new system of classi fi cation would need periodic updates and a recent meeting in Val David, Quebec has intro-duced some changes (Fig. 1.2 ).

The original rationale to standardize the classi fi cation of HE was simple. Not de fi ning terms like acute and chronic HE was a major source of confusion [ 2 ] . The problem was so bad we elected to totally change the terms to episodic and persistent. Details of the rationale for change have been published [ 3 ] . In addition to the ABC classi fi cation of the three main settings for HE, we further de fi ned the multiaxial classi fi cation which is evident in the enclosed fi gures (Figs 1.1 and 1.2 ).

Since that time there has been a persistent lobby to change the term “minimal HE” to something better re fl ecting the clinical importance of this entity. We endorsed the term “covert HE” in Quebec and this included in this publication from the meeting in Val David, Quebec. The International Society for Hepatic Encephalopathy and Nitrogen (ISHEN) is now the of fi cial authority for issuing updates on terminology and optimum study design in this fi eld of HE [ 4 ] . This society will be working closely with the various international liver societies [American (AASLD), European

K. D. Mullen, MD, FRCPI (*) • R. K. Prakash, MBBS, MD, MRCP (UK) Department of Internal Medicine, Division of Gastroenterology , Metrohealth Medical Center , 2500 Metrohealth Drive , Cleveland , OH 44109 , USA e-mail: [email protected]

Chapter 1 Introduction, Nomenclature, and Classi fi cation of Hepatic Encephalopathy

Kevin D. Mullen and Ravi K. Prakash

2 K.D. Mullen and R.K. Prakash

Fig. 1.1 World Congress of gastroenterology classi fi cation of hepatic encephalopathy

Fig. 1.2 Proposed changes by the International Society for Hepatic Encephalopathy and Nitrogen (ISHEN) metabolism—introduction of the term “Covert HE”

(EASL) and International (IASL)] to provide periodic updates on terminology and study design issues. One major goal is to make sure that ISHEN and other liver societies produce guidelines that are consistent. Ideally one uniform set of guide-lines should be produced with updates every 2–3 years.

The publication of the spectrum of neurocognitive impairment in cirrhosis paper by Bajaj et al. has highlighted a new perspective on HE [ 5 ] . Instead of viewing minimal

31 Introduction, Nomenclature, and Classifi cation of Hepatic Encephalopathy

HE (covert HE) and overt HE as distinct separate entities the idea now is that one evolves into the other. Now that we are beginning to recognize that not all patients reverse HE totally, the neurodegenerative aspect of HE is being included in the SONIC classi fi cation. This may ultimately have a major impact on priority for liver transplan-tation if irreversibility of neurological de fi cits is more formally and consistently identi fi ed. We may reach a point where avoidance of any episodes of overt HE will be the goal of therapy. Hence both treatment and liver transplantation may be instituted earlier in the course of HE in the future [ 6 ] . Clearly, more effective treatment for HE is required since organ supply for liver transplantation is limited. As these concepts evolve, it will become more and more important to diagnose HE in its earliest steps.

Contained in the new perspective on the spectrum of HE is a dif fi cult issue. There is a universal concern about the accuracy of the New Haven Scale in diagnos-ing and quantifying the severity of overt HE. The primary problem is so-called Stage I HE of that scale [ 7 ] . The criteria for diagnosis of Stage I overt HE is subjec-tive and is not consistently applied by physicians. Some patients have mild HE and others do not. Attempts have been to improve “measurement” of Stage I HE by including some more objective measures [ 8 ] . However, in keeping with Kircheis and Haussinger point of view we felt a major change was needed [ 9 ] . Essentially stage I HE as judged by the New Haven Scale has been abolished. Instead we have combined minimal HE with what used to be stage I HE. This “Covert HE” will be primarily diagnosed by psychometric tests and potentially other testing systems such as inhibitory control test (ICT) or critical fl icker fusion (CFF) (see Chap. 8 ). The cut off between covert and overt HE will now be based on disorientation at least to time. The particular element of HE diagnosis can be reliably detected by experi-enced clinicians. The concept of covert and overt HE is essentially the same as the low grade/high grade HE proposed by Haussinger et al. The remaining three grades of the New Haven Scale will be kept but will feature new descriptions (moderate overt HE, severe overt HE, and Comatose HE). It is important to note that covert HE is not just what used to be minimal HE but with the additional aspect of what used to be stage I HE. Purists suggest they can always fi nd neurological abnormalities in patients with Stage I HE but this proposed operational system is closer to reality. No doubt there will be major debates on these proposed changes. As noted earlier it is the intent of ISHEN and the other societies with an interest in HE to revise our approach if new data comes to hand suggesting changes are needed.

Most of the changes proposed earlier will have a direct bearing on the conduction of clinical treatment trials in the future. Choosing end points to evaluate for treat-ment ef fi ciency is crucial in the study design. We must endorse standardized meth-ods of measuring HE and develop proper terminology to allow clear communication at a global level. The last decade has seen progress with standardization of terminol-ogy for HE with general use of the proposed terms in most journals. It will be a more challenging task to agree upon standardization of diagnostic paradigm for the detection and quanti fi cation of the entire spectrum of HE. A major impetus for this will be the Val David accord which has addressed these issues in some detail [ 4 ] . Further progress is anticipated where working parties from upcoming liver meet-ings delegate new guidelines.

http://dx.doi.org/10.1007/978-1-61779-836-8_8


References

1. Ferenci P, Lockwood A, Mullen K, Tarter R, Weissenborn K, Blei AT. Hepatic encephalopathy–de fi nition, nomenclature, diagnosis, and quanti fi cation: fi nal report of the working party at the 11th World Congresses of Gastroenterology, Vienna, 1998. Hepatology. 2002;35(3):716–21.

2. Sanaka MR, Ong JP, Mullen KD. Challenges of designing hepatic encephalopathy treatment trials. Hepatology. 2003;38(2):527–8.

3. Mullen KD. Review of the fi nal report of the 1998 Working Party on de fi nition, nomenclature and diagnosis of hepatic encephalopathy. Aliment Pharmacol Ther. 2007;25 Suppl 1:11–6.

4. Bajaj JS, Cordoba J, Mullen KD, Amodio P, Shawcross DL, Butterworth RF, et al. Review article: the design of clinical trials in hepatic encephalopathy—an International Society for Hepatic Encephalopathy and Nitrogen Metabolism (ISHEN) consensus statement. Aliment Pharmacol Ther. 2011;33(7):739–47.

5. Bajaj JS, Wade JB, Sanyal AJ. Spectrum of neurocognitive impairment in cirrhosis: implications for the assessment of hepatic encephalopathy. Hepatology. 2009;50(6):2014–21.

6. Atluri DK, Asgeri M, Mullen KD. Reversibility of hepatic encephalopathy after liver transplan-tation. Metab Brain Dis. 2010;25(1):111–3.

7. Kircheis G, Fleig WE, Gortelmeyer R, Grafe S, Haussinger D. Assessment of low-grade hepatic encephalopathy: a critical analysis. J Hepatol. 2007;47(5):642–50.

8. Hassanein TI, Hilsabeck RC, Perry W. Introduction to the Hepatic Encephalopathy Scoring Algorithm (HESA). Dig Dis Sci. 2008;53(2):529–38.

9. Haussinger D, Cordoba Cardona J, Kircheis G, Vilstrup H, Fleig WE, Jones EA. De fi nition and assessment of low-grade hepatic encephalopathy. In: Haussinger D, Kircheis G, Schliess F, editors. Hepatic encephalopathy and nitrogen metabolism. The Netherlands: Springer; 2006. p. 423–32.

Part I Pathogenesis


Keywords Ammonia • Cerebral blood fl ow • Brain edema • Glutamine • Amino acidergic neurotransmission

Introduction

There is consensus that excess of gut-derived ammonia which is not cleared from the blood plays an important role in the pathogenesis of HE. However, as discussed elsewhere in this book, a growing body of evidence suggests signi fi cant contribution of other factors, such as proin fl ammatory cytokines and hyponatremia. Moreover, there is a long list of gut-derived toxins that accumulate in the body when the detoxi-fying capacity of the liver is compromised, many of which may enter the brain [ 1 ] . It thus appears worthwhile to distinguish the speci fi c roles of ammonia in inducing HE. This will be done in fi ve discrete sections. The fi rst issue addressed in this chap-ter is the degree of correlation between blood ammonia levels and severity of HE as graded by the West Haven scale (assignment to grades I–IV). The impact of changes in the rate of ammonia generation in the peripheral tissues is brie fl y accounted for. Next, the contribution of ammonia to the speci fi c pathophysiological manifestations of advanced stages of HE is analyzed. The key parameters under evaluation are brain edema, which is the major cause of death in patients with HE accompanying acute liver failure (ALF), and increased cerebral blood fl ow (CBF), which is a caus-ative factor in brain edema. Further, the role of ammonia in the development of cognitive and motor impairment is assessed. Wherever the net effect of ammonia could not be directly evaluated in a clinical setting, its distinct role is demonstrated in experimental animals with “simple” hyperammonemia not complicated by liver

J. Albrecht, PhD (*) Department of Neurotoxicology , M. Mossakowski Medical Research Centre, Polish Academy of Sciences , Pawinskiego 5 , Warsaw , Poland e-mail: [email protected]

Chapter 2 Role of Ammonia in the Pathogenesis of Hepatic Encephalopathy

Jan Albrecht

8 J. Albrecht

damage or asymptomatic animals with experimentally induced chronic liver failure subsequently given ammonia bolus. The effectiveness of therapeutic interventions speci fi cally aimed at reducing blood ammonia level in HE patients or experimental animals is taken as further support to the relative contribution of ammonia.

The section “Cellular and Molecular Mechanisms Underlying Ammonia-Induced Impairment of Brain Function” describes the molecular and biochemical effects of ammonia on the different cell types of the central nervous system (CNS) and on the interactions between these cells. It focuses on the events which can be causally linked to brain edema and to the growing imbalance between neural inhibition and excita-tion. Progression towards neural inhibition is mainly seen in Type C HE. Distinct contributions of ammonia itself and its direct metabolite, glutamine are emphasized.

Correlation Between Ammonia Levels in Blood and/or Its Rate of Production in the Periphery and the Advancement of HE

Most of the studies carried out in the last few decades have demonstrated a rather good correlation between blood ammonia and severity of HE. Occasional deviations from this rule are now interpreted as re fl ecting methodological inaccuracies and/or incompatibilities of the procedures used in different medical centers [ 2 ] . One major controversy of the past was whether arterial or venous blood should be taken for the measurements. It has been argued that when the liver becomes dysfunctional, detoxi fi cation of ammonia mainly occurs in the muscles, disproportionally lowering venous blood ammonia as compared to the arterial blood ammonia. It has also been suggested that partial pressure of ammonia correlates better with the HE grade than blood ammonia. Recently, Ong et al. [ 3 ] compared arterial and venous ammonia con-tent, and arterial and venous partial pressure of ammonia, in a carefully selected group of 121 patients with liver cirrhosis, and demonstrated that blood ammonia measured with any of these four methods correlated equally well with the severity of HE.

Ammonia delivered from the peripheral tissues to blood is mainly derived from glutamine following its degradation by phosphate-activated glutaminase (PAG). There is evidence that the risk of progression of cirrhotic patients to advanced HE is associated with increased ammonia production from glutamine in the intestines [ 4 ] and kidney [ 5 ] . Similarly, it has been demonstrated that enhanced response to oral glutamine challenge test can identify cirrhotics with increased risk of transition to higher grades of HE [ 6 ] . More recently, mutation in the promoter region of PAG has been identi fi ed in in vitro tests which accelerates the transcriptional activity of this gene, i.e., enhances production of PAG molecules [ 7 ] . Cirrhotic patients carrying this mutation show an increased preponderance to develop symptomatic HE [ 7 ] .

Although intracellular ammonia levels in the brain are not amenable to direct testing in HE patients, it is safe to assume that the increase in blood ammonia will lead to a proportional increase in brain ammonia. The current view is that not only ammonia base but also ionized ammonia penetrates the blood–brain barrier (BBB) [ 8 ] . Experiments in an animal model of hyperammonemia revealed a substantially increased extraction of blood ammonia by the brain [ 9 ] .

92 Role of Ammonia in the Pathogenesis of Hepatic Encephalopathy

The Role of Ammonia in Alterations of Cerebral Blood Flow and Development of Cerebral Edema Associated with HE

Brain edema is a frequent complication of ALF and a major cause of death in these patients because it leads to increased intracranial pressure (ICP) and herniation. Both clinical and animal model studies have brought about compelling evidence favoring a direct role of ammonia in inducing brain edema. In a retrospective study, death of ALF patients due to cerebral herniation closely correlated with the arterial ammonia levels [ 10 ] , and a recent prospective study by the same group revealed a good correlation in time and magnitude between arterial hyperammonemia, cere-bral accumulation of osmotically active amino acids and ICP [ 11 ] . Brain edema seen in ALF patients was reproduced in rats with ammonium acetate-induced hyper-ammonemia not complicated by liver failure [ 12, 13 ] and in portacaval-shunted rats which received an ammonia bolus [ 14 ] . Astrocytic swelling is not only associated with ALF [ 15 ] but also with low-degree brain edema accompanying Type C HE [ 16 ] . This phenomenon could also be induced by ammonia in cultured astrocytes [ 17 ] and cerebral cortical slices in vitro [ 18 ] .

While the effects of ALF on CBF in a clinical setting varied in different studies, patients with increased CBF developed brain edema more frequently than those with decreased or unchanged CBF, suggesting causal relation between the phe-nomena [ 19 ] . The role of hyperammonemia in evoking changes in CBF and the role of CBF changes in the development of brain edema were documented in ani-mal model studies. While cerebral hyperemia and brain edema were found absent in asymptomatic portacaval-shunted rats, they were precipitated by subsequent infusion of ammonia [ 20, 21 ] . The sequence in which brain edema and hyperemia occur has not been fi nally established. The current view is that the primary signals (nitric oxide and other as yet not well-de fi ned factors) are derived from the swollen brain cells (astrocytes) which by inducing hyperemia elicit a self-amplifying pro-hyperemic signaling train [ 20, 21 ] . Pharmacological decrease of CBF in hyperam-monemic rats attenuated brain edema, bespeaking the increased CBF as a causative factor [ 22 ] .

Recent evidence suggests the role of a vasogenic component of ammonia-induced brain edema. Studies with the magnetic resonance imaging technique revealed stage- and brain region-dependent development of vasogenic brain edema in rats with acute hyperammonemia [ 23 ] and ALF [ 24 ] . The above studies also have dem-onstrated that regions with vasogenic edema show increases of BBB permeability associated with increased activity of the matrix metalloproteinase 9 (MMP-9). MMP-9 was earlier found to contribute to BBB dysfunction in ALF by disrupting the brain endothelial tight junction proteins, but the speci fi c role of ammonia was not investigated in this study [ 25 ] . A challenging question for future investigations is whether and to what degree the subtle BBB disruption underlying vasogenic brain edema re fl ects direct toxic action of ammonia on the endothelial cells of the BBB similar to the effects of ammonia on astrocytes or neurons.

10 J. Albrecht

Ammonia and Impairment of Cognitive and Motor Functions

HE is associated with impairment of learning and memory. The complexity of the changes makes it dif fi cult to gauge the degree of contribution of ammonia and other pathogenic factors to a given neuropsychological symptom. Nonetheless, in animals, experimentally induced hyperammonemia not complicated by liver impairment have been shown to evoke alterations in some basic learning and cognition tests similar to those noted in animals with HE [ 26 ] . Cyclic GMP (cGMP) is a molecule critically involved in the different aspects of learning and memory, and the activity of NMDA receptor/NO/cGMP pathway is a marker of the cognitive functions. Both impairment of cognitive functions coupled with decrease of cGMP in the brain, and restoration of these functions upon pharmacological elevation of cGMP, are observed in cirrhotic patients and animals with HE and in animals with induced hyperam-monemia in the absence of liver failure [ 26, 27 ] .

HE in cirrhotic patients is associated with impaired motor activity and coordina-tion. These changes are due to the altered functioning of neuronal circuits involving basal ganglia and the cerebral cortex, including altered modulation of these circuits by the metabotropic glutamate receptor (mGluR) activity. The altered response to mGluR activation and the motor function changes observed in rats with chronic liver failure were mirrored in rats with induced hyperammonemia in the absence of liver failure. For example, activation of mGluR1 by excess glutamate in the substan-tia nigra/ventral tegmental area axis is thought to be responsible for hypokinesia in chronic hyperammonemic rats [ 28 ] .

Effectiveness of Blood Ammonia-Reducing Therapies as an Indicator of the Role of Ammonia in HE

As discussed elsewhere in this book, nonabsorbable disaccharides (lactulose) and antibiotics (rifaximin) are the routinely employed ammonia lowering treatment modalities based on the principle of combating gut fl ora. Although the improvement of the status of patients treated with these drugs supports the role of ammonia in the development of HE, the effects of these drugs on speci fi c pathophysiological mani-festations of HE have not been assessed quantitatively. More precise information was recently derived from the experiments with a newly invented drug, ornithine phenylacetate (OP). OP has a two-hit mechanism of action, where l -ornithine acts as a substrate for glutamine synthesis from ammonia in skeletal muscles, while phenylacetate combines with ammonia-derived glutamine to form phenylacetyl glu-tamine, which is subsequently excreted in the kidneys. Treatment of cirrhotic (bile duct ligated) rats with OP for a few hours reduced the originally increased arterial blood ammonia almost back to the control level, and the reduction was correlated with an equally effective attenuation of brain edema [ 29 ] .


Cellular and Molecular Mechanisms Underlying Ammonia-Induced Impairment of Brain Function

Ammonia that enters the brain is metabolized in astrocytes to glutamine in an ATP-consuming reaction catalyzed by glutamine synthetase (GS). Astrocytes that are in a close topographical contact with the cerebral vascular endothelial cells forming the BBB are the primary victim of excess ammonia. The metabolic and molecular changes evoked by ammonia on astrocytes affect the astrocytic–neuronal interactions which impact on neuronal function. However, ammonia also affects the neurons directly. It is beyond the scope of this chapter to discuss the multiple ways in which ammonia affects the general metabolism of astrocytes and/or neurons: in most general terms, astrocytic and neuronal dysfunction under excessive ammonia load is critically coupled to decreased energy metabolism [ 30 ] . The text later focuses on two issues: (a) the mechanisms by which ammonia speci fi cally contributes to astrocytic swelling and subsequent brain edema and (b) how the effects of ammonia on astrocytes and neurons are translated into the shift of balance of neurotransmis-sion to net neural inhibition, which progresses with the advancement of HE.

Role of Ammonia in Astrocytic Swelling and Brain Edema

The current view is that the major metabolic impairments and cell membrane dys-functions produced in astrocytes by ammonia evolve from astrocyte swelling by a vicious cycle of oxidative/nitrosative stress (ONS) and intracellular osmotic imbalance [ 16 ] . Swelling of cultured astrocytes treated with ammonia is invariably associated with intracellular accumulation of reactive oxygen and nitrogen species (RONS), including the highly toxic peroxynitrite [ 20 ] . One contributor to the increased RONS formation in ammonia-treated astrocytes or brain slices is excessive nitric oxide (NO) synthesis which may be associated with the overactivation of NMDA recep-tor, in a self-amplifying mechanism involving excessive glutamate release from astrocytes [ 16 ] . In an in vivo model of hyperammonemia, reduction of brain edema could be achieved upon administration of an NMDA receptor antagonist, memantine to the rat [ 31 ] . Excess of NO activates cGMP synthesis and subsequently increases protein kinase G activity, which also contributes to ammonia-induced astrocytic swelling [ 32 ] . The other contributing factor is the accumulation of reactive oxygen species, mainly the superoxide anion ( • O

2 ) generated by NADPH oxidase [ 16 ] .

Natriuretic peptides (NPs) (atrial natriuretic peptide, C type natriuretic peptide), which are natural components of the brain tissue, reduce RONS production in ammonia-treated astrocytes by reducing NADPH oxidase expression and activity [ 33 ] . This antioxidative effect is speci fi cally mediated by the natriuretic peptide clearance receptor (NPR-C). These NPs and the NPR-C may act as targets for ther-apy development for HE in future. Pharmacological studies demonstrated increased activity of MAP kinases and NF k -B. These act as carriers of downstream signals

12 J. Albrecht

critical for the translation of RONS accumulation to astrocytic swelling [ 34 ] . Ammonia may also contribute to astrocytic swelling by directly interfering with the cell membrane ion and water transport. The phosphorylation-dependent activation and/or increased expression of Na–K–Cl co-transporter 1 (NaKCC1) mediates astrocytic swelling in ammonia-treated astrocytes [ 35 ] and brain edema in rats with experimentally induced ALF [ 36 ] .

There is compelling evidence for increased glutamine accumulation in ammonia-exposed astrocytes which is a key factor mobilizing the vicious circle of ONS and osmotic imbalance associated with HE. Early studies have shown that astrocytic swelling and cerebral edema in rats with hyperammonemia become reduced or even disappear upon co-administration of glutamine synthetase inhibitor, l -methionine- d / l -sulfoximine (MSO) [ 13 ] . In the clinical setting, increased ICP in ALF patients awaiting liver transplantation was found to correlate almost perfectly with the glu-tamine (Gln) content measured in the cerebral microdialysates collected from the patients at the bedside [ 12 ] . The role of glutamine in brain edema has long been interpreted to exert exclusively by its intracellular osmotic effect. The fi nding that glutamine is able to induce mitochondrial permeability transition (mPT) and swelling in isolated mitochondria dependent on uninterrupted glutamine uptake to mitochon-dria [ 37 ] stimulated studies in this fi eld. The essence of the hypothesis, nicknamed the “Trojan horse” hypothesis, is that a portion of newly synthesized glutamine is transported from astrocytic cytosol to mitochondria and is degraded back to ammo-nia: the glutamine derived-ammonia would be responsible for astrocytic swelling and brain edema [ 38 ] . Recently, the paradigm of directly blocking the entry of glu-tamine to brain mitochondria (by the amino acid histidine) was successfully employed to ameliorate brain edema in a rat model of ALF [ 39 ] . Of note, ammonia also promotes astrocytic swelling by upregulating the peripheral benzodiazepine receptor (PBR); recently renamed the 18-kDa translocator protein (see also section “Ammonia and the Neurotransmitter Imbalance in HE” for its other roles) [ 40 ] . Since PBR is located on the outer mitochondrial membrane, it could be an easily accessible target for the glutamine-derived, mitochondrial pool of ammonia.

In summary, it is currently accepted that both the osmotic and the “Trojan horse” mode of action of glutamine contribute to its role as a mediator in ammonia-induced astrocyte swelling and brain edema.

Ammonia and the Neurotransmitter Imbalance in HE

Progression of HE through its different stages from normality excitation to coma is notable in ALF. In contrast, evolution to coma in chronic liver disease is much more a gradual increase in neural inhibition. This shift from neural excitation to inhibition mainly involves changes in the amino acid neurotransmitter systems: the excitatory glutaminergic and the inhibitory GABAergic system, along with some evidence implicating the serotoninergic system as swaying the balance further towards inhi-bition. Studies in hyperammonemic models in vivo and analysis of the effects of


in vitro treatment of astrocytes or neurons strongly suggest that ammonia is largely responsible for the neurotransmission imbalance in HE and disclosed some clues to details of the underlying mechanisms.

The Glutamatergic Transmission

Administration of ammonia to rats results in increased activation of NMDA type of glutamate receptor, which is the primary cause of neuronal damage in these animals [ 23 ] . Ammonia instantly increases extracellular accumulation of glutamate, which may re fl ect ammonia-induced depolarization as a triggering factor for a vicious circle of glutamate-induced NMDA-receptor-dependent glutamate release. Induced hyperammonemia is also associated with increased glutamate exocytosis in astro-cytes [ 41 ] and decreased astrocytic glutamate uptake [ 42 ] , which may partly engage the astrocytic NMDA receptors [ 16 ] , and which further contributes to the increase of extracellular glutamate. Extracellular gluatamate remains elevated under pro-longed exposure to elevated ammonia levels, which eventually leads to NMDA receptor inactivation [ 43 ] . This leads to the depression of the excitatory neurotrans-mission in different brain regions and to the cognitive impairment associated with the decrease of the NO/cGMP pathway. Reduction of cGMP synthesis may also be due to excessive accumulation of glutamine, which limits the availability of arginine for NO synthesis [ 44 ] . As mentioned earlier, hypokinesia, a typical locomotor dys-function accompanying advanced HE, is associated with overactivation of mGluR1 by excess glutamine. The underlying mechanism appears related to altered modula-tion of the microtubule-associated protein 2 (MAP-2) phosphorylation by mGluR1 in the neurons [ 28 ] .

The GABAergic Transmission

Hyperammonemia is associated with an increased GABAergic tone. The underlying mechanism is associated with the increased density of PBR, which are located in astrocytes and control the synthesis of pregnenolone -derived neurosteroids, some of which are positive modulators of the GABA (A)-benzodiazepine receptor complex. Increase of PBR binding coupled with increased synthesis of pregnenolone and its neuroactive derivatives were measured in hyperammonemic mice [ 45 ] . Increased concentrations of pregnenolone and its highly active derivative allopregnenolone were also found in the brain of cirrhotic patients who died in hepatic coma [ 46 ] . Recently, chronic hyperammonemia in rats was observed to speci fi cally increase the GABAergic tone in cerebellum, and this effect was associated with concerted increases of (a) extracellular GABA, (b) a neurosteroid positively modulating the GABAA receptor activation, and (c) the amounts of relevant GABAA receptor sub-units. Most interestingly, pharmacological blockade of GABAA receptors restored the previously reduced ability of cerebellum to synthesize cGMP in response to NMDA receptor stimulation and the cerebellar aspect of learning in these hyperam-monemic rats [ 47 ] . The latter study highlights the role of imbalance between gluta-matergic and GABAergic transmission in HE.

14 J. Albrecht

The Serotoninergic Transmission

Serotonin, the tryptophan-derived inhibitory monoamine, is involved in regulation of sleep, circadian rhythmicity and locomotion. Increased serotoninergic tone has been implicated in the derangement of the above parameters in HE patients and experimental animals. In addition, increased serotonin accumulation and turnover in the brain were positively correlated with the degree of hyperammonemia [ 48 ] . Increased serotonin synthesis in HE-affected brain is associated with increased tryptophan uptake from the circulation, which occurs by exchange with glutamine. Increased tryptophan/glutamine exchange was veri fi ed in the rat cerebral capillaries treated with ammonia in vitro or derived from hyperammonemic rats [ 49 ] .

Concluding Comments: Gaps in the Knowledge of Ammonia Neurotoxicity

The data reported in this chapter strongly support the key role of ammonia in the development of major HE symptoms and elucidate many of the underlying bio-chemical and molecular mechanisms. In general terms, the pattern of responses to ammonia noted in the CNS cells or brain slices in vitro and in the brain of animals with hyperammonemia corresponds relatively well with the changes observed in patients or experimental animals with HE. However, in light of the recent fi nding that hyperammonemia evokes an in fl ammatory response in the CNS engaging the CNS microglia [ 50 ] , data obtained with cultured astrocytes or neurons will have to be interpreted with caution. Moreover, there may be a need for reinterpretation of some older studies in which the brain was regarded as a homogenous entity. As discussed in this chapter, studies of the last few years disclosed a remarkable brain region variability of the responses to ammonia concerning edema [ 23 ] or molecular mechanisms underlying cognition [ 47 ] . However, the contribution of ammonia to some of the common manifestations of HE still remains to be estab-lished beyond doubt. Events such as alterations of the dopaminergic or cholinergic transmission, and changes in the accumulation or intercellular fl uxes of inhibitory neuromodulators: sulfur amino acid taurine, and serotonin metabolites kynurenic acid and oxindole, which frequently accompany HE, have not been analyzed in great detail. This needs to be done under the conditions mimicking hyperammone-mia and in the absence of other factors precipitating HE. Answers to the above questions are needed to fully appreciate the speci fi c role of ammonia in HE.

References

1. Zieve L. Pathogenesis of hepatic encephalopathy. Metab Brain Dis. 1987;2:147–65. 2. Lockwood AH. Blood ammonia levels and hepatic encephalopathy. Metab Brain Dis.

2004;19:345–9.


3. Ong JP, Aggarwal A, Krieger D, et al. Correlation between ammonia levels and the severity of hepatic encephalopathy. Am J Med. 2003;114:188–93.

4. Romero-Gomez M, Ramos-Guerrero R, Grande L, et al. Intestinal glutaminase activity is increased in liver cirrhosis and correlates with minimal hepatic encephalopathy. J Hepatol. 2004;41:49–54.

5. Olde Damink SW, Jalan R, Deutz NE, et al. The kidney plays a major role in the hyperam-monemia seen after simulated or actual GI bleeding in patients with cirrhosis. Hepatology. 2003;37:277–85.

6. Romero-Gomez M, Grande L, Camacho I, et al. Altered response to oral glutamine challenge as prognostic factor for overt episodes in patients with minimal hepatic encephalopathy. J Hepatol. 2002;37:781–7.

7. Romero-Gomez M, Jover M, Del Campo JA, et al. Variations in the promoter region of the glutaminase gene and the development of hepatic encephalopathy in patients with cirrhosis. A cohort study. Ann Intern Med. 2010;153:281–8.

8. Ott P, Larsen FS. Blood-brain barrier permeability to ammonia in liver failure: a critical reap-praisal. Neurochem Int. 2004;44:185–98.

9. Felipo V, Butterworth RF. Neurobiology of ammonia. Prog Neurobiol. 2002;67:259–79. 10. Clemmesen JO, Larsen FS, Kondrup J, et al. Cerebral herniation in patients with acute liver

failure is correlated with arterial ammonia concentration. Hepatology. 1999;29:648–53. 11. Tofteng F, Hauerberg J, Hansen BA, et al. Persistent arterial hyperammonemia increases the

concentration of glutamine and alanine in the brain and correlates with intracranial pressure in patients with fulminant hepatic failure. J Cereb Blood Flow Metab. 2006;26:21–7.

12. Takahashi H, Koehler RC, Brusilow SW, et al. Inhibition of brain glutamine accumulation prevents cerebral edema in hyperammonemic rats. Am J Physiol. 1991;261:H825–9.

13. Hilgier W, Olson JE. Brain ion and amino acid contents during edema development in hepatic encephalopathy. J Neurochem. 1994;62:197–204.

14. Blei AT, Olaffson S, Therrien G, et al. Ammonia-induced brain edema and intracranial hyper-tension in rats after portacaval anastomosis. Hepatology. 2000;19:1437–44.

15. Traber P, Dal Canto M, Ganger D, et al. Electron microscopic evaluation of brain edema in rabbits with galactosamine induced fulminant hepatic failure. Hepatology. 1987;7:1257–61.

16. Häussinger D, Schliess F. Pathogenetic mechanisms of hepatic encephalopathy. Gut. 2008;57: 1156–65.

17. Norenberg MD, Baker L, Norenberg LO, et al. Ammonia-induced astrocyte swelling in pri-mary culture. Neurochem Res. 1991;16:833–6.

18. Zielińska M, Law RO, Albrecht J. Excitotoxic mechanism of cell swelling in rat cerebral corti-cal slices treated acutely with ammonia. Neurochem Int. 2003;43:299–303.

19. Wendon JA, Harrison PM, Keays R, et al. Cerebral blood fl ow and metabolism in fulminant liver failure. Hepatology. 1994;19:1407–13.

20. Master S, Gottstein J, Blei AT. Cerebral blood fl ow and the development of ammonia-induced brain edema in rats after portacaval anastomosis. Hepatology. 1999;30:876–80.

21. Larsen FS, Gottstein J, Blei AT. Cerebral hyperemia and nitric oxide synthase in rats with ammonia-induced brain edema. J Hepatol. 2001;34:548–54.

22. Chung C, Gottstein J, Blei AT. Indomethacin prevents the development of experimental ammonia-induced brain edema in rats after portacaval anastomosis. Hepatology. 2001;34: 249–54.

23. Cauli O, López-Larrubia P, Rodrigues TB, et al. Magnetic resonance analysis of the effects of acute ammonia intoxication on rat brain. Role of NMDA receptors. J Neurochem. 2007;103:1334–43.

24. Cauli O, López-Larrubia P, Rodrigo R, et al. Brain region-selective mechanisms contribute to the progression of cerebral alterations in acute liver failure in rats. Gastroenterology. 2011;140:638–45.

25. Chen F, Ohashi N, Li W, et al. Disruptions of occludin and claudin-5 in brain endothelial cells in vitro and in brains of mice with acute liver failure. Hepatology. 2009;50:1914–23.

16 J. Albrecht

26. Aguilar MA, Miñarro J, Felipo V. Chronic moderate hyperammonemia impairs active and passive avoidance behavior and conditional discrimination learning in rats. Exp Neurol. 2000;161: 704–13.

27. Erceg S, Monfort P, Cauli O, et al. Role of extracellular cGMP and of hyperammonemia in the impairment of learning in rats with chronic hepatic failure. Therapeutic implications. Neurochem Int. 2006;48:441–6.

28. Canales JJ, Elayadi A, Errami M, et al. Chronic hyperammonemia alters motor and neuro-chemical responses to activation of group I metabotropic glutamate receptors in the nucleus accumbens in rats in vivo. Neurobiol Dis. 2003;14:380–90.

29. Davies NA, Wright G, Ytrebø LM, et al. L-ornithine and phenylacetate synergistically produce sustained reduction in ammonia and brain water in cirrhotic rats. Hepatology. 2009;50: 155–64.

30. Hertz L, Kala G. Energy metabolism in brain cells: effects of elevated ammonia concentra-tions. Metabol Brain Dis. 2007;22:199–218.

31. Vogels BAPM, Maas MAW, Daalhuisen J, et al. Memantine, a noncompetitive NMDA recep-tor antagonist improves hyperammonemia-induced encephalopathy and acute hepatic enceph-alopathy in rats. Hepatology. 1997;25:820–7.

32. Konopacka A, Konopacki FA, Albrecht J. Protein kinase G is involved in ammonia-induced swelling of astrocytes. J Neurochem. 2009;109 Suppl 1:246–51.

33. Skowronska M, Zielinska M, Albrecht J. Stimulation of natriuretic peptide receptor C attenu-ates accumulation of reactive oxygen species and nitric oxide synthesis in ammonia-treated astrocytes. J Neurochem. 2010;115:1068–76.

34. Sinke AP, Jayakumar AR, Panickar KS, et al. NFkappaB in the mechanism of ammonia-induced astrocyte swelling in culture. J Neurochem. 2008;106:2302–11.

35. Jayakumar AR, Liu M, Moriyama M, et al. Na-K-Cl cotransporter-1 in the mechanism of ammonia-induced astrocyte swelling. J Biol Chem. 2008;283:33874–82.

36. Jayakumar AR, Valdes V, Norenberg MD. The Na-K-Cl cotransporter in the brain edema of acute liver failure. J Hepatol. 2011;54:272–8.

37. Ziemińska E, Dolińska M, Lazarewicz JW, et al. Induction of permeability transition and swelling of rat brain mitochondria by glutamine. Neurotoxicology. 2000;21:295–300.

38. Albrecht J, Norenberg MD. Glutamine: a Trojan horse in ammonia neurotoxicity. Hepatology. 2006;44:788–94.

39. Rama Rao KV, Reddy PV, Tong X, et al. Brain edema in acute liver failure: inhibition by L-histidine. Am J Pathol. 2010;176:1400–8.

40. Panickar KS, Jayakumar AR, Rama Rao KV, et al. Downregulation of the 18-kDa translocator protein: effects on the ammonia-induced mitochondrial permeability transition and cell swell-ing in cultured astrocytes. Glia. 2007;55:1720–7.

41. Görg B, Morwinsky A, Keitel V, et al. Ammonia triggers exocytotic release of L-glutamate from cultured rat astrocytes. Glia. 2010;58:691–705.

42. Norenberg MD, Hugo Z, Neary JT, et al. The glial glutamate transporter in hyperammonemia and hepatic encephalopathy: relation to energy metabolism and glutamatergic neurotransmis-sion. Glia. 1997;21:124–33.

43. Sánchez-Pérez AM, Felipo V. Chronic exposure to ammonia alters basal and NMDA-induced phosphorylation of NMDA receptor-subunit NR1. Neuroscience. 2006;140:1239–44.

44. Hilgier W, Freśko I, Klemenska E, et al. Glutamine inhibits ammonia-induced accumulation of cGMP in rat striatum limiting arginine supply for NO synthesis. Neurobiol Dis. 2009;35:75–81.

45. Itzhak Y, Roig-Cantisano A, Dombro RS, et al. Acute liver failure and hyperammonemia increase peripheral-type benzodiazepine receptor binding and pregnenolone synthesis in mouse brain. Brain Res. 1995;705:345–8.

46. Ahboucha S, Pomier-Layrargues G, Mamer O, et al. Increased levels of pregnenolone and its neuroactive metabolite allopregnanolone in autopsied brain tissue from cirrhotic patients who died in hepatic coma. Neurochem Int. 2006;49:372–8.


47. Cauli O, Mansouri MT, Agusti A, et al. Hyperammonemia increases GABAergic tone in the cerebellum but decreases it in the rat cortex. Gastroenterology. 2009;136:1359–67.

48. Lozeva V, Montgomery JA, Tuomisto L, et al. Increased brain serotonin turnover correlates with the degree of shunting and hyperammonemia in rats following variable portal vein steno-sis. J Hepatol. 2004;40:742–8.

49. Hilgier W, Puka M, Albrecht J. Characteristics of large neutral amino acid-induced release of preloaded glutamine from rat cerebral capillaries in vitro: effects of ammonia, hepatic enceph-alopathy and g -glutamyltranspeptidase inhibitors. J Neurosci Res. 1992;32:221–6.

50. Rodrigo R, Cauli O, Gomez-Pinedo U, et al. Hyperammonemia induces neuroin fl ammation that contributes to cognitive impairment in rats with hepatic encephalopathy. Gastroenterology. 2010;139:675–84.


Keywords Neuroin fl ammation • Hepatic encephalopathy • Liver failure • Cirrhosis • Ammonia • Proin fl ammatory cytokines • Microglia

Introduction

Central nervous system (CNS) complications of liver failure include hepatic encephalopathy (HE) and brain edema. Depending upon the etiology and chronicity of the liver failure, brain edema may be low grade (cirrhosis) or high grade (acute liver failure, ALF); the latter may result in intracranial hypertension and brain herniation, one of the leading causes of mortality in ALF. HE is a neuropsychiatric syndrome that occurs in both cirrhosis and in ALF and is characterized by disturbance of both cognitive and motor function starting with personality changes and sleep disturbances progressing through more severe cognitive and motor symptoms to stupor and coma. In ALF, progression to severe stages of HE may occur in a matter of days. Since the appearance of CNS symptoms in liver failure frequently heralds a poor prognosis, potentially having a signi fi cant impact on quality of life, on clinical management strategies, on liver transplant priority, and on patient survival, effective therapies are urgently needed. The design of such therapies fi rst requires a knowledge of the underlying pathophysiological mechanisms.

In spite of many decades of study, the mechanisms responsible for HE and brain edema in liver failure are still not completely understood. A great deal of attention continues to be focused on ammonia as the culprit toxin implicated in the pathogen-esis of these CNS complications and agents with properties aimed at reduction of

R.F. Butterworth, PhD, DSc (*) Neuroscience Research Unit , Hôpital Saint-Luc (CHUM) , 1058 St. Denis , Montreal , QC , Canada H2X 3J4 e-mail: [email protected]

Chapter 3 Neuroin fl ammation in the Pathogenesis of Hepatic Encephalopathy

Roger F. Butterworth

20 R.F. Butterworth

circulating ammonia remain the mainstay of clinical management and therapy. However, recent research in both ALF patients as well as in patients with cirrhosis in addition to studies in experimental animal models of these conditions strongly suggests that in fl ammation, acting alone or in concert with ammonia, may also play an important role in the pathogenesis of the CNS complications of liver failure.

Glial Pathology in Liver Failure

The CNS is composed of two major cell types, neurons and glial cells, and the latter consist of astrocytes, oligodendrocytes, and microglia. Liver failure results in glial (rather than neuronal) pathology, the nature of which is dependent upon the type (acute or chronic) and severity of liver failure. Systematic studies in material from patients with ALF reveal swelling of astrocytes [ 1 ] leading to cytotoxic brain edema (Fig. 3.1a ).

In contrast, end-stage chronic liver failure results in pathological changes to astrocytes known as Alzheimer type 2 astrocytosis characterized by nuclear enlarge-ment, margination of chromatin, and glycogen depletion (Fig. 3.1b ). Brain edema may also occur in chronic liver failure but the magnitude of the edematous changes in this case is modest and more focal in nature affecting, for example, the corticospinal tract [ 2 ] . Neuronal pathology has also been described in end-stage chronic liver disease consisting primarily of thalamic and cerebellar lesions due to nutritional de fi cits related to liver failure [ 3, 4 ] . Although neuronal degeneration in the form of acquired non-Wilsonian neurodegeneration or postshunt myelopathy has been reported in cirrhosis, these cases are relatively rare and it is generally concluded that the neuronal loss in chronic liver failure is, in most cases, insuf fi cient to account for the symptoms of HE.

More recently, alterations of a second cell type of the glial lineage have been reported. Activation of microglia was fi rst reported in 2005 in brains of experimental animal models of ALF resulting from liver ischemia [ 5 ] and has since been con fi rmed both in liver ischemia animals [ 6 ] and in animals with ALF resulting from toxic liver injury [ 7 ] . Microglia are the immunomodulator cells of the brain being bone marrow-derived myeloid lineage cells. In the absence of an in fl ammatory stimulus, microglia remain quiescent, being involved principally in surveillance (the so-called resting phenotype). However in the presence of an in fl ammatory stim-ulus, these cells become reactive (the “activated” phenotype) with the task of pre-vention and control of CNS damage due to altered homeostasis associated with a wide range of insults and/or cell death. Activation of microglia is indicative of neuroin fl ammation and is observed in a wide range of neuroin fl ammatory disorders including multiple sclerosis and the AIDS-dementia complex and also in disor-ders such as stroke and Alzheimer’s disease suggesting the presence of a signi fi cant neuroin fl ammatory component in the pathogenesis of the neurological symptoms in these disorders also. Subsequent to the original reports of microglial activation in brain in experimental ALF, similar fi ndings have been reported in human ALF

213 Neuroinfl ammation in the Pathogenesis of Hepatic Encephalopathy

brain [ 8 ] as well as in the brains of animals with bile-duct ligation [ 9 ] or end-to-side portacaval shunts [ 10 ] suggesting that neuroin fl ammation is a signi fi cant component of HE in both acute and chronic liver failure.

Neuroin fl ammation in Acute Liver Failure

A signi fi cant correlation exists between the presence of the systemic in fl ammatory response syndrome (SIRS) and the severity of CNS complication of ALF [ 11 ] . Circulating levels of TNF- a are invariably increased in ALF patients [ 12 ] and TNF

Fig. 3.1 ( a ) Electron micrograph of cerebral cortex from a patient who died in acute liver failure (ALF) resulting from acetaminophen hepatotoxicity. Perivascular astrocytes ( A ) are markedly swollen (reprinted from Kato et al. [ 1 ] , with permission from John Wiley & Sons, Inc.). ( b ) Alzheimer type II astrocytosis (Alz) in prefrontal cortex of a 56-year-old cirrhotic patient who died in hepatic coma. N normal astrocyte

22 R.F. Butterworth

gene polymorphisms have been reported to in fl uence the clinical outcome in these patients [ 13 ] . Moreover, decreases in TNF- a production have been shown to be protective against the development of severe HE in patients with ALF resulting from acetaminophen ingestion [ 13 ] . Increased plasma concentrations of TNF- a are also associated with motor co-ordination de fi cits in animals with thioacetamide-induced ALF [ 14 ] . However, although invariably increased in human and experi-mental ALF, plasma cytokine pro fi les in experimental ALF resulting from toxic liver injury show both similarities and differences that are dependent upon the nature of the toxin [ 15 ] .

Although systemic in fl ammation has been well established for over a decade, evidence of neuroin fl ammation in liver failure was not provided until the publication of a report suggestive of increased production of proin fl ammatory cytokines in brain

Fig. 3.2 Microglial activation in two different experimental animal models of ALF at coma stages of encephalopathy. ( a ) The hepatic devascularized rat. ( b ) The mouse with azoxymethane-induced toxic liver injury. Microglial activation revealed by OX-42 immunohistochemistry in frontal cortex of ALF animals (for further details, see refs. [ 6, 7, 28 ] )


in ALF patients [ 16 ] who measured TNF- a , IL-1 b , and IL-6 in blood sampled from an artery and a reverse jugular catheter in 16 patients with ALF primarily due to acetaminophen hepatotoxicity. A signi fi cant correlation was observed between arterial cytokine levels and intracranial hypertension; brain cytokine ef fl ux was noted, consistent with brain cytokine production in these patients. Unequivocal evidence of neuroin fl ammation was subsequently provided by studies reported by Jiang et al. [ 6 ] , who demonstrated microglial activation (see above) and concomitant increases in expression of genes coding for proin fl ammatory cytokines in experimental ALF in the rat resulting from hepatic devascularization. In the study by Jiang et al. [ 6 ] , increases in expression of the major histocompatibility complex class 11 antigen marker CD11b/c (OX-42) were observed (Fig. 3.2a , b), a feature that is characteristic of microglial activation (Fig. 3.2a ). In this experimental model of ALF, microglial activation was found to occur early in the progression of the disorder and to increase signi fi cantly as HE and brain edema developed. Similar fi ndings were subsequently reported in mice with ALF due to azoxymethane-induced liver injury [ 7 ] (Fig. 3.2b ).

Neuroin fl ammation in Cirrhosis

Patients with cirrhosis are prone to infection due to their functionally immunosup-pressed state and impaired host defense capabilities, and the presence of infection in this patient group has the potential to complicate the clinical course leading to encephalopathy, multiple organ failure, and death [ 17 ] .

Moreover, while loss of liver function predisposes cirrhotic patients to the development of infection, once established, sepsis has the potential to cause deterioration of liver function resulting in a vicious cycle that invariably results in SIRS accompanied by increased circulating levels of TNF- a , IL-1 b , and IL-6. Cytokine synthesis in cirrhosis may be triggered by a range of in fl ammatory stimuli including gut-derived bacterial translocation, infection, increased hepatic cytokine production, and/or decreased renal cytokine clearance. The cells implicated include activated phagocytic and nonphagocytic cells such as monocytes, lymphocytes, neutrophils, and Kupffer cells of the liver.

Concentrations of circulating cytokines such as TNF- a are higher in decompensated vs. compensated cirrhosis and the magnitude of the increases is predictive of the severity of the encephalopathy [ 12 ] . Moreover, the presence of SIRS exacerbates the neuropsychological effects of induced hyperammonemia in cirrhosis [ 18 ] .

A major contribution of increased circulating TNF- a to the pathogenesis of HE in cirrhosis is supported by fi ndings of increased serum levels of the cytokine in a wide range of other encephalopathies including those related to the AIDS virus, cerebral malaria, meningitis, in fl uenza virus, sepsis, and multiple organ failure [ 19 ] .

A role for in fl ammation in the pathogenesis of minimal hepatic encephalopathy (MHE) was suggested by results of a study in 84 cirrhotic patients in which neurop-sychological testing was performed before and after induction of hyperammonemia by administration of a solution mimicking the amino acid composition of hemoglobin.

24 R.F. Butterworth

The presence and severity of MHE in these patients was found to be independent of the severity of liver disease or serum ammonia concentrations; however, circulatory markers of in fl ammation were signi fi cantly higher in patients with MHE [ 20 ] . In a second study by the same group, ten cirrhotic patients were studied after admission with clinical evidence of infection and following its resolution; induced hyperam-monemia resulted in signi fi cant worsening of neuropsychological test scores in patients showing evidence of SIRS but not after its resolution [ 18 ] . Another study showed that infection and systemic in fl ammation in cirrhotic patients, but not hyper-ammonemia, were associated with grades 3 and 4 HE [ 21 ] .

In contrast to the clear evidence of a neuroin fl ammatory response in ALF, evidence for neuroin fl ammation in cirrhosis is incomplete and, to date, is restricted to studies in animal models of MHE. In a study by Cauli et al. [ 22 ] , end-to-side portacaval anastomosis in the rat was found to result in increased brain concentrations of the proin fl ammatory cytokine IL-6 as well as increased activities of other proin fl ammatory markers such as cyclooxygenese and inducible nitric oxide synthase (iNOS). However, microglial activation was not assessed in the brains of these animals and improvement of learning skills followed ibuprofen was found to occur without signi fi cant reduction in brain cytokine levels. In a more recent study by Brück et al. [ 23 ] , locomotor de fi cits in rats following portal vein ligation were accompanied by increases in expression of the gene coding for the proin fl ammatory cytokine IL-6 but no evidence of microglial activation was observed in the brains of these animals. The identity of the cell responsible for increased IL-6 gene expression was not identi fi ed in this study. In contrast, these studies in portocaval shunted or portal vein ligated rats in which a clear role for neuroin fl ammation is still lacking, studies in bile duct-ligated mice [ 9 ] or rats [ 10 ] show clear evidence of neuroin fl ammation characterized by microglial activation established using a range of reliable cell-speci fi c markers and increased brain concentrations of proin fl ammatory cytokines. In the study of bile duct-ligated rats, microglial activation was found to manifest brain region selectivity.

Synergy Between Ammonia and Proin fl ammatory Mechanisms

There is increasing evidence to support the notion that ammonia-related mechanisms may act in concert with proin fl ammatory mechanisms in a complex series of steps resulting in the CNS complications of liver failure. Not only does the presence of systemic infection/in fl ammation have the potential to result in deterioration of liver function and consequently increased hyperammonemia (see above), but a signi fi cant correlation exists between circulating levels of ammonia and TNF- a in liver failure and both are independent predictors of HE severity [ 12 ] . Evidence for ammonia–proin fl ammatory cytokine synergy is also emerging from studies in experimental animal models of liver failure. For example, bile duct ligation in the mouse [ 9 ] and rat [ 24 ] affords reproducible animal models of in fl ammatory liver injury character-ized by modest hyperammonemia, increased levels of circulating proin fl ammatory cytokines, and neurobehavioral symptoms. In one study, bile duct ligation in the rat


resulted in increased circulating levels of TNF- a and IL-6 concomitant with motor incoordination and superimposed diet-induced hyperammonemia led to worsening of the motor de fi cit in these animals [ 24 ] .

Based upon studies with cultured astrocytes and microglial cells, it has been suggested that ammonia may cause increases in the production and/or release of proin fl ammatory cytokines. However, the effects of ammonia on cytokine release are dependent upon the cell type and on the nature of the cytokine. For example, exposure of human CHME-5 microglial cells to ammonia resulted in decreased secretion of the stimulated release of IL-6 but enhanced secretion of IL-8 [ 25 ] ; on the other hand, in GL-15 astroglioma cells, stimulated release of TNF- a was decreased by exposure to ammonia. These fi ndings were not con fi rmed in studies by Andersson et al. [ 26 ] , working with microglial-enriched and astroglial-enriched primary cultures who were unable to fi nd any signi fi cant effects of ammonia on the release of these or other proin fl ammatory cytokines.

An important function of astrocytes, and possibly also microglial cells, is the rapid removal of neuronally released glutamate. This mechanism represents the major inactivation step in the regulation of the glutamatergic neurotransmitter system. For this purpose, astrocytes and microglia express high af fi nity, high capacity glutamate transporters, the most abundant of which, EAAT-2 was previously found to be decreased in experimental ALF [ 27 ] . Moreover, administration of the proin fl ammatory agent lipopolysaccharide (LPS) to rats with ALF due to liver ischemia results in further losses in expression of EAAT-2 in brain and more rapid progression of HE and brain edema [ 28 ] . Studies in cultured astrocytes reveal that exposure to either ammonia [ 29 ] or proin fl ammatory cytokines [ 30 ] causes loss of expression of astrocytic glutamate transporters and a consequent reduction in capacity for high af fi nity glutamate uptake.

More recent studies provide evidence for ammonia–cytokine synergism at the cellular/molecular level in brain [ 31 ] . Exposure of primary cultures of cortical astrocytes to recombinant IL-1 b and ammonia resulted in signi fi cant increases in expression of both heme oxygenase-1 (HO-1) and iNOS. Furthermore, the effects were additive suggestive of synergism.

Liver–Brain Proin fl ammatory Signaling

The nature of the signaling between the failing liver and the brain leading to central neuroin fl ammation in liver failure remains unknown. On the one hand, there is evidence to suggest that systemic proin fl ammatory mechanisms may initiate the signaling process via one of several mechanisms that include (1) direct transfer of cytokines by way of active transport, (2) interaction with receptors on circum-ventricular organs lacking a blood–brain barrier, or (3) by activation of afferent neurons of the vagus nerve. In addition, it has been proposed that systemic in fl ammatory signals have the potential to result in increased permeability of the blood–brain barrier to cytokines in liver disease [ 21 ] . Direct evidence for this

26 R.F. Butterworth

intriguing possibility, however, is not currently available. More recently, using an animal model of biliary cirrhosis, D’Mello et al. [ 9 ] demonstrated that activation of cerebrovascular endothelial cells by peripherally administered TNF- a stimulated microglia to produce monocyte chemotactic protein-1 (MCP-1) that mediates the recruitment of monocytes into the brain with subsequent production of TFN- a . Whether these signaling mechanisms are modi fi ed by acute or chronic liver failure has not been established.

In addition to systemic proin fl ammatory signals, there is evidence to suggest that toxins generated by the failing liver (other than cytokines) may also play a role in the pathogenesis of neuroin fl ammation in liver failure. A wide range of molecules with the potential to threaten the functional integrity of the brain have the capacity to trigger the transformation of microglia from the resting to the active state. Such molecules include ammonia, lactate, glutamate, manganese, and neurosteroids [ 32 ] , all of which have been reported to be increased in concentration in the brain in liver failure. Despite the inconsistent fi ndings with respect to the effects of ammonia on proin fl ammatory cytokine release by microglial cells in culture [ 26 ] , a recent study clearly demonstrated that hyperammonemia in the absence of liver disease resulted in microglia activation of a comparable magnitude and regional distribution in brain to that observed in the bile duct-ligated rat and that hyperammonemia and bile duct ligation led to comparable cognitive and motor impairment [ 10 ] . Together, these fi ndings suggest that the ammonia molecule per se may not have been the entity responsible for the neuroin fl ammatory consequences of hyperammonemia.

Exposure of cultured cells to lactate in concentrations equivalent to those described in brain in acute [ 33 ] or chronic [ 34 ] liver failure led to several-fold increases in release of TNF- a and IL-1 b [ 26 ] . Increased brain lactate in liver failure has been attributed to an inhibitory effect of ammonia on alpha-ketoglutarate dehy-drogenase resulting in impaired cellular oxidative metabolism [ 35 ] and increased brain lactate synthesis signi fi cantly correlates with severity of encephalopathy, with the presence of brain edema and with microglial activation and cytokine production in brain in ALF [ 6, 36 ] . A single report suggests that manganese toxicity also has the potential to lead to microglial activation [ 37 ] . Manganese deposition is a consistent feature of cirrhosis, deposition being greatest in basal ganglia structures of the brain [ 38 ] but whether the concentrations of manganese reported in brain in liver failure are suf fi cient to cause neuroin fl ammation has not been ascertained.

Neuroin fl ammation and the CNS Complications of Liver Failure: The Neurosteroid Connection

A consistent fi nding in both acute and chronic liver failure is increased expression in brain of the so-called translocator protein (TLP), previously known as the “peripheral-type benzodiazepine receptor.” Increased TLP expression occurs in brain in human HE [ 39, 40 ] as well as in experimental animal models of either acute [ 41 ] or chronic [ 42, 43 ] liver failure. However, the identity of the neural cell(s)


expressing increased TLP has not yet been de fi nitively established. Both astrocytes and microglia express transcripts for TLP and, prior to the discovery of microglial activation in brain in ALF [ 6, 44 ] , it had been generally assumed that increased TLP expression was the consequence of the activation and/or proliferation of astro-cytes. However, a review of the literature fails to provide any convincing evidence of this. For example, expression of the astrocyte marker protein glial fi brillary acidic protein (GFAP) is decreased in brain in both experimental [ 45 ] and human [ 46 ] liver failure and morphologic studies, while showing alterations of astrocyte integrity such as swelling or Alzheimer-type II changes [ 47 ] show no clear evidence of an activated state. Based upon these fi ndings, it is unlikely that the increased TLP sig-nal observed in brain in liver failure is a uniquely astrocytic phenomenon and there are reasons to suspect that activations of microglia are alternatively (or additionally) also implicated. This notion is strengthened by the observation that increased signals in position emission tomography (PET) studies using the TLP ligand 11-C-PK11195 in neurological disorders, such as multiple sclerosis and in AIDS-dementia complex, have been attributed to microglial rather than astrocytic activation [ 48 ] .

Activation of TLP results in increased transport of cholesterol across the mitochondrial membrane, a step that constitutes the initial process in the synthesis of a novel class of compounds known as “neurosteroids.” Neurosteroids are potent activators of a range of neurotransmitter receptors, and one neurosteroid, allopreg-nanolone (Fig. 3.3 ), is an extremely high af fi nity agonist for the GABA-A receptor with consequent potent neuroinhibitory and sedative properties.

Increased concentrations of allopregnanolone have been reported in autopsied brain tissue of cirrhotic patients who died in HE but were within normal limits in those patients without HE (Fig. 3.4 ) suggestive of a role for allopregnanolone in the pathogenesis of HE in chronic end-stage liver failure. Moreover, increased brain concentrations of GABA-A receptor agonist neurosteroids such as allopregnano-lone offer an alternative explanation for the phenomenon of “increased GABAergic tone” in HE which had previously been attributed to increased brain concentrations of “endogenous benzodiazepines.”

Fig. 3.3 Structure of allopregnanolone, a neurosteroid synthesized in brain having potent neuroinhibitory properties by virtue of its agonist action at the postsynaptic GABA-A receptor (adapted from Ahboucha et al. [ 49 ] , with permission from John Wiley & Sons, Inc.)

28 R.F. Butterworth

Evidence of a link between microglial activation, TLP induction, and neurosteroid formation is provided by reports of the existence of all three processes in both experimental and clinical material. Brains of patients with chronic liver failure express increased quantities of TLP assessed either biochemically [ 39 ] or using PET [ 40 ] as well as increased concentrations of allopregnanolone [ 49 ] . Moreover, portacaval anastomosis in the rat leads to increased expression levels of TLP [ 42, 43 ] , increased brain levels of neurosteroids [ 50 ] , and microglial activation [ 51 ] . It has been demonstrated in studies using cultured cells that exposure to liver disease-related toxins such as ammonia and manganese leads to upregulation of TLP sites [ 52, 53 ] . Exposure of these cells to proin fl ammatory cytokines also leads to upregu-lation of TLP [ 54 ] suggesting that ammonia and proin fl ammatory cytokines may act synergistically to produce increased brain concentrations of inhibitory neurosteroids leading to HE in liver failure.

Diagnostic and Therapeutic Implications

Whatever the ultimate mechanism responsible, the consistent fi ndings of induction of central neuroin fl ammatory processes in acute and chronic liver diseases have the potential to impact signi fi cantly on diagnostic, management, and treatment options for the future. For example, the demonstration of microglial activation could stimulate the use of diagnostic neuroimaging techniques such as PET. Activated microglia express transcripts for TLP and the extent of neuroin fl ammation is currently assessed in a wide range of neurological disorders, including multiple sclerosis and the AIDS-dementia complex, by PET using the TLP ligand [11C]-PK11195.

Fig. 3.4 Increased concentrations of allopregnanolone in autopsied brain tissue from cirrhotic patients who died in hepatic coma (HE) compared to age-matched controls and nonencephalo-pathic cirrhotic patients (LD). Increased brain concentrations of allopregnanolone likely form the basis of the phenomenon of “increased GABAergic tone” in HE UC: Uremic coma (adapted from Ahboucha et al. [ 49 ] , with permission from John Wiley & Sons, Inc.)


Increased binding sites for this PET ligand have already been reported in cirrhotic patients with HE [ 40 ] , with particular intense signals observed in anterior cingulate cortex, a structure known to be associated with the control of attention (Fig. 3.5 ). These fi ndings suggest a potential application of 11C-PK11195 PET for the assess-ment of neuroin fl ammation in brain in relation to cognitive dysfunction in end-stage chronic liver disease.

Studies show that existing therapies for the treatment of HE in acute or chronic liver failure that were presumed to act by lowering levels of circulating ammonia may also act by reducing levels of proin fl ammatory cytokines. There are several

Fig. 3.5 Microglial activation in patients with acute or chronic liver failure. ( a ) HLA-DR (CR3/43) immunostaining in a patient with ALF (patient material provided by Dr. Radhakrishan Dhiman, PGIMER, Chandigarh, India) and ( b ) neuroin fl ammation in a patient with mild HE by position emission tomography. Left : T1-weighted MRI; Right : Increased [11C]-R-PK11195 binding sites in the frontal lobe particularly in the anterior cingulate cortex (ac) consistent with microglial activation and neuroin fl ammation in this patient (provided by Dr. Simon Taylor-Robinson, Imperial College, London, UK)

30 R.F. Butterworth

such treatments. For example, treatment of cirrhotic patients with lactulose leads to decreased severity of HE and reductions of both circulating ammonia and TNF- a [ 12 ] and use of the albumen dialysis (MARS) system in patients with ALF resulted in removal of TNF- a and in clinical improvement with better outcome [ 55 ] . Antibiotics including rifaximin that are effective in prevention of recurrence of HE in cirrhotic patients [ 56 ] are also known to reduce circulating levels of proin fl ammatory cytokines [ 12 ] . In a study of cirrhotic patients with MHE treated with synbiotics for 30 days, increased fecal content of non-urease producing species and concomitant reductions in circulating levels of both ammonia and endotoxin were observed along with reversal of MHE in 50% of patients compared to 13% in the control arm of the trial [ 57 ] . Another example of an existing therapy that acts by reduction of in fl ammation is mild hypothermia which is increasingly being used in the management of the CNS complications of ALF [ 58, 59 ] . Mechanisms implicated in the mediation of the bene fi cial effects of hypothermia in ALF involve anti-in fl ammatory mechanisms at both the hepatic and cerebral levels (see below).

The discovery of neuroin fl ammation and central neuroin fl ammatory mechanisms in liver failure will undoubtedly provide new therapeutic targets. Already, studies in experimental animal models of ALF or chronic liver failure have assessed the bene fi cial effects of known anti-in fl ammatory agents in relation to the cerebral complications of liver failure. Signi fi cant improvement of locomotor impairment following administration of indomethacin in portal vein-ligated rats was accompanied by prevention of a rise in IL-6 mRNA [ 23 ] . Ibuprofen was also reported to improve learning ability [ 22 ] and locomotor de fi cits [ 51 ] in portacaval-shunted rats but, in this case, the protective effect was independent of action on increased brain cytokine levels. Ibuprofen has also been shown to signi fi cantly reduce neuroin fl ammation in bile duct-ligated rats where it was found to inhibit microglial activation and restore cognitive and motor function in these animals [ 10 ] . However, in this latter study, ibuprofen was also found to normalize circulating and brain ammonia levels, suggesting that effects on systemic in fl ammation and improvement of hepatic func-tion may also have contributed to the bene fi cial effects of ibuprofen. The disparate fi ndings of the effects of anti-in fl ammatory drugs in different experimental models of liver failure likely re fl ect differences in the degree of systemic vs. neuroin fl ammation in these models.

Therapies directly targeting neuroin fl ammatory processes include those aimed at inhibition of microglial activation or inhibition of the actions of proin fl ammatory cytokines. One such example is mild hypothermia. Just two degrees of hypothermia have been shown to delay the onset of HE, prevent brain edema, and impair both microglial activation and the increased expression of genes coding for proin fl ammatory cytokines [ 6 ] . A more recent study showed that deletion (knock-down) of the gene coding for TNF- a or IL-1 b likewise delays HE onset and attenu-ates brain edema in mice with ALF resulting from toxic liver injury [ 7 ] . Preliminary studies demonstrate that treatment with the TNF- a receptor antagonist etanercept likewise led to slowing in progression of HE and prevention of brain edema in experimental ALF [ 31 ] .


An interesting new dimension in the search for novel anti-in fl ammatory agents for potential application in the treatment of the CNS complications of liver failure was recently provided by the report that minocycline, an agent with well-established potent inhibitory properties on microglial activation that are independent of its antimicrobial properties [ 60 ] , inhibits proin fl ammatory cytokine production in brain, delays progression of HE, and attenuates brain edema in experimental ALF [ 44 ] (Fig. 3.6 ).

Translation of these interesting leads to the clinic has the potential to provide novel, targeted strategies for the management and treatment of the CNS complications of acute and chronic liver failure in the near future.

References

1. Kato M, Hughes RD, Keays RT, Williams R. Electron microscopic study of brain capillaries in cerebral edema from fulminant hepatic failure. Hepatology. 1992;15:1060–6.

2. Cordoba J, Blei AT. Brain edema and hepatic encephalopathy. Semin Liver Dis. 1996;16:271–80. 3. Kril JJ, Butterworth RF. Diencephalic and cerebellar pathology in alcoholic and nonalcoholic

patients with end-stage liver disease. Hepatology. 1997;26(4):837–41. 4. Butterworth RF. Thiamine de fi ciency-related brain dysfunction in chronic liver failure. Metab

Brain Dis. 2009;24(1):189–96.

Fig. 3.6 Increased expression of OX-6 indicative of microglial activation in the brains of rats with ALF due to hepatic devascularization at coma/edema stage of encephalopathy (ALF coma). Treatment with minocycline resulted in delayed progression of HE, prevention of brain edema, and attenuation of the increase of OX-6 expression (ALF mino) (reprinted by permission from Macmillan Publishers Ltd: Jiang et al. [ 6 ] © 2009)

32 R.F. Butterworth

5. Jiang W, Qu H, Desjardins P, Chatauret N, Bélanger M, Butterworth RF. Bene fi cial effects of mild hypothermia on the expression of pro-in fl ammatory cytokines in rats with acute liver failure. Hepatology. 2005;42(4 Suppl 1):361A.

6. Jiang W, Desjardins P, Butterworth RF. Direct evidence for central proin fl ammatory mecha-nisms in rats with experimental acute liver failure: protective effect of hypothermia. J Cereb Blood Flow Metab. 2009;29:944–52.

7. Bémeur C, Qu H, Desjardins P, Butterworth RF. IL-1 or TNF receptor gene deletion delays onset of encephalopathy and attenuates brain edema in experimental acute liver failure. Neurochem Int. 2010;56:213–5.

8. Butterworth RF. Hepatic encephalopathy: a central neuroin fl ammatory disorder? Hepatology. 2011;53(4):1372–6.

9. D’Mello C, Le T, Swain MG. Cerebral microglia recruit monocytes into the brain in response to tumor necrosis factoralpha signaling during peripheral organ in fl ammation. J Neurosci. 2009;29:2089–102.

10. Rodrigo R, Cauli O, Gomez-Pinedo U, Agusti A, Hernandez-Rabaza V, Garcia-Verdugo JM, et al. Hyperammonemia induces neuroin fl ammation that contributes to cognitive impairment in rats with hepatic encephalopathy. Gastroenterology. 2010;139:675–84.

11. Rolando N, Wade J, Davalos M, Wendon J, Philpott-Howard J, Williams R. The systemic in fl ammatory response syndrome in acute liver failure. Hepatology. 2000;32:734–9.

12. Odeh M. Pathogenesis of hepatic encephalopathy: the tumour necrosis factor-alpha theory. Eur J Clin Invest. 2007;37:291–304.

13. Bernal W, Donaldson P, Underhill J, Wendon J, Williams R. Tumor necrosis factor genomic polymorphism and outcome of acetaminophen (paracetamol)-induced acute liver failure. J Hepatol. 1998;29(1):53–9.

14. Chu CJ, Chen CT, Wang SS, Lee FY, Chang FY, Lin HC, et al. Hepatic encephalopathy in rats with thioacetamide-induced fulminant hepatic failure: role of endotoxin and tumor necrosis factor-alpha. Zhonghua Yi Xue Za Zhi (Taipei). 2001;64(6):321–30.

15. Bémeur C, Qu H, Desjardins P, Butterworth RF. Contribution of cerebral proin fl ammatory cytokines to hepatic encephalopathy in experimental acute liver failure: effect of interleukin-1beta receptor and tumor necrosis factor-alpha receptor knockouts. Hepatology. 2008;48(4 Suppl):348A.

16. Wright G, Shawcross D, Olde Damink SW, Jalan R. Brain cytokine fl ux in acute liver failure and its relationship with intracranial hypertension. Metab Brain Dis. 2007;22:375–88.

17. Shawcross DL, Shabbir SS, Taylor NJ, Hughes RD. Ammonia and the neutrophil in the patho-genesis of hepatic encephalopathy in cirrhosis. Hepatology. 2010;51:1062–9.

18. Shawcross DL, Davies NA, Williams R, Jalan R. Systemic in fl ammatory response exacerbates the neuropsychological effects of induced hyperammonemia in cirrhosis. J Hepatol. 2004;40:247–54.

19. Morita H, Hosoya M, Kato A, Kawasaki Y, Suzuki H. Laboratory characteristics of acute encephalopathy with multiple organ dysfunctions. Brain Dev. 2005;27:477–82.

20. Shawcross DL, Wright G, Olde Damink SW, Jalan R. Role of ammonia and in fl ammation in minimal hepatic encephalopathy. Metab Brain Dis. 2007;22:125–38.

21. Shawcross DL, Shari fi Y, Canavan JB, Yeoman AD, Abeles RD, Taylor NJ, et al. Infection and systemic in fl ammation, not ammonia, are associated with Grade 3/4 hepatic encephalopathy, but not mortality in cirrhosis. J Hepatol. 2011;54(4):640–9. doi: 10.1016/j.jhep. 2010.07.045 .

22. Cauli O, Rodrigo R, Piedra fi ta B, Boix J, Felipo V. In fl ammation and hepatic encephalopathy: ibuprofen restores learning ability in rats with portacaval shunts. Hepatology. 2007;46:514–9.

23. Brück J, Görg B, Bidmon HJ, Zemtsova I, Qvartskhava N, Keitel V, et al. Locomotor impair-ment and cerebrocortical oxidative stress in portal vein ligated rats in vivo. J Hepatol. 2011;54(2):251–7. doi: 10.1016/j.jhep. 2010.06.035 .

24. Jover R, Rodrigo R, Felipo V, Insausti R, Sáez-Valero J, García-Ayllón MS, et al. Brain edema and in fl ammatory activation in bile duct ligated rats with diet-induced hyperammonemia: a model of hepatic encephalopathy in cirrhosis. Hepatology. 2006;43(6):1257–66.

http://dx.doi.org/10.1016/j.jhep. 2010.07.045

http://dx.doi.org/10.1016/j.jhep. 2010.06.035


25. Atanassov CL, Muller CD, Dumont S, Rebel G, Poindron P, Seiler N. Effect of ammonia on endocytosis and cytokine production by immortalized human microglia and astroglia cells. Neurochem Int. 1995;27(4–5):417–24.

26. Andersson AK, Rönnbäck L, Hansson E. Lactate induces tumour necrosis factor-alpha, interleukin-6 and interleukin-1beta release in microglial- and astroglial-enriched primary cultures. J Neurochem. 2005;93:1327–33.

27. Knecht K, Michalak A, Rose C, Rothstein JD, Butterworth RF. Decreased glutamate transporter (GLT-1) expression in frontal cortex of rats with acute liver failure. Neurosci Lett. 1997;229(3):201–3.

28. Jiang W, Desjardins P, Butterworth RF. Molecular basis of synergism between brain ammonia and proin fl ammatory mechanisms in acute liver failure. Hepatology. 2009;50(4 Suppl):430A.

29. Norenberg MD, Baker L, Norenberg LO, Blicharska J, Bruce-Gregorios JH, Neary JT. Ammonia-induced astrocyte swelling in primary culture. Neurochem Res. 1991;16:833–6.

30. Hu S, Sheng WS, Ehrlich LC, Peterson PK, Chao CC. Cytokine effects on glutamate uptake by human astrocytes. Neuroimmunomodulation. 2000;7:153–9.

31. Chastre A, Grimm A, Bémeur C, Desjardins P, Butterworth RF. Bene fi cial effect of soluble TNF receptor (Etanercept) on neurological complications of acute liver failure resulting from toxic liver injury in mice. Hepatology. 2010;52:1086A.

32. van Rossum D, Hanisch UK. Microglia. Metab Brain Dis. 2004;19:393–411. 33. Chatauret N, Zwingmann C, Rose C, Leibfritz D, Butterworth RF. Effects of hypothermia on

brain glucose metabolism in acute liver failure: a H/C-nuclear magnetic resonance study. Gastroenterology. 2003;125(3):815–24.

34. Therrien G, Giguère JF, Butterworth RF. Increased cerebrospinal fl uid lactate re fl ects deterioration of neurological status in experimental portal-systemic encephalopathy. Metab Brain Dis. 1991;4:225–31.

35. Lai JC, Cooper AJ. Brain alpha-ketoglutarate dehydrogenase complex: kinetic properties, regional distribution, and effects of inhibitors. J Neurochem. 1986;47:1376–86.

36. Chatauret N, Rose C, Therrien G, Pannunzio M, Butterworth RF. Mild hypothermia prevents cerebral edema and CSF lactate accumulation in acute liver failure. Metab Brain Dis. 2001;16:95–102.

37. Filipov NM, Seegal RF, Lawrence DA. Manganese potentiates in vitro production of proin fl ammatory cytokines and nitric oxide by microglia through a nuclear factor kappa B-dependent mechanism. Toxicol Sci. 2005;84:139–48.

38. Pomier Layrargues G, Spahr L, Butterworth RF. Increased manganese concentrations in pallidum of cirrhotic patients: cause of magnetic resonance hyperintensity? Lancet. 1995;345:735.

39. Lavoie J, Pomier Layrargues G, Butterworth RF. Increased densities of “peripheral-type” benzodiazepine receptors in autopsied brain tissue from cirrhotic patients with hepatic enceph-alopathy. Hepatology. 1990;11:874–8.

40. Cagnin A, Taylor-Robinson SD, Forton DM, Banati RB. In vivo imaging of cerebral “peripheral benzodiazepine binding sites” in patients with hepatic encephalopathy. Gut. 2006;55:547–53.

41. Bélanger M, Ahboucha S, Desjardins P, Butterworth RF. Upregulation of peripheral-type (mitochondrial) benzodiazepine receptors in hyperammonemic syndromes: consequences for neuronal excitability. Adv Mol Cell Biol. 2004;31(3):983–97.

42. Giguère JF, Hamel E, Butterworth RF. Increased densities of binding sites for the “peripheral-type” benzodiazepine receptor ligand 3H-PK 11195 in rat brain following portacaval anastomosis. Brain Res. 1992;585:295–8.

43. Desjardins P, Bandeira P, Raghavendra Rao VL, Ledoux S, Butterworth RF. Increased expression of the peripheral-type benzodiazepine receptor-isoquinoline carboxamide binding protein in mRNA brain following portacaval anastomosis. Brain Res. 1997;758:255–8.

44. Jiang W, Desjardins P, Butterworth RF. Cerebral in fl ammation contributes to encephalopathy and brain edema in acute liver failure: protective effect of minocycline. J Neurochem. 2009;109:485–93.

34 R.F. Butterworth

45. Bélanger M, Desjardins P, Chatauret N, Butterworth RF. Loss of expression of glial fi brillary acidic protein in acute hyperammonemia. Neurochem Int. 2002;41(2–3):155–60.

46. Kril JJ, Flowers D, Butterworth RF. Distinctive pattern of Bergmann glial pathology in human hepatic encephalopathy. Mol Chem Neuropathol. 1997;31(3):279–87.

47. Butterworth RF, Giguère JF, Michaud J, Lavoie J, Pomier Layrargues G. Ammonia: key factor in the pathogenesis of hepatic encephalopathy. Neurochem Pathol. 1987;6:1–12.

48. Doorduin J, de Vries EF, Dierckx RA, Klein HC. PET imaging of the peripheral benzodiaz-epine receptor: monitoring disease progression and therapy response in neurodegenerative disorders. Curr Pharm Des. 2008;14(31):3297–315.

49. Ahboucha S, Pomier-Layrargues G, Mamer O, Butterworth RF. Increased brain concentrations of a neuroinhibitory steroid in human hepatic encephalopathy. Ann Neurol. 2005;58(1):169–70.

50. Ahboucha S, Jiang W, Chatauret N, Mamer O, Baker GB, Butterworth RF. Indomethacin improves locomotor de fi cit and reduces brain concentrations of neuroinhibitory steroids in rats following portacaval anastomosis. Neurogastroenterol Motil. 2008;20:949–57.

51. Cauli O, Rodrigo R, Piedra fi ta B, Llansola M, Mansouri MT, Felipo V. Neuroin fl ammation contributes to hypokinesia in rats with hepatic encephalopathy: ibuprofen restores its motor activity. J Neurosci Res. 2009;87:1369–74.

52. Norenberg MD. Astroglial dysfunction in hepatic encephalopathy. Metab Brain Dis. 1998;13(4):319–35.

53. Hazell AS. Astrocytes and manganese neurotoxicity. Neurochem Int. 2002;41(4):271–7. 54. Oh YJ, Francis JW, Markelonis GJ, Oh TH. Interleukin-1-beta and tumor necrosis factor-alpha

increase peripheral-type benzodiazepine binding sites in cultured polygonal astrocytes. J Neurochem. 1992;58(6):2131–8.

55. Guo LM, Liu JY, Xu DZ, Li BS, Han H, Wang LH, et al. Application of molecular adsorbents recirculating system to remove NO and cytokines in severe liver failure patients with multiple organ dysfunction syndrome. Liver Int. 2003;23 Suppl 3:16–20.

56. Bass NM, Mullen KD, Sanyal A, Poordad F, Neff G, Leevy CB, et al. Rifaximin treatment in hepatic encephalopathy. N Engl J Med. 2010;362(12):1071–81.

57. Liu Q, Duan ZP, Ha DK, Bengmark S, Kurtovic J, Riordan SM. Synbiotic modulation of gut fl ora: effect on minimal hepatic encephalopathy in patients with cirrhosis. Hepatology. 2004;39(5):1441–9.

58. Jalan R, Olde Damink SW, Deutz NE, Davies NA, Garden OJ, Madhavan KK, et al. Moderate hypothermia prevents cerebral hyperemia and increase in intracranial pressure in patients undergoing liver transplantation for acute liver failure. Transplantation. 2003;75:2034–9.

59. Vaquero J, Butterworth RF. Mild hypothermia for the treatment of acute liver failure—what are we waiting for? Nat Clin Pract Gastroenterol Hepatol. 2007;4:528–9.

60. Henry CJ, Huang Y, Wynne A, Hanke M, Himler J, Bailey MT, et al. Minocycline attenuates lipopolysaccharide (LPS)-induced neuroin fl ammation, sickness behavior, and anhedonia. J Neuroin fl ammation. 2008;5:15.


Keywords In fl ammation • Infection • Hepatic encephalopathy • Ammonia • Oxidative stress • Neutrophils

Introduction

Following the seminal studies on portacaval shunted dogs by Nencki, Pavlov and Zaleski in the 1890s, it is widely agreed that ammonia plays an important role in the pathogenesis of hepatic encephalopathy (HE) [ 1 ] . In acute liver failure, arterial ammonia concentrations of >150 m mol/L predict a greater likelihood of dying from brain herniation [ 2 ] , and intracranial hypertension develops in 55% of patients with an arterial ammonia concentration of >200 m mol/L [ 3 ] . However in patients with cirrhosis, the relationship is less clear cut. There is con fl icting evidence regarding the relationship between blood ammonia concentration and the development of covert (minimal) and overt HE. Clinically, it is not unusual to fi nd patients with cirrhosis presenting with overt HE with normal or only mildly elevated blood ammonia concentrations [ 4, 5 ] . Indeed, studies have shown single blood ammonia

Chapter 4 In fl ammation and Hepatic Encephalopathy

Shabnam S. Shabbir , Amit Singh Seyan , and Debbie Lindsay Shawcross

S. S. Shabbir, BSc, MBBS • A.S. Seyan, MBBS, BSc (Hons) King’s College School of Medicine, King’s College London, London , UK

D. L. Shawcross, BSc, MBBS, FRCP, PhD (*) Institute of Liver Studies , King’s College School of Medicine at King’s College Hospital , Denmark Hill , London SE5 9RS , UK e-mail: [email protected]

The authors Shabnam S. Shabbir and Amit Singh Seyan contributed equally to this chapter.

36 S.S. Shabbir et al.

concentrations to correlate unreliably with the severity of HE [ 6 ] . It is therefore reasonable to postulate a key role for other factors in the pathogenesis of HE. The idea that the pathogenesis of HE might involve synergism between several toxins was fi rst suggested by Zieve et al. [ 7 ] , and this hypothesis has since evolved to include the complex role of in fl ammation and oxidative stress in the presence and absence of infection.

Infection Versus In fl ammation in Acute and Chronic Liver Failure

In both acute and chronic liver failure, patients are functionally immunosuppressed because of a signi fi cant reduction in liver synthetic function and impairment of host defence mechanisms. This makes them highly susceptible to developing infections, which can complicate their clinical course leading to the development of organ failure and death [ 8, 9 ] . Rolando et al. have demonstrated evidence of infection in up to 90% of patients early in the course of acute liver failure [ 10 ] . Other indicators of the presence of in fl ammation and infection in acute liver failure come from studies demonstrating raised proin fl ammatory cytokines, including TNF- a , IL-1 b and IL-6 which have been associated with poorer outcomes and the development of cerebral edema and intracranial hypertension [ 11, 12 ] .

In patients with cirrhosis, the increased susceptibility to infection is thought to be multifactorial. One important contributing factor is neutrophil dysfunction. Neutrophils play a key role in the early innate immune response of the body by engul fi ng foreign microbes and debris by a process known as phagocytosis. They then eliminate the engulfed foreign bodies through the generation of an “oxidative burst”, whereby reactive oxygen species are released into the phagosomes. These reactive oxygen species not only kill invading micro-organisms but may also cause damage to nearby tissues causing local in fl ammation, tissue destruction and organ failure. Neutrophil dysfunction is prevalent in patients with cirrhosis [ 13 ] , particu-larly where alcohol is implicated in the aetiology [ 14, 15 ] and is associated with a signi fi cantly greater risk of infection, organ failure and mortality.

The terms in fl ammation and infection are frequently used interchangeably. Although functionally related, they should be treated as separate entities. The sys-temic in fl ammatory response syndrome (SIRS) results from the release into the cir-culation of proin fl ammatory mediators and cytokines that can arise directly from hepatocyte injury, e.g. acetaminophen hepatotoxicity, or can arise peripherally from the production of reactive oxygen species and concomitant tissue injury, e.g. isch-emia or burns. Alternatively, this will occur as sequelae from local or systemic infection. Frequently, it is impossible to delineate these phenomena in patients with liver failure, especially those with cirrhosis who may have low grade endotoxemia resulting from bacterial translocation across the gut into the portal circulation [ 16 ] .

374 Infl ammation and Hepatic Encephalopathy

This population is prone to developing infection which is dif fi cult to con fi rm with microbial cultures which have a low yield.

In fl ammation results from the activation of circulating immune cells, interaction with the endothelium and multiple mediator cascades balanced by an anti-in fl ammatory system which include the cytokines IL-4, IL-10 and IL-13. Following injury, proin fl ammatory mediators are released locally to combat foreign antigens and promote wound healing. This is balanced by the release of anti-in fl ammatory mediators which downregulate and prevent excess in fl ammation (compensatory anti-in fl ammatory response—CARS). If the in fl ammatory response is not con-trolled, the proin fl ammatory mediators enter the systemic circulation leading to neutrophil recruitment and activation. When homeostasis is disturbed resulting in an exaggerated SIRS or CARS, then “immunological dissonance” occurs which can lead to cellular immune depression, multiorgan dysfunction and death [ 17 ] . This is frequently seen in those with acute or chronic liver failure, particularly in the con-text of severe sepsis. The extent of in fl ammation is also dependent on the aetiology of the liver injury, e.g. alcoholic hepatitis, and the severity of the underlying liver disease. Infection is a frequent precipitant of HE and it is not unusual for changes in mental state to be the sole manifestation of infection in this cirrhotic cohort.

Infection and the Blood–Brain Barrier

In the absence of liver disease, it is widely accepted that sepsis can cause agitation and delirium. This can progress to a condition known as sepsis-associated enceph-alopathy, which encompasses a range of changes in motor activity and mental status, ranging from delirium to coma. Asterixis, paratonic rigidity, tremor and myoclonus may even be observed. It is thought that these changes occur due to a reduction in cerebral blood fl ow, changes in brain metabolites and amino acids, and disruption to the blood–brain barrier resulting from the direct effect of in fl ammatory cytokines on the endothelium of the blood–brain barrier [ 18 ] . Although sepsis-associated encephalopathy is distinctly different to HE from a pathophysiological standpoint, it is not inconceivable that infection may induce changes in mental status in patients both with and without liver disease.

In fl ammatory mediators are able to signal the brain through activation of afferent neurons of the vagus nerve, interaction of cytokines with circumventricular organs or via the direct effect of active transport across the blood–brain barrier [ 19 ] . Furthermore, endothelial cells and astrocytes, integral parts of the blood–brain barrier, can be stimulated to release a full repertoire of immune mediators into the brain activating neurons and microglial cells. Endothelial cells have receptors for IL-1 b and TNF- a , which can alter the integrity of the blood–brain barrier and activate signalling pathways leading to the intracerebral synthesis of nitric oxide and prostanoids [ 20 ] .


Infection and In fl ammation Modulate Hepatic Encephalopathy

Over the past decade there has been a growing evidence base implicating infection as being important in the manifestation of HE in acute and chronic liver failure. It was fi rst shown by Nancy Rolando at King’s that patients with acute liver failure progress more quickly to severe HE if they have signs of systemic in fl ammation [ 21 ] , and in a study by the US Liver Failure Group, in patients with acute liver fail-ure induced by acetaminophen, the consequent systemic in fl ammatory response was a signi fi cant contributor to the severity of HE [ 22 ] . Liver-derived proin fl ammatory cytokines are important in driving cerebral edema and intracranial hypertension in acute liver failure [ 11 ] . Furthermore, the brain itself produces a number of proin fl ammatory cytokines in patients with acute liver failure and advanced cere-bral edema [ 12 ] . When interventions such as hypothermia are utilised, a reduction in intracranial hypertension can be seen resulting from a reduction in cerebral blood fl ow, brain ammonia uptake, oxidative stress and systemic in fl ammation [ 23, 24 ] .

In patients with cirrhosis, the role of systemic in fl ammation in exacerbating HE has also become evident. Studies have shown that those patients with minimal HE have elevated plasma levels of in fl ammatory markers, and the severity of the HE is not indicative of the liver disease severity nor of plasma ammonia levels [ 25 ] . The synergistic effect of in fl ammation and ammonia has been demonstrated in a cir-rhotic population admitted with infection and given an amino acid load to temporar-ily and reversibly induce hyperammonemia. Patients had deterioration in neuropsychological tests scores during infection but not after its resolution, provid-ing evidence in support of infection modulating the effects of ammonia on the brain [ 26 ] . In a large study of patients with cirrhosis from King’s College Hospital admit-ted to intensive care with the primary indication of severe HE (grades 3 and 4), almost 50% of patients were found to have culture-positive infection and a further 22% had sterile SIRS. Arterial ammonia concentration and blood biochemistry were found not to correlate with the severity of HE supporting the theory that infec-tion and in fl ammation, not hyperammonemia, have the more pivotal role in increas-ing the severity of HE [ 5 ] .

Infection and In fl ammation Act Synergistically with Ammonia

The notion of the existence of a synergistic relationship between in fl ammation, infection and ammonia has been examined in several studies. A mouse model with chronic hyperammonemia was shown not only to have an increased sensitivity to in fl ammation but signi fi cant cognitive defects when exposed to an in fl ammatory stimulus [ 27 ] . Jover et al. used a rat model to demonstrate neurological changes following bile duct ligation and were fed a hyperammonemic diet. These rats had increased levels of cerebral ammonia and type II Alzheimer astrocytosis, similar to that seen in patients with HE and cirrhosis. These rats also had signs of systemic


in fl ammation and low grade brain edema. All these changes contributed to impaired motor activity on co-ordination tests [ 28 ] . Wright et al. in another bile duct-ligated rat model were able to show that lipopolysaccharide administration increased brain water in ammonia-fed, bile duct-ligated and sham-operated animals signi fi cantly, but this was associated with progression to pre-coma only in the bile duct-ligated animals. Lipopolysaccharide induced cytotoxic brain edema but the blood–brain barrier remained intact. Nitrosation of brain proteins was seen in the lipopolysac-charide-treated, bile duct-ligated animals only suggesting subliminal in fl ammation may be a pre-requisite to the development of HE [ 29 ] . In a portacaval-shunted rat model mimicking minimal HE, Cauli et al. showed that administrating a high dose of ibuprofen, a non-steroidal anti-in fl ammatory, resulted in improved ability to learn. This was thought to occur through normalisation of the glutamate–nitric oxide–cyclic GMP pathway in the cerebral cortex, and so supports the fact that in fl ammation is pivotal to the development of cognitive impairment in HE [ 30 ] . The non-selective cyclo-oxygenase (COX) inhibitor indomethacin has been demon-strated to be effective in reducing intracranial hypertension in patients with acute liver failure [ 31, 32 ] and in a portacaval-shunted rat model [ 33 ] .

Immune Dysfunction and Oxidative Stress in Hepatic Encephalopathy

Systemic immune dysfunction in acute and chronic liver failure and the resultant oxidative stress response play an irrefutable role in the development of HE particu-larly in the context of elevated blood ammonia concentrations [ 34 ] . In a proof of concept study, ammonia was shown to lead to signi fi cant neutrophil malfunction. This led to a reduced capacity to engulf opsonised Escherichia coli and high spon-taneous oxidative burst. These observations were replicated in ammonia-fed rats and ex vivo in patients with cirrhosis given a simulated upper gastrointestinal bleed inducing hyperammonemia compared to controls [ 35 ] . The mechanism underlying this neutrophil malfunction was shown to be related to the development of ammonia-induced cell swelling resulting from an inability of a key osmoregulator p38 −MAPK to regulate neutrophil volume. This has interestingly also been replicated in hepato-cytes [ 36 ] and astrocytes [ 37 ] .

Small bowel overgrowth and increased bacterial translocation from the gut due to breakdown in mucosal barrier function can result in bacterial burden being deliv-ered to the liver via the portal vein. The presence of porto-systemic shunting results in the bypassing of the reticuloendothelial system and delivery of low-grade endotoxin to the systemic circulation. Bacteria and bacterial by-products such as endotoxin can activate various immune cells, either directly through pattern-recognition recep-tors such as Toll-like receptors (TLRs) or through the generation of proin fl ammatory and anti-in fl ammatory cytokines. Priming of circulating neutrophils through such mechanisms can lead to changes in surface receptors, conformational changes in


binding ligands and increased metabolic demand. This ultimately leads to alterations in phagocytic capacity and bacteriocidal function [ 14, 38 ] . Thus, in a patient with cirrhosis, hyperammonemia and chronic endotoxemia pre-primed neutrophils may enhance endothelial–neutrophil interaction within the cerebral microcirculation (Fig. 4.1 ). The cerebral effects of ammonia will therefore potentially have their greatest impact in this in fl ammatory milieu. This may be exacerbated by astrocytes producing chemokines that may attract and recruit neutrophils and other immune cells [ 39 ] .

Targeting In fl ammation in the Treatment of Hepatic Encephalopathy

In patients with acute liver failure, the main therapeutic goal along with liver trans-plantation is to lower arterial ammonia. Hemo fi ltration of the blood is highly ef fi cacious in removing ammonia and is now a standard of care [ 40 ] . However in

Fig. 4.1 Pictorial representation of the interface between the systemic in fl ammatory response and the blood–brain barrier in acute and chronic liver failure. A “cytotoxic soup” of ammonia (NH

3 ),

lipopolysaccharide (LPS), chemokines and cytokines and bacteria or bacterial peptides can lead to endothelial interaction, neutrophil activation and degranulation at the blood–brain barrier. Granules (containing substances such as myeloperoxidase) and chemokines can induce astrocyte and micro-glial activation and neuronal dysfunction. In patients with overt sepsis resulting in an overlap between hepatic encephalopathy and sepsis-related encephalopathy, neutrophils and monocytes may even be able to directly pass across the blood–brain barrier


patients with cirrhosis, treatments that focus on lowering arterial ammonia and modulating interorgan ammonia metabolism are less effective. The main therapeu-tic target will depend on the nature of the HE but reversing any precipitating factor should always be considered as a priority; infection being the most common precipi-tant particularly in those presenting with the severest grades of HE [ 5 ] .

The use of absorbable and non-absorbable antibiotics has become well estab-lished in the treatment of HE in patients with cirrhosis [ 41 ] . However, some antibi-otics, such as neomycin, vancomycin and metronidazole that have been used to effectively reduce the production of ammonia by gut bacterial fl ora, have nephro-toxic and ototoxic effects as well as the potential to cause a peripheral neuropathy. Rifaximin is a minimally absorbed antibiotic, with broad spectrum activity and is concentrated in the gastrointestinal tract. Bass et al. performed a randomised, dou-ble-blind, placebo-controlled trial enrolling 299 patients with cirrhosis who were currently in remission from HE. Rifaximin was signi fi cant in reducing the risk of developing an episode of HE when compared to a placebo, over a period of 6 months; not only did rifaximin maintain remission from HE, but also reduced the risk of hospitalisation [ 42 ] . Bajaj et al. assessed whether patients with minimal HE had an improved driving performance after treatment with rifaximin. Patients were either assigned to placebo or rifaximin for 8 weeks, undertaking driving simulation at the beginning and end of the 8-week study period. Patients taking rifaximin had fewer total driving errors than the placebo group. Ninety one per cent of patients on rifaximin improved their cognitive performance compared to 61% of patients on placebo. Patients taking rifaximin had an improved sickness impact pro fi le and increased interleukin-10 levels suggesting that rifaximin may be more than a modu-lator of gut fl ora but may lead to reduced bacterial translocation across the gut and systemic in fl ammation [ 43 ] .

As the role of infection and in fl ammation in mediating HE has become estab-lished, therapies that target in fl ammation and modulate the immune system have been of interest to hepatologists. However in doing this, one must also remember that augmenting immune function can lead to damage of normal healthy tissue and organs. The use of granulocyte colony-stimulating factor [ 44 ] , leucodepletion, [ 45 ] antagonism of proin fl ammatory cytokines or their receptors, anti-in fl ammatory (COX inhibitors) [ 31 ] , antioxidants ( N -acetylcysteine [ 46 ] and albumin), probiotics [ 47 ] and hypothermia [ 23 ] all hold potential. Inducing a hypothermic state has the bene fi t of decreasing brain ammonia, cerebral blood fl ow as well as in fl ammatory mediators and oxidative stress, particularly in those with the severest grades of HE [ 23 ] . Moderate hypothermia abolishes ammonia-induced neutrophil spontaneous oxidative burst without impairing phagocytic capacity, suggesting that hypothermia could be a valuable tool not only in patients with acute liver failure, but also those with cirrhosis and grade 3/4 HE [ 48 ] .

Patients with end-stage cirrhosis have alterations in the functional capacity of albumin which can act as an endotoxin scavenger and may explain the bene fi cial effects of albumin infusion and dialysis on HE [ 49 ] .

Jiang et al. showed that treatment with the antibiotic minocycline in rats with acute liver failure prevented central microglial activation and upregulation of many


proin fl ammatory mediators including IL-1 b , IL-6, TNF- a , haeme-oxygenase-1, eNOS, iNOS mRNA and protein expression, slowing progression of HE, in part due to a reduction in nitrosative and oxidative stress [ 50 ] . This supports minocycline as being a promising new candidate drug in HE and being taken forward into a ran-domised, placebo-controlled trial in patients with acute and acute-on-chronic liver failure and severe HE.

The use of TLR-2, TLR-4 and TLR-9 inhibitors and molecules involved in TLR-4 signalling could downregulate overactive neutrophil responses. Another therapeutic option could be to modulate the microbiota of the intestine, in turn pre-venting bacterial translocation of lipopolysaccharide and bacteria that activate TLRs. Probiotics have been shown to improve liver function, reduce infection and the development of minimal HE in cirrhosis [ 47 ] . Patients with alcohol-related cirrhosis given probiotics had improved neutrophil phagocytic activity possibly resulting from reduced interleukin-10 and TLR-4 expression [ 51 ] .

Summary

This chapter has highlighted the fundamental role that infection and in fl ammation plays in the development of HE in acute and chronic liver failure. No longer can ammonia be thought of as the sole perpetrator of HE but instead there is a synergistic relationship between in fl ammation in modulating the cerebral effects of ammonia. It has been shown that astrocytes and endothelial cells at the blood–brain barrier respond to a systemic in fl ammatory stimulus and play a role in eliciting an in fl ammatory response which incorporates a number of close knit proin fl ammatory and neurotransmitter pathways.

Ammonia is not only directly toxic to astrocytes but induces immune dysfunc-tion leading to the release of reactive oxygen species which contributes to systemic in fl ammation and an increased vulnerability to fi ghting microbial invasion. Increased neutrophil and endothelial cell interaction at the blood–brain barrier may even play a direct pathogenic role analogous to that seen in sepsis-related encephalopathy.

In addition to direct ammonia-lowering strategies, targeting systemic in fl ammation and infection is therefore key in developing effective treatments for HE. Furthermore, the neutrophil and other components of the innate and adaptive immune systems should be considered as legitimate novel pharmacotherapeutic targets for drug development in the future.

References

1. Nencki M, Pawlow J, Zaleski J. Ueber den ammoniakgehalt des blutes under der organe und die harnstoffbildung bei den saugethieren. Arch Exp Pathol Pharmakol. 1896;37:26–51.

2. Clemmesen J, Larsen F, Kondrup J, Hansen B, Ott P. Cerebral herniation in patients with acute liver failure is correlated with arterial ammonia concentration. Hepatology. 1999;29:648–53.


3. Bernal W, Hall C, Karvellas C, Auzinger G, Sizer E, Wendon J. Arterial ammonia and clinical risk factors for encephalopathy and intracranial hypertension in acute liver failure. Hepatology. 2007;46(6):1844–52.

4. Ong JP, Aggarwal A, Krieger D, Easley KA, Karafa MT, Van Lente F, et al. Correlation between ammonia levels and the severity of hepatic encephalopathy. Am J Med. 2003; 114(3): 188–93.

5. Shawcross D, Shari fi Y, Canavan J, Yeoman A, Abeles R, Taylor N, et al. Infection and sys-temic in fl ammation, not ammonia, are associated with grade III/IV hepatic encephalopathy, but not mortality in cirrhosis. J Hepatol. 2011;54(4):640–9.

6. Arora S, Martin CL, Herbert M. Myth: interpretation of a single ammonia level in patients with chronic liver disease can con fi rm or rule out hepatic encephalopathy. CJEM. 2006;8(6):433–5.

7. Zieve FJ, Zieve L, Doizaki WM, Gilsdorf RB. Synergism between ammonia and fatty acids in the production of coma: implications for hepatic coma. J Pharmacol Exp Ther. 1974;191(1):10–6.

8. Wasmuth H, Kunz D, Yagmur E, Timmer-Stranghoner A, Vidacek D, Siewart E, et al. Patients with acute on chronic liver failure display ‘sepsis-like’ immune paralysis. J Hepatol. 2005;42:195–201.

9. Antoniades C, Berry P, Wendon J, Vergani D. The importance of immune dysfunction in deter-mining outcome in acute liver failure. J Hepatol. 2008;49:845–61.

10. Rolando N, Harvey F, Brahm J, Philpott-Howard J, Alexander G, Gimson A, et al. Prospective study of bacterial infection in acute liver failure: an analysis of fi fty patients. Hepatology. 1990;11(1):49–53.

11. Jalan R, Pollok A, Shah SH, Madhavan K, Simpson KJ. Liver derived pro-in fl ammatory cytokines may be important in producing intracranial hypertension in acute liver failure. J Hepatol. 2002;37(4):536–8.

12. Wright G, Shawcross D, Olde Damink S, Jalan R. Brain cytokine fl ux in acute liver failure and its relationship with intracranial hypertension. Metab Brain Dis. 2007;22(3–4):375–88.

13. Rajkovic IA, Williams R. Mechanisms of abnormalities in host defences against bacterial infection in liver disease. Clin Sci (Lond). 1985;68(3):247–53.

14. Rajkovic IA, Williams R. Abnormalities of neutrophil phagocytosis, intracellular killing and metabolic activity in alcoholic cirrhosis and hepatitis. Hepatology. 1986;6(2):252–62.

15. Mookerjee R, Stadlbauer V, Lidder S, Wright G, Hodges S, Davies N, et al. Neutrophil dys-function in alcoholic hepatitis superimposed on cirrhosis is reversible and predicts outcome. Hepatology. 2007;46(3):831–40.

16. Bode C, Kugler V, Bode J. Endotoxemia in patients with alcoholic and non-alcoholic cirrhosis and in subjects with no evidence of chronic liver disease following acute alcohol excess. J Hepatol. 1987;4:8–14.

17. Bone RC. Immunologic dissonance: a continuing evolution in our understanding of the sys-temic in fl ammatory response syndrome (SIRS) and the multiple organ dysfunction syndrome (MODS). Ann Intern Med. 1996;125(8):680–7.

18. Papadopoulos MC, Davies DC, Moss RF, Tighe D, Bennett ED. Pathophysiology of septic encephalopathy: a review. Crit Care Med. 2000;28(8):3019–24.

19. Licinio J, Wong M. Pathways and mechanisms for cytokine signalling of the central nervous system. J Clin Invest. 1997;100:2941–7.

20. Didier N, Romero IA, Creminon C, Wijkhuisen A, Grassi J, Mabondzo A. Secretion of inter-leukin-1beta by astrocytes mediates endothelin-1 and tumour necrosis factor-alpha effects on human brain microvascular endothelial cell permeability. J Neurochem. 2003;86(1):246–54.

21. Rolando N, Wade J, Davalos M, Wendon J, Philpott-Howard J, Williams R. The systemic in fl ammatory response syndrome in acute liver failure. Hepatology. 2000;32:734–9.

22. Vaquero J, Polson J, Chung C, Helenowski I, Schiodt FV, Reisch J, et al. Infection and the progression of hepatic encephalopathy in acute liver failure. Gastroenterology. 2003;125(3): 755–64.

23. Jalan R, Olde Damink S, Deutz N, Lee A, Hayes P. Treatment of uncontrolled intracranial hypertension in acute liver failure with moderate hypothermia. Lancet. 1999;354:1164–8.


24. Jalan R, Olde Damink SW, Hayes PC, Deutz NE, Lee A. Pathogenesis of intracranial hypertension in acute liver failure: in fl ammation, ammonia and cerebral blood fl ow. J Hepatol. 2004;41(4):613–20.

25. Shawcross D, Wright G, Olde Damink S, Jalan R. Role of ammonia and in fl ammation in mini-mal hepatic encephalopathy. Metab Brain Dis. 2007;22:125–38.

26. Shawcross D, Davies N, Williams R, Jalan R. Systemic in fl ammatory response exacerbates the neuropsychological effects of induced hyperammonemia in cirrhosis. J Hepatol. 2004;40(2):247–54.

27. Marini JC, Broussard SR. Hyperammonemia increases sensitivity to LPS. Mol Genet Metab. 2006;88(2):131–7.

28. Jover R, Rodrigo R, Felipo V, Insausti R, Saez-Valero J, Garcia-Ayllon MS, et al. Brain edema and in fl ammatory activation in bile duct ligated rats with diet-induced hyperammonemia: a model of hepatic encephalopathy in cirrhosis. Hepatology. 2006;43(6):1257–66.

29. Wright G, Davies N, Shawcross D, Hodges S, Zwingmann C, Brooks H, et al. Endotoxemia produces coma and brain swelling in bile duct ligated rats. Hepatology. 2007;45(6):1517–26.

30. Cauli O, Rodrigo R, Piedra fi ta B, Boix J, Felipo V. In fl ammation and hepatic encephalopathy: ibuprofen restires learning ability in rats with portacaval shunts. Hepatology. 2007;46:514–9.

31. Clemmesen JO, Hansen BA, Larsen FS. Indomethacin normalizes intracranial pressure in acute liver failure: a twenty-three-year-old woman treated with indomethacin. Hepatology. 1997;26(6):1423–5.

32. Tofteng F, Larsen FS. The effect of indomethacin on intracranial pressure, cerebral perfusion and extracellular lactate and glutamate concentrations in patients with fulminant hepatic fail-ure. J Cereb Blood Flow Metab. 2004;24(7):798–804.

33. Chung C, Gottstein J, Blei AT. Indomethacin prevents the development of experimental ammo-nia-induced brain edema in rats after portacaval anastomosis. Hepatology. 2001;34(2):249–54.

34. Shawcross DL, Shabbir SS, Taylor NJ, Hughes RD. Ammonia and the neutrophil in the patho-genesis of hepatic encephalopathy in cirrhosis. Hepatology. 2010;51(3):1062–9.

35. Shawcross D, Wright G, Stadlbauer V, Hodges S, Wheeler-Jones C, Pitsillides A, et al. Ammonia impairs neutrophil phagocytic function in liver disease. Hepatology. 2008;48(4):1202–12.

36. Haussinger D, Graf D, Weiergraber O. Glutamine and cell signaling in the liver. J Nutr. 2001;131:2509S–14.

37. Jayakumar A, Panickar K, Murthy C, Norenberg M. Oxidative stress and mitogen-activated protein kinase phosphorylation mediate ammonia-induced cell swelling and glutamate uptake inhibition in cultured astrocytes. J Neurosci. 2006;26(18):4774–84.

38. Stadlbauer V, Mookerjee R, Wright G, Davies N, Jurgens G, Hallstrom S, et al. Role of toll-like receptors 2, 4 and 9 in mediating neutrophils dyfunction in alcoholic hepatitis. Am J Physiol Gastrointest Liver Physiol. 2009;296(1):G15–22.

39. Lu W, Maheshwari A, Misiuta I, Fox S, Chen N, Zigova T, et al. Neutrophil-speci fi c chemokines are produced by astrocytic cells but not neuronal cells. Dev Brain Res. 2005;155:127–34.

40. Bernal W, Auzinger G, Sizer E, Wendon J. Intensive care management for acute liver failure. Semin Liver Dis. 2008;28(2):188–200.

41. Als-Nielsen B, Gluud L, Gluud C. Non-absorbable disaccharides for hepatic encephalopathy: systematic review of randomised trials. Br Med J. 2004;328:1046–50.


43. Bajaj JS, Heuman DM, Wade JB, Gibson DP, Saeian K, Wegelin JA, et al. Rifaximin improves driving simulator performance in a randomized trial of patients with minimal hepatic enceph-alopathy. Gastroenterology. 2011;140(2):478–87.

44. Rolando N, Clapperton M, Wade J, Panetsos G, Mufti G, Williams R. Granulocyte colony-stimulating factor improves function of neutrophils from patients with acute liver failure. Eur J Gastroenterol Hepatol. 2000;12(10):1135–40.

45. Treacher D, Sabbato M, Brown K, Gant V. The effects of leucodepletion in patients who develop the systemic in fl ammatory response syndrome following cardiopulmonary bypass. Perfusion. 2001;16:67–73.


46. Harrison PM, Wendon JA, Gimson AE, Alexander GJ, Williams R. Improvement by acetyl-cysteine of hemodynamics and oxygen transport in fulminant hepatic failure. N Engl J Med. 1991;324(26):1852–7.

47. Liu Q, Duan ZP, Ha DK, Bengmark S, Kurtovic J, Riordan SM. Synbiotic modulation of gut fl ora: effect on minimal hepatic encephalopathy in patients with cirrhosis. Hepatology. 2004;39(5):1441–9.

48. Shawcross D, Davies N, Hodges S, Wright G, Jalan R. Hypothermia abolishes ammonia-induced neutrophil spontaneous oxidative burst [abstract]. Hepatology. 2006;44(4 Suppl 1):363A.

49. Jalan R, Schnurr K, Mookerjee R, Sen S, Cheshire L, Hodges S, et al. Alterations in the func-tional capacity of albumin in patients with decompensated cirrhosis is associated with increased mortality. Hepatology. 2009;50(2):555–64.

50. Jiang W, Desjardins P, Butterworth R. Cerebral in fl ammation contributes to encephalopathy and brain edema in acute liver failure: protective effect of minocycline. J Neurochem. 2009;109(2):485–93.

51. Stadlbauer V, Mookerjee R, Hodges S, Wright G, Davies N, Jalan R. Effect of probiotic treat-ment on deranged neutrophil function and cytokine responses in patients with compensated alcoholic cirrhosis. J Hepatol. 2008;48(6):945–51.


Keywords Astrocytes • Brain edema • Hepatic encephalopathy • In fl ammation • Intracellular signaling systems • Oxidative/nitrative stress

Introduction

Hepatic encephalopathy (HE) occurs in both acute and chronic liver disease. Chronic (or Type C) HE usually occurs in patients with underlying cirrhosis. It is character-ized by impaired neurological function, including changes in personality, altered mood, diminished intellectual capacity, and abnormal muscle tone and tremor [ 1 ] . HE in acute liver failure (fulminant hepatic failure) occurs following massive liver necrosis due to viral hepatitis (hepatitis B and C), hepatic neoplasm, vascular causes, acetaminophen toxicity, or exposure to various hepatotoxins. ALF is associated with the abrupt onset of delirium, seizures, and coma. Cerebral edema with increased intracranial pressure and brain herniation occurs in up to 80% of patients with ALF and represents the most frequent cause of death in these patients [ 2, 3 ] .

To date, the precise mechanism responsible for the development of both acute and chronic HE is not known. Increased blood and brain ammonia has been consid-ered an important pathogenetic factor and astrocytes appear to be the major cell type involved in its pathogenesis [ 4 ] . While the precise means by which ammonia causes

A. R. Jayakumar, PhD Department of Neuropathology , South Florida Foundation for Research and Education Inc., Miami VA Medical Center , Miami , FL , USA

M. D. Norenberg, MD (*) Department of Pathology, Biochemistry and Molecular Biology , Jackson Memorial Hospital, Miami VA Medical Center, University of Miami Hospital , 1611 NW, 12th Avenue , Miami , FL 33136 , USA e-mail: [email protected]

Chapter 5 Oxidative Stress in Hepatic Encephalopathy

Arumugam R. Jayakumar and Michael D. Norenberg

48 A.R. Jayakumar and M.D. Norenberg

neurotoxicity in HE are not clear, ammonia has been shown to impair bioenergetics, alter neurotransmission, cause electrophysiologic derangements, promote glutamate-mediated excitotoxicity, and stimulate various intracellular signaling pathways [ 5 ] . More recently, oxidative/nitrative stress (ONS) has been viewed as an important pathogenetic factor in HE. This chapter will summarize the involvement of ONS in the mechanism of HE, its consequences and potential role in therapy.

Oxidative/Nitrative Stress

Studies in Experimental Animals

Oxidative Stress

Evidence for the involvement of oxidative stress (OS) in HE initially arose from the observation that Alzheimer type II astrocytes, a prominent neuropathological component of HE, contain large amounts of lipofuscin pigment (indication of peroxidized lipids) [ 6 ] (Fig. 5.1 ). Excessive amounts of lipofuscin pigment were also detected in ammonia-treated astrocyte cultures [ 7, 8 ] . Subsequently, O’Connor and Costell [ 9 ] documented the presence of lipid peroxidation, a marker of OS,

Fig. 5.1 An Alzheimer type II astrocyte showing an enlarged and vacuolated nucleus containing a prominent nucleolus that is adherent to the nuclear membrane. No well-de fi ned cytoplasm is evident, except for the presence of lipofuscin pigment granules ( arrows ). Two normal-sized astro-cyte nuclei are present below the Alzheimer type II cell that also contain lipofuscin pigment

495 Oxidative Stress in Hepatic Encephalopathy

in brains of hyperammonemic mice. These fi ndings were further elaborated by Kosenko et al. [ 10– 13 ] , who showed an increase in superoxide production and lipid peroxidation, as well as a decrease in the activity of various antioxidant enzymes (glutathione peroxidase, manganese superoxide dismutase, and catalase) in rat brain cerebral cortex after acute hyperammonemia. Similar fi ndings were also observed in the cerebellum of rat after an acute ammonia infusion [ 14 ] , as well as in cerebral cortex of rats with thioacetamide (TAA)-induced ALF [ 15– 17 ] .

Increased hydrogen peroxide production [ 15, 18 ] , elevated levels of oxidized proteins [ 19 ] , and a decreased level of reduced glutathione as compared to oxidized glutathione (GSH/GSSG ratio) were identi fi ed in cerebral cortex of rats with TAA-induced ALF [ 15 ] . Decreased GSH/GSSG ratio was also detected in cerebral cortex of mice with azoxymethane-induced ALF [ 20, 21 ] . Hemeoxygenase-1 (HO-1), an enzyme that catalyzes the degradation of heme to iron and carbon monoxide and a marker of OS, was upregulated in hepatic devascularized rats [ 22, 23 ] , in mice with azoxymethane-induced ALF [ 24 ] , as well as in TAA-induced acute liver failure in rats [ 25 ] . Infusion of ammonia into the striatum of rats was shown to produce hydroxyl radicals [ 26 ] , while an increase in oxidized proteins was found in cerebral cortex of rats after TAA-induced acute liver failure (Fig. 5.2 ).

HO-1 upregulation was also observed in rat brain in a chronic model of HE (portacaval-shunted rat) [ 27 ] , and recently, Carbonero-Aguilar et al. [ 28 ] documented increased levels of malondialdehyde and hydroxynonenal in brains of portacaval-shunted rats. These studies strongly suggest that oxy-radicals and their derivatives are also produced in chronic HE. However, Yang et al. [ 29 ] found no changes in the level of oxidative stress markers in portacaval-shunted rats. Potential explanations for these con fl icting results may be the time of study selected (4 weeks vs. 6 weeks) and/or the sensitivity of the methods used to detect oxidative stress markers.

Nitrative Stress

Similar to OS, nitrative stress can also alter protein structure and potentially inter-fere with their cellular function. Nitrative stress has been documented in brains of

Fig. 5.2 Oxidation of brain proteins in TAA-treated rats. Oxidized proteins were detected by Western blot analysis with 2-DNPH. Proteins ranging in molecular weight from 90 to 40 kDa, as well as 32–24 kDa were highly oxidized in TAA-treated rats (lanes T1–4 from four separate animals) as compared to sham controls (C1–3 are controls from three separate animals)


acute and chronic liver failure. Increased nitric oxide synthase (NOS) activity, inducible nitric oxide synthase (iNOS) and neuronal nitric oxide synthase (nNOS) protein expression, along with increased protein tyrosine nitration were observed in portacaval-shunted rats [ 30– 32 ] . Increased protein tyrosine nitration was also observed in brains of rats with chronic liver failure produced by a low dose admin-istration of TAA [ 33 ] .

Increased brain nitric oxide (NO) production was observed in portacaval-shunted rats given an ammonia infusion, a model of acute liver failure [ 34 ] . Subsequently, elevated level of iNOS protein expression was demonstrated in rat brain astrocytes after acute ammonia infusion [ 35 ] . Increased endothelial nitric oxide synthase (eNOS) and iNOS protein expression were identi fi ed in brains of hepatic devascu-larized rats [ 22, 23 ] as well as following ischemic liver damage in rats [ 36 ] . Likewise, increased iNOS protein expression [ 37 ] and NO production were detected in brains of mice and rats, respectively, in TAA-induced acute liver failure [ 15 ] . Additionally, we found an increase in protein tyrosine nitration in cerebral cortex of rats after TAA-induced acute liver failure (Fig. 5.3 ).

Studies in Astrocyte Cultures

Oxidative Stress

While changes in OS markers have been demonstrated in different animal models of liver failure, much of the evidence for a role of OS in ammonia neurotoxicity has been derived from cell culture studies (for review, see Norenberg et al. [ 5 ] ).

Fig. 5.3 Protein tyrosine nitration from brains of TAA-treated rats. Protein tyrosine nitration was detected by western blot analysis with an antibody raised against 3-nitrotyrosine. Only two proteins are observed to be nitrated in sham treatment (control lane). By contrast, many proteins (between 85 and 40 kDa as well as 17.5 kDa) are observed to be highly nitrated (TAA-1 and 2 lane). Increase in protein nitration is also observed in TAA-treated rat brain at 132 and 20–30 kDa


A signi fi cant decrease in cellular glutathione (GSH) level was fi rst detected in ammonia-treated astrocyte cultures [ 38 ] . Since increased GSH is a major free radical scavenging system [ 39– 41 ] , we investigated whether ammonia produces free radicals in cultured astrocytes. Cultured astrocytes exposed to a pathophysio-logical concentration of ammonia (5 mM NH

4 Cl) were found to stimulate the

production of free radicals. Ammonia-induced free radical generation, including the activation of NADPH oxidase, was observed in cultured astrocytes [ 42– 44 ] (Fig. 5.4 ), while increased HO-1 expression was identi fi ed in cultured astrocytes after ammonia treatment [ 45 ] .

In addition to free radical production, a variety of morphological abnormalities, including enhanced stellation, a highly basophilic cytoplasm, prominent vacuoles and dense bodies were demonstrated in astrocyte cultures that had been exposed to ammonia [ 7, 8, 46 ] , and such effects were diminished by the antioxidants SOD and catalase [ 46 ] . Furthermore, natriuretic peptides, which are known to attenuate the production of reactive oxygen species (ROS) in other systems [ 47, 48 ] , were shown to reduce the accumulation of ROS in ammonia-treated cultured astrocytes [ 49 ] . Altogether, these studies suggest that oxy-radicals are produced by astrocytes in conditions associated with hyperammonemia.

Nitrative Stress

Astrocyte cultures exposed to ammonia caused an increase in iNOS protein expres-sion as well as NO production [ 35, 43 ] . Ammonia was shown to increase soluble guanylyl cyclase (a source of NO) in cultured astrocytes [ 50 ] . Additionally, stimula-tion of natriuretic peptide receptor C attenuated NOS activity in ammonia-treated astrocytes [ 49 ] .

Studies in Humans

While considerable evidence indicates the presence of oxidative stress markers in experimental models of HE, documentation of OS in humans is limited.

Fig. 5.4 Time-dependent changes in free radical production following treatment with ammonia (5 mM NH

4 Cl) in cultured

astrocytes. * p < 0.05 vs. control


Increased amount of lipofuscin pigment was found in brains of patients with HE [ 6, 51 ] . Elevated blood levels of free radicals were also identi fi ed in patients with HE resulting from chronic alcohol abuse which was associated with diminished antioxidative capacity [ 52 ] . Increased SOD activity, thiobarbituric acid reactive substances, and decreased catalase activities were observed in cirrhotic children [ 53 ] . Increased NO after transjugular intrahepatic portosystemic shunt (TIPS) inser-tion in patients with cirrhosis [ 54 ] , as well as elevated levels of tyrosine-nitrated proteins, heat shock protein-27, and 8-hydroxyguanosine (markers of RNA oxida-tion), was described in the cerebral cortex in patients with HE [ 55 ] .

Mechanisms of ONS Formation

Intracellular Calcium

While the precise mechanism by which ammonia generates free radicals is not clear, the elevation of intracellular Ca 2+ ([Ca 2+ ]) is likely an important factor as Ca 2+ has been shown to stimulate the production of RONS in other conditions [ 56– 58 ] . It is noteworthy that a rise in [Ca 2+ ]

i was shown to be an early event following ammonia

exposure to cultured astrocytes [ 35, 59, 60 ] . Consistent with these fi ndings, we recently reported that treatment of astrocyte cultures with the Ca 2+ chelator, 1,2-bis-( o -aminophenoxy)-ethane- N , N ,- N ¢ , N ¢ -tetraacetic acid tetraacetoxy-methyl ester (BAPTA), signi fi cantly blocked the ammonia-induced production of free radicals [ 44 ] . The ammonia-induced increase in [Ca 2+ ]

i is likely due to a rise in intracellular

pH since trimethylamine, a weak base, also increased [Ca 2+ ] i concentration in

cultured astrocytes [ 60 ] . Ca 2+ generates RONS likely through the activation of various Ca 2+ -dependent

enzymes, including constitutive nitric oxide synthase (cNOS) [ 61 ] , the cytosolic form of phospholipase A2 (cPLA2) [ 62 ] whose product, arachidonic acid (AA), is known to produce free radicals [ 63 ] and NADPH oxidase (NOX) [ 44, 64 ] , all of which generate superoxides. We recently reported that astrocytes exposed to ammo-nia showed increased activities of cNOS, NOX, and PLA2 and that pretreatment of cultures with their respective inhibitors blocked free radical production [ 44 ] . Additionally, ammonia-induced increase in cNOS, and PLA2 and NOX activities were blocked by BAPTA [ 44 ] .

The Mitochondrial Permeability Transition in ONS Production

One factor that is known to induce free radicals is the mitochondrial permeability transition (mPT), a Ca 2+ -dependent process associated with a collapse of the inner mitochondrial membrane potential due to a sudden opening of the permeability transition pore (PTP) in the inner mitochondrial membrane [ 65– 67 ] . Opening of the pore increases the permeability of the inner mitochondrial membrane to protons,


ions, and other small solutes (<1,500 Da) resulting in a collapse of the inner mitochondrial membrane potential which then leads to mitochondrial dysfunc-tion and enhanced free radical production [ 68, 69 ] .

While OS is a consequence of the mPT, it can also be a major cause of the mPT [ 70, 71 ] . This may occur due to the oxidation of pyridine nucleotides [ 72 ] , which diminishes glutathione levels, thereby decreasing the activity of glutathione peroxidase resulting in free radical production and induction of the mPT [ 71 ] . Additionally, ROS-mediated oxidation of thiol groups on mitochondrial proteins can result in pore opening [ 70 ] .

Electron Transport Chain

Another pathway by which ammonia may generate free radicals is through inhibition of the mitochondrial electron transport chain (ETC). Hyperammonemia has been shown to inhibit the ETC in brain [ 73, 74 ] . It was recently demonstrated that rats treated with the liver toxin carbon tetrachloride signi fi cantly inhibited complexes I, II, and IV in brain. Such effects were reversed by treatment of animals with the antioxi-dant N -acetylcysteine (NAC) or with the iron chelator desferrioxamine (DFX) which inhibits lipid peroxidation and hydroxyl radical production created by the Fenton reaction [ 75, 76 ] . Similar fi ndings were observed in rat brain after acetaminophen-induced liver failure [ 77 ] . Ammonia is also known to inhibit the activity of a -ketoglutarate dehydrogenase ( a -KGDH). Such inhibition is known to diminish FADH2 and NADH formation in the Krebs’ cycle, leading to NAD hyperoxidation and subsequent inhibition of the ETC, ultimately resulting in free radical formation [ 78 ] .

Nuclear Factor-Kappa B

Nuclear factor-kappa B (NF- k B) is a major transcription factor known to activate many genes, including NOX, PLA2, and iNOS that cause excessive oxy-nitro radical formation [ 79, 80 ] . It has been shown that cultured astrocytes exposed to ammonia caused the activation of NF- k B [ 35, 43 ] and inhibition of such activation attenuated ammonia-induced upregulation of iNOS protein expression and the subsequent generation of NO [ 35, 43 ] . It was also recently demonstrated that astro-cyte cultures from transgenic (Tg) mice with a functional inactivation of astrocytic NF- k B exhibit a lesser increment in iNOS and NADPH oxidase activity after ammonia treatment as compared to astrocytes derived from WT mice [ 37 ] .

N -Methyl D -Aspartate Receptors

Activation of N -methyl d -aspartate (NMDA) receptors can be an additional source of free radicals in HE. Acute ammonia intoxication was shown to activate NMDA


receptors in rat brain [ 13 ] , and inhibition of the receptor with MK-801 reversed the ammonia-induced decrease in the activity of various antioxidant enzymes (glutathi-one peroxidase, manganese superoxide dismutase, and catalase) in rat brain [ 13, 81, 82 ] . These studies indicate that ammonia-induced oxidative stress in brain was mediated, in part, by excessive activation of NMDA receptors. It should be noted that in addition to their neuronal localization, NMDA receptors are also expressed in astrocytes [ 83– 85 ] . Activation of these receptors is well known to increase intracellular calcium [ 86 ] . It is thus possible that increased intracellular calcium, by activation of NMDA receptors, may also contribute to the formation of free radicals in HE.

Glutamine

The synthesis of glutamine in astrocytes has generally been viewed as the principal means of ammonia detoxi fi cation in brain. However, recent studies suggest that some, if not most, of the deleterious effects of ammonia may actually be mediated by glutamine rather than ammonia per se. Studies have shown that many of the ammonia effects on astrocytes can be inhibited by interference with the synthesis of glutamine, by blocking the entry of glutamine into mitochondria, or by inhibition of mitochondrial glutamine hydrolysis [ 87, 88 ] . These fi ndings indicate that glutamine hydrolysis in mitochondria and the subsequent increase in mitochondrial ammonia content constitute a major pathway by which ammonia neurotoxicity occurs (the Trojan horse hypothesis) (Fig. 5.5 ).

Treatment of cultured astrocytes with 4.5 mM glutamine was shown to increase free radical production [ 89 ] , which was blocked by cyclosporine A (CsA), an inhibi-tor of the mPT. It was also blocked by 6-diazo-5-oxo- l -norleucine (DON), an inhib-itor of phosphate-activated glutaminase, suggesting that mitochondrial ammonia released by glutamine hydrolysis is responsible for the generation of free radicals.

Fig. 5.5 Metabolism of ammonia (NH 4 + ) in astrocytes resulting in the mitochondrial production

of reactive oxygen species (ROS). Glutamine, synthesized by glutamine synthatase (GS), enters mitochondria through the glutamine transporter (GLN-Tx). Glutamine is then hydrolyzed by phosphate-activated glutaminase. The “unloading” of ammonia from glutamine led to the so-called Trojan horse hypothesis of ammonia neurotoxicity. GLU glutamate


Additionally, it was recently shown that l -histidine, an inhibitor of mitochondrial glutamine transport, mitigated oxidative stress, the mPT, as well as cell swelling in cultured astrocytes treated with ammonia [ 90 ] . l -histidine was subsequently found to attenuate oxidative stress, the mPT, as well as brain edema in a rat model of acute liver failure [ 25 ] . The above fi ndings indicate that astrocytes generate free radicals following glutamine exposure and that glutamine-induced oxidative and/or nitrative stress, likely through mitochondrial ammonia production, represents a fundamental mechanism in ammonia neurotoxicity.

Peripheral Benzodiazepine Receptor

A prominent feature of HE is the upregulation of the peripheral benzodiazepine receptor (PBR) [ 91, 92 ] , which has recently been renamed as the 18-kDa translocator protein (TSPO) [ 93 ] . The TSPO is distinct from the central benzodiazepine receptor in its molecular structure, pharmacology, anatomical distribution, subcel-lular localization, and physiological functions [ 94 ] . While astrocytes and microglia are considered the predominant cell populations expressing the TSPO in the CNS [ 95– 97 ] , they are also expressed in neurons, although at much lower levels as compared to astrocytes or microglia [ 98 ] .

Increased TSPOs have been reported in acute hyperammonemic mice [ 99, 100 ] and in portacaval-shunted rats [ 101 ] , as well as in postmortem brain specimens from patients with HE [ 102 ] . Furthermore, a signi fi cant increase of TSPOs was identi fi ed in cultured astrocytes after treatment with ammonia [ 103 ] . The signi fi cance of this upregulation relative to the pathogenesis of HE or hyperammonemia remains poorly understood. It is of interest that activation of the TSPO may also contribute to oxida-tive stress. In support of this possibility, ligands of the TSPO (PK11195, Ro5-4864, and protophorphyrin IX) were shown to induce free radicals in cultured astrocytes, microglia, and neurons [ 98 ] . On the other hand, TSPO gene knockdown was shown to protect against oxidative stress in a human glioblastoma cell line [ 104 ] . Additionally, Görg et al. [ 105 ] showed that other TSPO ligands (diazepam, PK11195, Ro5-4864, and diazepam binding inhibitor) induce protein tyrosine nitration in cul-tured astrocytes, as well as in rat brain in vivo. Some of these effects were additive to those produced by ammonia. In aggregate, these studies suggest that upregulation of TSPO may contribute to the pathogenesis of HE by also increasing the level of ONS.

The means by which TSPO produces free radical in neural cells is not known. Hirsch et al. [ 106 ] reported that TSPO ligands inhibited mitochondrial respiration. It is therefore possible that free radical production after exposure of cells to TSPO ligands may be mediated by inhibition of mitochondrial respiratory complexes. Additionally, TSPO is believed to be a component of the mPT pore [ 107– 111 ] . We previously showed that the TSPO ligand Ro5-4864 at nanomolar concentration induced the mPT [ 112 ] . Using a gene knockdown approach, it was recently demon-strated that inhibition of TSPO protein synthesis signi fi cantly prevented the mPT [ 113 ] .


As the mPT is a known source of free radicals (noted above), it is possible that a TSPO-mediated mPT may be another source of free radical formation in HE.

Manganese

Manganese is an essential trace element. At low levels, manganese binds with superoxide dismutase to form manganese-superoxide dismutase (Mn-SOD), an important antioxidant enzyme in mitochondria [ 114 ] . However, when excessive, manganese contributes to neurological abnormalities such as parkinsonism and dystonia [ 115 ] . Chronic exposure of various cell types to manganese was shown to induce oxidative stress [ 116– 118 ] . Exposure of cultured astrocytes to manganese decreases energy production and antioxidant capacity, as well as stimulates the synthesis of glutamine [ 118 ] . It is possible that the manganese-induced activation of glutamine synthesis may also contribute to ONS.

Manganese has also been implicated in the pathogenesis of HE [ 119 ] . Manganese is elevated in plasma and brains of patients with cirrhosis or in individuals who had surgically created portal-systemic shunts. Selective neuronal loss in the basal ganglia (especially in the globus pallidus) and reactive gliosis are prominent features of manganese neurotoxicity in HE. T1-weighted magnetic resonance imaging (MRI) intensity of the globus pallidus suggested the possible accumulation of manganese in this region [ 120– 122 ] . Subsequent studies indeed disclosed elevated manganese levels in the globus pallidus obtained at autopsy from patients with chronic liver disease [ 123, 124 ] . A concomitant loss of dopamine D2 binding sites was also identi fi ed in these specimens [ 125 ] .

Morphologic and functional changes after exposure of astrocytes to manganese are similar to those observed after ammonia treatment. Cultured astrocytes exposed to 5 mM ammonia or 100 m M manganese acetate were shown to increase both free radical production and l -arginine uptake (a precursor of NO), and such effects were synergized when manganese was co-treated with ammonia [ 126, 127 ] . Similarly, exposure of primary cortical astrocytes to a low concentration of manganese (10 m M) was shown to potentiate interferon-gamma (IFN- g ) and tumor necrosis factor-alpha (TNF- a )-induced expression of iNOS mRNA and protein along with an increased production of NO [ 128 ] . The potentiating effect was a consequence of the activation of soluble guanylate cyclase and MAPK signaling pathways [ 128 ] . Cultured astro-cyte exposed to manganese was also shown to induce the mPT [ 129 ] and to inhibit glutamate uptake by a process involving oxidative stress [ 130, 131 ] . Additionally, Hazell et al. [ 132 ] demonstrated that treatment of rats with manganese chloride led to an increase in manganese level in brain that was accompanied by the development of pathological changes similar to those seen in HE (Alzheimer type II astrocyto-sis), and such changes were signi fi cantly reduced when rats were treated with the antioxidant NAC. These studies suggest that manganese contributes to oxidative stress in HE and that such effect is exacerbated in the presence of ammonia.


In fl ammation

Recent studies have suggested that in fl ammation plays a signi fi cant role in the pathogenesis of ALF [ 133– 137 ] . Patients with ALF frequently develop infections and sepsis, and when present, the severity of encephalopathy is greatly exacerbated [ 138 ] . Further, induction of endotoxemia with lipopolysaccharide (LPS) in rats was shown to aggravate the brain edema and encephalopathy associated with ALF [ 138 ] . Consistent with a role of in fl ammation, blood levels of TNF- a , IL-1 b , and IL-6 are elevated in patients with ALF [ 139– 141 ] . High ammonia levels in brain may also contribute to the production of cytokines as a recent study showed increased levels of IL-1 b , and other in fl ammatory mediators in brains of hyperammonemic rats [ 22, 142, 143 ] . Additionally, astrocyte cultures exposed to cytokines (TNF- a , IL-1 b , IL-6, and IFN- g ) were recently shown to activate NF- k B and blocking this activa-tion prevented astrocyte swelling [ 144 ] . Since cytokines are well-known inducers of oxidative stress and activators of NF- k B [ 145 ] , it is likely that, in addition to ammonia, cytokines also contribute to the ONS in HE.

Additional Cellular Sources of Free Radicals

Microglia

As noted earlier, the available data indicate that astrocytes are a major source of free radicals in brain in HE. However, other neural cells may also contribute to RONS formation in HE. Recent studies have demonstrated activation of microglial cells in ALF as well as in a rat model of hyperammonemia [ 22, 143 ] . It is likely that microglia, the principal in fl ammatory cell in brain [ 146 ] , play a role in the production of free radicals in HE since activated microglia are well known to induce free radical for-mation [ 147 ] . Once activated by stimulation of cell surface receptors [ 148 ] , micro-glial cells produce proin fl ammatory cytokines and other in fl ammatory mediators, including prostaglandins and arachidonic acid that are well known to induce free radical formation in the CNS [ 149 ] . Additionally, ammonia and glutamine were shown to induce free radical production in cultured BV2 microglia cells [ 150 ] . These studies suggest that microglial cells contribute to the ONS observed in HE.

Endothelial Cells

Another cell type that may potentially be involved in the production of free radicals in HE are brain endothelial cells (ECs). ECs perform a variety of functions, including provision of a barrier against potentially toxic substances, transport of nutrients, and leukocyte traf fi cking. ECs are the fi rst resident brain cells that could be impacted by blood-derived “toxins” (e.g., ammonia, cytokines). This may trigger an in fl ammatory


response, including the production of free radicals [ 151 ] . It is well known that LPS and systemic cytokines activate brain ECs [ 152 ] that subsequently produce free radicals [ 153 ] . In unpublished observations, we found free radical formation is increased in endothelial cells that are exposed to ammonia.

Consequences of ONS

Astrocyte Swelling/Brain Edema

Brain edema and the associated increase in intracranial pressure and brain herniation are major complications in patients with ALF [ 154 ] . Astrocyte swelling represents the principal alteration of this condition [ 91, 155, 156 ] . Ammonia plays a key role in the development of astrocyte swelling and brain edema in ALF [ 157, 158 ] . While mechanisms responsible for astrocyte swelling/brain edema in ALF remain poorly understood, recent studies have demonstrated an important role of ONS in this process. Exposure of cultured astrocytes to ammonia or oxidants caused cell swelling [ 159, 160 ] , which was attenuated by antioxidants or NO synthase inhib-itors. Additionally, exposure of astrocytes to cytokines (IL-1 b , IL-6, TNF- a , and IFN- g ) resulted in signi fi cant cell swelling, a process that was markedly potentiated when cultures were previously treated (“sensitized”) with ammonia [ 144 ] .

While the means by which ONS contribute to astrocyte swelling in HE is not well understood, ONS was shown to activate various signaling pathways, including activation of mitogen-activated protein kinases (MAPKs), and the transcription factors p53 and NF- k B. These signaling factors ultimately activate membrane ion channels/transporters/exchangers (ion transporting systems, ITSs), and such activa-tion leads to disturbances in cell volume homoeostasis [ 5 ] . These ITSs include the Na + -K + -2Cl − cotransporter (NKCC), volume-sensitive osmolyte anion channels (VSOAC), Na + /Ca 2+ exchanger (NCX), and the Na + /H + exchanger (NHE) that is functionally coupled to the Cl − /HCO

3 − exchanger, as well as the nonselective cation

channel (NCCa-ATP channel). For reviews on these ion transport systems, see Kahle et al. [ 161 ] , Jayakumar and Norenberg [ 162 ] , Simard et al. [ 163 ] .

It was recently demonstrated that exposure of cultured astrocytes to ammonia caused an increase in nitrated/carbonylated proteins [ 164, 165 ] . Additionally, cultured astrocytes exposed to ammonia or oxidants/NO donors signi fi cantly increased oxidation and/or nitration as well as the activation of NKCC1 [ 166 ] , and antioxidants, including Mn(III) tetrakis (4-benzoic acid) porphyrin (MnTBAP), a cell permeant superoxide dismutase mimetic, dimethylthiourea (a hydroxyl radical scavenger), Tempol (a cell permeable superoxide scavenger), catalase (a hydrogen peroxide decomposer), a -tocopherol (a lipid-soluble antioxidant), or the NOS inhibitor L-NAME as well as the peroxynitrite scavenger uric acid signi fi cantly reduced NKCC activity as well as cell swelling [ 166 ] . An increase in the activity of NCX in ammonia-treated astrocytes was also observed and the antioxidants MnTBAP and Tempol signi fi cantly diminished ammonia-induced NCX activity


(unpublished observations). Ammonia also increased the activity of NHE1, and this activity was diminished by antioxidants (PBN and catalase), and the NOS inhibitor L-NAME. These studies suggest that ammonia-induced ONS in fl uences various signaling pathways that ultimately activate membrane ion transporting systems.

Activation of ion transporting system will increase the intracellular ionic concentration. To maintain osmo-neutrality, water will enter the cell resulting in astrocyte swelling/brain edema. Such water entry is facilitated by the presence of the water channel aquaporin-4 (AQP4). Increased AQP4 expression in the plasma membrane of ammonia and manganese-treated astrocytes was recently implicated in the development of astrocyte swelling/brain edema in ALF. Cultured astrocytes exposed to a pathophysiological concentration of ammonia and manganese were shown to increase the AQP4 content in the plasma membrane [ 167, 168 ] , and such effect was blocked by antioxidants (PBN, Tempol) or with the NOS inhibitor L-NAME [ 168 ] , suggesting that ONS, in addition to increasing NKCC activity, also caused the overexpression of AQP4. Additionally, rats treated with TAA showed an increase in AQP4 protein in the plasma membrane of cortical astrocytes [ 169 ] . Treatment of rats with l -histidine (a potent antioxidant, as well as an inhibitor of glutamine transport into mitochondria) diminished TAA-induced AQP4 accumulation in the plasma membrane of cortical astrocytes and blocked TAA-induced brain edema [ 169 ] . Altogether, these fi ndings suggest that the accumulation of AQP4 in astrocytic plasma membranes is a consequence of ONS and a factor in the astrocyte swelling/brain edema in ALF (Fig. 5.6 ).

Fig. 5.6 Schematic representation of mechanisms by which ammonia leads to ONS and cell swelling in Type A HE. (1) Mobilization of intracellular calcium; (2) activation of Ca 2+ -dependent RONS producing enzymes (PLA2, cNOS, NOX; not shown); (3) activation of NF- k B by MAPKs, p53, TSPO, and the mPT; (4) activation of RONS producing factors by NF- k B activation (iNOS, NOX, and cytokines; not shown); (5) ROS generation via the mPT and TSPO; (6) activation of ITSs and AQP4 by ONS, resulting in astrocyte swelling/brain edema


Neurobehavioral Defects

While ONS contributes to astrocyte swelling/brain edema in acute HE, the consequences of ONS in chronic HE are unclear. Only a few studies have examined the role of ONS in the neurobehavioral abnormalities associated with chronic HE. Rats that underwent portal vein ligation were shown to increase protein tyrosine nitration, RNA oxidation, IL-6 mRNA increase in brains, which may have impaired locomotor activity [ 170 ] . Further, these authors reported that prevention of protein tyrosine nitration and RNA oxidation with indomethacin, a nonspeci fi c cyclooxygenase-2 inhibitor that also has antioxidant properties, prevented brain protein tyrosine nitration, RNA oxidation, as well as disturbances in locomotor activity associated with chronic HE [ 170 ] .

As noted in ONS , one consequence of ammonia neurotoxicity is the activation of NMDA receptors. Activation of these receptors was shown to induce behavioral changes such as impairment in active and passive avoidance behavior, conditional discrimination learning, as well as in long-term potentiation [ 171 ] . Such effects were mediated through the glutamate–nitric oxide–cyclic GMP pathway [ 172 ] . Ammonia was also shown to inhibit the induction and maintenance of long-term potentiation and these effects were blocked by l -carnitine, which has antioxidant properties, as well as by DL-APV, an antagonist of the NMDA receptor [ 173 ] . Since activation of NMDA receptor is well known to induce an increase in intracellular calcium and subsequent production of free radicals [ 86 ] , it is possible that NMDA receptor-mediated ONS in brain may contribute to the observed behavioral abnormalities.

Therapy of HE with Antioxidants

Treatment of experimental animals with HE/hyperammonemia with antioxidants (e.g., ascorbate, a -tocopherol, desferrioxamine, butylated-hydroxyanisole, dimethyl-sulfoxide, and dimethylthiourea) was shown to have bene fi cial effects by improving antioxidant status as well as their clinical condition [ 174, 175 ] . The antioxidant melatonin was shown to reduce blood and brain ammonia level as well as attenuate brain lipid peroxidation in rats after TAA injection [ 16 ] . Additionally, increased malondialdehyde levels and decreased glutathione peroxidase, catalase, and super-oxide dismutase activities were found in the hippocampal tissue of rats with portal hypertension (a model of low-grade HE), and such effects were reversed when rats were treated with curcumin, a known antioxidant, as well as an anti-in fl ammatory agent [ 176 ] .

Rats treated with morin (3,5,7,2 ¢ ,4 ¢ -pentahydroxy fl avone), a fl avonol, were shown to be protected against oxidative stress in brains of chronic hyperammone-mic rats [ 177 ] . The therapeutic potential of antioxidants, including PBN, catalase, and the NOS inhibitor L-NAME in TAA-induced acute liver failure in rats was recently shown by Norenberg et al. [ 19 ] . Additionally, increased NF- k B activation, a source of nitro-radicals, was found in TAA-treated rat brain and BAY 11-7082, an


inhibitor of NF- k B, signi fi cantly reduced the brain edema (unpublished observations). Likewise, transgenic (Tg) mice that have a functional inactivation of astrocytic NF- k B are resistant to TAA-induced iNOS protein expression and brain edema in acute liver failure [ 37 ] .

The antioxidant NAC has proven useful in reducing the brain edema in acute liver failure [ 20 ] and in the management of patients with ALF [ 178– 181 ] . Additionally, NAC was shown to delay the progression of encephalopathy in azoxymethane-induced ALF in mice, as well as to reduce the brain water content and proin fl ammatory cytokine levels [ 21 ] . Mannitol, which is used for the treatment of the brain edema in ALF due to its osmotic effect, also has antioxidant properties [ 182, 183 ] . Additionally, hypothermia which has been shown to improve the brain edema in animals and humans with ALF is also known to reduce free radical production [ 184 ] .

Conclusions

ONS has evolved in recent years as a major pathogenetic factor in HE/ALF. A growing body of evidence indicates the presence of ONS in brain in experimental models of acute and chronic liver failure. While the factors responsible for ONS formation in HE remain incompletely understood, it appears that ammonia-induced increase in intra-cellular calcium is an early event responsible for the production of free radicals. Such free radical formation occurs likely through activation of various Ca 2+ -dependent enzymes, including cNOS, PLA2, and NOX, the induction of the mPT, and activation of the major in fl ammatory transcription factor NF- k B.

While increased ONS in chronic HE has been demonstrated by some groups, its consequences are not well established. Additional studies on the role of ONS in chronic HE are clearly needed. On the other hand, the role of ONS in acute HE is relatively well established. Increased ONS has been documented in numerous studies, and antioxidants were shown to be protective against ammonia-induced astrocyte swelling and brain edema in acute liver failure. The antioxidant NAC is already in clinical trials. We anticipate that further recognition of ONS as a major factor in the pathogenesis of HE/ALF will be exploited into novel therapies for the treatment of patients af fl icted with HE.

Acknowledgments This work was supported by a Merit Review from the Department of Veterans Affairs and by a grant from the National Institutes of Health (DK063311).

References

1. Lockwood AH. Hepatic encephalopathy. Boston: Butterworth-Heinemann; 1992. 2. Ede RJ, Williams R. Hepatic encephalopathy and cerebral edema. Semin Liver Dis.

1986;6:107–18. 3. Hoofnagle JH, Carithers Jr RL, Shapiro C, Ascher N. Fulminant hepatic failure: summary of

a workshop. Hepatology. 1995;21:240–52.


4. Norenberg MD. The role of astrocytes in hepatic encephalopathy. Neurochem Pathol. 1987;6(1–2):13–33.

5. Norenberg MD, Rama Rao KV, Jayakumar AR. Signaling factors in the mechanism of ammonia neurotoxicity. Metab Brain Dis. 2009;24:103–17.

6. Norenberg MD. The astrocyte in liver disease. In: Fedoroff S, Hertz L, editors. Advances in cellular neurobiology, vol. 2. New York: Academic; 1981. p. 303–52.

7. Gregorios JB, Mozes LW, Norenberg LOB, Norenberg MD. Morphologic effects of ammonia on primary astrocyte cultures. I: light microscopic studies. J Neuropathol Exp Neurol. 1985;44:397–403.

8. Gregorios JB, Mozes LW, Norenberg MD. Morphologic effects of ammonia on primary astro-cyte cultures. II: electron microscopic studies. J Neuropathol Exp Neurol. 1985;44:404–14.

9. O’Connor JE, Costell M. New roles of carnitine metabolism in ammonia toxicity. In: Grisolia A, Felipo V, Miana MD, editors. Cirrhosis, hepatic encephalopathy and ammonium toxicity. New York: Plenum; 1990. p. 183–95.

10. Kosenko E, Kaminsky Y, Grau E, Miñana MD, Grisolía S, Felipo V. Nitroarginine, an inhibitor of nitric oxide synthetase, attenuates ammonia toxicity and ammonia-induced alterations in brain metabolism. Neurochem Res. 1995;20:451–6.

11. Kosenko E, Felipo V, Montoliu C, Grisolía S, Kaminsky Y. Effects of acute hyperammonemia in vivo on oxidative metabolism in nonsynaptic rat brain mitochondria. Metab Brain Dis. 1996;12:69–82.

12. Kosenko E, Kaminsky Y, Kaminsky A, Valencia M, Lee L, Hermenegildo C, Felipo V. Superoxide production and antioxidant enzymes in ammonia intoxication in rats. Free Radic Res. 1997;27:637–44.

13. Kosenko E, Kaminski Y, Lopata O, Muravyov N, Felipo V. Blocking NMDA receptors prevents the oxidative stress induced by acute ammonia intoxication. Free Radic Biol Med. 1999;26:1369–74.

14. Singh S, Koiri RK, Trigun SK. Acute and chronic hyperammonemia modulate antioxidant enzymes differently in cerebral cortex and cerebellum. Neurochem Res. 2008;33:103–13.

15. Sathyasaikumar KV, Swapna I, Reddy PV, Murthy CHR, Dutta Gupta A, Senthilkumaran B, Reddanna P. Fulminant hepatic failure in rats induces oxidative stress differentially in cere-bral cortex, cerebellum and pons medulla. Neurochem Res. 2007;32:517–24.

16. Túnez I, Muñoz MC, Medina FJ, Salcedo M, Feijóo M, Montilla P. Comparison of melatonin, vitamin E and L-carnitine in the treatment of neuro- and hepatoxicity induced by thioacetamide. Cell Biochem Funct. 2007;25:119–27.

17. Zarros A, Theocharis S, Skandali N, Tsakiris S. Effects of fulminant hepatic encephalopathy on the adult rat brain antioxidant status and the activities of acetylcholinesterase (Na + , K + - and Mg 2+ -ATPase): comparison of the enzymes’ response to in vitro treatment with ammonia. Metab Brain Dis. 2008;23:255–64.

18. Reddy PV, Murthy CR, Reddanna P. Fulminant hepatic failure induced oxidative stress in nonsynaptic mitochondria of cerebral cortex in rats. Neurosci Lett. 2004;368:15–20.

19. Norenberg MD, Jayakumar AR, Reddy PV, Moriyama M, Panickar KS. Oxidative-nitrosative stress, the permeability transition and MAP kinases in the mechanism of brain edema in acute liver failure. J Neurochem. 2008;104 Suppl 1:31.

20. Bémeur C, Vaquero J, Desjardins P, Butterworth RF. N-acetylcysteine attenuates cerebral complications of non-acetaminophen-induced acute liver failure in mice: antioxidant and anti-in fl ammatory mechanisms. Metab Brain Dis. 2010;25:241–9.

21. Bémeur C, Desjardins P, Butterworth RF. Antioxidant and anti-in fl ammatory effects of mild hypothermia in the attenuation of liver injury due to azoxymethane toxicity in the mouse. Metab Brain Dis. 2010;25:23–9.

22. Jiang W, Desjardins P, Butterworth RF. Hypothermia attenuates oxidative/nitrosative stress, encephalopathy and brain edema in acute (ischemic) liver failure. Neurochem Int. 2009;55:124–8.

23. Jiang W, Desjardins P, Butterworth RF. Minocycline attenuates oxidative/nitrosative stress and cerebral complications of acute liver failure in rats. Neurochem Int. 2009;55:601–5.


24. Bémeur C, Jiang W, Desjardins P, Butterworth RF. Mild hypothermia attenuates oxidative/nitrosative stress and cytotoxic brain edema in experimental acute liver failure. In: XXIVth International symposium on cerebral blood fl ow, metabolism and function and IXth interna-tional conference on quanti fi cation of brain function with PET, 2009; Chicago, IL, USA

25. Rama KV, Reddy PV, Tong X, Norenberg MD. Brain edema in acute liver failure: inhibition by L-histidine. Am J Pathol. 2010;176:1400–8.

26. Hilgier W, Anderzhanova E, Oja SS, Saransaari P, Albrecht J. Taurine reduces ammonia- and N-methyl-D-aspartate-induced accumulation of cyclic GMP and hydroxyl radicals in microdi-alysates of the rat striatum. Eur J Pharmacol. 2003;468:21–5.

27. Song G, Dhodda VK, Blei AT, Dempsey RJ, Rao VL. GeneChip analysis shows altered mRNA expression of transcripts of neurotransmitter and signal transduction pathways in the cerebral cortex of portacaval shunted rats. J Neurosci Res. 2002;68:730–7.

28. Carbonero-Aguilar P, Diaz-Herrero DM, Cremades O, Romero-Gómez M, Bautista J. Brain biomolecules oxidation in portacaval shunted rats. Liver Int. 2011;31(7):964–9.

29. Yang X, Bosoi CR, Jiang W, Tremblay M, Rose CF. Portacaval anastomosis-induced hyper-ammonemia does not lead to oxidative stress. Metab Brain Dis. 2010;25:11–5.

30. Rao VLR, Audet RM, Butterworth RF. Increased nitric oxide synthase activities and l-[3H]arginine uptake in brain following portacaval anastomosis. J Neurochem. 1995;65:677–81.

31. Suárez I, Bodega G, Rubino M, Felipo V, Fernández B. Neuronal and inducible nitric oxide synthase expression in the rat cerebellum following portacaval anastomosis. Brain Res. 2005;1047:205–13.

32. Suárez I, Bodega G, Arilla E, Felipo V, Fernández B. The expression of nNOS, iNOS and nitrotyrosine is increased in the rat cerebral cortex in experimental hepatic encephalopathy. Neuropathol Appl Neurobiol. 2006;32:594–604.

33. Hernández R, Martínez-Lara E, Del Moral ML, Blanco S, Cañuelo A, Siles E, Esteban FJ, Pedrosa JA, Peinado MA. Upregulation of endothelial nitric oxide synthase maintains nitric oxide production in the cerebellum of thioacetamide cirrhotic rats. Neuroscience. 2004;126:879–87.


35. Schliess F, Görg B, Fischer R, Desjardins P, Bidmon HJ, Herrmann A, Butterworth RF, Zilles K, Häussinger D. Ammonia induces MK-801-sensitive nitration and phosphorylation of protein tyrosine residues in rat astrocytes. FASEB J. 2002;16:739–41.

36. Sawara K, Desjardins P, Chatauret N, Kato A, Suzuki K, Butterworth RF. Alterations in expression of genes coding for proteins of the neurovascular unit in ischemic liver failure. Neurochem Int. 2009;55:119–23.

37. Jayakumar AR, Bethea JR, Tong XY, Gomez J, Norenberg MD. NF- k B in the mechanism of brain edema in acute liver failure: studies in transgenic mice. Neurobiol Dis. 2011;41:498–507.

38. Murthy CRK, Bender AS, Dombro RS, Bai G, Norenberg MD. Elevation of glutathione levels by ammonium ions in primary cultures of rat astrocytes. Neurochem Int. 2000;37:255–68.

39. Makar TK, Nedergaard M, Preuss A, Gelbard AS, Perumal AS, Cooper AJ. Vitamin E, ascor-bate, glutathione, glutathione disul fi de, and enzymes of glutathione metabolism in cultures of chick astrocytes and neurons: evidence that astrocytes play an important role in antioxidative processes in the brain. J Neurochem. 1994;62:45–53.

40. Cooper AJ, Kristal BS. Multiple roles of glutathione in the central nervous system. Biol Chem. 1997;378:793–802.

41. Murthy CRK, Rama Rao KV, Bai G, Norenberg MD. Ammonia induced production of free radicals in primary cultures of rat astrocytes. J Neurosci Res. 2001;66:282–8.

42. Rama Rao KV, Jayakumar AR, Norenberg DM. Ammonia neurotoxicity: role of the mito-chondrial permeability transition. Metab Brain Dis. 2003;18:113–27.

43. Sinke AP, Jayakumar AR, Panickar KS, Moriyama M, Reddy PV, Norenberg MD. NF k B in the mechanism of ammonia-induced astrocyte swelling in culture. J Neurochem. 2008;106:2302–11.

44. Jayakumar AR, Rama Rao KV, Tong XY, Norenberg MD. Calcium in the mechanism of ammonia-induced astrocyte swelling. J Neurochem. 2009;109 Suppl 1:252–7.


45. Warskulat U, Görg B, Bidmon HJ, Muller HW, Schliess F, Haussinger D. Ammonia-induced heme oxygenase-1 expression in cultured rat astrocytes and rat brain in vivo. Glia. 2002;40:324–36.

46. Norenberg MD, Jayakumar AR, Rama Rao KV. Oxidative stress in the pathogenesis of hepatic encephalopathy. Metab Brain Dis. 2004;19:313–29.

47. Woodard GE, Rosado JA. Natriuretic peptides in vascular physiology and pathology. Int Rev Cell Mol Biol. 2008;268:59–93.

48. De Vito P, Incerpi S, Pedersen JZ, Luly P. Atrial natriuretic peptide and oxidative stress. Peptides. 2010;31:1412–9.

49. Skowrońska M, Zielińska M, Albrecht J. Stimulation of natriuretic peptide receptor C attenu-ates accumulation of reactive oxygen species and nitric oxide synthesis in ammonia-treated astrocytes. J Neurochem. 2010;115:1068–76.

50. Konopacka A, Freśko I, Piaskowski S, Albrecht J, Zielińska M. Ammonia affects the activity and expression of soluble and particulate GC in cultured rat astrocytes. Neurochem Int. 2006;48:553–8.

51. Brunk UT. On the origin of lipofuscin; the iron content of residual bodies, and the relation of these organelles to the lysosomal vacuome. A study on cultured human glial cells. Adv Exp Med Biol. 1989;266:313–20.

52. Negru T, Ghiea V, Pasarica D. Oxidative injury and other metabolic disorders in hepatic encephalopathy. Rom J Physiol. 1999;36:29–36.

53. Ribeiro L, Andreazza AC, Salvador M, da Silveira TR, Vieira S, Nora DB, Bosa C, Di Napoli F, Schaf DV, Souza DO, Portela LV, Kapczinski F. Oxidative stress and S100B protein in cirrhotic children. Neurochem Res. 2007;32:1600–3.

54. Jalan R, Olde Damink SW, Ter Steege JC, Redhead DN, Lee A, Hayes PC, Deutz NE. Acute endotoxemia following transjugular intrahepatic stent-shunt insertion is associated with systemic and cerebral vasodilatation with increased whole body nitric oxide production in critically ill cirrhotic patients. J Hepatol. 2011;54:265–71.

55. Görg B, Qvartskhava N, Bidmon HJ, Palomero-Gallagher N, Kircheis G, Zilles K, Häussinger D. Oxidative stress markers in the brain of patients with cirrhosis and hepatic encephalopathy. Hepatology. 2010;52:256–65.

56. Duan Y, Gross RA, Sheu SS. Ca 2+ -dependent generation of mitochondrial reactive oxygen species serves as a signal for poly(ADP-ribose) polymerase-1 activation during glutamate excitotoxicity. J Physiol. 2007;585:741–58.

57. Hernández-Fonseca K, Cárdenas-Rodríguez N, Pedraza-Chaverri J, Massieu L. Calcium-dependent production of reactive oxygen species is involved in neuronal damage induced during glycolysis inhibition in cultured hippocampal. J Neurosci Res. 2008;86:1768–80.

58. Chinopoulos C, Adam-Vizi V. Calcium, mitochondria and oxidative stress in neuronal pathol-ogy. Novel aspects of an enduring theme. FEBS J. 2006;273:433–50.

59. Norenberg MD, Rama Rao KV, Jayakumar AR. The mitochondrial permeability transition in ammonia neurotoxicity. In: Jones EA, Meijer AA, Chamuleau RA, editors. Encephalopathy and nitrogen metabolism in liver failure. Dordrecht: Kluwer; 2003. p. 267–86.

60. Rose C, Kresse W, Kettenmann H. Acute insult of ammonia leads to calcium-dependent glutamate release from cultured astrocytes, an effect of pH. J Biol Chem. 2005;280:20937–44.

61. Mayer B, John M, Bohme E. Puri fi cation of a Ca 2+ /calmodulin-dependent nitric oxide synthase from porcine cerebellum. Cofactor-role of tetrahydrobiopterin. FEBS Lett. 1990;277:215–9.

62. Kramer RM, Sharp JD. Structure, function and regulation of Ca 2+ -sensitive cytosolic phospholipase A2 (cPLA2). FEBS Lett. 1997;410:49–53.

63. Cocco T, Di Paola M, Papa S, Lorusso M. Arachidonic acid interaction with the mitochondrial electron transport chain promotes reactive oxygen species generation. Free Radic Biol Med. 1999;27:51–9.

64. Reinehr R, Görg B, Becker S, Qvartskhava N, Bidmon HJ, Selbach O, Haas HL, Schliess F, Häussinger D. Hypoosmotic swelling and ammonia increase oxidative stress by NADPH oxidase in cultured astrocytes and vital brain slices. Glia. 2007;55:758–71.


65. Zoratti M, Szabo I. The mitochondrial permeability transition. Biochim Biophys Acta. 1995;1241:139–76.

66. Bernardi P, Colonna R, Costantini P, Eriksson O, Fontaine E, Ichas F, Massari S, Nicolli A, Petronilli V, Scorrano L. The mitochondrial permeability transition. Biofactors. 1998;8:273–81.

67. Norenberg MD, Rao KV. The mitochondrial permeability transition in neurologic disease. Neurochem Int. 2007;50:983–97.

68. Miller TJ, Phelka AD, Tjalkens RB, Dethloff LA, Philbert MA. CI-1010 induced opening of the mitochondrial permeability transition pore precedes oxidative stress and apoptosis in SY5Y neuroblastoma cells. Brain Res. 2003;14(963):43–56.

69. Votyakova TV, Reynolds IJ. Ca 2+ -induced permeabilization promotes free radical release from rat brain mitochondria with partially inhibited complex I. J Neurochem. 2005;93:526–37.

70. Halestrap AP, Wood fi eld KY, Connern CP. Oxidative stress, thiol reagents, membrane potential modulate the mitochondrial permeability transition by affecting nucleotide binding to the adenine nucleotide translocase. J Biol Chem. 1997;272:3346–54.

71. Kowaltowski AJ, Castilho RF, Vercesi AE. Mitochondrial permeability transition and oxidative stress. FEBS Lett. 2001;495:12–5.

72. Lehninger AL, Vercesi A, Bababunmi E. Regulation of Ca 2+ release from mitochondria by the oxidation-reduction state of pyridine nucleotides. Proc Natl Acad Sci U S A. 1978;75:1690–4.

73. Kosenko E, Felipo V, Montoliu C, Grisolía S, Kaminsky Y. Effects of acute hyperammonemia in vivo on oxidative metabolism in nonsynaptic rat brain mitochondria. Metab Brain Dis. 1997;12:69–82.

74. Qureshi K, Rao KV, Qureshi IA. Differential inhibition by hyperammonemia of the electron transport chain enzymes in synaptosomes and non-synaptic mitochondria in ornithine transcarbamylase-de fi cient spf-mice: restoration by acetyl-L-carnitine. Neurochem Res. 1998;23:855–61.

75. Sarco DP, Becker J, Palmer C, Sheldon RA, Ferriero DM. The neuroprotective effect of deferoxamine in the hypoxic-ischemic immature mouse brain. Neurosci Lett. 2000;282:113–6.

76. Boer LA, Panatto JP, Fagundes DA, Bassani C, Jeremias IC, Daufenbach JF, Rezin GT, Constantino L, Dal-Pizzol F, Streck EL. Inhibition of mitochondrial respiratory chain in the brain of rats after hepatic failure induced by carbon tetrachloride is reversed by antioxidants. Brain Res Bull. 2009;80:75–8.

77. Panatto JP, Jeremias IC, Ferreira GK, Ramos AC, Rochi N, Gonçalves CL, Daufenbach JF, Jeremias GC, Carvalho-Silva M, Rezin GT, Scaini G, Streck EL. Inhibition of mitochondrial respiratory chain in the brain of rats after hepatic failure induced by acetaminophen. Mol Cell Biochem. 2011;350:149–54.

78. Sheline CT, Wei L. Free radical-mediated neurotoxicity may be caused by inhibition of mitochondrial dehydrogenases in vitro and in vivo. Neuroscience. 2006;140:235–46.

79. Xie QW, Kashiwabara Y, Nathan C. Role of transcription factor NF-kappa B/Rel in induction of nitric oxide synthase. J Biol Chem. 1994;269:4705–8.

80. Kleinert H, Pautz A, Linker K, Schwarz PM. Regulation of the expression of inducible nitric oxide synthase. Eur J Pharmacol. 2004;500:255–66.

81. Hermenegildo C, Marcaida G, Montoliu C, Grisolía S, Minana MD, Felipo V. NMDA receptor antagonists prevent acute ammonia toxicity in mice. Neurochem Res. 1996;21:1237–44.

82. Marcaida G, Felipo V, Hermenegildo C, Minana MD, Grisolía S. Acute ammonia toxicity is mediated by the NMDA type of glutamate receptors. FEBS Lett. 1992;296:67–8.

83. Conti F, DeBiasi S, Minelli A, Melone M. Expression of NR1 and NR2A/B subunits of the NMDA receptor in cortical astrocytes. Glia. 1996;17:254–8.

84. Condorelli DF, Conti F, Gallo V, Kirchhoff F, Seifert G, Steinhäuser C, Verkhratsky A, Yuan X. Expression and functional analysis of glutamate receptors in glial cells. Adv Exp Med Biol. 1999;468:49–67.

85. Schipke CG, Ohlemeyer C, Matyash M, Nolte C, Kettenmann H, Kirchhoff F. Astrocytes of the mouse neocortex express functional N-methyl-D-aspartate receptors. FASEB J. 2001;15:1270–82.


86. Soria JM, Valdeolmillos M. Receptor-activated calcium signals in tangentially migrating cortical cells. Cereb Cortex. 2002;12:831–9.

87. Albrecht J, Norenberg MD. Glutamine: a Trojan horse in ammonia neurotoxicity. Hepatology. 2006;44:788–94.

88. Albrecht J, Zielińska M, Norenberg MD. Glutamine as a mediator of ammonia neurotoxicity: a critical appraisal. Biochem Pharmacol. 2010;80:1303–8.

89. Jayakumar AR, Rama Rao KV, Schousboe A, Norenberg MD. Glutamine-induced free radical production in cultured astrocytes. Glia. 2004;46:296–301.

90. Pichili VB, Rao KV, Jayakumar AR, Norenberg MD. Inhibition of glutamine transport into mitochondria protects astrocytes from ammonia toxicity. Glia. 2007;55:801–9.

91. Norenberg MD. A light and electron microscopic study of experimental portal-systemic (ammonia) encephalopathy. Progression and reversal of the disorder. Lab Invest. 1977;36:618–27.

92. Butterworth RF. The astrocytic (“peripheral-type”) benzodiazepine receptor: role in the pathogenesis of portal-systemic encephalopathy. Neurochem Int. 2000;36:411–6.

93. Papadopoulos V, Baraldi M, Guilarte TR, Knudsen TB, Lacapere JJ, Lindemann P, Norenberg MD, Nutt D, Weizman A, Zhang MR, Gavish M. Translocator protein (18 kDa): new nomen-clature for the peripheral-type benzodiazepine receptor based on its structure and molecular function. Trends Pharmacol Sci. 2006;27:402–9.

94. Krueger KE. Molecular and functional properties of mitochondrial benzodiazepine receptors. Biochim Biophys Acta. 1995;1241:453–70.

95. Itzhak Y, Baker L, Norenberg MD. Characterization of the peripheral-type benzodiazepine receptors in cultured astrocytes: evidence for multiplicity. Glia. 1993;9:211–8.

96. Park CH, Carboni E, Wood PL, Gee KW. Characterization of peripheral benzodiazepine type sites in a cultured murine BV-2 microglial cell line. Glia. 1996;16:65–70.

97. Vowinckel E, Reutens D, Becher B, Verge G, Evans A, Owens T, Antel JP. PK-11195 binding to the peripheral benzodiazepine receptor as a marker of microglia activation in multiple scle-rosis and experimental autoimmune encephalomyelitis. J Neurosci Res. 1997;50:345–53.

98. Jayakumar AR, Panickar KS, Norenberg MD. Effects on free radical generation by ligands of the peripheral benzodiazepine receptor in cultured neural cells. J Neurochem. 2002;83:1226–34.

99. Ducis I, Norenberg LO, Norenberg MD. Effect of ammonium chloride on the astrocyte ben-zodiazepine receptor. Brain Res. 1989;493:362–5.

100. Itzhak Y, Roig-Cantisano A, Dombro RS, Norenberg MD. Acute liver failure and hyperam-monemia increase peripheral-type benzodiazepine receptor binding and pregnenolone syn-thesis in mouse brain. Brain Res. 1995;705:345–8.

101. Giguere JF, Hamel E, Butterworth RF. Increased densities of binding sites for the ‘peripheral-type’ benzodiazepine receptor ligand [3H]PK 11195 in rat brain following portacaval anasto-mosis. Brain Res. 1992;585:295–8.

102. Lavoie J, Layrargues GP, Butterworth RF. Increased densities of peripheral-type benzodiaz-epine receptors in brain autopsy samples from cirrhotic patients with hepatic encephalopathy. Hepatology. 1990;11:874–8.

103. Itzhak Y, Norenberg MD. Ammonia-induced upregulation of peripheral-type benzodiazepine receptors in cultured astrocytes labeled with [3H] 11195. Neurosci Lett. 1994;177:35–8.

104. Zeno S, Zaaroor M, Leschiner S, Veenman L, Gavish M. CoCl(2) induces apoptosis via the 18 kDa translocator protein in U118MG human glioblastoma cells. Biochemistry. 2009;48:4652–61.

105. Görg B, Foster N, Reinehr R, Bidmon HJ, Höngen A, Häussinger D, Schliess F. Benzodiazepine-induced protein tyrosine nitration in rat astrocytes. Hepatology. 2003;37:334–42.

106. Hirsch JD, Beyer CF, Malkowitz L, Beer B, Blume AJ. Mitochondrial benzodiazepine receptors mediate inhibition of mitochondrial respiratory control. Mol Pharmacol. 1989;35:157–63.

107. Aprille JR. Reye’s syndrome: patient serum alters mitochondrial function and morphology in vitro . Science. 1977;197:908–10.


108. Szabo I, Zoratti M. The mitochondrial permeability transition pore may comprise VDAC molecules I. Binary structure and voltage dependence of the pore. FEBS Lett. 1993;330:201–5.

109. Zamzami N, Hirsch T, Dallaporta B, Petit PX, Kroemer G. Mitochondrial implication in accidental and programmed cell death: apoptosis and necrosis. J Bioenerg Biomembr. 1997;29:185–93.

110. Ravagnan L, Marzo I, Costantini P, Susin SA, Zamzami N, Petit PX, Hirsch F, Goulbern M, Poupon MF, Miccoli L, Xie Z, Reed JC, Kroemer G. Lonidamine triggers apoptosis via a direct, Bcl-2-inhibited effect on the mitochondrial permeability transition pore. Oncogene. 1999;18:2537–46.

111. Tatton WG, Olanow CW. Apoptosis in neurodegenerative diseases: the role of mitochondria. Biochim Biophys Acta. 1999;1410:195–213.

112. Rao KVR, Bai G, Jayakumar AR, Norenberg MD. Role of the peripheral benzodiazepine receptor and neurosteroids in the induction of the mitochondrial permeability transition in cultured astrocytes. J Neurochem. 2001;78 Suppl 1:25.

113. Panickar KS, Jayakumar AR, Norenberg MD. Downregulation of the 18-kDa translocator protein: effects on the ammonia-induced mitochondrial permeability transition and cell swell-ing in cultured astrocytes. Glia. 2007;55:1720–7.

114. Holley AK, Dhar SK, St. Clair DK. Manganese superoxide dismutase versus p53: the mito-chondrial center. Ann N Y Acad Sci. 2010;1201:72–8.

115. Pal PK, Samii A, Calne DB. Manganese neurotoxicity: a review of clinical features, imaging and pathology. Neurotoxicology. 1999;20:227–38.

116. Sun AY, Yang WL, Kim HD. Free radical and lipid peroxidation in manganese-induced neu-ronal cell injury. Ann N Y Acad Sci. 1993;679:358–63.

117. Desole MS, Esposito G, Migheli R, Fresu L, Sircana S, Zangani D, Miele M, Miele E. Cellular defence mechanisms in the striatum of young and aged rats subchronically exposed to man-ganese. Neuropharmacology. 1995;34:289–95.

118. Chen CJ, Liao SL. Oxidative stress involves in astrocytic alterations induced by manganese. Exp Neurol. 2002;175:216–25.

119. Butterworth RF. Metal toxicity, liver disease and neurodegeneration. Neurotox Res. 2010;18:100–5.

120. Pujol A, Graus F, Peri J, Mercader JM, Rimola A. Hyperintensity in the globus pallidus on T1-weighted and inversion-recovery MRI: a possible marker of advanced liver disease. Neurology. 1991;41:1526–7.

121. Chamuleau RA, Vogels BA, Bosman DK, Bovée WM. In vivo brain magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) in hepatic encephalopathy. Adv Exp Med Biol. 1994;368:23–31.

122. Norton NS, McConnell JR, Zetterman RK, Rodriguez-Sierra JF. A quantitative evaluation of magnetic resonance image signal changes of the brain in chronic hepatic encephalopathy. J Hepatol. 1994;21:764–70.

123. Krieger D, Krieger S, Jansen O, Gass P, Theilmann L, Lichtnecker H. Manganese and chronic hepatic encephalopathy. Lancet. 1995;346:270–4.

124. Pomier-Layrargues G, Spahr L, Butterworth RF. Increased manganese concentrations in pallidum of cirrhotic patients. Lancet. 1995;345:735.

125. Butterworth RF, Spahr L, Fontaine S, Layrargues GP. Manganese toxicity, dopaminergic dysfunction and hepatic encephalopathy. Metab Brain Dis. 1995;10:259–67.

126. Hazell AS, Norenberg MD. Ammonia and manganese increase arginine uptake in cultured astrocytes. Neurochem Res. 1998;23:869–73.

127. Jayakumar AR, Rama Rao KV, Kalaiselvi P, Norenberg MD. Combined effects of ammonia and manganese on astrocytes in culture. Neurochem Res. 2004;29:2051–6.

128. Moreno JA, Sullivan KA, Carbone DL, Hanneman WH, Tjalkens RB. Manganese potentiates nuclear factor-kappaB-dependent expression of nitric oxide synthase 2 in astrocytes by acti-vating soluble guanylate cyclase and extracellular responsive kinase signaling pathways. J Neurosci Res. 2008;86:2028–38.


129. Rao KV, Norenberg MD. Manganese induces the mitochondrial permeability transition in cultured astrocytes. J Biol Chem. 2004;279:32333–8.

130. Volterra A, Trotti D, Tromba C, Floridi S, Racagni G. Glutamate uptake inhibition by oxygen free radicals in rat cortical astrocytes. J Neurosci. 1994;14:2924–32.

131. Hazell AS, Norenberg MD. Manganese decreases glutamate uptake in cultured astrocytes. Neurochem Res. 1997;22:1443–7.

132. Hazell AS, Normandin L, Norenberg MD, Kennedy G, Yi JH. Alzheimer type II astrocytic changes following sub-acute exposure to manganese and its prevention by antioxidant treatment. Neurosci Lett. 2006;396:167–71.

133. O’Grady JG, Williams R. Management of acute liver failure. Schweiz Med Wochenschr. 1986;116:541–4.

134. Jalan R, Williams R. The in fl ammatory basis of intracranial hypertension in acute liver failure. J Hepatol. 2001;34:940–2.

135. Jalan R, Olde Damink SW, Hayes PC, Deutz NE, Lee A. Pathogenesis of intracranial hyper-tension in acute liver failure: in fl ammation, ammonia and cerebral blood fl ow. J Hepatol. 2004;41:613–20.

136. Shawcross D, Jalan R. The pathophysiologic basis of hepatic encephalopathy: central role for ammonia and in fl ammation. Cell Mol Life Sci. 2005;62:2295–304.

137. O’Beirne JP, Chouhan M, Hughes RD. The role of infection and in fl ammation in the patho-genesis of hepatic encephalopathy and cerebral edema in acute liver failure. Nat Clin Pract Gastroenterol Hepatol. 2006;3:118–9.

138. Wright G, Davies NA, Shawcross DL, Hodges SJ, Zwingmann C, Brooks HF, Mani AR, Harry D, Stadlbauer V, Zou Z, Williams R, Davies C, Moore KP, Jalan R. Endotoxemia pro-duces coma and brain swelling in bile duct ligated rats. Hepatology. 2007;45:1517–26.

139. Wilkinson SP, Arroyo V, Moodie H, Williams R. Proceedings: endotoxaemia in fulminant hepatic failure. Clin Sci Mol Med. 1974;46:30–1.

140. Wyke RJ, Canalese JC, Gimson AE, Williams R. Bacteraemia in patients with fulminant hepatic failure. Liver. 1982;2:45–52.

141. Odeh M, Sabo E, Srugo I, Oliven A. Serum levels of tumor necrosis factor-alpha correlate with severity of hepatic encephalopathy due to chronic liver failure. Liver Int. 2004;24:110–6.

142. Shawcross DL, Davies NA, Williams R, Jalan R. Systemic in fl ammatory response exacer-bates the neuropsychological effects of induced hyperammonemia in cirrhosis. J Hepatol. 2004;40:247–54.

143. Rodrigo R, Cauli O, Gomez-Pinedo U, Agusti A, Hernandez-Rabaza V, Garcia-Verdugo JM, Felipo V. Hyperammonemia induces neuroin fl ammation that contributes to cognitive impair-ment in rats with hepatic encephalopathy. Gastroenterology. 2010;139:675–84.

144. Rama Rao KV, Jayakumar AR, Tong X, Alvarez VM, Norenberg MD. Marked potentiation of cell swelling by cytokines in ammonia-sensitized cultured astrocytes. J Neuroin fl ammation. 2010;7:66.

145. Frank-Cannon TC, Alto LT, McAlpine FE, Tansey MG. Does neuroin fl ammation fan the fl ame in neurodegenerative diseases? Mol Neurodegener. 2009;4:47.

146. Harry GJ, Kraft AD. Neuroin fl ammation and microglia: considerations and approaches for neurotoxicity assessment. Expert Opin Drug Metab Toxicol. 2008;4:1265–77.

147. Park SY, Lee H, Hur J, Kim SY, Kim H, Park JH, Cha S, Kang SS, Cho GJ, Choi WS, Suk K. Hypoxia induces nitric oxide production in mouse microglia via p38 mitogen-activated protein kinase pathway. Brain Res Mol Brain Res. 2002;107:9–16.

148. Inoue K. Microglial activation by purines and pyrimidines. Glia. 2002;40:156–63. 149. Farooqui AA, Horrocks LA, Farooqui T. Modulation of in fl ammation in brain: a matter of fat.

J Neurochem. 2007;101:577–99. 150. Svoboda N, Kerschbaum HH. L-Glutamine-induced apoptosis in microglia is mediated by

mitochondrial dysfunction. Eur J Neurosci. 2009;30:196–206. 151. Rizzo MT, Leaver HA. Brain endothelial cell death: modes, signaling pathways, and rele-

vance to neural development, homeostasis, and disease. Mol Neurobiol. 2010;42:52–63.


152. Kacimi R, Giffard RG, Yenari MA. Endotoxin-activated microglia injure brain derived endothelial cells via NF- k B, JAK-STAT and JNK stress kinase pathways. J In fl amm (Lond). 2011;8:7.

153. Naassila M, Roux F, Beaugé F, Daoust M. Ethanol potentiates lipopolysaccharide- or interleukin-1 beta-induced nitric oxide generation in RBE4 cells. Eur J Pharmacol. 1996;313:273–7.

154. Blei AT. Cerebral edema and intracranial hypertension in acute liver failure: distinct aspects of the same problem. Hepatology. 1991;13:376–9.

155. Martinez AJ. Electron microscopy in human hepatic encephalopathy. Acta Neuropathol (Berl). 1968;11:82–6.

156. Traber PG, Dal Canto MC, Ganger D, Blei AT. Electron microscopic evaluation of brain edema in rabbits with galactosamine-induced fulminant hepatic failure: ultrastructure and integrity of the blood–brain barrier. Hepatology. 1987;7:1272–7.

157. Clemmesen JO, Larsen FS, Kondrup J, Hansen BA, Ott P. Cerebral herniation in acute liver failure is correlated with arterial ammonia concentration. Hepatology. 1999;29:648–53.

158. Córdoba J, Blei AT. Brain edema and hepatic encephalopathy. Semin Liver Dis. 1996;16:271–80.

159. Jayakumar AR, Panickar KS, Murthy CR, Norenberg MD. Oxidative stress and mitogen-activated protein kinase phosphorylation mediate ammonia-induced cell swelling and gluta-mate uptake inhibition in cultured astrocytes. J Neurosci. 2006;26:4774–84.

160. Moriyama M, Jayakumar AR, Tong XY, Norenberg MD. Role of mitogen-activated protein kinases in the mechanism of oxidant-induced cell swelling in cultured astrocytes. J Neurosci Res. 2010;88:2450–8.

161. Kahle KT, Simard JM, Staley KJ, Nahed BV, Jones PS, Sun D. Molecular mechanisms of ischemic cerebral edema: role of electroneutral ion transport. Physiology (Bethesda). 2009;24:257–65.

162. Jayakumar AR, Norenberg MD. The Na-K-Cl Co-transporter in astrocyte swelling. Metab Brain Dis. 2010;25:31–8.

163. Simard JM, Kahle KT, Gerzanich V. Molecular mechanisms of microvascular failure in central nervous system injury–synergistic roles of NKCC1 and SUR1/TRPM4. J Neurosurg. 2010;113:622–9.

164. Norenberg MD, Jayakumar AR, Rama Rao KV, Panickar KS. New concepts in the mecha-nism of ammonia-induced astrocyte swelling. Metab Brain Dis. 2007;22:219–34.

165. Widmer R, Kaiser B, Engels M, Jung T, Grune T. Hyperammonemia causes protein oxidation and enhanced proteasomal activity in response to mitochondria-mediated oxidative stress in rat primary astrocytes. Arch Biochem Biophys. 2007;464:1–11.

166. Jayakumar AR, Liu M, Moriyama M, Ramakrishnan R, Forbush III B, Reddy PV, Norenberg MD. Na-K-Cl cotransporter-1 in the mechanism of ammonia-induced astrocyte swelling. J Biol Chem. 2008;283:33874–82.

167. Rama Rao KV, Chen M, Simard JM, Norenberg MD. Increased aquaporin-4 expression in ammonia-treated cultured astrocytes. Neuroreport. 2003;14:2379–82.

168. Rao KV, Jayakumar AR, Reddy PV, Tong X, Curtis KM, Norenberg MD. Aquaporin-4 in manganese-treated cultured astrocytes. Glia. 2010;58:1490–9.

169. Rama Rao KV, Jayakumar AR, Tong X, Curtis KM, Norenberg MD. Brain aquaporin-4 in experimental acute liver failure. J Neuropathol Exp Neurol. 2010;69:869–79.

170. Brück J, Görg B, Bidmon HJ, Zemtsova I, Qvartskhava N, Keitel V, Kircheis G, Häussinger D. Locomotor impairment and cerebrocortical oxidative stress in portal vein ligated rats in vivo. J Hepatol. 2011;54:251–7.

171. Llansola M, Rodrigo R, Monfort P, Montoliu C, Kosenko E, Cauli O, Piedra fi ta B, El Mlili N, Felipo V. NMDA receptors in hyperammonemia and hepatic encephalopathy. Metab Brain Dis. 2007;22:321–35.

172. Aguilar MA, Miñarro J, Felipo V. Chronic moderate hyperammonemia impairs active and passive avoidance behavior and conditional discrimination learning in rats. Exp Neurol. 2000;161:704–13.


173. Izumi Y, Izumi M, Matsukawa M, Funatsu M, Zorumski CF. Ammonia-mediated LTP inhibition: effects of NMDA receptor antagonists and L-carnitine. Neurobiol Dis. 2005;20:615–24.

174. Bruck R, Aeed H, Shirin H, Matas Z, Zaidel L, Avni Y, Halpern Z. The hydroxyl radical scavengers dimethylsulfoxide and dimethylthiourea protect rats against thioacetamide-induced fulminant hepatic failure. J Hepatol. 1999;31:27–38.

175. Guerrini VH. Effect of antioxidants on ammonia induced CNS-renal pathobiology in sheep. Free Radic Res. 1994;21:35–43.

176. Roselló DM, Balestrasse K, Coll C, Coll S, Tallis S, Gurni A, Tomaro ML, Lemberg A, Perazzo JC. Oxidative stress and hippocampus in a low-grade hepatic encephalopathy model: protective effects of curcumin. Hepatol Res. 2008;38:1148–53.

177. Subash S, Subramanian P. Morin a fl avonoid exerts antioxidant potential in chronic hyperam-monemic rats: a biochemical and histopathological study. Mol Cell Biochem. 2009;327:153–61.

178. Harrison PM, Wendon JA, Gimson AE, Alexander GJ, Williams R. Improvement by acetyl-cysteine of hemodynamics and oxygen transport in fulminant hepatic failure. N Engl J Med. 1991;324:1852–7.

179. Jones AL. Mechanism of action and value of N-acetylcysteine in the treatment of early and late acetaminophen poisoning: a critical review. J Toxicol Clin Toxicol. 1998;36:277–85.

180. Walsh TS, Hopton P, Philips BJ, Mackenzie SJ, Lee A. The effect of N-acetylcysteine on oxygen transport and uptake in patients with fulminant hepatic failure. Hepatology. 1998;27:1332–40.

181. Wendon JA, Harrison PM, Keays R, Williams R. Cerebral blood fl ow and metabolism in fulminant liver failure. Hepatology. 1994;19:1407–13.

182. Haseloff RF, Blasig IE, Meffert H, Ebert B. Hydroxyl radical scavenging and antipsoriatic activity of benzoic acid derivatives. Free Radic Biol Med. 1990;9:111–5.

183. Upreti KK, Das M, Khanna SK. Role of antioxidants and scavengers on argemone oil-induced toxicity in rats. Arch Environ Contam Toxicol. 1991;20:531–7.

184. Globus MY, Alonso O, Dietrich WD, Busto R, Ginsberg MD. Glutamate release and free radical production following brain injury: effects of posttraumatic hypothermia. J Neurochem. 1995;65:1704–11.


Keywords Natural benzodiazepine • Benzodiazepine receptor • Benzodiazepine agonist • Hepatic encephalopathy • Gamma-aminobutyric acid • Benzodiazepine antagonist • Flumazenil

Benzodiazepine Ligands and GABA-Mediated Inhibitory Neurotransmission

The GABAA/Benzodiazepine Receptor Complex

Benzodiazepine (BZ) receptor ligands comprise a diverse class of compounds that include pharmaceutical BZs. These ligands bind to central BZ receptors, which are an integral component of the GABA

A /benzodiazepine receptor supramolecular

complex in synaptic neural membranes within the central nervous system. The other components of this complex are a receptor for GABA (the GABA

A receptor) and a

chloride channel (ionophore) [ 1, 2 ] (Fig. 6.1 ). Central BZ receptors are distinct from peripheral BZ receptors, which are located on mitochondrial outer membranes in nonneuronal tissues [ 3 ] . After its release from presynaptic neurons, GABA binds to GABA

A receptors on postsynaptic neurons. This binding triggers the opening of

the chloride channel, which allows passage of chloride ions into the neuron and results in hyperpolarization of its surface membrane. These events are the basis of

E. A. Jones, MD, DSc Winchester, Hampshire, UK

K. D. Mullen, MD, FRCPI (�) Department of Internal Medicine, Division of Gastroenterology , Metrohealth Medical Center , 2500 Metrohealth Drive , Cleveland , OH 44109 , USA e-mail: [email protected]

Chapter 6 The Role of Natural Benzodiazepines Receptor Ligands in Hepatic Encephalopathy

E. Anthony Jones and Kevin D. Mullen

72 E.A. Jones and K.D. Mullen

GABA-mediated inhibitory neurotransmission [ 4 ] . Gating of the chloride channel by the GABA

A receptor is allosterically modulated by the central BZ receptor,

which may increase or decrease the ef fi cacy of GABA-gated chloride conductance, depending on the nature of ligands occupying the BZ receptor [ 5– 7 ] .

The Spectrum on Intrinsic Activities of BZ Receptor Ligands

Three main classes of BZ receptor ligands are recognized: agonists, inverse agonists, and antagonists. Full agonists include the classical pharmaceutical 1,4-substituted BZs, such as diazepam. Occupation of the BZ receptor by an agonist induces con-formational changes in the receptor that increase the af fi nity of GABA for its recep-tor and, consequently, the frequency of GABA-gated chloride channel openings [ 8 ] .

Picrotoxinsite

ClosedCl–

OpenCl–

GABA receptor

BicucullineMuscimol

GABABarbiturates Benzodiazepine ligands

O

C

–O High Affinity

Outside

Inside

BZ receptor

BZ receptorCH2

CH2

N+

H2

CH2

Chloridechannel

Fig. 6.1 Diagrammatic representation of the GABAA/benzodiazepine (BZ) chloride ionophore supramolecular receptor complex in the surface membrane of a postsynaptic neuron. There are three components to these complexes: chloride channels, GABAA receptors, and central BZ receptors. The complex is depicted in the inactivated state with the chloride cannel closed. Activation of the complex with associated conformational changes. Opening of the chloride channel occurs in response to the binding of GABA to its receptor and this phenomenon is potentiated if a BZ agonist binds to the BZ receptor. Passage of chloride from the synaptic cleft to the interior of the neuron, as a consequence of opening of the chloride channel, is associated with hyperpolarization of the neural membrane. These phenomena are the basis of GABAergic inhibitory neurotransmission

736 The Role of Natural Benzodiazepines Receptor Ligands…

The resulting increase in GABAergic tone is the molecular basis of the ability of BZ agonists, including pharmaceutical BZs, to decrease anxiety, muscle tone, and vigilance and to mediate amnesia, sedation, and anticonvulsant effects [ 1, 2 ] . The effects of BZ agonist-induced augmentation of GABAergic tone include decreased consciousness and impaired motor function [ 1, 2 ] , which are two of the major manifestations of the syndrome of hepatic encephalopathy (HE) [ 9 ] . In contrast, full inverse agonists, such as beta carbolines (e.g., methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM)), induce conformational changes in the BZ receptor that decrease the synaptic response to GABA and, consequently, reduce GABAergic tone. The pharmacological effects of inverse agonists can be regarded as opposite to those of agonists and include anxiety, increased muscle tension, and proconvulsant and convulsant effects. Other BZ receptor ligands include partial agonists and partial inverse agonists. Pure antagonists have minimal (agonist or inverse agonist) intrinsic activity and, consequently, when occupying central BZ receptors, do not alter neuronal electrical activity, neuronal responsiveness to GABA, or behavior over a wide range of concentrations in normal animals. Antagonists, however, competitively antagonize the binding of other BZ receptor ligands. Consequently, antagonists tend to normalize changes in GABAergic tone induced by agonists or inverse agonists [ 5– 7, 10 ] . Thus, the intrinsic activities of different BZ receptor ligands are diverse; they can be classi fi ed with respect to their placement on a continuum or spectrum of intrinsic activities [ 5– 7, 10– 12 ] (Fig. 6.2 ). The properties of a pure antagonist would place it at the central (GABA neutral) point of this spectrum. However, many compounds classi fi ed in the central region, which have weak partial agonist or weak partial inverse agonist properties, act predominantly as antagonists [ 5– 7, 11 ] .

Origin of the Concept of a Role for BZ Receptor Ligands in HE

GABAergic Tone and HE

That increased GABAergic tone may contribute to HE was fi rst suggested in the early 1980s, when the abnormal patterns of visual evoked potentials associated with HE in animal models were shown to be similar to those induced in normal animals by administering drugs which induce augmentation of GABAergic tone, such as pentobarbital [ 13– 15 ] . Subsequently, other fi ndings also provided support for the concept that increased GABAergic tone contributes to the manifestations of HE [ 16 ] .

BZ Receptor Antagonism and HE

If augmentation of GABAergic tone induced by BZ receptor agonist ligands contributes to HE, then, theoretically, pharmacologically induced displace-ment of such ligands from central BZ receptors might induce an amelioration of HE.


This concept was originally expressed in 1984 by Anderson: “If there exists an endogenous modulator of the BZ receptor (in HE) that functions in an agonistic manner then blocking its action with an antagonist should remove this tonic facilitation and indirectly decrease GABAergic tone” and, consequently, decrease the severity of HE [ 17 ] . Subsequently, when the fi rst prototypic benzodiazepine receptor antag-onist became available for experimental use in patients, Bansky postulated in 1985 that: “since BZs stimulate the neuroinhibitory effect of GABA, a BZ antagonist might improve the level of consciousness and EEG appearing in patients with hepatic coma” [ 18 ] . This prediction was initially supported in the mid-1980s by the fi rst report of reversal of CNS changes in a rat model of HE by a BZ antagonist (CGS-8216) [ 19 ] and by anecdotal reports of ameliorations of hepatic coma in patients with cirrhosis or fulminant hepatic failure (FHF) following the intravenous administration of the newly characterized BZ receptor antagonist, Ro 15-1788 [ 18, 20 ] , i.e., fl umazenil [ 10 ] . Thus, by the late 1980s there was a basis for postulat-ing that BZ receptor agonist ligands may be involved in the mediation of HE [ 21 ] . However, it should be noted that, if the action of such ligands is a mechanism that contributes to increased GABAergic tone in HE, this mechanism would appear to

AnxiogenicIncreased muscle tension

ProconvulsantConvulsant

No effect AnxiolyticMyorelaxant

AmnesticDecreased vigilance

HypnoticAnticonvulsant

0

DMCM

Ro 15-4523

Ro 14-7437

DiazepamTriazolamMidazolam

Flumazenil(Ro 15-1788)

Ro 15-3505

Incr

ease

Dec

reas

e

Cu

mu

lati

ve U

se o

f T

reat

men

tFull Inverse

AgonistPartial Inverse

Agonist AntagonistPartial

AgonistFull

Agonist

Fig. 6.2 The spectrum of intrinsic activities mediated by central BZ receptor ligands when they binding to central BZ receptors. Full agonist ligands, including pharmaceutical BZs, increase GABAergic tone. In contrast, full inverse agonists, such as DMCM, decrease GABAergic tone. A pure BZ antagonist, such as Ro 14-7437, has no intrinsic activity; thus on binding to central BZ receptors it neither increases nor decreases GABAergic tone. Consequently, such a ligand is classi fi ed at the GABA-neutral mid-point on the spectrum. Flumazenil (Ro 15-1788) is classi fi ed as a weak partial agonist, and Ro 15-4513 and Ro 15-3505 (sarmazenil) as partial inverse agonists


be only one of several mechanisms that have been implicated in contributing to increased GABAergic tone in HE [ 16 ] .

To evaluate the validity of the hypothesis that central BZ receptor agonist ligands contribute to HE, it became necessary (1) to adopt a critical approach to evaluating the validity of quantitative methods designed to measure such ligands; (2) to obtain measurements of the concentrations of such ligands in animals and humans in the presence and absence of HE, and to determine whether such concentrations corre-late with the severity of HE; (3) to assess potential sources of nonpharmaceutical BZ receptor ligand activity in vivo in the presence and absence of HE; and, fi nally, (4) to interpret results of studies of the effects of BZ receptor ligands with different intrinsic activities on the manifestations of HE.

Some Issues Relating to Measurements of BZ Receptor Ligands

Detection and measurement of BZs in biological specimens are dependent on the type of initial extraction procedure applied. BZs are both lipophylic and highly protein bound [ 22 ] . Failure to make proper allowance for these properties is likely to lead to major inaccuracies in their detection and measurement. Standardized laboratory or toxicological procedures, such as deproteinization, may affect the detection of BZs unpredictably. Furthermore, a major problem with most commer-cially available toxicology assays for BZs is the unknown cross reactivity of the antibenzodiazepine antibody with heterogenous BZ ligands [ 23 ] .

Many compounds may contribute to BZ activity found in blood or other tissues. Indeed, it is possible that a large proportion of putative BZ ligands that may be pres-ent in biological systems could be novel compounds [ 22 ] . Distinguishing accurately between BZ activity due to occult ingestion of pharmaceutical BZs and that attribut-able to nonpharmaceutical BZs is a recurrent and important analytical challenge.

Major dif fi culties have been encountered in identifying all of the individual BZ compounds responsible for BZ activity detected in biological specimens. While minute quantities of known BZs can be measured accurately by gas chromatography/mass spectrometry techniques using specimens of conventional size, the quantities of material available after extensive puri fi cation procedures may be insuf fi cient for accurate quantitation of novel BZ compounds. Moreover, in applying the radioreceptor assay, problems in quantitation arise as a consequence of the differing avidity/af fi nity of individual BZs and the BZ (e.g., diazepam) used as a calibration standard. For example, the absolute amounts of compounds with high af fi nities for BZ receptors (e.g., picomolar) compared to that of diazepam (low nanomolar) are overestimated considerably by the radioreceptor assay when diazepam is used as the standard. The opposite is the case for compounds with low af fi nities for BZ receptors. Using samples of conventional size, many BZ compounds may tend to disappear during puri fi cation procedures. Consequently, it may be dif fi cult to obtain blood or tissue samples of suf fi cient size to provide enough material for de fi nitive identi fi cation of many BZ compounds.


In the subsequent discussion of studies in which concentrations of BZs were measured in humans or animals in the presence or absence of HE, the speci fi c methods used are mentioned only to draw attention to a particular methodological issue or to illuminate a particular point in the text.

Concentrations of BZs in Animals and Humans with and Without HE

As the brain is the end organ of HE, the optimal site for measuring the concentrations of BZ ligands in studies of their potential role in HE would be the brain. However, it would also be relevant to make measurements in cerebrospinal fl uid or plasma. In general, BZ receptor ligands are not only lipid soluble but they also rapidly traverse the blood–brain barrier. Thus, BZ receptor ligands present in increased concentrations in plasma could readily contribute to the manifestations of HE [ 22 ] . Factors that would tend to result in increased concentrations of free BZs in plasma in liver failure would include low protein binding potentiated by decreased hepatic synthesis of albumin, decreased hepatic metabolism, and increased portal-systemic shunting [ 24 ] .

Further evidence supporting a relationship between BZs and HE was provided by the demonstration of a BZ receptor binding substance in the cerebrospinal fl uid of a rabbit model of HE as a result of applying an assay to measure BZs directly [ 25– 27 ] . This study was followed by the demonstration of BZ activity in body fl uids of patients with HE, in whom there was no evidence of recent ingestion of pharmaceutical BZs [ 27, 28 ] . Subsequently, activity that reversibly and competi-tively inhibited radiolabeled BZ receptor ligand binding to normal brain membranes was demonstrated in brain, plasma, and several peripheral organs of animal models of HE [ 29– 33 ] .

In an autoradiographic study, the binding of a radiolabeled BZ receptor ligand to unwashed brain sections was found to be reduced in a model of HE. This decrease could be eliminated by prewashing brain sections, indicating the presence in HE of ligands that reversibly bind to BZ receptors. In this autoradiographic study, the distribution of the BZ receptor ligands was not uniform throughout the brain [ 30 ] . In two studies, the potency of the BZ receptor binding inhibitory activity in a model of HE was enhanced by GABA [ 29, 30 ] . This phenomenon, known as a positive GABA shift, is attributable to an increase in the af fi nities of the BZ receptor ligands present and indicates that they include ligands with agonist properties [ 34– 36 ] .

High performance liquid chromatographic analysis of whole brain extracts from two animal models of HE and control animals revealed peaks of inhibitory activity with retention times similar to those of known 1,4-BZs [ 31, 33 ] . 1,4-BZs were found in normal brain, but total brain levels of these ligands were signi fi cantly greater in the models of HE [ 31, 33 ] .


Both BZ receptor binding activity and 1,4-BZ immunoreactivity were found to be increased in cerebrospinal fl uid, plasma, and urine of patients with decompen-sated cirrhosis in whom there was no evidence of ingestion of pharmaceutical BZs during the preceding 3 months [ 28, 32, 37 ] .

A study that showed predominantly unchanged levels of BZ receptor ligands in a presumed model of HE raises questions whether the animal model used adequately re fl ects the syndrome of HE in humans; it also raises issues relating to the validity of the methods used [ 38, 39 ] .

Increased levels of total BZ receptor binding activity and of diazepam and N -desmethyldiazepam have been demonstrated in about 60% of brains obtained at autopsy from patients who died from acetaminophen-induced FHF [ 40, 41 ] .

Total brain levels of BZ receptor ligands are insuf fi cient to account for all of the manifestations of HE [ 22, 31, 33 ] . Brain levels of total BZ receptor ligands are lower in animal models of FHF than in humans with FHF. Speci fi cally, the mean brain level of total BZ receptor ligands in rats with thioacetamide-induced FHF was 71 ng/g [ 31 ] , and in rabbits with galactosamine-induced FHF it was 21 ng/g [ 33 ] ; in contrast, the corresponding mean for humans with acetaminophen-induced FHF was 300 ng/g [ 40 ] .

Brain levels of total BZ receptor ligands were not elevated in rats with a porta-caval shunt [ 32 ] , but the rat with a portacaval shunt does not ful fi ll criteria that are necessary for a model of HE [ 42 ] .

Brain levels of BZ receptor ligands in an animal model of FHF [ 43 ] and plasma levels of BZ receptor ligands in humans with FHF [ 44 ] or decompensated cirrhosis [ 28 ] have been shown to correlate directly with the severity of HE.

Nomenclature and the Nature of BZ Receptor Ligands in HE

Only a proportion of the BZ receptor binding activity present in the brain in animal models of FHF and humans with FHF has been shown to be due to the presence of classical 1,4-BZs; 17–55% of this activity appears to be due to diazepam and N -desmethyldiazepam [ 31, 33, 40 ] . The chemical and functional nature (agonist, antagonist, inverse agonist) of a large proportion of the BZ receptor ligands present in the brain in HE is currently unknown [ 22, 31, 40 ] . The presence of antagonist ligands in HE might in fl uence the responsiveness of the encephalopathy to an administered antagonist, and the presence of ligands with inverse agonist properties would tend to counteract the effects of agonist ligands on the encephalopathy.

Originally, when BZ activity was fi rst found in animals and humans with HE, the term “endogenous” BZs was used [ 21, 28 ] . Endogenous BZs are distinct from endozepines and diazepine-binding inhibitor, which were discovered at about the same time [ 45– 48 ] . Increased levels of diazepam-binding inhibitor, a BZ receptor ligand with partial inverse agonist properties, have been demonstrated in the cerebrospinal fl uid of cirrhotic patients with HE [ 49 ] . However, the relevance of endozepines to


the pathogenesis of HE is uncertain. High molecular weight endozepines and their cleavage products are not detected by the radioreceptor assay for BZs [ 50 ] . Application of the word “endogenous” to BZs would appear to imply that BZs are synthesized by mammalian cells. However, evidence that mammalian cells can synthesize BZs is lacking. While the thyroid gland can halogenate a tyrosine ring, there is considerable uncertainty whether any mammalian tissue can halogenate (e.g., 7-chlorination) the A ring of a 1,4-BZ [ 51 ] , an essential step for the biosynthesis of BZs. If the BZs present in patients with HE come from food or are synthesized and released within the gut lumen, it would be inappropriate to classify them as endogenous. Thus, it is currently uncertain whether the term “endogenous” is appropriate for the BZs present in patients with HE. Until the source of the BZs present in patients with HE has been clari fi ed unequivocally, it is suggested that an appropriate interim term for these compounds be “natural” BZs.

Possible Sources of Natural BZs in HE

The origin of increased BZ receptor ligand levels in HE is uncertain [ 52 ] . Possibilities include the food cycle [ 53– 56 ] , precursor compounds in the food cycle, direct synthesis or synthesis of precursors by intestinal bacteria [ 57 ] , and occult inges-tion of pharmaceutical BZs. BZs, including diazepam and N -desmethyldiazepam, have been found in low concentrations in a variety of human tissues from subjects without liver disease [ 53– 55, 58– 61 ] , and in foods such as wheat and potatoes [ 55, 56 ] , milk [ 53 ] , soy, beans, rice, and mushrooms [ 54 ] . BZ levels have been shown to increase fi ve- to eightfold during germination of wheat and potatoes, suggesting that biosynthesis of BZs occurs in these plants [ 56 ] . Even if subnormal metabolism of BZ receptor ligands by a failing liver is assumed, the concentra-tions of preformed BZ receptor ligands in food seem to be too low to account for the levels of BZ receptor ligands found in animal models of HE and patients with HE. The term natural BZs has been applied to BZs found in the food cycle that are not attributable to industrial contamination with BZs [ 53– 56 ] . Most of these BZs that have been identi fi ed are identical to commercially synthesized BZs, such as lorazepam and N -desmethyldiazepam. Commercial BZs, which are clearly an important potential source of BZs in patients with HE, cannot account for the elevated levels of BZs found in most patients with HE. Brains of human subjects without liver disease, which were preserved at a time before BZs had become commercially available, have been shown to contain 1,4-BZs [ 51, 58 ] . One pos-sible source for such natural BZs might be ingested BZ precursors, which are converted into biologically active BZs in the gut or after absorption. Diazepam and N -desmethyldiazepam may be synthesized by prokaryotes [ 62 ] . Finally, gut bacteria have been shown to be a potential source of precursors of BZ receptor ligands in a rat model of HE [ 57 ] .


Effects of BZ Receptor Antagonist Ligands on HE

Flumazenil

The 1,4-imidazobenzodiazepine, fl umazenil (Ro 15-1788), binds competitively, reversibly, and with high speci fi city and high af fi nity to central BZ receptors [ 10, 63 ] , at which it exhibits very weak, dose-dependent, partial agonist effects [ 64 ] . Its location on the spectrum of intrinsic activities of BZ receptor ligands, slightly on the agonist side of the central, GABA-neutral, point [ 12 ] (Fig. 6.2 ), implies that it acts predomi-nantly as a BZ receptor antagonist. Furthermore, its precise location on this spectrum contributes signi fi cantly to its safety pro fi le, since it is devoid of the convulsive potential associated with ligands that possess inverse agonist intrinsic activity. Thus, an overdose of fl umazenil is likely to induce only weak diazepam-like effects, such as mild sedation [ 10 ] . Flumazenil antagonizes the actions of BZs, beta-carbolines, and other compounds with signi fi cant intrinsic activity that bind directly to central BZ receptors. It blocks all of the speci fi c behavioral and pharmacological effects of classical BZ receptor agonists, such as diazepam [ 10, 63 ] .

The ef fi cacy of fl umazenil depends not only on its precise placement on the spectrum of intrinsic activities of BZ receptor ligands (Fig. 6.2 ), but also on its occupancy of central BZ receptors and its rate of metabolism [ 10, 22, 24, 63, 65 ] . Plasma clearance of fl umazenil is rapid in normal subjects; it is slower in patients with impaired hepatocellular function [ 66 ] . Positron emission tomography after the intravenous injection of 11 C-labeled fl umazenil to normal subjects has demonstrated prompt binding of the radioligand to BZ receptors in the brain. Cerebral levels of the radio-ligand decrease with a half-life of 25–38 min, which is due to displacement rather than metabolism; the rate of decline of cerebral radioactivity may exceed that of plasma radioactivity. The radioligand is rapidly removed from BZ receptors in the brain after the intravenous administration of unlabeled fl umazenil [ 67 ] . Cerebral retention of 11 C-labeled fl umazenil is prolonged in patients with advanced hepato-cellular disease [ 68 ] , probably due to impaired hepatic metabolism of fl umazenil [ 66 ] . Only small doses of fl umazenil (e.g., 0.3–0.5 mg) administered intravenously appear to be necessary to occupy a large proportion of central BZ receptors, and, hence to mediate BZ receptor antagonist effects [ 10, 22, 63, 65, 69 ] . Doses for clinical administration as intravenous bolus injections are usually less than 2 mg.

Like many other BZ receptor ligands, fl umazenil is lipid soluble and, following its intravenous administration, it rapidly traverses the blood–brain barrier and gains access to central BZ receptors. Its effects become apparent less than 4 min after intravenous administration [ 10, 22, 63 ] . The drug also mediates BZ antagonist effects when given by mouth, but its oral bioavailability is low mainly due to its high fi rst-pass hepatic extraction [ 10, 22, 24 ] . Thus, fl umazenil is effective at lower doses after intravenous than oral administration. Its duration of action, which lasts 2–3 h in man after an intravenous bolus injection [ 10 ] , is dependent on its rapid rate of metabolism. In patients with impaired hepatocellular function, its slower rate of metabolism [ 66 ] may contribute to a more sustained action.


Flumazenil for parenteral use is currently the only BZ receptor antagonist preparation approved for clinical use.

Uncontrolled Studies of Flumazenil in Humans

Normal Subjects

When low doses of fl umazenil (1–5 mg IV or 30 mg orally) were administered to normal subjects, phenomena indicative of central neuronal activation were observed, including anxiety, autonomic arousal, sleep disturbances, and increased neuronal electrical activity [ 70 ] . At higher doses (25 mg IV or 100–400 mg orally) fl umazenil exhibited agonist properties; speci fi cally, it acted as an anticonvulsant, impaired motor function, suppressed neuronal electrical activity, and induced mild sedation [ 24, 71 ] . Because fl umazenil is devoid of inverse agonist intrinsic activity [ 64 ] , the anxiogenic and CNS-activating effects of low doses can be explained by postulating that it displaces natural BZ receptor ligands with agonist properties from central BZ receptors, thereby inducing activation of the CNS as a consequence of neuronal disinhibition [ 70 ] . This interpretation of the effects of low doses of fl umazenil in normal subjects is consistent with the existence of low levels of natural BZ agonist ligands in the brain under physiological conditions.

Patients with HE

Anecdotal reports have described clinical and electrophysiological ameliorations of HE following intravenous bolus injections of fl umazenil to patients with FHF or cirrhosis [ 22, 72, 73 ] . These observations, although uncontrolled, were usually made in patients with stable clinical and electrophysiological indices of HE before drug administration [ 72, 73 ] , and the ameliorations that occurred were often repro-ducible [ 22 ] . Thus, the responses seemed to be genuine, especially as basic research on the pathogenesis of HE [ 22, 65, 74 ] provided a logical explanation for fl umazenil-induced ameliorations of HE. These reports have documented certain characteristics of ameliorations of HE following intravenous bolus injections of fl umazenil: (1) readily detectable ameliorations are inconsistent, occurring in about 60% of patients with HE secondary to either acute (FHF) or chronic liver disease (cirrhosis) [ 10, 22, 65, 74 ] ; (2) responses occur rapidly, usually within 4 min of drug adminis-tration [ 72, 73 ] , the range being 28 s to 30 min [ 22, 75 ] ; such responses are unlikely to be spontaneous, but are consistent with fl umazenil rapidly crossing the blood–brain barrier and gaining access to central BZ receptors [ 10, 63 ] ; (3) substantial ameliora-tions of HE occur after low doses, e.g., 0.3–0.5 mg, supporting the concept that only small amounts of the drug are necessary to occupy a large proportion of central BZ receptors and, hence, mediate BZ antagonist effects [ 22, 65, 69 ] ; (4) consistent with its rapid rate of catabolism, which includes hepatic metabolism and the action of


plasma esterases [ 10, 22, 24 ] , ameliorations of HE have a short duration (0.6–4 h) [ 22, 72, 73 ] ; and (5) ameliorations are usually partial (e.g., one to two of the classical clinical stages of HE [ 9 ] ); typically only some neurologic de fi cits are reversed and improvements in motor function tend to be limited, but, occasionally, a patient becomes conscious and starts talking with dramatic rapidity [ 22, 72, 73, 75 ] .

In addition, an intravenous infusion of fl umazenil (0.2 mg) has been shown to improve the cognitive component of a reaction time task in patients with subclinical HE [ 9, 76 ] . Furthermore, administration of fl umazenil to patients in hepatic coma was shown, not only to induce clinical ameliorations of encephalopathy, but also to induce improvements in associated abnormal patterns of visual evoked potentials [ 75 ] , which are an index of brain electrophysiologic function that does not depend on cognitive function. In contrast, fl umazenil did not induce an improvement in visual event-related potentials, an index of cognitive function, in cirrhotic patients without overt encephalopathy [ 77 ] , but the patients studied were not shown to fi ll criteria necessary for a diagnosis of subclinical HE [ 9 ] .

In contrast to the intravenous route of administration, orally administered fl umazenil, 25 mg twice daily, has been reported to induce consistently a complete and sustained amelioration of intractable portal-systemic encephalopathy in a middle-aged woman. While taking the drug, a normal or supranormal dietary intake of protein was well tolerated [ 78 ] . Furthermore, 25–40 min after administration of each dose of fl umazenil, this patient regularly experienced a feeling of anxiety, which subsided after 30–60 min [ 78 ] . This observation can be explained by postulating that the drug displaced agonist ligands from central BZ receptors, thereby precipitating a clinically overt manifestation of neuronal disinhibition.

Controlled Studies of Flumazenil

Animal Models of HE

Flumazenil markedly excited the spontaneous neuronal activity of isolated Purkinje neurons from the cerebellum of a rabbit model of FHF, but partially suppressed the spontaneous activity of the same neurons from control animals [ 64 ] . The effect of fl umazenil on the control neurons is a direct demonstration of its very weak partial agonist intrinsic activity, whereas its effect on neurons from the model of HE can be explained by their disinhibition as a consequence of displacement of ligands with agonist intrinsic activity from central BZ receptors.

Controlled data on the effects of fl umazenil on behavioral and electrophysiologi-cal indices of HE have been generated using animal models of FHF. Both positive [ 79, 80 ] and negative [ 81– 85 ] results have been obtained. In the light of extensive positive fi ndings in humans [ 22, 86 ] , negative results must always raise concerns about the adequacy of the animal model studied. For example, the syndrome of acute hepatic ischemia in animals [ 81, 82, 87 ] differs in important respects from the typical syndrome of FHF in humans [ 9, 88 ] , including the probability that


factors other than uncomplicated hepatocellular failure contribute signi fi cantly to encephalopathy at an early stage in the ischemic model; such factors may include other metabolic encephalopathies (e.g., hypoglycemia) and cerebral edema. Other potential explanations for a lack of amelioration of encephalopathy following administration of fl umazenil to animal models of HE include pharmacokinetic factors (e.g., effects of dissolving the drug in gum arabic as vehicle), and, possibly, the weak partial agonist properties of the drug. In two animal studies in which positive data were generated, at least three factors enhance the signi fi cance of the results: (1) the models used had been extensively characterized and validated [ 80, 89, 90 ] ; (2) increased levels of natural BZs in the brain had been demonstrated in both of the models [ 31, 33 ] ; and (3) the animals studied had not been exposed to pharmaceutical BZs.

Patients with HE

Thirteen randomized controlled trials of the effects of fl umazenil on HE complicating cirrhosis have been reviewed by Als-Nielsen et al. [ 91 ] . The number of patients entered into these trials was 805. All of them were double blind and assessed the effects of fl umazenil vs. those of placebo. Eight of the trials had a crossover design. Flumazenil administration was associated with a signi fi cant increase in short-term ameliorations of HE, predominantly in patients who had a favorable outcome. Certain issues of concern may be applicable to the design of some of the trials included in this review; these include: (1) poorly de fi ned criteria for making a diag-nosis of HE; (2) selection of suboptimal stages of encephalopathy as inclusion criteria; (3) failure to ensure adequately that patients had not recently received pharmaceutical BZs; and (4) inappropriate interpretation of screening tests for BZs in body fl uids.

Comments on Studies of Flumazenil in HE

None of the traditional treatments for HE, such as lactulose and neomycin, induce such substantial ameliorations of HE, so rapidly and so frequently, as those that have been documented to occur after administering fl umazenil intravenously [ 22, 72, 73 ] . This fi nding highlights that a fundamental shift of approach to treating HE has been initiated [ 92, 93 ] . Traditional approaches have typically involved administering agents that are believed to decrease formation and/or absorption of encephalopathogenic substances in the colon. A more ef fi cacious approach may be to administer therapies that have the potential of directly reversing relevant pathophysiological mechanisms in the brain, the end organ of HE [ 92, 93 ] . The fi rst example of such a new approach to treating HE is the administration of fl umazenil, which acts directly as an antagonist at central BZ receptors in the brain.

Although subject to the limitations inherent in all human autopsy studies, the percentage of patients with FHF in whom brain levels of BZ receptor ligands were


found to be increased at autopsy was found to correspond closely to the percentage of patients with FHF in whom ameliorations of HE occur following a bolus intrave-nous injection of fl umazenil. This fi nding is consistent with elevated brain levels of BZ receptor ligands being a necessary prerequisite for a fl umazenil-induced ame-lioration of HE to occur [ 22, 40, 41, 65, 74, 94 ] . Because of the speci fi city of the action of fl umazenil for central BZ receptors and its very weak partial agonist properties at this receptor, the most logical explanation for a fl umazenil-induced amelioration of HE is that the drug reduces increased GABAergic tone that occurs in HE [ 16 ] by displacing natural agonist ligands from central BZ receptors (Fig. 6.1 ). The ef fi cacy of fl umazenil in ameliorating HE implies that levels of BZ agonist ligands in the brain in liver failure are suf fi ciently high to mediate at least some of the behavioral manifestations of HE. Flumazenil-induced displacement of BZ ago-nist ligands from central BZ receptors would lead to a disinhibition of neurons and, hence, an increase in their spontaneous activity. Furthermore, the transient anxiety that occurred consistently soon after the oral administration of fl umazenil to a patient with intractable chronic portal-systemic encephalopathy can be explained by the same mechanism [ 78 ] . The available data on the effects of fl umazenil suggest that augmentation of GABAergic tone induced by natural BZ ligands with agonist properties contributes substantially to the manifestations of HE in a majority of patients with liver failure. Speci fi cally, improvements of one to two of the classical clinical stages of HE have been frequently documented following fl umazenil admin-istration [ 9, 10, 22, 72, 73 ] . The ef fi cacy of fl umazenil in reversing manifestations of HE may be related primarily to the degree to which concentrations of BZ agonists are elevated in the brain. Thus, the apparently greater ef fi cacy of fl umazenil in amelio-rating HE in humans than in animals with FHF may be due largely to the much higher brain levels of BZs in some patients with FHF than in animals with FHF [ 22, 31, 33, 40 ] . The proportions of patients with HE who respond to fl umazenil are similar (about 60%) for those with both FHF and cirrhosis [ 65, 74 ] , suggesting that natural BZs contribute to HE in both of these clinical settings. Thus, HE due to FHF and HE complicating cirrhosis do not appear to be completely distinct entities. Whether the response of a patient with HE to fl umazenil is an index of prognosis [ 74, 91, 95 ] is currently uncertain.

While an amelioration of HE associated with administration of fl umazenil provides strong evidence that BZ agonists contribute to the manifestations of HE, it does not follow that a lack of improvement in encephalopathy in a model of liver failure [ 81– 85 ] or a patient with liver disease following administration of fl umazenil provides evidence against a contribution of BZ agonists to the manifestations of HE. Such a lack of an overt effect of fl umazenil may occur if manifestations of enceph-alopathy are compounded by the presence of encephalopathogenic factors other than those attributable to uncomplicated hepatocellular failure alone, for example, cerebral edema, increased intracranial pressure, hypoxic brain damage, and hypoglyce-mia. Thus, as FHF or end-stage chronic liver disease progresses to the agonal stages of liver failure many factors, in addition to those responsible for HE, may contribute to an encephalopathic state [ 9, 88 ] . Furthermore, whenever an encephalopathy consid-ered to be HE does not respond to fl umazenil, it is important not only to determine


if manifestations of HE are being masked by other encephalopathies, but also to question whether the diagnosis of HE is correct. A con fi dent diagnosis of HE depends on clinical judgment and experience. There is no simple test to con fi rm a diagnosis of HE [ 9, 88 ] . Features of patients with liver disease that may be associated with a lack of response of HE to fl umazenil include stage IV encephalopathy, cerebral edema, and early death [ 22, 91, 95 ] .

The observations that fl umazenil rarely reverses HE completely may be interpreted as suggesting that pathogenic mechanisms other than BZ agonist-induced augmen-tation of GABAergic tone also contribute to HE. For example, mechanisms not involving BZ receptor ligands may mediate increased GABAergic tone in HE [ 16 ] . Clearly, fl umazenil-induced ameliorations of HE cannot be explained by the weak agonist intrinsic activity of the drug. The data on the effects of fl umazenil on HE in man may underestimate the magnitude of the contribution of natural BZs to HE for the following reasons: (1) other complicating metabolic disturbances may have masked the contribution of natural BZ agonist ligands to encephalopathy [ 10, 22, 65, 74 ] ; (2) the design of published controlled trials of fl umazenil in patients with HE may not have been optimal; and (3) fl umazenil, because of its weak partial agonist intrinsic activity [ 64 ] , does not have the properties of a pure BZ antagonist [ 94 ] .

Whenever the effects of fl umazenil on HE are being assessed, it is essential to exclude recent ingestion of pharmaceutical BZs [ 28, 96 ] . In this context, it may not be easy to ascertain whether a patient with liver disease has taken pharmaceutical BZs recently, as several natural BZs and pharmaceutical BZs appear to be identical [ 27 ] . Clearly, it is inappropriate in an assessment of the effects of fl umazenil on HE to exclude patients in whom a screening test for BZs in blood is positive [ 97, 98 ] , as such positive tests may be attributable to the consequences of liver failure [ 22 ] . On the contrary, a positive assay for BZs in a patient with liver failure and HE may indicate that therapy with fl umazenil is likely to be effective.

BZ Receptor Ligands Other than Flumazenil

Exposure to the BZ receptor antagonist Ro 14-7437 markedly increased the sponta-neous activity of isolated Purkinje neurons from a rabbit model of FHF, but had no effect on the spontaneous activity of control neurons (Fig. 6.3 ). The latter observa-tion is compatible with Ro 14-7437 being classi fi ed as a pure BZ receptor antago-nist with minimal agonist or inverse agonist intrinsic activity (Fig. 6.2 ). Furthermore, incubation of Purkinje neurons from the model of HE, but not control neurons, with subthreshold concentrations of Ro 14-7437 reduced their sensitivity to the neuroin-hibitory effect of the GABAmimetic, muscimol. In contrast, there was no difference in sensitivity between neurons from the model of HE and control neurons to the depressant actions of the alpha-adrenoceptor agonist, phenylephrine [ 64 ] . These observations demonstrate a differential responsiveness of neurons from a model of HE to ligands that interact with the GABA

A -BZ receptor complex and provide

further support for reversible binding of BZ ligands with agonist properties to BZ receptors on the GABA

A receptor complex in HE.


Two other compounds that have been classi fi ed as BZ receptor antagonists with weak partial inverse agonist properties, Ro 15-4513 and Ro 15-3505 (sarmazenil) [ 5– 7, 10, 11 ] (Fig. 6.2 ), have been administered to animal models of FHF. Both compounds were shown to induce robust behavioral and electrophysiological ameliorations of encephalopathy in the models studied [ 80, 82, 83, 85 ] . In one study these BZ receptor ligands were shown not to improve the neurological status of control animals with uremic encephalopathy [ 83 ] . Theoretically, improvements of HE induced by these agents could arise as a consequence of either or both of their two well-known properties: (1) their ability to act as antagonists and displace BZ agonist ligands from central BZ receptors; and (2) their ability to induce an analeptic effect as a consequence of their weak partial inverse agonist intrinsic activity at central BZ receptors. The ameliorations of HE induced by these agents did not appear to be predominantly due to their partial inverse agonist properties for two reasons: (1) the doses of these drugs that induced ameliorations of HE did not mediate any unequivocal behavioral or electrophysiological effects in normal animals [ 80, 82, 83 ] ; and (2) the administration of subconvulsive doses of the full inverse agonist, DMCM, to a rat model of HE did not ef fi caciously reverse HE, but induced a preconvulsive state [ 80 ] , whereas the ameliorations of HE induced by Ro 15-4513 and Ro 15-3505 were characterized by normal coordinated motor activity and exploratory behavior in the absence of any clearly recognizable preconvulsive state [ 80, 82, 83 ] . Furthermore, in one of the studies in which positive data were obtained using fl umazenil, behavioral and electrophysiological ameliorations of HE were more robust following the administration of Ro 15-4513 than fl umazenil [ 80 ] .

80

100

120

140

60

40

20

–20

–40

7 6 5

–Log Drug, [M]

0

Ch

ang

e in

Sp

on

tan

eou

s F

irin

gR

ate,

(%

of

Co

ntr

ol)

Fig. 6.3 Concentration–response curves for the effects of the pure benzodiazepine receptor antagonist, Ro 14-7437, on the spontaneous activity of Purkinje neurons from control rabbits ( closed tri-angles ) and rabbits with hepatic encephalopathy ( open triangles ). Data are means ± SEM. Ro 14-7437 (0.5–7.5 m M) had no effect on the activity of neurons from control rabbits, but elicited a robust increase in the spontaneous activity of neurons from rabbits with hepatic encephalopathy. The concentration of drug that increased neuronal activity by 50% (EC

50 ) was 1.43 m M. The increased

spontaneous activity of neurons from rabbits with hepatic encephalopathy can be explained by their disinhibition as a consequence of displacement of ligands with agonist properties from central BZ receptors


Nevertheless, the possibility that a component of the observed ameliorations of HE following administration of Ro 15-4513 or Ro 15-3505 was due to the inverse agonist properties of the administered compound, and was therefore independent of natural BZ receptor agonist ligands, cannot be excluded.

A third less well-known property of BZ receptor antagonists with weak partial inverse agonist properties may also be relevant to the potential for these ligands to ameliorate HE. Increased brain levels of neurosteroids, such as allopregnanolone, that are positive allosteric modulators of GABA

A receptors, are known to occur in

HE and are recognized as a potential mechanism of increased GABAergic tone [ 16 ] . Allopregnanolone has been shown to potentiate GABA-induced currents in cultured hippocampal neurons. This phenomenon was attenuated by Ro 15-4513, but not by fl umazenil [ 99 ] . Thus, the bene fi cial effect of Ro 15-4513 on HE may be mediated, at least in part, by its ability to reduce the effects of certain neurosteroids on the function of the GABA neurotransmitter system.

Concluding Perspectives

Both direct and indirect evidence for an association between increased levels of BZ receptor agonists and HE have been generated and support the hypothesis that natural BZs with agonist properties contribute to the manifestations of overt and subclinical HE by potentiating the action of GABA. Mean concentrations of BZ receptor ligands in the brain in HE, when expressed in units of diazepam (or oxazepam) equivalents, are probably suf fi cient to induce subtle derangements of psychomotor function (subclinical HE) and mild sedation [ 22, 40, 50 ] , but not all of the manifes-tations of HE. Furthermore, these mean concentrations appear to be less than those induced by encephalopathogenic doses of diazepam. However, as the BZ receptor ligands present in the brain in HE may be functionally heterogenous [ 22, 31, 33, 40 ] , it may be inappropriate to make any assumption regarding their functional signi fi cance from concentrations expressed in diazepam (or oxazepam) equivalents. Furthermore, in the brain of a rabbit model of FHF, BZ receptor ligands are heterogenously distributed [ 30 ] . Thus, their concentrations in certain regions of the brain may greatly exceed their mean concentration for the whole brain. In addition, the neuroinhibitory effects of BZ receptor ligands with agonist properties, and, hence, the contribution of such ligands to HE, may be enhanced if the availability of GABA at GABA

A receptors is increased in liver failure [ 16, 22, 100, 101 ] . Indeed, increased

sensitivity of isolated Purkinje neurons from a model of HE [ 64, 102 ] and of the brain of patients with cirrhosis and impaired hepatocellular function [ 103 ] to a pharmaceutical BZ has been documented. Thus, the sensitivity of the GABA

A

receptor complex to BZ agonist ligands is increased in HE. Ideally, an assessment of the contribution of BZ receptor agonist ligands to HE

requires evaluating the responsiveness of the encephalopathy to the intravenous administration of a pure BZ receptor antagonist, which is devoid of any inverse agonist intrinsic activity and preferably, unlike fl umazenil, is also devoid of any


agonist intrinsic activity. In the management of HE, the contribution of natural BZs to the encephalopathy could theoretically be completely reversed by administering a BZ receptor antagonist devoid of any intrinsic activity. If an antagonist with weak partial agonist properties, such as fl umazenil, is administered, the improvement in encephalopathy induced by the drug may represent an underestimation of the contribution of natural BZs to the encephalopathy, because potent agonist molecules would be replaced by weaker agonist molecules on BZ receptors. Conversely, if an antagonist with weak partial inverse agonist properties is administered, the resultant improvement in encephalopathy might, theoretically, overestimate the contribution of natural BZs to the encephalopathy, because any decrease in encephalopathy attributable to its partial inverse agonist properties would be independent of the presence of natural BZ receptor ligands. However, this line of reasoning has not been supported by the documented responses of animal models of FHF to certain BZ receptor antagonists with weak partial inverse agonist properties, speci fi cally Ro 15-3505 and Ro 15-4513 [ 80, 82, 83, 85 ] .

The association of increased levels of natural BZ receptor agonists with HE pro-vides a strong rationale for the use of a BZ receptor antagonist as a component of a therapeutic regimen designed to facilitate optimization of mental function in patients with HE. Such a regimen may include an intravenous infusion of a BZ receptor antagonist, which, in contrast to intravenous bolus injections, would be likely to induce a more predictable and sustained response. Two phases in the development of a new drug for treatment of HE can be recognized: phase I—demonstration that a drug of a particular class can induce an amelioration of HE; phase II—identifying a drug of that class that has optimal therapeutic properties. The effect demonstrated in phase I may not necessarily be therapeutically signi fi cant. With regard to the use of BZ receptor antagonists in the management of HE, the available data on the effects of fl umazenil on HE in humans indicate that phase I has been completed. However, it is clear from the above discussion that the properties of fl umazenil do not conform to those of an ideal BZ receptor antagonist for use in the management of HE [ 94 ] . Such a compound has not yet been identi fi ed and may not yet have been synthesized. Consequently, phase II is incomplete. The properties of such an ideal BZ receptor ligand would include: (1) slow rate of metabolism, so that its ameliorat-ing effects on HE would be sustained; (2) high af fi nity and speci fi city for central BZ receptors; (3) no toxic effects; and (4) minimal (agonist or inverse agonist) intrinsic activity, so that no phenomena attributable to intrinsic activity would be apparent after administration of a wide range of doses of potential therapeutic relevance (Fig. 6.2 ).

At this time the only BZ antagonist preparation available for clinical use is fl umazenil for parenteral administration. The impressive case study that demon-strated a complete and sustained amelioration of intractable chronic portal-systemic encephalopathy in a middle-aged woman treated with fl umazenil 25 mg orally twice daily [ 78 ] should prompt the conduct of an appropriately designed trial to assess more de fi nitively the ef fi cacy of orally administered fl umazenil in the treatment of patients with chronic portal systemic encephalopathy. A positive result in such a trial may indicate a place for a preparation of fl umazenil for oral administration in


the treatment of chronic HE on an outpatient basis. However, an oral preparation of fl umazenil has yet to be made available for such a study. Furthermore, so far BZ receptor antagonists with partial inverse agonist properties have not yet been evalu-ated in humans with HE, in part, because of concern over their assumed convulsive potential. Ro 15-3505 (sarmazenil) appears to be a weaker partial inverse agonist than Ro 15-4513 and to have a higher af fi nity for central BZ receptors than fl umazenil [ 5, 22 ] . Factors that contribute to the greater ef fi cacy of both sarmazenil and Ro 15-4513 than fl umazenil in ameliorating HE in animal models may include their higher af fi nity for central BZ receptors and different pharmacokinetic properties, rather than their partial inverse agonist properties, which were not shown to be signi fi cant in the context of inducing ameliorations of HE in animal models [ 22, 80, 82, 83, 85 ] . Extrapolation from relevant fi ndings in animal models of FHF [ 80, 82, 83, 85 ] to man may be used to justify postulating that sarmazenil may act as a BZ receptor antagonist in patients with HE without any partial inverse agonist effects becoming clinically apparent following administration of low doses that may well be ef fi cacious in ameliorating HE. Thus, although high doses of sarmazenil are considered to have convulsive potential, the safety pro fi le of low, and possibly therapeutically ef fi cacious, doses may well be suf fi ciently acceptable to permit carefully conducted clinical trials of its administration to patients with HE. Furthermore, the possibility that ameliorations of HE induced by BZ receptor antagonists with weak partial inverse agonist properties, such as Ro 15-4513, may be mediated, at least in part, by their ability to attenuate neurosteroid-induced potentiation of GABAergic tone [ 99 ] , may imply that the convulsive potential of such agents when used to treat HE is even less than may have been assumed.

There are exciting prospects for improved treatment of HE with novel BZ recep-tor antagonist ligands, if the pharmaceutical industry can be motivated to synthe-size and make available additional BZ receptor ligands with properties that are superior to those of fl umazenil, particularly with respect to their rate of metabolism and intrinsic activity. If such new ligands are generated it is important that they be made available for testing experimentally in animal models of HE and, subse-quently if indicated, in trials in humans with HE complicating both acute and chronic liver failure.

This is one of the last publications of E. Anthony Jones who died unexpectedly on January 23rd 2012. His memory will live-on in his many proteges (K.D. Mullen).

References

1. Tallman JF, Paul SM, Skolnick P, Gallager DW. Receptors for the age of anxiety: the pharmacol-ogy of benzodiazepines. Science. 1980;207:274–81.

2. Paul SM, Marangos PJ, Skolnick P. The benzodiazepine-GABA-chloride ionophore receptor complex. Common site of minor tranquilizer action. Biol Psychiatry. 1981;16:213–29.

3. Anholt RR, Pedersen PL, De Souza EB, Snyder SH. The peripheral-type benzodiazepine receptor. Localization to the mitochondrial outer membrane. J Biol Chem. 1986;261:576–83.


4. Skolnick P, Paul SM. The benzodiazepine/GABA receptor chloride channel complex. ISI Atlas Sci Pharmacol. 1988;2:19–22.

5. Haefely W, Kyburaz E, Gerecke M, Mohler H. Recent advances in the molecular pharmacology of benzodiazepine receptors and in the structure-activity relationships if their agonists and antagonists. Adv Drug Res. 1985;14:165–322.

6. Haefely WE, Martin JR, Richards JG, Schoch P. The multiplicity of actions of benzodiaz-epine receptor ligands. Can J Psychiatry. 1993;38 Suppl 4:S102.

7. Haefely WE. Allosteric modulation of the GABAA receptor channel: a mechanism for interaction with a multitude of central nervous system functions. In: Mohler H, De Prada M, editors. The challenge of neuropharmacology. A Tribute to the Memory of Willy Haefely. Basel: Editiones Roche; 1994. p. 15–39.

8. Study RE, Barker JL. Diazepam and (-)-pentobarbital: fl uctuation analysis reveals different mechanisms for potentiation of gamma-aminobutyric acid responses in cultured central neurones. Proc Natl Acad Sci U S A. 1981;78:7180–4.

9. Jones EA, Weissenborn K. Neurology and the liver. J Neurol Neurosurg Psychiatry. 1997;63:279–93.

10. Jones EA, Basile AS, Mullen KD, Gammal SH. Flumazenil: potential implications for hepatic encephalopathy. Pharmacol Ther. 1990;45:331–43.

11. Gardner CR. Pharmacological pro fi les in vivo of benzodiazepine receptor ligands. Drug Dev Res. 1988;12:1–28.

12. Jones EA. Benzodiazepine receptor ligands and hepatic encephalopathy: further unfolding of the GABA story. Hepatology. 1991;14:1286–90.

13. Schafer DF, Jones EA. Hepatic encephalopathy and the g -aminobutyric acid neurotransmitter system. Lancet. 1982;1:18–20.

14. Schafer DF, Pappas SC, Brody LE, Jacobs R, Jones EA. Visual evoked potentials in a rabbit model of hepatic encephalopathy. I. Sequential changes and comparisons with drug-induced comas. Gastroenterology. 1984;86:540–5.

15. Jones DB, Mullen KD, Roessle M, Maynard T, Jones EA. Hepatic encephalopathy: application of visual evoked responses to test hypotheses of its pathogenesis in rats. J Hepatol. 1987;4:118–26.

16. Jones EA. Potential mechanisms of enhanced GABA-mediated inhibitory neurotransmission in liver failure. Neurochem Int. 2003;43:509–16.

17. Anderson B. A proposed theory for the encephalopathies of Reye’s syndrome and hepatic encephalopathy. Med Hypotheses. 1984;15:415–20.

18. Bansky G, Meier PJ, Zeigler WH, et al. Reversal of hepatic coma by benzodiazepine antagonist (Ro 15-1788). Lancet. 1985;1:1324–5.

19. Baraldi M, Zeneroli ML, Ventura E, et al. Supersensitivity of benzodiazepine receptors in hepatic encephalopathy due to fulminant hepatic failure in the rat: reversal by a benzodiazepine antagonist. Clin Sci. 1984;67:167–75.

20. Scollo-Lavizzari G, Steinmann E. Reversal of hepatic coma by benzodiazepine antagonist (Ro 15-1788). Lancet. 1985;1:1324.

21. Mullen KD, Martin JV, Mendelson WB, Bassett ML, Jones EA. Could an endogenous ben-zodiazepine ligand contribute to hepatic encephalopathy? Lancet. 1988;1:457–9.

22. Basile AS, Jones EA, Skolnick P. The pathogenesis and treatment of hepatic encephalopathy: evidence for the involvement of benzodiazepine receptor ligands. Pharmacol Rev. 1991;43:27–71.

23. Mullen KD, Kaminsky-Russ K. Pathogenesis of hepatic encephalopathy: potential future approaches. Dig Dis. 1996;14 Suppl 1:20–9.

24. Klotz U, Ziegler G, Reiman IW. Pharmacokinetics of the selective benzodiazepine antagonist Ro 15-1788 in man. Eur J Clin Pharmacol. 1984;27:115–7.

25. Mullen KD, Martin JV, Mendelson WB, Jones EA. Further evidence that HE in the galac-tosamine rabbit model may be mediated by an endogenous BZ compound. In: Soeters PB, Wilson JHP, Meier AJ, Holm E, editors. Advances in ammonia metabolism and hepatic encephalopathy. Amsterdam: Elsevier Science; 1988. p. 333–7.


26. Mullen KD, Martin JV, Mendelson WB, Kaminsky-Russ K, Jones EA. Evidence for the pres-ence of a benzodiazepine receptor binding substance in cerebrospinal fl uid of a rabbit model of hepatic encephalopathy. Metab Brain Dis. 1989;4:253–60.

27. Mullen KD, Szauter KM, Kaminsky-Russ K, et al. Detection and characterization of endog-enous benzodiazepine activity in both animal models and humans with hepatic encephalopathy. In: Butterworth RF, Layrargues GP, editors. Hepatic encephalopathy: pathophysiology and treatment. Clifton: Humana; 1989. p. 287–94.

28. Mullen KD, Szauter KM, Kaminsky-Russ K. “Endogenous” benzodiazepine activity in body fl uids of patients with hepatic encephalopathy. Lancet. 1990;336:81–3.

29. Basile AS, Gammal SH, Jones EA, Skolnick P. The GABA A receptor complex in an experimen-

tal model of hepatic encephalopathy: evidence for elevated levels of an endogenous benzodiaz-epine receptor ligand. J Neurochem. 1989;53:1057–63.

30. Basile AS, Ostrowski NK, Gammal SH, Jones EA, The SP. The GABA A receptor complex in

hepatic encephalopathy. Autoradiographic evidence for the presence of elevated levels of a benzodiazepine receptor ligand. Neuropsychopharmacology. 1990;3:61–7.

31. Basile AS, Pannell L, Jaouni T, et al. Brain concentrations of benzodiazepines are elevated in an animal model of hepatic encephalopathy. Proc Natl Acad Sci. 1990;87:5263–7.

32. Olasmaa M, Rothstein JD, Guidotti A, et al. Endogenous benzodiazepine receptor ligands in human and animal hepatic encephalopathy. J Neurochem. 1990;55:2015–23.

33. Basile AS. The contribution of endogenous benzodiazepine receptor ligands to the pathogene-sis of hepatic encephalopathy. Synapse. 1991;7:141–50.

34. Mohler H, Richards JG. Agonist and antagonist benzodiazepine receptor interactions in vitro. Nature. 1981;294:763–5.

35. Braestrup C, Schmiechen R, Neef G, et al. Interaction of convulsive ligands with benzodiazepine receptors. Science. 1982;216:1241–3.

36. Skolnick P, Schweri MM, Williams ER, et al. An in vitro binding assay which differentiates benzodiazepine “agonists” and “antagonists”. Eur J Pharmacol. 1982;78:133–6.

37. Olasmaa M, Guidotti A, Costa E, et al. Endogenous benzodiazepines in hepatic encephalopa-thy. Lancet. 1989;1:491–2.

38. Widler P, Fisch HU, Schoch P, et al. Increased benzodiazepine-like activity is neither neces-sary nor suf fi cient to explain acute hepatic encephalopathy in the thioacetamide-treated rat. Hepatology. 1993;18:1459–64.

39. Basile AS, Jones EA. The involvement of benzodiazepine receptor ligands in hepatic enceph-alopathy. Hepatology. 1994;20:541–2.

40. Basile AS, Hughes RD, Harrison PM, et al. Elevated brain concentrations of 1,4-benzodiaz-epines in fulminant hepatic failure. N Engl J Med. 1991;325:473–8.

41. Mullen KD. Benzodiazepine compounds and hepatic encephalopathy. N Engl J Med. 1991;325:509–11.

42. Mullen KD, Roessle M, Jones DB, Grun M, Jones EA. Precipitation of overt encephalopathy in the portacaval shunted rat: towards the development of an adequate model of chronic por-tal-systemic encephalopathy. Eur J Gastroenterol Hepatol. 1997;9:293–8.

43. Yurdaydin C, Gu Z-Q, Nowak G, et al. Benzodiazepine receptor ligands are elevated in an animal model of hepatic encephalopathy: relationship between brain concentration and severity of encephalopathy. J Pharmacol Exp Ther. 1993;265:565–71.

44. Basile AS, Harrison PM, Hughes RD, et al. Relationship between plasma benzodiazepine receptor ligand concentrations and severity of hepatic encephalopathy. Hepatology. 1994;19:112–21.

45. Guidotti A, Forchetti CM, Corda MG, et al. Isolation, characterization and puri fi cation to homogeneity of an endogenous polypeptide with agonistic action on benzodiazepine recep-tors. Proc Natl Acad Sci U S A. 1983;80:3531–5.

46. Shoyab M, Gentry L, Marquardt H, Todaro G. Isolation and characterization of a putative endogenous benzodiazepine (endozepine) from bovine and human brain. J Biol Chem. 1986;261:1168–73.


47. Matquardt H, Todaro G, Shoyab M. Complete amino acid sequences of bovine and human endozepines. J Biol Chem. 1986;262:9227–31.

48. Gray PW. Molecular biology of diazepam binding inhibitor. Neuropharmacology. 1987;26:863–6. 49. Rothstein JD, McKhann G, Guarneri P, et al. Cerebrospinal fl uid content of diazepam binding

inhibitor in chronic hepatic encephalopathy. Ann Neurol. 1989;26:57–62. 50. Mullen KD, Szauter KM, Kaminsky-Russ K, et al. Detection and characterization of endogenous

benzodiazepine activity in both animal models and humans with hepatic encephalopathy. In: Butterworth RF, Layrargues GP, editors. Hepatic encephalopathy: pathophysiology and treatment. Clifton: Humana; 1989. p. 287–94.

51. de Blas AL, Park D, Friedrich P. Endogenous benzodiazepine-like molecules in the human, rat and bovine brains studied with a monoclonal antibody to benzodiazepines. Brain Res. 1987;413:275–84.

52. Baraldi M, Avallone R, Corsi L, Venturini I, Baraldi C, Zeneroli ML. Natural endogenous ligands for benzodiazepine receptors in hepatic encephalopathy. Metab Brain Dis. 2009;24:81–93.

53. Medina JH, Pena C, Piva M, et al. Presence of benzodiazepine-like molecules in mammalian brain and milk. Biochem Biophys Res Commun. 1988;152:534–9.

54. Unseld E, Krishna DR, Fischer C, Klotz U. Detection of desmethyldiazepam and diazepam in brain of different species and plants. Biochem Pharmacol. 1989;38:2473–8.

55. Wildmann J, Vetter W, Ranalder UB, et al. Occurrence of pharmacologically active benzodi-azepines in trace amounts in wheat and potato. Biochem Pharmacol. 1988;37:3549–59.

56. Wildmann J. Increase in neural benzodiazepines in wheat and potato during germination. Biochem Biophys Res Commun. 1988;157:1436–43.

57. Yurdaydin C, Walsh TJ, Engler HD, et al. Gut bacteria provide precursors of benzodiazepine receptor ligands in a rat model of hepatic encephalopathy. Brain Res. 1995;679:42–8.

58. Sangameswaran L, Fales HM, Friedrich P, DeBlas A. Puri fi cation of a benzodiazepine from bovine brain and detection of benzodiazepine-like immunoreactivity in human brain. Proc Natl Acad Sci U S A. 1986;83:9236–40.

59. Wildmann J, Niemann J, Matthaei H. Endogenous benzodiazepine receptor agonist in human and mammalian plasma. J Neural Transm. 1986;66:151–60.

60. Wildmann J, Ranalder U. Presence of lorazepam in the blood plasma of drug free rats. Life Sci. 1988;43:1257–60.

61. Unseld E, Fischer C, Rothemund E, Klotz U. Occurrence of “natural” diazepam in human brain. Biochem Pharmacol. 1990;39:210–2.

62. Luckner M. Secondary metabolism in microorganisms, plants and animals. Berlin: Springer; 1984. p. 274.

63. Haefely W. The preclinical pharmacology of Flumazenil. Eur J Anaesthesiol Suppl. 1988;2:25–36.

64. Basile AS, Gammal SH, Mullen KD, Jones EA, Skolnick P. Differential responsiveness of cerebellar Purkinje neurons to GABA and benzodiazepine receptor ligands in a animal model of hepatic encephalopathy. J Neurosci. 1988;8:2414–21.

65. Jones EA, Skolnick P. Benzodiazepine receptor ligands and the syndrome of hepatic enceph-alopathy. In: Popper H, Schaffner F, editors. Progress in liver diseases, vol. IX. Philadelphia: WB Saunders; 1990. p. 345–70.

66. Pomier-Layrargues G, Giguere J-F, Lavoie J, et al. Pharmacokinetics of benzodiazepine antagonist Ro 15-1788 in cirrhotic patients with moderate and severe liver dysfunction. Hepatology. 1989;10:969–72.

67. Samson Y, Hantraye P, Baron JC, et al. Kinetics and displacement of [ 11 C]Ro 15-1788, a benzodiazepine antagonist, studied in human brain in vivo by positron tomography. Eur J Pharmacol. 1985;110:247–51.

68. Samson Y, Bernuau J, Pappata S, Chavoix C, Baron JC, Maziere MA. Cerebral uptake of benzodiazepine measured by positron emission tomography in hepatic encephalopathy. N Engl J Med. 1987;316:414–5.


69. Savic I, Widen L, Stone-Elander S. Feasibility of reversing benzodiazepine tolerance with fl umazenil. Lancet. 1991;337:133–7.

70. File SE, Pellow S. Intrinsic actions of benzodiazepine receptor antagonist Ro 15-1788. Psychopharmacology. 1986;88:1–11.

71. Scollo-Lavizzari G. The anticonvulsant effect of the benzodiazepine antagonist, Ro 15-1788: an EEG study in 4 cases. Eur Neurol. 1984;23:1–6.

72. Grimm G, Ferenci P, Katzenschlager R, et al. Improvement of hepatic encephalopathy treated with fl umazenil. Lancet. 1988;2:1392–4.

73. Bansky G, Meier PJ, Riederer E, et al. Effects of the benzodiazepine receptor antagonist fl umazenil in hepatic encephalopathy in humans. Gastroenterology. 1989;97:744–50.

74. Jones EA, Ferenci P. Hepatic encephalopathy, GABAergic neurotransmission and the benzodiazepines. In: Conn HO, Bircher J, editors. Hepatic encephalopathy: syndromes and therapies. Bloomington: Medi-Ed Press; 1994. p. 75–100.

75. Burke DA, Mitchel KW, Burke DA, Mitchel KW, Al Mardini H, et al. Reversal of hepatic coma with fl umazenil with improvement in visual evoked potentials. Lancet. 1988;1:505–6.

76. Googay R, Hayes PC, Bzeizi K, O’Carroll RE. Benzodiazepine receptor antagonism improves reaction time in latent hepatic encephalopathy. Psychopharmacology. 1995;119:295–8.

77. Jones EA, Giger-Mateeva VI, Reits D, et al. Visual event-related potentials in cirrhotic patients without overt encephalopathy: the effects of fl umazenil. Metab Brain Dis. 2001;16:43–53.

78. Ferenci P, Grimm G, Meryn S, Gangl A. Successful long-term treatment of portal-systemic encephalopathy by the benzodiazepine receptor antagonist fl umazenil. Gastroenterology. 1989;96:240–3.

79. Bassett ML, Mullen KD, Skolnick P, Jones EA. Amelioration of hepatic encephalopathy by pharmacological antagonism of the GABA

A -benzodiazepine receptor complex in a rabbit

model of fulminant hepatic failure. Gastroenterology. 1987;93:1069–77. 80. Gammal SH, Basile AS, Geller D, Skolnick P, Jones EA. Reversal of the behavioral and

electrophysiological abnormalities of an animal model of hepatic encephalopathy by benzo-diazepine receptor ligands. Hepatology. 1990;11:371–78.

81. Van der Rijt CCD, de Knegt RJ, Schalm SW, et al. Flumazenil does not improve hepatic encephalopathy associated with acute ischemic liver failure in the rabbit. Metab Brain Dis. 1990;5:131–41.

82. Bosman DK, van den Buijs CACG, de Haan JG, Maas MAW, Chamuleau RAFM. The effects of benzodiazepine-receptor antagonists and partial inverse agonists on acute hepatic enceph-alopathy in the rat. Gastroenterology. 1991;101:772–81.

83. Steindl P, Puspok A, Druml W, Ferenci P. Bene fi cial effect of pharmacological modulation of the GABAA-benzodiazepine receptor on hepatic encephalopathy in the rat: comparison with uremic encephalopathy. Hepatology. 1991;14:963–8.

84. Puspok A, Herneth A, Steindl P, Ferenci P. Hepatic encephalopathy in rats with thioacetamide-induced acute liver failure is not mediated by endogenous benzodiazepines. Gastroenterology. 1993;105:851–7.

85. Maher HP, Legemate DA, van den Brom W, Rothuizen J. Improvement of chronic hepatic encephalopathy in dogs by the benzodiazepine-receptor partial inverse agonist sarmazenil, but not by the antagonist fl umazenil. Metab Brain Res. 1998;13:241–51.

86. Mullen KD, Basile AS. Benzodiazepine receptor antagonists and hepatic encephalopathy: where do we stand? Gastroenterology. 1993;105:937–40.

87. Zieve L, Ferenci P, Rzepczynski D, Ebner J, Zimmermann Ch. A benzodiazepine antagonist does not alter the course of hepatic encephalopathy or neural gamma-aminobutyric acid (GABA) binding. Metab Brain Dis. 1987;2:201–5.

88. Jones EA. Hepatocellular failure. In: Warrell DA, Cox TM, Firth JD, editors. Oxford text-book of medicine. 5th ed. Oxford: Oxford University Press; 2010. p. 2493–505.

89. Blitzer BL, Waggoner JG, Jones EA, et al. A model of fulminant hepatic failure in the rabbit. Gastroenterology. 1978;74:664–71.


90. Mullen KD, Schafer DF, Cuchi P, et al. Evaluation of the suitability of galactosamine-induce fulminant hepatic failure as a model of hepatic encephalopathy in the rat and rabbit. In: Soeters PB, Wilson JMP, Meijer AJ, Holm E, editors. Recent advances in ammonia metabo-lism and hepatic encephalopathy. Amsterdam: Elsevier; 1988. p. 205–12.

91. Als-Nielsen B, Gluud LL, Gluud C. Benzodiazepine receptor antagonists for hepatic enceph-alopathy. Cochrane Database Syst Rev. 2004;(2):CD002798.

92. Schafer DF. In hepatic coma, the problem comes from the colon, but will the answer come from there? J Lab Clin Med. 1987;110:253–4.

93. Schafer DF. Hepatic coma: studies on the target organ. Gastroenterology. 1987;93:1131–4. 94. Jones EA, Yurdaydin C, Basile AS. Benzodiazepine antagonists and the management of

hepatic encephalopathy. In: Capacaccia L, Merli M, Riggio O, editors. Advances in hepatic encephalopathy and metabolic nitrogen exchange. Boca Raton: CRC Press; 1995. p. 549–63.

95. Sutherland LR, Minuk GY. Ro 15-1788 and hepatic failure. Ann Intern Med. 1988;108:158. 96. Ferenci P, Herneth A, Steindl P. Newer approaches to therapy of hepatic encephalopathy. In:

Blei AT, Butterworth RF (Eds). Hepatic encephalopathy. Semin Liver Dis. 1996;16:329–38. 97. Van der Rijt CCD, Schalm SW, Meulster J, Stijnen T. Flumazenil therapy for hepatic enceph-

alopathy: a double-blind cross-over study. Hepatology. 1989;10:590. 98. Klotz U, Walker S. Flumazenil and hepatic encephalopathy. Lancet. 1989;1:155–6. 99. Ahboucha S, Coyne L, Hirakawa R, Butterworth RF, Halliwell RF. An interaction between

benzodiazepines and neuroactive steroids at GABAA receptors in cultured hippocampal neu-rons. Neurochem Int. 2006;48:703–7.

100. Bassett ML, Mullen KD, Scholz B, et al. Increased brain uptake of gamma-aminobutyric acid in a rabbit model of hepatic encephalopathy. Gastroenterology. 1990;98:747–57.

101. Albrecht J, Jones EA. Hepatic encephalopathy: molecular mechanisms underlying the clinical syndrome. J Neurolog Sci. 1999;170:138–46.

102. Gammal SH, Basile AS, Skolnick P, Jones EA. Isolated CNS neurons from a model of hepatic encephalopathy exhibit increased sensitivity to a benzodiazepine. In: Butterworth RF, Pomier Layrarques G, editors. Hepatic encephalopathy: pathophysiology and treatment. Clifton: Humana; 1989. p. 295–304.

103. Bakti G, Fisch HU, Karlaganis G, Minder C, Bircher J. Mechanism of the excessive sedative response of cirrhotics to benzodiazepines: model experiments with triazolam. Hepatology. 1987;7:629–38.

Part II Diagnosis


Keywords Diagnostic approach • Acquired hepatocerebral degeneration • Hepatic myelopathy • Magnetic resonance spectroscopy • Magnetic resonance imaging

Introduction

De fi cits in attention, visual perception, visuo-spatial construction, motor speed and accuracy are early symptoms of hepatic encephalopathy (HE) [ 1 ] . Due to subtle nature of these cognitive de fi cits, psychometric testing is required to detect the earli-est grade of cerebral dysfunction in HE—the so-called minimal HE (mHE). Later on clinically obvious psychomotor slowing, increasing alterations of consciousness, pyramidal and extrapyramidal as well as cerebellar symptoms and signs occur. Patients are classi fi ed into grades I–IV HE according to the degree of altered con-sciousness (as determined by the New Haven Scale) [ 2 ] . Lethargy and psychomotor slowing is classi fi ed as grade I HE, disorientation is considered to represent grade II HE, somnolence and stupor grade III HE and coma grade IV HE. The accompanying motor symptoms indicate a dysfunction of the cerebellar, extrapyramidal and pyra-midal system, and can be detected by a thorough neurological examination even in patients who appear clinically unaffected on the fi rst view [ 3 ] . But the frequency and extent of motor symptoms such as asterixis, ataxia, dysarthria, tremor, rigidity, hypo-mimia and hypokinesia, as well as hyperre fl exia, spasticity and extensor plantar responses increases with increasing grade of HE. In patients with acute liver failure, HE (Type A HE) is accompanied and even masked by the effects of increasing brain edema [ 4 ] . These patients develop neurological symptoms more rapidly than those with Type C HE, and in contrast to the latter they also suffer epileptic seizures [ 5 ] .

K. Weissenborn, MD (*) Department of Neurology , Hannover Medical School , Carl-Neuberg-Strasse 1 , Hannover 30625 , Germany e-mail: [email protected]

Chapter 7 Diagnosis of Overt Hepatic Encephalopathy

Karin Weissenborn

98 K. Weissenborn

In patients with cirrhosis, clinically overt HE usually occurs episodically. It is often precipitated by dietary protein overload, gastrointestinal bleeding, infection, electrolyte imbalance or CNS active medication. A few patients, however, present with chronic progressive symptoms with Parkinsonism, dystonia or choreatic move-ments as acquired hepatocerebral degeneration (AHD) and/or spastic paraparesis as hepatic myelopathy (HM).

The symptoms of HE are manifold and of course none of the symptoms of hepatic encephalopathy (HE) or hepatic myelopathy (HM) are speci fi c. Thus, the diagnosis of HE or HM can be made only by exclusion of other possible causes of brain or spinal cord dysfunction, and can be proven only by a positive response to the respec-tive therapy.

The appropriate diagnostic procedure depends on the quality and time-course of the symptoms presented, the underlying liver disease and the patients’ co-morbidities and medication.

Diagnostic Approach

Biochemical Analysis

Metabolic disturbances, which may affect brain function, besides hyperammonemia have to be considered. These include hyponatremia [ 6 ] in patients with liver cirrho-sis and hypoglycemia in patients with acute liver failure [ 4 ] .

Measurement of serum ammonia is not indicated for routine diagnosis of HE in clinical practice. An increased serum ammonia level may indicate HE as the cause of a patient’s altered mental status, but other potential sources of hyperammonemia have to be excluded, and hyperammonemia per se is no proof that cerebral dysfunc-tion in the individual patient under study is due to elevated ammonia levels. Mean ammonia levels increase with increasing grade of HE, but there is a substantial overlap between values at different stages [ 7 ] .

While the assessment of plasma ammonia levels is not of diagnostic use in patients with HE, it appears to be worthwhile for the estimation of patient’s progno-sis in case of acute liver failure [ 8, 9 ] . Arterial ammonia levels >124 m mol/L indi-cate a higher risk of cerebral herniation, seizures and death [ 9 ] .

Brain Imaging

Even in the presence of signi fi cant metabolic alterations, brain imaging should be done in every patient who develops disorientation, somnolence or stupor to exclude other possible causes such as intracranial bleeding. Chronic subdural hematoma

997 Diagnosis of Overt Hepatic Encephalopathy

may present with alterations of cognition and consciousness exclusively, but with no focal neurological signs, and is more frequent in patients with coagulopathy specially so in patients with alcoholic liver disease. If available, magnetic resonance imaging (MRI) should be preferred to cranial computed tomography (CCT) because MRI offers the opportunity to look also for the characteristic signs of Wernicke’s encephalopathy—the most important differential diagnosis of hepatic encephalopa-thy, especially in patients with alcoholic liver disease [ 10 ] .

MRI has been shown to be pathological in about two-thirds of alcoholics with clinically proven Wernicke’s encephalopathy (WE) and in about 100% of published WE cases in nonalcoholics [ 11 ] . Symmetric lesions are usually seen in the thalami, mamillary bodies, tectal plate and the periaquaeductal area. But in addition, cerebel-lar and cortical lesions as well as lesions in the splenium and the caudate nucleus have been observed [ 11, 12 ] . Long-TR (repetition time) MR images are considered the most sensitive technique for the diagnosis of WE and contrast enhancement of the mamillary bodies may be the only sign of WE [ 13 ] . In practice, the radiologist should be aware of the differential diagnosis of Wernicke’s encephalopathy to be able to consider this in patients with symptoms of HE.

Of note, the symmetric pallidal signal alterations in T1-weighted images, which are frequently observed in patients with cirrhosis, are not diagnostic for hepatic encephalopathy [ 14 ] . They are due to an increased manganese deposition in brain tissue with a preference to basal ganglia and indicate the presence of signi fi cant porto-systemic shunts [ 15 ] . Newer MR imaging techniques such as MR volumetry, diffusion-weighted imaging and magnetization transfer imaging have been used to study hepatic encephalopathy, but none of these techniques have been evaluated for its diagnostic use [ 14 ] . Magnetic resonance spectroscopy (MRS) of the brain in patients with liver cirrhosis has consistently shown a decrease in myo-inositol and choline signal intensity accompanied with an increase in glutamate/glutamine sig-nal intensity [ 14 ] . These alterations correlate with the degree of hepatic encephal-opathy [ 16 ] and improve with medical treatment [ 17 ] or liver transplantation [ 18 ] . But, again, the use of MRS for diagnosing HE has still to be established since the characteristic alterations seen in patients with cirrhosis and HE may be present also in cirrhotic patients without any signs of HE [ 19 ] , and they cannot exclude the pres-ence of another pathology that does not affect MRS such as, for example, drug effects or thiamine de fi ciency.

Lumbar Puncture

Sub-acute development of disorientation and alteration of consciousness are also frequent symptoms of encephalitis, but encephalitis has rarely to be considered in the differential diagnosis of HE. In case there is any doubt, lumbar puncture should be performed.

100 K. Weissenborn

Electroencephalogram

The electroencephalogram (EEG) is slowed in patients with hepatic encephalopathy. Higher grades of HE are typically associated with theta or delta-dominated EEG and frontal triphasic waves. But, again, this alteration is not speci fi c for HE but can be seen also with other metabolic disturbances such as hyponatremia or uraemia [ 20 ] . Thus, the EEG cannot be recommended as a diagnostic tool. Instead, it can be used for follow-up examinations and monitoring of treatment effects after the diagnosis has been made [ 20 ] .

Diagnosis of Chronic Progressive HE

Differential diagnosis of AHD is more demanding than differential diagnosis of episodic HE. Patients with AHD present with Parkinsonism, dystonia, dyskinesia and choreatic movements. The symptoms may develop more rapidly than in classic neurodegenerative disorders such as Parkinson’s disease, but they may also show a very slow progress over years, and even remain stable for some time [ 21 ] . The most frequent feature of AHD is Parkinsonism [ 22 ] . Differential diagnosis between AHD and Parkinson’s disease (PD) should consider the difference in symptom progres-sion, the symmetry in motor symptoms in AHD in contrast to PD, the presence of action tremor in AHD but not PD and the absence of the characteristic shuf fl ing gait of patients with Parkinson’s disease in AHD [ 22, 23 ] . Again, brain imaging by CT or MRI does not help in the differential diagnosis. The analysis of the striatal dopamine D2 receptor binding capacity (which is not altered in patients with devel-oping Parkinson’s disease) combined with an analysis of the striatal dopamine transporter binding capacity might add useful information [ 24, 25 ] . Both dopamine D2 receptor and dopamine transporter binding have been shown to be compromised in a patient with cirrhosis and hepatic encephalopathy by single photon emission tomography (SPET) [ 24 ].

Differential diagnosis between AHD and the so-called Parkinson plus or atypical Parkinson syndromes is more dif fi cult as both syndromes share the combination of Parkinsonian symptoms and cerebellar or pyramidal symptoms and the SPET results. Here, again the time-course of symptom development may help to distin-guish between these different entities. Unfortunately, the response to treatment cannot be used for differential diagnostic purposes in this situation. AHD does not respond to the usual ammonia-lowering therapeutic strategies working for episodic HE, but some patients respond to dopaminergic drugs [ 26, 27 ] .

Differential diagnosis of hepatic myelopathy is less demanding. Again, the clinical symptoms are not speci fi c, but they are quite characteristic: a rapidly progressive spastic paraparesis without any sensory symptoms that binds the patient to a wheel-chair within a few months in the absence of spinal cord lesions visible on MRI and accompanied by normal cerebrospinal fl uid analysis results [ 28, 29 ] . Again the

1017 Diagnosis of Overt Hepatic Encephalopathy

diagnosis cannot be tested by the response to ammonia-lowering therapies, as HM has been shown not to respond to the usual therapy of HE. Of note, however, there are several reports of the bene fi cial effects of liver transplantation for both AHD and HM [ 28, 30, 31 ] .

References

1. Weissenborn K, Ennen JC, Schomerus H, Rückert N, Hecker H. Neuropsychological charac-terization of hepatic encephalopathy. J Hepatol. 2001;34:768–73.

2. Conn HO, Leevy CM, Vlahcevic ZR, Rodgers JB, Maddrey WC, Seeff L, et al. Comparison of lactulose and neomycin in the treatment of chronic portal systemic encephalopathy. A double blind controlled trial. Gastroenterology. 1977;72:573–83.

3. Krieger S, Jauss M, Jansen O, Theilmann L, Geissler M, Krieger D. Neuropsychiatric pro fi le and hyperintense globus pallidus on T1-weighted magnetic resonance images in liver cirrho-sis. Gastroenterology. 1996;111(1):147–55.

4. Bernal W, Auzinger G, Dhawan A, Wendon J. Acute liver failure. Lancet. 2010;376:190–201. 5. Ellis AJ, Wendon JA, Williams R. Subclinical seizure activity and prophylactic phenytoin

infusion in acute liver failure: a controlled clinical trial. Hepatology. 2000;32(3):536–41. 6. Córdoba J, García-Martinez R, Simón-Talero M. Hyponatremic and hepatic encephalopathies:

similarities, differences and coexistence. Metab Brain Dis. 2010;25(1):75–80. 7. Ong JP, Aggarwal A, Krieger D, Easley KA, Karafa MT, Van Lente F, et al. Correlation between

ammonia levels and the severity of hepatic encephalopathy. Am J Med. 2003;114(3):188–93. 8. Clemmesen JO, Larsen FS, Kondrup J, Hansen BA, Ott P. Cerebral herniation in patients with

acute liver failure is correlated with arterial ammonia concentration. Hepatology. 1999;29: 648–53.

9. Bathia V, Singh R, Acharya SK. Predictive value of arterial ammonia for complications and outcome in acute liver failure. Gut. 2006;55(1):98–104.

10. Kril JJ, Butterworth RF. Diencephalic and cerebellar pathology in alcoholic and nonalcoholic patients with end-stage liver disease. Hepatology. 1997;26:837–41.

11. Galvin R, Brathen G, Ivashynka A, Hillbom M, Tanasescu R, Leone MA. EFNS guidelines for diagnosis, therapy and prevention of Wernicke encephalopathy. Eur J Neurol. 2010;17:1408–18.

12. Luigetti M, De Paulis S, Spinelli P, Sabatelli M, Tonali P, Colosimo C, et al. Teaching NeuroImages: the full-blown neuroimaging of Wernicke encephalopathy. Neurology. 2009;72:e115.

13. Zuccoli G, Pipitone N. Neuroimaging fi ndings in acute Wernicke’s encephalopathy: review of the literature. AJR. 2009;192:501–8.

14. McPhail MJW, Taylor-Robinson S. The role of magnetic resonance imaging and spectroscopy in hepatic encephalopathy. Metab Brain Dis. 2010;25:65–72.

15. Spahr L, Butterworth RF, Fontaine S, Bui L, Therrien G, Milette PC, et al. Increased blood manganese in cirrhotic patients: relationship to pallidal magnetic resonance signal hyperinten-sity and neurological symptoms. Hepatology. 1996;24:1116–20.

16. Haussinger D, Laubenberger J, vom Dahl S, Ernst T, Bayer S, Langer M, et al. Proton mag-netic resonance spectroscopy studies on human brain myo-inositol in hypo-osmolarity and hepatic encephalopathy. Gastroenterology. 1994;107:1475–80.

17. Hass HG, Naegele T, Seeger U, Hosl F, Gregor M, Kaiser S. Detection of subclinical and overt hepatic encephalopathy and treatment control after L-ornithine-L-aspartate medication by magnetic resonance spectroscopy ((1)H-MRS). Z Gastroenterol. 2005;43:373–8.

18. Naegele T, Grodd W, Viebahn R, Seeger U, Klose U, Seitz D, et al. MR imaging and (1)H spectroscopy of brain metabolites in hepatic encephalopathy: time-course of renormalization after liver transplantation. Radiology. 2000;216:683–91.

102 K. Weissenborn

19. Köstler H. Proton magnetic resonance spectroscopy in portal-systemic encephalopathy. Metab Brain Dis. 1998;13(4):291–301.

20. Guerit JM, Amantini A, Fischer C, Kaplan PW, Mecarelli O, Schnitzler A, Ubiali E, Amodio P, Members of the ISHEN Commission on Neurophysiological Investigations. Neurophysiological investigations of hepatic encephalopathy: ISHEN practice guidelines. Liver Int. 2009; 29(6):789–96.

21. Victor M, Adams RD, Cole M. The acquired (non-Wilsonian) type of chronic hepatocerebral degeneration. Medicine (Baltimore). 1965;44:345–96.

22. Ferrara J, Jankovic J. Acquired hepatocerebral degeneration. J Neurol. 2009;256(3):320–32. 23. Fernández-Rodriguez R, Contreras A, De Villoria JG, Grandas F. Acquired hepatocerebral

degeneration: clinical characteristics and MRI fi ndings. Eur J Neurol. 2010;17(12):1463–70. 24. Weissenborn K, Berding G, Köstler H. Altered striatal dopamine D2 receptor density and dop-

amine transport in a patient with hepatic encephalopathy. Metab Brain Dis. 2000;15(3):173–8. 25. Isaias IU, Antonini A. Single-photon emission computed tomography in diagnosis and differ-

ential diagnosis of Parkinson’s disease. Neurodegener Dis. 2010;7:319–29. 26. Burkhard PR, Delavelle J, Du Pasquier R, Spahr L. Chronic parkinsonism associated with

cirrhosis: a distinct subset of acquired hepatocerebral degeneration. Arch Neurol. 2003;60(4): 521–8.

27. Lunzer M, James IM, Weinman J, Sherlock S. Treatment of chronic hepatic encephalopathy with levodopa. Gut. 1974;15:555–61.

28. Weissenborn K, Tietge UJ, Bokemeyer M, Mohammadi B, Bode U, Manns MP, et al. Liver transplantation improves hepatic myelopathy: evidence by three cases. Gastroenterology. 2003;124(2):346–51.

29. Campellone JV, Lacomis D, Giuliani MJ, et al. Hepatic myelopathy. Case report with review of the literature. Clin Neurol Neurosurg. 1996;98:242–6.

30. Baccarani U, Zola E, Adani GL, Cavalletti M, Schiff S, Cagnin A, et al. Reversal of hepatic myelopathy after liver transplantation: fi fteen plus one. Liver Transpl. 2010;16(11):1336–7.

31. Pinarbasi B, Kaymakoglu S, Matur Z, Akyuz F, Demir K, Besisik F, et al. Are acquired hepa-tocerebral degeneration and hepatic myelopathy reversible? J Clin Gastroenterol. 2009; 43(2):176–81.


Keywords Minimal hepatic encephalopathy • Covert hepatic encephalopathy • Cirrhosis • Psychometric testing • Neurophysiological testing

Introduction

The current classi fi cation of hepatic encephalopathy (HE) is the well-known West Haven criteria, which is based on impairment in consciousness, intellectual func-tion, and behavior (Table 8.1 ) [ 1 ] . The use of the West Haven scale alone is incon-sistent when grading patients in stages 0 through 2 because it relies on subjective assessments by clinicians, which may vary by individual clinician and across multi-center trials [ 2 ] . Nonspeci fi c signs and symptoms are often used in differentiating between stages 0 and 1; therefore, there is a lack of reproducibility and inconsis-tency. The approach to HE as a continuum on the spectrum of neurocognitive impairment in cirrhosis (SONIC) is now promoted [ 3, 4 ] . In a round table at the 14th International Society for Hepatic Encephalopathy and Nitrogen Metabolism (ISHEN) meeting, it was suggested that patients with minimal HE and grade I HE should be grouped together, with the conjoined group termed as “covert” HE [ 5 ] .

J. Y. Montgomery, MD Department of Internal Medicine , Virginia Commonwealth University Health System , Richmond , VA 23298 , USA

J. S. Bajaj, MBBS, MD, MS (*) Department of Gastroenterology, Hepatology and Nutrition , Virginia Commonwealth University and McGuire VA Medical Center , 1201 Broad Rock Boulevard , Richmond , VA 23249 , USA e-mail: [email protected]

Chapter 8 Diagnosis of Minimal Hepatic Encephalopathy

Jennifer Y. Montgomery and Jasmohan S. Bajaj

104 J.Y. Montgomery and J.S. Bajaj

Table 8.1 West Haven criteria for the classi fi cation of hepatic encephalopathy

Grade Characteristics

0 No detectable abnormalities in personality or behavior

I Trivial lack of awareness Euphoria or anxiety Sleep disturbance, altered mood Shortened attention span Impaired addition and/or subtraction Asterixis may be present

II Lethargy, apathy Disorientation to time, amnesia of recent events Subtle to obvious personality changes Inappropriate behavior Slurred speech Asterixis is present

III Somnolence, semi-stupor Confusion, responsive to verbal stimuli Gross disorientation Bizarre behavior Clonus, nystagmus, positive Babinski sign Asterixis is usually absent

IV Coma Unresponsive to verbal and/or noxious stimuli No verbal, eye, or oral response

Table 8.2 Revised classi fi cation

New classi fi cation Old classi fi cation Mental status Performance on specialized tests a Asterixis

Unimpaired Normal No impairment No impairment Not present

Covert HE Minimal HE No impairment Impairment Not present Grade I

Overt HE Grade II Disorientation through coma

Impairment/abnormal

Present (except in coma) Grade III

Grade IV

a Neuropsychometric or neurophysiological tests

Patients with neuropsychological or neurophysiological abnormalities without disorientation and asterixis would be classi fi ed as having covert HE, while those with West Haven grade II or above would be classi fi ed as overt HE. Patients with no clinical, neuropsychometric, or neurophysiological changes would be classi fi ed as unimpaired (Table 8.2 ) [ 5 ] .

Therefore, for the rest of the chapter we will be using the terms covert/minimal HE.

1058 Diagnosis of Minimal Hepatic Encephalopathy

Diagnostic Methods

Unlike the diagnosis of overt hepatic encephalopathy, in which a physical and mental status exam shows clear evidence of impairment, the diagnosis of covert/minimal hepatic encephalopathy is less apparent [ 6 ] . Covert/minimal hepatic encephalopathy shows abnormalities on psychometric testing, particularly in areas of attention (demonstrated by loss of vigilance, disorientation), executive functions (problem-solving, planning, judgment), visuo-spatial coordination, and psychomotor speed (reaction times) [ 4 ] . These in turn can lead to learning and memory impairment. Underlying many of these de fi cits is also an impaired response inhibition [ 3 ] . Therefore, testing strategies focus on de fi ning abnormalities related to these domains using (a) neuropsychological or (b) neurophysiological tests. An overall description of key tests used is presented in Table 8.3 .

Neuropsychological Testing

Experts agree that a battery of tests that measure multiple cognitive domains is more reliable and reproducible than a single test [ 1 ] . An example of a standardized battery is the portosystemic encephalopathy (PSE) syndrome test (or Psychometric Hepatic Encephalopathy Score [PHES]) [ 7 ] . It includes number connection test A (NCT-A), NCT-B, digit symbol test (DST), line-tracing test (LTT), and serial-dotting test (SDT). The ISHEN practice guidelines recommend the PHES because it is rela-tively cross-cultural, easily applied and relies on nonverbal tasks that require mini-mal language translation [ 8 ] . The PHES is highly speci fi c for the diagnosis of HE, with poor prognosis implicated by PHES scores £ −6, indicating severe abnormali-ties [ 9 ] . The major limitations are the lack of normative reference data outside of Europe, and varying performances noted among ethnic subgroups. In places with-out PHES normative data, such as the United States, it is recommended that at least two of the following neuropsychological tests be used: NCT-A, NCT-B, block-design test (BDT), and DST. The current de fi nition of minimal hepatic encephal-opathy (MHE) is based on psychometric test results of two standard deviations less than normal on at least two of these tests [ 1 ] .

A second standardized battery, the repeatable battery for the assessment of neu-ropsychological status (RBANS), was originally designed to assess dementia. It includes a copyrighted set of tests in fi ve domains: immediate memory, visuo- spatial/constructional, language, attention, and delayed memory. RBANS scores predicted disability independently of liver disease severity [ 8 ] . The ISHEN practice guidelines recommend RBANS due to the rigorous population-based standardiza-tion in the United States; however, it has not been speci fi cally validated in HE.

The inhibitory control test (ICT) is a computerized test of sustained attention, vigilance, working memory, and response inhibition [ 10 ] . During this test, the patient is asked only to respond to targets and not to lures. Covert/minimal HE


Tabl

e 8.

3 C

ompa

riso

n of

cur

rent

ly a

vaila

ble

psyc

hom

etri

c te

sts

Test

D

omai

ns te

sted

U

.S. n

orm

s av

aila

ble?

C

opy-

righ

ted?

E

xper

tise

need

ed?

Tim

e ne

eded

fo

r ad

min

is-

trat

ion

(s/m

in)

Lim

itatio

ns

Pape

r an

d pe

ncil

psyc

hom

etri

c te

sts

Num

ber

conn

ectio

n te

st

A (

NC

T-A

) a Ps

ycho

mot

or s

peed

Y

N

N

30

–120

s

Poor

spe

ci fi c

ity

NC

T-B

a Ps

ycho

mot

or s

peed

N

Y

Y

1–

3 m

in

Poor

spe

ci fi c

ity

(im

prov

ed o

ver

NC

T-A

) Se

t shi

ftin

g D

ivid

ed a

ttent

ion

Dig

it sy

mbo

l tes

t (D

ST) a

Psyc

hom

otor

spe

ed

Y

Y

Y

2 m

in

Ver

y se

nsiti

ve; c

an b

e us

ed a

s an

ear

ly

indi

cato

r A

ttent

ion

Lin

e tr

acin

g te

st (

LTT

) a Ps

ycho

mot

or s

peed

N

Y

N

10

min

V

isuo

-spa

tial

reas

onin

g Se

rial

dot

ting

test

(S

DT

) a Ps

ycho

mot

or s

peed

N

Y

N

1–

4 m

in

Onl

y te

sts

psyc

hom

otor

spe

ed

Blo

ck d

esig

n te

st

(BD

T)

Psyc

hom

otor

spe

ed

Y

Y

Y

10–2

0 m

in

Prax

is

Vis

uo-s

patia

l re

ason

ing

Rep

eata

ble

batte

ry f

or

the

asse

ssm

ent o

f ne

urop

sych

olog

ical

st

atus

(R

BA

NS)

Psyc

hom

otor

spe

ed

Y

Y

Y

35 m

in

Lim

ited

stud

ies

invo

lvin

g H

E

Vis

uo-s

patia

l re

ason

ing

Lan

guag

e V

erba

l, vi

sual

, w

orki

ng m

emor

y

1078 Diagnosis of Minimal Hepatic Encephalopathy Te

st

Dom

ains

test

ed

U.S

. nor

ms

avai

labl

e?

Cop

y-ri

ghte

d?

Exp

ertis

e ne

eded

?

Tim

e ne

eded

fo

r ad

min

is-

trat

ion

(s/m

in)

Lim

itatio

ns

Com

pute

rize

d ps

ycho

met

ric

test

s

Inhi

bito

ry c

ontr

ol te

st

(IC

T)

Atte

ntio

n Y

(lim

ited)

N

N

15

min

R

equi

res

high

fu

nctio

ning

pat

ient

s w

ith k

now

ledg

e of

com

pute

rs

Res

pons

e in

hibi

tion

Vig

ilanc

e W

orki

ng m

emor

y C

ogni

tive

drug

res

earc

h (C

DR

) A

ttent

ion

N

Y

N

15–2

0 m

in

Req

uire

s hi

gh

func

tioni

ng p

atie

nts

with

kno

wle

dge

of

com

pute

rs

Wor

king

mem

ory

Epi

sodi

c m

emor

y

Neu

roph

ysio

logi

cal

test

s E

lect

roen

ceph

alog

raph

y (E

EG

), m

ean

dom

inan

t fre

quen

cy

Gen

eral

ized

bra

in

activ

ity

Y (

loca

l)

N

Y

Var

ies

Vis

ual e

voke

d po

tent

ials

(V

EPs

) In

terv

al b

etw

een

activ

ity a

nd

visu

al s

timul

us

Y (

loca

l)

N

Y

Var

ies

Hig

hly

vari

able

res

ults

Bra

inst

em a

udito

ry

evok

ed p

oten

tials

C

ortic

al r

espo

nse

afte

r au

dito

ry

stim

ulus

Y (

loca

l)

N

Y

Var

ies

Show

n to

hav

e in

cons

iste

nt r

esul

ts

in H

E p

atie

nts

P300

cog

nitiv

e ev

oked

po

tent

ials

In

freq

uent

stim

ulus

em

bedd

ed in

ir

rele

vant

stim

uli

Y (

loca

l)

N

Y

Var

ies

Req

uire

s pa

tient

co

oper

atio

n;

pote

ntia

l for

goo

d di

agno

stic

res

ults

C

ritic

al fl

icke

r fr

eque

ncy

(CFF

) V

isua

l dis

crim

inat

ion

N

N

N

10 m

in

Req

uire

s hi

gh

func

tioni

ng p

atie

nts

Gen

eral

aro

usal

a The

se fi

ve te

sts

are

part

of

the

psyc

hom

etri

c he

patic

enc

epha

lopa

thy

scor

e (P

HE

S)


patients had longer reaction times, lower rate of target response, higher rate of lure response than unimpaired patients, with a sensitivity of 87% and speci fi city of 77% [ 11 ] . Impairment demonstrated on ICT is signi fi cantly associated with motor vehi-cle accidents and traf fi c violations [ 12, 13 ] . Other studies showed that ICT targets are a better differentiator than lures alone, and that ICT outcome lures are more valuable if adjusted for target accuracy [ 14 ] . ICT is a free and easily administered test; however, even though the equipment has been standardized, there still remain signi fi cant variations in the threshold levels used and the test requires intense patient concentration.

The Cognitive Drug Research (CDR) battery of tests was developed by Cognitive Drug Research Ltd. With over 50 parallel forms of each task, it tests fi ve domains: attention, continuity of attention, speed of memory, quality of episodic and working memories. Covert/minimal HE patients were found to have impairment in all domains, worsened after a nitrogen challenge and improved with liver transplanta-tion [ 15 ] . The CDR has been validated in the United Kingdom and is available for approximately 50 USD.

These neuropsychological tests are well-documented and extensively tested; however, they have many limitations. Results are often greatly in fl uenced by the patients’ age, educational status, and cultural/ethnic background; therefore local, population-based normative values are necessary. The choice of which battery/test to select should be driven by availability of local normative data as well as expertise [ 5 ] .

Neurophysiological Testing

Neurophysiological tests involve specialized, computer-assisted techniques and are offered under the supervision of a neurologist. They are recommended to be used in conjunction with neuropsychological tests [ 1 ] . The advantages of neurophysio-logical testing are the absence of learned effects, objective data, and the high speci fi city of the response [ 16 ] . These tools provide objective data on brain electri-cal activity and do not require patient cooperation, which allows comparisons between multiple centers.

Electroencephalography (EEG) is the electrophysiological technique most fre-quently used to assess neuropsychiatric status in cirrhotic patients [ 17 ] . An EEG re fl ects cortical neuronal activity and shows generalized slowing of the background activity with characteristic triphasic waves in overt HE [ 18 ] . In covert/minimal HE, the mean dominant frequency is slowed, and has been shown to correlate with PHES abnormalities [ 16 ] . EEG abnormalities were detected in 8–40% of MHE patients, but this wide range may re fl ect variations in technique (quality of the recording and the analysis performed).

Evoked potentials measure the latency between an applied stimulus and the brain’s ability to sense it [ 19 ] . They are small phasic potentials elicited in response to sensory, motor, and cognitive events. Visual evoked potentials (VEPs) can be


fl ash, pattern-reversal, or motion-elicited. Abnormalities are observed in pure optic nerve disorders, demyelinating processes, metabolic abnormalities and psy-chotropic medications, but to date, results in cirrhotics have been dif fi cult to inter-pret [ 19 ] . Somatosensory evoked potentials (SEPs) are measured following brief electric shocks administered via skin electrodes to large, mixed-type peripheral nerves (i.e., median/ulnar nerves at the wrist, peroneal nerve at the knee, tibial nerve at the ankle). A prolongation of the peak and interpeak latencies N20–N65 in one or more cortical SEPs was observed in up to 50% of covert/minimal HE patients. These fi ndings suggest that SEPs may be a promising tool in the diagno-sis of HE [ 16, 20 ] .

Brain electrical responses to an auditory stimulus can likewise be measured. The P300 event-related potential (P300ERP) uses an infrequent stimulus embedded in a series of otherwise irrelevant frequent stimuli (called “oddball paradigm”) [ 21 ] . Patients are asked to identify and keep count of the rare stimuli (“oddballs”). The potential is evoked independent of the delivery modality used (visual, auditory, olfactory). A typical response peaks within 250–500 ms after the stimulus; a delay greater than 2.5 SD of the age-controlled mean indicates a dysfunctional response. Increases in the latency of responses are recorded in more than half of encephalo-pathic patients, but there were no signi fi cant differences between latencies of covert/minimal HE patients and unimpaired controls. Therefore, the P300ERP alone has limited diagnostic potential in this situation [ 16 ] .

The critical fl icker frequency (CFF) measures the maximum frequency at which a fl ickering light can still be perceived to fl icker [ 22 ] . As the frequency of light pulses is decreased, the frequency at which the fl ickering light no longer appears fused is called the CFF threshold. When using a threshold of 39 Hz, CFF strongly correlates with PHES and was shown to accurately diagnose 73–83% of covert/minimal HE patients, with higher sensitivity and speci fi city than use of P300ERP alone [ 23 ] . Covert/minimal HE patients were distinguished from unimpaired patients with a sensitivity of 55% and speci fi city of 91–100% [ 24 ] . CFF decreases with aging and can be affected by medications (sedatives, psychotropic drugs, caf-feine), and equipment (luminance and the color of the transmitted light) [ 5 ] . These variables should be taken into consideration—age-adjusted values should be used and should be compared with normative reference data. Though it requires patient cooperation and binocular vision, CFF is a simple, reproducible test that is not lim-ited by educational status, which allows for its widespread use in the diagnosis of covert HE [ 5 ] .

Smooth pursuit eye movements (SPEM) are the conjugate eye movements used to track smooth predictable trajectories of targets, such as small dots. Impairment of SPEM can be observed when patients can no longer track the dot trajectory accurately, leading to anticipatory and corrective saccadic movements which appear jerky or with a cogwheel pattern. This can occur in many clinical situations, including cirrhotics with hepatic encephalopathy. The degree of SPEM impairment re fl ects neuropsychiatric status. In patients with covert HE, there were clear dis-ruptions of smooth pursuit with interspersed anticipatory and corrective catch-up saccades [ 25 ] .


Other Markers of Cognitive Dysfunction

In addition to cognitive dysfunction, patients with covert HE are known to have a higher degree of extrapyramidal signs (EPS) and impairment in motor abilities, most likely due to manganese deposits in the basal ganglia which affect dopaminer-gic transmission [ 26 ] . Motor signs can include speech abnormalities, facial expres-sion, resting tremor, intention tremor, fi nger dexterity, rigidity, gait disturbance, and postural stability [ 27 ] . Patients with covert HE were more prone to the development of EPS, and there is a strong correlation between the severity of EPS and neuropsy-chological impairment [ 27 ] . However, these are nonspeci fi c and their analysis may be subjective. Metabolomics offers a quantitative examination of underlying meta-bolic derangements which occur with liver dysfunction. It is applicable to a broad spectrum of metabolites and has previously been used in the diagnosis of cancer, coronary artery disease and diseases of the CNS. Jimenez et al. studied cirrhotic patients with covert/minimal and found increased serum glucose and lactate levels along with decreased serum choline and lipids [ 28 ] . A detailed approach to metabo-nomics is needed with respect to covert/minimal HE before this can be used routinely.

Hepatic encephalopathy is not readily identi fi ed by structural abnormalities in the brain, although there is evidence that T1-pallidal hyperintensity may be seen on MR images [ 29 ] . However for the most part, neuroimaging serves to exclude other causes of brain disease in suspected HE when clinically indicated. Magnetic reso-nance spectroscopy is a study of metabolites in various brain regions, which shows an increase in glutamate/glutamine ratio with a compensatory decrease in myoinosi-tol and choline in patients with hepatic encephalopathy [ 30 ] . The limited availabil-ity and expense of an MRI scanner capable of two-dimensional MRS techniques limits the use of this modality.

Barriers Against Testing for Covert/Minimal HE and Consensus on Future Trials

Although the majority of clinicians agree that covert/minimal HE is a signi fi cant problem and requires outpatient testing, many barriers exist that prevent routine testing. The inability to have insurance companies reimburse for testing, the extra time added to outpatient visits, the lack of standardized norms, the reliance on psy-chological expertise to administer and interpret test results, and the expensive and copyrighted testing procedures are all contributors [ 31 ] .

In the round table discussion at the 14th ISHEN meeting, it was concluded that trials involving minimal/covert HE patients should be randomized and pla-cebo-controlled. Patient populations in such trials should exclude patients receiv-ing treatment for overt HE, and those with prior episodes of overt HE, as this was a confounder in the classi fi cation of performance on neuropsychological tests.


In single-center or proof-of-concept studies, test operators should be experienced in the use, administration, and interpretation of that particular test(s) and appropriate normative reference data should be available. The test(s) should also be validated for use in the selected patient population. In multi-center trials, there needs to be more information on the interchangeability and standardization of tests; in the interim, the use of two or more validated tests are recommended [ 5 ] .

References

1. Ferenci P, Lockwood A, Mullen K, Tarter R, Weissenborn K, Blei AT. Hepatic encephalopathy—de fi nition, nomenclature, diagnosis, and quanti fi cation: fi nal report of the working party at the 11th World Congresses of Gastroenterology, Vienna, 1998. Hepatology. 2002;35(3):716–21.

2. Hassanein T, Blei AT, Perry W, et al. Performance of the hepatic encephalopathy scoring algorithm in a clinical trial of patients with cirrhosis and severe hepatic encephalopathy. Am J Gastroenterol. 2009;104(6):1392–400.

3. Bajaj JS, Wade JB, Sanyal AJ. Spectrum of neurocognitive impairment in cirrhosis: implica-tions for the assessment of hepatic encephalopathy. Hepatology. 2009;50(6):2014–21.

4. Cordoba J. New assessment of hepatic encephalopathy. J Hepatol. 2011;54(5):1030–40. 5. Bajaj JS, Cordoba J, Mullen KD, et al. Review article: the design of clinical trials in hepatic

encephalopathy—an International Society for Hepatic Encephalopathy and Nitrogen Metabolism (ISHEN) consensus statement. Aliment Pharmacol Ther. 2011;33(7):739–47.

6. Bajaj JS. Review article: the modern management of hepatic encephalopathy. Aliment Pharmacol Ther. 2010;31(5):537–47.

7. Weissenborn K, Ennen JC, Schomerus H, Ruckert N, Hecker H. Neuropsychological charac-terization of hepatic encephalopathy. J Hepatol. 2001;34(5):768–73.

8. Randolph C, Hilsabeck R, Kato A, et al. Neuropsychological assessment of hepatic encephal-opathy: ISHEN practice guidelines. Liver Int. 2009;29(5):629–35.

9. Dhiman RK, Kurmi R, Thumburu KK, et al. Diagnosis and prognostic signi fi cance of minimal hepatic encephalopathy in patients with cirrhosis of liver. Dig Dis Sci. 2010;55(8):2381–90.

10. Garavan H, Ross TJ, Stein EA. Right hemispheric dominance of inhibitory control: an event-related functional MRI study. Proc Natl Acad Sci U S A. 1999;96(14):8301–6.

11. Bajaj JS, Hafeezullah M, Franco J, et al. Inhibitory control test for the diagnosis of minimal hepatic encephalopathy. Gastroenterology. 2008;135(5):1591–600.e1591.

12. Bajaj JS, Hafeezullah M, Hoffmann RG, Saeian K. Minimal hepatic encephalopathy: a vehicle for accidents and traf fi c violations. Am J Gastroenterol. 2007;102(9):1903–9.

13. Bajaj JS, Saeian K, Schubert CM, et al. Minimal hepatic encephalopathy is associated with motor vehicle crashes: the reality beyond the driving test. Hepatology. 2009;50(4):1175–83.

14. Amodio P, Ridola L, Schiff S, et al. Improving the inhibitory control task to detect minimal hepatic encephalopathy. Gastroenterology. 2010;139(2):510–8.e511–2.

15. Mardini H, Saxby BK, Record CO. Computerized psychometric testing in minimal encephal-opathy and modulation by nitrogen challenge and liver transplant. Gastroenterology. 2008;135(5):1582–90.

16. Montagnese S, Amodio P, Morgan MY. Methods for diagnosing hepatic encephalopathy in patients with cirrhosis: a multidimensional approach. Metab Brain Dis. 2004;19(3–4):281–312.

17. Amodio P, Pellegrini A, Ubiali E, et al. The EEG assessment of low-grade hepatic encephal-opathy: comparison of an arti fi cial neural network-expert system (ANNES) based evaluation with visual EEG readings and EEG spectral analysis. Clin Neurophysiol. 2006;117(10): 2243–51.

18. Montagnese S, Jackson C, Morgan MY. Spatio-temporal decomposition of the electroencepha-logram in patients with cirrhosis. J Hepatol. 2007;46(3):447–58.


19. Kullmann F, Hollerbach S, Holstege A, Scholmerich J. Subclinical hepatic encephalopathy: the diagnostic value of evoked potentials. J Hepatol. 1995;22(1):101–10.

20. Zeneroli ML, Pinelli G, Gollini G, et al. Visual evoked potential: a diagnostic tool for the assessment of hepatic encephalopathy. Gut. 1984;25(3):291–9.

21. Blauenfeldt RA, Olesen SS, Hansen JB, Graversen C, Drewes AM. Abnormal brain processing in hepatic encephalopathy: evidence of cerebral reorganization? Eur J Gastroenterol Hepatol. 2010;22(11):1323–30.

22. Kircheis G, Wettstein M, Timmermann L, Schnitzler A, Haussinger D. Critical fl icker frequency for quanti fi cation of low-grade hepatic encephalopathy. Hepatology. 2002;35(2):357–66.

23. Sharma P, Sharma BC, Puri V, Sarin SK. Critical fl icker frequency: diagnostic tool for minimal hepatic encephalopathy. J Hepatol. 2007;47(1):67–73.

24. Romero-Gomez M, Cordoba J, Jover R, et al. Value of the critical fl icker frequency in patients with minimal hepatic encephalopathy. Hepatology. 2007;45(4):879–85.

25. Montagnese S, Gordon HM, Jackson C, et al. Disruption of smooth pursuit eye movements in cir-rhosis: relationship to hepatic encephalopathy and its treatment. Hepatology. 2005;42(4):772–81.

26. Company L, Zapater P, Perez-Mateo M, Jover R. Extrapyramidal signs predict the develop-ment of overt hepatic encephalopathy in patients with liver cirrhosis. Eur J Gastroenterol Hepatol. 2010;22(5):519–25.

27. Jover R, Company L, Gutierrez A, et al. Minimal hepatic encephalopathy and extrapyramidal signs in patients with cirrhosis. Am J Gastroenterol. 2003;98(7):1599–604.

28. Jimenez B, Montoliu C, MacIntyre DA, et al. Serum metabolic signature of minimal hepatic encephalopathy by (1)H-nuclear magnetic resonance. J Proteome Res. 2010;9(10):5180–7.

29. Cordoba J, Sanpedro F, Alonso J, Rovira A. 1H magnetic resonance in the study of hepatic encephalopathy in humans. Metab Brain Dis. 2002;17(4):415–29.

30. Rovira A, Alonso J, Cordoba J. MR imaging fi ndings in hepatic encephalopathy. AJNR Am J Neuroradiol. 2008;29(9):1612–21.

31. Bajaj JS, Etemadian A, Hafeezullah M, Saeian K. Testing for minimal hepatic encephalopathy in the United States: an AASLD survey. Hepatology. 2007;45(3):833–4.


Keywords Electroencephalogram • Triphasic waves • EEG quantitative analysis • EEG spectral analysis • Prognosis • Event-related response • Cognitive potential • P300 • Neurophysiology

Principles of EEG Functioning

The electroencephalogram (EEG) represents the time-course of the difference of electric potentials that are recorded on the scalp by electrodes placed over speci fi c sites, which are called derivations, with respect to a reference derivation. The EEG tracing ultimately depends on the electric current generated by the synchronized postsynaptic potentials of thousands of pyramidal cells of the fourth layer of the brain cortex that are placed under the recording derivations. Unlike the ECG, it is not possible for the EEG to have a reference derivation without any electric activity, either on the scalp (cephalic derivation) or outside the scalp (extra-cephalic deriva-tion). The electric activity of the reference derivation can only be minimized after EEG recording (post-processing) by mathematical work-up [ 1 ] . Alternatively to display the EEG as it is has been recorded, the EEG activity can be displayed in a bipolar way (i.e. the time-course of the difference of electric potential between two cephalic derivations), or as the voltage difference between the considered derivation and the average of all the other derivations.

The EEG has low spatial resolution; in contrast, it has great time resolution. This property allows the use of the EEG to detect the time-course of the electric poten-tials that are evoked by sensory or cognitive stimuli, once the background EEG activity is removed by mathematical handling of the signals.

P. Amodio , MD (*) Department of Medicine , University Hospital of Padova , Via Giustiniani, 2 , Padova 35128 , Italy e-mail: [email protected]

Chapter 9 The Electroencephalogram in Hepatic Encephalopathy

Piero Amodio

114 P. Amodio

The cortical neuronal electric activity that produces the EEG is modulated by both physiological and pathological diencephalic and brain-stem in fl uences. In addition, the electric activity is extremely sensitive to metabolic and toxic in fl uences; therefore, the EEG is a reliable tool to detect metabolic brain dysfunction, even if in clinical practice the EEG is manly used to detect the abrupt, abnormal electric dis-charges characterizing epilepsy.

Clinical Scenario

The EEG is a tool that provides a functional assessment of the nervous system; therefore, its domain is similar to that of clinical examination and complementary to that of neuroimaging. When compared to clinical examination, the EEG provides more quantitative assessment, which is potentially amenable for follow-up and remains interpretable in non-cooperative patients.

In a few circumstances, the EEG is highly useful to diagnose the disease causing confusion or comatose patterns. Examples are non-convulsive seizures, viral encephalitis and spongiform encephalitis. Highly indicative patterns are also pro-vided by stroke, subdural hematoma and malingering (Fig. 9.1 ).

In other cases, the EEG, similar to other functional evaluations (and similar to clinical evaluation), is generally non-speci fi c and analogous patterns can be found

Fig. 9.1 In this patient, hyperammonaemia and coma occurred after surgical porto-systemic shunt. The diagnosis of HE was ruled out by the electroencephalogram (EEG) that disclosed a massive suffering on the right hemisphere: a massive right stroke had occurred during the surgical procedure

1159 The Electroencephalogram in Hepatic Encephalopathy

in a wide variety of pathophysiological events, from transient, primary, subcortically or metabolically induced cortical dysfunction to irreversible cortical problems. Nonetheless, in these conditions, the pattern of EEG alterations re fl ects the severity of underlying brain dysfunction. Therefore, the objection that EEG is useless for the diagnosis of HE, because it is relatively unspeci fi c, is meaningless and depends on the confusion between the concept of differential diagnosis (diagnosis of a disease vs. another disease) and of disease severity.

EEG Patterns in HE

Therefore, apart from the possibility that the EEG discloses another cause of delirium/coma in a patient with cirrhosis, the EEG provides useful information to quantify brain dysfunction in hepatic encephalopathy (HE). In fact, HE is associated with the occurrence of EEG patterns that present a relationship, albeit rough, with the behav-ioural features of the syndrome, as was proven by Parsons-Smith et al. [ 2 ] more than 50 years ago. This rough correlation with the behavioural feature does not imply that EEG re fl ects brain dysfunction at a lower level than behaviour: simply they re fl ect two different, albeit correlated, domain of brain function. In addition, since the behav-ioural expression of neurologic disorder is highly in fl uenced by the premorbid condi-tions of the patient, by his/her will to cooperate and by other confounding factors, the EEG can re fl ect biological alterations more than behaviour ability [ 3 ] .

The fi rst EEG sign of HE is a low-frequency alpha rhythm disturbed by random waves in the theta range over both hemispheres. A certain degree of frontalization of alpha activity was proven by quanti fi ed analysis of EEG performed by short epoch, dominant activity, cluster analysis (SEDACA ) [ 4 ] . Waves in the theta band are generally observed in the temporal areas, but they may also be observed in the frontal areas or diffusely on the scalp.

The increase in HE severity causes a progressive increase in theta band activity that diffuses over both hemispheres along with high voltage arrhythmic delta band activity. At this stage, triphasic waves are usually discernable. These are synchronous waves with anterior dominance that appear in groups or runs, have a fronto-occipital lag time, and are superimposed on the basic slow theta–delta rhythm. Although triphasic waves are frequent in HE, they are not speci fi c and can also be observed in other types of metabolic encephalopathies (uremic, hyponatremia) or in drug intoxi-cations (lithium, valproate, baclofen) [ 5– 7 ] .

Burst of high voltage frontal intermittent delta activity (FIRDA) or occipital intermittent delta activity (OIRDA) can occur. In addition, the EEG reactivity to eye opening (block of alpha rhythm) progressively decreases in parallel with the increase in HE severity. A further increase in HE severity, in comatose patients, is character-ized by an EEG tracing formed only by high voltage arrhythmic delta waves; fi nally in severe coma, arrhythmic delta activity decreases both in frequency and amplitude until reaching the shape of a fl at EEG [ 8 ] . Once a fl at EEG is reached, the information obtainable by the EEG is saturated and further useful information on brain activity can be obtained by somatosensory evoked potentials (SSEP) [ 9 ] .

116 P. Amodio

The Objective Quanti fi cation of EEG in HE

The patterns of EEG in HE are clear for an expert; however, the inter-observer repeatability of a classi fi cation based on pattern recognition is poor [ 10 ] . A simple way to improve the repeatability of EEG evaluation of HE is provided by the visual measuring of basic background frequency on posterior derivations [ 10 ] . This approach is limited by the fact that the fi rst stages of HE are characterized by the mixing of rare activities in the theta range to alpha rhythm, therefore producing high subjectivity in the estimation of basic frequency. Similarly, in more severe cases of HE, when theta and delta activities are mixed together, the estimation of basic rhythm is unreliable. These limitations can be overcome by objective quanti fi cation of digitalized EEG. The simplest way to obtain proper quanti fi cation is provided by the spectral analysis of about 60–90 s of bipolar EEG signals from posterior deriva-tions [ 11 ] . In addition, temporal-occipital (T3-O1 and T4-O2) as well as central-occipital (Cz-O1, Cz-O2) and biparietal (P3-P4) or parieto-occipital derivations are useful [ 11, 12 ] . Spectral analysis can be performed either by non-parametric (fast Fourier transform) or parametric (autoregressive) procedures [ 13 ] . Using spectral analysis, a simple quanti fi cation of EEG alteration in HE is possible: at the begin-ning theta activity increases, later a decrease of the “barycentre” of the frequencies (expressed by the mean dominant frequency (MDF) 1 ) occurs and, lastly, an increase in delta activity is detectable (Fig. 9.2 ; Table 9.1 ).

A stage of low power, very low delta frequency occurs in severe coma, before the stage of fl at EEG: spectral analysis can be misleading in these circumstances and no study using quanti fi ed EEG on this stage of HE has been published.

A possible limitation of the current criteria for quanti fi cation of EEG in HE is given by the fact that they consider only background activity from few derivations, missing the information coming from triphasic waves or the relationship across rhythms and their spatial distribution. Other modes/methods of quanti fi cation can be obtained by more sophisticated techniques, such as principal component analy-sis, SEDACA, neural network procedures and coherency esteem, which can par-tially overcome these limitations [ 4, 10, 14 ] .

Clinical Information from the EEG in HE

The EEG quanti fi cation provides good assessment both of the risk for development of overt HE and mortality at 1-year follow up (Table 9.2 ) in patients who do not display symptoms of overt HE at the time of examination. These observations provide

1 The MDF is given by the ratio of the sum of each frequency band multiplied by its electric power over the total electric power of the interval of examined frequencies.


evidence that EEG is a valuable tool to investigate HE in clinical practice, even in routine examination of outpatients with cirrhosis. In fact, EEG has the advantage to provide data that are independent of patient’s cooperation and education level: as against psychometric evaluation and is complementary to it for evaluation of patients with covert HE.

EEG has proven to have higher predictive value on survival in minimal HE subjects compared to psychometric testing and cognitive evoked potentials (P300 latency) [ 15 ] .

Fig. 9.2 The classi fi cation of EEG alterations based on spectral analysis: grade 1 is characterized by an increase in theta activities ( ³ 35%), grade 2 by a signi fi cant reduction of the mean dominant frequency (MDF) (<6.8 Hz) without a massive increase in delta activity, grade 3 by a reduction of the MDF with a massive increase in delta activity ( ³ 49%). In the circle , a triphasic wave pattern is shown. In severe coma, the spectral measures lose their meaning: the activity tends to disappear, in the fi gure the apparent activity is due to gasping (personal observations, classi fi cation according to Amodio et al. [ 12 ] )

Table 9.1 EEG classi fi cation of HE based on spectral measures from bipolar biparietal deriva-tions (P3-P4)

Grade MDF Theta relative power (%) Delta relative power (%)

Normal >6.8 <35 <49 Grade 1 >6.8 ³ 35 Grade 2 £ 6.8 ³ 35 <49 Grade 3 £ 6.8 Irrelevant ³ 49

Reprinted from Amodio et al. [ 12 ] ©1999. With permission from Elsevier

118 P. Amodio

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In addition, even minor changes in EEG dynamics correlate with changes on psy-chometric test fi ndings as demonstrated by our group [ 12 ] .

The EEG is particularly appropriate to show objectively the changes in brain function following treatment of HE (Fig. 9.3 ). The improvement related to liver transplantation is also extremely remarkable [ 16 ] and EEG may have a role in the evaluation of post-transplant neurological complications [ 17 ] .

Obviously, being a functional measure and similar to psychometric investigation, subtle EEG changes in patients with a low pre-test probability of HE (well pre-served liver function and absence of porto-systemic shunt) should be proven to depend on HE and not to other causes of brain dysfunction. It should be noted, however, that this is true also for psychometric dysfunction in patients with a low a priori probability of HE: other causes of mild cognitive impairment different from HE should be ruled out.

EEG Responses Evoked by Cognitive Tasks

An alternative method to use the EEG for the study of HE is the extraction of cognitive potentials related to execution of a cognitive task. Of these, the P300 elic-ited by the oddball paradigm was the most widely used for the study of the mildest

Fig. 9.3 The massive improvement of EEG features after a session of MARS in a patient with HE in acute on chronic liver failure. On the left , before treatment, a very slow EEG tracing with a high number of triphasic waves ( circles ), after treatment the mental state improves (from grade 2–3 to grade 1 HE) and the EEG tracing shows the disappearance of triphasic waves (personal observation)

120 P. Amodio

manifestations of HE. This technique has limited clinical applicability [ 9 ] , and its clinical utility in comparison with the EEG for the detection and monitoring of HE is doubtful [ 15, 18 ] . Other evoked responses, such as lateralized readiness potential allow distinction between selective and executive phase of a response [ 19 ] .

Conclusions

In conclusion, the EEG, especially with quantitative techniques, provide useful information, independent of educational bias, for the assessment, follow up and monitoring treatment of individuals with cirrhosis with covert, mild or severe HE.

References

1. Hjorth B. An on-line transformation of EEG scalp potentials into orthogonal source deriva-tions. Electroencephalogr Clin Neurophysiol. 1975;39(5):526–30.

2. Parsons-Smith BG, Summerskill WHJ, Dawson AM, Sherlock S. The electroencephalograph in liver disease. Lancet. 1957;2:867–71.

3. Montagnese S, Biancardi A, Schiff S, et al. Different biochemical correlates for different neu-ropsychiatric abnormalities in patients with cirrhosis. Hepatology. 2010;53(2):558–66.

4. Montagnese S, Jackson C, Morgan MY. Spatio-temporal decomposition of the electroencepha-logram in patients with cirrhosis. J Hepatol. 2007;46(3):447–58.

5. Bickford RG, Butt HR. Hepatic coma: the electroencephalographic pattern. J Clin Invest. 1955;34: 790–9.

6. Kaplan PW. The EEG in metabolic encephalopathy and coma. J Clin Neurophysiol. 2004;21(5): 307–18.

7. Karnaze DS, Bickford RG. Triphasic waves: a reassessment of their signi fi cance. Electroencephalogr Clin Neurophysiol. 1984;57(3):193–8.

8. Amodio P, Gatta A. Neurophysiological investigation of hepatic encephalopathy. Metab Brain Dis. 2005;20(4):369–79.

9. Guerit JM, Amantini A, Fischer C, et al. Neurophysiological investigations of hepatic enceph-alopathy: ISHEN practice guidelines. Liver Int. 2009;29(6):789–96.

10. Amodio P, Pellegrini A, Ubiali E, et al. The EEG assessment of low-grade hepatic encephal-opathy: comparison of an arti fi cial neural network-expert system (ANNES) based evaluation with visual EEG readings and EEG spectral analysis. Clin Neurophysiol. 2006;117(10): 2243–51.

11. Van der Rijt CC, Schalm SW, De GG, De VM. Objective measurement of hepatic encephal-opathy by means of automated EEG analysis. Electroencephalogr Clin Neurophysiol. 1984;57(5):423–6.

12. Amodio P, Marchetti P, Del Piccolo F, et al. Spectral versus visual EEG analysis in mild hepatic encephalopathy. Clin Neurophysiol. 1999;110(8):1334–44.

13. Amodio P, Orsato R, Marchetti P, et al. Electroencephalographic analysis for the assessment of hepatic encephalopathy: comparison of non-parametric and parametric spectral estimation techniques. Neurophysiol Clin. 2009;39(2):107–15.

14. Onton J, Wester fi eld M, Townsend J, Makeig S. Imaging human EEG dynamics using inde-pendent component analysis. Neurosci Biobehav Rev. 2006;30(6):808–22.


15. Saxena N, Bhatia M, Joshi YK, Garg PK, Dwivedi SN, Tandon RK. Electrophysiological and neuropsychological tests for the diagnosis of subclinical hepatic encephalopathy and predic-tion of overt encephalopathy. Liver. 2002;22(3):190–7.

16. Epstein CM, Riether AM, Henderson RM, Cotsonis GA. EEG in liver transplantation: visual and computerized analysis. Electroencephalogr Clin Neurophysiol. 1992;83(6):367–71.

17. Steg RE, Wszolek ZK. Electroencephalographic abnormalities in liver transplant recipients: practical considerations and review. J Clin Neurophysiol. 1996;13(1):60–8.

18. Amodio P, Valenti P, Del PF, et al. P300 latency for the diagnosis of minimal hepatic enceph-alopathy: evidence that spectral EEG analysis and psychometric tests are enough. Dig Liver Dis. 2005;37(11):861–8.

19. Schiff S, Vallesi A, Mapelli D, Orsato R, Pellegrini A, Umilta C, Gatta A, Amodio P. Impairment of response inhibition precedes motor alteration in the early stage of liver cirrhosis: a behavioral and electrophysiological study. Metab Brain Dis. 2005;20:381–92.


Keywords Magnetic resonance • Ammonia • Manganese • Brain edema • Brain atrophy

Abbreviations

ADC Apparent diffusion coef fi cient Cho Choline containing compounds DWI Diffusion-weighted imaging FLAIR Fast fl uid-attenuated inversion recovery fMRI Functional magnetic resonance imaging Glx Glutamine/glutamate HE Hepatic encephalopathy LT Liver transplantation MR Magnetic resonance MT Magnetization transfer PET Positron emission tomography SPECT Single-photon emission computed tomography WML White matter focal T2-weighted lesions

R. García-Martínez, PhD • J. Córdoba, PhD (*) Liver Unit, Department of Internal Medicine , Vall d’Hebron Hospital , Barcelona 08035 , Spain e-mail: [email protected]; [email protected]

Chapter 10 Brain Imaging in Hepatic Encephalopathy

Rita García-Martínez and Juan Córdoba

124 R. García-Martínez and J. Córdoba

Introduction

Neuroimaging techniques provide the possibility to assess the central nervous system of patients that experience hepatic encephalopathy (HE). There are many available methods that can be applied, which are classi fi ed according to the physical principles of the technique (e.g., computed tomography, magnetic resonance (MR), positron emission tomography [PET]). Some techniques (conventional T1 or T2 MR-imaging) are considered standard diagnostic methods that are available in most centers and are very useful in the evaluation of acute confusional syndrome, because they allow exclusion of other neurologic disease and may reveal typical signs of HE [ 1 ] . Other techniques have been relevant to understand the pathogenesis of HE and may become of clinical interest in the future [ 2 ] . The most common presenta-tion of HE is in cirrhotic patients (HE type-C). This population is also the most frequently included in neuroimaging studies. One of the limitations of the studies that have been performed is the dif fi culty to separate the disturbances caused by liver failure (without impact on brain function) from those that are directly involved in HE. In addition, these patients exhibit frequent co-morbidities that may partici-pate in the neurological manifestations, such as cerebrovascular disorders or alco-hol-induced injury. This chapter aims to review the contribution of neuroimaging techniques to understanding the pathogenesis, diagnosis and monitoring of HE, emphasizing the role of magnetic resonance.

Brain Features That Are Relevant for Neuroimaging

Manganese Accumulation

Liver failure may lead to the accumulation in the brain of manganese, a metal that is excreted in the bile. Increased blood levels are seen in the presence of large portal-systemic shunts. Manganese shows a preference to accumulate in some areas of the brain, such as the basal ganglia, due to the presence of speci fi c carriers that relate to the participation of manganese in certain metabolic pathways. Manganese has a key role in the normal functioning of several enzymes including mitochondrial superoxide dismutase [ 3 ] , glutamine synthetase, and phosphoenolpyruvate car-boxykinase [ 4 ] . The metal was fi rst considered to be neurotoxic more than 150 years ago, when workers employed in grinding black oxide of manganese devel-oped an unsteady gait and muscle weakness [ 5 ] . Since that time, many cases of manganese neurotoxicity (manganism), a neurological disease characterized by psychological and neurological abnormalities has been reported [ 6 ] . It has some similarities to Parkinson’s disease and has been reported particularly in miners, smelters, welders, and workers involved in the alloy industry. Typically, patients exhibit extrapyramidal changes that include hypokinesia, rigidity, and tremor.

12510 Brain Imaging in Hepatic Encephalopathy

Ammonia

Patients with liver failure or portal-systemic shunting have elevated levels of circulating ammonia, which enters the brain through the blood–brain barrier, increasing the brain–blood ammonia concentration ratio. PET studies using 13 NH

3

provide evidence of the increased blood–brain ammonia transfer and brain ammo-nia utilization rates in patients with chronic liver failure [ 7 ] . This hyperammone-mia results in profound astrocyte changes, including Alzheimer type II changes seen commonly in longstanding type C HE and astrocyte swelling in acute HE. One of the effects of ammonia is inducing a rise in brain glutamine in astrocytes, the only cell in the brain that has glutamine synthetase. The rise in glutamine may cause an increase in the intracellular osmolality and induce compensatory meta-bolic changes to counteract the osmotic imbalance induced by intra-astrocytic glu-tamine accumulation. In chronic liver failure, there is enough time for activation of effective compensatory mechanisms of cellular adaptation to the osmotic changes: glial accumulation of one organic osmolyte, glutamine, should lead to the loss of other organic osmolytes, such as myo-inositol, taurine, and choline. This osmo-regulatory mechanism may account for the protection against massive edema in chronic liver failure [ 8 ] .

Brain Edema

Brain water secondary to severe liver failure [ 9 ] and to hyperammonemia (urea cycle disorders) has been clearly documented. A large increase in brain water which results in intracranial hypertension is seen more often but not exlusively in patients with fulminant hepatic failure [ 10 ] . The relevance of more subtle cerebral edema is a matter of much debate, primarily because this is a common fi nding in patients with HE in chronic liver disease. Experimental studies indicate that brain edema is mostly located in the astrocytes, but may also be located in the interstitial compartment and be secondary to disturbances in the blood–brain barrier [ 11 ] .

Brain Atrophy

Neuropathological studies have documented loss of brain tissue in chronic liver failure, especially in patients with long-lasting HE manifestations and large porto-systemic shunts [ 12 ] . This is usually referred to as acquired hepatocerebral degen-eration [ 13 ] , and it may have milder forms that are more common than previously recognized.


Magnetic Resonance: T1 High Signal Intensity

Since the introduction of MR imaging in clinical practice, it has been well described that the majority of patients with cirrhosis or portal-systemic shunts exhibit a bilat-eral, symmetrical high signal intensity at the globus pallidus and substantia nigra (Fig. 10.1 ) [ 14 ] . The signal may increase after performing a portal-systemic shunting with transjugular intrahepatic portal-systemic stent placement [ 15 ] and reverses after normalization of liver function [ 16 ] or after occlusion of congenital portal-systemic shunts [ 17 ] . The most plausible explanation for the increased T1 signal is a rise in manganese concentration (a paramagnetic substance) in the CNS, with preferential deposition in the globus pallidus [ 18 ] . The arguments favoring the “manganese hypothesis” include the dramatic blood and CSF manganese increase in patients with cirrhosis and pallidal hyperintensities [ 19 ] , normalization of MR signal abnormalities and manganese levels after liver transplantation [ 16 ] , and the several-fold increase in manganese concentrations from pallidal samples obtained at autopsy in cirrhotic patients [ 20 ] .

This manganese-related MR signal abnormality has also been described in non-cirrhotic patients, such as those receiving total parenteral nutrition [ 21 ] , patients with occupational exposure to manganese from welding [ 22 ] , and patients with noncirrhotic portal vein thrombosis or congenital portal-systemic bypass and no intrinsic hepatocellular disease [ 23 ] . In all these situations, the MR signal changes resolve after discontinuation of manganese intake [ 21 ] . Similar fi ndings were observed in a patient with Alagille’s syndrome [ 24 ] , an autosomal dominant disorder characterized by cholestasis, intrahepatic bile duct paucity, end-stage liver disease, and elevated blood manganese.

Bilateral basal ganglia T1 signal changes have also been observed in several conditions unrelated to increased brain manganese levels (e.g., nonketotic hyperg-lycemic episodes, hypoxic-ischemic encephalopathy, basal ganglia calci fi cation, neuro fi bromatosis type I, and Japanese encephalitis), although the high signal inten-sity occurring in these conditions does not usually show symmetrical, predomi-nantly pallidal involvement [ 25 ] .

Although pallidal hyperintensities are found in about 90% of cirrhotic patients, these signal alterations are not closely linked to the presence of HE. It has been shown that cirrhotic patients with no clinical, neuropsychological, or neurophysi-ological signs of HE can also show severe signal alterations, while others with manifest HE may present only slight signal alterations [ 26– 28 ] . Moreover, longitu-dinal studies have shown quick regression of HE after liver transplantation, while T1 signal abnormalities need up to 1 year to resolve (Fig. 10.1 ) [ 28, 29 ] . The clinical-MR discrepancy may, therefore, be explained by the fact that T1 high signal inten-sity cannot be used as a quantitative measure of tissue manganese, as it represents only semiquantitative measurement of abnormal manganese deposition. Thus, it is possible that manganese accumulation participates in the pathogenesis of HE only after reaching a certain threshold, which may not be clearly identi fi ed by MR. An interesting study supports the concept that the presence of parkinsonism is related


to the extension of the high signal intensity to midbrain structures (particularly substantia nigra), as this MR feature is unique to patients with cirrhosis-related parkinsonism. These data provide a good explanation for the apparent clinical–radiological discrepancies. The current understanding is that T1 high signal inten-sity identi fi es the deposition of paramagnetic substances that participate in the pathogenesis of chronic rigidity-akinesia. From a clinical perspective, the value of T1 high signal intensity in the diagnosis of chronic neurological manifestations has not been assessed. However, the clinical experience indicates that the absence of T1 high signal intensity is a strong argument against interpreting the neurological manifestations as secondary to liver failure [ 30 ] .

1 H-MR Spectroscopy: Metabolites

MR detects the relaxation properties of some atoms (most usual isotopes are 1 H, 31 P, 23 Na, 13 C) in strong magnetic fi elds and according to how the data are processed can generate high-resolution images or spectrum of several metabolites that contain the atoms that are studied. The spectrum contains a series of metabolites that are displayed as peaks at different frequencies (Fig. 10.2 ). 1 H magnetic reso-nance spectroscopy shows relative to creatine an increase in glutamine/glutamate (Glx) signal and a decrease of choline containing compounds (Cho) and myo-inositol. Abnormalities in the Glx signal have been interpreted as an increase

Fig. 10.1 Transverse T1-weighted MR images of the brain in chronic liver failure. Observe the bilateral and symmetric high T1 signal change involving the globus pallidus (white arrow)


in brain glutamine secondary to the metabolism of ammonia in astrocytes. Disturbances of Cho and myo-inositol have been interpreted as a compensatory response to the increase in intracellular osmolality caused by the accumulation of glutamine in astrocytes. Disturbances in MR-spectroscopy have been proposed as a signature of HE because the severity of these changes has been associated with HE [ 31 ] . The origin of these disturbances appears to be ammonia. In patients with cirrhosis subjected to ammonia load, 1 H-MRS consistently show increases in the Glx signal accompanied by myo-inositol depletion, and decreases in the choline signal [ 32– 34 ] .

Longitudinal studies have assessed the evolution of 1 H-MR spectroscopy abnormalities after liver transplantation (LT) and demonstrated their reversibility [ 26, 27, 34 ] . However, time to normalization for each metabolite is different. The Glx peak normalizes within the fi rst 1–2 months (except in cases of high peaks) after liver transplant, whereas myo-inositol normalizes slower, and may take 3–7 months. This reversibility precedes the disappearance of pallidal hyperintensity after LT and correlates with improvements in neurologic manifestations [ 35 ] .

The data provided by MR-spectroscopy may be re fi ned using a two-dimensional analysis. In a study performed in patients with minimal HE, a decrease in myo-inositol was the most accurate predictor for minimal HE compared with MR imaging or neuropsychological tests [ 36 ] . The decrease in the peak of myo-inositol

Fig. 10.2 MR of the brain in a patient that exhibits grade II HE that was repeated 6 weeks later when the patient exhibited minimal HE. MR-spectroscopy shows an increase in the peaks that contain glutamine (Glx) and a decrease of the peaks containing myo-inositol (mIns) and choline (Cho). After improving HE, the peak of Glx decreased and the peak of mIns increased. Other peaks correspond to n -acetyl-aspartate (NAA), and creatine (Cr)


is exacerbated by hyponatremia, as can be expected from the functional role of myo-inositol. In a prospective study of prognostic factors for development of overt HE among 61 cirrhotic patients, low levels of myo-inositol were associated to hyponatremia, which was the major risk factor of overt HE [ 37 ] . However, these metabolic changes have also been observed in patients with cirrhosis and neither clinical nor psychometric or neurophysiologic signs of cerebral dysfunction. The current understanding is that the increase in brain Glx and the decrease in myo-inositol re fl ect the neurometabolic changes associated with HE, but they are not perfect indicators of neuronal function and clinical manifestations.

Magnetic Resonance: Brain Water

Standard MR may reveal changes in the volume of brain parenchyma, such as decrease in the size of ventricles, cortical sulcal effacement, and attenuation of the signal intensity of brain parenchyma. However, mild to moderate accumulation of water may not be apparent. Studies comparing the brain of patients before and after liver transplantation show an increase in the size of the ventricles and a decrease in white matter lesions that are compatible with resolution of mild edema after liver transplantation [ 38 ] . The increase in brain water has been con fi rmed with water quanti fi cation maps, a sophisticated method of MR that measures directly the amount of water in the tissue [ 39 ] . Conventional MR imaging techniques, such as T2-weighted signal-intensity reveal no abnormalities. However, other MR imaging sequences have been applied in the recent years for the assessment of brain in liver diseases. These include magnetization transfer imaging, fast fl uid-attenuated inver-sion recovery (FLAIR) imaging, and diffusion-weighted imaging (DWI), which are more sensitive to detect changes in brain water. These studies support the hypothe-sis of low-grade diffuse brain edema in patients with chronic liver disease.

Magnetization Transfer

Magnetization transfer (MT) imaging is based on the interaction between protons in a relatively free environment and those in which movement is restricted [ 40 ] . Exchange of this saturated magnetization with free water reduces the signal intensity observed in the subsequent MR imaging. The degree of signal-intensity loss depends on the attenuation of the macromolecules in the interrogated tissue. Different studies assessed MT ratios in the brain of patients with cirrhosis [ 27, 41, 42 ] showing all of them had low values in different regions of the brain. Compared to other diseases, the decrease in MT ratio is mild (10%) and without signi fi cant abnor-malities on conventional T1- and T2-weighted images. In addition, this decrease returns to almost normal values after liver transplant in parallel with improvement in neuropsychological alterations [ 27 ] , supporting the hypothesis of changes in brain water rather than reduction in brain tissue.


FLAIR

This MR imaging sequence is used to nullify signal from fl uids, such as cerebrospinal fl uid. In the subsequent image, abnormalities that are normally covered by bright fl uid signal can be revealed. Several studies have assessed the brain of cirrhotic patients with this technique [ 43– 46 ] . Two fi ndings emerge from these studies:

(a) High signal intensity along the hemispheric white matter or around the corti-cospinal tract was observed in cirrhotic patients with an improvement after LT [ 43 ] or after resolution of the episode of HE (Fig. 10.3 ) [ 46 ] . Although similar fi ndings have been observed in diseases which pathologic bases are axonal loss or demyelination, several factors lead to reject this interpretation and to support the presence of mild brain edema in cirrhotic patients. The progressive normal-ization in prospective follow-up in parallel with improvement of cognitive function, normal values of neuronal marker ( N -acetyl-aspartate/creatine) in 1 H-MR spectroscopy, and lack of other signs concordant with loss of brain tissue in other MR imaging sequences are more consistent with the concept of low-grade brain edema.

(b) White matter focal T2-weighted lesions (white matter lesions [WMLs]) are attributed to degenerative small-vessel cerebrovascular disease (Fig. 10.4 ). They are often seen in MR images of general population over 60 years old, with a progressive increase in their volume and associated to cognitive decline [ 47 ] . In patients with cirrhosis, these lesions showed a decrease in their volume after improvement of HE [ 45 ] and after liver transplant [ 38, 44 ] . The shrinkage of

Fig. 10.3 Serial transverse T2-weighted fast-FLAIR images obtained in a patient with liver cir-rhosis during an episode of hepatic encephalopathy. Observe the symmetric areas of increased signal along the corticospinal tract in both cerebral hemispheres ( upper panel ). This signal abnor-mality almost completely reversed after liver transplant ( lower panel )


these lesions is closely associated with the improvement of neuropsychological function and this is the opposite behavior observed in WMLs attributable to small-vessel cerebrovascular disease. The most plausible explanation for this feature is the existence of brain edema.

Diffusion-Weighted Imaging

While MT or FLAIR sequences are sensitive to detect an increase in the content of brain water, these techniques cannot discriminate whether this water is intracellular or extracellular. DWI allows calculating an apparent diffusion coef fi cient (ADC), which represents a tool to understand the interaction between water and the cellular

Fig. 10.4 ( a ) Baseline MR study (transverse fast-FLAIR T2-weighted imaging) of a 56-year-old patient with hepatitis C cirrhosis without overt hepatic encephalopathy. Multiple focal white mat-ter lesions in both cerebral hemispheres were attributed to small vessel disease. ( b ) A new scan obtained 2 years later during an episode of hepatic encephalopathy shows marked increase in size of these focal white matter lesions. ( c ) A new follow-up scan after complete resolution of neuro-logical symptoms shows decrease in size of the white matter lesions. This last scan was almost identical to the fi rst study


barriers in its movement. Several studies revealed a signi fi cant increase in brain water diffusivity, more pronounced with the severity of HE [ 48– 50 ] . A study per-formed in 13 cirrhotic patients showed that induced hyperammonemia causes osmotic changes (increase in glutamine and decrease in myo-inositol) and a signi fi cant increase in ADC demonstrating that ammonia can lead to changes in brain water distribution [ 51 ] . A prospective study among patients with overt HE showed that after the resolution of the episode, there is a decrease in the ADC in the parietal gray matter suggesting a fl ux between extracellular and intracellular com-partments [ 52 ] . Furthermore, in a study performed among 40 cirrhotic patients, ADC showed a good correlation with neuropsychological test and its ability to pre-dict the development of overt HE [ 53 ] . According to the basis of diffusivity [ 54 ] , increase in ADC indicates augmentation of water in the extracellular compartment and consequently, does not support the astrocytic swelling as the cause of diffuse low-grade brain edema in cirrhosis.

Brain Size

Neuroradiological studies have documented brain atrophy in patients with cirrhosis, which is aggravated in those with history of alcohol abuse [ 55 ] . Volumetric MR techniques [ 56 ] have been applied to cirrhotic patients after liver transplant to assess changes in brain size after the resolution of low-grade brain edema [ 57 ] . This tech-nique has shown that the normalized brain volume (according to a standard cranial size) was smaller in patients with prior HE after adjustment for age. This fi nding, together with the persistence of cognitive de fi cits in those patients with prior HE [ 57, 58 ] , supports the hypothesis of structural damage secondary to HE [ 59 ] . Voxel-based morphometry has also observed a decrease in brain density in patients with cirrhosis compared with healthy controls in several areas of the brain, which was more pronounced in those patients with alcohol etiology and was related to the severity of liver failure. The decrease in brain density was associated with neurop-sychological performances and persisted after liver transplant [ 60 ] .

Functional Studies

In addition to changes in the structure and metabolism of brain tissue, patients with HE experience disturbances in neuronal function. These disturbances are heteroge-neously distributed in the fi rst stages of HE and are more conspicuous in some regions. The reasons for the higher vulnerability of some regions, such as the basal ganglia, the hippocampus, the corticospinal tract or the anterior cingulate cortex, is not known, but probably relates to speci fi c neurochemical properties of these regions.


Magnetic Resonance

Functional magnetic resonance imaging (fMRI) measure the hemodynamic response (change in blood fl ow) associated to different brain areas during predetermined tasks. The selected tasks are related to speci fi c brain areas and allow examining the function of this region. This technique requires patient’s collaboration so that is suitable for patients with low-grade HE. Few studies have evaluated cirrhotic patients with fMRI. These methods are capable of demonstrating the functional impairment, such as disturbances in attention [ 61 ] or the need to recruit more brain areas to carry out simple tasks [ 62 ] . These disturbances are indicative of the cogni-tive disturbance, but are not speci fi c to HE.

Nuclear Imaging Techniques

These techniques consist of assessing with PET or single-photon emission computed tomography (SPECT); the signal generated by radioisotopes that are administered intravenously. The radioisotopes are linked to molecules, such as deoxyglucose, which provides functional and metabolic information of the brain. The most relevant limitations are the spatial resolution, and the lack of information about the anatomi-cal structures and the detected metabolic data.

PET provides quantitative data of isotope distribution (nCi/mL); the main iso-topes used to study brain function are 15 O, 13 N, 11 C, and 18 F. In contrast, SPECT provides only relative measurements of the radioactivity (counts/mL) and uses uncommon biological elements such as 99mTc. However, SPECT is more easily available and less expensive than PET. Most recent application is the bimodal imag-ing that combines the anatomical images of CT or MR with functional images.

PET has been applied to investigate cerebral ammonia metabolism ( 13 N-ammonia PET) in parallel with cerebral glucose utilization ( 18 F- fl uorodesoxyglucose PET) [ 63 ] . In this study, plasma ammonia levels correlated with ammonia metabolism of the brain and with MR-spectroscopy in white matter. MR spectroscopy showed also a correlation with cerebral glucose utilization. However, ammonia metabolism and glucose utilization were not associated. The study suggests that cerebral ammonia metabolism is important in the development of HE but is not the only factor.

Energy impairment has been proposed to play a role in the pathogenesis of HE. Oxygen consumption ( 15 O-oxygen PET) and cerebral blood fl ow ( 15 O-water PET) have been investigated in cirrhotic patients with and without HE, and compared to healthy controls [ 64 ] . HE induced a decrease in oxygen consumption and cerebral blood fl ow. The analysis of fl ow-metabolism coupling indicated that the decrease in blood fl ow was not the cause, but the consequence of reduced brain energy metabo-lism. It has been proposed that the inability to use the delivered oxygen of patients with HE relates to a speci fi c inhibition associated with oxidative metabolism in mitochondria [ 65 ] .


One of the possible clinical applications of PET/SPECT is the differential diagnosis with other neurological disorders, such as Alzheimer’s or Parkinson’s disease, for which there are speci fi c radioligands that are of clinical help [ 66 ] . Future studies should con fi rm its utility for dif fi cult to diagnose cases.

Conclusions

Neuroimaging has had a rapid development in the last years and the data obtained from the brain of patients with different stages of liver disease provided us with a better understanding of the pathogenesis of hepatic encephalopathy. These tech-niques have been useful in the comprehension of the role of manganese in neuro-logic complications of liver disease, the development of diffuse low-grade brain edema, and the possible permanent damage associated with this metabolic condi-tion. The wide information obtained with these tools support their use in monitoring hepatic encephalopathy and evaluating the effect of new therapeutic measures.

Financial Support CIBEREHD is supported by Instituto de Salud Carlos III, Madrid, Spain. Rita García-Martínez has been supported by grant CM07/00109.

References

1. Cordoba J, Minguez B. Hepatic encephalopathy. Semin Liver Dis. 2008;28(1):70–80. 2. McPhail MJ, Taylor-Robinson SD. The role of magnetic resonance imaging and spectroscopy

in hepatic encephalopathy. Metab Brain Dis. 2010;25(1):65–72. 3. Stallings WC, Metzger AL, Pattridge KA, Fee JA, Ludwig ML. Structure-function relation-

ships in iron and manganese superoxide dismutases. Free Radic Res Commun. 1991;12–13(Pt 1):259–68.

4. Bentle LA, Lardy HA. Interaction of anions and divalent metal ions with phosphoenolpyruvate carboxykinase. J Biol Chem. 1976;251(10):2916–21.

5. Couper J. On the effects of black oxide of manganese when inhaled into the lungs. Br Ann Med Pharmacol. 1837;1:41–2.

6. Mena I, Marin O, Fuenzalida S, Cotzias GC. Chronic manganese poisoning. Clinical picture and manganese turnover. Neurology. 1967;17(2):128–36.

7. Keiding S, Sorensen M, Bender D, Munk OL, Ott P, Vilstrup H. Brain metabolism of 13N-ammonia during acute hepatic encephalopathy in cirrhosis measured by positron emission tomography. Hepatology. 2006;43(1):42–50.

8. Haussinger D. Low grade cerebral edema and the pathogenesis of hepatic encephalopathy in cirrhosis. Hepatology. 2006;43(6):1187–90.

9. Cordoba J, Blei AT. Brain edema and hepatic encephalopathy. Semin Liver Dis. 1996;16(3):271–80.

10. Donovan JP, Schafer DF, Shaw Jr BW, Sorrell MF. Cerebral oedema and increased intracranial pressure in chronic liver disease. Lancet. 1998;351(9104):719–21.

11. Chen F, Ohashi N, Li W, Eckman C, Nguyen JH. Disruptions of occludin and claudin-5 in brain endothelial cells in vitro and in brains of mice with acute liver failure. Hepatology. 2009;50(6):1914–23.


12. Victor M, Adams RD, Cole M. The acquired (non-Wilsonian) type of chronic hepatocerebral degeneration. Medicine (Baltimore). 1965;44(5):345–96.

13. Atluri DK, Asgeri M, Mullen KD. Reversibility of hepatic encephalopathy after liver transplantation. Metab Brain Dis. 2010;25(1):111–3.

14. Pujol A, Pujol J, Graus F, Rimola A, Peri J, Mercader JM, et al. Hyperintense globus pallidus on T1-weighted MRI in cirrhotic patients is associated with severity of liver failure. Neurology. 1993;43(1):65–9.

15. Matsumoto S, Mori H, Yoshioka K, Kiyosue H, Komatsu E. Effects of portal-systemic shunt embolization on the basal ganglia: MRI. Neuroradiology. 1997;39(5):326–8.

16. Krieger S, Jauss M, Jansen O, Stiehl A, Sauer P, Geissler M, et al. MRI fi ndings in chronic hepatic encephalopathy depend on portosystemic shunt: results of a controlled prospective clinical investigation. J Hepatol. 1997;27(1):121–6.

17. Butterworth RF, Spahr L, Fontaine S, Layrargues GP. Manganese toxicity, dopaminergic dys-function and hepatic encephalopathy. Metab Brain Dis. 1995;10(4):259–67.

18. Spahr L, Butterworth RF, Fontaine S, Bui L, Therrien G, Milette PC, et al. Increased blood manganese in cirrhotic patients: relationship to pallidal magnetic resonance signal hyperinten-sity and neurological symptoms. Hepatology. 1996;24(5):1116–20.

19. Pomier-Layrargues G, Spahr L, Butterworth RF. Increased manganese concentrations in pal-lidum of cirrhotic patients. Lancet. 1995;345(8951):735.

20. Krieger D, Krieger S, Jansen O, Gass P, Theilmann L, Lichtnecker H. Manganese and chronic hepatic encephalopathy. Lancet. 1995;346(8970):270–4.

21. Ejima A, Imamura T, Nakamura S, Saito H, Matsumoto K, Momono S. Manganese intoxica-tion during total parenteral nutrition. Lancet. 1992;339(8790):426.

22. Nolte W, Wiltfang J, Schindler CG, Unterberg K, Finkenstaedt M, Niedmann PD, et al. Bright basal ganglia in T1-weighted magnetic resonance images are frequent in patients with portal vein thrombosis without liver cirrhosis and not suggestive of hepatic encephalopathy. J Hepatol. 1998;29(3):443–9.

23. Minguez B, Garcia-Pagan JC, Bosch J, Turnes J, Alonso J, Rovira A, et al. Noncirrhotic portal vein thrombosis exhibits neuropsychological and MR changes consistent with minimal hepatic encephalopathy. Hepatology. 2006;43(4):707–14.

24. Lockwood AH, Weissenborn K, Butterworth RF. An image of the brain in patients with liver disease. Curr Opin Neurol. 1997;10(6):525–33.

25. Weissenborn K, Ehrenheim C, Hori A, Kubicka S, Manns MP. Pallidal lesions in patients with liver cirrhosis: clinical and MRI evaluation. Metab Brain Dis. 1995;10(3):219–31.

26. Cordoba J, Olive G, Alonso J, Rovira A, Segarra A, Perez M, et al. Improvement of magnetic reso-nance spectroscopic abnormalities but not pallidal hyperintensity followed amelioration of hepatic encephalopathy after occlusion of a large spleno-renal shunt. J Hepatol. 2001;34(1):176–8.

27. Cordoba J, Alonso J, Rovira A, Jacas C, Sanpedro F, Castells L, et al. The development of low-grade cerebral edema in cirrhosis is supported by the evolution of (1)H-magnetic reso-nance abnormalities after liver transplantation. J Hepatol. 2001;35(5):598–604.

28. Naegele T, Grodd W, Viebahn R, Seeger U, Klose U, Seitz D, et al. MR imaging and (1)H spectroscopy of brain metabolites in hepatic encephalopathy: time-course of renormalization after liver transplantation. Radiology. 2000;216(3):683–91.

29. Lockwood AH, Yap EW, Wong WH. Cerebral ammonia metabolism in patients with severe liver disease and minimal hepatic encephalopathy. J Cereb Blood Flow Metab. 1991;11(2):337–41.

30. Cordoba J. New assessment of hepatic encephalopathy. J Hepatol. 2011;54(5):1030–40. 31. Geissler A, Lock G, Frund R, Held P, Hollerbach S, Andus T, et al. Cerebral abnormalities in

patients with cirrhosis detected by proton magnetic resonance spectroscopy and magnetic resonance imaging. Hepatology. 1997;25(1):48–54.

32. Kreis R, Ross BD, Farrow NA, Ackerman Z. Metabolic disorders of the brain in chronic hepatic encephalopathy detected with H-1 MR spectroscopy. Radiology. 1992;182(1):19–27.

33. Cordoba J. Glutamine, myo-inositol, and brain edema in acute liver failure. Hepatology. 1996;23(5):1291–2.


34. Thomas MA, Huda A, Guze B, Curran J, Bugbee M, Fairbanks L, et al. Cerebral 1H MR spectroscopy and neuropsychologic status of patients with hepatic encephalopathy. AJR Am J Roentgenol. 1998;171(4):1123–30.

35. Cordoba J, Raguer N, Flavia M, Vargas V, Jacas C, Alonso J, et al. T2 hyperintensity along the cortico-spinal tract in cirrhosis relates to functional abnormalities. Hepatology. 2003;38(4):1026–33.

36. Singhal A, Nagarajan R, Hinkin CH, Kumar R, Sayre J, Elderkin-Thompson V, et al. Two-dimensional MR spectroscopy of minimal hepatic encephalopathy and neuropsychological correlates in vivo. J Magn Reson Imaging. 2010;32(1):35–43.

37. Guevara M, Baccaro ME, Torre A, Gomez-Anson B, Rios J, Torres F, et al. Hyponatremia is a risk factor of hepatic encephalopathy in patients with cirrhosis: a prospective study with time-dependent analysis. Am J Gastroenterol. 2009;104(6):1382–9.

38. Garcia MR, Rovira A, Alonso J, Aymerich FX, Huerga E, Jacas C, et al. A long-term study of changes in the volume of brain ventricles and white matter lesions after successful liver transplantation. Transplantation. 2010;89(5):589–94.

39. Shah NJ, Neeb H, Kircheis G, Engels P, Haussinger D, Zilles K. Quantitative cerebral water content mapping in hepatic encephalopathy. Neuroimage. 2008;41(3):706–17.

40. Wolff SD, Balaban RS. Magnetization transfer imaging: practical aspects and clinical appli-cations. Radiology. 1994;192(3):593–9.

41. Iwasa M, Kinosada Y, Nakatsuka A, Watanabe S, Adachi Y. Magnetization transfer contrast of various regions of the brain in liver cirrhosis. AJNR Am J Neuroradiol. 1999;20(4):652–4.

42. Rovira A, Grive E, Pedraza S, Rovira A, Alonso J. Magnetization transfer ratio values and proton MR spectroscopy of normal-appearing cerebral white matter in patients with liver cirrhosis. AJNR Am J Neuroradiol. 2001;22(6):1137–42.

43. Rovira A, Cordoba J, Sanpedro F, Grive E, Rovira-Gols A, Alonso J. Normalization of T2 signal abnormalities in hemispheric white matter with liver transplant. Neurology. 2002;59(3):335–41.

44. Rovira A, Minguez B, Aymerich FX, Jacas C, Huerga E, Cordoba J, et al. Decreased white matter lesion volume and improved cognitive function after liver transplantation. Hepatology. 2007;46(5):1485–90.

45. Minguez B, Rovira A, Alonso J, Cordoba J. Decrease in the volume of white matter lesions with improvement of hepatic encephalopathy. AJNR Am J Neuroradiol. 2007;28(8):1499–500.

46. McKinney AM, Lohman BD, Sarikaya B, Uhlmann E, Spanbauer J, Singewald T, et al. Acute hepatic encephalopathy: diffusion-weighted and fl uid-attenuated inversion recovery fi ndings, and correlation with plasma ammonia level and clinical outcome. AJNR Am J Neuroradiol. 2010;31(8):1471–9.

47. de Groot JC, de Leeuw FE, Oudkerk M, Van Gijn J, Hofman A, Jolles J, et al. Cerebral white matter lesions and cognitive function: the Rotterdam Scan Study. Ann Neurol. 2000;47(2):145–51.

48. Lodi R, Tonon C, Stracciari A, Weiger M, Camaggi V, Iotti S, et al. Diffusion MRI shows increased water apparent diffusion coef fi cient in the brains of cirrhotics. Neurology. 2004;62(5):762–6.

49. Kale RA, Gupta RK, Saraswat VA, Hasan KM, Trivedi R, Mishra AM, et al. Demonstration of interstitial cerebral edema with diffusion tensor MR imaging in type C hepatic encephalopa-thy. Hepatology. 2006;43(4):698–706.

50. Miese F, Kircheis G, Wittsack HJ, Wenserski F, Hemker J, Modder U, et al. 1H-MR spectros-copy, magnetization transfer, and diffusion-weighted imaging in alcoholic and nonalcoholic patients with cirrhosis with hepatic encephalopathy. AJNR Am J Neuroradiol. 2006;27(5):1019–26.

51. Mardini H, Smith FE, Record CO, Blamire AM. Magnetic resonance quanti fi cation of water and metabolites in the brain of cirrhotics following induced hyperammonaemia. J Hepatol. 2011;54:1154–60.


52. Poveda MJ, Bernabeu A, Concepcion L, Roa E, de Madaria E, Zapater P, et al. Brain edema dynamics in patients with overt hepatic encephalopathy A magnetic resonance imaging study. Neuroimage. 2010;52(2):481–7.

53. Sugimoto R, Iwasa M, Maeda M, Urawa N, Tanaka H, Fujita N, et al. Value of the apparent diffusion coef fi cient for quanti fi cation of low-grade hepatic encephalopathy. Am J Gastroenterol. 2008;103(6):1413–20.

54. Schaefer PW, Grant PE, Gonzalez RG. Diffusion-weighted MR imaging of the brain. Radiology. 2000;217(2):331–45.

55. Zeneroli ML, Cioni G, Vezzelli C, Grandi S, Crisi G, Luzietti R, et al. Prevalence of brain atrophy in liver cirrhosis patients with chronic persistent encephalopathy. Evaluation by com-puted tomography. J Hepatol. 1987;4(3):283–92.

56. Smith SM, Zhang Y, Jenkinson M, Chen J, Matthews PM, Federico A, et al. Accurate, robust, and automated longitudinal and cross-sectional brain change analysis. Neuroimage. 2002;17(1):479–89.

57. Garcia-Martinez R, Rovira A, Alonso J, Jacas C, Simon-Talero M, Chavarria L, et al. Hepatic encephalopathy is associated with posttransplant cognitive function and brain volume. Liver Transpl. 2011;17(1):38–46.

58. Sotil EU, Gottstein J, Ayala E, Randolph C, Blei AT. Impact of preoperative overt hepatic encephalopathy on neurocognitive function after liver transplantation. Liver Transpl. 2009;15(2):184–92.

59. Rose C, Jalan R. Is minimal hepatic encephalopathy completely reversible following liver transplantation? Liver Transpl. 2004;10(1):84–7.

60. Guevara M, Baccaro ME, Gomez-Anson B, Frisoni G, Testa C, Torre A, et al. Cerebral magnetic resonance imaging reveals marked abnormalities of brain tissue density in patients with cirrhosis without overt hepatic encephalopathy. J Hepatol. 2011;55(3):564–73.

61. Za fi ris O, Kircheis G, Rood HA, Boers F, Haussinger D, Zilles K. Neural mechanism underlying impaired visual judgement in the dysmetabolic brain: an fMRI study. Neuroimage. 2004;22(2):541–52.

62. Zhang LJ, Yang G, Yin J, Liu Y, Qi J. Neural mechanism of cognitive control impairment in patients with hepatic cirrhosis: a functional magnetic resonance imaging study. Acta Radiol. 2007;48(5):577–87.

63. Weissenborn K, Ahl B, Fischer-Wasels D, van den HJ, Hecker H, Burchert W, et al. Correlations between magnetic resonance spectroscopy alterations and cerebral ammonia and glucose metabolism in cirrhotic patients with and without hepatic encephalopathy. Gut. 2007;56(12):1736–42.

64. Iversen P, Sorensen M, Bak LK, Waagepetersen HS, Vafaee MS, Borghammer P, et al. Low cerebral oxygen consumption and blood fl ow in patients with cirrhosis and an acute episode of hepatic encephalopathy. Gastroenterology. 2009;136(3):863–71.

65. Keiding S, Sorensen M, Munk OL, Bender D. Human (13)N-ammonia PET studies: the impor-tance of measuring (13)N-ammonia metabolites in blood. Metab Brain Dis. 2010;25(1):49–56.

66. Narendran R, Mason NS, Laymon CM, Lopresti BJ, Velasquez ND, May MA, et al. A comparative evaluation of the dopamine D(2/3) agonist radiotracer [11C](-)-N-propyl-norapomorphine and antagonist [11C]raclopride to measure amphetamine-induced dopamine release in the human striatum. J Pharmacol Exp Ther. 2010;333(2):533–9.

Part III Treatment


Keywords Hepatic encephalopathy • Disaccharides • Lactulose

Hepatic encephalopathy (HE) is a complex neuropsychiatric syndrome, which may complicate acute or chronic liver failure. It is characterized by changes in mental state including a wide range of neuropsychiatric symptoms ranging from minor signs of altered brain function to deep coma. Traditionally, HE is graded according to the West Haven criteria, which de fi ne HE grades I–IV based on the presence of speci fi c clinical signs and symptoms and their severity [ 1, 2 ] . However, patients with cirrhosis present with a continuous severity spectrum of neuropsychological symptoms ranging from entire normality (HE 0) up to obvious de fi cits [ 3 ] . Even in minimal HE (MHE) without obvious clinical symptoms, neuropsychological and neurophysiological testing uncovers de fi cits which impact on the quality of life and the fi tness to drive a motor vehicle [ 4– 7 ] .

There is consensus that ammonia is a key toxin in HE, which may sensitize the brain to the different precipitating factors (Fig. 11.1 ) [ 8, 9 ] . Astrocytes play an important role in the pathogenesis of HE with consequences on neuronal function. At the neurophysiological level, the motor de fi cits seen in patients with HE are characterized by a pathologically altered oscillatory coupling within the central motor system and the cognitive de fi cits are assigned to pathologically alter oscilla-tory activity in higher cognitive brain areas [ 10, 11 ] . In chronic liver disease, urea synthesis is impaired and the brain acts as an alternative major ammonia detoxi fi cation pathway. Astrocytes have the ability to eliminate ammonia by the synthesis of

P. Sharma, MD, DM • S. K. Sarin, MD, DM, FNA, FNASc (*) Department of Hepatology , Institute of Liver and Biliary Sciences , New Delhi 110070, India e-mail: [email protected]

Chapter 11 Disaccharides in the Treatment of Hepatic Encephalopathy

Praveen Sharma and Shiv Kumar Sarin

142 P. Sharma and S.K. Sarin

glutamine through amidation of glutamate by the enzyme glutamine synthetase [ 12– 14 ] . Hyperammonemia leads to the accumulation of glutamine within astro-cytes, which exerts an osmotic stress that causes astrocytes to take in water and swell. Further support for the ammonia–glutamine–brain water hypothesis has been provided by inducing hyperammonemia in patients with cirrhosis through the oral administration of an amino acid solution. An increase in brain glutamine, reduction in magnetization transfer ratio, and signi fi cant deterioration in neuropsychological function were suggestive of an increase in brain water [ 15 ] .

Nonabsorbable Disaccharides and Mechanism of Action

For over 25 years, nonabsorbable disaccharides have been the fi rst-line drug treat-ment for lowering the production and absorption of ammonia in HE. Current therapies for HE are based on ammonia lowering, with the hypothesis that the colon is the

Fig. 11.1 Pathogenesis of brain swelling—ammonia

14311 Disaccharides in the Treatment of Hepatic Encephalopathy

primary organ that generates ammonia (Fig. 11.2 ) [ 2, 16 ] . Lactulose is the most commonly utilized nonabsorbable disaccharide for HE. Lactulose, a synthetic disac-charide, is comprised of the monosaccharides lactose and galactose, and is available as a syrup. Doses are generally titrated to achieve two to four semisoft stools daily, with typical doses of 20 g/30 mL orally 3–4 times per day. A second nonabsorbable disaccharide, lactitol, has also been used in the treatment of HE, but it is not currently commercially available in the United States [ 17, 18 ] . Lactitol ( p -galactosido-sorbitol) is a disaccharide analog of lactulose which is neither absorbed nor broken down in the small intestine, but is extensively metabolized by colonic bacteria. It is produced in a highly soluble crystalline powder form which is reported to be less sweet in taste than lactulose. Clinical trials have reported lactitol dosages of 10 g every 6 h, 0.5 g/kg/day twice daily and lactitol powder 66.7 g/100 mL titrated to two bowel movements daily (mean equivalent of approximately lactitol 30 g/day) [ 17, 19 ] . Both lactulose and lactitol get metabolized by the bacteria in the colon to acetic and lactic acid. This acidi fi cation of the colon not only creates a hostile environment for the survival of intestinal bacteria with urease activity involved in the production of ammonia in the gut, but also facilitates the conversion of NH

3 to nonabsorbable

NH 4 + . Both effects result in reduced levels of ammonia in the colon and portal blood.

Nonabsorbable disaccharides also cause a fourfold increase in fecal nitrogen excre-tion due to their cathartic effect [ 20– 22 ] .

Fig. 11.2 Therapies for hepatic encephalopathy based on site of action


Clinical Ef fi cacy of Nonabsorbable Disaccharides

Lactulose or Lactitol Versus Placebo or No Intervention

Overt Hepatic Encephalopathy

The nonabsorbable disaccharides have been a mainstay of therapy for HE for decades, and have been extensively studied in several small clinical trials since the late 1960s for this indication. In most of these trials, patients had cirrhosis with acute, chronic or minimal hepatic encephalopathy [ 23– 30 ] . Oral lactulose was used in majority of these studies though some had also used lactitol and lactulose enemas [ 26 ] . Uribe et al. [ 26 ] performed a double-blind, controlled trial to study the ef fi cacy of acidifying enemas of lactitol and lactose vs. nonacidifying tap-water enemas in 45 episodes of acute portosystemic encephalopathy. A favorable response to treatment was obtained in 19 (86%) of the patients receiving lactitol enemas and in 14 (78%) of those receiving lactose enemas. They concluded that acidifying agents like lac-tose and lactitol are effective and superior to tap-water enemas for the treatment of acute nitrogenous portosystemic encephalopathy. In most of the studies, the daily mean doses of lactulose ranged from 30 to 80 g (median 50 g) to obtain two to three semisoft stools per day. The median duration of treatment was 15 days (range 5–360 days). None of the trials followed up patients after the end of treatment. A recent meta-analysis evaluated 22 clinical trials in order to better assess the utilization of nonabsorbable disaccharides in the management of HE when compared with pla-cebo, no intervention, or antimicrobials. Compared with placebo or no intervention, lactulose and lactitol seemed to reduce the risk of no improvement of hepatic encephalopathy (relative risk 0.62, 95% con fi dence interval 0.46–0.84). However, high quality trials found no signi fi cant effect of lactulose or lactitol on the risk of no improvement (0.92, 0.42–2.04), whereas low quality trials found a signi fi cant bene fi cial effect of lactulose or lactitol (0.57, 0.40–0.83) [ 31, 32 ] . At the present time, however, there is a lack of suf fi cient evidence to thoroughly refute the use of nonabsorbable disaccharides for the treatment of HE.

Minimal Hepatic Encephalopathy

Trials in patients with minimal hepatic encephalopathy (MHE) found that lactulose or lactitol signi fi cantly reduced the risk of no improvement assessed by various psycho-metric tests (0.61, 0.47–0.79). Compared with placebo or no intervention, lactulose and lactitol had no signi fi cant effect on mortality but tended to lower blood ammonia. Reported adverse events were not serious, and all originated from the gastrointestinal tract (diarrhea, fl atulence, abdominal pain, or nausea) [ 31 ] . A summary analysis of some clinical trials of nonabsorbable disaccharides vs. placebo/no treatment is shown in Table 11.1 . In a recent study, Prasad et al. [ 30 ] found that treatment with lactulose improved both cognitive function and health-related quality of life, as measured by the Sickness Impact Pro fi le, when compared against a “no treatment” patient group.


Tabl

e 11

.1

Com

pari

son

of n

onab

sorb

able

dis

acch

arid

es a

nd p

lace

bo o

r no

trea

tmen

t for

hep

atic

enc

epha

lopa

thy

Tri

al

Stud

y de

sign

Pa

tient

s N

o.

Tre

atm

ent

Ass

essm

ent

Ef fi

cacy

Sim

mon

s et

al.

[ 23 ]

Pa

ralle

l A

HE

+ C

HE

26

L

actu

lose

/glu

cose

C

linic

al g

radi

ng,

amm

onia

, sto

ol

prod

uctio

n

Lac

tulo

se =

glu

cose

Rod

gers

et a

l. [ 2

4 ]

Cro

ssov

er

CH

E

6 L

actu

lose

/sor

bito

l C

linic

al g

radi

ng,

EE

G, a

mm

onia

L

actu

lose

= so

rbito

l

Cor

azza

et a

l. [ 2

5 ]

Para

llel

CH

E

32

Lac

tulo

se/p

lace

bo

Enc

epha

lopa

thy

inte

nsity

sco

re,

amm

onia

Lac

tulo

se b

ette

r th

an

plac

ebo

Uri

be e

t al.

[ 26 ]

Pa

ralle

l A

HE

15

L

actu

lose

ene

ma

Mor

talit

y, c

linic

al

grad

ing

Lac

tulo

se >

pla

cebo

Hor

sman

s et

al.

[ 27 ]

Pa

ralle

l M

HE

14

L

actu

lose

/pla

cebo

Ps

ycho

met

ric

test

s,

amm

onia

leve

ls

Lac

tulo

se >

pla

cebo

Wat

anab

e et

al.

[ 28 ]

Pa

ralle

l M

HE

36

L

actu

lose

/no

trea

tmen

t T

hree

psy

chom

etri

c te

sts,

am

mon

ia

Lac

tulo

se >

pla

cebo

Dhi

man

et a

l. [ 2

9 ]

Para

llel

MH

E

26

Lac

tulo

se/n

o tr

eatm

ent

Psyc

hom

etri

c te

sts

Lac

tulo

se >

pla

cebo

Pr

asad

et a

l. [ 3

0 ]

Para

llel

MH

E

61

Lac

tulo

se/n

o tr

eatm

ent

Psyc

hom

etri

c te

sts

and

HR

QO

L

Lac

tulo

se >

pla

cebo

AH

E a

cute

hep

atic

enc

epha

lopa

thy;

CH

E c

hron

ic h

epat

ic e

ncep

halo

path

y; M

HE

min

imal

hep

atic

enc

epha

lopa

thy;

EE

G e

lect

roen

ceph

alog

raph

y


Lactulose Versus Lactitol for the Treatment of Hepatic Encephalopathy

Lactulose and lactitol both have been used for the treatment of HE and lactulose has been compared with lactitol in various studies (Table 11.2 ) [ 18, 19, 33– 40 ] . In a meta-analysis by Blanc et al. [ 39 ] , evaluated parameters were portosystemic enceph-alopathy index of Conn after treatment, the percentage of improved patients, and the percentage of patients who had ill effects related to the treatment ( fl atulence, diar-rhea). The duration of the treatment ranged from 3 to 6 months. All studies found a similar ef fi ciency with both drugs. However, they exhibited some discrepancies in the relative frequency of adverse reactions ( fl atulence). Meta-analysis showed no statistical differences in the portosystemic encephalopathy index after lactitol or lactulose treatment. The percentage of improved patients after lactitol or lactulose was similar [ 39 ] . In contrast, the analysis revealed a higher frequency ( p less than 0.01) of fl atulence in patients treated with lactulose compared with those treated with lactitol. In conclusion, this meta-analysis shows no statistical difference between therapeutic effects of lactitol and lactulose, but it does show a higher fre-quency of fl atulence with lactulose [ 39 ] . However, an another meta-analysis by Cammà et al. [ 40 ] showed that lactitol was as effective as other disaccharides in the treatment of encephalopathy: pooled odds ratio was 0.83, 95% con fi dence interval was 0.38–1.82. Patients experienced fewer side effects during treatment with lacti-tol, but the pooled odds ratio was not statistically signi fi cant. In all studies, lactitol was considered more palatable [ 33, 38 ] . Clinical effectiveness of lactitol, in long-term treatment of chronic encephalopathy, is similar to those of lactulose. It seems that lactitol has lower side effects than lactulose.

Comparison of Lactulose and Antimicrobial Agents for Hepatic Encephalopathy

Antimicrobial agents have long been utilized as an alternative treatment option for patients intolerant or unresponsive to nonabsorbable disaccharides. Neomycin and other antimicrobials are utilized as a treatment modality in HE due to their ability to inhibit ammonia production by intestinal bacteria [ 41 ] . Other antimicrobials, including metronidazole and vancomycin, have been studied to a more limited extent than neomycin (Table 11.3 ) [ 42– 44 ] . Orlandi et al. [ 43 ] conducted a random-ized study in order to compare the course of HE in patients treated with neomycin plus magnesium sulfate or with lactulose. The treatment groups were similar in terms of clinical characteristics, fatalities, recovery rate from grade 1 encephalopa-thy, and disappearance rate of neuropsychiatric signs. Transitions from severe to grade 1 or 0 encephalopathy showed a 0.17 (NS) difference in favor of neomycin. Early therapy and evidence of precipitating factors showed a favorable prognostic signi fi cance.


Tabl

e 11

.2

Com

pari

son

of la

ctul

ose

and

lact

itol f

or h

epat

ic e

ncep

halo

path

y

Tri

al

Stud

y de

sign

Pa

tient

s N

o.

Tre

atm

ent

dura

tion

Ass

essm

ent

Ef fi

cacy

Lan

thie

r et

al.

[ 33 ]

C

ross

over

C

HE

5

6

mon

ths

Clin

ical

exa

min

atio

n,

psyc

hom

etri

c te

sts,

am

mon

ia le

vels

, EE

G,

cere

bral

blo

od fl

ow

Lac

tulo

se =

lact

itol

Mor

gan

and

Haw

ley

[ 18 ]

Pa

ralle

l, do

uble

bl

ind

AH

E

25

5 da

ys

Psyc

hom

etri

c te

sts,

EE

G,

PSE

inde

x L

actu

lose

= la

ctito

l

Her

edia

et a

l. [ 1

9 ]

Para

llel

AH

E

40

5 da

ys

Mor

talit

y, c

linic

al g

radi

ng,

PSE

gra

de, a

dver

se e

vent

s L

actu

lose

= la

ctito

l

Her

edia

et a

l. [ 3

4 ]

Ran

dom

ized

, cr

osso

ver

CH

E

25

6 m

onth

s Ps

ycho

met

ric

test

s, a

mm

onia

le

vels

, EE

G, P

SE in

dex

Lac

tulo

se =

lact

itol

Mor

gan

et a

l. [ 3

5 ]

Dou

ble-

blin

d,

rand

om-

ized

, cr

osso

ver

MH

E

9

3 m

onth

s Ps

ycho

met

ric

test

s, a

mm

onia

le

vels

, EE

G

Lac

tulo

se =

lact

itol

Rig

gio

et a

l. [ 3

6 ]

Para

llel

CH

E +

MH

E

31

6 m

onth

s PS

E in

dex,

new

epi

sode

s of

HE

, adv

erse

eve

nts

Lac

tulo

se =

lact

itol

Gra

ndi e

t al.

[ 37 ]

C

ross

-ove

r C

HE

40

–

PSE

inde

x, a

dver

se e

vent

s L

actu

lose

= la

ctito

l Pa

i et a

l. [ 3

8 ]

Para

llel

AH

E

45

5 da

ys

PSE

inde

x, a

dver

se e

vent

s L

actit

ol >

lact

ulos

e B

lanc

et a

l. [ 3

9 ]

Met

a-an

alys

is

CH

E

77

3–6

mon

ths

PSE

inde

x L

actu

lose

= la

ctito

l C

amm

à et

al.

[ 40 ]

M

eta-

anal

ysis

C

HE

–

– PS

E in

dex

Lac

tulo

se =

lact

itol

AH

E a

cute

hep

atic

enc

epha

lopa

thy;

CH

E c

hron

ic h

epat

ic e

ncep

halo

path

y; M

HE

min

imal

hep

atic

enc

epha

lopa

thy;

PSE

por

tosy

stem

ic e

ncep

halo

path

y


Table 11.3 Comparison of lactulose and neomycin, metronidazole for hepatic encephalopathy

Trial Study design No. of patients

Duration of treatment Assessment Ef fi cacy

Conn et al. [ 41 ]

Neomycin vs. lactulose (double-blind, randomized, crossover)

29 10 days each arm before crossover

Mental status, asterixis score, EEG, ammonia levels, PSE index

Neomycin = lactulose

Atterbury et al. [ 42 ]

Parallel 47 7 days Mental status, asterixis score, EEG, ammonia levels, PSE index


Orlandi et al. [ 43 ]

Single blind 173 14 days Mental status, asterixis score, EEG, ammonia levels, HE change


EEG electroencephalography

Comparison of Lactulose and Rifaximin for Hepatic Encephalopathy

Rifaximin is a poorly absorbed synthetic antimicrobial with a broad spectrum of antibacterial activity, including both aerobic and anaerobic Gram-positive and Gram-negative organisms. Due to its low rate of systemic absorption, rifaximin appears to be relatively safe [ 45 ] . Many studies have demonstrated the ef fi cacy of rifaximin in the treatment of overt HE (grade ³ 1) (Table 11.4 ) [ 46– 56 ] . In addition, a randomized, double-blind, dose-ranging study demonstrated that rifaximin at doses of 1,200 and 2,400 mg/day for 7 days signi fi cantly improved HE [ 46 ] . In a meta-analysis by Als-Nielsen et al. [ 31, 32 ] compared with antibiotics, patients tak-ing lactulose or lactitol had a signi fi cantly higher risk of no improvement of hepatic encephalopathy (1.24, 1.02–1.50). They also found no signi fi cant difference in response to treatment between aminoglycosides and rifaximin ( p = 0.2 by test of interaction) or when trials were strati fi ed by quality or type of hepatic encephalopa-thy. It was also found that there was no signi fi cantly different effect on mortality between nonabsorbable disaccharides and antibiotics (0.90, 0.48–1.67) or on adverse events (1.62, 0.57–4.58). None of the reported adverse events were serious, and all originated from the gastrointestinal tract (diarrhea, fl atulence, abdominal pain, or nausea). In a meta-analysis by Jiang et al. [ 57 ] , fi ve trials involving 264 patients met all the inclusion criteria. There was no signi fi cant difference between rifaximin and nonabsorbable disaccharides on improvement in patients with hepatic encephalopathy (relative risk [RR] 1.08; 95% con fi dence interval [CI], 0.85–1.38; p = 0.53). RR was 0.98 (95% CI: 0.85–1.13; p = 0.74) for acute hepatic encephalopathy


Tabl

e 11

.4

Com

pari

son

of la

ctul

ose

and

rifa

xim

in f

or h

epat

ic e

ncep

halo

path

y

Tri

al

Stud

y de

sign

N

o. o

f pa

tient

s D

urat

ion

of tr

eatm

ent

Ass

essm

ent

Ef fi

cacy

Fest

i et a

l. [ 4

6 ]

Lac

tulo

se (

open

-lab

el)

21

21

Neu

rolo

gica

l sig

ns o

f H

E,

aste

rixi

s sc

ore,

HR

NB

, E

EG

, am

mon

ia le

vels

Rif

axim

in =

lact

ulos

e

Buc

ci a

nd P

alm

ieri

[ 50

] L

actu

lose

(do

uble

-blin

d,

doub

le-d

umm

y)

58

15

Neu

rolo

gica

l sta

tus,

ast

erix

is

scor

e, H

RN

B, c

ance

latio

n ta

sks,

EE

G, a

mm

onia

leve

ls

Rif

axim

in >

lact

ulos

e

Mas

sa e

t al.

[ 52 ]

L

actu

lose

(do

uble

-blin

d,

doub

le-d

umm

y)

40

15

HE

inde

x se

veri

ty, m

enta

l st

atus

, can

cela

tion

task

s,

HR

NB

, EE

G

Rif

axim

in >

lact

ulos

e

Fera

et a

l. [ 5

4 ]

Lac

tulo

se (

doub

le-b

lind,

do

uble

-dum

my)

4

0 Fi

rst 2

wee

ks o

f ea

ch

mon

th f

or 3

mon

ths

Men

tal s

tatu

s, a

ster

ixis

sco

re,

canc

elat

ion

task

s, H

RN

B,

EE

G, a

mm

onia

leve

ls, P

SE

inde

x

Rif

axim

in >

lact

ulos

e

Mas

et a

l. [ 5

3 ]

Lac

titol

(do

uble

-blin

d,

doub

le-d

umm

y)

103

5–10

day

s M

enta

l sta

tus,

ast

erix

is s

core

, E

EG

, am

mon

ia le

vels

, PSE

in

dex,

psy

chom

etri

c te

sts

Rif

axim

in =

lact

itol

Lee

vy e

t al.

[ 55 ]

L

actu

lose

(cr

osso

ver)

14

5 >

6 m

onth

s la

ctul

ose

>6

mon

ths

rifa

xim

in

HE

gra

de, a

ster

ixis

sco

re

Rif

axim

in >

lact

ulos

e

Paik

et a

l. [ 5

6 ]

Lac

tulo

se (

open

-lab

el)

54

7 da

ys

Am

mon

ia le

vels

, fl ap

ping

tr

emor

, men

tal s

tatu

s, H

E

inde

x, p

sych

omet

ric

test

s

Rif

axim

in =

lact

itol

Jian

g et

al.

[ 57 ]

M

eta-

anal

ysis

26

4 –

– R

ifax

imin

= la

ctito

l


in 157 patients and 0.87 (95% CI: 0.40–1.88; p = 0.72) for chronic hepatic enceph-alopathy in 96 patients, respectively. There was no signi fi cant difference between rifaximin and nonabsorbable disaccharides on diarrhea (RR = 0.90; 95% CI: 0.17–4.70; p = 0.90). However, a signi fi cant difference in favor of rifaximin on abdominal pain (RR = 0.28; 95% CI: 0.08–0.95; p = 0.04) was identi fi ed. Rifaximin is not supe-rior to nonabsorbable disaccharides for acute or chronic hepatic encephalopathy in the long-term or short-term treatment except that it may be better tolerated. Further studies on larger populations are required to provide more suf fi cient evidence for assessment of the use of rifaximin.

Disaccharides Versus Other Therapy for Hepatic Encephalopathy

Loguercio et al. [ 58 ] studied 40 patients with cirrhosis on a dietary protein regimen of 1 g/kg b.w., determined the effect on chronic hepatic encephalopathy of long-term administration of Enterococcus faecium (SF68) vs. lactulose. The patients received one of the two treatments for three periods of 4 weeks, each separated by drug-free 2-week intervals. The ef fi cacy of treatment was assessed by arterial blood ammonia concentration, mental status, number connection (Reitan’s part A) test, and fl ash-evoked visual potentials. At the end of the third period, the reduction in both blood ammonia concentrations and Reitan’s test times was more enhanced in patients on SF68 than in patients on lactulose. In conclusion, SF68 is at least as use-ful as lactulose for the chronic treatment of chronic hepatic encephalopathy; it has no adverse effects, and treatment can be interrupted for 2 weeks without losing the bene fi cial effects. Sushma et al. [ 59 ] conducted a prospective randomized double-blind study to evaluate the ef fi cacy of sodium benzoate in the treatment of acute portosystemic encephalopathy. Seventy-four consecutive patients with cirrhosis or surgical portosystemic anastomosis and hepatic encephalopathy of less than 7 days duration were randomized to receive lactulose (dose adjusted for 2 or 3 semiformed stools/day) or sodium benzoate (5 g twice daily). Assessment of response included mental status, asterixis, arterial ammonia level, electroencephalogram and number-connection test. The incidence of side effects was similar in the two treatment groups. The cost of lactulose for one course of therapy was 30 times that of sodium benzoate. They concluded that sodium benzoate is a safe and effective alternative to lactulose in the treatment of acute portosystemic encephalopathy . However, sodium benzoate is not routinely used due to fear of high sodium load and no change in ammonia level after its use.

Rossi-Fanelli et al. [ 61 ] conducted a controlled study in two groups of 20 cir-rhotic patients with deep coma in order to compare the ef fi cacy of intravenous branched-chain amino acid solutions in 20% glucose (group A) vs. lactulose plus glucose in isocaloric amount (group B). Complete mental recovery was obtained in 70% of patients in group A and in 47% in group B. They concluded that, branched-chain amino acids are at least as effective as lactulose in deep hepatic coma.


However, in a meta-analysis of 11 randomized trials (556 patients) assessing BCAA vs. carbohydrates, neomycin/lactulose, or isonitrogenous control they found no evi-dence of an effect of BCAA on improvement of hepatic encephalopathy in trials with adequate generation of the allocation sequence (RR 1.01, 95% CI 0.84–1.23, three trials), adequate allocation concealment (RR 1.09, 95% CI 0.89–1.33, fi ve tri-als), or adequate double-blinding (RR 1.20, 95% CI 0.83–1.73, three trials). They did not fi nd convincing evidence that BCAA had a signi fi cant bene fi cial effect on patients with hepatic encephalopathy (Table 11.5 ) [ 62 ] .

Disaccharides for Primary Prophylaxis of Hepatic Encephalopathy

Certain patients are at risk of development of overt HE, such as patients with minimal hepatic encephalopathy and those with advanced liver disease [ 63– 65 ] . Recently, our group has shown in a randomized trial [ 66 ] involving 120 (48%) patients, receiving either lactulose ( n = 60) or no lactulose ( n = 60). Twenty (19%) of 105 patients, fol-lowed up for 12 months , developed an episode of overt HE. Six (11%) of 55 in the lactulose group and 14 (28%) of 50 in the no lactulose group ( p = 0.02) developed HE. Ten (20%) of 50 patients in the no lactulose group and 5 (9%) of 55 patients in the lactulose group died ( p = 0.16). On multivariate analysis, Child’s score and presence of MHE at baseline were signi fi cantly associated with development of HE. Lactulose is effective in the primary prevention of HE.

Variceal bleed is an important precipitating factor for HE in patients with cir-rhosis. In a randomized trial [ 67 ] , we enrolled 70 patients with acute variceal bleed into group 1 (lactulose, n = 35) and group 2 (no lactulose, n = 35). Nineteen (27%) patients developed HE, 5 patients (14%) in the lactulose group and 14 patients (40%) in no lactulose group ( p = 0.03). On multivariate analysis, only baseline arte-rial ammonia, blood requirement during hospital stay, and lactulose therapy were predictors for the development of HE. Hence, lactulose was effective in preventing HE in these patients. We, therefore, recommend lactulose (30–60 mL/day) so that patients pass two to three semiformed stools in a day .

Disaccharides for Secondary Prophylaxis of Hepatic Encephalopathy

The emergence of HE after transjugular intrahepatic portosystemic shunt (TIPS) is of major concern for patients undergoing this procedure for refractory ascites or for prevention of variceal rebleeding. This clinical complication tends to occur within the fi rst few days post-procedure.

Although the majority of post-TIPS HE episodes are mild and responsive to pharmacological therapy, there are some cases where intractable HE develops and


Tabl

e 11

.5

Dis

acch

arid

es v

s. o

ther

ther

apy

for

hepa

tic e

ncep

halo

path

y

Tri

al

Stud

y de

sign

N

o. o

f pa

tient

s Ty

pe o

f pa

tient

s T

reat

men

t A

sses

smen

t E

f fi ca

cy

Log

uerc

io e

t al.

[ 58 ]

Pa

ralle

l 40

C

HE

L

acto

baci

llus

SF68

/lact

ulos

e PS

E p

aram

eter

s,

adve

rse

even

ts

SF68

= la

ctul

ose

Sush

ma

et a

l. [ 5

9 ]

Para

llel

74

AH

E

Sodi

um b

enzo

ate/

lact

ulos

e M

orta

lity,

PSE

pa

ram

eter

s So

dium

be

nzoa

te =

lact

ulos

e Fi

acca

dori

[ 60

] Pa

ralle

l 23

A

HE

+ C

HE

B

CA

A/B

CA

A +

lact

ulos

e/la

ctul

ose

Clin

ical

gra

ding

B

CA

A +

lact

u-lo

se >

BC

AA

/lact

ulos

e R

ossi

-Fan

elli

[ 61 ]

Pa

ralle

l 40

A

HE

B

CA

A/la

ctul

ose

Clin

ical

gra

ding

B

CA

A =

lact

ulos

e


hospitalization is required. There are limited data on the use of drug therapy for the prophylaxis of HE after a TIPS procedure or in patients who have recovered from an episode of HE who may bene fi t from pharmacological prophylaxis to prevent future recurrences. Until recently, there has not been any conclusive evidence to support routine use of pharmacological prophylaxis for this purpose. Riggio et al. [ 68 ] conducted the fi rst randomized controlled trial utilizing lactitol or rifaximin as pharmacological prophylaxis for post-shunt HE. Seventy- fi ve consecutive patients with cirrhosis undergoing a TIPS procedure were randomized to receive lactitol 60 mL/day, rifaximin 1,200 mg/day or no treatment. Patients in the rifaximin or no-treatment groups were allowed administration of a sorbitol enema (120 mL) in cases of minimal bowel movement (<1 bowel movement/day). Treatments were contin-ued for 1 month post-TIPS or until the occurrence of an episode of HE. There was no signi fi cant difference in the rate of HE occurrence among the three patient groups ( p = 0.97).

Two recent clinical trials have been conducted to evaluate the ef fi cacy of lactu-lose or rifaximin used concomitantly with lactulose, as secondary prophylaxis of overt HE compared with placebo [ 69, 70 ] . Sharma et al. [ 69 ] conducted a single-center, open-label, randomized controlled trial in 125 cirrhotic patients who had recovered from at least one previous episode of HE. Patients were randomized to receive either lactulose 30–60 mL/day or placebo. Development of overt HE was the primary study endpoint. At the end of a median follow-up time of 14 months, signi fi cantly more patients in the placebo group (30 of 64 patients [46.8%]) than in the lactulose group (12 of 61 patients [19.6%]) developed HE ( p = 0.001).

In a recent multicenter double-blind randomized clinical trial to assess the sec-ondary prevention of HE, Bass et al. [ 70 ] enrolled 299 cirrhotic patients with a his-tory of at least two episodes of overt HE to receive either rifaximin (550 mg twice daily; n = 140) or placebo ( n = 159) for a period of 6 months. All enrolled patients had Model for End-Stage Liver Disease (MELD) scores of <25. More than 90% of patients in both groups were also maintained on concomitant lactulose therapy. A signi fi cantly lower percentage of patients in the rifaximin group (22.1%) experi-enced a breakthrough HE episode during the study period than in the placebo group (45.9%), with a hazard ratio (HR) of 0.42 (95% CI 0.28, 0.64; p < 0.001). In addi-tion, there was a signi fi cantly reduced risk of hospitalization in the rifaximin patient group when compared with placebo; 19 patients in the rifaximin group (13.6%) vs. 36 patients in the placebo group (22.6%), with a corresponding HR of 0.50 (95% CI 0.29, 0.87; p = 0.01). No signi fi cant difference in the incidence of adverse events was found between the two groups. Overall, this pivotal study has demonstrated a clinically relevant bene fi t of rifaximin as pharmacological prophylaxis of HE in cir-rhotic patients with a recent history of overt HE. The addition of rifaximin to a standard lactulose regimen may offer advantages in terms of decreasing risk of both breakthrough HE episodes as well as hospitalizations when compared with lactu-lose alone. Further, in a sub-analysis of patients from the United States and Canada, patients who received rifaximin 550 mg b.i.d. had signi fi cantly higher time-weighted average scores for overall QoL on the Chronic Liver Disease Questionnaire than those who received placebo ( p = 0.0093) [ 71 ] . The mean time-weighted average


QoL scores across all six subdomains of the Chronic Liver Disease Questionnaire were also signi fi cantly improved with rifaximin 550 mg b.i.d. compared with pla-cebo ( p < 0.05 for each) (Table 11.6 ). Hence, we recommend lactulose and rifaximin for the secondary prophylaxis of HE.

Conclusion

Current pharmacotherapy for the management of HE is fairly limited, mainly because of the complex and relatively limited understanding of the pathophysiology of the disorder. Although the evidence base supporting a pivotal role of ammonia is robust, in everyday clinical practice a consistent correlation between the concentra-tion of ammonia in the blood and the manifest symptoms of HE is not observed. More recently, the synergistic role of in fl ammation and infection in modulating the cerebral effects of ammonia has been shown to be important. The most commonly utilized pharmacological agents include the nonabsorbable disaccharides lactulose and lactitol, and the antimicrobial agent rifaximin. Recent literature has questioned the clinical ef fi cacy of disaccharides in improving morbidity and mortality in patients with HE and, although antimicrobial agents such as rifaximin have had an established role in the treatment of encephalopathy, its use in high-grade HE needs more data. Until we have more de fi nitive agents nonabsorbable disaccharide lactu-lose still continues to be the fi rst-line therapy for the prevention, treatment, and secondary prophylaxis of hepatic encephalopathy.

References

1. Ferenci P, Lockwood A, Mullen K, Tarter R, Weissenborn K, Blei AT. Hepatic encephalopathy—de fi nition, nomenclature, diagnosis, and quanti fi cation: fi nal report of the working party at the 11th World Congresses of Gastroenterology, Vienna, 1998. Hepatology. 2002;35:716–21.

2. Riordan SM, Williams R. Treatment of hepatic encephalopathy. N Engl J Med. 1997;337: 473–9.

Table 11.6 Disaccharides for secondary prophylaxis of hepatic encephalopathy

Trial Study design

No. of patients

Duration of treatment Assessment Ef fi cacy

Sharma et al. [ 69 ]

Lactulose (open-label)

140 14 months Psychometry and CFF

Lactulose > no treatment

Bass et al. [ 70 ]

Rifaximin + lactulose (randomized, double-blind, placebo-controlled)

299 6 HE clinical Rifaximin > placebo


3. Bajaj JS, Wade JB, Sanyal AJ. Spectrum of neurocognitive impairment in cirrhosis: implications for the assessment of hepatic encephalopathy. Hepatology. 2009;50(6):2014–21.

4. Bajaj JS, Hafeezullah M, Hoffmann RG, Saeian K. Minimal hepatic encephalopathy: a vehicle for accidents and traf fi c violations. Am J Gastroenterol. 2007;102:1903–9.

5. Groeneweg M, Quero JC, De Bruijn I, Hartmann IJC, Essink-bot MI, Hop WCJ, et al. Subclinical hepatic encephalopathy impairs daily functioning. Hepatology. 1998;28:45–9.

6. Bajaj JS, Stein AC, Dubinsky RM. What is driving the legal interest in hepatic encephalopathy? Clin Gastroenterol Hepatol. 2011;9(2):97–8.

7. Bajaj JS, Saeian K, Schubert CM, Hafeezullah M, Franco J, et al. Minimal hepatic encephal-opathy is associated with motor vehicle crashes: the reality beyond the driving test. Hepatology. 2009;50(4):1175–83.

8. Bismuth M, Funakoshi N, Cadranel JF, Blanc P. Hepatic encephalopathy: from pathophysiology to therapeutic management. Eur J Gastroenterol Hepatol. 2011;23(1):8–22.

9. Albrecht J, Zielińska M, Norenberg MD. Glutamine as a mediator of ammonia neurotoxicity: a critical appraisal. Biochem Pharmacol. 2010;80(9):1303–8.

10. Lockwood A, Yap E, Wong W. Cerebral ammonia metabolism in patients with severe liver disease and minimal hepatic encephalopathy. J Cereb Blood Flow Metab. 1991;11:337–41.

11. Shawcross DL, Olde Damink SW, Butterworth RF, Jalan R. Ammonia and hepatic encephal-opathy: the more things change, the more they remain the same. Metab Brain Dis. 2005;20(3): 169–79.

12. Haussinger D, Kircheis G, Fischer R, et al. Hepatic encephalopathy in chronic liver disease: a clinical manifestation of astrocyte swelling and low grade cerebral edema. J Hepatol. 2000;32: 1035–8.

13. Tanigami H, Rebel A, Martin LJ, et al. Effect of glutamine synthetase inhibition on astrocyte swelling and altered astroglial protein expression during hyperammonemia in rats. Neuroscience. 2005;131:437–49.

14. Cordoba J, Alonso J, Rovira A, Jacas C, Sanpedro F, Castells L, et al. The development of low-grade cerebral oedema in cirrhosis is supported by the evolution of 1H-magnetic resonance abnormalities after liver transplantation. J Hepatol. 2001;35:598–604.

15. Balata S, Olde Damink S, Ferguson K, Marshall I, Hayes P, Deutz N, et al. Induced hyperam-monemia alters neuropsychology, brain MR spectroscopy and magnetization transfer in cir-rhosis. Hepatology. 2003;37:931–9.

16. Blei AT, Cordoba J. Hepatic encephalopathy. Am J Gastroenterol. 2001;96:1968–76. 17. Riggio O, Balducci G, Ariosto F, et al. Lactitol in prevention of recurrent episodes of hepatic

encephalopathy in cirrhotic patients with portosystemic shunt. Dig Dis Sci. 1989;34(6):823–9. 18. Morgan MY, Hawley KE. Lactitol vs lactulose in the treatment of acute hepatic encephalopathy

in cirrhotic patients: a double-blind, randomized trial. Hepatology. 1987;7(6):1278–84. 19. Heredia D, Teres J, Orteu N, et al. Lactitol vs. lactulose in the treatment of chronic recurrent

portosystemic encephalopathy. J Hepatol. 1988;7:106–10. 20. Cordóba J, Blei AT. Treatment of hepatic encephalopathy. Am J Gastroenterol. 1997;92(9):

1429–39. 21. Clausen MR, Mortensen PB. Lactulose, disaccharides and colonic fl ora: clinical consequences.

Drugs. 1997;53(6):930–42. 22. Eroglu Y, Byrne W. Hepatic encephalopathy. Emerg Med Clin North Am. 2009;27:401–14. 23. Simmons F, Goldstein H, Boyle JD. A controlled clinical trial of lactulose in hepatic encephal-

opathy. Gastroenterology. 1970;59:827–32. 24. Rodgers Jr JB, Kiley JE, Balint JA. Comparison of results of long-term treatment of chronic

hepatic encephalopathy with lactulose and sorbitol. Am J Gastroenterol. 1973;60:459–65. 25. Corazza GR, Tacconi C, Zoli G, Somarolli M, D’Ambro A, Bernardi M. Use of pyridoxine-

alpha-ketoglutarate (PAK) in hepatic encephalopathy. Int J Clin Pharmacol Res. 1982;2:7–13. 26. Uribe M, Campollo O, Vargas F, Ravelli GP, Mundo F, Zapata L. Acidifying enemas (lactitol

and lactose) vs. nonacidifying enemas (tap water) to treat acute portosystemic encephalopathy: a double-blind, randomized clinical trial. Hepatology. 1987;7:639–43.


27. Horsmans Y, Solbreux PM, Daenens C, et al. Lactulose improves psychometric testing in cir-rhotic patients with subclinical encephalopathy. Aliment Pharmacol Ther. 1997;11(1):165–70.

28. Watanabe A, Sakai T, Sato S, et al. Clinical ef fi cacy of lactulose in cirrhotic patients with and without subclinical hepatic encephalopathy. Hepatology. 1997;26(6):1410–4.

29. Dhiman RK, Sawhney MS, Chawla YK, et al. Ef fi cacy of lactulose in cirrhotic patients with subclinical hepatic encephalopathy. Dig Dis Sci. 2000;45(8):1549–52.

30. Prasad S, Dhiman RK, Duseja A, et al. Lactulose improves cognitive functions and health-related quality of life in patients with cirrhosis who have minimal hepatic encephalopathy. Hepatology. 2007;45(3):549–59.

31. Als-Nielsen B, Gluud LL, Gluud C. Non-absorbable disaccharides for hepatic encephalopathy: systematic review of randomised trials. BMJ. 2004;328(7447):1046.

32. Als-Nielsen B, Gluud LL, Gluud C. Nonabsorbable disaccharides for hepatic encephalopathy. Cochrane Database Syst Rev. 2004;(2):CD003044.

33. Lanthier PL, Morgan MY. Lactitol in the treatment of chronic hepatic encephalopathy: an open comparison with lactulose. Gut. 1985;26:415–20.

34. Heredia D, Terés J, Orteu N, Rodés J. Lactitol vs. lactulose in the treatment of chronic recurrent portosystemic encephalopathy. J Hepatol. 1988;7(1):106–10.

35. Morgan MY, Alonso M, Stanger LC. Lactitol and lactulose for the treatment of subclinical hepatic encephalopathy in cirrhotic patients. A randomised, cross-over study. J Hepatol. 1989;8(2):208–17.

36. Riggio O, Balducci G, Ariosto F, Merli M, Pieche U, Pinto G, et al. Lactitol in prevention of recurrent episodes of hepatic encephalopathy in cirrhotic patients with portosystemic shunt. Dig Dis Sci. 1989;34(6):823–9.

37. Grandi M, Sacchetti C, Pederzoli S, Celani MF. A clinical comparative study of crystalline pure lactulose and powder pure lactitol in portosystemic encephalopathy of cirrhotic patients. Minerva Gastroenterol Dietol. 1991;37(4):225–30.

38. Pai CH, Huang YS, Jeng WC, Chan CY, Lee SD. Treatment of porto-systemic encephalopathy with lactitol versus lactulose: a randomized controlled study. Zhonghua Yi Xue Za Zhi (Taipei). 1995;55(1):31–6.

39. Blanc P, Daures JP, Rouillon JM, Peray P, Pierrugues R, et al. Lactitol or lactulose in the treatment of chronic hepatic encephalopathy: results of a meta-analysis. Hepatology. 1992;15(2): 222–8.

40. Cammà C, Fiorello F, Tinè F, Marchesini G, Fabbri A, et al. Lactitol in treatment of chronic hepatic encephalopathy. A meta-analysis. Dig Dis Sci. 1993;38(5):916–22.

41. Conn HO, Leevy CM, Vlacevic ZR, Rodgers JB, Maddrey WC, Seef L. Comparison of lactu-lose and neomycin in the treatment of chronic portosystemic encephalopathy. A double blind controlled trial. Gastroenterology. 1977;72:573–83.

42. Atterbury CE, Maddrey WC, Conn HO. Neomycin-sorbitol and lactulose in the treatment of acute portosystemic encephalopathy. A controlled, double-blind clinical trial. Am J Dig Dis. 1978;23:398–406.

43. Orlandi F, Freddara U, Candelaresi MT, Morettini A, Corazza GR, Di Simone A. Comparison between neomycin and lactulose in 173 patients with hepatic encephalopathy: a randomized clinical study. Dig Dis Sci. 1981;26:498–506.

44. Blanc P, Couderc M, Peray P, Liautard J, Larrey D, Michel H, et al. Lactitol versus vancomy-cin in the treatment of acute hepatic encephalopathy: a double blind, randomized trial [abstract]. Gut. 1993;34:46.

45. Mullen K, Prakash R. Rifaximin for the treatment of hepatic encephalopathy. Expert Rev Gastroenterol Hepatol. 2010;4(6):665–77.

46. Festi D, Mazzella G, Orsini M, et al. Rifaximin in the treatment of chronic hepatic encephalopa-thy: results of a multicenter study of ef fi cacy and safety. Curr Ther Res. 1993;54(5): 598–609.

47. Palmer M. The antibiotic rifaximin improves hepatic encephalopathy symptoms in patients with cirrhosis due to hepatitis C virus. Pract Gastroenterol. 2007;31(2):72–6.

48. Puxeddu A, Quartini M, Massimetti A, Ferrieri A. Rifaximin in the treatment of chronic hepatic encephalopathy. Curr Med Res Opin. 1995;13(5):274–81.


49. Sama C, Morselli-Labate AM, Pianta P, Lambertini L, Berardi S, Martini G. Clinical effects of rifaximin in patients with hepatic encephalopathy intolerant or nonresponsive to previous lactulose treatment: an open-label, pilot study. Curr Ther Res. 2004;65(5):413–22.

50. Bucci L, Palmieri GC. Double-blind, double-dummy comparison between treatment with rifaximin and lactulose in patients with medium to severe degree hepatic encephalopathy. Curr Med Res Opin. 1993;13(2):109–18.

51. Loguercio C, Federico A, De Girolamo V, Ferrieri A, Del Vicchio BD. Cyclic treatment of chronic hepatic encephalopathy with rifaximin. Results of a double-blind clinical study. Minerva Gastroenterol Dietol. 2003;49:53–62.

52. Massa P, Vallerino E, Dodero M. Treatment of hepatic encephalopathy with rifaximin: double blind, double dummy study versus lactulose. Eur J Clin Res. 1993;4:7–18.

53. Mas A, Rodes J, Sunyer L, Rodrigo L, Planas R, Vargas V. Comparison of rifaximin and lactitol in the treatment of acute hepatic encephalopathy: results of a randomized, double-blind, double-dummy, controlled clinical trial. J Hepatol. 2003;38:51–8.

54. Fera G, Agostinacchio F, Nigro M, et al. Rifaximin in the treatment of hepatic encephalopathy. Eur J Clin Res. 1993;4:57–66.

55. Leevy CB, Phillips JA. Hospitalizations during the use of rifaximin versus lactulose for the treatment of hepatic encephalopathy. Dig Dis Sci. 2007;52:737–41.

56. Paik YH, Lee KS, Han KH, et al. Comparison of rifaximin and lactulose for the treatment of hepatic encephalopathy: a prospective randomized study. Yonsei Med J. 2005;46(3):399–407.

57. Jiang Q, Jiang XH, Zheng MH, Jiang LM, Chen YP, Wang L. Rifaximin versus nonab-sorbable disaccharides in the management of hepatic encephalopathy: a meta-analysis. Eur J Gastroenterol Hepatol. 2008;20(11):1064–70.

58. Loguercio C, Del Vecchio Blanco C, Coltorti M. Enterococcus lactic acid bacteria strain SF68 and lactulose in hepatic encephalopathy: a controlled study. J Int Med Res. 1987;15(6):335–43.

59. Sushma S, Dasarathy S, Tandon RK, Jain S, Gupta S, Bhist MS. Sodium benzoate in the treat-ment of acute hepatic encephalopathy: a double-blind randomized trial. Hepatology. 1992;16(1): 138–44.

60. Fiaccadori F, Ghinelli F, Pelosi G, et al Selective amono acid solutions in hepatic encephalopa-thy treatment (a preliminary report). Ric Clin Lab. 1980;10(2):411–22.

61. Rossi-Fanelli F, Riggio O, Cangiano C, Cascino A, De Conciliis D, Merli M, et al. Branched-chain amino acids vs lactulose in the treatment of hepatic coma: a controlled study. Dig Dis Sci. 1982;27(10):929–35.

62. Als-Nielsen B, Koretz RL, Kjaergard LL, Gluud C. Branched-chain amino acids for hepatic encephalopathy. Cochrane Database Syst Rev. 2003;(2):CD001939.

63. Romero-Gomez M, Boza F, Garcia-Valdecasas MS, García E, Aguilar-Reina J. Subclinical hepatic encephalopathy predicts the development of overt hepatic encephalopathy. Am J Gastroenterol. 2001;96:2718–23.

64. Das A, Dhiman RK, Saraswat VA, Verma M, Naik SR. Prevalence and natural history of sub-clinical hepatic encephalopathy in cirrhosis. J Gastroenterol Hepatol. 2001;16:531–5.

65. Hartmann IJ, Groeneweg M, Quero JC, Beijeman SJ, de Man RA, Hop WC, et al. The prognostic signi fi cance of subclinical hepatic encephalopathy. Am J Gastroenterol. 2000;95:2029–34.

66. Sharma P, Agrawal A, Sharma BC, Sarin SK. Primary prophylaxis of hepatic encephalopathy in patients with cirrhosis: an open labeled randomized controlled trial of lactulose versus no lactulose. Indian J Gastroenterol. 2010;29 Suppl 1:A8.

67. Sharma P, Agrawal A, Sharma BC, Sarin SK. Prophylaxis of hepatic encephalopathy in acute variceal bleed: a randomized controlled trial of lactulose versus no lactulose. J Gastroenterol Hepatol. 2011;26(6):996–1003.

68. Riggio O, Masini A, Efrati C, et al. Pharmacological prophylaxis of hepatic encephalopathy after transjugular intrahepatic portosystemic shunt: a randomized controlled study. J Hepatol. 2005;42:674–9.

69. Sharma BC, Sharma P, Agrawal A, et al. Secondary prophylaxis of hepatic encephalopathy: an open-label randomized controlled trial of lactulose versus placebo. Gastroenterology. 2009;137:885–91.


70. Bass NM, Mullen KD, Sanyal A, et al. Rifaximin treatment in hepatic encephalopathy. N Engl J Med. 2010;362(12):1071–81.

71. Sanyal A, Bass N, Mullen K, et al. Rifaximin treatment improved quality of life in patients with hepatic encephalopathy: results of a large, randomized, placebo-controlled trial [abstract 15]. J Hepatol. 2010;52 Suppl 1:S7.


Keywords Lactulose • Rifaximin • Hepatic encephalopathy • Neomycin • Small intestinal bacterial overgrowth

Introduction

Long before lactulose was introduced as a therapy for hepatic encephalopathy (HE), an assortment of antibiotics were used to treat HE. Chlortetracycline was used in the 1950s [ 1, 2 ] and soon after neomycin became a commonly used treatment [ 3, 4 ] . Neomycin ef fi cacy was not originally tested in randomized controlled trials (RCT) and indeed no therapy was subjected to rigorous test in that era. Neomycin dosing was in the range of 1–3 g orally every 6 h for 5 days and the general impression was it had some ef fi cacy in the treatment of HE. Toxicity, particularly, in the form of hearing loss and renal failure was a major concern, especially if longer courses of therapy were employed. Lower doses of neomycin became popular for a time, but the publication of Strauss et al. seriously questioned the ef fi cacy of neomycin when correction of precipitating factors alone was found to be effective as neomycin plus the correction of precipitating factors [ 5 ] . Neomycin is still used to manage intractable recurrent HE, but less toxic alternative antibiotics are now available to reduce episodes of HE in patients who still have these bouts of HE despite lactulose therapy.

One very interesting facet of neomycin therapy that came to light in the 1950s was its relationship to intestinal glutaminase activity. Neomycin was de fi nitely shown to inhibit this enzyme. It was proposed that this action rather than its antibiotic properties was responsible for its effect on HE [ 6 ] . In general, the observation was


Chapter 12 Antibiotic Treatment for Hepatic Encephalopathy



that antibiotics with activity against anaerobic bacteria were more effective than those with antiaerobic bacteria activity. In the 1970s, based on very limited data, lactulose became the preferred therapy for the treatment of HE [ 7 ] . Nonetheless, metronidazole and vancomycin were shown to have ef fi cacy in the treatment of HE even though neither of these was compared to placebo in the RCT setting. Paromomycin and vancomycin also were featured as a treatment option for HE and other antibiotics were also proposed as possible therapies to employ.

Mechanism of Action of Antibiotics

The basic premise for the improvement of HE with antibiotics was simply that this therapy reduced ammonia generation in the gut from enteric bacteria. Whether erad-ication or reduction of bacterial fl ora acted primarily in the small or large bowel was a topic of considerable interest. Sherlock and coworkers and more recently Dhiman and coworkers have demonstrated that small bowel bacterial overgrowth (SBO) was common in cirrhotic patients [ 8, 9 ] . Could SBO be a major contributor to HE? Is some of the ef fi cacy of antibiotics due to suppression or clearance of small bowel bacteria? We still do not have an answer. However, it should be noted that less than 10% of oral metronidazole reaches the colon and yet this antibiotic is felt to have ef fi cacy in treating HE [ 10 ] . It can be further speculated that the main bacterial culprits for HE were anaerobes since vancomycin was also noted to be effective in treating lactulose-resistant HE [ 11 ] . This drug is no longer used because of the fear of induction of vancomycin-resistant enterococci (VRE). Nonetheless, its use was needed to support the concept that a nonabsorbable antibiotic with activity against anaerobic bacteria was a potentially effective therapy for HE. This association of antibiotics with anaerobic activity being possible effective therapy for HE still con-tinues to be observed (e.g.: nitosoxanide). However, there still is no clear evidence supporting eradication of small bowel bacteria alone being the main mechanism of action of these types of antibiotics. Most are in association with major effects on colonic fl ora which may provide the setting for clostridium dif fi cile overgrowth.

Returning to neomycin therapy as mentioned previously, its main mechanism of action appears to have been (at least at the very high doses used) inhibitor of intes-tinal glutaminase. As demonstrated in rat experiments, the majority of portal vein ammonia comes from glutaminase activity and not from intestinal bacteria. Neomycin was also associated with reports of villous atrophy which potentially could have eradicated the glutaminase activity [ 12, 13 ] . However, the direct enzyme inhibiting action seems a more likely cause of reduction in ammonia coming from the gut. Certainly, the antianaerobic bacterial action of neomycin and possibly also paromomycin seems less important in the reports of improvement of the HE with oral amino glycosides.

Despite the data in germ-free rats, it seems possible that suppression of intestinal fl ora does reduce production of ammonia by preventing breakdown of nitrogen-containing compounds. These would arise to some extent from partially hydrolyzed proteins

16112 Antibiotic Treatment for Hepatic Encephalopathy

from the diet and exudates from the intestinal tract. Fecal incubation studies have shown signi fi cant production of ammonia when hydrolyzed proteins are added to fecal incubation containing anaerobic fl ora. If the small bowel motility is reduced in cirrhotic patients, as demonstrated in at least two studies, then the risk of SBO is increased [ 8, 9 ] . More studies are needed to establish if SBO is prevalent in cirrhotics.

A peculiarity of antibiotic rifaximin is its differential bioavailability in the small as opposed to large bowel. Rifaximin is largely insoluble unless exposed to bile salts. Hence, the drug is an active antibacterial (aerobic and anaerobic) agent in the small bowel. When bile salts are reabsorbed, its antibacterial activity is signi fi cantly reduced. This is evident in the generally mild effect on colonic fl ora induced by the antibiotic. However, it may be important to consider that bile salt delivery to the gut may be markedly reduced, especially in cholestatic liver disease. Potentially this may reduce the ef fi cacy of rifaximin in this type of situation.

Published Data on Antibiotic Therapy for Hepatic Encephalopathy

Most, if not all, of the literature on the ef fi cacy of antibiotics in the treatment of HE is not placebo controlled. Majority of the studies compare antibiotic therapy to nonabsorbed disaccharides or to other antibiotics. When antibiotics have been compared to nonabsorbable disaccharides, there is a trend in favor of greater ef fi cacy of antibiotics. However, the toxicity of many antibiotics used in the past was felt to outweigh the possible superiority of this form of treatment. Table 12.1 lists the antibiotics with recommended doses from various studies (see Table 12.2 ).

The systematic analysis published by Als-Nielsen et al. is a useful resource [ 21 ] . Some criticism of this study of this study has been voiced in that some published studies were arbitrarily excluded from the system analysis. Nonetheless, this review had a major impact on this perspective of the ef fi cacy of agents to treat HE. Primarily what was noted was the extreme paucity of data ful fi lling RCT criteria with pla-cebo control. This was very important because of the already entrenched view that lactulose was a well-proven therapy. This perspective was so strongly held that

Table 12.1 Lists the antibiotics studied for the treatment of hepatic encephalopathy

FDA approved • Rifaximin 550 mg PO twice daily (Mainly recommended for prophylaxis of recurrent overt

HE) [ 14 ] Off label agents • Metronidazole 250 mg four times daily [ 10 ] • Neomycin 2–4.5 g daily in divided doses [ 3, 7 ] • Vancomycin 1–2 g daily in divided doses [ 15 ] • Paromomycin 1 g four times a day [ 16 ] • Nitazoxanide 500 mg twice daily [ 14 ]


Table 12.2 Summarizes important trials involving antibiotics for treatment of hepatic encephalopathy

Investigators Study details

Intervention (number of study subjects in each arm) Conclusion

Bass et al. [ 17 ] Double-blind placebo-controlled multicentric study. Duration—6 months

Rifaximin 550 mg bid (140) vs. placebo (159) (>90% of subjects in both groups were on lactulose)

Rifaximin signi fi cantly reduced the risk of an episode of hepatic encephalopathy and reduced the risk of hospitalization because of HE

Mas et al. [ 18 ] Randomized double-blind double dummy study. Duration—5–10 days

Rifaximin 1,200 mg/day (50) vs. lactitol 60 g/day (53)

Rifaximin is a safe alternative therapy to lactitol in the treatment of acute hepatic encephalopathy

Strauss et al. [ 5 ] Randomized double-blind study. Duration—5 days

Neomycin 1.5 g q6 (20) vs. placebo (19)

Compared to placebo (with correction of precipitat-ing factors) neomycin shortened the duration of hepatic encephalopa-thy but this difference was not statistically signi fi cant

Parini et al. [ 19 ] Randomized study in acute episode of hepatic encephalopathy. Duration—10 days

Paromomycin 1,500 mg/day (15) vs. rifaximin 1,200 mg/day (15)

Rifaximin proved to be as effective as paromomy-cin in treating acute episode of hepatic encephalopathy

Pedretti et al. [ 20 ] Randomized study. Duration—21 days

Rifaximin 400 mg q 8 (15) vs. neomycin 1 g q 8 (15)

Rifaximin is at least as effective as neomycin in achieving clinical improvement in hepatic encephalopathy and reducing ammonia levels

Tarao et al. [ 15 ] Randomized double-blind crossover study. Duration—8 weeks

Vancomycin 2 g q 12 h (12) vs. lactulose (12)

Vancomycin seems to be effective in chronic portal systemic encephalopathy in patients who are not helped by lactulose alone

Morgan et al. [ 10 ] Randomized double-blind study. Duration—7 days

Neomycin 1 g Q6 (9) vs. metronidazole 200 mg Q 6 (9)

Metronidazole is as effective as neomycin in the treatment of hepatic encephalopathy

Conn et al. [ 7 ] Randomized double-blind double dummy

Neomycin 1 g q 8 (33) vs. lactulose (33)

Neomycin is as effective in the treatment of hepatic encephalopathy

16312 Antibiotic Treatment for Hepatic Encephalopathy

there was a virtual ban on placebo-controlled trials [ 22 ] . This factored strongly in the design of a recent trial of rifaximin treatment of patients at risk for recurrent bouts of HE [ 20 ] . Over 90% of patients continued to stay on lactulose while rifaximin or placebo was added to their therapeutic regimen. The 58% reduction in further episodes of overt HE clearly indicated that it had a signi fi cant therapeutic action.

References

1. Mc Jr DW. Metabolism and toxicity of ammonia. N Engl J Med. 1957;257(22):1076–81. 2. Martini GA, Strohmeyer G, Doelle W. [The treatment of hepatic coma with antibiotics

(chlortetracycline, neomycin)]. Medizinische. 1959;52:2549–53. 3. Dawson AM, Mc LJ, Sherlock S. Neomycin in the treatment of hepatic coma. Lancet.

1957;273(7008):1262–8. 4. Summerskill WH. Hepatic coma in liver failure and gastro-intestinal haemorrhage treated with

neomycin. Br Med J. 1958;2(5108):1322–5. 5. Strauss E, Tramote R, Silva EP, Caly WR, Honain NZ, Maffei RA, et al. Double-blind randomized

clinical trial comparing neomycin and placebo in the treatment of exogenous hepatic enceph-alopathy. Hepatogastroenterology. 1992;39(6):542–5.

6. Hawkins RA, Jessy J, Mans AM, Chedid A, DeJoseph MR. Neomycin reduces the intestinal production of ammonia from glutamine. Adv Exp Med Biol. 1994;368:125–34.

7. Conn HO, Leevy CM, Vlahcevic ZR, Rodgers JB, Maddrey WC, Seeff L, et al. Comparison of lactulose and neomycin in the treatment of chronic portal-systemic encephalopathy. A double blind controlled trial. Gastroenterology. 1977;72(4 Pt 1):573–83.

8. Martini GA, Phear EA, Ruebner B, Sherlock S. The bacterial content of the small intestine in nor-mal and cirrhotic subjects: relation to methionine toxicity. Clin Sci (Lond). 1957;16(1):35–51.

9. Gupta A, Dhiman RK, Kumari S, Rana S, Agarwal R, Duseja A, et al. Role of small intestinal bacterial overgrowth and delayed gastrointestinal transit time in cirrhotic patients with minimal hepatic encephalopathy. J Hepatol. 2010;53(5):849–55.

10. Morgan MH, Read AE, Speller DC. Treatment of hepatic encephalopathy with metronidazole. Gut. 1982;23(1):1–7.

11. Tarao K, Ikeda T, Hayashi K, Sakurai A. Successful use of vancomycin hydrochloride in the treatment of lactulose-resistant chronic hepatic encephalopathy. J Gastroenterol Hepatol. 1989;4 Suppl 1:284–6.

12. Faloon WW, Jacobson ED. Malabsorption during neomycin administration. Gastroenterology. 1961;40:447–8.

13. Jacobson ED, Faloon WW. Malasorptive effects of neomycin in commonly used doses. JAMA. 1961;175:187–90.

14. Basu AP, Rayapudi K, Estevez J, Brown RS. A pilot study utilizing nitazoxanide for hepatic encephalopathy in chronic liver disease program and abstracts of the 59th annual meeting of the American Association for the study of liver diseases (abstract), 31 Oct–4 Nov; 2008. p. 1742.

15. Tarao K, Ikeda T, Hayashi K, Sakurai A, Okada T, Ito T, et al. Successful use of vancomycin hydrochloride in the treatment of lactulose resistant chronic hepatic encephalopathy. Gut. 1990;31(6):702–6.

16. Tromm A, Griga T, Greving I, Hilden H, Huppe D, Schwegler U, et al. Orthograde whole gut irrigation with mannite versus paromomycine+lactulose as prophylaxis of hepatic encephal-opathy in patients with cirrhosis and upper gastrointestinal bleeding: results of a controlled randomized trial. Hepatogastroenterology. 2000;47(32):473–7.



18. Mas A, Rodes J, Sunyer L, Rodrigo L, Planas R, Vargas V, et al. Comparison of rifaximin and lactitol in the treatment of acute hepatic encephalopathy: results of a randomized, double-blind, double-dummy, controlled clinical trial. J Hepatol. 2003;38(1):51–8.

19. Parini P, Cipolla A, Ronchi M, Roda A. Effect of rifaximin and paromomycin in the treatment of portal-systemic encephalopathy. Curr Ther Res. 1992;52(1):34–9.

20. Pedretti G, Calzetti C, Missale G, Fiaccadori F. Rifaximin versus neomycin on hyperammoniemia in chronic portal systemic encephalopathy of cirrhotics. A double-blind, randomized trial. Ital J Gastroenterol. 1991;23(4):175–8.

21. Als-Nielsen B, Gluud LL, Gluud C. Non-absorbable disaccharides for hepatic encephalopathy: systematic review of randomised trials. BMJ. 2004;328(7447):1046.

22. Mullen KD, Amodio P, Morgan MY. Therapeutic studies in hepatic encephalopathy. Metab Brain Dis. 2007;22(3–4):407–23.


Keywords Hepatic encephalopathy • Ornithine phenylacetate • Acute liver failure • Brain edema • Ammonia • Glutaminase • Glutamine synthetase • ADMA • Nitric oxide • NF k B

Introduction

Although the exact pathophysiological mechanisms of hepatic encephalopathy (HE) remain the subject of investigation, studies over the past 100 years have dem-onstrated a central role of ammonia. The mechanisms include ammonia-induced changes in neurotransmitter synthesis and release, neuronal oxidative stress, impaired mitochondrial function, and osmotic disturbances resulting from astrocytic metabolism of ammonia to glutamine. Systemic hyperammonemia has been largely found in patients with HE with underlying cirrhosis and acute liver failure (ALF).

Neuropathological examination of the brains obtained from patients who died with HE shows that astrocytes are the main cells to show physical alterations [ 1 ] . Patients with ALF develop raised intracranial pressure (ICP), which uncorrected may result in cerebral herniation, culminating in the death of about 30% of patients [ 2 ] . In patients with ALF, the astrocytes are swollen and in cirrhosis these cells show changes in their morphology to Alzheimer type II astrocytosis [ 3 ] . Similar changes can be induced in cultured astrocytes following incubation with ammonia [ 1, 4 ] . Furthermore, infusion of ammonia into rats with portacaval shunt results in brain swelling, and ammonia is thought to produce astrocytic edema through the ammonia–glutamine brain swelling hypothesis [ 5 ] .

M. Jover-Cobos, PhD • N. A. Davies, PhD, BSc • Y. Shari fi , MD, BAO, BCh, LRCP, SI&MRCP (UK) • R. Jalan, MBBS, MD, PhD, FRCPE, FRCP (*) UCL Institute of Hepatology , Royal Free Hospital, University College of London, Upper Third UCL Medical School , Pond Street , London NW3 2PF , UK e-mail: [email protected]

Chapter 13 Ornithine Phenylacetate: A Novel Strategy for the Treatment of Hepatic Encephalopathy

Maria Jover-Cobos , Nathan A. Davies , Yalda Shari fi , and Rajiv Jalan

166 M. Jover-Cobos et al.

Minimal hepatic encephalopathy (MHE) is a clinical condition that occurs in patients with cirrhosis and is de fi ned by the existence of a series of neurophysiological changes that go unnoticed in routine examination and has a strong impact on quality of life, altering memory, concentration, and attention. The increase in brain water correlates with the severity of MHE suggesting that this is important in its patho-genesis [ 6 ] . Direct evidence for the ammonia hypothesis was provided in patients with cirrhosis. In this study, hyperammonemia induced by the administration of amino acid solution mimicking the hemoglobin (emulating gastrointestinal bleeding) alters neuropsychology, brain magnetic resonance spectroscopy (MRS), and magneti-zation transfer ratio (MTR) in cirrhotic patients [ 7 ] . Other studies con fi rmed that a high arterial ammonia level predicts brain herniation, clinical manifestations of cerebral edema, increased ICP, and mortality in ALF patients [ 8– 11 ] .

Studies in patients and animal models have also indicated a role for in fl ammation in the pathogenesis of HE. However, it has been shown that induced hyperammonemia on the background of in fl ammation produces HE indicating that the effects of ammonia are synergistic with in fl ammation [ 12, 13 ] . Further evidence for the synergy between ammonia and in fl ammation has more recently been provided in animal studies suggesting that hyperammonemia may prime the brain to the effects of in fl ammation and alter the NO-cGMP pathway [ 14, 15 ] . HE treatment remains an unmet clinical need [ 16– 19 ] . Hence, ammonia reduction remains an important therapeutic target for the treatment of HE in liver disease. Recent studies using a novel therapeutic approach, ornithine phenylacetate (OP), may provide a useful treatment for patients with hyperammonemia.

Interorgan Ammonia Metabolism

The main mechanism for ammonia removal is urea production by hepatocytes. In liver disease, this function is compromised resulting in elevated ammonia levels, and other ammonia-regulating pathways in multiple organs assume important signi fi cance; see Fig. 13.1 [ 20 ] .

Studies focusing on interorgan ammonia metabolism in patients with cirrhosis indicate that the liver, muscles, kidney, and the small bowel are important in regulating the circulating levels of ammonia. Contrary to popular belief, it has been shown that at least 50–60% of total gut ammonia is derived from uptake of glutamine, which is metabolized to glutamate and ammonia by the enzyme glutaminase (GA) [ 21, 22 ] . Ammonia that would normally be converted to urea by the liver increases to toxic levels. In this situation, the enzyme glutamine synthetase (GS) plays a pivotal role in ammonia detoxi fi cation, effectively removing ammonia during the conversion of glutamate to glutamine [ 23 ] . Studies of the administration of l -ornithine l -aspartate (LOLA) and OP are based on using GS as a major alternative ammonia detoxi fi cation pathway. Antibiotics, probiotics, and symbiotic have been used as modulators of intestinal ammoniagenesis as well as in the prevention of systemic in fl ammation. These studies are based on the hypothesis that luminal bacteria produce the majority

16713 Ornithine Phenylacetate: A Novel Strategy for the Treatment…

of ammonia (gut sterilization). Lactulose has been the most popular treatment, but there is little evidence to support routine use [ 24 ] ; it offers no clear bene fi t in ALF [ 25 ] , where HE remains the major determinant of death [ 26 ] . Current approaches for treatment of HE are interventions targeting in fl ammation such as the use of hypothermia, and antibiotics such as Rifaximin. These treatments have shown some promise but the Rifaximin approach thus far has not been shown to successfully reduce ammonia levels [ 27 ] . Hence, GS and GA are current and future targets for therapy.

Ornithine Phenylacetate as a New Treatment for Hepatic Encephalopathy

Leading the Hypothesis

Currently, there is no speci fi c treatment of proven value for Type A HE and only liver transplantation remains a de fi nitive treatment for long-term bene fi t. Studies in animal models of liver failure suggested that the administration of a mixture of the amino-acids, LOLA, is associated with a lowering of plasma ammonia [ 23 ] . It is thought that the mechanism represents the conversion of l -ornithine to glutamate in

Fig. 13.1 Interorgan metabolism in health ( a ) and cirrhosis ( b )


the muscle, suggesting that the muscle could be targeted as an alternative site of ammonia detoxi fi cation [ 17, 23 ] . A large, placebo-controlled trial in ALF failed to show any bene fi t on ammonia level, encephalopathy grade, or survival [ 28 ] . In addi-tion, the role of aspartate remains unclear. Aspartate infusions in animals were not shown to result in a reduction in ammonia levels indicating that aspartate was unlikely to be the precursor of glutamate/glutamine and that ornithine was likely to be the active component of LOLA.

According to the above stated reasoning, the administration of LOLA would generate glutamine, which would only temporarily reduce ammonia, as this glutamine would be recycled in the small bowel to produce more ammonia [ 29 ] . Phenylacetate and its prodrug phenylbutyrate ( converted to phenylacetate in vivo) have been used for the hyperammonemia which occurs due to urea cycle enzyme de fi ciencies [ 30 ] . Phenylacetate combines covalently with the glutamine derived from glutamate to produce phenylacetylglutamine which is excreted by the kidneys. However, this therapy has not been attempted previously in cirrhosis as these patients do not have increased glutamine levels. The studies of interorgan ammonia traf fi cking, the lessons from LOLA observations, and the current use of phenylacetate to treat urea cycle disorders have led to the hypothesis. The concomitant administration of ornithine and phenylacetate act synergistically to produce a sustained reduction in ammonia concentration [ 29 ] .

The Mechanism of Action of Ornithine Phenylacetate

Decreasing Plasma Levels of Ammonia: Direct Effect on Ammonia Metabolism Enzymes in Liver Failure

In preliminary studies, it has been shown that the combination of ornithine with phenylacetate to treat hyperammonemia in cirrhosis is effective in animal models. Administration of OP results in increased conversion of glutamate to glutamine by stimulation of GS activity in the muscle with the subsequent excretion of pheny-lacetylglutamine in the urine, a reaction in which one molecule of ammonia is removed. GA has been found to contribute to hyperammonemia in cirrhosis and in MHE animal models [ 21, 31 ] . It has also been discovered that variations in the promoter region of the GA gene is associated with the development of HE in a cohort of patients with cirrhosis [ 32 ] . These fi ndings suggest developing approaches to target GA to prevent ammonia release and HE as a valid therapeutic strategy. Recent data show that OP treatment for 5 days intraperitoneally resulted in normalization of GA activity in the gut, indicating that OP effectively restricts the production of in vivo ammonia in a cirrhotic model [ 33 ] . Mechanism of action of OP on the metabolism of ammonia is shown in Fig. 13.2 .


Decreasing Brain Edema and Motor-Evoked Potentials

Cytotoxic brain edema and intracranial hypertension occurring in encephalopathy ALF patients account for a large number of deaths owing to cerebral herniation. It has been shown that in chronic liver failure there is a low-grade brain edema [ 34 ] that is resolved after transplantation. In this novel approach to targeting the altered interorgan ammonia metabolism in liver failure, OP utilizes the activity of GS to trap ammonia as glutamine and phenylacetate facilitates its excretion as pheny-lacetylglutamine [ 11– 13 ] . Effectiveness of this approach with OP has been con fi rmed in animal models of cirrhosis and ALF. The reduction ( » 50%) of plasma ammonia was associated with (a) an improvement in grade of HE in cirrhotic patients and (b) a reduction in ICP in ALF. OP treatment reduced ammonia concentrations signi fi cantly which was associated with a reduction in brain water and the brain myo-inositol levels were signi fi cant increased, showing an improvement in brain metabolism [ 29, 35 ] . In a devascularized pig model of ALF the rise in arterial ammonia was attenuated with OP which was accompanied by a signi fi cant decrease in extracellular brain ammonia and prevention of intracranial hypertension in pigs with ALF [ 36 ] .

Physical symptoms of MHE have been detected by motor-evoked potentials (MEP) which examines the function of signal transmission along the nerve, which is perturbed by low-grade brain edema. Similar disturbances have been found in patients with cirrhosis using magnetic resonance (MR), with signs compatible with low-grade edema along the corticospinal tract. These abnormalities were related to functional impairment detected by transcranial magnetic stimulation and were found to be reversed after liver transplantation. Recently, the assessment of MEP in

Fig. 13.2 Mechanism of action of OP in GS and GA enzymes. GS is stimulated in muscle by glutamate increased levels. At the same time PAGN is formed and excreted in the urine. In addition, GA is restored to normal levels in the gut


awake rats has been validated to monitor HE in animal models of liver failure (portacaval anastomosis—PCA) and precipitated HE (simulated gastrointestinal bleed—GiB). These models have been utilized to test the ef fi cacy of OP [ 37 ] , dem-onstrating that OP treatment prevents the neurophysiological abnormalities induced by the GiB insult in the PCA animals. Administration of OP over differing time periods (3 h and 3 days) as a pretreatment prevents the decrease in the amplitude and increase in MEP latency at 6 h post GiB [ 38 ] .

Indirect Effect of Ammonia Metabolism: Cytokines, Nitric Oxide/ADMA In fl ammation Pathway in the Brain

In cirrhotic patients it has been shown that the effects of hyperammonemia are synergistic with in fl ammation [ 13 ] . The effects on cell swelling by cytokines in ammonia-sensitized cultured astrocytes have also been shown [ 12 ] . However, the mechanisms by which ammonia produces brain swelling are still subject of much investigation. Although the effects on in fl ammatory processes have been found to contribute to the formation of cerebral edema, it is not clear whether ammonia promotes in fl ammation or both are independent factors. In fl ammatory pathways identi fi ed as contributing to the edema include cyclo-oxygenase, nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signaling, and cytokine release [ 34, 39, 40 ] .

Hyperammonemia could increase blood–brain-barrier permeability to systemic cytokines. It is also possible that several factors associated with the systemic in fl ammatory response syndrome could modulate brain dysfunction induced by hyperammonemia. These processes may help to explain the differences that some-times exist between lower ammonia levels and observed brain impairment in some patients. It has been shown that the presence of HE grade 3/4 correlates better with in fl ammation than with ammonia plasma levels [ 41 ] , though extracellular brain ammonia levels may be signi fi cantly higher. One recent study showed that in a cir-rhosis animal model in which plasma and brain cytokines were markedly elevated following administration of lipopolysaccharide (LPS), pretreatment with OP pre-vented increased levels of TNF a and IL-6 (trend) in plasma and in brain induced by LPS. Moreover, OP reduced LPS-induced development of precoma/coma and wors-ening of brain edema. It is well known that the transcription of NF k B directly increases proin fl ammatory cytokines and leads to induction of nitric oxide syn-thase [ 42 ] . OP reduced iNOS and NF k B expressions in cortical brain of cirrhotic animals indicating that ammonia reduction may modulate neuroin fl ammation [ 43 ] .

In cirrhosis, a paradox exists between reduced intrahepatic NO generation and excess NO in the splanchnic circulation. Splanchnic vasodilatation leads to vasocon-striction of numerous vascular beds, including the liver, kidneys, and has signi fi cant effects on the brain. Asymmetric dimethylarginine (ADMA) is an endogenous inhibi-tor of eNOS (endothelial nitric oxide synthase), the levels of which are increased in liver failure [ 44, 45 ] . It has been shown that treatment of cirrhotic rats with OP resulted in restoration of the NOS pathways (reduction in ADMA levels, increased eNOS activity, reduced caveolin-1) [ 43 ] . The reduction in arterial ammonia concentration


with OP may prevent LPS-induced worsening of HE and brain edema. It was therefore not surprising to note that treatment of animals with OP resulted also in restoring nitric oxide signaling (see Fig. 13.3 ).

Conclusions

In summary, the mechanism by which OP directly reduces ammonia levels in cirrhosis is by increasing muscle glutamine synthesis activity, subsequently trapping and increasing ammonia excretion as phenylacetylglutamine, with the concomitant normalization of gut glutaminase activity. The reduction on ammonia (by OP) leads to a reduction in ICP in ALF and is associated with an improvement in in fl ammation and NO pathways in the context of chronic liver disease. Moreover, OP modulates iNOS and NF k B mechanisms and prevents LPS-induced brain edema in cirrhotic rats. Studies to date have indicated that OP is safe and patient studies in MHE and HE is needed to establish OP as a treatment for this signi fi cant complication of liver disease.

Fig. 13.3 Sites of action of OP on the neuroin fl ammatory cascade


Con fl ict of Interest UCL has licensed its invention ornithine phenylacetate in hepatic encephal-

opathy to Ocera and Prof. Jalan is the named inventor on the patents.

References

1. Martinez-Hernandez A, Bell KP, Norenberg MD. Glutamine synthetase: glial localization in brain. Science. 1977;195:1356–8.

2. Jalan R. Intracranial hypertension in acute liver failure: pathophysiological basis of rational management. Semin Liver Dis. 2003;23:271–82.

3. Neary JT, del Pilar Gutierrez M, Norenberg LO, Norenberg MD. Protein phosphorylation in primary astrocyte cultures treated with and without dibutyryl cyclic AMP. Brain Res. 1987;410:164–8.

4. Kato M, Hughes RD, Keays RT, Williams R. Electron microscopic study of brain capillaries in cerebral edema from fulminant hepatic failure. Hepatology. 1992;15:1060–6.


6. Cordoba J, Alonso J, Rovira A, Jacas C, Sanpedro F, Castells L, et al. The development of low-grade cerebral edema in cirrhosis is supported by the evolution of (1)H-magnetic resonance abnormalities after liver transplantation. J Hepatol. 2001;35:598–604.

7. Balata S, Olde Damink SW, Ferguson K, Marshall I, Hayes PC, Deutz NE, et al. Induced hyperammonemia alters neuropsychology, brain MR spectroscopy and magnetization transfer in cirrhosis. Hepatology. 2003;37:931–9.

8. Clemmesen JO, Larsen FS, Kondrup J, Hansen BA, Ott P. Cerebral herniation in patients with acute liver failure is correlated with arterial ammonia concentration. Hepatology. 1999;29:648–53.

9. Jalan R, Olde Damink SW, Deutz NE, Hayes PC, Lee A. Moderate hypothermia in patients with acute liver failure and uncontrolled intracranial hypertension. Gastroenterology. 2004;127:1338–46.

10. Bhatia V, Singh R, Acharya SK. Predictive value of arterial ammonia for complications and outcome in acute liver failure. Gut. 2006;55:98–104.

11. Bernal W, Hall C, Karvellas CJ, Auzinger G, Sizer E, Wendon J. Arterial ammonia and clinical risk factors for encephalopathy and intracranial hypertension in acute liver failure. Hepatology. 2007;46:1844–52.

12. Rama Rao KV, Jayakumar AR, Tong X, Alvarez VM, Norenberg MD. Marked potentiation of cell swelling by cytokines in ammonia-sensitized cultured astrocytes. J Neuroin fl ammation. 2010;7:66.

13. Shawcross DL, Davies NA, Williams R, Jalan R. Systemic in fl ammatory response exacerbates the neuropsychological effects of induced hyperammonemia in cirrhosis. J Hepatol. 2004;40:247–54.

14. Wong D, Dorovini-Zis K, Vincent SR. Cytokines, nitric oxide, and cGMP modulate the perme-ability of an in vitro model of the human blood-brain barrier. Exp Neurol. 2004;190:446–55.

15. Wright G, Davies NA, Shawcross DL, Hodges SJ, Zwingmann C, Brooks HF, et al. Endotoxemia produces coma and brain swelling in bile duct ligated rats. Hepatology. 2007;45:1517–26.

16. Ortiz M, Jacas C, Cordoba J. Minimal hepatic encephalopathy: diagnosis, clinical signi fi cance and recommendations. J Hepatol. 2005;42(Suppl):S45–53.

17. Shawcross D, Jalan R. The pathophysiologic basis of hepatic encephalopathy: central role for ammonia and in fl ammation. Cell Mol Life Sci. 2005;62:2295–304.

18. Gerber T, Schomerus H. Hepatic encephalopathy in liver cirrhosis: pathogenesis, diagnosis and management. Drugs. 2000;60:1353–70.


19. Blei AT. Diagnosis and treatment of hepatic encephalopathy. Baillieres Best Pract Res Clin Gastroenterol. 2000;14:959–74.

20. Wright G, Noiret L, Olde Damink SW, Jalan R. Interorgan ammonia metabolism in liver failure: the basis of current and future therapies. Liver Int. 2011;31(2):163–75.

21. Romero-Gomez M, Ramos-Guerrero R, Grande L, de Teran LC, Corpas R, Camacho I, et al. Intestinal glutaminase activity is increased in liver cirrhosis and correlates with minimal hepatic encephalopathy. J Hepatol. 2004;41:49–54.

22. Olde Damink SW, Jalan R, Redhead DN, Hayes PC, Deutz NE, Soeters PB. Interorgan ammonia and amino acid metabolism in metabolically stable patients with cirrhosis and a TIPSS. Hepatology. 2002;36:1163–71.

23. Rose C, Michalak A, Rao KV, Quack G, Kircheis G, Butterworth RF. L-ornithine-L-aspartate lowers plasma and cerebrospinal fl uid ammonia and prevents brain edema in rats with acute liver failure. Hepatology. 1999;30:636–40.

24. Als-Nielsen B, Gluud LL, Gluud C. Non-absorbable disaccharides for hepatic encephalopathy: systematic review of randomised trials. BMJ. 2004;328:1046.

25. Alba L, Hay J, Lee WM. Lactulose therapy in acute liver failure. J Hepatol. 2002;36:33A. 26. Lee WM, Squires Jr RH, Nyberg SL, Doo E, Hoofnagle JH. Acute liver failure: summary of a

workshop. Hepatology. 2008;47:1401–15. 27. Bass NM, Mullen KD, Sanyal A, Poordad F, Neff G, Leevy CB, et al. Rifaximin treatment in

hepatic encephalopathy. N Engl J Med. 2010;362:1071–81. 28. Acharya SK, Bhatia V, Sreenivas V, Khanal S, Panda SK. Ef fi cacy of L-ornithine L-aspartate

in acute liver failure: a doubleblind, randomized, placebo-controlled study. Gastroenterology. 2009;136(7):2159–68.

29. Jalan R, Wright G, Davies NA, Hodges SJ. L-Ornithine phenylacetate (OP): a novel treatment for hyperammonemia and hepatic encephalopathy. Med Hypotheses. 2007;69:1064–9.

30. Smith I. The treatment of inborn errors of the urea cycle. Nature. 1981;291:378–80. 31. Romero-Gomez M, Jover M, Diaz-Gomez D, de Teran LC, Rodrigo R, Camacho I, et al.

Phosphate-activated glutaminase activity is enhanced in brain, intestine and kidneys of rats following portacaval anastomosis. World J Gastroenterol. 2006;12:2406–11.

32. Romero-Gomez M, Jover M, Del Campo JA, Royo JL, Hoyas E, Galan JJ, et al. Variations in the promoter region of the glutaminase gene and the development of hepatic encephalopathy in patients with cirrhosis: a cohort study. Ann Intern Med. 2010;153:281–8.

33. Jover-Cobos M, Noiret L, Habtesion A, Balasubramaniyan V, Shari fi Y, Romero-Gómez M, et al. The mechanism behind synergistic action of L-ornithine and phenylacetate to reduce ammonia in Cirrhotic rats. Hepatology. 2010;52(Suppl):893A.

34. Rodrigo R, Cauli O, Gomez-Pinedo U, Agusti A, Hernandez-Rabaza V, Garcia-Verdugo JM, et al. Hyperammonemia induces neuroin fl ammation that contributes to cognitive impairment in rats with hepatic encephalopathy. Gastroenterology. 2010;139:675–84.

35. Davies N, Wright G, Ytrebo LM, Stadlbauer V, Fuskevag O-M, Zwingmann C, et al. L-ornithine and phenylacetate synergistically produces sustained reduction in ammonia and brain water in cirrhotic rats. Hepatology. 2009;50(1):155–64.

36. Ytrebo LM, Kristiansen RG, Maehre H, Fuskevag O-M, Kalstad T, Revhaug A, et al. L-ornithine phenylacetate attenuates increased arterial and extracellular brain ammonia and prevents intrac-ranial hypertension in pigs with acute liver failure. Hepatology. 2009;50(1):165–74.

37. Oria M, Chatauret N, Chavarria L, Romero-Gimenez J, Palenzuela L, Pardo-Yules B, et al. Motor-evoked potentials in awake rats are a valid method of assessing hepatic encephalopathy and of studying its pathogenesis. Hepatology. 2010;52:2077–85.

38. Oria M, Romero-Giménez J, Arranz JA, Riudor E, Raguer N, Córdoba J. Ornithine phenylac-etate prevents disturbances of motor-evoked potentials induced by intestinal blood in rats with portacaval anastomosis. J Hepatol. 2012;56(1):109–14. Epub 2011 Aug 9.

39. Montoliu C, Piedra fi ta B, Serra MA, del Olmo JA, Urios A, Rodrigo JM, et al. IL-6 and IL-18 in blood may discriminate cirrhotic patients with and without minimal hepatic encephalopathy. J Clin Gastroenterol. 2009;43:272–9.


40. Montoliu C, Rodrigo R, Monfort P, Llansola M, Cauli O, Boix J, et al. Cyclic GMP pathways in hepatic encephalopathy. Neurological and therapeutic implications. Metab Brain Dis. 2010;25:39–48.

41. Shawcross DL, Shari fi Y, Canavan JB, Yeoman AD, Abeles RD, Taylor NJ, et al. Infection and systemic in fl ammation, not ammonia, are associated with grade 3/4 hepatic encephalopathy, but not mortality in cirrhosis. J Hepatol. 2010;54:640–9.

42. Li Q, Verma IM. NF-kappaB regulation in the immune system. Nat Rev Immunol. 2002;2:725–34.

43. Balasubramaniyan V, Wright G, Sharma V, Davies NA, Shari fi Y, Habtesion A, Mookerjee RP, Jalan R. Ammonia reduction with ornithine phenylacetate restores brain eNOS activity via the DDAH-ADMA pathway in bile duct-ligated cirrhotic rats. Am J Physiol Gastrointest Liver Physiol. 2012;302(1):G145–52.

44. Leiper J, Nandi M, Torondel B, Murray-Rust J, Malaki M, O’Hara B, et al. Disruption of methylarginine metabolism impairs vascular homeostasis. Nat Med. 2007;13:198–203.

45. Mookerjee RP, Malaki M, Davies NA, Hodges SJ, Dalton RN, Turner C, et al. Increasing dimethylarginine levels are associated with adverse clinical outcome in severe alcoholic hepatitis. Hepatology. 2007;45:62–71.

Part IV Special Topics


Keywords Sleep quality • Sleep timing • Sleepiness • Diurnal preference • Melatonin • Circadian rhythms

This chapter will focus on sleep disturbances and their pathophysiology in patients with cirrhosis. Sleep disturbances will be divided into night sleep disturbance , abnor-mal sleep timing and daytime sleepiness . The relationship between each of these key features of the sleep–wake pro fi le and hepatic encephalopathy, if any, will be dis-cussed. A separate section will cover the available information on the pathophysiology of sleep alterations in this patient population. Finally, treatment will be discussed.

Night Sleep Disturbance

Up to 50–65% of patients with cirrhosis complain of unsatisfactory sleep [ 1– 4 ] . More speci fi cally, they complain of increased sleep latency (dif fi culties falling asleep) and excessive sleep fragmentation (numerous night awakenings) [ 1, 3, 4 ] . Questionnaire-based sleep complaints are substantiated by quantitative sleep quality parameters, such as wrist actigraphy (i.e. the recording of movement over days/weeks by means of an accelerometer worn as a wrist watch), which documents activity over the whole 24 h and numerous sleep interruptions [ 1, 5, 6 ] .

Night sleep disturbance seems to be more common in patients with cirrhosis than in patients with other chronic illnesses, for instance, renal failure [ 1 ] , and is detectable also in well-compensated patients with cirrhosis [ 1, 4 ] , with no obvious reasons for

S. Montagnese, MD, PhD (*) Department of Medicine , University of Padova , Via Giustiniani, 2 , Padova 35128 , Italy e-mail: [email protected]

Chapter 14 Sleep Disorders and Hepatic Encephalopathy

Sara Montagnese

178 S. Montagnese

disturbed sleep such as severe itching, tense ascites or the need to empty their bladder repeatedly overnight because of treatment with diuretics.

While night sleep disturbance has been traditionally associated with hepatic encephalopathy, there are limited experimental animal data [ 7, 8 ] and virtually no human data to support this contention. Córdoba et al. found no difference in the prevalence of sleep disturbance in relation to psychometric performance in 44 patients with cirrhosis, 24 (55%) of whom had minimal hepatic encephalopathy [ 1 ] . In a study by Montagnese et al., which was designed to assess the relationship between sleep behaviour and neuropsychiatric performance, no association was observed between the presence of night sleep disturbance and either the presence or the severity of hepatic encephalopathy [ 4 ] . Finally, Spahr et al. showed that the histamine H

1 blocker hydroxyzine improves sleep quality in patients with cirrhosis

and minimal hepatic encephalopathy but not their cognitive performance [ 5 ] , thus dissociating the two sets of symptoms.

Delayed Sleep Timing

The fi rst study to assess sleep timing in patients with cirrhosis was that of Córdoba et al. [ 1 ] . In this study, sleep timing was assessed, in relation to sleep quality and diur-nal preference (eveningness/morningness), in a group of healthy volunteers, a group of patients with cirrhosis and a control diseased group of patients with renal failure [ 1 ] . An association was observed between delayed sleep habits/evening preference and impaired sleep quality in patients with cirrhosis, while no such association existed in the healthy and disease control groups. These fi ndings were con fi rmed by Montagnese et al., who described signi fi cant correlations between diurnal preference and sleep quality scores, with evening patients taking longer to fall asleep and sleep-ing worse [ 4 ] . The observed delays in sleep habits in a subgroup of patients with cir-rhosis (approximately 60 min compared to the healthy population) were shown to be independent of employment status in a smaller, subsequent study [ 6 ] .

The interest in sleep timing amongst chronobiologists and sleep scientists has grown considerably over the recent years. It has been shown that even in the healthy population, individuals who are more alert in the evening and have late/delayed sleep habits (“owls”) can experience dif fi culties in complying with the living and working constraints of the Western world, which requires them to be operative in the early part of the day [ 9 ] . These dif fi culties, which can translate into morning traf fi c accidents and poor school/work performances, become particularly prominent when evening subjects are forced to a sudden 60-min advance of their sleep–wake schedule, on the spring switch to “light saving time”. There is even some indication that the transition to light saving time might be associated with an increase in the incidence of myocardial infarction [ 10 ] . The 60-min delay relating to light saving time is comparable to the delay in sleep–wake habits exhibited by patients with cirrhosis compared to the healthy population, although the latter is chronic rather than suddenly and externally imposed. Nevertheless, the prognostic relevance of abnormal sleep timing in this patient population is worthy of further research.

17914 Sleep Disorders and Hepatic Encephalopathy

Daytime Sleepiness

So-called “inversion” of the sleep–wake pattern, manifest as an inability to rest at night and profound daytime somnolence, was fi rst recognised as a sign of overt hepatic encephalopathy by Sherlock et al. in a case series of 17 patients with varying degree of hepatic dysfunction, accompanied by severe neurological abnormalities [ 11 ] . This paper is often quoted as indicating that sleep–wake inversion and disturbed nocturnal sleep are both features of hepatic encephalopathy. However, the patient population was extremely heterogeneous, with several individuals having noncirrhotic acute hepatic failure, and the accompanying neurological alterations were very severe.

Nevertheless, excessive daytime sleepiness has been subsequently described in individuals with cirrhosis and milder neuropsychiatric impairment [ 1–4 ] . In at least in one study, an association was observed between excessive sleepiness and the presence/degree of hepatic encephalopathy. In the same paper, a correlation was described between a sleepiness scale and the degree of electroencephalographic slowing [ 4 ] . These observations fi t the hypothesis that hepatic encephalopathy can be interpreted, at least to some extent, as a syndrome of decreased vigilance [ 12 ] . Indeed, some of the electroencephalographic features of hepatic encephalopathy are reminiscent of those observed during the wake–sleep transition [ 13 ] .

In summary, night sleep disturbance, especially in the way of increased sleep latency and interrupted night sleep, is common in patients with cirrhosis, regardless of the presence of hepatic encephalopathy. In addition, a subset of these patients tend to have delayed sleep habits (bed and wake-up times delayed by approximately an hour compared to the healthy population), independently of their daytime commitments [ 1, 6 ] . These individuals also exhibit more pronounced night sleep disturbance. Excessive daytime sleepiness and daytime napping are also common in patients with cirrhosis and they are associated with the presence of hepatic encephalopathy [ 4 ] . There is little evidence, in the studies performed to date, of a relationship between night sleep disturbance and daytime sleepiness (patients who are sleepy in the daytime are not necessarily those who sleep badly at night), sug-gesting that their occurrence may re fl ect different disease processes. Finally, sleep–wake alterations have been shown to severely impinge on quality of life in this patient population [ 4, 14 ] . Nonetheless, they are not routinely screened for [ 15 ] and they tend to be managed in a nonspeci fi c, potentially inappropriate fashion.

Physiological Sleep Regulation

The currently accepted two-process model of human sleep regulation postulates the interaction between a circadian and a homeostatic mechanism [ 16 ] .

Circadian sleep regulation is responsible for the alternation of periods of high/low sleep propensity, in relation to dark/light cues, and irrespective of preceding sleep–wake behaviour. The suprachiasmatic nuclei of the hypothalamus are the site of the master circadian clock, which generates circadian rhythms. In humans,

180 S. Montagnese

the average, endogenous circadian period is approximately 24.18 h and must be constantly synchronised, or entrained, to the 24-h day by external in fl uences [ 17 ] . Light, which is the major external time cue, reaches the suprachiasmatic nuclei by afferent projections from the retina, primarily via the retino-hypothalamic tract. In turn, the suprachiasmatic nuclei project to the pineal gland, regulating the produc-tion of melatonin, which can be thought of as a neuroendocrine transducer of the light/dark cycle [ 18 ] . Thus, in healthy individuals, melatonin synthesis increases

Fig. 14.1 The black lines illustrate the normal, 24-h rhythm of plasma melatonin, which is virtually absent in the daytime, starts rising in the evening, peaks in the middle of the night, and then gradually declines. Part of the changes observed in the 24-h melatonin pro fi le of patients with cirrhosis, such as prolonged melatonin peaks and high daytime levels ( green line ( a )), can be ascribed to impaired hepatic melatonin metabolism, while others, such as an overall rhythm delay involving both the onset and the offset of the peak ( green line ( b )) suggest central circadian dysfunction

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b


soon after the onset of darkness, peaks in the middle of the night and then gradually declines (Fig. 14.1 ). The nocturnal rise in melatonin synthesis is associated with an increased propensity to sleep and is acutely suppressed by light exposure, as a result of a rapid decrease in pineal serotonin N -acetyltransferase activity [ 19 ] . Melatonin is hydroxylated and sulphated to 6-sulphatoxymelatonin (aMT6s), primarily in the liver, and aMT6s is subsequently excreted in the urine. Minor amounts of melatonin are excreted unchanged, conjugated with glucuronic acid or react with active oxy-gen species, leading to the formation of the pharmacologically active compounds of the kynurenines family [ 20 ] .

Homeostatic sleep regulation is responsible for the increase in sleep propensity when sleep is curtailed or absent and its dissipation during sleep. The term homeo-static refers to the fact that the system counteracts deviations from an average “reference level” of sleep. The pioneering studies of Blake and Gerard showed that both the arousal threshold and the dominance of slow electroencephalographic waves are high in the initial part of sleep and progressively decrease [ 21 ] . The initial dominance of slow-wave activity has been con fi rmed in subsequent studies [ 22 ] and it has also been shown that sleep deprivation produces an increase in slow-wave activity in the recovery night [ 23 ] . In contrast, a daytime nap attenuates slow-wave activity in the subsequent sleep episode [ 24 ] . Taken together, these fi ndings indicate that slow-wave activity reliably re fl ects prior history of sleep and wake. The exact neurochemical correlates of human sleep homeostasis remain unknown, but there is evidence that adenosinergic neurotransmission might play an important role [ 25 ] .

The separation of the circadian and homeostatic processes is useful for descrip-tive purposes. However, it is the fi ne-tuned interaction between these two processes that enables sleep consolidation, optimal waking performance and relatively brief sleep–wake and wake–sleep transitions [ 26 ] . It is common experience that, no matter how long the preceding wake period, it is still easier to sleep during the night, when it is dark, than during the day.

Sleep Regulation in Patients with Cirrhosis

It has been assumed, on fi rst principles, that, as melatonin is metabolised in the liver, its disposition would be delayed in patients with cirrhosis (Fig. 14.1a ). Abnormalities have been observed, including high daytime plasma melatonin con-centrations [ 27 ] , low urinary aMT6s concentrations [ 28 ] and a reduction in the clearance of exogenously administered melatonin [ 29 ] , which point to impaired hepatic metabolism. In a study where plasma melatonin and urinary aMT6s were assessed simultaneously over a 36-h period (two nights plus one day), 24-h mela-tonin clearance was shown to be comparable to that of healthy controls, while overnight melatonin clearance (thus clearance at a time when the hormone levels are highest) was reduced [ 30 ] . In the same and in other studies, correlations were observed between the delay in plasma melatonin/urinary aMT6s peaks and the degree of hepatic failure [ 6, 31, 32 ] .

182 S. Montagnese

However, other circadian abnormalities have also been described in patients with cirrhosis, namely, delays in the nocturnal rise of plasma melatonin and in its time to peak [ 27, 30, 33 ] , suggesting dysfunction of the central circadian clock rather than impaired melatonin disposition (Fig. 14.1b ). The function of the retinal-hypothalamic axis, and thus of the circadian clock, can be assessed by measuring “melatonin sup-pression” (i.e. the rapid decrease in melatonin plasma levels in response to the expo-sure of the retina to light at night [ 34 ] ) and/or by measuring the 24-h pro fi le of at least two variables out of melatonin, cortisol and core body temperature, the rhythm of each of which is strongly connected to the phase of the circadian clock. Montagnese et al. demonstrated parallel delays in the onset of plasma melatonin/plasma cortisol rhythms and attenuated melatonin sensitivity to light in a group of 20 patients with cirrhosis, thus suggesting that some degree of central circadian dysfunction exists in this patient population [ 30, 35 ] . Bernardi et al. [ 36 ] and Velissaris et al. [ 33 ] reported normal cortisol rhythms in patients with cirrhosis but in both studies the number of samples was smaller than required for accurate estimates of cortisol rhythm timing and controls were not exercised for light exposure, which might have biased the results. Interestingly, in the study by Montagnese et al., melatonin sensitivity to night light (melatonin suppression) was inversely correlated with the timing of the mela-tonin peak [ 30 ] , supporting Steindl’s original hypothesis that the observed delays in the 24-h melatonin pro fi le depend on a dysfunctional retinal-hypothalamic axis [ 27 ] . Similar circadian abnormalities have been reported in blind individuals; however, these show considerably more variation in their melatonin and cortisol pro fi les, with advanced, delayed and free-running rhythms all being described [ 37 ] .

Some attempt has been made to correlate the changes in the melatonin rhythm with the sleep disturbances observed in patients with cirrhosis, but the fi ndings have been inconclusive [ 27, 30, 38 ] . Montagnese et al. have suggested that circadian rhythm delays in this patient population are associated with delayed sleep habits, although not necessarily with impaired sleep quality. The combination of evening preference, delayed sleep habits, impaired sleep quality and delayed circadian rhythms is reminiscent of “delayed sleep phase syndrome” [ 39 ] , a circadian disorder characterised by considerable delays in sleep onset and wake times. The goal of treatment is to resynchronise the circadian clock with the 24-h light/dark cycle: structured sleep–wake schedules and avoidance of exposure to bright light in the evening are advised. In addition, exposure to bright light shortly after awakening in the morning [ 40 ] and/or administration of melatonin 5–6 h before habitual sleep time [ 41 ] have been shown to advance the timing of sleep. In patients with cirrhosis, naturally occurring delayed sleep phase syndrome might be exacerbated by delayed hepatic melatonin metabolism, increasing its prevalence and modulating its clinical features [ 6, 42 ] .

Virtually no information is available on the effect of hepatic transplantation on circadian abnormalities in patients with cirrhosis, but one encouraging case report suggests that transplantation can revert melatonin arrhythmia [ 43 ] .

Limited information is available on homeostatic sleep regulation in patients with cirrhosis. Polysomnography has been performed in a limited number of studies but with the aim of evaluating indices of hepatic encephalopathy rather than homeostatic


indices per se. Correlations were established between the clinical severity of encephalopathy and ammonia levels on one hand and the degree of disruption of sleep architecture on the other [ 44 ] . No matter how profound, the disturbances in sleep architecture remained reversible, in parallel with lowered ammonia levels and improved neuropsychiatric performance [ 44 ] .

Decreased density of the adenosine receptor A1AR has also been described in both cortical and subcortical regions of the brain of patients with cirrhosis in one positron emission tomography/magnetic resonance imaging study [ 45 ] , thus poten-tially implicating the homeostatic system in sleep deregulation in these patients; however, sleep–wake pro fi les were not obtained in this study.

In summary, the pathophysiology of sleep–wake disturbance in patients with cirrhosis remains poorly understood. Circadian regulation has been studied in some depth, while less is known about homeostatic regulation. In addition, virtually no information is available on: (a) genetic predisposition, (b) sympathetic/parasympa-thetic transmission of the circadian clock signal to the periphery, and (c) function/dysfunction of the hepatic clocks, which may all play a role (Fig. 14.2 ).

Treatment of Sleep–Wake Abnormalities in Patients with Cirrhosis

Limited therapeutic options are available to treat sleep–wake disturbances in patients with cirrhosis. This is for a number of reasons : (a) sleep–wake alterations are not formally assessed in routine hepatological practice, (b) their pathogenesis has not

Fig. 14.2 Diagram summarising the potential pathophysiological mechanisms of sleep–wake alterations in patients with cirrhosis. Continuous arrows mark associations or causal relationships that are supported by the studies performed to date; dashed arrows mark hypothetical associations/causal relationships. HE hepatic encephalopathy; aMT6s 6-sulphatoxymelatonin

184 S. Montagnese

been fully elucidated, (c) patients with cirrhosis are extremely sensitive to psychoac-tive drugs [ 46 ] , and (d) hepatic impaired disposition of common hypnotics can result in accumulation and oversedation [ 47 ] . Even when an “aetiological” treatment was attempted by Spahr et al., who administered the histamine H1 blocker hydroxyzine to a group of patients with minimal encephalopathy and sleep alterations, some risk of precipitating severe hepatic encephalopathy was observed [ 5 ] . All these issues result in underdiagnosis and cautious, aspeci fi c and potentially inappropriate man-agement strategies. Further elucidation of the pathophysiological mechanisms may, in time, lead to the development of speci fi c therapies. Meanwhile:

1. Routine assessment of night sleep quality, sleep–wake timing habits and diurnal somnolence should be performed.

2. Sleep and light hygiene practices, to include regular sleep–wake schedules, exposure to bright, natural light in the early hours of the morning and avoidance of exposure to bright light in the evening should be encouraged.

References

1. Córdoba J, Cabrera J, Lataif L, Penev P, Zee P, Blei AT. High prevalence of sleep disturbance in cirrhosis. Hepatology. 1998;27:339–45.

2. Bianchi G, Marchesini G, Nicolino F, et al. Psychological status and depression in patients with liver cirrhosis. Dig Liver Dis. 2005;37:593–600.

3. Mostacci B, Ferlisi M, Baldi AA, et al. Sleep disturbance and daytime sleepiness in patients with cirrhosis: a case control study. Neurol Sci. 2008;29:237–40.

4. Montagnese S, Middleton B, Skene DJ, Morgan MY. Night-time sleep disturbance does not correlate with neuropsychiatric impairment in patients with cirrhosis. Liver Int. 2009;29:1372–82.

5. Spahr L, Coeytaux A, Giostra E, Hadengue A, Annoni JM. Histamine H1 blocker hydroxyzine improves sleep in patients with cirrhosis and minimal hepatic encephalopathy: a randomized controlled pilot trial. Am J Gastroenterol. 2007;102:744–53.

6. Montagnese S, Middleton B, Mani AR, Skene DJ, Morgan MY. Sleep and circadian abnor-malities in patients with cirrhosis: features of delayed sleep phase syndrome? Metab Brain Dis. 2009;24:427–39.

7. Córdoba J, Dupuis J, Gottstein J, Blei AT. Stenosis of a portacaval anastomosis affects circadian locomotor activity in the rat: a multivariable analysis. Am J Physiol. 1997;273:G1218–25.

8. Ahabrach H, Piedra fi ta B, Ayad A, et al. Chronic hyperammonemia alters the circadian rhythms of corticosteroid hormone levels and of motor activity in rats. J Neurosci Res. 2010;88:1605–14.

9. Kantermann T, Juda M, Merrow M, Roenneberg T. The human circadian clock’s seasonal adjustment is disrupted by daylight saving time. Curr Biol. 2007;17:1996–2000.

10. Janszky I, Ljung R. Shifts to and from daylight saving time and incidence of myocardial infarction. N Engl J Med. 2008;359:1966–8.

11. Sherlock S, Summerskill WH, White LP, Phear EA. Portal-systemic encephalopathy; neuro-logical complications of liver disease. Lancet. 1954;267:454–7.

12. Ross CA. CNS arousal systems: possible role in delirium. Int Psychogeriatr. 1991;3:353–71. 13. Montagnese S, Jackson C, Morgan MY. Spatio-temporal decomposition of the electroencepha-

logram in patients with cirrhosis. J Hepatol. 2007;46:447–58. 14. Marchesini G, Bianchi G, Amodio P, et al. Factors associated with poor health-related quality

of life of patients with cirrhosis. Gastroenterology. 2001;120:170–8.


15. Montagnese S, Middleton B, Skene DJ, Morgan MY. Sleep-wake patterns in patients with cirrhosis: all you need to know on a single sheet. A simple sleep questionnaire for clinical use. J Hepatol. 2009;51:690–5.

16. Borbely AA. A two process model of sleep regulation. Hum Neurobiol. 1982;1:195–204. 17. Czeisler CA, Duffy JF, Shanahan TL, et al. Stability, precision, and near-24-hour period of the

human circadian pacemaker. Science. 1999;284:2177–81. 18. Moore RY. Neural control of the pineal gland. Behav Brain Res. 1996;73:125–30. 19. Arendt J. Light-dark control of melatonin synthesis. Melatonin and the mammalian pineal

gland. 1st ed. London: Chapman & Hall; 1995. p. 66–109. 20. Boutin JA, Audinot V, Ferry G, Delagrange P. Molecular tools to study melatonin pathways

and actions. Trends Pharmacol Sci. 2005;26:412–9. 21. Blake H, Gerard RW. Brain potentials during sleep. Am J Physiol. 1937;119:692–703. 22. Dement W, Kleitman N. Cyclic variations in EEG during sleep and their relation to

eye movements, body motility, and dreaming. Electroencephalogr Clin Neurophysiol. 1957;9:673–90.

23. Borbely AA, Baumann F, Brandeis D, Strauch I, Lehmann D. Sleep deprivation: effect on sleep stages and EEG power density in man. Electroencephalogr Clin Neurophysiol. 1981;51:483–95.

24. Werth E, Dijk DJ, Achermann P, Borbely AA. Dynamics of the sleep EEG after an early evening nap: experimental data and simulations. Am J Physiol. 1996;271:R501–10.

25. Landolt HP. Sleep homeostasis: a role for adenosine in humans? Biochem Pharmacol. 2008;75:2070–9.

26. Dijk DJ, Czeisler CA. Paradoxical timing of the circadian rhythm of sleep propensity serves to consolidate sleep and wakefulness in humans. Neurosci Lett. 1994;166:63–8.

27. Steindl PE, Finn B, Bendok B, Rothke S, Zee PC, Blei AT. Disruption of the diurnal rhythm of plasma melatonin in cirrhosis. Ann Intern Med. 1995;123:274–7.

28. Steindl PE, Ferenci P, Marktl W. Impaired hepatic catabolism of melatonin in cirrhosis. Ann Intern Med. 1997;127:494.

29. Iguchi H, Kato KI, Ibayashi H. Melatonin serum levels and metabolic clearance rate in patients with liver cirrhosis. J Clin Endocrinol Metab. 1982;54:1025–7.

30. Montagnese S, Middleton B, Mani AR, Skene DJ, Morgan MY. On the origin and the conse-quences of circadian abnormalities in patients with cirrhosis. Am J Gastroenterol. 2010;105:1773–81.

31. Piscaglia F, Hermida RC, Siringo S, Legnani C, Ramadori G, Bolondi L. Cirrhosis does not shift the circadian phase of plasma fi brinolysis. Am J Gastroenterol. 2002;97:1512–7.

32. Velissaris D, Karamouzos V, Polychronopoulos P, Karanikolas M. Chronotypology and mela-tonin alterations in minimal hepatic encephalopathy. J Circadian Rhythms. 2009;7:6.

33. Velissaris D, Karanikolas M, Kalogeropoulos A, et al. Pituitary hormone circadian rhythm alterations in cirrhosis patients with subclinical hepatic encephalopathy. World J Gastroenterol. 2008;14:4190–5.

34. Thapan K, Arendt J, Skene DJ. An action spectrum for melatonin suppression: evidence for a novel non-rod, non-cone photoreceptor system in humans. J Physiol. 2001;535:261–7.

35. Montagnese S, Middleton B, Mani AR, Skene DJ, Morgan MY. Changes in the 24-h plasma cortisol rhythm in patients with cirrhosis. J Hepatol. 2011;54(3):588–90.

36. Bernardi M, De Palma R, Trevisani F, et al. Chronobiological study of factors affecting plasma aldosterone concentration in cirrhosis. Gastroenterology. 1986;91:683–91.

37. Lockley SW, Skene DJ, Tabandeh H, Bird AC, Defrance R, Arendt J. Relationship between napping and melatonin in the blind. J Biol Rhythms. 1997;12:16–25.

38. Steindl PE, Finn B, Bendok B, Rothke S, Zee PC, Blei AT. [Changes in the 24-hour rhythm of plasma melatonin in patients with liver cirrhosis—relation to sleep architecture]. Wien Klin Wochenschr. 1997;109:741–6.

39. Weitzman ED, Czeisler CA, Coleman RM, et al. Delayed sleep phase syndrome. A chronobio-logical disorder with sleep-onset insomnia. Arch Gen Psychiatry. 1981;38:737–46.

186 S. Montagnese

40. Weyerbrock A, Timmer J, Hohagen F, Berger M, Bauer J. Effects of light and chronotherapy on human circadian rhythms in delayed sleep phase syndrome: cytokines, cortisol, growth hormone, and the sleep-wake cycle. Biol Psychiatry. 1996;40:794–7.

41. Nagtegaal JE, Kerkhof GA, Smits MG, Swart AC, Van Der Meer YG. Delayed sleep phase syndrome: a placebo-controlled cross-over study on the effects of melatonin administered fi ve hours before the individual dim light melatonin onset. J Sleep Res. 1998;7:135–43.

42. Blei AT, Zee P. Abnormalities of circadian rhythmicity in liver disease. J Hepatol. 1998;29:832–5.

43. Cordoba J, Steindl P, Blei AT. Melatonin arrhythmia is corrected after liver transplantation. Am J Gastroenterol. 2009;104:1862–3.

44. Kurtz D, Zenglein JP, Imler M, et al. [Night sleep in porto-caval encephalopathy]. Electroencephalogr Clin Neurophysiol. 1972;33:167–78.

45. Boy C, Meyer PT, Kircheis G, et al. Cerebral A1 adenosine receptors (A1AR) in liver cirrhosis. Eur J Nucl Med Mol Imaging. 2008;35:589–97.

46. Laidlaw J, Read AE, Sherlock S. Morphine tolerance in hepatic cirrhosis. Gastroenterology. 1961;40:389–96.

47. Assy N, Rosser BG, Grahame GR, Minuk GY. Risk of sedation for upper GI endoscopy exacerbating subclinical hepatic encephalopathy in patients with cirrhosis. Gastrointest Endosc. 1999;49:690–4.


Keywords Driving • Minimal hepatic encephalopathy • Simulation • Legal • Motor vehicle • Crashes • Traf fi c violations

Introduction

Hepatic encephalopathy is characterized as a spectrum of neuropsychiatric symp-toms in the absence of other known brain disease [ 1 ] . Hepatic encephalopathy ranges from overt and severe disturbances to minimal hepatic encephalopathy (MHE), once described as “low-grade” or “subclinical” encephalopathy. These patients lack the neurologic exam fi ndings and historical symptoms for diagnosis, and instead manifest with subtle neuro-cognitive de fi cits and psychomotor abnor-malities, primarily affecting immediate memory, attention, visual spatial abilities, and fi ne motor skills [ 2 ] . As MHE is estimated to have a prevalence of 22–80% [ 3– 7 ] , this becomes particularly important when pertaining to the responsibility of driving an automobile or commercial vehicle.

M. R. Kappus, MD Department of Internal Medicine , Virginia Commonwealth University Health Systems and Physicians , 1250 East Marshall Street , PO Box 980509 , Richmond , VA 23298-0509 , USA

J. S. Bajaj, MBBS, MD, MS (*) Department of Gastroenterology, Hepatology and Nutrition , Virginia Commonwealth University and McGuire VA Medical Center , 1201 Broad Rock Boulevard , Richmond , VA 23249 , USA e-mail: [email protected]

Chapter15 Hepatic Encephalopathy and Driving

Matthew R. Kappus and Jasmohan S. Bajaj

188 M.R. Kappus and J.S. Bajaj

Driving and Society

Driving is a dangerous activity, and has a signi fi cant impact on our society with over 34,000 fatalities and 2,120,000 injuries in the United States in 2008 alone [ 8 ] . Individual characteristics of the driver predominate in the causation of most motor vehicle crashes, and certain underlying conditions predispose drivers to their occur-rence [ 8 ] . It is expected for states, through the department of motor vehicles or transportation safety, to detect, examine, and regulate problem drivers. These drivers include those inexperienced, the elderly, the intoxicated, or those with episodic loss of consciousness (i.e., epilepsy). Restrictions are imposed upon the new driver to protect both society and the driver. More frequent written and performance exami-nations are required to detect impairment in the elderly. Awareness of this link between medical conditions like diabetes, dementia, cardiac disease, stroke, and epilepsy and car accidents [ 9 ] brings forward the importance of how to assess medical fi tness to drive [ 10 ] . As the population ages, the prevalence of medical conditions known to impair driving, like stroke, obstructive sleep apnea, dementia, polyphar-macy, will increase. Frighteningly, most medical conditions are not even considered by the state licensing agencies, and legislation to restrict the impaired driver is slow. Among those conditions which leave patients with a questionable ability to drive is MHE. More evidence is beginning to emerge on the adverse effects of MHE on daily functioning and guidelines do not currently exist for evaluating capacity to operate a motor vehicle.

Skills Needed to Drive

Skills expected for safely driving a vehicle includes physical mobility and psychomo-tor coordination, visual and audio perception, and higher cognitive ability and attention span. Decisions are made on a tactical, strategic, and operational level [ 11 ] . The act of driving requires a person to incorporate different senses, coordinating different actions such as speeding up, slowing down, passing, and turning. Visual perception allows the person to see obstacles, and audio perception helps drivers detect warning signals such as car horns and the sound of other vehicles on the road. Drivers are required to main-tain attention to the road, and minimize other distractions such as other passengers or the surrounding environment. Cognitive ability allows the driver to make decisions and determine reaction time, navigate an environment, and executive decision making in order to determine traveling speeds, and follow local driving laws.

Why Should MHE Affect Driving

MHE encompasses neuro-cognitive impairment [ 10 ] . Studies done with Alzheimer patients have shown that impairment of attention and speed of mental processing—both exhibited in patients with MHE—affect an individual’s ability to react to

18915 Hepatic Encephalopathy and Driving

unexpected traf fi c conditions [ 12 ] . MHE is characterized by defects in visuo-spatial assessment, attention span, working memory, and speed of information processing and motor abilities [ 13 ] . Diminished driving ability in these patients has been demonstrated [ 14 ] . This pattern of disease suggests involvement of the subcortical brain centers [ 15 ] . It is present in up to 80% of cirrhotics, and psychometric testing has indicated that between 15 and 75% of patients with MHE were unable to safely drive a motor vehicle [ 16, 17 ] .

The presence of MHE alone does not necessarily predict inability to drive a car [ 17 ] . Cognitive examinations have demonstrated depressed cognition, however, not necessarily inability to drive a car [ 17 ] . Cognitive exams such as the FEV 5 (German guidelines for driver quali fi cation and evaluation) and the BGL (German guidelines for expertise on driver aptitude) have been used to evaluate the neuropsychological fi tness for patients with MHE to drive. The results of both of these computerized tests and a real driving test with a driving instructor assessment showed progres-sively poor test results paralleled increased severity of hepatic encephalopathy. Interestingly, however, according to the judgment of the driving instructor, 39 and 48% of overt and minimal HE patients, respectively, could still drive a car. The driv-ing instructors only went so far as to deem overt and MHE “doubtful” and “un fi t” to drive in 61 and 52%, respectively, of the time [ 17 ] . This demonstrates that while these patients are cognitively impaired, there may be still some debate as to who still can safely drive.

Evidence of Driving Impairment

On-Road Driving Studies

Two early studies performed in the 1980s by Schomerus et al. [ 16 ] and Watanabe et al. [ 18 ] categorized a large fraction of patients with cirrhosis un fi t to drive as judged by on-road testing (44–60%). Around the same time, Srivastava et al. [ 19 ] in a pilot study evaluated driving on a live road test in 15 cirrhotic patients, nine of which had MHE, and they failed to detect impaired performance while driving a car. These con fl icting studies renewed interest in the fi eld and indicated that larger stud-ies would lead to further investigation of driving fi tness in cirrhotic patients (Table 15.1 ).

A 2004 study conducted by Wein et al. [ 20 ] evaluated 48 cirrhotics, 14 with MHE, using a standardized 90 min real-life road test. The evaluation by a profes-sional driving instructor, unaware of the diagnoses or reason for the test, showed that driving competence was scored lower in patients with MHE. Ratings in patients with cirrhosis without MHE were scored as being similar to the control group. This study suggested that MHE should be considered a medical condition that increases the risk of automobile accidents. The con fl icts of the Wein [ 20 ] study with earlier


studies [ 19 ] may be attributed to the larger sample size used in the Wein study, a study group with a more advanced stage of disease, or a more demanding on-road driving test. There were several variables unaccounted for in all studies, and further testing was needed.

Simulation Studies

While on-road tests are largely standardized, they do not ensure similar conditions and also have medico-legal implications. In contrast, driving simulation can be used to test the detailed cognitive response in MHE. A study of navigation and driving in cirrhotic patients with MHE was performed on a driving simulator [ 21 ] . This study showed that while impairment of attention, response inhibition, and visuo-motor coordination exists in MHE [ 22– 26 ] , working memory problems for navigational purposes also exists [ 27 ] . Working memory is a key component of completing an executive task by allowing an individual to rapidly adapt to new situations by recall-ing previous experience [ 21 ] . Patients underwent testing with three psychometric tests, and driving skills were assessed by using a driving simulation program. There was a signi fi cantly higher rate of collisions in the MHE group compared to all other groups. All patients incurred accidents when asked to overtake a slow moving vehi-cle by crossing into the lane of oncoming traf fi c, or when a simulation dog darted out into the driving fi eld. This shows a miscalculation of time needed to overtake the other vehicle, and a failure to react to a stimulus, respectively. In this study, patients with MHE also had more dif fi culty following mapped directions, and incurred a

Table 15.1 Available studies and results of minimal hepatic encephalopathy and driving

Study and location Total no./% with MHE MHE diagnosis Testing

Results in MHE patients

Schomerus et al. [ 16 ] ; Germany

40/25% EEG Driving test 100% Unsafe

Watanabe et al. [ 18 ] ; Japan

16/100% Reaction time Driving test 44% Unsafe

Srivastava et al. [ 19 ] ; Chicago

15/60% Psychometric tests

Driving test Similar to controls

Wein et al. [ 20 ] ; Germany


Driving test X10 intervention Behavior

rating Worse rating Worse driving

Kircheis et al. [ 56 ] ; Germany


Driving test Simulated or driving test required

Driving instructor Self-evaluation Biochemical analysis


higher number of incorrect turns compared to the other drivers. The study went on to further correlate a signi fi cant relationship between the number of positive psychometric tests with number of incorrect turns, though this same correlation was not statistically signi fi cant when it came to number of collisions [ 21 ] . By computer simulation there are demonstrated dif fi culties with attention and response inhibi-tion, skills required for safe navigation in patients with MHE.

Real-Life Driving Outcomes

The self-reported traf fi c violations and motor vehicle accidents in a cohort of cir-rhotic patients have been performed [ 28 ] . The results indicated that patients with cirrhosis reported more events than controls, and that patients with concomitant diagnoses of MHE had the highest rate of events compared to cirrhotics without MHE, or even those patients on psychoactive drugs. This was an important fi nding, as this is one of the fi rst studies to document objectively higher rates of motor vehicle accidents and traf fi c violations in patients with MHE. However, the self-reported nature as well as the retrospective design introduced bias. Another confounding feature of this study is the potential of the effect of etiology of liver disease, such as hepatitis C on the neurophysiologic and neuropsychological fea-tures used to establish a diagnosis of MHE [ 29 ] . Likewise, the effects of prolonged alcohol abuse leading to cirrhosis may have prolonged and subtle neurophysiologic abnormalities, therefore independently impacting driving outcome.

Therefore, the authors undertook a prospective validation in which they found that patients with MHE diagnosed by the ICT were at signi fi cantly higher risk for future driving offenses [ 14 ] . They also reported that MHE patients had a higher risk of traf fi c violations and motor vehicle crashes over the past year with self-report as well as through of fi cial driving records. Self-report of driving offenses was compa-rable to the of fi cial driving records [ 14 ] .

The current evaluation shows that MHE patients are likely to have driving dif fi culties on the road and on a simulator. These fi ndings actually translate into worse driving outcomes.

Additional Challenges Faced by MHE Patients While Driving

In addition to the neuropsychological de fi cits patients with MHE contend with, they also have a chronic debilitating illness which puts them at risk for increased fatigue. Of the factors that contribute to human error leading to motor vehicle accidents, a major one is fatigue [ 30 ] . Fatigue is associated with driving dif fi culties in healthy individuals and in patients with attention de fi cits. This is demonstrated


both in a simulator and during live driving scenarios [ 31– 33 ] . An age-matched control study was conducted observing the affect of fatigue on driving in patients with recent overt hepatic encephalopathy (OHE), MHE, and a control group [ 34 ] . The study compared driving skills in the fi rst half and second half of an extended driving period, and it was felt that patients with MHE had a signi fi cant worsening of simulated driving skill with time related to fatigue. Interestingly, patients with MHE were the only group to show a signi fi cant increase in the number of collisions in the second half compared with the fi rst when compared to controls and OHE. Patients with OHE did not show signi fi cant difference as they were already impaired at baseline. In the second half of the driving simulation, MHE patients had worsen-ing in their rate of collisions, off road excursions, and their speeding. A survey at the end of the simulation period asking drivers “after driving I feel tired,” MHE and OHE patients showed no difference in how many answered yes; however, there was a signi fi cantly increased number when compared to the control group. Patients with MHE have several dimensions of impairment in their driving abili-ties, and this study highlighted that fatigue [ 34 ] is one, in addition to reduced reaction time and navigational ability [ 20, 21 ] . Decreased driving ability due to fatigue from processing multiple sensory inputs during driving is important to con-sider in patients with MHE, especially because they lack the chronic feeling of fatigue that patients with OHE experience. Fatigue is one way that patients with MHE may be able to self-realize their inability to operate a motor vehicle; however, this is not present at the beginning of the driving task, but rather manifests later in the driving experience.

Besides fatigue, patients with MHE also lack insight into their own impair-ment, and insight into a problematic process is the fi rst step towards seeking inter-vention. In 2008, Bajaj et al. [ 35 ] used a 26-item scale named the driving behavioral survey (DBS), validated by Barkley et al. [ 36 ] in patients with attention de fi cit hyperactivity disorder (ADHD), to test the hypothesis of whether patients with MHE did in fact have insight into their driving disability. This scale was used because patients with MHE and ADHD struggle with attention impairment [ 21 ] . The study outcomes demonstrated that patients with MHE rated themselves equivalent to controls and cirrhotic patients without MHE despite having signi fi cantly worse driving performance on simulation driving. Also, the study enlisted observers who rated patient’s driving abilities, and observers rated MHE patients as poorer drivers compared with those patients without MHE or controls. MHE is dif fi cult to evaluate in the clinical setting, and evaluation of self-aware-ness in this group is challenging [ 37– 40 ] . If patients lack insight into their clinical disease, it will be up to healthcare providers to inquire about driving records to perhaps make patients more aware of their problem. This is important not only because motor vehicle accidents are a leading cause of death in the United States [ 41 ] , but also because of the negative impact of cirrhosis on survival after trauma and traf fi c accidents [ 41– 44 ] .


Determining Fitness to Drive in Minimal Hepatic Encephalopathy

Treatment of MHE Pertaining to Driving

Patients with MHE may not be safe to drive in certain cases; however, therapy, either medically or behaviorally, can improve driver ability. Therapy with gut-speci fi c agents like lactulose and rifaximin has been relied upon to clear cognition in patients with OHE, and may be useful in patients with MHE [ 17, 45– 48 ] . Bajaj et al. [ 49 ] randomly assigned in a double-blinded manner patients with known MHE to placebo or rifaximin and demonstrated improved ability by driving simulation. They also measured cognition with a set of cognitive battery tests, the NCT-A, NCT-B, the DST, and the ICT. A greater proportion of those given the rifaximin interven-tion improved driving outcomes (decreased collisions, illegal turns, and speeding tickets), as well as improvement towards normal in the NCT-B, DST, BDT, and the ICT cognitive tests. Interestingly, there was no signi fi cant difference between the two groups with respect to the number of collisions. This may re fl ect that those patients randomized to rifaximin may have been able to grasp insight into their poor driving based upon collisions, and perhaps this re fl ected improved working mem-ory, response inhibition, and cognitive fl exibility. This would suggest that therapy improved the cortical network feedback between frontal, insular, and the parietal regions [ 49 ] .

Still unknown is whether cognitive rehabilitation could have a bene fi t in patients with MHE as it has been shown to have in stroke and brain injury patients. Limited research has been done with brain injury patients with respect to speci fi c cognitive and behavioral aspects of motor vehicle operation. The design of these studies has been to test whether training exercises involving visuo-motor tracking, divided attention, performance feedback, and social reinforcement can improve the safety of driving in this patient population. Results have indicated that training resulted in improved performance during live driving simulation, and there may be a signi fi cant therapeutic effect in using speci fi c training exercises in patients with stroke and brain injury [ 50 ] . These same training techniques have not yet been understood in patients with MHE, and this will be an area of signi fi cant research in the future.

Legal Rami fi cations

Currently, only 76% of states in the United States have a medical advisory board overseeing driver regulation [ 51 ] . None of the 50 states even mentions oversight of patients with altered mental status as a result of liver-related disease, which would include both overt and MHE [ 51 ] . Only a subset, 12%, of states has a mandated


system in which physicians are required to report medically impaired patients, and in those states reporting was suboptimal due to burden to the physician [ 51 ] . Only 32 states provide legal immunity to physicians for reporting these unsafe drivers, and transcending the legal rami fi cations, physicians face the ethical decision of pro-tecting an individual’s right to privacy vs. the right of safety for society. For violat-ing either of these, a physician may be legally liable.

As there is no written law de fi nitive to this topic, and the present laws are subject to interpretation of the legal system. The American Medical Association (AMA) has released a guide to physicians assessing and counseling elderly drivers [ 52 ] . While this document does not address patients with MHE or OHE speci fi cally, it does provide a set of tools which may be useful for physicians. The overwhelming recommendation is for the physician and patient, with family, to have a candid dis-cussion, and that if there is a strong threat to public safety, it is both “desirable and ethical” to notify the authorities. It is in this way that the burden still rests with the states in making the fi nal determination of driving safety.

Because physicians are not speci fi cally trained in fi tness to drive evaluations, they must act in the best interest of the patient and society while following the local laws [ 53 ] . Physicians are advised to follow the applicable local laws on mandatory reporting; inform the patient and their family of the potential impairment; and if possible, recommend a fi tness to drive evaluation by a driving instructor trained in detecting impairment. Physicians can also educate the public and legislatures to advocate for changes in driving-related legislation.

As of now, this is still a burdensome task as the present tools used to diagnose MHE are not easily used in a clinical setting. It is hopeful that in the future, a more simple and direct way of being able to identify these patients will be available. Until then, it will be the duty of the physician to report patients at risk to the proper gov-ernmental agency for further driving evaluation.

Summary

OHE is usually clinically evident and obviates driving, but the challenge arises once acute episodes have resolved, or patients present with MHE. It is evident that HE consists of spectrum of neuro-cognitive de fi cits. The most mild of these de fi cits consists of cognitive and attention de fi cits and are compounded by impaired response inhibition, working memory, and visuo-motor coordination [ 54, 55 ] , all of which are important skills for driving a vehicle. These patients lack insight into their prob-lem, and more easily develop fatigue, which contributes to the danger [ 21, 49, 56 ] . Diagnosis of MHE requires specialized testing and is often dif fi cult to detect, and physician reporting to state driver regulatory organizations is riddled with ethical and legal dilemmas. The effect of hepatic encephalopathy on driving is complex and affects patients and the general population alike. These effects and exciting new treatment strategies are being actively investigated.


References

1. Bajaj JS, Wade JB, Sanyal AL. Spectrum of neurocognitive impairment in cirrhosis: implica-tions for the assessment of hepatic encephalopathy. Hepatology. 2009;50:2014–21.

2. Randolph C, Hilsabeck R, Kato A, et al. Neuropsychological assessment of hepatic encephal-opathy: ISHEN practice guidelines. Liver Int. 2009;29:629–35.

3. Dhiman RK, Saraswat VA, Sharma BK, et al. Indian National Association for Study of the Liver: minimal hepatic encephalopathy: consensus statement of a working party of the Indian National Association for Study of the Liver. J Gastroenterol Hepatol. 2010;25:1029–41.

4. Sharma P. Minimal hepatic encephalopathy. J Assoc Physicians India. 2009;57:760–3. 5. Dhiman RK, Chawla YK. Minimal hepatic encephalopathy. Indian J Gastroenterol.

2009;28:5–16. 6. Sharma P, Sharma BC. Predictors of minimal hepatic encephalopathy in patients with cirrho-

sis. Saudi J Gastroenterol. 2010;16:181–7. 7. Bajaj JS. Minimal hepatic encephalopathy matters in daily life. World J Gastroenterol.

2008;14:3609–15. 8. Traf fi c safety facts 2008: a compilation of motor vehicle crash data from the fatality analysis

reporting system and the general estimates system—NHTSA DOT HS 811 170. http://www-nrd.nhtsa.dot.gov/CATS/index/aspx . Accessed 26 Feb 2011.

9. O’Neill D. Physicians, elderly drivers, and dementia. Lancet. 1992;339:41–3. 10. Marotolli RA, Cooney LM, Wagner S, Doucette J, Tinetti ME. Predictors of automobile

crashes and moving violations among elderly drivers. Ann Intern Med. 1994;121:842–6. 11. Marshall SC. The role of reduced fi tness to drive due to medical impairments in explaining

crashes involving older drivers. Traf fi c Inj Prev. 2008;9:291–8. 12. Rizzo M, McGehee DV, Dawson JD, Anderson SN. Simulated car crashes at intersections in

drivers with Alzheimer disease. Alzheimer Dis Assoc Disord. 2001;15:10–20. 13. Quero JC, Schalm SW. Subclinical hepatic encephalopathy. Semin Liver Dis. 1996;16: 321–8. 14. Bajaj JS. Minimal hepatic encephalopathy is associated with motor vehicle crashes: the reality

beyond the driving test. Hepatology. 2009;50(4):1175–83. 15. McCrea M, Cordoba J, Vessey G, Blei AT, Randolph C. Neuropsychological characterization

and detection of subclinical hepatic encephalopathy. Arch Neurol. 1996;53:758–63. 16. Schomerus H, Hamster W, Blunck H, et al. Latent portosystemic encephalopathy. Nature of

cerebral function defects and their effect on fi tness to drive. Dig Dis Sci. 1981;16:321–8. 17. Haussinger D, Schliess F. Pathogenetic mechanisms of hepatic encephalopathy. Gut.

2008;57:1156–65. 18. Watanabe A, Tuchida T, Yata Y, et al. Evaluation of neuropsychological function in patients with

liver cirrhosis with special reference to their driving ability. Metab Brain Dis. 1995;10:239–48. 19. Srivastava A, Mehta R, Rothke SP, Rademaker AW, Blei AT. Fitness to drive in patients with

cirrhosis and portal-systemic shunting: a pilot study evaluating driving performance. J Hepatol. 1994;21:1023–8.

20. Wein C, Koch H, Popp B, et al. Minimal hepatic encephalopathy impairs fi tness to drive. Hepatology. 2004;39:739–45.

21. Bajaj JS, Hafeezullah M, Hoffmann R. Navigation skill impairment: another dimension of the driving dif fi culties in minimal hepatic encephalopathy. Hepatology. 2008;47(2):596–604.

22. Amodio P, Schiff S, Del Piccolo F, Mapelli D, Gatta A, Umilta C. Attention dysfunction in cirrhotic patients: an inquiry on the role of executive control, attention orienting and focusing. Metab Brain Dis. 2005;20:115–27.

23. Weissenborn K, Ennen JC, Schomerus H, Ruckert N, Hecker H. Neuropsychological charac-terization of hepatic encephalopathy. J Hepatol. 2001;34:768–73.


25. Weissenborn K, Giewekemeyer K, Heidenreich S, Bokemeyer M, Berding G, Ahl B. Attention, memory, and cognitive function in hepatic encephalopathy. Metab Brain Dis. 2005;20:359–67.

http://www-nrd.nhtsa.dot.gov/CATS/index/aspx

http://www-nrd.nhtsa.dot.gov/CATS/index/aspx


26. Schiff S, Vallesi A, Mapelli D, Orsato R, Pellegrini A, Umilta C, et al. Impairment of response inhibition precedes motor alteration in the early stage of liver cirrhosis: a behavioral and elec-trophysiological study. Metab Brain Dis. 2005;20:381–92.

27. Kim Y, Park G, Lee M, Lee JH. Impairment of driving ability and neuropsychological function in patients with MHE disease. Cyberpsychol Behav. 2009;12(4):433–6.

28. Bajaj JS, Hafeezullah M, Hoffmann R. Minimal hepatic encephalopathy: a vehicle for acci-dents and traf fi c violations. Am J Gastroenterol. 2007;102(9):1903–9.

29. Cordoba J, Flavia M, Jacas C, et al. Quality of life and cognitive function in hepatitis C at dif-ferent stages of liver disease. J Hepatol. 2003;39:231–8.

30. Blanco M, Biever WJ, Gallagher JP, et al. The impact of secondary task cognitive processing demand on driving performance. Accid Anal Prev. 2006;38:895–906.

31. Reimer B, D’Ambrosio LA, et al. Task-induced fatigue and collisions in adult drivers with attention de fi cit hyperactivity disorder. Traf fi c Inj Prev. 2007;8:290–9.

32. Barkley RA, Guevremont DC, Anastopoulos AD, et al. Driving-related risks and outcomes of attention de fi cit hyperactivity disorder in adolescents and young adults: a 3- to 5-year follow-up survey. Pediatrics. 1993;92:212–8.

33. Philip P, Sagaspe P, Taillard J, et al. Fatigue, sleepiness, and performance in simulated versus real driving conditions. Sleep. 2005;28:1511–6.

34. Bajaj JS, HAfeezullah M, et al. The effect of fatigue on driving skills in patients with hepatic encephalopathy. Am J Gastroenterol. 2009;104(4):898–905.

35. Bajaj JS, Saeian K, Hafeezullah M, Hoffmann RG, Hammeke TA. Patients with minimal hepatic encephalopathy have poor insight into their driving skills. Clin Gastroenterol Hepatol. 2008;6(10):1135–9.

36. Barkley RA, Murphy KR, Dupaul GI, et al. Driving in young adults with attention de fi cit hyperactivity disorder: knowledge, performance, adverse outcomes, and the role of executive functioning. J Int Neuropsychol Soc. 2002;8:655–72.


38. Qadri AM, Ogunwale BO, Mullen KD. Can we ignore minimal hepatic encephalopathy any longer? Hepatology. 2007;45:547–8.

39. Bajaj JS, Etemadian A, Hafeezullah M, et al. Testing for minimal encephalopathy: diagnosis, clinical signi fi cance and recommendations. J Hepatol. 2005;42(Suppl):S45–53.

40. Vergara-Gomez M, Flavia-Olivella M, Gil-Prades M, et al. [Diagnosis and treatment of hepatic encephalopathy in Spain: results of a survey of hepatologists]. Gastroenterol Hepatol. 2006;29:1–6.

41. Gerber T, Schomerus H. Hepatic encephalopathy in liver cirrhosis: pathogenesis, diagnosis and management. Drugs. 2000;60:1353–70.

42. Dangleben DA, Jazaeri O, Wasser T, et al. Impact of cirrhosis on outcomes in trauma. J Am Coll Surg. 2006;203:908–13.

43. Demetriades D, Constantinou C, Salim A, et al. Liver cirrhosis in patients undergoing laparo-tomy for trauma: effect on outcomes. J Am Coll Surg. 2004;199:538–42.

44. Bajaj JS, Ananthakrishnan A, McGinley A, et al. Deleterious effect of cirrhosis on outcomes after motor vehicle crashes using the Nationwide Inpatient Sample. Am J Gastroenterol. 2008;103(7):1674–81.

45. Shawcross DL, Wright G, Olde Damink SW, et al. Role of ammonia and in fl ammation in mini-mal hepatic encephalopathy. Metab Brain Dis. 2007;22:125–38.

46. Dhiman RK, Sawhney MS, Chawla YK, et al. Ef fi cacy of lactulose in cirrhotic patients with subclinical hepatic encephalopathy. Dig Dis Sci. 2000;45:1549–52.

47. Prasad S, Dhiman RK, Duseja A, et al. Lactulose improves cognitive functions and health-related quality of life in patients with cirrhosis who have minimal hepatic encephalopathy. Hepatology. 2007;45:549–59.

48. Watanabe A, Sakai T, Sato S, et al. Clinical ef fi cacy of lactulose in cirrhotic patients with and without subclinical hepatic encephalopathy. Hepatology. 1997;26:1410–4.


49. Bajaj JS, Heuman DM, Wade JB, Gibson DP, Saeian K, Wegelin JA, Hafeezullah M, Bell DE, Sterling RK, Stravitz RT, Fuchs M, Luketic V, Sanyal AJ. Rifaximin improves driving simula-tor performance in a randomized trial of patients with minimal hepatic encephalopathy. Gastroenterology. 2011;140(2):478–87.

50. Kewman D, et al. Simulation training of psychomotor skills: teaching the brain-injured to drive. Rehabil Psychol. 1985;30(1):11–27.

51. Cohen SM, Kim A, Metropulos M, Ahn J. Legal rami fi cations for physicians of patients who drive with hepatic encephalopathy. Clin Gastroenterol Hepatol. 2011;9(2):156–60.

52. American Medical Association. Physician’s guide to assessing and counseling older drivers. 2nd ed (released 3 Feb 2010). http://www.ama-assn.org/ama/pub/physician-resources/public-health/promoting-healthy-lifestyles/geriatric-health/olderdriver-safety/assessing-counseling-older-drivers.shtml . Accessed 7 April 2010.

53. Dubinsky RM, Stein AC. Minimal hepatic encephalopathy and driving. Hepatology. 2009;50:1007–8.

54. Weissenborn K, Ennen JC, Schomerus H, et al. Neuropsychological characterization of hepatic encephalopathy. J Hepatol. 2001;34:768–73.

55. Weissenborn K, Heidenreich S, Ennen J, et al. Attention de fi cits in minimal hepatic encephal-opathy. Metab Brain Dis. 2001;16:13–9.

56. Kircheis G, Knoche A, Hilger N, et al. Hepatic encephalopathy and fi tness to drive. Gastroenterology. 2009;137(1706–15):e1–9.

http://www.ama-assn.org/ama/pub/physician-resources/public-health/promoting-healthy-lifestyles/geriatric-health/olderdriver-safety/assessing-counseling-older-drivers.shtml




Keywords Hepatic encephalopathy • Liver cirrhosis • Nutrition • Protein energy malnutrition • Protein • Ammonia

Introduction

Hepatic encephalopathy (HE) is a neurologic syndrome characterized by a wide spectrum of neuropsychiatric changes and alterations in neuromuscular function which are seen in patients with severe liver insuf fi ciency. HE may be present in patients with acute liver failure and is included among the symptoms for the diag-nosis of fulminant hepatic failure: in these patients survival is poor due to the severe prognosis of the underlying liver disease. Most frequently HE is seen in patients with chronic liver disease. It has been estimated that 30–40% of patients with liver cirrhosis will experience overt HE during the natural history of the disease. Symptoms of HE in chronic liver disease may appear as acute reversible episodes frequently associated with a precipitating cause. However, episodes of HE may also be recurrent with intermittent neurological symptoms negatively affecting the patient’s self-suf fi ciency [ 1 ] . Frequent HE precipitating events are constipation, hypokalemia, alkalosis, hyponatremia, hypovolemia, gastrointestinal bleeding, dehydration, infections, surgery, renal failure, diuretics, and psychoactive medica-tions. Patients with more severe liver insuf fi ciency and those with spontaneous or arti fi cially created porto-systemic shunts are at higher risk of HE.

Some cirrhotic patients, even if recognizable clinical symptoms of brain dysfunction are lacking, may show an abnormal performance when submitted to

M. Merli, MD (*) • M. Giusto, MD • O. Riggio, MD Department of Clinical Medicine , University “Sapienza” Roma , Viale Dell’Universita’ 37 , Rome 00185 , Italy e-mail: [email protected]

Chapter 16 Nutrition and Hepatic Encephalopathy

Manuela Merli , Michela Giusto , and Oliviero Riggio

200 M. Merli et al.

psychometric or computerized tests or electrophysiological techniques. The term minimal HE (MHE) has been proposed to de fi ne this condition [ 2 ] . This cognitive dysfunction may be present in 60–70% of cirrhotic patients; it may affect quality of life and even impair the execution of simple and complex tasks such as car driving [ 3 ] . The patients with MHE are considered to be at risk for the development of overt HE.

HE represents the second-most frequent cause of decompensation in cirrhotic patients after ascites and before variceal bleeding. Prognostic signi fi cance of HE in liver cirrhosis has been recognized in many reports [ 4 ] .

The mechanisms involved in the pathogenesis of HE are still a matter of debate and multiple factors are probably involved in the genesis of this neurologic syndrome. Gut-derived nitrogenous compounds are usually released from the intestine. These metabolites are normally detoxi fi ed by the liver but in cirrhosis their hepatic clear-ance is impaired. Portosystemic shunts causes blood to by-pass the liver and this also reduces metabolites detoxi fi cation. When ammonia or other gut-derived toxins accumulate in the blood they may also reach the brain through the blood–brain barrier, and exert a “toxic effect” on the brain function. Several other compounds, such as mercaptans, short-chain fatty acids amines, g -aminobutyric acid (GABA), endorphins, glutamate, endogenous benzodiazepine agonists, tryptophan and its metabolites have also been proposed [ 5 ] . As far as the mechanism involved in the central nervous system is concerned, in the last few years, “astrocytes swelling” has been identi fi ed as an important process negatively in fl uencing the neuronal neurotrans-mission as well as the brain energy production rate. The “astrocytes swelling hypothesis” is able to explain one of the key features of HE, namely, that the syn-drome is precipitated by heterogeneous factors [ 6 ] . Infection, for example, induces the astrocytes swelling by endotoxins and proin fl ammatory cytokines [ 6 ] .

Protein-Calorie Malnutrition in Cirrhosis

Alterations in nutritional status are a frequent fi nding in patients with cirrhosis [ 7– 9 ] either of alcoholic [ 7 ] or nonalcoholic origin [ 9 ] . The prevalence of malnutrition in cirrhosis has been reported to be as high as 65–90%. Patients with more advanced liver disease are more frequently malnourished [ 8 ] . On the other hand, more sophis-ticated methods to evaluate body composition have shown that alteration in cell mass or muscle function may be found also in compensated cirrhosis [ 10, 11 ] . The best de fi nition of malnutrition in cirrhotic patients is protein-calorie malnutrition (PCM), in fact both lean and fat tissue may be depleted. Depletion of adipose tissue is more frequent in women while muscle tissue is more often compromised in men [ 8, 9 ] .

Multiple factors are involved in the etiology of PCM in chronic liver disease (Table 16.1 ), dietary intake is inadequate to meet energy expenditure, absorption is compromised, and substrate utilization is impaired due to liver disease. A variety of events decrease the ability of the cirrhotic patient to control their dietary intake. It is commonly described that when these patients present new clinical symptoms,

20116 Nutrition and Hepatic Encephalopathy

they get worried that consumption of food would worsen their conditions. Patients with liver cirrhosis show an increased severity of gastrointestinal symptoms which has been associated with impaired nutritional status and health-related quality of life [ 12 ] . In cirrhotic patients intestinal transit is reduced [ 13 ] and ascites reduces the postprandial gastric volumes and accommodation [ 14 ] , further compromising nutritional intake. Paradoxically, nutrition is further neglected when these patients are hospitalized to treat the complications of the disease: they are starved to be sub-mitted to endoscopy, ultrasonography, contrast imaging, or other invasive procedures. The hospital staff in charge of the patient often considers nutrition of lower rele-vance with respect to the other complications that need to be treated.

Cirrhotic patients are further penalized due to more rapid transition to a “starvation pro fi le.” The liver, in fact, plays a central role in many metabolic pathways and the metabolic disturbances consequent to liver derangement induce profound modi fi cations in substrate utilization [ 15– 17 ] . Insulin resistance, manifested as high levels of circulating insulin and impaired glucose utilization [ 15, 18 ] affects the ability of glucose storage through glycogen synthesis. As a consequence the cir-rhotic liver is unable to adequately derive glucose from glycogen through glycog-enolysis and after a short-term fasting, gluconeogenesis is enhanced in these patients to produce glucose. To provide substrates for gluconeogenesis, alanine and glycerol are mobilized from muscle and adipose tissue deposits, respectively, thus causing skeletal muscle and adipose tissue catabolism. Previous studies have shown that a different eating pattern with 4–7 small meals, including a late-evening snack, by avoiding prolonged starvation periods, may improve the nitrogen economy in these patients and reverse this abnormal substrate oxidation [ 19, 20 ] . In a recent study, Plank et al. [ 21 ] provided in a group of cirrhotic patients a late-evening nutritional supple-ment over a 12-months period to test the hypothesis that, by shortening the night fast, the total protein stores would improve. They observed that total body protein, measured by neutron activation analysis, increased signi fi cantly in these patients throughout the observation period compared to baseline.

Anorexia Dietary restriction Unpalatable diet Dysgeusia Other gastrointestinal symptoms Ascites Hepatic encephalopathy Frequent hospitalization Diuretic therapy Lactulose treatment Pancreatic insuf fi ciency Bacterial overgrowth Rapid transition to a starvation pro fi le Decreased protein synthesis Disturbances in substrates utilization

Table 16.1 Main causes of malnutrition in cirrhotic patients

202 M. Merli et al.

Interestingly, the presence of nutritional alterations should not be considered only as a consequence of chronic liver disease, but it may even accelerate the natu-ral history of the disease and adversely affect the patients’ outcome. Prospective studies on large series of cirrhotic patients have in fact shown that severe malnutrition, as well as the presence of depletion in lean body mass, represents an independent prognostic factor in the survival of patients with liver cirrhosis [ 22, 23 ] .

Nutrition, Diet, and HE

There are several reasons why nutrition and diet should be carefully managed in cirrhotic patients to prevent or treat HE

1. PCM can be involved in the pathogenesis of HE. 2. The patient’s diet (mainly protein intake) has been invoked both as precipitating

factor and as treatment of HE. 3. Episodes of HE further in fl uence the dietary consumption due to the patient’s

attitude about feeding and physician prescriptions.

Role of Malnutrition in HE

Recent available information on interorgan ammonia exchange in liver cirrhosis have suggested that, in cirrhotic patients, due to the inability of urea synthesis in the failing liver, the muscle may have a crucial role in ammonia detoxi fi cation [ 24 ] . The muscle can remove ammonia from the circulation and release it as glutamine. Although this metabolic pathway does not result in a de fi nitive ammonia disposal (as glutamine reaches the small intestine and the colon mucosa, where it is converted once again into glutamic acid and ammonia), it has been proposed that muscle depletion may have relevant implications in favoring HE [ 6 ] (Fig. 16.1 ). An alternative mechanism to explain the possible relationship between muscle mass and HE takes into account that an increased glutamine release from muscle may also derive from an increased muscle protein catabolism. In this case the excess glutamine is drained to the small intestine and kidney and its conversion to glutamic acid and ammonia contributes to increase the whole body ammonia disposal. Patients with cirrhosis and malnutrition often have reduced muscle mass [ 25 ] . Despite the potential rele-vance of the correlation between malnutrition and HE, few studies have dealt with this topic and de fi nite conclusions are still lacking. Campillo et al. [ 26 ] have previ-ously reported that HE is independently related to low caloric intake in hospitalized patients with liver cirrhosis, but a potential link between nutritional status and cognition was not investigated.

Two studies have examined more recently the potential role of malnutrition in the development of HE with con fl icting results. Sörös et al. [ 27 ] examined 223


patients with nonalcoholic cirrhosis. These patients had a complete nutritional assessment (BMI, anthropometric measurements and bioelectric impedance analy-sis, and indirect calorimetry) and were evaluated for the presence of clinically overt HE (West Haven criteria). Fifty- fi ve percent of these patients had grade 1 HE and 7% grade 2 or 3; 38% had no evidence of neurologic impairment. Nutritional status and metabolic variables were similar in patients with and without HE and multivari-ate analysis failed to show that these parameters were independently related to HE. The authors conclude that malnutrition and catabolism did not seem to be indepen-dent risk factors for the presence of HE in patients with liver cirrhosis.

Kalaitzakis et al. [ 28 ] performed a prospective study in 128 patients with cirrhosis of various etiology evaluating HE, malnutrition, and diabetes. In this study, patients with MHE were also included. Forty percent of the patients were malnourished, 26% had diabetes, and 34% had HE. Patients with malnutrition suffered more frequently from HE when compared to those with good nutritional status ( p = 0.03). Plasma ammonia levels showed a correlation with muscle mass ( r = 0.28, p = 0.003) and insulin resistance ( r = 0.42, p < 0.001). Malnutrition and diabetes were indepen-dently correlated with the time needed to perform the number connection test A. In conclusion, due to methodological differences, these studies reached different conclusions and more studies are probably needed to better clarify the relation between nutritional status and HE. Despite the lack of clear evidence, muscle wasting and protein catabolism in cirrhotic patients should always be avoided and an adequate nutritional intake to maintain their muscle mass should be implemented. In fact, protein malnutrition may favor HE through indirect mechanism. We have recently shown that protein malnutrition in cirrhotic patients is an independent risk factor for severe infections [ 29 ] . Bacterial infections, due to increased endotoxins or through a cytokine release, are a well-known trigger for HE.

Fig. 16.1 Interorgan ammonia metabolism in health and in liver cirrhosis. GS glutamine-synthetase; HE hepatic encephalopathy. Adapted from Wright et al. [ 6 ] , with permission from John Wiley & Sons, Inc

204 M. Merli et al.

Diet as a Treatment of HE

The restriction of protein intake has traditionally been considered as a rule for the treatment of HE [ 30 ] . This was originated from old experimental studies showing that in porto-caval shunted dogs meat feeding caused neurological symptoms. Later on it was reported that the symptoms of HE were controlled by a low-protein diet, containing about 20 g proteins a day [ 31 ] . Based on these observations the restriction of protein intake in cirrhotic patients with HE became a common practice. It should also be considered that the therapeutic armamentarium for HE was extremely lim-ited at that time and protein restriction was one of the few treatment options.

In the last decade, the increased knowledge on the progressive deterioration of nutritional status in liver cirrhosis and improved comprehension of metabolic alter-ations in chronic liver disease has questioned the opportunity to adopt a severe and prolonged protein restriction in the treatment of HE [ 32 ] .

It has been recognized that protein restriction may increase muscle catabolism and the release of the amino acids, with a consequent elevation in serum ammonia concentrations and worsening of HE. In fact, while the limitation in protein intake tries to reduce the dietary nitrogen load to the liver, it increases, on the other hand, the nitrogen derived from muscle catabolism. The main goal of an adequate protein feeding in cirrhotic patients should be to avoid muscle protein breakdown.

Morgan et al. [ 33 ] have examined the relationship between protein intake and changes in HE in a large number of patients with alcoholic hepatitis, 63% with HE, during the fi rst weeks of hospitalization. All the patients were encouraged to eat a prescribed adequate diet and their 24-h dietary intake was assessed weekly. These authors reported that lower the protein intake in the previous week, the higher was the deterioration in their mental status suggesting that a diet lacking adequate protein content could favor HE. On the other hand, those patients who improved their mental status were those in whom a higher protein intake was recorded during the previous week.

Protein requirement and protein utilization were investigated in malnourished cirrhotic patients showing that long-term oral refeeding with increased amounts of proteins and energy intake was associated with high nitrogen retention and was able to induce signi fi cant protein synthesis [ 34 ] .

In 1997, the European Society of Parenteral and Enteral Nutrition published speci fi c guidelines for nutrition in liver disease and transplantation [ 35 ] . These guidelines stated for the fi rst time the higher protein requirements in cirrhotic patients and recommended a diet including at least 1.2 g/kg of proteins every day. Even the presence of HE was not considered a reason to decrease protein content in diet of at least 1.0–1.5 g/kg/day. If any protein restriction was needed, this was recommended to be only transient [ 35 ] . More recently, the same recommendations were also con fi rmed in the guidelines for the use of enteral nutrition in patients with liver diseases [ 36 ] .

A randomized study was performed to better clarify if a normal or high protein diet could be recommended in patients with overt HE [ 37 ] . All patients included


were hospitalized for episodic HE; none had alcoholic hepatitis, recent alcohol intake, gastrointestinal bleeding, benzodiazepine intake, and neurologic, respiratory, or cardiovascular comorbidities. Patients were randomized to receive two different diets: either a normal protein diet (1.2 g/kg/day) or a strict low-protein diet (0 g proteins for days 0–3, 12 g proteins for days 4–6, 24 g proteins for days 7–10) for 14 days through a nasogastric tube. A single lactulose enema was administered followed by Neomycin therapy in both groups. Ten patients in each group completed the study. Patients following a normal protein diet showed a similar improvement in HE, while the low-protein diet caused an increase in protein breakdown during the fi rst days. Apparently, therefore, protein restriction did not cause any major bene fi t on HE while, on the other hand, the low-protein diet exacerbated protein breakdown. These results were a further support to the safety of a normal protein intake during HE and demonstrated the harmful effect of a low-protein diet. Further reports have given evidence to the fact that a high-calorie high-protein diet might be well tolerated in patients with overt HE [ 38 ] . More recently a randomized study, performed in patients with compensated cirrhosis and MHE, suggested that eating a regular breakfast meal (500 kcal and 21 g of proteins) may improve their cognitive performance with regard to attention and executive function [ 39 ] .

HE In fl uences the Patient’s Attitude About Feeding and Physician Prescriptions

In spite of the advice of experts in the fi eld [ 35, 40, 41 ] , medical practitioners and dietitians often feel that protein restriction is necessary in patients with HE. This has been demonstrated by a number of surveys in different countries showing that moderate (30–50 g/day) or severe (<30 g/day) restriction of dietary protein intake was frequently prescribed for patients with HE. This opinion was reported either among medical practitioners [ 42 ] or in gastroenterologists [ 30 ] or in dietitians [ 43 ] . This perspective may induce the patients to believe that, after an episode of HE, protein restriction is advisable even as a long-term strategy.

Current Guidelines About Nutrition in Hepatic Encephalopathy

Patients with overt HE usually have advanced liver disease. As recommended in current guidelines their diet should provide at least 30 kcal/kg of body weight, 30–35% of calories as fat, and the remaining 50–55% as carbohydrates. The protein intake is expected to reach at least 1–1.2 g/kg of protein per day to maintain nitrogen homeostasis but requirements may be increased to 1.5 g/kg/day in malnourished patients to avoid endogenous protein breakdown (Table 16.2 ). Oral intake should be

206 M. Merli et al.

encouraged and diet needs to be cared for in these patients for adequate nutritional support. The consumption of 4–6 small meals a day is advisable and the positive role of breakfast and a late-evening meal has been already discussed. Whenever a patient is unable to maintain an adequate oral intake, oral nutrition supplements or tube feeding should be considered [ 36 ] . Enteral nutrition (EN) improves nutritional status, reduces complications, and prolongs survival in hospitalized cirrhotic patients with malnutrition; the possibility that the use of nasogastric tube may induce gastro-intestinal bleeding is not supported by the literature. For patients who cannot be adequately fed by EN or in whom EN is contraindicated, parenteral nutrition (PN) may be helpful. PN is indicated when the patient is considered unlikely to resume normal oral nutrition within the next 5–7 days irrespective of current nutritional status. When a patient comes to the hospital in hepatic coma, he/she may need to be supported with a complete parenteral nutrition [ 44 ] .

Patients with recurrent HE may present speci fi c problems with regard to the maintenance of an adequate protein intake due to protein intolerance or a general-ized decreased in food intake associated with the alteration in mental status. The utilization of alternative sources of proteins might be of help either as a more tolerable substitute of animal proteins or as a nutritional supplement.

Vegetable proteins have been claimed to be better tolerated than animal proteins in cirrhotic patients with HE [ 45 ] . The bene fi cial effects of a vegetable protein diet (green vegetables, fruits, cereals, and pulses) include a higher intestinal clearance of nitrogen-waste products due to the high fi ber content able to induce a greater bacterial mass, a shortened transit time, and a reduced colonic pH entrapping ammo-nia in the intestinal lumen. The clinical advantage of vegetable protein diets in HE has been reported in small series of patients with chronic HE but not con fi rmed by all authors [ 45 ] . Bloating, fl atulence, and early satiety are frequent in those consum-ing vegetarian diets and may cause poor tolerance in the long term. To obtain a more palatable and a more varied dietary regimen, vegetables may be supplemented with cheese and other milk-derived dietary products. A diet including vegetables, fruits,

Table 16.2 Recommended energy and protein intake in liver cirrhosis

Clinical condition Nonprotein energy (kcal/kg/day) Protein or amino acids (g/kg/day)

Compensated cirrhosis 25–35 1.0–1.2 Cirrhosis with malnutrition and/or

inadequate nutrient intake 35–40 1.5

Cirrhosis and low-grade encephalopathy

25–35 Transient 1.0–1.5 if protein intolerance: vegetable protein or BCAA supplement

Cirrhosis and high-grade encephalopathy

25–35 0.5–1 BCAA-enriched amino-acid solution

Reprinted from Plauth et al. [ 35 ] © 1997, with permission from Elsevier Frequent meals (4–7 per day with a late-evening meal). Provide micronutrients and vitamins if correction is needed. In patients with clinical signs of malnutrition, oral intake should be encour-aged and nutritional supplements may be added to provide the needed requirements. When nutritional supplementation is insuf fi cient to obtain the desired intake, enteral nutrition should be considered. Parenteral nutrition is used only when enteral feeding is not possible or impracticable


cereals, and milk-derived products planned to ensure at least 30 kcal/kg/day and 1.2 g of proteins/kg/day was well tolerated in 153 cirrhotic patients hospitalized with overt HE [ 38 ] .

Branched-chain amino acids (BCAA: isoleucine, leucine, and valine) are essential amino acids with a peculiar role in whole-body nitrogen metabolism. They have a stimulatory effect on protein synthesis, secretion of hepatocytes growth factor, glu-tamine production, and inhibitory effect on proteolysis. BCAA supplementation may ameliorate HE by promoting ammonia detoxi fi cation and through a competitive action on amino-acid transport across the blood–brain barrier [ 46 ] . Based on this possible pharmacologic effects in cirrhotic patients with encephalopathy, BCAA were ini-tially used as intravenous solutions in patients with severe hepatic coma as far as 25 years ago. Results of meta-analyses on the bene fi cial effects of BCAA in the treatment of HE and on patient’s survival were controversial. When BCAA were administered as long-term oral supplementation it appeared, however, that BCAA allowed a higher protein intake without inducing encephalopathy in cirrhotic patients with chronic recurrent HE or either improving the neurologic symptoms when they were present [ 47 ] . The nutritional and anticatabolic effect of BCAA may ameliorate the symptoms of HE also through the improvement of muscle protein catabolism. A long-term oral supplementation with BCAA in patients with advanced liver disease has been shown to increase serum albumin concentration [ 48 ] and even to have bene fi cial effects on the progression-free survival [ 49, 50 ] . In a double-blind randomized trial comparing BCAA supplementation with an equicaloric (maltodextrine) or an equinitrogen (lactoalbumin) supplementation for 12 months, a signi fi cant reduction in the number of hospital admissions and the length of hospital stay was seen in patients treated with BCAA as compared with controls [ 49 ] . The main problem in the study was a higher noncompliance and low palatability of the BCAA formulation. The second study [ 50 ] enrolled 622 patients with cirrhosis treated (long term) with BCAA supplementation vs. diet alone; in the treated group, a signi fi cant improvement in a composite end-point [(progression to liver failure or death) (hazard ratio: 0.67, con fi dence interval: 0.49–0.93)] and a tendency to a reduced HE incidence was reported.

In conclusion, although the use of BCAA supplementation may be limited by the patients’ compliance and its availability (due to its high costs), there is a growing evidence that these amino acids may help intolerant patients to reach the amount of protein intake needed and prevent endogenous protein breakdown, thus represent-ing a valid tool in the management of those cases at an advanced stage of the disease and HE.

References

1. Bajaj JS, Wade JB, Sanyal AJ. Spectrum of neurocognitive impairment in cirrhosis: implica-tions for the assessment of hepatic encephalopathy. Hepatology. 2009;6:2214–21.

2. Amodio P, Montagnese S, Gatta A, et al. Characteristics of minimal hepatic encephalopathy. Metab Brain Dis. 2004;19:253–67.

3. Bajaj JS, Hafeezullah M, Hoffmann RG, et al. Minimal hepatic encephalopathy: a vehicle for accident and traf fi c violations. Am J Gastroenterol. 2007;102:1903–9.

208 M. Merli et al.

4. Bustamante J, Rimola A, Ventura PJ, et al. Prognostic signi fi cance of hepatic encephalopathy in patients with cirrhosis. J Hepatol. 1999;30:890–5.

5. McPhail MJW, Bajaj JS, Thomas HC, et al. Pathogenesis and diagnosis of hepatic encephalopathy. Expert Rev Gastroenterol Hepatol. 2010;4:365–8.

6. Wright G, Noiret L, Olde Damink SW, et al. Interorgan ammonia metabolism in liver failure: basis of current and future therapies. Liver Int. 2011;31:163–75.

7. Mendehall CL, Anderson S, Weesner RE, et al. Protein-calorie malnutrition associated with alcoholic hepatitis. Am J Med. 1994;76:211–22.

8. Italian Multicentric Cooperative Project on Nutrition in Liver Cirrhosis. Nutritional status in cirrhosis. J Hepatol. 1994;21:317–25.

9. Caregaro L, Alberino F, Amodio P, et al. Malnutrition in alcoholic and virus-related cirrhosis. Am J Clin Nutr. 1996;63:602–9.

10. Prijatmoko D, Strauss BJG, Lambert JR, et al. Early detection of protein depletion in alcoholic cirrhosis: role of body composition analysis. Gastroenterology. 1993;105:1839–45.

11. Alvares-da-Silvia MR, Reverbel da Silveira T. Comparison between handgrip strength, sub-jective global assessment, and prognostic nutritional index in assessing malnutrition and pre-dicting clinical outcome in cirrhotic outpatients. Nutrition. 2005;21:113–7.

12. Kalaitzaskis E, Simrén M, Olsson R, et al. Gastrointestinal symptoms in patients with liver cirrhosis: associations with nutritional status and health-related quality of life. Scand J Gastroenterol. 2006;41:1464–72.

13. Gupta A, Dhiman RK, Kumari S, et al. Role of small intestinal bacterial overgrowth and delayed gastrointestinal transit time in cirrhotic patients with minimal hepatic encephalopathy. J Hepatol. 2010;53:849–55.

14. Aquel BA, Scolapio JS, Dickson RC, et al. Contribution of ascites to impaired gastric function and nutritional intake in patients with cirrhosis and ascites. Clin Gastroenterol Hepatol. 2005;3:1095–100.

15. Merli M, Erikson SL, Hagenfeldt H, et al. Splanchnic and peripheral exchange of FFA in patients with liver cirrhosis. J Hepatol. 1986;3:348–55.

16. Merli M, Riggio O, Romiti A, et al. Basal energy production rate and substrate use in stable cirrhotic patients. Hepatology. 1990;12:106–12.

17. Muller MJ, Lautz HU, Plogman B, et al. Energy expenditure and substrate oxidation in patients with cirrhosis: the impact of cause, clinical staging and nutritional status. Hepatology. 1992;15:782–94.

18. Merli M, Leonetti F, Riggio O, et al. Glucose intolerance and insulin resistance in cirrhosis are normalized after liver transplantation. Hepatology. 1999;30:649–54.

19. Verboeket-van de Venne WPHG, Westerterp KR, van Hoek B, et al. Energy expenditure and substrate metabolism in patients with cirrhosis of the liver: effects of the pattern of food intake. Gut. 1995;36:110–6.

20. Zillikens MC, van den Berg JWO, Wattimena JLD, et al. Nocturnal glucose supplementation. The effects on protein metabolism in cirrhotic patients and in healthy controls. J Hepatol. 1993;17:377–83.

21. Plank LD, Gane EJ, Peng S, et al. Nocturnal nutritional supplementation improves total body protein status of patients with liver cirrhosis: a randomized 12-month trial. Hepatology. 2008;48:557–66.

22. Merli M, Riggio O, Dally L, et al. Does malnutrition affect survival in cirrhosis? Hepatology. 1996;23:1041–6.

23. Gunsar F, Raimondo ML, Jones S, et al. Nutritional status and prognosis in cirrhotic patients. Aliment Pharmacol Ther. 2006;24:563–72.

24. Olde Damink SWM, Jalan R, Redhead DN, et al. Inter organ ammonia and amino acid metabo-lism in metabolically stable patients with cirrhosis and a TIPSS. Hepatology. 2002;37:1163–70.

25. Peng S, Lindsay DP, McCall JL, et al. Body composition, muscle function, and energy expendi-ture in patients with liver cirrhosis: a comprehensive study. Am J Clin Nutr. 2007;85:1257–66.

26. Campillo B, Richardet JP, Scherman E, et al. Evaluation of nutritional practice in hospitalized cirrhotic patients: results of a prospective study. Nutrition. 2003;19:515–21.


27. Sörös P, Böttcher J, Weissenborn K, et al. Malnutrition and hypermetabolism are not risk factors for the presence of hepatic encephalopathy: a cross-sectional study. J Gastroenterol Hepatol. 2008;23:606–10.

28. Kalaitzakis E, Olsson R, Henfridsson P, et al. Malnutrition and diabetes mellitus are related to hepatic encephalopathy in patients with liver cirrhosis. Liver Int. 2007;27:1194–201.

29. Merli M, Lucidi C, Giannelli V, et al. Cirrhotic patients are at risk for health-care-associated bacterial infections. Clin Gastroenterol Hepatol. 1997;16:43–5.

30. Merli M, Riggio O. Dietary and nutritional indications in hepatic encephalopathy. Metab Brain Dis. 2009;24:211–21.

31. Sherlock S, Summerskill WHJ, White LP, et al. Portal-systemic encephalopathy. Neurological complications of liver disease. Lancet. 1954;267:454–7.

32. Mullen KD, Dasarathy S. Protein restriction in hepatic encephalopathy: necessary evil or illogical dogma? J Hepatol. 2004;41:147–8.

33. Morgan TR, Moritz TE, Mendenhall CL, et al. Protein consumption and hepatic encephalopa-thy in alcoholic hepatitis. J Am Coll Nutr. 1995;2:152–8.

34. Kondrup J, Nielsen K, Juul A. Effect of long-term refeeding on protein metabolism in patients with cirrhosis of the liver. Br J Nutr. 1997;77:197–212.

35. Plauth M, Merli M, Kondrup J, et al. ESPEN guidelines for nutrition in liver disease and transplantation. Clin Nutr. 1997;16:43–5.

36. Plauth M, Cabré E, Riggio O, et al. ESPEN guidelines on enteral nutrition: liver disease. Clin Nutr. 2006;25:285–94.

37. Cordoba J, Lopez-Hellin J, Planas M, et al. Normal protein diet for episodic hepatic encephal-opathy results of a randomized study. J Hepatol. 2004;41:38–43.

38. Gheorghe L, Jacob R, Vadan R, et al. Improvement of hepatic encephalopathy using a modi fi ed high-calorie high-protein diet. Rom J Gastroenterol. 2005;3:231–8.

39. Vaisman N, Katzman H, Carmiel-Haggai M, et al. Breakfast improves cognitive function in cirrhotic patients with cognitive impairment. Am J Clin Nutr. 2010;92:137–40.

40. Mizock BA. Nutritional support in hepatic encephalopathy. Nutrition. 1999;15:220–8. 41. Blei AT, Cordoba J. Hepatic encephalopathy. Am J Gastroenterol. 2001;96:1968–75. 42. Soulsby CT, Morgan MY. Dietary management of hepatic encephalopathy in cirrhotic patients:

survey of current practice in United Kingdom. BMJ. 1999;318:1391. 43. Heyman JK, Whit fi eld CJ, Brock KE, et al. Dietary protein intakes in patients with hepatic

encephalopathy and cirrhosis: current practice in NSW and ACT. Med J Aust. 2006;185:542–3.

44. Plauth M, Cabré E, Campillo B, et al. ESPEN guidelines on parenteral nutrition: hepatology. Clin Nutr. 2009;28:436–44.

45. Amodio P, Caregaro L, Pettinò E, et al. Vegetarian diets in hepatic encephalopathy: facts or fantasies? Dig Liver Dis. 2001;33:492–500.

46. Holecek M. Three targets of branched-chain amino acid supplementation in the treatment of liver disease. Nutrition. 2010;26:482–90.

47. Als Nielsen B, Koretz RL, Kjaergard LL, et al. Branched chain amino acids for hepatic enceph-alopathy (Cochrane review). Cochrane Database Syst Rev. In The Cochrane Library, Issue 2. Chichester: Wiley; 2004.

48. Sato S, Watanabe A, Muto Y, et al. Clinical comparison of branched-chain amino acid (L-Leucine, L-Isoleucine, L-Valine) granules and oral nutrition for hepatic insuf fi ciency in patients with decompensated liver cirrhosis (LIV-EN study). Hepatol Res. 2005;31:232–40.

49. Marchesini G, Bianchi G, Merli M, et al. Nutritional supplementation with branched-chain amino acids in advanced cirrhosis: a double-blind, randomized trial. Gastroenterology. 2003;124:1792–801.

50. Muto Y, Sato S, Watanabe A, et al. Effects of oral branched-chain amino acid granules on event-free survival in patients with liver cirrhosis. Clin Gastroenterol Hepatol. 2005;3:705–13.


Keywords Transjugular shunt • TIPS • Hepatic encephalopathy • Prediction of HE • Prevention of shunt-induced HE • Portosystemic pressure gradient

Introduction

Hepatic encephalopathy (HE) is a complex phenomenon which depends on both liver dysfunction and portosystemic shunting. Thus, patients with acute hepatic fail-ure may develop HE without any portosystemic shunting while patients with huge shunts may develop HE without signi fi cant liver dysfunction [ 1 ] . In patients with cirrhosis, HE (Type C HE) is a result of both components with variable contribu-tion. In addition, most of these patients may suffer from non-hepatic, secondary factors such as hypovolemia, hypotension, anaemia, electrolyte imbalance, renal failure, malnutrition, and wasting which may contribute to HE.

The Eck fi stula [ 2 ] was the fi rst animal model demonstrating that diversion of the portal blood fl ow results in a cerebral disease which can be provoked by meat inges-tion [ 3 ] . Since then, numerous models have been investigated using portosystemic shunts or experimental liver cirrhosis [ 4 ] . However, there is no animal model avail-able which closely resembles the human situation with a combination of shunting and cirrhosis. The transjugular intrahepatic portosystemic shunt (TIPS) is an ideal model to investigate HE because the technique allows repeated measurements in

M. Rössle, MD (*) Department of Gastroenterology and Radiology , University Hospital Freiburg , Hugstetter Strasse 55 , Freiburg 79106 , Germany e-mail: [email protected]

W. Euringer, MD Department of Radiology , University Hospital Freiburg , Hugstetter Strasse 55 , Freiburg 79106 , Germany

Chapter 17 Hepatic Encephalopathy in Patients with Transjugular Intrahepatic Portosystemic Shunt (TIPS)

Martin Rössle and Wulf Euringer

212 M. Rössle and W. Euringer

humans of portal hemodynamics, shunt fl ow, and parameters of liver function as well. In the last 2 decades, it has been increasingly applied for the treatment of symptomatic portal hypertension and this has markedly stimulated the investigation of HE [ 5 ] . However, most studies available are of questionable quality due to a number of problems such as inappropriate design, inappropriate methods, and unblinded investigators.

The following article tries to critically summarize the present knowledge obtained in TIPS patients and discuss the dif fi culties of its assessment, prediction, prevention, and treatment on the basis of the present literature.

Assessment and Incidence of HE

Several aspects suggest that assessment of HE was inappropriate in most of the previous studies. In particular, previously applied tests for the assessment of HE severity are now questioned. These include the West-Haven criteria which is subjec-tive in nature with high inter-observer variability regarding the staging of lower grades of HE [ 6, 7 ] . The diagnosis of minimal HE (mHE) is an even greater problem which in part may be due to the limitations of the most often applied paper pencil tests [ 6– 11 ] . To overcome these problems, the critical fl icker frequency test (CFF) was introduced and investigated for the assessment of mHE and overt HE [ 12, 13 ] . This test seems to be an objective and reproducible diagnostic tool with little bias in training effects, education, and time of testing or inter-observer variability. A recent study by Kircheis et al. [ 14 ] compared the results obtained with CFF to a battery of computerized psychometric tests and clinical assessment by the West-Haven criteria which served as gold standards for mHE and overt HE. Sixty-three patients were investigated before and after TIPS and compared to a control group of 34 age-matched cirrhotic patients without TIPS. A clear correlation was found between HE severity assessed with the West-Haven criteria, CFF, and the psychometric tests at baseline. However, the TIPS-induced changes assessed by the West-Haven criteria were only re fl ected by the CFF. Neither the worsening nor the improvement of the HE severity after TIPS implantation was re fl ected in respective changes in the different computerized psychometric test results. The lack of correlation of most of the psycho-metric tests with HE severity (West-Haven criteria) and the CFF in the longitudinal assessment after TIPS was interpreted as a lack of reliability and reproducibility of the psychometric tests. Overall, these results question the usefulness of psychometric tests for follow-up investigations in clinical trials.

In addition to the methodological problems, the design of most studies may not be appropriate to investigate HE. First, longitudinal cohort studies may be biased by comparing a retrospective evaluation before the TIPS (past history of HE together with the assessment at index hospitalization) with a prospective evaluation after the TIPS. Except in the study by Kircheis et al. [ 14 ] , exact data on the observation period before the procedure are not given [ 15– 22 ] . Second, in the numerous random-ized trials summarized and analysed in respective meta-analyses comparing TIPS

21317 Hepatic Encephalopathy in Patients with Transjugular Intrahepatic…

with medical treatment of variceal bleeding [ 23, 24 ] or refractory ascites [ 25 ] , the evaluation of HE may be biased because investigators were not blinded. It can be assumed that investigators expected a higher risk of HE in the TIPS groups, a fact which may have in fl uenced the result. Third, HE often presents as an episodic and self-limiting disease which may not be evaluated by regular outpatient visits. Assessment using a diary has not been performed so far.

The incidence of post-TIPS encephalopathy varies from 15 to 48% [ 14– 22 ] . In controlled trials comparing TIPS with alternative forms of therapy, the inci-dence of encephalopathy was always greater in patients who received TIPS. Thus, a meta-analysis including studies in patients treated for variceal bleeding showed 1-year probabilities of overt HE of 19 and 35% for medical and TIPS treatment, respec-tively [ 23 ] . In another analysis comparing medical treatment with TIPS, one serious HE episode occurred for every eight TIPS procedures [ 24 ] . In patients with ascites, a recent meta-analysis of individual patient data [ 25 ] showed that the cumulative probability of developing the fi rst episode of HE during follow-up was not different between TIPS and paracentesis groups ( P = 0.36 by log-rank) and a similar result was found for the development of severe HE ( P = 0.46 by log-rank). However, when the average number of episodes-per-patient was considered, patients allocated to TIPS had signi fi cantly more episodes of HE with regard to both, total number of episodes (1.13 ± 1.93 vs. 0.63 ± 1.18, P = 0.006) and number of severe episodes (0.68 ± 1.0 vs. 0.24 ± 0.50, P = 0.008).

The recent study by Kircheis et al. [ 14 ] was designed to assess HE in a suf fi cient number of patients receiving TIPS as well as in controls not receiving the intervention. Their data showed a stable HE severity in the control group during an observation period of 442 ± 428 days with only minimal changes in CFF. In the TIPS group, however, HE severity did not change in 44% of the patients, deteriorated in 35%, and improved in 21% of the patients. Thus, while controls remained stable, TIPS had the potential to deteriorate as well as to improve HE.

Prediction of HE After TIPS

Since HE depends on both liver function and portosystemic shunting, parameters of liver function as well as of shunting may predict HE in patients with cirrhosis with or without TIPS. In addition, biometrical variables may be important such as age and gender. Furthermore, in most patients with advanced cirrhosis secondary factors such as low blood pressure, renal insuf fi ciency, electrolyte abnormalities, malnutrition, etc. may contribute to HE (Table 17.1 ). It is the nature of portosystemic shunting to worsen the hepatogenic factors of HE. However, the shunt may improve some of the secondary factors making the prediction of HE more complex and unclear. Accordingly, a variety of patterns of predictors including primary, biometrical, and secondary prognostic factors have been suggested. Most often, increased age, advanced liver failure (expressed by elevated bilirubin), a history of encephalopathy before TIPS insertion, and serum sodium concentration [ 16– 18, 20 ] have been found to predict


HE. With respect to pre-TIPS HE as a predictor of post-TIPS HE, the study by Kircheis et al. [ 14 ] did not con fi rm previous fi ndings using a different methodology. Predictors, other than biometrical ones, have limited value in patients with an acute bleed since bleeding limits the interpretation of laboratory and psycho-neurological parameters.

In the meta-analysis of individual patient data [ 25 ] , independent predictors of post-TIPS HE in patients treated for refractory ascites were baseline mean arterial pressure (MAP) (HR 0.93, CI 0.89–0.98; P = 0.004), MELD score at baseline (HR 1.068, CI 1.006–1.13; P = 0.032), and post-TIPS porto-systemic pressure gradient (HR 0.93, CI 0.87–0.99; P = 0.048). An explanation for the correlation of baseline MAP with HE may be that a low MAP re fl ects poor liver and brain perfusion together with advanced disease. Unfortunately, the study by Salerno et al. [ 25 ] does not provide thresholds with lower or higher probabilities of HE after TIPS. However, with a mean MAP of 87 mmHg and a mean MELD score of 12.5, values of < 80 mmHg or above 15, respectively, may be regarded as risk indicators for HE .

With respect to the hepatic arterial or portal hemodynamics, no correlation could be seen between the increase in hepatic arterial blood fl ow after TIPS (so-called buffer response) and the incidence of post procedural HE [ 26, 27 ] . However, patients with a loss of portal blood fl ow before TIPS are protected against HE after TIPS [ 28, 29 ] .

Most of the variables predicting HE are also predictors for survival after TIPS. As a reliable marker of liver function bilirubin plays a dominant role in predicting both HE and mortality in patients not having cholestatic disease. A value above 3 mg/dL is critical and above 5 mg/mL a relative contraindication for a TIPS in bleeders as well as in ascites patients [ 30– 34 ] . As shown recently [ 14 ] , the extent of pre-TIPS HE is a major predictor for long-term survival in patients undergoing TIPS implantation. Patients with pre-existing manifest HE have a signi fi cantly reduced survival rate after TIPS implantation. This prognostic information was obtained by a pre-TIPS CFF measurement. Those patients with a CFF below 37 Hz prior to TIPS implantation have a signi fi cantly reduced long-term survival after TIPS implantation than those with a CFF above this threshold [ 14 ] .

Table 17.1 Secondary factors contributing to HE and effect of the TIPS treatment

Prominent feature Direct effect of TIPS

Cerebral Older age, pre-existing vascular or alcoholic damage No direct effect Cardiac Systolic and diastolic dysfunction due

to cirrhosis or toxins No direct effect

Hemodynamic Hypovolemia due to vasodilatation and ascites production

Improved by TIPS

Renal Hepatorenal syndrome Improved by TIPS Hematologic Anaemia due to GI-bleeding and hypersplenism

causing fatigue Improved by TIPS

Nutritional Muscle wasting may affect ammonia metabolism Improved by TIPS Metabolic Hyponatremia, nocturnal hypoglycaemia, hypo-

phosphatemia, vitamin B de fi ciency, thiamine de fi ciency

Improved by TIPS


Since TIPS is expected to worsen HE, it is not surprising that attention has been focused exclusively on the factors predicting HE. However, as shown recently, TIPS may also improve HE [ 14 ] . If those patients could be selected with suf fi cient accu-racy, TIPS may rather be an indication than a contraindication. This requires the knowledge of predictive markers for a positive effect of the TIPS on pre-existing HE which have not been investigated so far. Candidate predictors for an improve-ment of HE after TIPS may in particular be some secondary factors of HE (Table 17.1 ) which have a high potential of improvement by the TIPS treatment.

One of these factors is the systemic circulation. It has been demonstrated that within a short time after the TIPS, the central venous pressure and the arterial blood pressure increase with a concomitant decrease of the heart rate [ 32 ] . In addition, the hyperdynamic circulation improves almost reaching normal values for the periph-eral resistance and cardiac output within 1 year of follow-up [ 32 ] . This is accompa-nied by normalization of the plasma renin activity, aldosterone, and norepinephrine concentrations [ 32 ] . As a consequence of the improvement in the systemic hemody-namics after TIPS, renal function also normalizes during a 1 year follow-up which is accompanied by an improvement of the dilutional hyponatremia [ 32 ] .

Malnutrition and muscle wasting are seen in most patients with cirrhosis and refractory ascites and have a negative effect on survival and HE [ 35, 36 ] . Wasting may not only affect the ammonia metabolism in muscle, but may also lead to decreased synthetic function of the liver. This affects many biochemical and even hemodynamic variables such as decrease in serum albumin concentration present in patients with cirrhosis. In contrast to serial paracentesis , which leads to a protein loss of about 200 g/10 L of ascites removed (including the albumin substitution of 8 g/L), TIPS increases the plasma albumin concentration and increases body weight despite resolution of ascites [ 31 ] . In addition, three studies show a signi fi cant improvement in dry weight, total body nitrogen, total body fat, and total body pro-tein [ 37– 39 ] .

Prevention of HE

Attempts have been made to limit shunting with its negative effects on liver function and HE by reducing the diameter of the shunt. The degree of shunting can be visualized semi-quantitatively by portography. As demonstrated in Fig. 17.1 , a reduction of the pressure gradient by 50% or more of the pre-TIPS gradient commonly results in a loss of portal liver blood fl ow equivalent to 100% shunting. Fortunately, the loss or the reduction of the portal perfusion induces an immediate rise in the arterial blood fl ow which is known as the arterial buffer response [ 27 ] . As demonstrated by endoluminal fl ow measurements during the TIPS procedure, the calculated average arterial liver perfusion per minute increased from 599 ± 100 mL/min before to 749 ± 161 mL/min after TIPS creation [ 40 ] . The effect occurred within seconds after opening of the shunt and disappeared also within seconds after its balloon occlusion.


It is assumed that the arterial buffer response does not fully compensate for the loss of the portal hepatic perfusion. Therefore, the use of smaller shunts (<10 mm) has been proposed to prevent complete diversion of the portal blood fl ow and also ef fl ux of arterial fl ow retrograde through the portal vein. This is supported by the fact that larger shunts with a lower portal-systemic pressure gradient were identi fi ed as an independent risk factor for post-TIPS HE and survival [ 25, 41– 43 ] . In the study by Casado et al. [ 42 ] , 23 out of 25 patients who developed HE after TIPS had a pressure gradient <12 mmHg. The close correlation between the reduction of the pressure gradient and post-shunt HE has also been demonstrated in previous studies with surgical shunts [ 44 ] . Wider shunts with a greater pressure reduction resulted in signi fi cantly increased incidence of HE. Thus, a recent uncontrolled study in patients with ascites suggested that an incomplete stent expansion during TIPS construction may reduce the occurrence of HE [ 45 ] . However, this study used self-expandable nitinol stents which do not hold a given smaller diameter but expand to their nomi-nal diameter due to the memory character of the nitinol. This is not the case with the Viatorr stent which retains the adjusted diameter.

To further prove the advantage of smaller shunts with respect to HE, a recent randomized study compared 8 mm with 10 mm TIPS using a covered stent graft [ 46 ] . The study was stopped prematurely because of a less ef fi cient control of com-plications of portal hypertension, which could have been predicted. Thus, among the 12 patients with the smaller stent, one patient re-bled and 5 continued to have high-risk varices which needed further treatment for reducing the risk of rebleeding (i.e. re-TIPS, endoscopic ligation, variceal embolization, or beta-blockers). When patients treated for refractory ascites were considered, the majority of patients (6 out of 10 patients) in the 8-mm stent group continued to have ascites and needed to be submitted to repeated paracentesis after the procedure. Because of the reduced ef fi ciency, the authors did not recommend the use of 8 mm stents without having the possibility to correct shunt ef fi ciency. This possibility, however, is provided by

Fig. 17.1 Portal hepatic blood fl ow in a cirrhotic patient before and after the TIPS implantation. Before TIPS, anterograde portal blood fl ow is seen. The implantation of an 8-mm stent resulted in a reduction of the pressure gradient by 50% from 24 to 12 mmHg leading to a complete deviation of the portal blood fl ow through the shunt


using stents with a nominal diameter of 10 mm that can be expanded to 8 mm only and enlarged to 10 mm if necessary. Such an approach can be achieved using the Viatorr stent (Gore) which allows stepwise enlargement due to its speci fi c design.

Not only the shunt diameter, but also the design of the stent has been found to in fl uence the occurrence of HE. It has recently been shown that the covered stent (Viatorr) has a reduced risk of HE and may, therefore, be preferred in patients with a higher risk of HE [ 47 ] . However, this fi nding is invalid because the diameters of the covered stents were smaller as compared to those of the bare stents and, there-fore, the groups were not comparable [ 48 ] . In contrast, covered stents can be expected to have even a higher risk of HE than bare stents. As shown with bare stents, HE usually becomes clinically apparent 2–3 weeks after TIPS insertion and then begins to decline (as measured by the portosystemic encephalopathy index) at 6 months [ 15, 18 ] . This may be due to shunt dysfunction over time which is a common phenomenon after placement of bare stents. With the use of covered stent grafts, post-TIPS HE is no more con fi ned to the postoperative period but remains a long-term problem because of the improved patency of these stents [ 20 ] . Therefore, in a patient with a higher risk of shunt-induced HE, uncovered stents may be preferred because they may narrow with time preventing worsening of liver function or HE, whereas patients with a low risk of these complications may have a covered stent a priori to avoid unnecessary revisions.

Treatment of Shunt-Induced HE

Treatment of HE is medical in most of the patients and consists of lactulose and non-absorbable antibiotics (neomycin or rifaximin) [ 15, 16 ] . In most patients, the encephalopathy rapidly improves with supportive and standard therapy. In case of medical therapy failure, the TIPS diameter can be reduced or the shunt occluded [ 49– 52 ] . In this situation, one should be assured that the patient’s quality of life bene fi ts more from improving HE than it worsens by the reaccumulation of ascites. Fortunately, in a series of 1,000 patients, the need for shunt reduction for debilitating HE was only 3% [ 52 ] . According to one randomized study, pharmacological prophy-laxis of HE is not effective and cannot be recommended for routine use [ 53 ] .

Conclusions

The present knowledge of the incidence of HE after TIPS implantation and its prediction is limited. Studies assessing HE may be biased by inappropriate methods and design and may, therefore, provide rather qualitative but not quantitative infor-mation. Without doubt, TIPS certainly increases the incidence of HE but the degree of the effect is not suf fi ciently quanti fi ed. In addition, the factors predicting improvement of HE by TIPS need to be established.


Prevention of HE may be achieved by creation of smaller shunts with the potential of further dilatation in case of insuf fi cient ef fi cacy with respect to control of ascites or variceal bleeding. Even in patients with refractory ascites, hepatorenal syndrome or hydrothorax that are likely to require larger shunts, smaller shunts may be implanted and dilated further after a stable course within the following 3 months.

References

1. Mullen KD, Gacad R. Hepatic encephalopathy. Gastroenterologist. 1996;4:188–202. 2. Eck NVK. Ligature of portal vein. Translation by Child CG. Surg Gynecol Obstet. 1953;96:375. 3. Balo J, Korpassy B. The encephalitis of dogs with Eck fi stula fed on meat. Arch Pathol.

1932;13:80. 4. Mullen KD, McCullough AL. Problems with animal models of chronic liver disease: sugges-

tions for improvement in standardization. Hepatology. 1989;9:500–3. 5. Rössle M, Siegerstetter V, Huber M, et al. The fi rst decade of the transjugular intrahepatic

portosystemic shunt (TIPS): state of the art. Liver. 1998;18:73–89. 6. Kircheis G, Görtelmeyer R, Grafe S, et al. Critical assessment of the PHES test battery in patients

with low-grade hepatic encephalopathy. In: Häussinger D, Kircheis G, Schliess F, editors. Hepatic encephalopathy and nitrogen metabolism. Dordrecht: Springer; 2006. p. 495–504.

7. Kircheis G, Fleig WE, Görtelmeyer R, Grafe S, Häussinger D. Assessment of low-grade hepatic encephalopathy: a critical analysis. J Hepatol. 2007;47:642–50.

8. Ferenci P, Lockwood AR, Mullen K, et al. Hepatic encephalopathy -de fi nition, nomenclature, diagnosis, and quanti fi cation: fi nal report of the working party at the 11th World Congress of Gastroenterology, Vienna 1998. Hepatology. 2002;35:716–21.

9. Weissenborn K. Minimal hepatic encephalopathy: a permanent source of discussion. Hepatology. 2002;35:494–5.

10. Quero JC, Hartmann IJ, Meulstee J, et al. The diagnosis of subclinical encephalopathy in patients with cirrhosis using neuropsychological tests and automated electroencephalogram analysis. Hepatology. 1996;24:556–60.

11. Weissenborn K, Rückert N, Hecker H, et al. The number connection tests A and B: interindi-vidual variability and use for the assessment of early hepatic encephalopathy. J Hepatol. 1998;28:646–53.

12. Kircheis G, Wettstein M, Timmermann L, et al. Critical fl icker frequency for quanti fi cation of low grade hepatic encephalopathy. Hepatology. 2002;35:357–66.

13. Sharma P, Sharma BC, Puri V, et al. Critical fl icker frequency: diagnostic tool for minimal hepatic encephalopathy. J Hepatol. 2007;47:10–1.

14. Kircheis G, Bode JG, Hilger N, et al. Diagnostic and prognostic values of critical fl icker frequency determination as new diagnostic tool for objective HE evaluation in patients undergoing TIPS implantation. Eur J Gastroenterol Hepatol. 2009;21:1383–94.

15. Sanyal AJ, Freedman AM, Shiffman ML, et al. Portosystemic encephalopathy after transjugu-lar intrahepatic portosystemic shunt: results of a prospective controlled study. Hepatology. 1994;20:46–55.

16. Somberg KA, Riegler JL, LaBerge JM, et al. Hepatic encephalopathy after transjugular intrahe-patic portosystemic shunts: incidence and risk factors. Am J Gastroenterol. 1995;90:549–55.

17. Jalan R, Elton RA, Redhead DN, et al. Analysis of prognostic variables in the prediction of mortality, shunt failure, variceal rebleeding and encephalopathy following the transjugular intrahepatic portosystemic stent-shunt for variceal haemorrhage. J Hepatol. 1995;23:123–8.

18. Riggio O, Merli M, Pedretti G, et al. Hepatic encephalopathy after transjugular intrahepatic portosystemic shunt. Incidence and risk factors. Dig Dis Sci. 1996;41:578–84.


19. Nolte W, Wiltfang G, Schindler C, et al. Portosystemic hepatic encephalopathy after transjugular intrahepatic portosystemic shunt in patients with cirrhosis: clinical, laboratory, psychometric, and electroencephalographic investigations. Hepatology. 1998;28:1215–25.

20. Riggio O, Angeloni S, Salvatori FM, et al. Incidence, natural history, and risk factors of hepatic encephalopathy after transjugular intrahepatic portosystemic shunt with polytetra fl uoroethylene-covered stent grafts. Am J Gastroenterol. 2008;103:2738–46.

21. Pomier-Layrargues G. TIPS and hepatic encephalopathy. Semin Liver Dis. 1996;16:315–20. 22. Rossle M, Piotraschke J. Transjugular intrahepatic portosystemic shunt and hepatic encephal-

opathy. Dig Dis. 1996;14 Suppl 1:12–9. 23. Luca A, D’Amico G, La Galla R, et al. TIPS for prevention of recurrent bleeding in patients

with cirrhosis: meta-analysis of randomized clinical trial. Radiology. 1999;212:411–21. 24. Burroughs AK, Vangeli M. Transjugular intrahepatic portosystemic shunt versus endoscopic

therapy: randomized trials for secondary prophylaxis of variceal bleeding: an updated meta-analysis. Scand J Gastroenterol. 2002;3:249–52.

25. Salerno F, Camma C, Enea A, et al. Transjugular intrahepatic portosystemic shunt for refractory ascites: a meta-analysis of individual patent data. Gastroenterology. 2007;133:825–34.

26. Patel NH, Sasadeusz KJ, Seshadri R, et al. Increase in hepatic arterial blood fl ow after tran-sjugular intrahepatic portosystemic shunt creation and its potential predictive value of postpro-cedural hepatic encephalopathy and mortality. J Vasc Interv Radiol. 2001;12:1279–84.

27. Gülberg V, Haag K, Rössle M, Gerbes AL. Hepatic arterial buffer response in patients with advanced cirrhosis. Hepatology. 2002;35:630–4.

28. Hassoun Z, Deschênes M, Lafortune M, et al. Relationship between pre-TIPS liver perfusion by the portal vein and the incidence of post-TIPS chronic hepatic encephalopathy. Am J Gastroenterol. 2001;96:1205–9.

29. Deng D, Liao MS, Qin JP, et al. Relationship between pre-TIPS hepatic hemodynamics and post-operative incidence of hepatic encephalopathy. Hepatobiliary Pancreat Dis Int. 2006;5:232–6.

30. Rössle M, Haag K, Ochs A, et al. The transjugular intrahepatic portosystemic stent-shunt procedure for variceal bleeding. N Engl J Med. 1994;330:165–71.

31. Rössle M, Ochs A, Gulberg V, et al. A comparison of paracentesis and transjugular intrahe-patic portosystemic shunting in patients with ascites. N Engl J Med. 2000;342:1701–7.

32. Rössle M, Gerbes AL. TIPS for the treatment of refractory ascites, hepatorenal syndrome and hepatic hydrothorax: a critical update. Gut. 2010;59:988–1000.

33. Haskal ZJ, Martin L, Cardella JF, Cole P, Drooz A, Grassi CJ, et al. Quality improvement guide-lines for transjugular intrahepatic portosystemic shunts. J Vasc Interv Radiol. 2001;12:131–6.

34. Rajan DK, Haskal ZJ, Clark TW. Serum bilirubin and early mortality after transjugular intrahepatic portosystemic shunts: results of a multivariate analysis. J Vasc Interv Radiol. 2002;13:155–61.

35. Peng S, Plank LD, McCall JL, et al. Body composition, muscle function, and energy expendi-ture in patients with liver cirrhosis: a comprehensive study. Am J Clin Nutr. 2007;85:1257–66.

36. Selberg O, Selberg D. Norms and correlates of bioimpedance phase angle in healthy human sub-jects, hospitalized patients, and patients with liver cirrhosis. Eur J Appl Physiol. 2002;86:509–16.

37. Trotter JF, Suhocki PV, Rockey DC. Transjugular intrahepatic portosystemic shunt (TIPS) in patients with refractory ascites: effect on body weight and Child-Pugh score. Am J Gastroenterol. 1998;93:1891–4.

38. Allard JP, Chau J, Sandokji K, et al. Effects of ascites resolution after successful TIPS on nutrition in cirrhotic patients with refractory ascites. Am J Gastroenterol. 2001;96:2442–7.

39. Plauth M, Schuetz T, Buckendahl DP, et al. Weight gain after transjugular intrahepatic porto-systemic shunt (TIPS) is associated with improvement in body composition in malnourished patients with cirrhosis and hypermetabolism. J Hepatol. 2004;40:228–33.

40. Radeleff B, Sommer CM, Heye T, et al. Acute increase in hepatic arterial fl ow during TIPS identi fi ed by intravascular fl ow measurements. Cardiovasc Intervent Radiol. 2009;32:32–7.

41. Zuchermann DA, Darsy MD, Bocchini TP, et al. Encephalopathy after transjugular intrahe-patic portosystemic shunt: correlation with hemodynamic fi ndings. Am J Roentgenol. 1997;169:1727–31.


42. Casado M, Bosch J, Garcia-Pagan JC, et al. Clinical events after transjugular intrahepatic porto-systemic shunt: correlation with hemodynamic fi ndings. Gastroenterology. 1998;114:1296–303.

43. Harrod-Kim P, Saad WE, Waldman D. Predictors of early mortality after transjugular intrahe-patic portosystemic shunt creation for the treatment of refractory ascites. J Vasc Interv Radiol. 2006;17:1605–10.

44. Rypins EB, Milne N, Sarfeh IJ. Analysis of nutrient hepatic blood fl ow after 8-mm versus 16-mm portacaval H-grafts in a prospective randomized trial. Am J Surg. 1995;169:197–201.

45. Thalheimer U, Leandro G, Samonakis DN, et al. TIPS for refractory ascites: a single centre experience. J Gastroenterol. 2009;44:1089–95.

46. Riggio O, Ridola L, Angeloni S, et al. Clinical ef fi cacy of transjugular intrahepatic portosystemic shunt created with covered stents with different diameters: results of a randomized controlled trial. J Hepatol. 2010;53:267–72.

47. Bureau C, Pagan JC, Layragues GP, et al. Patency of stents covered with polytetra fl uoroethylene in patients treated by transjugular intrahepatic portosystemic shunts: long-term results of a randomized multicenter study. Liver Int. 2007;27:742–7.

48. Rössle M, Mullen KD. Long-term patency is expected with covered TIPS stents: this effect may not always be desirable! Hepatology. 2004;40:495–7.

49. Hauenstein KH, Haag K, Ochs A, et al. The reducing stent: treatment for transjugular intrahepatic portosystemic shunt-induced refractory hepatic encephalopathy and liver failure. Radiology. 1995;194:175–9.

50. Kerlan Jr RK, LaBerge JM, Baker EL, et al. Successful reversal of hepatic encephalopathy with intentional occlusion of transjugular intrahepatic portosystemic shunts. J Vasc Interv Radiol. 1995;6:917–21.

51. Gerbes AL, Waggershauser T, Holl J, Gulberg V, Fischer G, Reiser M. Experiences with novel techniques for reduction of stent fl ow in transjugular intrahepatic portosystemic shunts. Z Gastroenterol. 1998;36:373–7.

52. Rössle M, Siegerstetter V, Berger E, et al. Epidemiology and treatment of debilitating hepatic encephalopathy after implantation of a transjugular intrahepatic portosystemic shunt. In: Yurdaydin C, Bozkaya H, editors. Advances in hepatic encephalopathy and metabolism in liver disease. Ankara: Turkish Gastroenterology Foundation, Ankara University Press; 2000. p. 411–5.

53. Riggio O, Masini A, Efrati C, et al. Pharmacological prophylaxis of hepatic encephalopathy after transjugular intrahepatic portosystemic shunt: a randomized controlled study. J Hepatol. 2005;42:674–9.


Keywords Quality of life • Health-related quality of life • Health utilities

De fi ning Quality of Life and Health-Related Quality of Life

Quality of life (QoL) is a general term for the assessment of the impact of health, social, economic, and environmental factors on an individual’s well-being. Although the de fi nition for QoL has not yet been standardized, the World Health Organization (WHO) has de fi ned QoL as “individuals’ perceptions of their position in life in the context of the culture and value systems in which they live, and in relation to their goals, expectations, standards, and concerns” [ 1, 2 ] . Other de fi nitions of QoL have included a patient’s perception of his/her ability to perform functions such as work, their cognitive capabilities, the physical effects of the illness and concomitant psycho-logical conditions (e.g., anxiety, depression, and aggressiveness), sexual problems, and the patient’s relationship with their family and healthcare providers [ 1, 3– 6 ] .

Health-related quality of life (HRQL) deals primarily with the health-related aspect of QoL [ 7 ] . In the context of chronic liver disease (CLD) and its complica-tions such as hepatic encephalopathy (HE), assessing the impact of HE and its

J. K. Price, MS Outcomes Research Program, Betty and Guy Beatty Center for Integrated Research , Inova Fairfax Hospital , Falls Church , VA , USA

Z. M. Younossi, MD, MPH (*) Beatty Liver and Obesity Research Center , Inova Fairfax Hospital , Claude Moore Education and Research Building, 3rd Floor, 3300 Gallows Road , Falls Church , VA 22042 , USA e-mail: [email protected]

Chapter 18 Quality of Life in Hepatic Encephalopathy

Jillian Kallman Price and Zobair M. Younossi

222 J.K. Price and Z.M. Younossi

treatment on patients’ HRQL are important [ 6, 7 ] . In addition, patients with HE have profound impairment of both their physical and mental aspects of HRQL, affecting HE patients’ ability for self-care and other daily activities [ 8 ] . Currently, many of the HRQL measures of impairment available in this patient population depend upon the subjective perspective and self-reporting of the patient. It is neces-sary to determine the areas of functionality and HRQL that are valued most by each patient and to address perceived symptoms or limitations impacting their QoL. HRQL can be measured both quantitatively with objective, validated, reliable measures and qualitatively. Both forms of assessment and their utility will be elaborated upon in this chapter. HRQL measures can also feed into health utility calculations, which will also be discussed.

Generic Versus Disease-Speci fi c Health-Related Quality of Life Measures and Combined/Composite Measures

Two types of HRQL measures are currently used—generic and disease speci fi c [ 5 ] . There is a growing belief that these two types of instruments measure different aspects of patients’ HRQL and are therefore considered to be complementary [ 9, 10 ] . In some recent studies, both types of HRQL measures are used to provide the full spectrum of HRQL issues.

Generic Health-Related Quality of Life Measures

Generic HRQL measures allow for the global assessment of HRQL across a wide variety of diseases. Assessment results for a generic HRQL instrument can be com-pared across diseases (e.g., in general, patients with CLD have better HRQL than patients with congestive heart failure) and are also compared with general or so-called “healthy” population norms. The limitation of generic measures is that it may not assess all issues important for a speci fi c disease (e.g., generic measures may not have a question regarding apprehension related to potential for liver failure in the future) and may not be responsive to subtle yet clinically signi fi cant changes for a speci fi c disease state over time [ 5, 11 ] . Examples of generic HRQL measures which have been used in hepatic encephalopathy studies are the Medical Outcomes Survey Short Form 36 (MOS SF-36 or SF-36), the Sickness Impact Pro fi le (SIP) and the Nottingham Health Pro fi le which will be further discussed later in this chapter (Tables 18.1 and 18.2 ).

Many generic measures of HRQL will have a series of subscales or domains measuring different global contributors to HRQL. Some have been designed to measure speci fi c symptoms tied to HRQL in great detail. Often these symptoms may be included in a generic HRQL measure, but not in the detail desired for a speci fi c disease. The addition of a symptom-speci fi c generic assessment to a test

22318 Quality of Life in Hepatic Encephalopathy

battery may be desired (e.g., self-care, confusion, emotional behavior), especially if a disease or treatment-related side effect is a common complaint or is believed to strongly impact HRQL in the population to be studied.

Disease-Speci fi c Health-Related Quality of Life Measures

Disease-speci fi c measures of HRQL are tailored to a speci fi c illness or category of illness (e.g., Chronic Liver Disease Questionnaire (CLDQ), and Liver Disease Quality of Life Questionnaire (LDQOL 1.0), National Institute of Diabetes and Digestive and Kidney Disease-QoL Assessment Questionnaire (NIDDK-QA) [ 10– 16 ] (for more detailed information on these instruments, please refer to Tables 18.1 and 18.2 ). By focusing on the unique concerns and challenges of a speci fi c disease, disease-speci fi c measures tend to be more responsive than generic instruments.

Combination Instruments

Occasionally a test will be designed to capture both generic HRQL information and disease-speci fi c information. These combination instruments such as modular instruments may have some ease in administration, and reduce the overlap of ques-tions that can occur when both generic and disease-speci fi c HRQL assessments are used. However, unless portions of the questionnaire overlap signi fi cantly or com-pletely with an existing generic measure, it is dif fi cult to compare the results to other generic measure study fi ndings. The LDQOL is a combined instrument com-prising the SF-36 plus 75 liver disease-speci fi c questions. The Hepatitis Quality of Life Questionnaire (HQLQ) is another example of disease-speci fi c questions com-bined with the SF-36 (Tables 18.1 and 18.2 ).

Table 18.1 Quality of life (QoL) measures used in hepatic encephalopathy assessment QoL measure Type of measure Total number of items

Medical Outcomes Survey Short Form 36 (SF-36)

Generic 36

Sickness Impact Pro fi le (SIP) Generic 136 Nottingham Health Pro fi le Generic 38 Chronic Liver Disease Questionnaire (CLDQ) Liver disease-speci fi c 29 National Institute of Diabetes and Digestive

and Kidney Disease-QoL Assessment Questionnaire (NIDDK-QA)

Liver disease-speci fi c 47

Hepatitis Quality-of-Life Questionnaire (HQLQ) Modular/Combination SF-36 + 15 Liver Disease Quality of Life Questionnaire

(LDQOL) Combination SF-36 + 75

Table 18.2 QoL measures: areas of measurement for domains and scales Health-related quality of life (HRQL) measure

Total number of domains/scales Domain/scale scores

Medical Outcomes Survey Short Form 36 (SF-36)

8 Physical functioning (PF) Role limitation-physical (RP) Bodily pain (BP) General health (GH) Vitality (VT) Social functioning (SF) Role limitation-emotional (RE) Mental health (MH)

Sickness Impact Pro fi le (SIP) 12 Sleep and rest Eating Work Home management Recreation and pastimes Ambulation Mobility Body care and movement Social interaction Alertness Emotional behavior Communication

Nottingham Health Pro fi le Part I: 6 Energy (Part I) Pain (Part I) Emotional reactions (Part I) Sleep (Part I) Social isolation (Part I) Physical immobility (Part I)

Part II: 1 Daily living (Part II)

Chronic Liver Disease Questionnaire (CLDQ)

6 Abdominal symptoms Activity Emotional function Fatigue Systemic symptoms Worry

National Institute of Diabetes and Digestive and Kidney Disease-QoL Assessment (NIDDK-QA)

4 Liver disease symptoms Physical function Health satisfaction Overall well-being

Liver Disease Quality-of-Life Questionnaire (LDQOL)

12 Symptoms of liver disease Effects of liver disease Concentration Memory Quality of social interaction Health distress Sleep problems Loneliness Hopelessness Stigma of liver disease Sexual functioning Sexual problems


Health Utilities and Quality of Life

Another important type of measurement related to QoL is the measurement of health utilities, and are measured on an interval scale of 0–1.0, with 0 re fl ecting states of health equivalent to death and 1 re fl ecting perfect health. In health economics, health utilities are often combined with survival estimates and aggregated across individuals to generate quality-adjusted life years (QALYs) for use in cost–utility analyses and comparison of different healthcare interventions [ 17– 20 ] . The main indirect methods of utility measurement are: the use of generic preference instru-ments (EQ-5D, SF-6D, and HUI); the use of disease-speci fi c preference measures; and mapping from a disease-speci fi c HRQL instrument to a generic instrument. The EQ-5D’s Visual Analog Scale (VAS) has been used in an HE treatment study [ 21 ] . The Health Utilities Index (HUI) has correlated strongly with global measures of QoL such as the SF-36 and has also been applied to CLD [ 22 ] . A scoring method for the SF-36, the SF-6D, has also been used to derive health utility scores, and has correlated well in a CLD population [ 23 ] . Table 18.3 contains additional informa-tion on the healthy utilities measures listed above.

Quantitative Versus Qualitative Measurement of Quality of Life

Quantitative assessment of HRQL allows us to quantify the relative impacts of hepatic encephalopathy on patient’s daily activities to evaluate the impact of speci fi c treatment strategies on a patient’s HRQL. A qualitative approach can provide deeper insights into the issues affecting HRQL in patients with hepatic encephalopathy,

Table 18.3 Health utilities measures

European Quality of Life-Visual Analog Scale (EQ-5D VAS)

Health Utilities Index (HUI)

Medical Outcomes Survey Short Form-6D (MOS SF-6D or SF-6D)

Number of items N/A 17 36 Number of scales/

domains/classi fi cations/attributes

Selection of a number between 000 and 100

HUI2 attributes: sensation, mobility, emotion, cognition, self-care, pain, fertility

Physical functioning, social functioning, mental health, vitality, pain, and role limitations

HUI3 attributes: vision, hearing, speech, ambulation, dexterity, emotion, cognition, pain

Selected citations Poo et al. [21] Younossi et al. [40] Dan et al. [41]


and explain potentially ambiguous or contradictory fi ndings of the quantitative models. Both methods can become a fi rst step in the development of reliable and valid HRQL measures tailored to speci fi c clinical populations [ 13 ] .

Chronic Liver Disease and Health-Related Quality of Life

In the recent years, QoL research has become increasingly essential to assess the impact of CLD and its treatment, not only on important clinical outcomes but also on patients’ well-being. HRQL monitoring is a vital part of the management of potential transplant patients as a tool to assist in minimizing both human and economic impacts of cirrhosis [ 24– 27 ] . Impairment of HRQL correlates strongly with severity of liver disease [ 28, 29 ] , and other complications of cirrhosis, as well as repeated hospitalization [ 25, 28– 31 ] . In fact, patients with CLD have been shown to exhibit impaired HRQL, on par with chronic obstructive pulmonary disease and congestive heart failure [ 28, 32, 33 ] . In addition, cirrhotic patients tend to present with more severe gastrointestinal symptoms than the general pop-ulation, which is associated with decreased HRQL [ 16, 34 ] . Also, patients with early cirrhosis showed better QoL as measured by the SF-36, as against those with advanced cirrhosis [ 8, 16, 29 ] . Therefore, disease severity is associated with worsening HRQL scores.

Health-Related Quality of Life in Hepatic Encephalopathy

Patients with hepatic encephalopathy have been shown to have lower HRQL than the general population [ 8, 35 ] . Using SF-36, patients with cirrhosis undergoing ini-tial screening for liver transplant candidacy, in a combined group of overt hepatic encephalopathy (excluding grade III HE and above) and minimal (as de fi ned by the Reitan trial test) hepatic encephalopathy, were found to have lower mental and physical component scores (MCS and PCS) on SF-36 than those without hepatic encephalopathy, irrespective of the Child-Pugh score. In addition, those with mini-mal hepatic encephalopathy (MHE) had worse MCS scores than patients without hepatic encephalopathy [ 8 ] . SF-36 domains most affected were role limitation-emo-tional, mental health, and social functioning [ 8 ] . An abbreviated SIP was also used in a study assessing the fl uctuating course of MHE [ 36 ] . Several other studies have also used the SIP to measure HRQL in patients with hepatic encephalopathy [ 37 ] as well as assessing HRQL in patients pre-liver transplantation with varying severities of hepatic encephalopathy [ 38 ] . In one such study, severity of hepatic encephalopa-thy prior to liver transplantation was shown to correlate with QoL post liver trans-plantation [ 38 ] . Finally, a lower HRQL score, depicting severe impairment, has been shown to predict HE recurrence [ 39 ] .


Health-Related Quality of Life and Minimal Hepatic Encephalopathy

As noted previously, a number of researchers have found signi fi cant QoL impair-ment in patients with MHE. MHE has been shown to independently impair HRQL, socio-economic status, and daily functioning in multiple studies [ 16, 29, 35, 37, 40, 41 ] . In fact, MHE can also impact the patients’ adherence to treatment which can lead to increased dependence on providers [ 7, 42 ] . Additional studies have reported that 44–50% of patients with MHE are un fi t to work or were not regularly employed, compared with 15% of patients without MHE [ 37, 43 ] . Furthermore, MHE may have a negative impact on fi tness to drive an automobile [ 19, 20, 40, 44– 47 ] . Patients with MHE showed signi fi cant impairment on 11 scales of the SIP, the psychosocial and physical subscores, and in total SIP score, particularly in social interaction, alertness, emotional behavior, sleep, work, home management, and recreation and pastimes [ 35 ] . More in-depth studies of MHE using disease-speci fi c HRQL instru-ments are currently underway.

Impact of Treatment of Hepatic Encephalopathy and Minimal Hepatic Encephalopathy on Health-Related Quality of Life

Treatment of hepatic encephalopathy can positively impact HRQL [ 21, 32, 43, 48, 49 ] . Treatment options for hepatic encephalopathy include nonabsorbable disac-charides (e.g., lactulose) [ 48 ] and nonabsorbable antibiotics (e.g., rifaximin) [ 50 ] . Although not available in the United States, l -ornithine- l -aspartate has also been used to treat HE [ 32, 43 ] . HRQL data using VAS of the EQ-5D survey for l -ornithine- l -aspartate used for treatment of HE showed signi fi cantly greater improvements than lactulose [ 21 ] . In another study using CLDQ-D, l -ornithine- l -aspartate for 8 weeks improved HRQL domain scores [ 32 ] .

The effect of nonabsorbable disaccharide, lactulose, on HRQL of cirrhotic patients with minimal HE has also been assessed [ 21, 32, 35 ] . Patients with MHE after 3 months of treatment with lactulose improved cognitive performance and showed increased HRQL as measured by the SIP [ 35 ] . Nonabsorbable disaccharide, lactulose, however, may be associated with gastrointestinal symptoms which might reduce HRQL [ 51 ] .

Finally, patients with MHE who were treated with rifaximin, a non-absorbable antibiotic, for 8 weeks have also been shown to have improvements in cognitive function and HRQL, as measured by the SIP [ 52 ] . Improvements on neuropsycho-logical tests correlated with improved HRQL. Speci fi cally, mean total SIP score showed signi fi cant improvement in the rifaximin group. A recent study found that rifaximin signi fi cantly improved HRQL in patients with cirrhosis and recurrent HE [ 39 ] . In fact, the study suggested that HRQL of patients with HE using CLDQ was profoundly impaired. After 8 weeks of treatment with Rifaximin, all domain scores


of CLDQ showed signi fi cant improvement as compared to baseline or compared to lactulose [ 39 ] . This study suggests that effective treatment of HE with this antibi-otic will not only result in reduction of recurrence of HE but also in improvement of HRQL.

Summary

It has been long suspected that symptoms of hepatic encephalopathy impair func-tioning and well-being of patients with cirrhosis in a variety of ways. Recent studies have shown that impairment of HRQL does indeed correlate strongly with both overt HE [ 8, 24, 29, 49, 53 ] and minimal HE [ 33– 35, 49, 51, 54– 56 ] . Additionally, treatment of overt and minimal HE can lead to improvement of the patients’ HRQL. Therefore, measurement of HRQL remains an important bellwether of a patient’s condition in overt hepatic encephalopathy, MHE, and CLD. The speci fi c impact on HRQL of HE and MHE versus other symptoms of liver disease and treatment side effects needs to be studied in greater detail.

References

1. Gotardo DR, Strauss E, Teixeira MC, et al. Liver transplantation and quality of life: relevance of a speci fi c liver disease questionnaire. Liver Int. 2008;28(1):99–106.

2. Orley J, Kuyken W. Quality of life assessment: international perspectives. Berlin: Springer; 1994.

3. Bergner M, Bobbitt RA, Kressel S, et al. The sickness impact pro fi le: conceptual formulation and methodology for the development of a health status measure. Int J Health Serv. 1976;6:393–415.

4. Patrick DL, Bergner M. Measurement of health status in the 1990s. Annu Rev Public Health. 1990;11:165–83.

5. World Health Organization. Study protocol for the World Health Organization project to develop a Quality of Life assessment instrument (WHOHRQL). Qual Life Res. 1993;2:153–9.

6. Younossi ZM. Chronic liver disease and health-related quality of life. Gastroenterology. 2001;120:305–7.

7. Cirrincione R, Taliani G, Caporaso N, Mele A. Quality of life assessment in chronic liver dis-ease. Hepatogastroenterology. 2002;49:813–6.

8. Arguedas MR, DeLawrence TG, McGuire BM. In fl uence of hepatic encephalopathy on health-related quality of life in patients with cirrhosis. Dig Dis Sci. 2003;48(8):1622–6.

9. Bayliss MS. Methods in outcomes research in hepatology: de fi nitions and domains of quality of life. Hepatology. 1999;29(Suppl):3s–6.

10. Martin L, Dunn A, Younossi Z. Measurement of health-related quality of life in patients with chronic liver disease. Liver Transpl. 2006;12(1):22–3.

11. Gralnek IM, Hays RD, Kilbourne A, Rosen HR, Keeffe EB, Artinian L, Kim S, Lazarovici D, Jensen DM, Busuttil RW, Martin P. Development and evaluation of the Liver Disease Quality of Life instrument in persons with advanced, chronic liver disease—the LDQOL 1.0. Am J Gastroenterol. 2000;95:3552–65.


12. Kim WR, Lindor KD, Malinchoc M, et al. Reliability and validity of the NIDDK-QA instru-ment in the assessment of quality of life in ambulatory patients with cholestatic liver disease. Hepatology. 2000;32:924–9.

13. Younossi ZM, Guyatt G, Kiwi M, et al. Development of a disease-speci fi c questionnaire to measure health-related quality of life in patients with chronic liver disease. Gut. 1999;45: 295–300.

14. Nie YZ, Zhang JX, Li XH. Evaluation of the quality of life instrument in patients with chronic liver disease. Mod Rehabil. 2001;5:18–9.

15. Gross CR, Malinchos M, Kim WR, et al. Quality of life before and after liver transplantation for cholestatic liver disease. Hepatology. 1999;29:356–64.

16. Zhou YQ, Chen SY, Jiang LD, et al. Development and evaluation of the quality of life instru-ment in chronic liver disease patients with minimal hepatic encephalopathy. J Gastroenterol Hepatol. 2009;24(3):408–15.

17. Drummond MF, Sculpher MJ, Torrance GW, O’Brien BJ, Stoddart GL. Methods for the eco-nomic evaluation of health care programmes. 3rd ed. Oxford: Oxford University Press; 2005.

18. Tolley K. What is…? Series: what are health utilities? Health Econ. 2009;2:1–8. 19. Torrance GW. Measurement of health state utilities for economic appraisal. J Health Econ.

1986;5:1–30. 20. Dhiman RK, Chawla YK. Minimal hepatic encephalopathy: should we start treating it?

Gastroenterology. 2004;127:1855–7. 21. Poo JL, Góngora J, Sánchez-Ávila F, et al. Ef fi cacy of oral L-ornithine-L-aspartate in cirrhotic

patients with hyperammonemic hepatic encephalopathy. Results of a randomized, lactulose-controlled study. Ann Hepatol. 2006;5:281–8.

22. Younossi ZM, Boparai N, McCormick M, et al. Assessment of utilities and health-related quality of life in patients with chronic liver disease. Am J Gastroenterol. 2001;96:579–83.

23. Dan A, Kallman J, Srivastava R, Younoszai Z, Kim A, Younossi Z. Health utilizing assessment using SF-6D as Health Utility Index in patients with chronic liver disease. Liver Transpl. 2008;14(3):321–6.

24. Gutteling JJ, de Man RA, Busschbach JJ, Darlington AS. Overview of research on health-related quality of life in patients with chronic liver disease. Neth J Med. 2007;65(7):227–34.

25. Younossi ZM, McCormick M, Price LL, Boparai N, Farquhar L, Henderson JM, et al. Impact of liver transplantation on health-related quality of life. Liver Transpl. 2000;6(6):779–83.

26. Kim WR, Brown Jr RS, Terrault NA, El-Serag H. Burden of liver disease in the United States: summary of a workshop. Hepatology. 2002;36(1):227–42.

27. Kanwal F, Gralnek IM, Hays RD, Zeringue A, Durazo F, Han SB, et al. Health-related quality of life predicts mortality in patients with advanced chronic liver disease. Clin Gastroenterol Hepatol. 2009;7(7):793–9.

28. Younossi ZM, Boparai N, Price LL, et al. Health-related quality of life in chronic liver disease: the impact and severity of disease. Am J Gastroenterol. 2001;96:2199–205.

29. Marchesini G, Bianchi G, Amodio P, Salerno F, Merli M, Panella C, et al. Factors associated with poor health-related quality of life of patients with cirrhosis. Gastroenterology. 2001;120(1): 170–8.

30. Leevy CB, Phillips JA. Hospitalizations during the use of rifaximin versus lactulose for the treatment of hepatic encephalopathy. Dig Dis Sci. 2007;52(3):737–41.

31. Poordad F. Review article: the burden of hepatic encephalopathy. Aliment Pharmacol Ther. 2007;25(S1):3–9.

32. Ong JP, Oehler G, Krüger-Jansen C, Lambert-Baumann J, Younossi ZM. Oral L-ornithine-L-aspartate improves health-related quality of life in cirrhostic patients with hepatic enceph-alopathy: an open-label, prospective, multicentre observational study. Clin Drug Investig. 2011;31(4):213–20.

33. Saab S, Ibrahim AB, Shpaner A, Younossi ZM, Lee C, Durazo F, et al. MELD fails to measure quality of life in liver transplant candidates. Liver Transpl. 2005;11(2):218–23.


34. Kalaitzakis E, Simren M, Olsson R, Henfridsson P, Hugosson I, Bengtsson M, et al. Gastrointestinal symptoms in patients with liver cirrhosis: associations with nutritional status and health-related quality of life. Scand J Gastroenterol. 2006;41(12):1464–72.

35. Prasad S, Dhiman RK, Duseja A, Chawla YK, Sharma A, Agarwal R. Lactulose improves cognitive functions and health-related quality of life in patients with cirrhosis who have mini-mal hepatic encephalopathy. Hepatology. 2007;45(3):549–59.

36. Tan HH, Lee GH, Thia KT, Ng HS, Chow WC, Lui HF. Minimal hepatic encephalopathy runs a fl uctuating course: results from a three-year prospective cohort follow-up study. Singapore Med J. 2009;50(3):255–60.

37. Groeneweg M, Quero JC, De Bruijn I, Hartmann IJ, Essink-bot ML, Hop WC, et al. Subclinical hepatic encephalopathy impairs daily functioning. Hepatology. 1998;28:45–9.

38. Tarter RE, Switala J, Plial J, Havrilla J, Van Thiel DH. Severity of hepatic encephalopathy before liver transplantation is associated with quality of life after transplantation. Arch Intern Med. 1992;152:2097–101.

39. Sanyal A, Younossi ZM, Bass NM, Mullen KD, Poordad F, Brown RS, Vemuru RP, Jamal M, Huang S, Merchant K, Bortey E, Forbes WP. Rifaximin treatment improved quality of life in patients with hepatic encephalopathy: results of a large, randomized, placebo-controlled trial. J Hepatol. 2011;52(S7):15.

40. Schomerus H, Hamster W. Quality of life in cirrhotics with minimal hepatic encephalopathy. Metab Brain Dis. 2001;16:37–41.

41. Quero Guillen JC, Groeneweg M, Jimenez Saenz M, et al. Is it medical error if we do not screen cirrhotic patients for minimal hepatic encephalopathy? Rev Esp Enferm Dig. 2002;94: 544–57.

42. Miyazaki ET, Dos Jr SR, Miyazaki MC, Domingos NM, Felicio HC, Rocha MF, et al. Patients on the waiting list for liver transplantation: caregiver burden and stress. Liver Transpl. 2010;16(10):1164–8.

43. Kircheis G, Wettstein M, vom Dahl S, Häussinger D. Clinical ef fi cacy of L-ornithine-L-aspartate in the management of hepatic encephalopathy. Metab Brain Dis. 2002;17:453.

44. Watanabe A, Tuchida T, Yata Y, Kuwabara Y. Evaluation of neuropsychological function in patients with liver cirrhosis with special reference to driving ability. Metab Brain Dis. 1995;10: 239–48.

45. Wein C, Koch H, Popp B, Ochler G, Schauder P. Minimal hepatic encephalopathy impairs fi tness to drive. Hepatology. 2004;39:739–45.

46. Bajaj JS, Hafeezullah M, Hoffman RG, Saeian K. Minimal hepatic encephalopathy: a vehicle for accidents and traf fi c violations. Am J Gastroenterol. 2007;103:1903–9.

47. Bajaj JS, Hafeezullah M, Hoffman RG, et al. Navigation skill impairment: another dimension of driving dif fi culties in minimal hepatic encephalopathy. Hepatology. 2008;47(2):596–604.

48. Als-Nielsen B, Gluud LL, Gluud C. Nonabsorbable disaccharides for hepatic encephalopathy (review). Cochrane Database Syst Rev. 2004;(2):CD003044. doi: 10.1002/14651858.CD003044.pub2 .

49. Les I, Doval E, Flavia M, Jacas C, Cardenas G, Esteban R, et al. Quality of life in cirrhosis is related to potentially treatable factors. Eur J Gastroenterol Hepatol. 2010;22(2):221–7.

50. Festi D, Vestito A, Mazella G, Roda E, Colecchia A. Management of hepatic encephalopathy: focus on antibiotic therapy. Digestion. 2006;73 Suppl 1:94–101.

51. Kalaitzakis E, Björnsson E. Lactulose treatment for hepatic encephalopathy, gastrointestinal symptoms, and health-related quality of life. Hepatology. 2007;466:949–50 (Letter).

52. Sidhu SS, Goyal O, Mishra BP, Sood A, Chhina RS, Soni RK. Rifaximin improves psychomet-ric performance and health-related quality of life in patients with minimal hepatic encephal-opathy (the RIME trial). Am J Gastroenterol. 2011;106(2):307–16.

53. Afendy A, Kallman JB, Stepanova M, Younoszai Z, Aquino RD, Bianchi G, et al. Predictors of health-related quality of life in patients with chronic liver disease. Aliment Pharmacol Ther. 2009;30(5):469–76.

http://dx.doi.org/10.1002/14651858.CD003044.pub2

http://dx.doi.org/10.1002/14651858.CD003044.pub2


54. Kalaitzakis E, Josefsson A, Bjornsson E. Type and etiology of liver cirrhosis are not related to the presence of hepatic encephalopathy or health-related quality of life: a cross-sectional study. BMC Gastroenterol. 2008;8:46.

55. Bao ZJ, Qiu DK, Ma X, Fan Z-P, Zhang G-S, Huang Y-Q, et al. Assessment of health-related quality of life in Chinese patients with minimal hepatic encephalopathy. World J Gastroenterol. 2007;13(21):3003–8.

56. Company L, Zapater P, Perez-Mateo M, Jover R. Extrapyramidal signs predict the develop-ment of overt hepatic encephalopathy in patients with liver cirrhosis. Eur J Gastroenterol Hepatol. 2010;22(5):519–25.


Keywords Hepatic encephalopathy • Liver transplantation • Graft allocation

Introduction

Liver transplantation (LT) is the de fi nitive treatment for end-stage liver disease and its associated complications. LT improves and in most cases reverses hepatic encephalopathy (HE). With the advent of model for end-stage liver disease (MELD), the importance of HE as a major indication for LT has decreased. As the evidence for residual effect of HE on posttransplant cognition continues to mount, we may need to devise a system which includes HE in the decision-making process for LT.

Effect of Liver Transplantation on HE

Most clinicians believe that overt HE resolves after LT. A study by Hockerstedt et al. [ 1 ] showed marked improvement in encephalopathic state of patients with overt HE after LT. Along with extending life expectancy, LT was noted to improve

D. K. Atluri , MD, MRCP (UK) (*) Department of Gastroenterology , Metrohealth Medical Center , 2500 Metrohealth Drive , Cleveland , OH 44109 , USA e-mail: [email protected]

K. D. Mullen , MD, FRCPI Division of Gastroenterology, Department of Internal Medicine , Metrohealth Medical Center , Cleveland , OH , USA

Chapter 19 Liver Transplantation and Hepatic Encephalopathy

Dileep K. Atluri and Kevin D. Mullen

234 D.K. Atluri and K.D. Mullen

quality of life (QOL) and cognitive functioning of the patients. In a prospective study by Moore et al., 32 post-LT patients were followed for 9 months after LT. Their QOL and cognitive functioning improved on successive measurements at 3, 6, and 9 months [ 2 ] . Tarter et al. noted that severity of HE is associated with post-LT improvement in QOL [ 3 ] .

Some patients with advanced neurodegeneration such as “acquired hepatocere-bral degeneration” aka “non-Wilsonian hepatolenticular degeneration” were also noted to bene fi t from LT. Case series by Stracciari, Powell, and Pinarbasi et al. have demonstrated the reversibility of this condition after LT both clinically and radio-graphically [ 4– 7 ] .

Several studies were conducted to evaluate the reversibility of minimal hepatic encephalopathy (MHE) after LT. In a study done by Tarter et al., performance of liver disease patients with a battery of neuropsychological tests improved after LT.

Fig. 19.1 Chronology of improvement in cognitive function after liver transplantation as observed in Mattarozzi study

23519 Liver Transplantation and Hepatic Encephalopathy

But, the impairments on 4 of 27 measures remained after transplantation [ 8 ] . The improvement in neuropsychiatric test performance does not appear to be uniform among the LT patients. In a study by Mechtcheriakov et al., only half of 14 patients saw improvements in their visuo-constructive performance score. They concluded that the visuo-motor de fi cits in liver disease patients resolve only in some of the patients after LT, whereas a signi fi cant number of patients show no improvement of the visuo-motor and visuo-constructive function [ 9 ] . In a larger study by Mattarozzi et al., cognitive performance was assessed in LT patients for longer intervals of up to 18 months posttransplantation [ 10 ] . In this longitudinal study, it was noted that cognitive functions such as verbal short-term memory were late to improve compared to visuo-spatial function and psychomotor speed. Their fi ndings are shown in Fig. 19.1 .

Effect of Liver Transplantation on Findings of Investigative Modalities for HE

A variety of changes are noted in brain in patients with HE. These changes include manganese deposition in basal ganglia, brain edema, and increase in intracellular concentration of glutamine and decrease in choline. These changes can be detected by magnetic resonance (MR) imaging. These changes are noted to be reversible after restoration of liver function through LT [ 11– 14 ] . They are detailed in Table 19.1 .

Glucose metabolism of brain is altered in HE patients. Decreased glucose metabolism is particularly evident in cingulate gyrus, frontal lobe, and hippocam-pus. The glucose metabolism is noted to improve signi fi cantly in these areas after LT [ 15 ] .

The abnormalities in spectral electroencephalogram (S-EEG) associated with HE are noted to improve after LT [ 16 ] .

Residual Cognitive De fi cits After Liver Transplantation

Many studies have noted persistent de fi cits in cognition of liver transplant patients. This may be attributable to various causes as detailed below.

1. Preexisting central nervous system (CNS) damage: CNS insults such as trauma, stroke, and Wernicke’s encephalopathy (WE) can lead to persistent neurological de fi cits post-LT. Prolonged alcohol use, in con-junction with thiamine de fi ciency, can lead to WE. Pathologically, WE manifests with mammillary body and thalamic lesions. In a study by Kril and Butterworth, brains of patients with autopsy proven cirrhosis were examined. WE fi ndings were discovered in 9 out of 30 alcoholic patients. But, clinical diagnosis of WE was considered only in two patients. Cerebellar degeneration was found in 17 of


Table 19.1 Changes in fi ndings of diagnostic modalities of HE with liver transplantation

Diagnostic modality Pathogenetic mechanism Before transplantation

After transplantation

PET scan Altered glucose metabolism of brain

Decreased glucose uptake in cortical and subcortical areas

Improvement in glucose uptake

MR imaging Deposition of manganese in basal ganglia

Bilateral high signal intensity of globus pallidus and substantia nigra on T1-weighted images

Decrease in hyperintensity on T1-weighted images

Accumulation of glutamine in astrocyte and osmolar adaptation of astrocyte

Increase in glutamine/glutamate signal, decrease in choline and myo-inositol signal

Reversal of osmolar adaptation changes of astrocyte

Diffuse brain edema Focal high-signal T2 lesions in subcortical hemispheric white matter on T2/FLAIR images

Decrease in white matter lesions

Interstitial brain edema Increase in mean diffusivity in hemispheric white matter

Reversal of this change

S-EEG Cerebral bioelectric alterations

Low MDF (mean dominant frequency) and low LogR (LogR _ log10 occipital alpha-theta ratio) (<0.13)

Signi fi cant increase in MDF and LogR

30 patients [ 17 ] . This demonstrates the possibility of clinically unidenti fi ed WE and cerebellar degeneration from alcohol abuse accounting for part of the post-LT cognitive de fi cits.

2. Intraoperative injury to brain: Given the complexity and prolonged nature of the LT procedure, many CNS insults may occur. Changes in cerebral perfusion pressure and hypotension may lead to ischemic event. Air embolism, embolic stroke, and cerebral hemorrhage can also lead to lasting injury to brain [ 18 ] .

3. Persistence of porto-systemic collaterals: Porto-systemic shunts may persist after LT. Although HE is uncommon due to collaterals in a patient with normally functioning graft, exceptions do exist. In a case report by Herrero et al., recurrent bouts of HE were observed after a suc-cessful LT with normally functioning graft. This was attributed to collaterals in the retroperitoneum based on abdominal angiography. After successful embo-lization of these collaterals, HE did not recur [ 19 ] .

4. CNS toxicity of immunosuppressant drugs: Immunosuppressive agents such as tacrolimus and cyclosporine are used after LT as antirejection drugs. They act by inhibiting T lymphocytes. They also have neuropsychiatric complications such as diffuse encephalopathy, cerebellar disor-ders, and posterior leukoencephalopathy [ 20 ] .


5. Residual effects of prior bouts of overt HE: The effect of overt HE prior to LT on post-LT neurological outcomes was studied by Sotil et al. Although this study was limited by small cohort and possible selec-tion bias, authors suggested the possibility of overt HE having lasting effects on the neurological outcome of the LT [ 20 ] .

Importance of HE on Transplant Outcomes

HE is known to affect posttransplant outcomes such as neurological recovery, survival, and QOL. In a study by Bajaj et al., effect of recurrent bouts of HE on cognition was assessed. They concluded that episodes of overt HE are associated with persistent and cumulative de fi cits in working memory, response inhibition, and learning. It was also noted that the number of OHE hospitalizations correlated with severity of residual impairment [ 21 ] .

Patients with HE at time of listing have decreased 3- and 12-month posttrans-plant survival compared to their counterparts without HE [ 22 ] .

Apart from having possible residual neurological effect post-LT, HE is also noted to be an independent risk factor for the early calcineurin inhibitor-induced neuro-toxicity (ECIIN) after LT [ 23 ] . Acute graft rejection and infections were more frequent in the ECIIN patients.

Should Hepatic Encephalopathy Be Given Greater Consideration in Transplant Allocation?

LT is recognized as an effective treatment for advanced liver disease and the demand for organs has been steadily going up. But the supply of the organs could not keep pace with the demand. With this demand–supply mismatch, it becomes imperative to allocate the organs to the recipients most in need. MELD was introduced as an objective and reliable predictor of short-term mortality in liver disease patients. This scale is also used currently to assign priority to liver disease patients for organ allocation. It is based on objective data such as serum bilirubin, creatinine, and international normalized ratio (INR). MELD has not assigned HE any extra points. MELD exception study group and conference 2006 (MESSAGE) did not recom-mend any automatic increase in priority due to HE. They suggested case-by-case assessments and priority to patients in coma needing endotracheal intubation and/or increased intracranial pressures [ 24, 25 ] .

As new evidence for effect of HE on transplant outcomes continues to build, it becomes necessary to explore ways in which HE can be given higher priority in transplant allocation.


Conclusion

LT has evolved from experimental procedure to accepted treatment modality for advanced chronic or fulminant liver failure. LT treats a variety of complications of liver failure including HE. Overt HE is known to improve after LT, whereas the improvement in MHE appears to be nonhomogenous, dynamic, and at times incomplete. There are a range of possible reasons for persistent cognitive de fi cits after LT. Possible lasting effect of overt HE on brain is one of them. Overt HE is also known to affect the post-LT survival, QOL, and modulate ECIIN. As detri-mental effects of overt HE on transplant outcomes become more apparent, more emphasis might need to be given for early transplantation in these patients.

References

1. Hockerstedt K, Kajaste S, Isoniemi H, Muuronen A, Raininko R, Seppalainen AM, et al. Tests for encephalopathy before and after liver transplantation. Transplant Proc. 1990;22(4):1576–8.

2. Moore KA, McL Jones R, Burrows GD. Quality of life and cognitive function of liver trans-plant patients: a prospective study. Liver Transpl. 2000;6(5):633–42.

3. Tarter RE, Switala J, Plail J, Havrilla J, Van Thiel DH. Severity of hepatic encephalopathy before liver transplantation is associated with quality of life after transplantation. Arch Intern Med. 1992;152(10):2097–101.

4. Stracciari A, Guarino M, Pazzaglia P, Marchesini G, Pisi P. Acquired hepatocerebral degenera-tion: full recovery after liver transplantation. J Neurol Neurosurg Psychiatry. 2001;70(1):136–7.

5. Stracciari A, Baldin E, Cretella L, Delaj L, D’Alessandro R, Guarino M. Chronic acquired hepatocerebral degeneration: effects of liver transplantation on neurological manifestations. Neurol Sci. 2011;32(3):411–5.

6. Powell EE, Pender MP, Chalk JB, Parkin PJ, Strong R, Lynch S, et al. Improvement in chronic hepatocerebral degeneration following liver transplantation. Gastroenterology. 1990;98(4):1079–82.

7. Pinarbasi B, Kaymakoglu S, Matur Z, Akyuz F, Demir K, Besisik F, et al. Are acquired hepa-tocerebral degeneration and hepatic myelopathy reversible? J Clin Gastroenterol. 2009;43(2):176–81.

8. Tarter RE, Switala JA, Arria A, Plail J, Van Thiel DH. Subclinical hepatic encephalopathy. Comparison before and after orthotopic liver transplantation. Transplantation. 1990;50(4):632–7.

9. Mechtcheriakov S, Graziadei IW, Mattedi M, Bodner T, Kugener A, Hinterhuber HH, et al. Incomplete improvement of visuo-motor de fi cits in patients with minimal hepatic encephal-opathy after liver transplantation. Liver Transpl. 2004;10(1):77–83.

10. Mattarozzi K, Stracciari A, Vignatelli L, D’Alessandro R, Morelli MC, Guarino M. Minimal hepatic encephalopathy: longitudinal effects of liver transplantation. Arch Neurol. 2004;61(2):242–7.

11. Thomas MA, Huda A, Guze B, Curran J, Bugbee M, Fairbanks L, et al. Cerebral 1H MR spectroscopy and neuropsychologic status of patients with hepatic encephalopathy. AJR Am J Roentgenol. 1998;171(4):1123–30.

12. Rovira A, Minguez B, Aymerich FX, Jacas C, Huerga E, Cordoba J, et al. Decreased white matter lesion volume and improved cognitive function after liver transplantation. Hepatology. 2007;46(5):1485–90.


13. Pujol J, Kulisevsky J, Moreno A, Deus J, Alonso J, Balanzo J, et al. Neurospectroscopic altera-tions and globus pallidus hyperintensity as related magnetic resonance markers of reversible hepatic encephalopathy. Neurology. 1996;47(6):1526–30.

14. Chavarria L, Alonso J, Garcia-Martinez R, Aymerich FX, Huerga E, Jacas C, et al. Biexponential analysis of diffusion-tensor imaging of the brain in patients with cirrhosis before and after liver transplantation. AJNR Am J Neuroradiol. 2011;32(8):1510–7.

15. Senzolo M, Pizzolato G, Ferronato C, Chierichetti F, Boccagni P, Dam M, et al. Long-term evaluation of cognitive function and cerebral metabolism in liver transplanted patients. Transplant Proc. 2009;41(4):1295–6.

16. Ciancio A, Marchet A, Saracco G, Carucci P, Lavezzo B, Leotta D, et al. Spectral electroen-cephalogram analysis in hepatic encephalopathy and liver transplantation. Liver Transpl. 2002;8(7):630–5.

17. Kril JJ, Butterworth RF. Diencephalic and cerebellar pathology in alcoholic and nonalcoholic patients with end-stage liver disease. Hepatology. 1997;26(4):837–41.

18. Stracciari A, Guarino M. Neuropsychiatric complications of liver transplantation. Metab Brain Dis. 2001;16(1–2):3–11.

19. Herrero JI, Bilbao JI, Diaz ML, Alegre F, Inarrairaegui M, Pardo F, et al. Hepatic encephalopa-thy after liver transplantation in a patient with a normally functioning graft: treatment with embolization of portosystemic collaterals. Liver Transpl. 2009;15(1):111–4.

20. Sotil EU, Gottstein J, Ayala E, Randolph C, Blei AT. Impact of preoperative overt hepatic encephalopathy on neurocognitive function after liver transplantation. Liver Transpl. 2009;15(2):184–92.

21. Bajaj JS, Schubert CM, Heuman DM, Wade JB, Gibson DP, Topaz A, et al. Persistence of cognitive impairment after resolution of overt hepatic encephalopathy. Gastroenterology. 2010;138(7):2332–40.

22. Bajaj JS, Saeian K. MELD score does not discriminate against patients with hepatic encephal-opathy. Dig Dis Sci. 2005;50(4):753–6.

23. Balderramo D, Prieto J, Cardenas A, Navasa M. Hepatic encephalopathy and post-transplant hyponatremia predict early calcineurin inhibitor-induced neurotoxicity after liver transplanta-tion. Transpl Int. 2011;24(8):812–9.

24. Ham J, Gish RG, Mullen K. Model for end-stage liver disease (MELD) exception for hepatic encephalopathy. Liver Transpl. 2006;12(12 Suppl 3):S102–4.

25. Freeman Jr RB, Gish RG, Harper A, Davis GL, Vierling J, Lieblein L, et al. Model for end-stage liver disease (MELD) exception guidelines: results and recommendations from the MELD Exception Study Group and Conference (MESSAGE) for the approval of patients who need liver transplantation with diseases not considered by the standard MELD formula. Liver Transpl. 2006;12(12 Suppl 3):S128–36.


Keywords Covert hepatic encephalopathy • Rifaximin • Psychometric tests • Liver transplantation

One of the major trends we predict for the future is a totally different focus for hepatic encephalopathy (HE) treatment. Formerly, all trials of new therapeutic agents for the treatment of HE were performed in patients with overt HE. Since most of these patients had advanced liver disease and at times multiple precipitating events for episodes of HE, it was not possible to perform randomized controlled clinical trials in these patients. This may explain why no new drug was approved for the treatment of HE in 30 years [ 1 ] . These days minimal or covert HE can be reliably detected and quanti fi ed [ 2, 3 ] . It is generally seen earlier in the course of liver disease when precipitating factors are relatively rare. Accordingly, new therapeutic agents will be tested for ef fi cacy in this population of HE patients.

The total emphasis on overt HE has shifted towards covert HE based on the growing knowledge of the impact of covert HE. Patients meeting the criteria for covert HE (generally by psychometric test scores) have been shown to have (1) decreased quality of life; (2) reduced driving skills; (3) less chance of being employed; and (4) high probability (60%) of developing overt HE without 18 months [ 4– 9 ] . Treatment of covert HE has already been shown to improve/normal-ize psychometric test scores, driving capacity, and quality of life [ 10– 12 ] . Future studies will determine if overt HE can be postponed or, even more tantalizingly, prevented!!!

In future, another trend in HE will be genetic markers for susceptibility to developing HE. Not all patients with cirrhosis develop overt HE. Why does one patient get


Chapter 20 Future of Hepatic Encephalopathy



HE at the same level of liver dysfunction as another patient who is free of HE? The recent discovery of the importance of the pro fi le of glutaminase gene inheri-tance in modulating the expression of overt HE has provoked great interest [ 13 ] . The enzymes were known in the early to mid-1950s as a potential mediator of the therapeutic action of neomycin [ 14 ] . Inhibition of intestinal glutaminase enzyme activity was proposed to reduce portal vein ammonia levels [ 15 ] . Now we have its potential role in permitting the appearance of overt HE being identi fi ed. In the near future more genetic markers of susceptibility to express or protect from HE will be identi fi ed. This will considerably modify how we manage cirrhotic patients in the decades to come.

Another new development still requiring more veri fi cation is the concept that overt HE episodes may be associated with less than full recovery to normal brain function [ 16 ] . If this is veri fi ed, liver transplantation may be moved up in cirrhotics to precede the development of overt HE especially in patients with genetic predis-position to develop overt HE. Short-term data after bouts of overt HE have shown “delayed” recovery from bouts of overt HE. These have been identi fi ed with either speci fi c psychometric tests or the inhibitory control test. The question still remains whether more effective or aggressive therapy over time will reverse these de fi cits more fully. Even after successful liver transplantation there are concerns that certain domains of neurological function will never return to complete normality [ 17 ] . Whether brain atrophy so commonly seen in cirrhotics reverses after liver transplan-tation should be resolved in the next few years.

Future treatments of HE will include more effective agents for lowering ammonia in the blood. New glutaminase inhibitors are already being developed and tested. Probiotic agents plus laxatives seem likely to be piloted as a therapy for covert HE in the coming years [ 18 ] . Perhaps the most promising agents are antibiotics with prominent anaerobic activity. Ever since metronidazole was noted to potentially have ef fi cacy in treating HE, antibiotics with anaerobic coverage have been tested for ef fi cacy in treating HE. Nitazoxanide and Rifaximin may be the fi rst in a line of agents to treat HE [ 10, 19 ] . Compounds that provide alternatives to urea for the excretion of ammonia will continue to be tested and developed [ 20 ] . The agents being tested will do so in patients with covert rather than overt HE because placebo-controlled trials can be utilized in this patient population.

In summary, the future of HE therapeutic interventions will be greatly enhanced by enrollment of covert HE patients. We have the ability to detect and quantify this earlier form of HE. Randomized placebo-controlled trials will be the norm for initial testing of agents for the ef fi cacy in controlling or preventing HE. Truly, these are exciting times for the development of new therapeutic agents for the treat-ment of HE. A key to this new testing paradigm is agreement on computerized psychometric testing systems that are widely available and validated as measures of covert HE.

24320 Future of Hepatic Encephalopathy

References

1. Mullen KD, Amodio P, Morgan MY. Therapeutic studies in hepatic encephalopathy. Metab Brain Dis. 2007;22(3–4):407–23.

2. Montgomery JY, Bajaj JS. Advances in the evaluation and management of minimal hepatic encephalopathy. Curr Gastroenterol Rep. 2011;13(1):26–33.

3. Bajaj JS, Cordoba J, Mullen KD, Amodio P, Shawcross DL, Butterworth RF, et al. Review article: the design of clinical trials in hepatic encephalopathy–an International Society for Hepatic Encephalopathy and Nitrogen Metabolism (ISHEN) consensus statement. Aliment Pharmacol Ther. 2011;33(7):739–47.

4. Groeneweg M, Quero JC, De Bruijn I, Hartmann IJ, Essink-bot ML, Hop WC, et al. Subclinical hepatic encephalopathy impairs daily functioning. Hepatology. 1998;28(1):45–9.

5. Bao ZJ, Qiu DK, Ma X, Fan ZP, Zhang GS, Huang YQ, et al. Assessment of health-related quality of life in Chinese patients with minimal hepatic encephalopathy. World J Gastroenterol. 2007;13(21):3003–8.

6. Bajaj JS, Saeian K, Schubert CM, Hafeezullah M, Franco J, Varma RR, et al. Minimal hepatic encephalopathy is associated with motor vehicle crashes: the reality beyond the driving test. Hepatology. 2009;50(4):1175–83.

7. Kircheis G, Knoche A, Hilger N, Manhart F, Schnitzler A, Schulze H, et al. Hepatic encephalopathy and fi tness to drive. Gastroenterology. 2009;137(5):1706–15.e1-9.

8. Bajaj JS. Minimal hepatic encephalopathy matters in daily life. World J Gastroenterol. 2008;14(23):3609–15.

9. Hartmann IJ, Groeneweg M, Quero JC, Beijeman SJ, de Man RA, Hop WC, et al. The prognostic signi fi cance of subclinical hepatic encephalopathy. Am J Gastroenterol. 2000;95(8):2029–34.

10. Mullen K, Prakash R. Rifaximin for the treatment of hepatic encephalopathy. Expert Rev Gastroenterol Hepatol. 2010;4(6):665–77.

11. Sidhu SS, Goyal O, Mishra BP, Sood A, Chhina RS, Soni RK. Rifaximin improves psychometric performance and health-related quality of life in patients with minimal hepatic encephalopathy (the RIME Trial). Am J Gastroenterol. 2011;106(2):307–16.

12. Bajaj JS, Heuman DM, Wade JB, Gibson DP, Saeian K, Wegelin JA, et al. Rifaximin improves driving simulator performance in a randomized trial of patients with minimal hepatic enceph-alopathy. Gastroenterology. 2011;140(2):478–87.e1.

13. Romero-Gomez M, Jover M, Del Campo JA, Royo JL, Hoyas E, Galan JJ, et al. Variations in the promoter region of the glutaminase gene and the development of hepatic encephalopathy in patients with cirrhosis: a cohort study. Ann Intern Med. 2010;153(5):281–8.

14. Hawkins RA, Jessy J, Mans AM, Chedid A, DeJoseph MR. Neomycin reduces the intestinal production of ammonia from glutamine. Adv Exp Med Biol. 1994;368:125–34.

15. Weber Jr FL, Veach GL. The importance of the small intestine in gut ammonium production in the fasting dog. Gastroenterology. 1979;77(2):235–40.

16. Bajaj JS, Schubert CM, Heuman DM, Wade JB, Gibson DP, Topaz A, et al. Persistence of cognitive impairment after resolution of overt hepatic encephalopathy. Gastroenterology. 2010;138(7):2332–40.

17. Garcia-Martinez R, Rovira A, Alonso J, Jacas C, Simon-Talero M, Chavarria L, et al. Hepatic encephalopathy is associated with posttransplant cognitive function and brain volume. Liver Transpl. 2011;17(1):38–46.

18. Shukla S, Shukla A, Mehboob S, Guha S. Meta-analysis: the effects of gut fl ora modulation using prebiotics, probiotics and synbiotics on minimal hepatic encephalopathy. Aliment Pharmacol Ther. 2011;33(6):662–71.

19. Al Sibae MR, McGuire BM. Current trends in the treatment of hepatic encephalopathy. Ther Clin Risk Manag. 2009;5(3):617–26.

20. Romero-Gomez M. Pharmacotherapy of hepatic encephalopathy in cirrhosis. Expert Opin Pharmacother. 2010;11(8):1317–27.

245K.D. Mullen and R.K. Prakash (eds.), Hepatic Encephalopathy, Clinical Gastroenterology,DOI 10.1007/978-1-61779-836-8, © Springer Science+Business Media, LLC 2012

A Acquired hepatocerebral degeneration

(AHD) , 100 Acute liver failure (ALF)

Alzheimer type II astrocytosis , 20, 21 blood–brain barrier , 40 brain edema , 9, 169 CBF , 9 death of patients , 9 electron micrograph of cerebral cortex , 21 ICP , 12 infection vs. in fl ammation , 36–37 microglial activation , 22, 23 OX-42 immunohistochemistry , 22, 23 proin fl ammatory cytokine , 38 systemic immune dysfunction , 39

ADMA. See Asymmetric dimethylarginine (ADMA)

AHD. See Acquired hepatocerebral degeneration (AHD)

ALF. See Acute liver failure (ALF) American Medical Association (AMA) , 194 Ammonia

ADMA in fl ammation pathway , 170–171 amino acid neurotransmitter systems , 12 blood ammonia levels , 8 blood ammonia-reducing therapies , 10 brain function

astrocytic swelling , 11–12 neurotransmitter imbalance , 12–14

brain imaging , 125 brain swelling , 142 CBF , 9

cerebral edema , 9 cognitive and motor functions , 10 cytokines, nitric oxide , 170–171 free radical production , 51 in fl ammation , 38–39 interorgan metabolism , 166–167, 203 metabolism of , 54 ornithine phenylacetate , 168–169 vs. proin fl ammatory mechanisms , 24–25

Antibiotic treatment data , 161–163 mechanism of action , 160, 161 treatment , 162

Antioxidants , 60–61 Aquaporin-4 (AQP4) , 59 Asymmetric dimethylarginine

(ADMA) , 170–171

B BBB. See Blood–brain barrier (BBB) BCAA. See Branched-chain amino acids

(BCAA) Benzodiazepine (BZ) receptor ligands

agonists and antagonist , 74, 85 in animals and humans , 76–77 concentration–response curves , 85 fl umazenil

controlled studies of , 81–82 ef fi cacy of , 79, 83 FHF , 82, 83 1,4-imidazobenzodiazepine , 79 observations , 84

Index

246 Index

Benzodiazepine (BZ) receptor ligands (cont.) plasma clearance , 79 positron emission tomography , 79 traditional approaches , 82 uncontrolled studies of , 80–81

GABA-mediated inhibitory neurotransmission

GABAA/benzodiazepine receptor complex , 71–72

intrinsic activities of , 72–74 measurements of , 75–76 nomenclature of , 77–78 Ro 14-7437 , 84, 85 Ro 15-4513 and Ro 15-3505 , 74, 85 role for

antagonism , 73–75 GABAergic tone , 73

sources of , 78 Blood–brain barrier (BBB) , 8, 9, 11

acute and chronic liver failure , 40 infection , 37

Brain edema astrocytic swelling , 11–12 brain imaging , 125 development of , 9 and motor-evoked potentials , 169–170 role of glutamine , 12

Brain imaging ammonia , 125 brain atrophy , 125 brain edema , 125 brain size , 132 FLAIR

diffusion-weighted imaging , 131–132 T2-weighted lesions , 130, 131

functional studies magnetic resonance , 133 nuclear imaging techniques , 133–134

1 H-MR spectroscopy, metabolites , 127–129

magnetic resonance brain water , 129 T1 high signal intensity , 126–127

manganese accumulation , 124 Branched-chain amino acids (BCAA) , 207 BZ receptor ligands. See Benzodiazepine

(BZ) receptor ligands

C CBF. See Cerebral blood fl ow (CBF) CDR. See Cognitive drug research (CDR)

Central nervous system (CNS) , 19 damage , 235, 236 toxicity of , 236

Cerebral blood fl ow (CBF) , 9 CFF. See Critical fl icker frequency (CFF) cGMP. See Cyclic guanosine monophosphate

(cGMP) Chronic liver failure

blood–brain barrier , 40 infection vs. in fl ammation , 36–37 MR images , 127 systemic immune dysfunction , 39

Chronic subdural hematoma , 98–99 Cirrhosis

neuroin fl ammation , 23–24 protein-calorie malnutrition , 200–202 sleep disorders

sleep regulation , 179, 181, 182 sleep–wake abnormalities , 183–184

CNS. See Central nervous system (CNS) Cognitive drug research (CDR) , 107, 108 Covert hepatic encephalopathy , 1–3

cognitive dysfunction , 110 diagnosis of , 105 neurophysiological testing , 108–109 neuropsychological testing , 105, 108 trials , 110–111

Critical fl icker frequency (CFF) , 107, 109, 212, 214

Cyclic guanosine monophosphate (cGMP) excess of nitric oxide , 11 impairment of cognitive functions , 10 reduction of , 13

D Diet , 202, 204–205 Disaccharides

antimicrobial agents , 146, 148 lactulose and lactitol

minimal hepatic encephalopathy , 144–145

overt hepatic encephalopathy , 144 treatment , 146, 147

mechanism of action , 142–143 vs. other therapy , 150–152, 154 primary prophylaxis , 151 rifaximin , 148, 150 secondary prophylaxis, 151

Driving crashes , 188 driving impairment

247Index

on-road driving studies , 189–190 simulation studies , 190–191

minimal hepatic encephalopathy challenges , 191–192 cognitive examinations , 189 fi tness , 193–194 legal rami fi cations , 193–194

motor vehicles , 191 real-life driving outcomes , 191 skills , 188 and society , 188 traf fi c violations , 191

E ECs. See Endothelial cells (ECs) Electroencephalogram (EEG) , 100, 108

classi fi cation of , 117 clinical information , 116–119 clinical scenario , 114–115 cognitive tasks , 119–120 EEG patterns , 115 objective quanti fi cation , 116, 117 P300 , 119 principles of , 113–114 quantitative assessment , 114 spectral analysis , 116–118 triphasic waves , 115–117, 119

Electron transport chain (ETC) , 53 Endothelial cells (ECs) , 57–58 Enteral nutrition (EN) , 206 ETC. See Electron transport chain (ETC) Extrapyramidal signs (EPS) , 110

F Fast fl uid-attenuated inversion recovery

(FLAIR) diffusion-weighted imaging , 131–132 T2-weighted lesions , 130, 131

Flumazenil controlled studies of

animal models of , 81–82 patients with HE , 82

ef fi cacy of , 79 FHF , 82, 83 1,4-imidazobenzodiazepine , 79 observations , 84 plasma clearance , 79 positron emission tomography , 79 traditional approaches , 82 uncontrolled studies of

doses of , 80 patients with HE , 80–81

Fulminant hepatic failure (FHF) , 77, 80–83 Functional magnetic resonance imaging

(fMRI) , 133

G Gamma-aminobutyric acid (GABA)

BZ receptor ligands GABAA/benzodiazepine receptor

complex , 71–72 intrinsic activities of , 72–73

hyperammonemia , 13 Glutaminase (GA) , 166, 169 Glutamine/glutamate (Glx) , 127–128 Glutamine synthetase (GS) , 166–169 Glutathione (GSH) , 51

H HE. See Hepatic encephalopathy (HE) Health-related quality of life (HRQL)

chronic liver disease , 226 de fi nition , 221–222 disease-speci fi c measures , 223 domains and scales , 224 generic , 222–224 hepatic encephalopathy , 226 impact of treatment , 227–228 minimal hepatic

encephalopathy , 227 Health utilities index (HUI) , 225 Hemeoxygenase-1(HO-1) , 49 Hepatic encephalopathy (HE)

cirrhotic patients , 10 covert , 1–3, 241, 242 ISHEN , 1–2 liver transplantation , 242 nomenclature and classi fi cation , 1–3 overt , 3 psychometric test , 241, 242 rifaximin , 242 symptoms of , 97, 98 terminology , 1–3 West Haven criteria , 103, 104

Hepatic myelopathy (HM) , 98, 101 HO-1. See Hemeoxygenase-1(HO-1) HRQL. See Health-related quality

of life (HRQL) HUI. See Health utilities index (HUI) Hyperammonemia

accumulation of glutamine , 142 CBF , 9 glutamate exocytosis , 13 in vivo model , 11

248 Index

I Inducible nitric oxide synthase

(iNOS) , 50, 51, 53 Infection

ammonia , 38–39 blood–brain barrier , 37 hepatic encephalopathy , 38 vs. in fl ammation , 36–37

In fl ammation ammonia , 38–39 blood–brain barrier , 37 and hepatic encephalopathy

immune dysfunction and oxidative stress , 39–40

role of , 38 treatment of , 40–42

infection vs. , 36–37 pathogenesis of ALF , 57

Inhibitory control test (ICT) , 105, 107, 108 International Society for Hepatic Encephalopathy

and Nitrogen (ISHEN) , 1–2, 105, 110 Intracellular calcium , 52 Intracranial pressure (ICP) , 9, 12, 165

L Lactulose , 159, 162

antimicrobial agents , 146, 148 vs. lactitol

minimal hepatic encephalopathy , 144–145

overt hepatic encephalopathy , 144 treatment , 146, 147

vs. neomycin , 148 rifaximin , 148, 150

Lipopolysaccharide (LPS) , 25 Liver transplantation

CNS , 235, 236 cognitive function , 234 effect of , 233–235 immunosuppressant drugs , 236 intraoperative injury , 236 investigative modalities , 235, 236 porto-systemic collaterals , 236 residual cognitive de fi cits , 235–237 transplant allocation , 237 transplant outcomes , 237

L -ornithine L -aspartate (LOLA) , 166–168 LPS. See Lipopolysaccharide (LPS)

M Magnetic resonance imaging (MRI) , 99, 100 Magnetic resonance spectroscopy (MRS) , 99 Magnetization transfer (MT) imaging , 129

Malnutrition , 202–203 Matrix metalloproteinase 9 (MMP-9) , 9 MELD. See Model for end-stage liver disease

(MELD) Metabotropic glutamate receptor

(mGluR) activity , 10 Minimal hepatic encephalopathy

(MHE) , 166 cognitive dysfunction , 110 diagnostic methods , 105–107 driving

challenges , 191–192 cognitive examinations , 189 fi tness , 193–194 legal rami fi cations , 193–194 studies and results of , 190

health-related quality of life , 227 neurophysiological testing , 108–109 neuropsychological testing , 105, 108 nonabsorbable disaccharides , 144–145 physical symptoms of , 169 presence and severity of , 24 psychometric tests , 106–107 trials , 110–111

Mitochondrial permeability transition , 52–53 Model for end-stage liver disease

(MELD) , 237 Motor-evoked potentials (MEP) , 169–170 MRI. See Magnetic resonance

imaging (MRI) MRS. See Magnetic resonance

spectroscopy (MRS)

N Natriuretic peptide clearance receptor

(NPR-C) , 11 Natriuretic peptides (NPs) , 11 Neomycin , 148, 159, 160, 162 Neuroin fl ammation

ALF , 21–23 ammonia vs. proin fl ammatory

mechanisms , 24–25 cirrhosis , 23–24 CNS complications

allopregnanolone , 27, 28 diagnostic and therapeutic

implications , 28–31 glial pathology in liver failure , 20–21 liver–brain proin fl ammatory

signaling , 25–26 Neurotransmitter imbalance

GABAergic transmission , 13 glutamatergic transmission , 13 serotoninergic transmission , 14

249Index

Neutrophils , 36, 39, 40 Nitrative stress

astrocyte cultures , 50–51 experimental animals , 49–50

Nitric oxide (NO) , 11 N -methyl D -aspartate (NMDA)

receptors , 13, 53–54 NPR-C. See Natriuretic peptide clearance

receptor (NPR-C) NPs. See Natriuretic peptides (NPs) Nuclear factor-kappa B (NF- K B) , 53 Nutrition

diet , 202, 204–205 energy and protein intake , 206 feeding and physician prescriptions , 205 guidelines , 205–207 liver cirrhosis , 203, 206 malnutrition , 202–203 protein-calorie malnutrition , 200–202

O OHE. See Overt hepatic encephalopathy (OHE) ONS. See Oxidative/nitrative stress (ONS) Ornithine phenylacetate (OP)

blood ammonia , 10 LOLA , 167, 168 mechanism of action

ADMA in fl ammation pathway , 170–171 ammonia metabolism enzymes , 168–169 brain edema and motor-evoked

potentials , 169–170 cytokines, nitric oxide , 170–171 NF K B , 170

Overt hepatic encephalopathy (OHE) , 3 chronic progressive HE , 100–101 diagnostic approach

biochemical analysis , 98 brain imaging , 98–99 electroencephalogram , 100 lumbar puncture , 99

nonabsorbable disaccharides , 144 Oxidative/nitrative stress (ONS)

antioxidants , 60–61 in astrocyte cultures

ammonia , 51 GSH level , 51 time-dependent changes , 51

cellular sources of free radicals endothelial cells , 57–58 microglia , 57

consequences of astrocyte swelling/brain edema , 58–59 neurobehavioral defects , 60

in experimental animals

Alzheimer typeII astrocytes , 48 nitric oxide production , 50 protein tyrosine nitration , 50 thioacetamide-treated rats , 49, 50

in humans , 51–52 mechanisms of

electron transport chain , 53 glutamine , 54–55 in fl ammation , 57 intracellular calcium , 52 manganese , 56 mitochondrial permeability transition ,

52–53 NMDA receptors , 53–54 nuclear factor-kappa B , 53 peripheral benzodiazepine receptor ,

55–56 Oxidative stress

astrocyte cultures , 50–51 experimental animals , 48–49 humans , 51–52

P Parenteral nutrition (PN) , 206 Parkinson’s disease (PD) , 100 Peripheral benzodiazepine receptor

(PBR) , 55–56 PET. See Positron emission tomography (PET) P300 event-related potential (P300ERP) , 109 PN. See Parenteral nutrition (PN) Portacaval anastomosis (PCA) , 170 Positron emission tomography (PET)

ammonia , 125 cerebral ammonia metabolism , 133 oxygen consumption , 133 quantitative data , 133

Protein-calorie malnutrition (PCM) , 200–202 Psychometric hepatic encephalopathy score

(PHES) , 105

Q Quality of life (QoL)

chronic liver disease , 226 combination instruments , 223–224 de fi nition , 221–222 disease-speci fi c HRQL , 223 domains and scales , 224 generic HRQL , 222–224 health utilities , 225 impact of treatment , 227–228 minimal hepatic encephalopathy , 227 quantitative versus qualitative

measurement , 225, 226

250 Index

R Reactive oxygen and nitrogen species

(RONS) , 11, 12, 52, 59 Reactive oxygen species (ROS) , 51 Repeatable battery for the assessment of

neuropsychological status (RBANS) , 105, 106

Rifaximin , 148, 150, 161, 162

S Serotoninergic transmission , 14 Single-photon emission computed tomography

(SPECT) , 133, 134 Sleep disorders

circadian rhythm , 182 cirrhosis

sleep regulation , 179, 181, 182 sleep–wake abnormalities , 183–184

daytime sleepiness , 179 delayed sleep timing , 178 diurnal preference , 178 melatonin , 180–182 night sleep disturbance , 177–178 physiological sleep regulation , 179–181 sleep quality , 178

Small bowel bacterial overgrowth (SBO) , 160, 161

Smooth pursuit eye movements (SPEM) , 109

Somatosensory evoked potentials (SEPs) , 109

SPECT. See Single-photon emission computed tomography (SPECT)

Spectral electroencephalogram (S-EEG) , 235, 236

Systemic in fl ammatory response syndrome (SIRS) , 23, 36, 37

T Toll-like receptors (TLRs) , 39, 42 Transjugular intrahepatic portosystemic

shunt (TIPS) , 151, 153 assessment and incidence , 212–213 portal hepatic blood fl ow , 216 prediction of HE , 213–215 secondary factors , 214 shunt-induced HE , 217

18-kDa Translocator protein (TSPO) , 55, 56

V Visual analog scale (VAS) , 225 Visual evoked potentials (VEPs) , 107–109

W Wernicke’s encephalopathy (WE) , 99, 235 Western blot analysis

oxidized proteins , 49 protein tyrosine nitration , 50

World Gastroenterology Congress , 1, 2

hepatic encephalopathy ||

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