J. Schulte am Esch . E. Kochs (Eds.)

Central Nervous System Monitoring in Anesthesia and Intensive Care

With 127 Figures, Some in Color

Springer-Verlag Berlin Heidelberg New York London Paris Tokyo Hong Kong Barcelona Budapest

Prof. Dr. med. J. SCHULTE AM ESCH Prof. Dr. med. E. KOCHS

Department of Anesthesiology University Hospital Eppendorf University of Hamburg Martinistrasse 52 20246 Hamburg Germany

ISBN-13:978-3-642-78443-9 e-ISBN-13 :978-3-642-78441-5 DOl: 10.1007/978-3-642-78441-5

Library of Congress Cataloging-in-Publication Data. Central nervous system monitoring in anesthesia and intensive care/J. Schulte am Esch, E. Kochs, eds. p. cm, Includes bibliographical references and index. ISBN-13 :978-3-642-78443-9(U .S.)I.Electroencephalography .2.Evoked potential (Electrophysiology)3.Patient monitoring. 4. Intraoperative monitoring. 5. Critical care medicine. I. Schulte am Esch, J. (Jochen), 1939- . II. Kochs, E. (Eberhard), 1943- . RC386.6.E43C46 1994 616.8'047547--dc20 94-2610

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Preface

Research in electrophysiologic monitoring in anesthesia and intensive care has focussed mostly on questions pertinent for patient care: First how to quantitate drug effects on brain electrical activity and the degree of anesthetic-induced suppression of the central nervous system. Second, how to monitor functional impairment following cerebral ischemia and hypoxia. And third, how to differ­entiate between drug-induced effects on the central nervous system and deleteri­ous events related to reductions in cerebral blood flow and/or oxygen delivery.

Even though progress has been achieved over the last 10 years in this field and fascinating new techniques have been developed, it is still not clear which monitor parameter will provide adequate information on the depth of anes­thesia and the analgesic level. Because the central nervous system has been one of the main research areas in our department over the last 10 years, we organized a workshop to summarize the latest developments in central nervous system monitoring. This book comprises the topics of this workshop and is intended to provide insight into the current status of central nervous system monitoring, elucidating possible indications and delineating its limitations.

For more than 30 years a primary goal for intraoperative neurophysiologi­cal monitoring has been to get a warning when cerebral oxygen supply may be hampered. This, obviously, is of special interest during surgical procedures which may impair cerebral blood flow such as carotid endarterectomy, intra­cranial aneurysm, or spinal cord surgery. Many monitoring techniques have been developed to predict imminent neuronal damage. In this sense, in­traoperative monitoring is used specifically to observe the response of the central nervous system to surgical interventions. The hope was that peri­operative morbidity and mortality may be decreased by continuous or frequent assessment of neuronal function. Some monitoring techniques, such as EEG or evoked potential monitoring during carotid endarterectomies, have been shown to be very sensitive and specific for the prediction of postoperative neurologic outcome. For other surgical procedures the best monitoring parameter still has to be defined.

A specific anesthesiologic goal which also has gained interest over the past years is the assessment of the depth of anesthesia by neurophysiological monitoring. The hope that the EEG may provide unique parameters has not been substantiated because various anesthetic agents may produce different

VI Preface

EEG patterns. However, using computerized analysis methods, EEG frequency descriptors (i.e., median frequency and spectral edge frequency) have been advocated for the assessment of changes in depth of anesthesia. In closed-loop feedback systems the median frequency has been shown to be useful for super­vising anesthetic drug administration. However, single parameters may not be helpful for assessing sedative/hypnotic as opposed to analgesic effects. It has become clear over the last years that the so-called intraoperative arousal phenomena may be of concern when there is an inadequate depth of anesthesia. In the EEG desynchronization with appearance of fast low wave activity has been considered to indicate arousal phenomena. Recent studies have shown that the shift to slower waves induced by surgical manipulations may also reflect electrophysiologic arousal reactions. This has made it clear that at the time being no single EEG parameter can be defined which unequivocally indicates intraoperative arousal. Furthermore, the EEG may not reflect the level of drug induced analgesic effects. Several studies suggest that evoked responses hold promise for intraoperative assessment of the inadequate depth of anes­thesia. Early cortical auditory and somatosensory evoked responses change in a graded manner with changes in depth of anesthesia. With few exceptions these changes are not anesthetic specific. In addition, it has been shown that surgical stimulation during an inadequate depth of anesthesia will reverse the depressant effects of anesthetics. Further work has to show which anesthetic technique will be most useful for achieving this goal in intraoperative monitor­ing. There is evidence that auditory evoked responses may indicate in­traoperative awareness. Specific cortical components of auditory evoked re­sponses seem to be related to auditory signal processing. Further studies have to show if drug administration can be controlled by auditory evoked responses in order to impair transmission of sensory stimuli to implicit memory. From several studies on auditory evoked responses including the 40-Hz steady state response, it can be concluded that these measures hold promise for assessing the hypnotic effect of anesthesia. Somatosensory evoked responses have also been shown to change in relation to anesthetic drug concentration in a non-agent­specific manner (exception: etomidate). It has been demonstrated in a few studies that surgery may also offset the anesthetic induced depressant effects on somatosensory evoked responses. However, it is unclear if these changes are related to inadequate sedation. The stimulation of large mixed peripheral nerves, such as is used for conventional somatosensory evoked response monitoring, recruits different afferent pathways. In contrast, specific pathways have to be stimulated to assess changes in nociceptive signal transmission. Various studies have shown that somatosensory evoked responses following the stimulation of C- and Ab- fibers correlate to drug induced changes in pain perception. However, these cortical evoked responses are very vulnerable to changes in psychophysiologic variables (i.e., attention, alertness, vigilance) and are suppressed by virtually all anesthetics. Few studies have shown that these evoked responses may be used for the assessment of analgesic treatment effects during anesthesia.

Preface VII

In contrast to somatosensory evoked responses, transcranial stimulation may be used for monitoring efferent pathways. This modality may be especially useful during surgical procedures when motor pathways are at risk. However, most anesthetics reduce the amplitudes of the evoked responses significantly. To interpret electrophysiologic data, changes in systemic variables have to be considered. Simultaneous recordings of brain function and cerebral blood flow velocities or venous jugular bulb oxygen saturation may help in the detection of deleterious effects.

Basic science and clinical applications complement each other. The syn­thesis of both, the exchange of scientific research and routine clinical practice, will lead to a concept which will bring about the maximal benefit for patient care. Therefore, one of today's pending challenges is to find monitoring tech­niques for clinical practice which allow the unequivocal assessment of central nervous system function during anesthesia and intensive care.

It was O. W. Holmes who, in 1840, stated that the great thing in this world is not so much where we stand, but in what direction we are going. In this sense we understand the current trends in the development of central nervous system monitoring techniques. It was the goal of this book to give an insight into the ever developing process on new specific monitoring techniques and how they may be used in the future. This in mind, we hope that this book will stimulate scientists and physicians to continued research in the field of central nervous system monitoring.

We are very grateful to the international group of distinguished speakers and chairmen as well as to the audience for the excellent contributions and discussions in this workshop. We are also much indebted to Mrs. L. Berger for her technical assistance in preparing the workshop and her help in organizing the publication of this book.

Hamburg, January 1994 JOCHEN SCHULTE AM ESCH

EBERHARD KOCHS

Contents

Part I Monitoring of the Electroencephalogram - Fundamentals

Interactions of Anesthetics at Different Levels of the Central Nervous System B. w. Urban . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Principles of Central Nervous System Monitoring in Humans R.-D. Treede . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Part n Techniques and Applications of Electroencephalogram-Monitoring

Pharmacokinetic and Pharmacodynamic Interactions Relevant To Cerebral Monitoring H. J. M. Lemmens ........................................ 29

Electroencephalographic Feedback Control of Anesthetic Drug Administration H. Schwilden . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

The Use of Processed EEG in the Operating Room M. J. Bloom ............................................. 56

Bispectral Electroencephalogram Analysis for Monitoring Anesthetic Adequacy J. M. Vernon, P. S. Sebel, S. M. Bowles, N. Chamoun, and V. Saini ............................................. 69

Does Spectral Edge Frequency Assess Depth of Anesthesia? G. M. Gurman ........................................... 78

"Paradoxical Arousal" During IsofluranejNitrous Oxide Anesthesia: Quantitative Topographical EEG Analysis P. Bischoff, E. Kochs, and J. Schulte am Esch ................... 91

Central Nervous System Monitoring; Reduction of Information Content of Quantitative Electroencephalograms for Continuous On-Line Display During Anesthesia W. Dimpfel and H.-C. Hofmann............. .. .. ........... .. 103

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Part HI Monitoring of Stimulus Evoked Responses

Central Evoked Brain Potential as Overall Control of Afferent Systems

Contents

B. Bromm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Indication for Evoked Potential Monitoring: A Surgical View J. Zentner and J. Schramm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

Anesthesia and Somatosensory Evoked Responses E. Kochs and P. Bischoff ................................... 146

Peri-operative Anesthesiological Monitoring of Auditory-Evoked Potentials C. Thornton, P. Creagh-Barry, and D. E. F. Newton. . . . . . . . . . . . . . 176

The 40-Hz Auditory Steady State Response for Monitoring Level of Consciousness: Methodological Considerations C. Villemure, G. Plourde, and P. April. . . . . . . . . . . . . . . . . . . . . . . . . 187

Motor Evoked Potentials C. J. Kalkman . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

Part IV Evoked Response: Special Applications

Auditory Evoked Potentials to Monitor Intra-operative Awareness D. Schwender, S. Klasing, C. Madler, E. Poppel, and K. Peter ...... 215

Evoked Potential Monitoring for Vascular Surgery M. Dinkel, H. Loder, H. Langer, H. Schweiger, and E. Riigheimer 230

Assessment of Analgesic Drug Treatment E. Scharein .............................................. 248

Long-Term Monitoring in Intensive Care Patients: Electroencephalogram, Evoked Responses, and Brain Mapping E. Facco, M. Munare, F. Baratto, A. U. Behr, and G. P. Giron 257

Part V Present and Future Trends in Cerebral Monitoring

Present and Future Trends in Multimodal Cerebral Monitoring in Anesthesia and Intensive Care G. Litscher, G. Schwarz, W. Marte, G. Pfurtscheller, and W. F. List ........................................... 283

Jugular Bulb Venous Oxygen Saturation and Transcranial Doppler Ultrasonography in Neurosurgical Patients N. M. Dearden . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

Contents

Transcranial Doppler Sonography: Monitoring of Cerebral Perfusion

XI

C. Werner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314

BRAINDEX - An Expert System for Supporting Brain Death Diagnosis G. Rom, R. Grims, G. Schwarz, and G. pfurtscheller . . . . . . . . . . . . . . 326

Subject Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335

Contributors

BISCHOFF, P., Dr. Abteilung fiir Anasthesiologie, Universitats-Krankenhaus Eppendorf, Martinistr. 52, 20246 Hamburg, Germany

BLOOM, M.J., M.D., Ph.D. Assistant Professor School of Medicine, Departments of Anesthesiology jCCM, University of Pittsburgh, Pittsburgh, PA 15213, USA

BROMM, B., Prof. Dr. Dr. Physiologisches Institut, Universitats-Krankenhaus Eppendorf, Martinistr. 52, 20246 Hamburg, Germany

DEARDEN, N.M., M.D. Dept. of Anaesthesia, Leeds General Infirmary, Leeds LS12 4AD, Scotland

DIMPFEL, W., Prof. Dr. ProScience, Private Research Institute, Linden, 35390 Giessen, Germany

DINKEL, M., Dr. Institut fiir Anasthesiologie der Universitat Erlangen - Nurnberg, Krankenhaus Str. 12, 91054 Erlangen, Germany

DOENICKE, A., Prof. Dr. Anasthesiologische, Abteilung, Chirurgische Poliklinik der Universitat, Pettenkoferstr. 8a, 80336 Munchen, Germany

F ACCO, E., M.D. 1st. Anestesiologia e Rianimazione, Universita di Padova, Via C. Battisti 267, 35121 Pad ova, Italy

GURMAN, G., M.D., Prof. Division of Anesthesiology, Soroka Medical Center, Beer-Sheva 84101, Israel

HEMPELMANN, G., Prof. Dr. Institut fur Anasthesiologie, Universitatskliniken, Klinikstr. 29, 35392 Giessen, Germany

XIV

KALKMAN, c., M.D., Ph.D. Department of Anesthesiology, University Hospital Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands

KOCHS, E., Dipl. Phys., Prof. Dr.

Contributors

Abteilung fiir Anasthesiologie, Universitats-Krankenhaus Eppendorf, Martinistr. 52, 20246 Hamburg, Germany

LEMMENS, H.J.M., M.D., Ph.D. Prof. Veterans Administration Medical Center, School of Medicine, Stanford University, Palo Alto, CA 94304, USA

LITSCHER, G., Dipl. Ing., Dr. Univ.-Klinik fiir Anasthesiologie, Landeskrankenhaus, 8036 Graz, Austria

PLOURDE, G., M.D., M.Sc. Department of Anaesthesia, Royal Victoria Hospital, 687 Pine Avenue West, Suite 5.05, Montreal (Quebec), Canada H3A lAB

ROM, G., Dipl. Ing. Department of Medical Informatics, Institute of Biomedical Engineering, Graz University of Technology, 8036 Graz, Austria

SCHAREIN, E., Dipl. Psych., Dr. Physiologisches Institut, Universitats-Krankenhaus Eppendorf, Martinistr. 52, 20246 Hamburg, Germany

SCHULTE AM ESCH, J., Prof. Dr. Abteilung fiir Anasthesiologie, Universitats-Krankenhaus Eppendorf, Martinistr. 52, 20246 Hamburg, Germany

SCHWENDER, D., PD Dr. Institut fiir Anasthesiologie, Klinikum Grosshadern, Marchioninistr., 81377 Miinchen, Germany

SCHWILDEN, H., Prof. Dr. Dr. Institut fiir Anasthesiologie der Universitat Bonn, Sigmund-Freud-Str. 25, 53127 Bonn, Germany

SEBEL, P.S., M.B., B.S., Ph.D., FFARC SI, Department of Anesthesiology, Emory, University at Crawford Long Hospital, Atlanta, GA 30308, USA

STOECKEL, H., Prof. Dr. Institut fiir Anasthesiologie der Universitat Bonn, Sigmund-Freud-Str. 25, 53127 Bonn, Germany

Contributors

THORNTON, Ch., Ph.D. Division of Anaesthesia, Clinical Research Centre, Northwick Park Hospital, Harrow, Middlesex HAl 3UJ, UK

TREEDE, R.D., Prof. Dr. Physiologisches lnstitut, Klinikum der Johannes-Gutenberg-Universitat, Saarstr. 21, 55122 Mainz, Germany

URBAN, W., Prof. Dr.

xv

lnstitut fUr Anasthesiologie der Universitat Bonn, Sigmund-Freud-Str. 25, 53127 Bonn, Germany

V AN AKEN, H., Prof. Dr. Dept. of Anesthesiology, Universitaire Ziekenhuizen Katholieke Universiteit Leuven, 3000 Leuven, Belgium

VERNON, J.M., Dr. Department of Anesthesiology, Emory, University at Crawford Long Hospital, Atlanta, GA 30308, USA

VILLEMURE, c., Dr. Department of Anaesthesia, Royal Victoria Hospital, 687 Pine Avenue West, Suite 5.05, Montreal (Quebec), Canada H3A lAB

WERNER, c., Dr. Abteilung fUr Anasthesiologie, Universitats-Krankenhaus Eppendorf, Martinistr. 52, 20246 Hamburg, Germany

ZENTNER, J., PD Dr. Neurochirurgische Klinik der Universitat Bonn, Sigmund-Freud-Str. 25, 53127 Bonn, Germany