086-0092 1.01 1

Brain Function Monitoring and it’s Role

in Anesthetic Management

Michael Geisler, CRNA, BSN

Private Anesthesia Practitioner

Ponte Vedra Beach, Florida

Learning Objectives •  Explore the rationale for monitoring brain function

•  Review Bispectral Index™ (BIS) fundamentals

•  Examine evidence-based results of BIS monitoring

•  Provide an update on Intraoperative Awareness

•  Using case studies, illustrate BIS responses during anesthesia

•  Discuss clinical applications and benefits of BIS monitoring

Why Monitor Consciousness?

Side-effects Costs Adverse Outcomes

Complications Adverse Outcomes

ANESTHETIC DEPTH

OVERDOSING UNDERDOSING ADEQUATE/OPTIMAL

BEST OUTCOMES Quality + Safety

Anesthetic Effect Management

086-0092 1.01 2

100

80

60

40

20

0

BIS

Recovery of Consciousness*

0 2 4 6 8 10 12

*Thiopental Induction (4 mg/kg)

Time (minutes)

Blo

od P

ress

ure

(MA

P) 180

140

100

60 12 10

8

6 4 2 0 Time (minutes)

Hea

rt R

ate

(bpm

)

150

120

90

60

30 12 10 8 6 4 2 0 Time (minutes)

“Hemodynamic signs do not correspond with a state of awareness.” 1Flaishon R et al. Recovery of Consciousness after Thiopental or Propofol. Anesthesiology 1997; 86(3):613-619.

“Recovery of Consciousness after Thiopental or Propofol”1

Hemodynamics and Consciousness

Poor correlation •  Anesthetic dose •  Sedation and consciousness

Inherent patient variability •  Children/elderly patients •  Patients on cardiac medications

Dosing considerations/restraints •  Elderly: ↓Requirement and ↑ CV sensitivity •  Patient profiles: Obese, ESRD, ESLD •  Altered requirements: Drug dependencies •  Intraoperative cardiovascular instability

Hemodynamics lack precision and utility

Why Measure Brain Effects Directly?

• A practical, processed EEG parameter that measures the direct effects of anesthetics and sedatives on the brain

• Numerical scale correlates to hypnotic endpoints

• Extensive clinical validation

• Provides objective information about an individual patient’s response to anesthesia

Bispectral Index (BIS)

086-0092 1.01 3

Donald R. Stanski and Steven L. Shafer, Miller’s Anesthesia, ed. Ronald D. Miller (Philadelphia: Elsevier Inc., 2005), p. 1252.

Signal Processing

Stanski DR, ShaferDL , Anesthesia, ed. Miller RD. (Philadelphia: Elsevier Inc., 2004), p. 1253.

EEG/BIS Response to Anesthetics

Alkire, Anesthesiology 1998; 89:323-333.

BIS Responds to Factors that Δ Metabolic Rate

•  Anesthesia •  Temperature •  Natural sleep •  Ischemia •  Neurologic disease •  Metabolic status

  Glucose   Thyroid function

34

95

62

66

38

54

64

100

BIS %BMR

BIS Correlates with Brain Metabolism

086-0092 1.01 4

Meta-analysis to examine the clinical impact of BIS monitoring on anesthetic use, incidence of PONV, duration of PACU stay and time to discharge in ambulatory anesthesia.

•  11 randomized controlled trials enrolling 1,380 subjects •  Comparison of BIS monitoring to standard practice (sp)

Key Results BIS monitoring:

•  Significantly reduced anesthetic use by 19% compared to sp •  Reduced the incidence of PONV by 16% •  Reduced PACU time by 4 minutes

Author estimated net cost of $5.55 per patient

Liu SS. Effects of Bispectral Index Monitoring on Ambulatory Anesthesia: A Meta-analysis of Randomized Controlled Trials and a Cost Analysis. Anesthesiology 2004; 101(2):311-315.

Clinical Impact of BIS Monitoring

Meta-analysis

Drug Savings (Gan, 1997; Bannister, 2001; Wong 2002; White 2004; Liu ,2004)

Isoflurane Propofol Sevoflurane Desflurane

Decreased PONV (Nelskya, 2001; Luginbühl, 2003)

Control BIS Titrated

Faster Wake-Ups (Gan, 1997)

Standard Practice BIS-Titrated

Shorter PACU Stays (White, 2004)

Standard Practice BIS-Titrated

Documented Anesthesia Benefit Summary

%

%

%

Min

utes

Denman WT et al. Anesthesia & Analgesia 2000; 90 (4): 872-877. Degoute CS et al. British Journal of Anaesthesia 2001; 86(2): 209-212. Davidson AJ et al. Anesthesia & Analgesia 2001; 93 (2): 326-330. Laussen PC et al. Paediatric Anaesthesia 2001; 11 (5): 567-573. Bannister CF et al. Anesthesia & Analgesia 2001; 92 (4):877-881. Johansen JW. Anesthesia & Analgesia 1998; 86: S406.

BIS-guided titration during general anesthesia: •  Correlates with the hypnotic component of anesthetics

accurately reflecting level of consciousness

•  Improves titration of general anesthetics

•  25-40% reduction in measured recovery times

•  Useful during pediatric anesthesia, including cardiac

Documented Benefits in Children

086-0092 1.01 5

•  General Incidence: 0.1-0.2% Sandin, Lancet 2001; Sebel, Anesth Analg 2004

•  Preoperatively, many patients are concerned

Royston & Cox, Lancet 2003;362:1648-58

•  Patients would pay $35 to prevent awareness Gan, J Clin Anesth 2003; 15:108-12

•  Highest risk factor for patient dissatisfaction Myles et al. BJA 2000; 84: 6-10

•  65% of patients do not tell their anesthetist Moerman et al. Anesthesiology 1993; 79:454-464

Is Intraoperative Awareness a Problem?

N Death Awareness Pain PONV

382 23% 19% 5% 6%

100 15% 15% - - 5%

129 54% 4.5% - - 22%

800 37% 24% 34% 22%

166 43% 52% 38% - -

132 19% - - 39% - -

1216 12% 20% 9% 12%

Royston & Cox, Anesthesia: the patient’s point of view. The Lancet 2003;362:1648-58

Patient Concerns Before Anesthesia

•  Large, prospective, multicenter study •  19,576 Patients interviewed •  Postoperatively and after one week •  Convenience sampling of all patients types

0

0.05

0.1

0.15

0.2

0.25

Site 1

Site 2

Site 3

Site 4

Site 5

Site 6

Site 7

Tota

l

Awareness Incidence by Site

Aw

aren

ess

Inci

denc

e %

1 case per 1000

1 case per 500

Sebel et al Anesth Analg 2004; 99:833-9

Awareness in the United States

086-0092 1.01 6

Ghoneim MM, Awareness During Anesthesia. Anesthesiology 2000; 92:597-602

Selection of inadequate anesthetic

dose

Resistance to anesthetics

Mechanical malfunction or

misuse of anesthetic machine

INADEQUATE ANESTHETIC

EFFECT

CONSCIOUSNESS EXPLICIT RECALL

Why Does Awareness Occur?

•  Definition, Role of NMB •  Patient Experience & Sequelae •  Incidence (0.1-0.2%) •  “High risk” Scenarios •  Current Monitoring Limitations •  Brain monitoring devices •  Anesthesia Challenge:

Balance psychological risk vs. physiologic risk •  Recommendation: Develop Awareness Policy

JCAHO Sentinel Event Alert · Issue 32 ���Preventing, and managing the impact of, anesthesia awareness ��� http://www.jcaho.org/about+us/news+letters/sentinel+event+alert/sea_32.htm

Practice Advisory for Intraoperative Awareness and Brain Function Monitoring

A Report by the American Society of Anesthesiologists Task Force

on Intraoperative Awareness

Adopted by ASA House of Delegates, October 2005. http://www.asahq.org

•  Not routinely indicated for general anesthesia patients •  The decision to use a brain function monitor should be

made on a case-by-case basis by the individual practitioner for selected patients

Brain Function Monitoring in Anesthesia Practice

086-0092 1.01 7

Strongly Agree

Agree

Uncertain

Disagree

Strongly Disagree

“Brain function monitors are valuable and should be used to reduce the risk of intraoperative awareness for patients with conditions that may place them at risk for intraoperative awareness”.

http://www.asahq.org

ASA Practice Advisory Member Survey

Emerging Role of Brain Monitors

Avoiding Awareness Algorithm

1. Assess Individual Risk 2. Change Care Appropriate to Risk 3. Use Multiple Modalities

BIS Monitoring

Patients Elderly Obese Medically-compromised

Pediatric Labile Organ dysfunction

Procedures Outpatient procedures Cardiac surgery Neurosurgery Office procedures

Increased awareness risk cardiac, trauma, obstetric, expected hypotension, airway surgery, limited cardiac reserve

Techniques Volatile-based anesthesia IV-based anesthesia Combined regional-general Muscle relaxant use

MAC & Procedural Sedation Perioperative Adjuvant therapy

Beta-blockers, Alpha-2 agonists Closed loop anesthesia

Broad Clinical Applications

086-0092 1.01 8

BIS Sample Profile: GA

Strategy for intraoperative management based on integration of BIS index value with observed clinical response. Patient management should never be based on BIS monitoring information alone.

Physical signs

Clinical profile

BIS Index*

Management strategy

Desired range (45-60)

Hypertension Tachycardia Movement Autonomic responses

Light

High value

Low Value •  Consider antihypertensive administration •  Assess level of surgical stimulation •  Consider ↓ hypnotic / ↑ analgesic dosing

•  Assess level of surgical stimulation •  Consider ↑ analgesic dosing •  Consider antihypertensive administration

•  Assess level of surgical stimulation •  Confirm delivery of hypnotics/analgesics •  Consider ↑ hypnotic / ↑ analgesic dosing •  Consider antihypertensive administration

*Potential impact of artifact should be considered when interpreting BIS values.

Patient Management Table

Adapted from Stanski DR, Shafer DL. Anesthesia, ed. Miller RD. (Philadelphia: Elsevier Inc., 2004) p. 1257.

•  Clinical judgment should always be used when interpreting BIS in conjunction with other available clinical signs.

•  Reliance on the BIS alone for intraoperative anesthetic management is not recommended.

•  As with any monitored parameter, artifacts and poor signal quality may lead to inappropriate BIS values.

•  BIS values should be interpreted cautiously in patients:  with known neurological disorders   taking psychoactive medications   in children below the age of one

Important Information about Using BIS Monitoring

086-0092 1.01 9

EMG Tone & Neuromuscular blockers may influence BIS   EMG Artifact: Excessive forehead muscle tone may increase BIS   Administration of NMB may alleviate EMG artifact & decrease BIS   During stable anesthesia without EMG artifact, NMB have no BIS

effect

Mechanical and electrical artifacts may increase BIS values   Forced-air warmers, surgical navigation systems   Pacemakers, endoscopic shaver devices

Certain anesthetics may produce different BIS responses   Ketamine   Halothane

Dahaba AA, Anesth Analg 2005; 101:765-73

Important Considerations

SQI – Signal Quality Index EMG – High-freq activity

BIS “Hollows” then blanks during low SQI

BIS Monitoring: Key Practical Issues

BIS Calculations: • BIS values may lag 15-30 s behind clinical state

due to signal processing & averaging • Real-time EEG display available • EMG Tone or Artifact may impact BIS value

Sensor Application

Stryker Snap II

 Different Algorithm  Different values  Same intent

086-0092 1.01 10

•  EMG tone & neuromuscular blockers may influence BIS

•  Mechanical and electrical artifacts may increase BIS values

•  Certain serious clinical conditions have been associated with low BIS values intraoperatively •  Hypovolemia, hypoglycemia, hypothermia, cerebral ischemia

•  Certain anesthetics may produce different BIS responses

Dahaba AA, Anesth Analg 2005; 101:765-73

Important Considerations

•  Examine for presence of artifacts (e.g., EMG, electrocautery or high frequency signals) •  Ensure anesthetic delivery systems are operating properly •  Ensure that the anesthetic dose is sufficient •  Assess current level of surgical stimulation •  Additional patient parameters (e.g., hemodynamics)

Responding to a Sudden BIS Increase

•  Assess for new pharmacologic changes •  Assess current level of surgical stimulation •  Assess for other potential physiologic changes •  Assess raw EEG for large delta waves (paradoxical delta)

Responding to a Sudden BIS Decrease

086-0092 1.01 11

70 year old female, 89 kg, ASA III, undergoing lumbar spinal decompression, fusion, instrumentation (L2-L5) Cardiac evaluation: EF=27% Anesthesia care: Premedication: Midazolam 2 mg Induction sequence:

•  Midazolam 2mg / Fentanyl 100mcg – divided doses during preoxygenation •  Propofol 50mg – observed response to BIS ~40 •  Rocuronium 40 mg to facilitate endotracheal intubation •  Esmolol 20mg and labetalol 2.5mg in response to BP 165/80

Peter C. Horowitz, M.D. Tulane University School of Medicine

Clinical Perspectives: Induction Management

0

20

40

60

80

100

7:41 7:58 8:16 8:33 8:50 9:08 9:25 9:42 10:00 10:17 10:34 10:52

Time

BIS

Luginbühl, M and Schnider T. Detection of Awareness with the Bispectral Index: Two Case Reports. Anesthesiology 2002;96:241-243

Noted that the anesthetics were "backed up" in the IV line.

Awareness: A Delivery Problem

Patient was not paralyzed, but did not move during this time.

80 yo female Right shoulder surgery GA with interscalene block Anesthesia: propofol and

remifentanil

An Algorithm to Avoid Awareness 1. Assess Individual Risk

086-0092 1.01 12

An Algorithm to Avoid Awareness

2. Change Care Appropriate to Risk

An Algorithm to Avoid Awareness

3. Use Multiple Modalities

Summary • BIS measures the hypnotic effects of anesthetics and

sedatives on the brain.

• Substantial evidence demonstrates the impact of BIS-guided anesthesia care:

•  Drug use •  Speed and quality of recovery •  Safety

• New ASA Practice Advisory provides guidance on awareness & brain function monitoring role.

• BIS monitoring can facilitate decision-making and patient management.

086-0092 1.01 13

Aver

age

Isof

lura

ne (

% in

spir

ed)

Clinical Utility in Elderly Patients

Standard Practice

BIS Titrated

27%

Faster Time to Orientation

Min

utes

Reduced Anesthetic Dosing

1%

0

.5%

1%

0.7%

Standard Practice

BIS Titrated

30%

Wong. Canadian Journal of Anesthesia 2002;49:13-18.

13.1 9.5

Organ Transplantation

 Mayo Clinic, Jacksonville Florida  Largest liver transplant program  50% of patients extubated in OR  30% bypass ICU to floor  BIS very important part of anesthetic

plan

New Generation Medications

 Precedex (dexmedetomidine)  Significant decrease in narcotics  Significant decrease in volatile agent  Bradycardia, hypotension masks depth of

anesthesia

086-0092 1.01 14

BIS Monitoring Adoption Published Scientific Literature

•  > 2,200 published studies

Broad clinical experience •  Over 13 million patients monitored to date

Significant BIS adoption •  Over 29,000 monitors & modules installed worldwide •  BIS monitoring available in 68% of “best” US hospitals

B-Unaware Trial

 First large independently funded evaluation of the technology

 Reports that BIS provides no greater reduction of anesthesia awareness than a protocol guided by levels of end-tidal anesthetic gases

New England Journal of Medicine (2008;358:1097-1108

B-Unaware Trial

 Critics say marketing and public demand, not science drove hospitals to adopt the monitor

 Looked at BIS vs. End Tidal Anesthetic Gas  ETAG - 0.7 - 1.3 MAC  BIS 40-60 target range  N= 950+ in both groups

086-0092 1.01 15

B-Unaware Trial

 Two patients in each high risk group had awareness

 Aspect defended their studies  Rate of awareness was 80% lower with the

BIS than in expected in high risk patients  Did not look at TIVA

Legal Aspects

 Washington v. Washington   What is standard of care for patients

 How will this change your practice

Questions?

Thank you for your attention