Awareness of AwarenessRoy Esaki

September 6 2012PACU

“Every year 20 million people are put under anesthesia. 1 in 500 stay awake the whole time” ◦ –Claim from Awake

Intraoperative Awareness

Public Awareness and Concern

Survey of 130 patients assessing importance of postoperative outcomes:

◦ 20% of people reported “recall without pain” as the most important concern

◦ Overall relative weights:

Vomiting 18 Gagging on ETT 17.9 Pain 17.0 Recall without pain 13.8 Nausea 11.8 Residual weakness 8.0

Macario, A&A; 1999

Patient Concerns

Clinical Background◦ Etiology◦ Clinical Features◦ Diagnosis

Brain Function Monitors

Treatment and Prevention

“Awareness” without general anesthesia

Overview

“Explicit recall of sensory perceptions during general anesthesia”

What is intraoperative awareness?

Vs “Awareness” during MAC or Dreams(Correlate patient report with surgical events)

Inadequate Anesthetic Effect◦ Inadequate dose (TIVA)◦ Resistance to anesthetic◦ Machine malfunction

May result in:◦ Immediate emotional and physiological response◦ Long-lasting Anxiety/PTSD◦ Avoidance of future medical care or surgeries◦ Lawsuits

Causes and Consequences

Mashour, A&A, 2010

Generally accepted incidence 0.1-0.3%

◦ Full range from .007-1%◦ 2004 JCAHO Sentinel alert: 20,000-40,000 cases of awareness

annually out of 21 million general anesthetics

Incidence

1. Sandin, 20012. Sebel, 2004

Risk Factors

High Risk Surgeries:

•Cardiac Surgery

•Trauma

•(Emergent) Cesarean Section

High Risk Situations:

•Difficult intubation

•Hypovolemia

•TIVA

•Paralysis

Clinical Signs◦ Sympathetic activation◦ Movement, Lacrimation, Sweating

Isolated Forearm◦ Inflate tourniquet prior to muscle relaxant (like ECT)

Brain Function Monitors◦ Processed EEG to “quantify” depth of sedation◦ BIS, SEDLine, Narcotrend

Intraoperative Diagnosis

Principle of Depth of Anesthesia Monitors

Measure frontal cortex activity (+/-) EMG signalAnalyze FrequencyProprietary and empirically derived formula outputs number indicating “depth of anesthesia”

Various Monitors

BIS (Bi-spectral index)

SEDLINE (Patient State Index)

Keep value 40-60 for general anesthesia

BIS value

◦ Unchanged by nitrous oxide◦ Ketamine increases BIS value◦ Lower BIS index in neurological impairment

Cerebral ischemia Dementia Hypoglycemia

Caveats

Highly controversial◦ Industry-sponsored trials◦ Direct-to-consumer advertising by device manufacturer

“B-aware” study (Myles, 2004)◦ 2643 patients at high risk of awareness◦ Routine (11/1418) ) vs BIS (2/1225) guided anesthesia◦ 82% Reduction of awareness by BIS; NNT =138

“B-unaware” study (Avidan, 2008)◦ 2000 high-risk patients◦ End-tidal anesthetic gas-based protocol (2/974) vs

BIS (2/967)◦ No reduction in awareness

Ongoing Multi-center studies for average-risk patients

Does BIS work?

2006 ASA Task Force on Intraoperative Awareness”

“Brain function monitoring is not routinely indicated for patients undergoing general anesthesia, either to reduce the frequency of intraoperative awareness or to monitor depth of anesthesia”◦ “There is insufficient evidence to justify a standard, guideline, or

absolute requirement that (depth of anesthesia) devices be used to reduce the occurrence of intraoperative awareness in high-risk patients undergoing general anesthesia

BIS Not Routinely Indicated

2007 Cochrane Review:

◦ Modest reduction in intraoperative primary anesthetic agent

◦ Faster recovery Eye opening 2.4 minutes

Verbal Command 2.3 minutesExtubation 3 minutes

Decreased PACU stay by 6.8 minutes) No change in time to home readiness

◦ Less post-operative nausea/vomiting

Significantly reduced the incidence of intraoperative recall awareness in surgical patients with high risk of awareness (OR 0.20, 95% CI 0.05 to 0.79).

Benefits to BIS

Listen, reassure, acknowledge◦ Document details of patient report◦ Open-ended (vs leading) questions

Alert anesthesia team involved with case Offer medical and mental health follow-up Contact risk management (Anesthesia provider)

Novel Treatment◦ Psychotherapy + Gradual desensitization to OR

If a patient reports awareness

Mashour, Anesthesiology 2008

32 year old woman underwent a cesarean delivery. When interviewed about anesthetic problems postoperatively, she complained of “hearing conversations, seeing bright lights, and feeling as though she were underwater. She was quite distressed by the recollections, as she “felt as though she were dead”

A Case of Awareness:

Patients report “awareness”◦ Occasionally with psychiatric consequences◦ Patients report “awareness” to online awareness database,

future anesthesia providers

Similar incidence of complaints of awareness in general (.023%) vs MAC or regional anesthesia ( .03%)

“Awareness” During Sedation

Mashour, A&A, 2009

117 patients undergoing regional anesthesia or MAC◦ Structured pre-operative and post-operative

interviews

Examined role of expectations for level of consciousness

Source of Expectation

Esaki, A&A, 2009

Nurse

Expected vs Experienced level of Consciousness

1-10 scale (completely asleep to completely awake)

Patients less awake than expected (15%) Patients more awake

than expected (8%)

Patients heavily sedated, or amnestic during previous MAC think they received general anesthesia may expect complete loss of consciousness for all future (MAC) cases

Appropriate message for MAC case:

◦ “Don’t worry you’ll be asleep for the whole procedure”

vs

◦ “We’ll keep you comfortable and will give you medication for pain and anxiety” “You may fall asleep or forget what happened, but that doesn’t

mean it’s general anesthesia” It’s like having a lot to drink—some people remember bits and

pieces or don’t remember all

“Going to sleep”

“The distinction between general and nongeneral anesthesia is often unclear from the patient’s perspective.

Anesthesia providers might better educate patients regarding intraoperative levels of consciousness and postoperative recall.”

Punchline

The perioperative health care team

Esaki RK, Mashour Ga. Complaints Of Intraoperative Awareness After Regional Anesthesia And Sedation, In: Consciousness, Awareness, And Anesthesia, Mashour Ga Ed. Cambridge University Press. 2010

Esaki RK, Mashour GA. Level of Consciousness Monitoring, In: Hand book of Anesthesia Equipment, Sandberg W ed. Elsevier. 2011.

Mashour GA, et al. A retrospective study of intraoperative awareness with methodological implications. Anesth Analg 2009;108:521–6

Mashour, et al. A Novel Classification Instrument for Intraoperative Awareness Events. Anesth Anal 2010; 110: 813-815

Sebel PS, et al. The incidence of awareness during anesthesia: a multicenter United States study. Anesth Analg 2004;99:833–9

Sandin RH, et al. Awareness during anaesthesia: a prospective case study. Lancet 2000; 355:707–11

Pollard RJ, et al. Intraoperative awareness in a regional medical system: a review of 3 years’ data. Anesthesiology 2007;106:269–74

Selected References