Prevention of intraoperative Awareness in High-Risk Surgical Population NEJM August 2011

Intraoperative Awarenss

Plan Awareness – Defintion BIS Previous Studies Journal Article Conclusion & Recommendations

Awareness Explicit Memory ◦ Active ◦ Intentional or conscious recollection of prior experiences as assessed by tests Implicit Memory ◦ Passive ◦ Perception without conscious recall. Patient denies recall but may remember “something” under hypnosis Deliberate ◦ Regional/Local Anaesthesia. Waking of patient during neurosurgical procedures

Stages of Awareness Griffith and Jones described 5 stages of perception during general anaesthesia with memory of intra-operative events 1.Conscious perception with explicit memory 2.Conscious perception without explicit memory 3.Dreaming 4.Subconscious perception with implicit memory 5.No perception and no implicit memory

Modified Brice Questionnaire Were you expecting to be completely asleep for this operation (please circle)? YES / NO 1. What is the last thing you remember before going to sleep (please tick one box)? -Being in the pre-op area ☐ -Seeing the operating room ☐ -Being with family ☐ -Hearing voices ☐ -Feeling mask on face ☐ -Smell of gas ☐ -Burning or stinging in the IV line ☐ -Other [Please write below]: 2. What is the first thing you remember after waking up (please tick one box)? -Hearing voices ☐ -Feeling breathing tube ☐ -Feeling mask on face ☐ -Feeling pain ☐ -Seeing the operating room ☐ -Being in the recovery room ☐ -Being with family ☐ -Being in ICU ☐ -Nothing ☐ -Other [Please write below]:

Modified Brice Questionnaire 3. Do you remember anything between going to sleep and waking up (please tick box)? -No ☐ -Yes: -Hearing voices ☐ -Hearing events of the surgery ☐ -Unable to move or breathe ☐ -Anxiety/stress ☐ -Feeling pain ☐ -Sensation of breathing tube ☐ -Feeling surgery without pain ☐ -Other [Please write below] 4. Did you dream during your procedure (please tick box)? -No ☐ -Yes ☐ -What about [Please write below]: 5. Were your dreams disturbing to you (please tick box)? -No ☐ -Yes ☐ 6. What was the worst thing about your operation (please tick box)? -Anxiety ☐ -Pain ☐ -Recovery process ☐ -Unable to carry out usual activities ☐ -Awareness ☐ -Other [Please write below]:

What is BIS? Google says ◦ British Interplanetary Society ◦ A Scottish band (Sci-fi Steven and John Disco) ◦ A bank the Nazis used to launder money ◦ Bishops Stortford Train Station ◦ Bispecitral index monitoring

BIS Frontotemporal EEG trace Fed into Algorithm to give a dimensionless number = “normal” cortical activity 0 = cortical electrical silence

BIS Essentially a group of healthy individuals were anaesthetised/sedated Fixed end points were assigned from consciousness to unconsciousness using different agents The EEG changes were analysed and from this an algorithm created to give a number

Previous Studies AIM 2004 ◦ Assessed incidence ◦ 1-2/1000 in USA B-AWARE 2004 ◦ 2503 high risk for awareness patients ◦ BIS vs no BIS ◦ 82% reduction with BIS ◦ 2/1225 vs 11/1238

Previous Studies SAFE-1 Trial 2000/2002 ◦ Incidence of Awareness in Sweden ◦ 1.8/1000 with NMB ◦ 1/1000 without NMB ◦ 18/11,785  explicit recall ◦ 9 interviewed 2 years later  4 severely disabled due to PTSD

Previous Studies SAFE-2 Trial 2004 ◦ Sweden ◦ BIS vs No BIS ◦ Used historical control ◦ 2/4945 vs 14/7826 ◦ Reduction of 77%

Prevention of Intraoperative Awareness in a High-Risk Surgical Population High-Risk? ◦ Planned open heart surgery ◦ Aortic Stenosis ◦ Pulmonary Hypertension ◦ Use of Opiates ◦ Use of Benzodiazepines ◦ Use of anticonvulsant drugs ◦ Daily Alcohol consumption ◦ ASA 4 ◦ End-stage lung disease ◦ History of intraoperatuve awareness ◦ History of anticipated difficult intubation ◦ Cardiac ejection fraction <40% ◦ Marginal exercise tolerance

Study USA over 3 sites GA with Iso-, Sevo-, Desflurane 5713 patients Anaesthetist presented with envelope informing of which arm patient randomised to ◦ Patient, postop interviewer, expert reviewer and statistician blinded

Procedure BIS applied to everyone ◦ In non BIS the number was not available to the anaesthetist but recorded In BIS arm ◦ Alarm set for >60 & <40 In Non BIS ◦ Alarm set for Age adjusted MAC 1.3 BIS and ETAC electronically recorded at 1 minute intervals

Post op Interview at 72 hours and 30 days using Modified Brice Questionnaire If some awareness was suspected they were further contacted and asked additional questions

Results Of 5713 ◦ 49 reported “memories” ◦ 9 definite intraoperative awarenss 1.6/1000 ◦ 27 had definite or possible intraoperative awareness 4.7/1000

BIS ◦ Definite 7/2861 ◦ Possible 12/2861 ETAC ◦ Definite 2/2852 ◦ Possible 6/2852

Results

Results 5 out of the 9 who had definite awareness had BIS values 0.7

Discussion Results not as expected Trial does not support superiority of the BIS over ETAC for prevention of intraoperative awareness Suggest not to decrease Anaesthetic agent upon BIS value alone

Limitations 1. Limited to High risk patients 2. Only one EEG derived monitored tested 3. Compared BIS vs ETAC when combination may be better 4. Possible desentisation to protocol due to multiple false alarms sounds

Further Investigation NAP 5 SNAP 1