Awareness during Anaesthesia :
Incident or Mismanagement ?
Dr. Alain F. Kalmar, MD, PhD
Dep. Of Anaesthesia
University Medical Center Groningen
The Netherlands
Incident or Mismanagement ?
 Complex interaction between
- Pharmacology (PK/PD)
- Patient characteristics & genetics
- Surgical events
 Many unknown variables may increase risk
 Evolution to psychological disorders ~ our policy
 Inevitable event or anesthetic mismanagement ?
Action and receptors and … AROUSAL
NOXIOUS
STIMULUS
propofol
barbiturates
benzodiazepines
opiates
AROUSAL
inhalational an.
Local an.
Definitions?
“consciousness” is NOT equal to “awareness”
“physiological condition” versus “failed drug effect”
Types of Awareness Reports
 True Awareness with Recall and pain
 True Awareness with Recall but without pain
 Adequate response on demand without recall
 Opening of Eyes/Movement without Recall
 “Memories”
 Conscious Sedation (Inform patient !)
 Implicit (“Unconscious”) Learning
 Diagnose with complex psychological questionnaires
 Vivid dreaming
 Triggered by recovery experience?
 (Unwise to do sedation without witnesses)
Working and long-term memory
( Bailey AR et al., Anesthesia 1997, 52, 460 - 476. )
Central
executive
Encoding
Stimulus
Long term
memory
Phonological Visuospatial
loop
sketchpad
Working memory
Responding
Retrieval
Forgetting
Declarative and nondeclarative memory.
( Bailey AR et al., Anesthesia 1997, 52, 460 - 476. )
outside world
declarative
memory
working
memory
explicit
episodic
events or
episodes within
the subject’s life
nondeclarative
memory
implicit
semantic
skills and
procedures
priming
general or specific
knowledge
knowing how
increased ability
to identify a
stimulus as a
result of recent
presentation
Where did it all start?
 Awareness during anaesthesia became a problem after
muscle relaxants was introduced in the 1940’s
 Balanced anaesthesia:




Immobility
Haemodynamics
Analgesia
Hypnosis
 Curare
 Inotropica, vasodilators, B-Blokkers
 Opioids
 Hypnotics
 Smaller amount of general anaesthetics were needed.
 High Opioids / low hypnotics methods
 Changing attitude in patients
Cause of awareness
Study pitfalls
 Retrospective
 Many studies lack information on ET gas concentration or IV drug
concentrations.
Hard to compare anaesthetic techniques and causes
 The use of neuromuscular blockers has an important role and are
not always reported
 Definition
 Timing of the screening interview is crucial
 Many studies only interview patients once within 24 hours after surgery
 Underestimation of incidence is probable
Causes of Awareness
(closed claims analysis)
 N = 4183 closed claims (retrospective + selection bias)
- aspiration pneumonia
- awareness
- burns
2.4 %
1.9 % (=80 cases)
1.9 %
 Possible (retrospective) causes for awareness:
- N2O - relaxant technique
- hypotension (with decreased amount of hypnotics)
- inadequate doses of drugs
- obesity
- difficult intubation
- vaporizer leaks
- failure to turn on the vaporizer
- no obvious factor (Patient sensitivity???)
( Domino et al. Anesthesiology 1999, 90, 1053 - 61)
Incidence of explicit recall
Remember being awake and recall things that were said or done during operation
Year
Incidence
Hutchinson
1960
1.2%
656
Harris
1971
1.6%
120
McKenna
1973
1.5%
200
Wilson
1975
0.8%
490
Flier
1986
1.4%
140
Liu
1991
0.2%
1000
Nordström
1997
0.2%
1000
Ranta
1998
0.4 - 0.7%
2612
Myles
2000
0.11%
10811
Sandin
2000
0.15%
11785
Number of patients
The first half is not relevant today because the anaesthesia technique has
changed a lot.
With kind permission from Dr Rolf Sandin, Kalmar, Sweden
How damaging is Awareness?
 Global incidence 0.1-0.3%
 35-70/year in UMCG
 65% of patients do not tell the anesthesiologist
 Moerman et al. Anesthesiology, 1993 79:454-464
 50% of patients are concerned about awareness
 McCleane and Cooper. Anesthesia, 1990 45:153-5
 Highest risk factor for patient dissatisfaction
 Myles et al. Patient satisfaction after anesthesia and surgery . BJA, 2000 84 : 6-10
Awareness : patients’ evaluation
 Awareness :
- auditory perception
- sensation of paralysis
- anxiety, pain
- helplessness
- panic
>> 70 % : sleep disturbances, dreams, nightmares,
flashbacks,…
< % : P.T.S.S. ( repititive mightmares, anxiety, irritability,
preoccupation with death,…)
(ref.: Schwender et al. BJA, 1998, 80, 133-139)
(ref.: Domino et al. Anesthesiology 1999, 90, 1053 - 61)
Sandin’s study year 2000
 11785 patients
 1997 - 1999 in 2 hospitals
 Patients were interviewed 3 times
 Most of patient received Neuromuscular blockers
 18 patients identified with explicit recall
 At PACU: 11 of 18 identified
 Day 1-3 : 12 of 18 identified
 Day 7-14: 17 of 18 had explicit recall
 The 18 patient forgot everything, even the interview, but started to
remember some details after 21 days, but was not worried at all about it.
 1 of these had experienced awareness before.
Sandin’s study year 2000
 So, only half of cases can be identified with todays advice of
1 interview at PACU discharge
 Awareness : consequences:
 More Pain and chronic pain
 Panic
 Post Traumatic Stress Disorder
Explicit recall - long term effects
Evans 1987
Fear & Panic
Pain
Late mental effects
78%
41%
?
92%
39%
70%
50%
24%
49%
11%
21%
84%
64%
43%
n=27
Moerman 1993
n=26
Schwender 1998
n=45
Domino 1999
n=79 (closed claims)
Sandin et al.
n= 9-18 (prospective)
21%
With kind permission from Dr Rolf Sandin, Kalmar, Sweden
Sandin’s study
 There is only 21% late mental effects. But, that is after a few
weeks
 3 weeks after the awareness all 18 were happy.
 Interviews then happened 2 years later
 9 of the 18 could then be included
 6 refused interview: 2 wanted to avoid anything that had to do
with anaesthesia.
 2 could not be localised
 1 was dead
 So, what about the 9 that co-operated
Sandin’s study
 The last 9 that were located:
 4 had PTSD ( Post-Traumatic Stress Disorder)
 3 had less severe problems
 2 had no mental problems
 So, when you follow up over time, the result is different
Awareness : patients’ treatment
 Explicit recall must be taken serious
 Believe the patients experience
 Early referral to psychiatrists
 Repeated follow-ups
 In Sandin’s case, the less severe cases turned out to be the worst
and detected latest
 Memory for intraoperative events may improve for more than
10 days
 So, what can be done to prevent this?
Prevention
 Do not deny awareness risks?
 Seems that patient information reduces the risk of neurotic symptoms afterwards,
because the patient is “prepared” mentally that this could happen.
 A little bit of psychology seems to help to limit post awareness trauma
 Interview of patients?
 4 QUESTIONS as a standard routine (educate nurses)
 Did you sleep well?
 Last memory before falling asleep?
 First memory when waking up?
 Do you remember anything from in between these two moments?
 Do not deny your patients story?

(ref.: Schwender et al. BJA, 1998, 80, 133-139)
(ref.: Domino et al. Anesthesiology 1999, 90, 1053 - 61)
Considerate Conduct
“Anesthetized (but also awake) patients tend to sensor what they hear,
retaining comments they consider important. Common categories of
comments:
 the ‘fat lady syndrome’, in which doctors make derogatory appraisals
of a patient’s appearance.
 the ‘dirtball phenomen’, in which patients are treated to remarks
deriding their worth.”
 The ‘bad message’ effect, in which patients are focussed more on
negative than on reassuring messages
(Henry Bennett as quoted in Hippocrates, 1997)
Prevention
More Benzodiazepines?
Lancet 2000; 355:707
 More Benzodiazepines?
 No randomised ctr. Studies
 In the Sandin incidence paper similar incidence with/without use of
benzodiazepines.
 No strong evidence…
 the practice of giving benzodiazepines as a prevention
 = pure empirical conviction
“Valley of no anaesthesia” ????
Maybe... But no evidence
Induction with propofol bolus
“Depth of anaesthesia”
Sevoflurane maintenance
Valley of no anaesthesia
Avoid TIVA?
 Errando et al: Awareness with recall during general
anaesthesia: a prospective evaluation of 4001 patients, BJA
2008;101;7402
 1.1% awareness with TIVA
 0.6% with inhalation
 Sandin and Myles study: No sign. difference between patients
with TIVA vs inhaled anaesthesia
Explicit recall after TIVA
Incidence
Sandin 1993
Br J Anaesth
5 / 1727
Retrospective study
Nordström 1997
Acta Anaesthesiol Scand
Prospective study: Interview d1 + d7 (50%):
2 / 1000
Sandin 2000
The Lancet
Prospective study: Interview d1-3 + d7-14:
0 / 284
0.2%
With kind permission from Dr Rolf Sandin, Kalmar, Sweden
Prevention
End-tidal gas monitoring?
 Avidan et al NEJM 2011
 High risk population
 Power analysis OK
 Comparing BIS monitoring with MAC >0.7 concept
 RESULTS: See further at the prevention section
Prevention
Measure Vital Signs?
 Monitor Vital Signs (BP, Heart rate) only?
 vital signs reflect balance between OS and PS and not hypnosis
 The degree of depression of the Central Nervous System may not be totally correlated to
the degree of depression of the Cardio-Vascular System for a specific patient at each
moment.
This will be true also with patients without Cardio active medication.
 Many cases of intraoperative recall do not signal with hemodynamic changes
(Domino 1999)
 So, basically Vital Signs are
Insufficient
as an indication of awareness
Prevention
Value of neuro-physiological monitoring?
 General population :
Power analysis : 47022 patients needed to show reduction 0,2%  0,1%
of awareness!
 B-Aware trial (Myles P, The Lancet, 2004):
 Selection of high risk patients
 Multi centre study with sufficient inclusions
 Results: The use of BIS reduces the incidence of explicit awareness by 82% in a high risk
population. (p<0.002)
Prevention
Neuro-physiological monitoring IN GENERAL population? (Sandin
et al: Acta Anaesth Scand 2004: 48:20-6)
 Comparable results in a
former retrospective
Scandinavian trial (Sandin et
al ) in the general
population. (Retrospective
control)
 SAFE 2 trial : The use of BIS
reduces the incidence of
explicit awareness by 78% in
a general population.
(p<0.05)
0,17%
0,03%
Prevention
Neuro-physiological monitoring during inhaled anaesthesia in
high risk patients? (Avidan)
 Avidan et al. NEJM 2011:
 During inhaled sevofurane concentration, a strategy to keep sevo ET% >
0.7 MAC (+ setting alarms accurately + checklists and education) is
equally effective to avoid awareness in a high risk population compared to
BIS guided anaesthesia.
 BIS guided group 7/2861 (0.24%) compared to ETAC group 2/2852
(0.07%) but not statistically significant
 No mortality difference postoperatively
 Questions:
 Overdosing for some in ETAC harmful?
 What before intubation?
Final CONCLUSIONS 1
 Awareness is a problem for all anesthetists
 Awareness is not always a proof of medical error
Final CONCLUSIONS 2
 The consequences are worse than we think
Final CONCLUSIONS 3
 BIS is the only monitor that has evidence to support a
reduction in awareness in a high risk population with mixed
anaesthesia techniques.
 When Sevo>0.7 MAC in high risk population the incidence
of awareness = BIS monitored approach with lower MAC
accepted.
 General population: probably comparable effect but less
powerful evidence to support this
Final CONCLUSIONS 4
  USE BIS when you feel uncertain about the
hypnotic state of the patient.
Final CONCLUSIONS 5
 Try to detect eventual cases of awareness
 Immediately inform the patient about the
meaning of these experiences and show
empathy.
Questions?