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?