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112/04/08112/04/08 Liu, Chih-Min Liu, Chih-Min 11
Awareness Awareness During AnesthesiaDuring Anesthesia
Do You Remember…?Do You Remember…?
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References References Awareness during anesthesiaAwareness during anesthesia
• Anesthesiology Clinics of North AmericaAnesthesiology Clinics of North America Volume 20 • Number 3 • September 2002 Volume 20 • Number 3 • September 2002 Awareness with recall during general anesthesia – InciAwareness with recall during general anesthesia – Inci
dence and risk factorsdence and risk factors• Anesth AnalgAnesth Analg 86: 1084-1089, 1998 86: 1084-1089, 1998
Awareness during anesthesiaAwareness during anesthesia• AnethesiologyAnethesiology 2000; 92: 597-602 2000; 92: 597-602
BIS Monitoring to Prevent Awareness during General ABIS Monitoring to Prevent Awareness during General Anesthesianesthesia• AnethesiologyAnethesiology 2001; 94:520-2 2001; 94:520-2
Awareness detected by auditory evoked potential moAwareness detected by auditory evoked potential monitoringnitoring• BJABJA 91 (2): 209-2 (2003) 91 (2): 209-2 (2003)
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Before talking about it…Before talking about it…
Did you ever forget anything…?Did you ever forget anything…?• Patients are concerned that they would Patients are concerned that they would
not be asleep during their surgery not be asleep during their surgery ( more then 50%) ( more then 50%)
• For anesthesiologists, awareness under For anesthesiologists, awareness under anesthesia ranks second only to death anesthesia ranks second only to death as a “dreaded” complication as a “dreaded” complication
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DefinitionsDefinitions
ConsciousnessConsciousness• ‘‘The state of being conscious; The state of being conscious;
awareness of one’s own existence, awareness of one’s own existence, sensation, thoughts, surroundings, etc’sensation, thoughts, surroundings, etc’
AwarenessAwareness• ‘‘Having knowledge, conscious, Having knowledge, conscious,
cognizant’ cognizant’
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Incidence of awareness during Incidence of awareness during anesthesiaanesthesia
General surgeryGeneral surgery• 1960: 1.2%1960: 1.2%• 2000: 0.11% to 0.16%2000: 0.11% to 0.16%
Cardiac surgeryCardiac surgery• 1977: 5.8%1977: 5.8%• 1998: 0.3%1998: 0.3%
Other types of surgeryOther types of surgery• Major traumaMajor trauma
High from 11% up to 43% High from 11% up to 43% • Obstetric surgery (C/S)Obstetric surgery (C/S)
1968: 11.8%1968: 11.8% 1991: 0.9%1991: 0.9%
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Patient perceptions of awareness Patient perceptions of awareness
Most common Most common • Sounds and conversation – 89% to 100% Sounds and conversation – 89% to 100% • Sensation of paralysis - 85% Sensation of paralysis - 85% • Anxiety and panic Anxiety and panic • Helplessness and powerlessness Helplessness and powerlessness • Pain - 39% Pain - 39%
Least common Least common • Visual perceptions Visual perceptions • Intubation or tube Intubation or tube • Feeling the operation without painFeeling the operation without pain
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After-effects of Awareness During After-effects of Awareness During General AnesthesiaGeneral Anesthesia
Mental after-effectsMental after-effects• Muscle relaxationMuscle relaxation• PainPain• Fear of dyingFear of dying
Medico-legal after-effectsMedico-legal after-effects
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Mental after-effectsMental after-effects
37% of patients were responded with…37% of patients were responded with…• DisbeliefDisbelief• IgnoranceIgnorance• Anger Anger
14% of patients were told…14% of patients were told…• ““just a bad dream”just a bad dream”• ““all in your imagination”all in your imagination”• ““were med or hallucinating”were med or hallucinating”• ““had a seventh sense”had a seventh sense”
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Then…there wereThen…there were Sleep disturbances Sleep disturbances
• fear when falling asleep fear when falling asleep Repetitive nightmares Repetitive nightmares
• 52.4% 52.4% Anxiety and panic attacks Anxiety and panic attacks
• 55% 55% Depression Depression Flashbacks Flashbacks Avoidance of medical care Avoidance of medical care Preoccupation of deathPreoccupation of death Post-traumatic stress disorder (PTSD) Post-traumatic stress disorder (PTSD)
• 14.3% to 22% 14.3% to 22% • From months (20m) to years (17y)!From months (20m) to years (17y)!
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Medico-legal after-effectsMedico-legal after-effects
Very large compensations…Very large compensations…• USD 1,000 to 600,000USD 1,000 to 600,000
Risk factorsRisk factors• No volatile agents usedNo volatile agents used• FemaleFemale• Obstetric or gynecology procedureObstetric or gynecology procedure• Opioid only Opioid only • Muscle relaxantMuscle relaxant
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Causes of AwarenessCauses of Awareness
Light anesthesia Light anesthesia • Nitrous/opioid/relaxant anesthesia Nitrous/opioid/relaxant anesthesia • Myocardial depressionMyocardial depression• Hypovolemia Hypovolemia • Cesarean section Cesarean section • Difficult intubation Difficult intubation • Premature discontinuation of anesthetic Premature discontinuation of anesthetic
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Causes of AwarenessCauses of Awareness
Machine malfunction or misuse of techniMachine malfunction or misuse of technique que • Failure to check equipment Failure to check equipment • Vaporizer and circuit leaks Vaporizer and circuit leaks • Intravenous infusion errors Intravenous infusion errors • Accidental administration of muscle relaxanAccidental administration of muscle relaxan
t to awake patient t to awake patient
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Causes of AwarenessCauses of Awareness
Increased anesthetic requirements Increased anesthetic requirements • Variability in anesthetic requirements for intVariability in anesthetic requirements for int
ravenous agents ravenous agents • Increased anesthetic requirement because Increased anesthetic requirement because
of chronic alcohol, opioid, and cocaine abusof chronic alcohol, opioid, and cocaine abusee
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Causes of AwarenessCauses of Awareness
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Prevention of awareness Prevention of awareness 1.1. Administer amnestic premedicants. Administer amnestic premedicants. 2.2. Maintain vigilance regarding equipment and monitoriMaintain vigilance regarding equipment and monitori
ng. ng. 3.3. Minimize use of complete neuromuscular blockade. Minimize use of complete neuromuscular blockade. 4.4. Supplement nitrous/opiate anesthesia with a potent Supplement nitrous/opiate anesthesia with a potent
volatile anesthetic. volatile anesthetic. 5.5. Maintain 0.8–1.0 MAC of a potent volatile anesthetic bMaintain 0.8–1.0 MAC of a potent volatile anesthetic b
y itself. y itself. 6.6. Administer adequate dose of induction agent. Administer adequate dose of induction agent. 7.7. Obtain informed consent for high-risk patients. Obtain informed consent for high-risk patients. 8.8. Mask auditory input. Mask auditory input. 9.9. Provide education. Provide education. 10.10. Monitor for awareness.Monitor for awareness.
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Methods of detecting awarenessMethods of detecting awareness
Postoperative interviewPostoperative interview• Structured Structured • Best Best
Questions asked during interviewsQuestions asked during interviews1.1. What is the last thing you remember before going to What is the last thing you remember before going to
sleep for the operation?sleep for the operation?
2.2. What is the first thing you remember after waking after What is the first thing you remember after waking after the operation?the operation?
3.3. Do you remember anything in between?Do you remember anything in between?
4.4. Did you have any dreams?Did you have any dreams?
5.5. What is the most unpleasant thing you remember from What is the most unpleasant thing you remember from your operation and anesthesia?your operation and anesthesia?
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Methods of Monitoring Consciousness Methods of Monitoring Consciousness During General AnesthesiaDuring General Anesthesia
Clinical signsClinical signs• Sympathetic activities: HR, BP, sweating, puSympathetic activities: HR, BP, sweating, pu
pillary dilatation, lacrimation … pillary dilatation, lacrimation … • Unreliable Unreliable
Isolated forearm techniqueIsolated forearm technique EEGEEG
• BISBIS• AEPAEP
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Awareness detected by auditory Awareness detected by auditory evoked potential monitoringevoked potential monitoring
BJA 91 (2): 209-2 (2003)BJA 91 (2): 209-2 (2003)
Case reportCase report Accidental interruption of drug Accidental interruption of drug
delivery is a common cause of delivery is a common cause of awareness during general anesthesiaawareness during general anesthesia
A rapid change of AEP was noted A rapid change of AEP was noted when infusion of anesthetics was when infusion of anesthetics was stoppedstopped
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Prevention and Management of AwarenessPrevention and Management of Awareness
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Conclusions Conclusions
1.1. Incidence in general anesthesia: 0.1-Incidence in general anesthesia: 0.1-0.2% 0.2%
2.2. Incidence in cardiac surgery: 0.3%Incidence in cardiac surgery: 0.3%3.3. Lower dose of anesthetics are associated Lower dose of anesthetics are associated
with higher incidence of intra-op with higher incidence of intra-op awareness; insufficient concentrationawareness; insufficient concentration
4.4. Standard physiologic monitoring is not Standard physiologic monitoring is not reliable, such as AEP or BIS; however, reliable, such as AEP or BIS; however, clinical signs are much more unreliableclinical signs are much more unreliable
5.5. Psychiatric after-effect of awareness Psychiatric after-effect of awareness range from no effect to PTSDrange from no effect to PTSD
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Conclusions Conclusions
6.6. There is no evidence that any kind of premedication woulThere is no evidence that any kind of premedication would affect the incidence of awareness d affect the incidence of awareness
7.7. If prolonged laryngoscopy is required, one should not forIf prolonged laryngoscopy is required, one should not forget to add the induction agents or inhalation agentget to add the induction agents or inhalation agent
8.8. In critical hemodynamic situation, BZD instead of general In critical hemodynamic situation, BZD instead of general anesthetics may be acceptableanesthetics may be acceptable
9.9. NMBs should be used as sparingly as possibleNMBs should be used as sparingly as possible10.10. If the patient has a history of awareness under anesthesiIf the patient has a history of awareness under anesthesi
a, it would be wise to use monitora, it would be wise to use monitor11.11. If the patient has suffered from awareness, psychiatric coIf the patient has suffered from awareness, psychiatric co
nsultation and follow-up is recommended.nsultation and follow-up is recommended.
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Discussion Discussion Structured post-operative interviewsStructured post-operative interviews
• Best methodBest method• howeverhowever
Large number of patientsLarge number of patients Very sick patients: difficult to interviewVery sick patients: difficult to interview
Feedback information to the anesthesiologistsFeedback information to the anesthesiologists• EducationEducation
Incidence from 4% to 1.5% in one studyIncidence from 4% to 1.5% in one study• Changes in drugs dosageChanges in drugs dosage
Increase in volatile agents, I.V. anesthetic agentsIncrease in volatile agents, I.V. anesthetic agents Decrease in muscle relaxantDecrease in muscle relaxant
BZD?BZD?• Have effect on memory but are not likely to be Have effect on memory but are not likely to be
anesthetic anesthetic
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Thanks for your attention! Thanks for your attention!
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