AWARENESS

LOOK FOR

There may be no obvious signs (1)
Hypertension
Tachycardia
Reflex activity:
     Withdrawal/movement
     Coughing/straining
     Pupillary dilation
     Sweating/tears

HIGH RISK SITUATIONS (2)

Patient factors: 
     History of drug/alcohol abuse
     Highly anxious patient
     Previous awareness
Equipment problems: (3)
     Vaporiser leaking/empty/mal-positioned
     Incorrectly calibrated vaporiser
     Nitrous oxide run out
     Failure of drug delivery with TIVA
Drug errors: (4)
     Syringe swap causing paralysis before induction
     Syringe swap causing non delivery of opioid/sedative
Anaesthetic technique:
     Deliberate light anaesthesia during crisis management or caesarean section
     Opioid based anaesthesia
     Regional/local anaesthetic techniques
     Anaesthesia with paralysis (5)
Other problems:
     Laryngospasm/airway obstruction
     Difficult/prolonged intubation (6)
     Delayed extubation

EMERGENCY MANAGEMENT

Stop painful surgical or other stimuli
Verbally reassure the patient
Rapidly deepen anaesthesia
Consider amnestic drugs: eg. midazolam 3mg IV bolus

FURTHER CARE

Interview the patient post operatively as soon as possible, and again several days later (7)
Reassure the patient
Explain what has happened
Be honest and sympathetic
Arrange for follow up
See  - After the Crisis

NOTES:
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Twenty-one (21) cases of awareness under general anaesthesia were reported in the first 4000 AIMS reports. In 43% of these the conduct of the anaesthesia appeared unremarkable; and awareness was only diagnosed post-operatively by an unsolicited patient complaint. The COVER ABCD algorithm would have detected almost all causes of awareness where it was actually suspected, but would be ineffective in patients who were aware but lacked physical signs to indicate its presence.
(1) There may be no signs to indicate awareness. In 43% of 21 cases of awareness under general anaesthetic, there were no remarkable changes to alert suspicion.
(2) Commonest causes under general anaesthesia included:
          low concentration of volatile agent 38%
          in association with a crisis 23%
         failure to check equipment 19%
         justified risk taking 10%
(3) The most frequently identified cause of awareness under general anaesthetic was a low concentration of volatile agent. The commonest preventable cause was secondary to a failure to check equipment, specifically the vaporiser. There were 2 reports related to total intravenous anaesthesia, caused by failure to deliver the drug to the patient. Failure to deliver nitrous oxide was also reported.
(4) There was another group of 20 incidents involving accidental paralysis prior to induction and whilst awake. The majority involved syringe swaps immediately prior to induction, particularly suxamethonium for opioids.
(5) If full paralysis is avoided except where absolutely necessary there is a greater chance that a patient will be able to indicate that they are aware.
(6) There were 2 reports of awareness during difficult intubations
(7) Awareness may not be diagnosed for several days after the incident.

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