A small percentage of patients may have periods of awareness during anesthesia or recall certain features of the operative procedure. This can be a devastating experience with long-term sequelae. The presence of one or more risk factors should prompt questioning of the patient for evidence of awareness or recall.


Rate of occurrence: overall the rate is reported as 0.1 to 0.2% of patients undergoing general anesthesia


Type of procedure:

(1) trauma

(2) Caesarean section

(3) cardiac surgery


Depth of anesthesia:

(1) trying to use a lower dose of anesthetic agents

(2) not properly monitoring the patient

(3) conscious sedation

(4) occurrence of a rise in blood pressure > 30 mm Hg and/or heart rate > 30 beats per minute during the procedure (Moerman, page 461)



(1) a lot of talking in the operating room, especially if unprofessional (more opportunity for something to be recalled)


Patient factors:

(1) history of previous awareness or recall during surgery (Cobcroft, page 842)

(2) paradoxical reaction to sedative (arousal or hyperactivity, see Complications of Anesthetic Agents)

(3) suggestible personality (Because of alarming reports in the lay press, some people may claim recall even when there is none. This is unlikely if the person can recall specific events that are known to have occurred during the procedure.)


The proper use of bispectral analysis during anesthesia administration reportedly can prevent awareness and recall if the index is kept < 55 (Myles, page 1762).


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