Roger E. Padilla

The incidence of awareness during anesthesia: a multicenter United States study.

Awareness with recall after general anesthesia is an infrequent, but well described, phenomenon that may result in posttraumatic stress disorder. There are no recent data on the incidence of this complication in the United States. We, therefore, undertook a prospective study to determine the incidence of awareness with recall during general anesthesia in the United States. This is a prospective, nonrandomized descriptive cohort study that was conducted at seven academic medical centers in the United States. Patients scheduled for surgery under general anesthesia were interviewed in the postoperative recovery room and at least a week after anesthesia and surgery by using a structured interview. Data from 19,575 patients are presented. A total of 25 awareness cases were identified (0.13% incidence). These occurred at a rate of 1–2 cases per 1000 patients at each site. Awareness was associated with increased ASA physical status (odds ratio, 2.41; 95% confidence interval, 1.04–5.60 for ASA status III–V compared with ASA status I–II). Age and sex did not influence the incidence of awareness. There were 46 additional cases (0.24%) of possible awareness and 1183 cases (6.04%) of possible intraoperative dreaming. The incidence of awareness during general anesthesia with recall in the United States is comparable to that described in other countries. Assuming that approximately 20 million anesthetics are administered in the United States annually, we can expect approximately 26,000 cases to occur each year.

Awareness During Anesthesia

MEMORY is not a single entity. Current classification distinguishes between two types: explicit, or conscious memory, and implicit, or unconscious memory. Explicit memory refers to the conscious recollection of previous experiences. Implicit memory, by contrast, refers to changes in performance or behavior that are produced by previous experiences but without any conscious recollection of those experiences.’ Explicit memory is equivalent to “remembering” (e.g., can you remember what you did last Tuesday evening?). In the case of an anesthetized patient, one might ask the patient in the postoperative period “can you remember hearing any words or sounds during your operation?” (i.e., a recall test) or “which of the following words were played to you during surgery?” (a recognition test). As an example of implicit memory, consider the following scenario. Patients were exposed during anesthesia to a list of words containing the word “pension. ” Postoperatively, when they were presented with the three-letter word stem “PEN-” and were asked to supply the first word that came to their minds beginning with those letters, they gave the word “pension” more often than “pencil” or “peninsula” or others. The term “awareness” will be used to describe explicit memory during anesthesia.

Awareness during anesthesia [7] (multiple letters)

MEMORY is not a single entity. Current classification distinguishes between two types: explicit, or conscious memory, and implicit, or unconscious memory. Explicit memory refers to the conscious recollection of previous experiences. Implicit memory, by contrast, refers to changes in performance or behavior that are produced by previous experiences but without any conscious recollection of those experiences.’ Explicit memory is equivalent to “remembering” (e.g., can you remember what you did last Tuesday evening?). In the case of an anesthetized patient, one might ask the patient in the postoperative period “can you remember hearing any words or sounds during your operation?” (i.e., a recall test) or “which of the following words were played to you during surgery?” (a recognition test). As an example of implicit memory, consider the following scenario. Patients were exposed during anesthesia to a list of words containing the word “pension. ” Postoperatively, when they were presented with the three-letter word stem “PEN-” and were asked to supply the first word that came to their minds beginning with those letters, they gave the word “pension” more often than “pencil” or “peninsula” or others. The term “awareness” will be used to describe explicit memory during anesthesia.