Abstract

In general anesthesia, a “cocktail” of drugs renders a patient unconscious, in what has been called a “controlled coma”. Various measures of patient awareness involve overt behavior, autonomic nervous system activity, processed EEG, and event‐related potentials. The incidence of intraoperative awareness is very low, but anecdotal reports suggest that patients might process surgical events unconsciously, leading to unconscious postoperative memories. Careful experimental studies show that priming effects, similar to those observed in implicit memory, can be spared even in the absence of conscious recollection, an outcome which indicates that unconscious perception can occur even in clinically adequate general anesthesia. Deeper planes of amnesia, however, appear to abolish both explicit and implicit perception.