Anesthetic Amnesia: The Forgotten Importance of Forgetting?

There is increasing evidence that the impairment of consciousness by anesthetic drugs does not always lead to its complete absence and that the loss of subjective experience with anesthesia may at times be an illusion created by amnesia. However, the study of how anesthetic drugs cause amnesia, and importantly how they fail, has received less attention than the other cardinal properties of anesthesia. There is no reliable biomarker to determine the adequacy of pharmacologic amnesia in real time. Anesthetic drugs can influence all stages of memory formation and recall, and their amnestic effects are dissociable from their hypnotic effects; for example, propofol has potent specific amnestic potential, whereas dexmedetomidine is a pure hypnotic. Posttraumatic stress disorder cluster symptoms, which constitute a disorder of amygdala-centered memory systems, are commonly related to surgical memories under both general anesthesia and procedural sedation and need to be better understood and managed.