General anesthesia is a reversible
state characterized by unconsciousness, analgesia, muscle relaxation, and
depression of reflexes which is achieved by the administration of chemical
agents. As the intensity of surgical stimulation varies during a surgical
procedure, so does the requirement of anesthetic agents. The organ system
effects of anesthetic drugs may limit the amount that can be given safely.
This would, at occasions, create a critical imbalance between anesthetic
requirement and anesthetic drug administration resulting in varying depth
of anesthesia and, ultimately, in awareness. Unintended intraoperative
awareness occurs when a patient can recall some or all of the events
happening during a surgical procedure.