Awareness during anesthesia implies that during a period of intended general anesthesia, the brain is aroused by stimuli that are stored in memory for future explicit recall. It has an estimated incidence between 0.007-0.91. Thus, with over 20 million general anesthetics performed yearly in the United States, the occurrence can be striking. Consequently, in 2004, The Joint Commission issued an alert stating that anesthesia awareness is an "under-recognized and under-treated" problem in health care organizations. The incidence in trauma patients is even more alarming and has been shown to range from 11-43% in various studies.
When discussing and describing awareness, there are several important terms that require defining:
- Consciousness describes a state in which a patient is able to process information from his or her surroundings.
- Unconsciousness results from the interruption in cortical communication and loss of integration that is needed to process information from one’s surroundings.
- General anesthesia is a drug-induced state that produces unconsciousness.
- Perceptions while under anesthesia are most commonly auditory (sounds, conversations) and feelings of fear, helplessness, pain, anxiety, and paralysis. Less commonly, they include visual perception, memory of intubation, and feeling the operation without pain.
- Memories are often described as explicit or implicit. Explicit memory, or recall, is the conscious recollection of stored memories, whereas implicit memory describes changes in performance or behavior that are produced by previous experiences but without any conscious recollection of those experiences
- Amnesia is the absence of recall. Patients may follow commands as they are emerging from anesthesia or during “wake-up” testing (e.g. spinal surgery to test the integrity of nerves), but not have conscious recall (explicit memory).
- “Awake paralysis” is a term used to describe errors in the administration of neuromuscular blocking agent resulting in paralysis of the unanesthetized or incompletely anesthetized patient.
More Answers from Nina Radcliff, MD