Anesthesia awareness

Blog Post by George Mashour, University of Michigan School of Medicine

Anesthesia awareness” refers to consciousness and explicit memory of surgical events.  This complication is thought to occur in approximately 1-2 cases/1000 and can range from a transient auditory perception to the experience of being fully awake, in pain, and chemically paralyzed. Risk factors for this event traditionally include certain cardiac procedures, emergency cases with blood loss, emergency cesarean section, difficult airway management, and cases with total intravenous anesthetic.  Many of these cases (cardiac, trauma, cesarean section) represent situations in which giving adequate anesthesia could be potentially life-threatening.  Other causes include resistance to anesthetics, machine or equipment malfunction, and human error.  The experience of anesthesia awareness can be psychologically devastating.  In a new study by Dr. Kate Leslie and colleagues (Anesthesia & Analgesia, March issue), 5 of 7 awareness patients identified in a larger study met criteria for post-traumatic stress disorder.  The role of brain monitoring for the prevention of awareness is still unclear; several large studies are ongoing to determine the value of one such monitor.  Part of the difficulty of detecting awareness in the surgical setting relates to our limited understanding of the neural correlates of consciousness.  As we develop more sophisticated knowledge of the mechanisms of both consciousness and anesthesia, improved monitoring capabilities may become available.  In the meantime, recognizing high risk cases and vigilance on the part of the anesthesia provider is the first line of defense.    

Now published in the US, and available from the UK and Europe in March 2010, Consciousness, Awareness, and Anesthesia, edited by George Mashour, is a fascinating insight into both the scientific problem of consciousness and the clinical problem of awareness during general anesthesia.

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