General anesthesia, although an obvious boon to modern surgery, fails to completely knock out a small percentage of patients, many of whom go on to develop post-traumatic stress disorder from the pain, horror and helplessness of the experience.

A study of 16 of these so-called "awareness" patients found that more than half of them had PTSD, while none of the 10 patients who were not awake during their surgery developed the psychiatric disorder.

Awareness under general anesthesia is estimated to happen to 0.2 percent to 0.7 percent of surgery patients, affecting between 40,000 and 140,000 patients a year.

"Most post-awareness subjects reported lapsing in and out of consciousness, picking up fragments of the surgery, conversations and bodily sensation while struggling to move, escape and communicate. These memories reappeared later as vivid images, sensations, isolated thoughts and intense emotions that are characteristic of PTSD," says lead author Jane E. Osterman, M.D., M.S., of Boston University School of Medicine.

The subjects in this study reported an inability to communicate during their surgery as well as intense feelings of helplessness, terror, feeling unsafe, fear of pain, pain and paralysis. They also reported that they had felt abandoned or betrayed by their doctors and nurses.

Following surgery, the awareness patients continued to suffer from feelings of being unsafe, terror, helplessness, the inability to communicate, betrayal and abandonment.

The study is published in the July-August issue of General Hospital Psychiatry.

By comparison, control subjects had only vague memories of the circumstances of their surgery, no memory of the surgical procedure itself and reported only mild feelings of helplessness, fear of pain and pain.

The difference between memory recall in the awareness and the control subjects memories is consistent with previous reports which show that nontraumatic memories tend to degrade over time, while memories of traumatic events remain vivid, says Osterman.

PTSD resulting from awareness during surgery can lead to a state in which patients described themselves as "the living dead" or "zombies." This dissociation may be a product of patients’ attempts to mentally escape during surgery or likened to an out-of-body experience during or after surgery.

"Patients suffering from dissociation often appear calm and unaffected by the traumatic event and do not attract attention on busy surgical services. Their heart rates, rather than elevated, are often reduced….Patients with post-awareness dissociation are unlikely to be identified as having suffered awareness. Instead, they may be considered merely slightly ‘groggy,’" the investigators say, helping to explain why PTSD has not been identified in these patients before.

This is especially problematic because, as has been seen in PTSD caused by other types of trauma, these patients will avoid doctors and hospitals so that they will not be reminded of the traumatic experience.

The study was partially funded by Aspect Medical Center, Inc., Natick, Massachusetts.

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General Hospital Psychiatry is a peer-reviewed research journal published bimonthly by Elsevier Science. For information about the journal, contact Don R. Lipsitt, MD, at (617) 499-5008.