Under Anesthesia, Yet Aware

Brain monitors, while valuable, are no substitute for a skilled practitioner

By Bernadine Healy M.D.

Posted March 12, 2008

It’s easy to be squeamish about going under the knife, especially if you fear that the anesthesia might forsake you. Well over 20,000 people a year, by some estimates, experience “anesthesia awareness,” in which they awaken during the operation, paralyzed but later able to bear witness to operating room chatter, the clanking of instruments, and the sucking, sawing, or slicing sounds of the surgical team at work. Most of the time (but not always), there is no physical pain and the patient later recalls only fleeting awareness. But sometimes the event leads to post-traumatic stress disorder and lingering terror about hospitals and operations. How disappointing, then, that a study just out in the New England Journal of Medicine finds little value in a technology that might prevent this unhappy complication.

The technology, called the BIS (short for “bispectral index”) monitor, measures the brain’s electrical activity and comes up with a single number to represent the level of consciousness, ranging from 100 for fully awake to 0, no brain activity. Amid growing recognition that intraoperative awareness is a worldwide phenomenon, many countries, including the United States, have witnessed a proliferation in the use of such monitors to better titrate drugs, with reported success. But this new trial from the School of Medicine at Washington University in St. Louis of 1,941 patients at high risk for awareness showed no added value when BIS was used along with standard practice.

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