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Brain & Nervous System Health Center

Awake-During-Surgery Device Worth a Nod?

Study Challenges Benefit of BIS, a Brain Monitor That Helps Doctors Detect When Patients Are Waking
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Does BIS Brain Monitor Cut Waking During Surgery? continued...

In 2004, a clinical trial suggested that the device cut the risk of anesthesia awareness among high-risk surgery patients. Driven by media reports of patients who experienced waking during surgery -- and by a frightening Hollywood movie, Awake -- Advent's device became widely used. It's now found in about 60% of all U.S. operating rooms and is used in about 17% of surgeries requiring general anesthesia.

But does the device work better than the standard technique tracking the amount of anesthetic gas a patient exhales? Avidan and colleagues tested this in a new clinical trial that enrolled patients with at least one factor that put them at high risk of anesthesia awareness.

The researchers randomly assigned about 1,000 surgical patients to the Aspect BIS monitor, and about 1,000 patients to standard monitoring (except that an alarm was set to go off when exhaled anesthesia levels dropped below optimal levels).

Four patients experienced anesthesia awareness. Two were in the standard monitoring group. Two were in the group that got BIS monitoring.

"I don't think, presently, the evidence would persuade me that use of technologies like BIS monitoring would reduce the likelihood of anesthesia awareness," Avidan says. "I would still use these monitors, but only in the context of clinical trials. We are doing a 6,000-patient study in high-risk patients. And the University of Michigan is doing a 30,000-patient study. It seems strange to me there should be such a widespread change in practice before we have more compelling evidence than only one trial demonstrating benefit."

An editorial by Beverley A. Orser, MD, PhD, professor of anesthesia and physiology at the University of Toronto, accompanies Avidan and colleagues' report in the March 13 issue of The New England Journal of Medicine. Orser says she is not surprised that the BIS monitor was no better than enhanced anesthesia monitoring at preventing waking during surgery.

"I question the ability of this device to prevent anesthesia awareness because I don't think it is targeting the areas of the brain responsible for this activity," Orser tells WebMD. "We had the device at our center and tried it, and our group did not feel it was something of sufficient value to justify the cost. Our decision as a group was this is not validated enough to use for clinical practice."

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