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Awake-During-Surgery Device Worth a Nod?

Study Challenges Benefit of BIS, a Brain Monitor That Helps Doctors Detect When Patients Are Waking

Does BIS Brain Monitor Cut Waking During Surgery? continued...

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."

But Scott D. Kelley, MD, vice president and medical director for Aspect Medical Systems Inc., sees the Avidan study much differently.

Kelley notes that the rate of anesthesia awareness seen in the study was about two per 1,000 patients -- 10 times lower than would be expected for these high-risk patients. This, he says, shows that BIS monitoring does indeed reduce waking during surgery.

"What they used as a control protocol is not standard practice," Kelley tells WebMD. "I went through 40 operating rooms yesterday, and not a single one had one of these exhaled gas alarms turned on. So what the control group received in the Avidan study was not the kind of care the average patient can expect to get. I don't want patients to believe that starting tomorrow they will get same kind of care the control group got in the Avidan study. And are there other consequences to that kind of treatment care? We don't know. Their protocol has not been validated in clinical trials."

Kelley also brushes aside Orser's criticism of what the Aspect BIS monitor measures.

"There are clearly deep structures within the brain where some of these control centers for consciousness exist. But as clinicians trying to take care of a wide number of patients, what is important here is the surface reading of the electroencephalogram," he says. "We have broad clinical experience in more than 25 million patients. This technology being adopted by so many doctors works, and works well, and has patient impact. I believe I, as an anesthesiologist, and my patients benefit greatly from this technology."

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