Awake-During-Surgery Device Worth a Nod?
Study Challenges Benefit of BIS, a Brain Monitor That Helps Doctors Detect When Patients Are Waking
WebMD News Archive
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
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
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
"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