Study queries utility of brainwave surgery device

BOSTON (Reuters) - A widely used device that employs brainwaves to help doctors prevent patients from waking up during surgery is no more effective than an older, far less costly technique, researchers said on Wednesday.

Their study of nearly 2,000 patients showed the BIS device, made by Aspect Medical Systems Inc., did not help doctors prevent any more patients from waking up while under inhaled anesthesia.

"Our findings do not support routine BIS monitoring as part of standard practice," Michael Avidan of Washington University School of Medicine in St. Louis and colleagues wrote in their report, published in the New England Journal of Medicine.

"Reliance on BIS technology may provide patients and health care practitioners with a false sense of security about the reduction in the risk of anesthesia awareness," they added. Anethesia awareness occurs when patients have some degree of consciousness.

"If BIS monitoring were routinely applied to all patients in the United States receiving general anesthesia, the cost of disposable electrodes alone would exceed $360 million annually."

As many as 40,000 of the 21 million patients undergoing surgery in the United States may experience inadequate anesthesia, leading to anxiety and even post-traumatic stress disorder if patients regain consciousness, according to the Joint Commission on Accreditation of Healthcare Organizations.

Aspect's Bispectral Index or BIS system assesses brainwaves to help doctors accurately gauge unconsciousness and adjust anethesia. It is used in about 60 percent of U.S. operating rooms and is the only system of its kind approved by the U.S. Food and Drug Administration.

WIDESPREAD USE

"There had only been a single large randomized study suggesting it worked, and yet it was enjoying widespread adoption throughout operating rooms in the U.S. and throughout the world," said Avidan.

So his group looked for evidence of anesthesia awareness in 967 patients monitored by the BIS system and 974 people in a control group that used a long-established monitoring method -- standard in new anesthesia machines -- that measures the concentration of anesthesia gas exhaled by the patient.

"The addition of the BIS-guided protocol did not reduce the frequency of definite or possible awareness," Dr. Beverly Orser of the University of Toronto wrote in a commentary.

"Specifically, four patients, two in each group, had definite awareness, and five additional patients (four in the BIS group and one in the control group) had possible awareness."

Aspect's medical director, Dr. Scott Kelley, said the Avidan study did not reflect real-world conditions because doctors do not usually measure exhaled gases, he said.

Kelley said the Avidan study also failed to assess other important benefits of BIS technology, such as comfort and better recovery from anesthesia.

Aspect says that when its system is used, one-fifth less anesthetic is needed, which speeds recovery and reduces side effects.

"It is important to emphasize that the results of this trial should not be extrapolated to patients receiving total intravenous anesthesia, which is considered to be a risk factor for anesthesia awareness," Avidan's team wrote.

"Indeed, BIS monitoring may be useful during total intravenous anesthesia, since it is not presently possible to monitor the blood concentrations of anesthetic agents continuously."

Intravenous sedation is more common in Europe.

(Editing by Maggie Fox and Cynthia Osterman)