Thursday, October 27, 2005

Anesthesiology Group: No Widespread Use of Brain Devices Needed

Filed under: Anesthesiology , Critical Care

The American Society of Anesthesiologists (ASA) has once again decided not to recommend widespread use of "brain function monitoring devices" as necessary tools to prevent intraoperative awareness under general anesthesia. The Task Force of the ASA has just published a practice advisory to help anesthesiologists deal with this serious complication of general anesthesia. The news is indeed a blow to manufacturers of these devices, despite their positive spin press releases.

Here is the explanation from the ASA:

Brain function monitoring devices, made by a handful of companies, use processed electroencephalographic data to assign a numeric value to a patient's depth of sedation. One application for which they are marketed is to help minimize the risk of intraoperative awareness.

The report recognizes the devices as a possible tool for monitoring selected patients, but concludes that the decision to use this emerging technology should be made on a case-by-case basis by the individual practitioner.

"There is still much to be discovered about how these devices work, and in which situations they are best applied," Dr. Guidry said. "We are interested in following their continued evolution and to conducting further research in this area. Meanwhile, brain function monitors are an option to be used when the anesthesiologist deems it appropriate, just as he or she makes choices about specific drugs, dosages, warming devices, and other types of monitors depending on the individual patient."

From an historical perspective, ASA's approach to these monitors is consistent with its approach to other types of equipment used by anesthesiologists. For example, capnographs and pulse oximeters are widely used today to monitor surgical patients' breathing and blood oxygen levels. Yet language encouraging their use in ASA standards and guidelines did not happen overnight; it was strengthened gradually as the devices' usefulness, reported by anesthesiologists and researchers, became more evident.

One also has to recognize the fundamental difference between capnographs, pulse oximeters, and brain function monitoring devices, such as the pictured BIS monitor of Aspect Medical Systems. While capnographs and pulse oximeters calculate physically measurable values (partial pressure of CO2; percentage of hemoglobin saturation), BIS Monitor and others cook up a single number through proprietary secret algorithms. The secrecy of how the monitor translates information from the electroencephalogram (EEG) into a single number will make it even more difficult to popularize such devices. After all, physicians are scientists, and naturally have reservations about the data from a black box. As for us, we'll take BIS anytime someone passes gas at us.

More at the WaPo...

The BIS technology...

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