St. Louis researchers look at cheaper anesthesia awareness method

Monday, September 5, 2011 | 3:47 p.m. CDT

ST. LOUIS — Surgery patients who sometimes appear to be sedated but are awake for the procedures should be measured with a new brain wave-monitoring device because a common method used to prevent what's known as anesthesia awareness is not always effective, researchers in St. Louis said.

Between 1-in-500 and 1-in-1,000 patients remember pain, feeling paralyzed or hearing something stressful during their surgeries, The St. Louis Post-Dispatch reports. Some need psychological help or develop post-traumatic stress disorder.

Researchers from Washington University School of Medicine and two other universities found that a device that monitors brain activity known as the bispectral index is no more effective than a more simple and less expensive method of measuring anesthetic concentration levels in the breath.

Anesthesia awareness is more common in some patients — those undergoing cardiac surgery or who regularly consume large amounts of alcohol or take certain medications.

Washington University anesthesiology professor Michael Avidan led the study of 6,000 high-risk surgical patients in a study published Aug. 18 in the New England Journal of Medicine. It confirmed results from a smaller study led by Avidan in 2008.

The bispectral index, known as a BIS monitor, was approved by the Food and Drug Administration in 1996. It is available in most U.S. operating rooms.

A 2004 study found that using the device could reduce anesthesia awareness among patients by 82 percent. But that study compared the patients to those who received no prevention method. Avidan's studies compared the brain wave-measuring method to monitoring the concentration of exhaled anesthetic agents and sounding alerts when the exhaled anesthetics were too high or low.

"New technology has to prove its superiority over more cost-effective alternatives," Avidan said. "Our trial showed, compellingly, that the protocol based on the bispectral index is not superior."

Avidan said the findings could prompt the American Society of Anesthesiologists to adopt prevention guidelines based on the methods used in the study.

Researchers said a new brain wave-monitoring method that provides real-time measurement should be explored. The bispectral index can take as long as one minute to interpret a patient's brain waves.

"It's a really good idea. We should be trying to monitor the brain directly rather than monitoring measures that indirectly indicate whether a person in anesthetized or unaware," Avidan said.

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