Anesthesiology researchers have shown that a device approved by the Food and Drug Administration to reduce the risk that patients will recall their surgery does not lower the risk of the problem, known as intraoperative awareness, any more than a less expensive method.
The new study, published Aug. 18 in The New England Journal of Medicine, involved more than 6,000 surgical patients at Washington University School of Medicine in St. Louis, the University of Chicago and the University of Manitoba in Winnipeg.
Called the international BIS or Anesthetic Gas to Reduce Explicit Recall (BAG-RECALL) trial, the multi-center study is the third involving the bispectral index in recent years. A 2004 study found that using BIS monitors could reduce awareness incidence by 82 percent.
Then in 2008, Michael Avidan, MB, BCh, and his colleagues did a second study that followed almost 2,000 surgery patients at Barnes-Jewish Hospital in St. Louis. That study found that using a BIS monitor, which involves placing a disposable sensor on the patient’s forehead to monitor brain activity, was no better at preventing awareness than the less-expensive protocol based on the measurement of end-tidal anesthetic-agent concentration (ETAC), the concentration of anesthetic agents in patients’ exhaled breath.
The new study was designed to resolve whether the BIS protocol did, in fact, confer that clinically meaningful advantage. In the multi-center trial, investigators found that 19 of the 2,861 high-risk surgical patients in the BIS monitor group experienced either definite or possible intraoperative awareness. Among those randomized to the exhaled anesthetic technique, only eight of the 2,852 had intraoperative awareness.
“This study again found that both approaches were probably effective,” says co-investigator Alex S. Evers, MD, the Henry E. Mallinckrodt Professor and head of the Department of Anesthesiology at Washington University School of Medicine. “In many cases, the reason patients may experience awareness is because they do not receive an adequate concentration of anesthetic, so it makes sense to monitor the anesthetic drug levels closely. That’s one reason rigorously monitoring the concentration of drugs with the exhaled agent method appears to be so effective.”
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