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, the University of Chicago and the University of Manitoba in Winnipeg.
Unintended intraoperative awareness, also known as anesthesia awareness, occurs when a patient becomes aware during surgery and remembers being in pain or feeling distress during the operation. Between one in 500 and one in 1,000 surgery patients experience awareness during anesthesia. Those with such memories often need psychological help, and some even develop post-traumatic stress disorder.
“We were testing whether a protocol based on a device called a bispectral index or BIS monitor, which measures brain activity to determine how deeply a patient is anesthetized, could more effectively prevent intraoperative awareness than an alternative approach that measures anesthetic levels in a patient’s breath,” says first author Michael S. Avidan, MB, BCh, professor of anesthesiology.
The study, called the international BIS or Anesthetic Gas to Reduce Explicit Recall (BAG-RECALL) trial, focused on a subset of patients at high risk for awareness. They include patients undergoing cardiac surgery, those who regularly consume large amounts of alcohol or take sedatives or certain types of pain-killing drugs. Patients who previously have had episodes of awareness also are at high risk.
Because the study showed that the structured approach to using BIS monitoring is no better than one based on measuring exhaled anesthetics, Avidan and co-investigator Alex S. Evers, MD, the Henry E. Mallinckrodt Professor and head of the Department of Anesthesiology, say the current, widespread use of the bispectral index in operating rooms should be re-examined.
“New technology has to prove its superiority over more cost-effective alternatives,” Avidan explains. “Our trial showed, compellingly, that the protocol based on the bispectral index is not superior.”