Anesthesia awareness

Bispectral index (BIS)-guided anesthesia with Aspect Medical's BIS Quatro Sensor does not lower the incidence of anesthesia awareness or reduce administration of volatile anesthetic gases compared with end-tidal anesthetic gas (ETAG) anesthesia, according to results of a 2,000-patient randomized study at Washington University, St. Louis, published in the March 13 New England Journal of Medicine. The results appear to contradict those of the 2,503-patient Australian B-Aware study, in which BIS reduced awareness by 82% compared to "standard clinical practice" (1"The Gray Sheet" Nov. 3, 2003, p. 26). "Reliance on BIS technology may provide practitioners with a false sense of security about the reduction in the risk of anesthesia awareness," authors Michael Avidan, et al., warn. Scott Kelley, M.D., Aspect Medical's medical director, maintains that the Washington University study did not show the same benefits of BIS as the earlier B-Aware trial because it used ETAG, instead of standard therapy, as the control. "The ETAG-guided protocol used in the NEJM study instructed the anesthesia professionals to use a certain amount of inhaled anesthetics and audible alarms set at the minimum level. This is not how anesthesia professionals routinely practice," said Kelley. "We would expect that a protocol which provides significant amounts of volatile anesthesia would produce a low incidence of awareness in these patients.