Bispectral Index Guided Anesthesia Not Superior

Fewer cases of intraoperative awareness with standard end-tidal anesthetic-agent concentration

WEDNESDAY, Aug. 17 (HealthDay News) -- Intraoperative anesthesia guided by a protocol incorporating the electroencephalogram derived bispectral index (BIS) is not superior to a protocol incorporating standard monitoring of end-tidal anesthetic-agent concentration (ETAC) for the prevention of intraoperative awareness, according to a study published in the Aug. 18 issue of the New England Journal of Medicine.

Michael S. Avidan, M.B., B.Ch., from the Washington University School of Medicine in St. Louis, and colleagues investigated whether a protocol incorporating the electroencephalogram-derived BIS index is superior to the one incorporating standard monitoring of ETAC for the prevention of unintended intraoperative awareness after anesthesia. A total of 2,861 patients at high risk for awareness were randomly assigned to BIS and 2,852 were assigned to ETAC, followed by a post-operative interview. The protocol consisted of audible alerts (<40 and >60 for BIS on a scale of 0 to 100, and <0.7 and >1.3 minimum alveolar concentration for ETAC), structured education, and checklists. One-sided Fisher's exact test was used to assess the superiority of the BIS protocol.

The investigators found that seven and two patients in the BIS and ETAC groups, respectively, had intraoperative awareness (a difference of 0.17 percent). Compared to eight cases of definite or possible intraoperative awareness in the ETAC group, 19 cases occurred in the BIS group (difference of 0.38 percent). The amount of anesthesia administered or the rate of major postoperative adverse outcomes were not different between the groups. The results demonstrated no superiority of BIS protocol over ETAC.

"The superiority of the BIS protocol was not established; contrary to expectations, fewer patients in the ETAC group than in the BIS group experienced awareness," the authors write.

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