Prevention of intraoperative awareness in a high-risk surgical population.

Background: Unintended intraoperative awareness, which occurs when general anesthesia is not achieved or maintained, affects up to 1% of patients at high risk for this complication. We tested the hypothesis that a protocol incorporating the electroencephalogram-derived bispectral index (BIS) is superior to a protocol incorporating standard monitoring of end-tidal anesthetic-agent concentration (ETAC) for the prevention of awareness.

Methods: We conducted a prospective, randomized, evaluator-blinded trial at three medical centers.