• George A Mashour, Amy Shanks, Kevin K Tremper, Sachin Kheterpal, Christopher R Turner, Satya Krishna Ramachandran, Paul Picton, Christa Schueller, Michelle Morris, John C Vandervest, Nan Lin, and Michael S Avidan.
• Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan 48109-5048, USA. gmashour@umich.edu
• Anesthesiology. 2012 Oct 1;117(4):717-25.

BackgroundIntraoperative awareness with explicit recall occurs in approximately 0.15% of all surgical cases. Efficacy trials based on the Bispectral Index® (BIS) monitor (Covidien, Boulder, CO) and anesthetic concentrations have focused on high-risk patients, but there are no effectiveness data applicable to an unselected surgical population.MethodsWe conducted a randomized controlled trial of unselected surgical patients at three hospitals of a tertiary academic medical center. Surgical cases were randomized to alerting algorithms based on either BIS values or anesthetic concentrations. The primary outcome was the incidence of definite intraoperative awareness; prespecified secondary outcomes included postanesthetic recovery variables.ResultsThe study was terminated because of futility. At interim analysis the incidence of definite awareness was 0.12% (11/9,376) (95% CI: 0.07-0.21%) in the anesthetic concentration group and 0.08% (8/9,460) (95% CI: 0.04-0.16%) in the BIS group (P = 0.48). There was no significant difference between the two groups in terms of meeting criteria for recovery room discharge or incidence of nausea and vomiting. By post hoc secondary analysis, the BIS protocol was associated with a 4.7-fold reduction in definite or possible awareness events compared with a cohort receiving no intervention (P = 0.001; 95% CI: 1.7-13.1).ConclusionThis negative trial could not detect a difference in the incidence of definite awareness or recovery variables between monitoring protocols based on either BIS values or anesthetic concentration. By post hoc analysis, a protocol based on BIS monitoring reduced the incidence of definite or possible intraoperative awareness compared with routine care.

This article appears in the collection: Post-operative awareness monitoring & prevention.

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