title: Prevention of intraoperative awareness in a high-risk surgical population.
abstract: 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. We randomly assigned 6041 patients at high risk for awareness to BIS-guided anesthesia (with an audible alert if the BIS value was <40 or >60, on a scale of 0 to 100, with 0 indicating the suppression of detectable brain electrical activity and 100 indicating the awake state) or ETAC-guided anesthesia (with an audible alert if the ETAC was <0.7 or >1.3 minimum alveolar concentration). In addition to audible alerts, the protocols included structured education and checklists. Superiority of the BIS protocol was assessed with the use of a one-sided Fisher's exact test.
  
  
  RESULTS
  A total of 7 of 2861 patients (0.24%) in the BIS group, as compared with 2 of 2852 (0.07%) in the ETAC group, who were interviewed postoperatively had definite intraoperative awareness (a difference of 0.17 percentage points; 95% confidence interval [CI], -0.03 to 0.38; P=0.98). Thus, the superiority of the BIS protocol was not demonstrated. A total of 19 cases of definite or possible intraoperative awareness (0.66%) occurred in the BIS group, as compared with 8 (0.28%) in the ETAC group (a difference of 0.38 percentage points; 95% CI, 0.03 to 0.74; P=0.99), with the superiority of the BIS protocol again not demonstrated. There was no difference between the groups with respect to the amount of anesthesia administered or the rate of major postoperative adverse outcomes.
  
  
  CONCLUSIONS
  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. (Funded by the Foundation for Anesthesia Education and Research and others; BAG-RECALL ClinicalTrials.gov number, NCT00682825.).
authors.affiliation: Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA. avidanm@anest.wustl.edu
authors.forename: Michael S
authors.initials: MS
authors.lastname: Avidan
authors.forename: Eric
authors.initials: E
authors.lastname: Jacobsohn
authors.forename: David
authors.initials: D
authors.lastname: Glick
authors.forename: Beth A
authors.initials: BA
authors.lastname: Burnside
authors.forename: Lini
authors.initials: L
authors.lastname: Zhang
authors.forename: Alex
authors.initials: A
authors.lastname: Villafranca
authors.forename: Leah
authors.initials: L
authors.lastname: Karl
authors.forename: Saima
authors.initials: S
authors.lastname: Kamal
authors.forename: Brian
authors.initials: B
authors.lastname: Torres
authors.forename: Michael
authors.initials: M
authors.lastname: O'Connor
authors.forename: Alex S
authors.initials: AS
authors.lastname: Evers
authors.forename: Stephen
authors.initials: S
authors.lastname: Gradwohl
authors.forename: Nan
authors.initials: N
authors.lastname: Lin
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Palanca
authors.forename: George A
authors.initials: GA
authors.lastname: Mashour
mesh_terms: D000328:Adult; D000368:Aged; D000768:Anesthesia, General; D018685:Anesthetics, Inhalation / Q000032:analysis*; D056805:Consciousness Monitors; D004569:Electroencephalography; D005260:Female; D006801:Humans; D058926:Intraoperative Awareness / Q000453:epidemiology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D011183:Postoperative Complications; D011446:Prospective Studies; D011650:Pulmonary Alveoli / Q000737:chemistry*; D012307:Risk Factors; D016037:Single-Blind Method
chemical_list: D018685:Anesthetics, Inhalation