title: Prevention of intraoperative awareness with explicit recall in an unselected surgical population: a randomized comparative effectiveness trial.
abstract: BACKGROUND
  Intraoperative 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.
  
  
  METHODS
  We 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.
  
  
  RESULTS
  The 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).
  
  
  CONCLUSIONS
  This 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.
authors.affiliation: Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan 48109-5048, USA. gmashour@umich.edu
authors.forename: George A
authors.initials: GA
authors.lastname: Mashour
authors.forename: Amy
authors.initials: A
authors.lastname: Shanks
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Tremper
authors.forename: Sachin
authors.initials: S
authors.lastname: Kheterpal
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Turner
authors.forename: Satya Krishna
authors.initials: SK
authors.lastname: Ramachandran
authors.forename: Paul
authors.initials: P
authors.lastname: Picton
authors.forename: Christa
authors.initials: C
authors.lastname: Schueller
authors.forename: Michelle
authors.initials: M
authors.lastname: Morris
authors.forename: John C
authors.initials: JC
authors.lastname: Vandervest
authors.forename: Nan
authors.initials: N
authors.lastname: Lin
authors.forename: Michael S
authors.initials: MS
authors.lastname: Avidan
mesh_terms: D000328:Adult; D000465:Algorithms; D000762:Anesthesia Recovery Period; D000768:Anesthesia, General; D000777:Anesthetics / Q000008:administration & dosage; D056805:Consciousness Monitors; D005260:Female; D006801:Humans; D058926:Intraoperative Awareness / Q000453:epidemiology / Q000517:prevention & control*; D008297:Male; D011939:Mental Recall / Q000502:physiology; D008875:Middle Aged; D017211:Treatment Failure; D016896:Treatment Outcome
chemical_list: D000777:Anesthetics