title: Alerting thresholds for the prevention of intraoperative awareness with explicit recall: a secondary analysis of the Michigan Awareness Control Study.
abstract: BACKGROUND
  Intraoperative awareness with explicit recall is a potentially devastating complication of surgery that has been attributed to low anaesthetic concentrations in the vast majority of cases. Past studies have proposed the determination of an adequate dose for general anaesthetics that could be used to alert providers of potentially insufficient anaesthesia. However, there have been no systematic analyses of appropriate thresholds to develop population-based alerting algorithms for preventing intraoperative awareness.
  
  
  OBJECTIVE
  To identify a threshold for intraoperative alerting that could be applied for the prevention of awareness with explicit recall.
  
  
  METHODS
  Secondary analysis of a randomised controlled trial (Michigan Awareness Control Study).
  
  
  METHODS
  Three hospitals at a tertiary care centre in the USA.
  
  
  METHODS
  Unselected patients presenting for surgery under general anaesthesia.
  
  
  METHODS
  Alerts based on end-tidal anaesthetic concentration or bispectral index values.
  
  
  METHODS
  Using case and outcomes data from the primary study, end-tidal anaesthetic concentration and bispectral index values were analysed using Youden's index and c-statistics derived from a receiver operating characteristic curve to determine a specific alerting threshold for the prevention of awareness.
  
  
  RESULTS
  No single population-based threshold that maximises sensitivity and specificity could be identified for the prevention of intraoperative awareness, using either anaesthetic concentration or bispectral index values. The c-statistic for anaesthetic concentration was 0.431 ± 0.046, and 0.491 ± 0.056 for bispectral index values.
  
  
  CONCLUSIONS
  We could not derive a single population-based alerting threshold for the prevention of intraoperative awareness using either anaesthetic concentration or bispectral index values. These data indicate a need to move towards individualised alerting strategies in the prevention of intraoperative awareness.
  
  
  BACKGROUND
  Primary trial registration (Michigan Awareness Control Study) ClinicalTrials.gov identifier: NCT00689091.
authors.affiliation: From the Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan (AMS, SK, KKT, JCV, GAM), Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (MSA) and Department of Biomedical Engineering, Wayne State University, Detroit, Michigan, USA (JMC).
authors.forename: Amy M
authors.initials: AM
authors.lastname: Shanks
authors.forename: Michael S
authors.initials: MS
authors.lastname: Avidan
authors.forename: Sachin
authors.initials: S
authors.lastname: Kheterpal
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Tremper
authors.forename: John C
authors.initials: JC
authors.lastname: Vandervest
authors.forename: John M
authors.initials: JM
authors.lastname: Cavanaugh
authors.forename: George A
authors.initials: GA
authors.lastname: Mashour
mesh_terms: D000768:Anesthesia, General / Q000009:adverse effects*; D004569:Electroencephalography / Q000379:methods / Q000592:standards; D005260:Female; D006801:Humans; D058926:Intraoperative Awareness / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control*; D008297:Male; D050316:Medical Order Entry Systems / Q000592:standards*; D008824:Michigan / Q000453:epidemiology; D016343:Monitoring, Intraoperative / Q000379:methods / Q000592:standards*