title: Bispectral index monitoring, duration of bispectral index below 45, patient risk factors, and intermediate-term mortality after noncardiac surgery in the B-Unaware Trial.
abstract: BACKGROUND
  Postoperative mortality has been associated with cumulative anesthetic duration below an arbitrary processed electroencephalographic threshold (bispectral index [BIS] <45). This substudy of the B-Unaware Trial tested whether cumulative duration of BIS values lower than 45, cumulative anesthetic dose, comorbidities, or intraoperative events were independently associated with postoperative mortality.
  
  
  METHODS
  The authors studied 1,473 patients (mean ± SD age, 57.9 ± 14.4 yr; 749 men) who underwent noncardiac surgery at Barnes-Jewish Hospital in St. Louis, Missouri. Multivariable Cox regression analysis was used to determine whether perioperative factors were independently associated with all-cause mortality.
  
  
  RESULTS
  A total of 358 patients (24.3%) died during a follow-up of 3.2 ± 1.1 yr. There were statistically significant associations among various perioperative risk factors, including malignancy and intermediate-term mortality. BIS-monitored patients did not have lower mortality than unmonitored patients (24.9 vs. 23.7%; difference = 1.2%, 95% CI, -3.3 to 5.6%). Cumulative duration of BIS values less than 45 was not associated with mortality (multivariable hazard ratio, 1.03; 95% CI, 0.93-1.14). Increasing mean and cumulative end-tidal anesthetic concentrations were not associated with mortality. The multivariable Cox regression model showed a good discriminative ability (c-index = 0.795).
  
  
  CONCLUSIONS
  This study found no evidence that either cumulative BIS values below a threshold of 40 or 45 or cumulative inhalational anesthetic dose is injurious to patients. These results do not support the hypothesis that limiting depth of anesthesia either by titration to a specific BIS threshold or by limiting end-tidal volatile agent concentrations will decrease postoperative mortality.
authors.affiliation: Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri, USA. miklos.kertai@duke.edu
authors.forename: Miklos D
authors.initials: MD
authors.lastname: Kertai
authors.forename: Ben J A
authors.initials: BJ
authors.lastname: Palanca
authors.forename: Nirvik
authors.initials: N
authors.lastname: Pal
authors.forename: Beth A
authors.initials: BA
authors.lastname: Burnside
authors.forename: Lini
authors.initials: L
authors.lastname: Zhang
authors.forename: Furqaan
authors.initials: F
authors.lastname: Sadiq
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Finkel
authors.forename: Michael S
authors.initials: MS
authors.lastname: Avidan
mesh_terms: D000368:Aged; D000769:Anesthesia, Inhalation / Q000009:adverse effects*; D018685:Anesthetics, Inhalation / Q000009:adverse effects*; D002423:Cause of Death; D056805:Consciousness Monitors; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D058926:Intraoperative Awareness / Q000517:prevention & control; D007432:Intraoperative Period; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D019990:Perioperative Care; D059035:Perioperative Period / Q000401:mortality*; D011183:Postoperative Complications / Q000401:mortality; D011184:Postoperative Period; D011650:Pulmonary Alveoli / Q000378:metabolism; D012044:Regression Analysis; D012307:Risk Factors; D012959:Socioeconomic Factors; D013514:Surgical Procedures, Operative / Q000401:mortality*
chemical_list: D018685:Anesthetics, Inhalation