title: BIS-guided anesthesia decreases postoperative delirium and cognitive decline.
abstract: BACKGROUND
  Previous clinical trials and animal experiments have suggested that long-lasting neurotoxicity of general anesthetics may lead to postoperative cognitive dysfunction (POCD). Brain function monitoring such as the bispectral index (BIS) facilitates anesthetic titration and has been shown to reduce anesthetic exposure. In a randomized controlled trial, we tested the effect of BIS monitoring on POCD in 921 elderly patients undergoing major noncardiac surgery.
  
  
  METHODS
  Patients were randomly assigned to receive either BIS-guided anesthesia or routine care. The BIS group had anesthesia adjusted to maintain a BIS value between 40 and 60 during maintenance of anesthesia. Routine care group had BIS measured but not revealed to attending anesthesiologists. Anesthesia was adjusted according to traditional clinical signs and hemodynamic parameters. A neuropsychology battery of tests was administered before and at 1 week and 3 months after surgery. Results were compared with matched control patients who did not have surgery during the same period. Delirium was measured using the confusion assessment method criteria.
  
  
  RESULTS
  The median (interquartile range) BIS values during the maintenance period of anesthesia were significantly lower in the control group, 36 (31 to 49), compared with the BIS-guided group, 53 (48 to 57), P<0.001. BIS-guided anesthesia reduced propofol delivery by 21% and that for volatile anesthetics by 30%. There were fewer patients with delirium in the BIS group compared with routine care (15.6% vs. 24.1%, P=0.01). Although cognitive performance was similar between groups at 1 week after surgery, patients in the BIS group had a lower rate of POCD at 3 months compared with routine care (10.2% vs. 14.7%; adjusted odds ratio 0.67; 95% confidence interval, 0.32-0.98; P=0.025).
  
  
  CONCLUSIONS
  BIS-guided anesthesia reduced anesthetic exposure and decreased the risk of POCD at 3 months after surgery. For every 1000 elderly patients undergoing major surgery, anesthetic delivery titrated to a range of BIS between 40 and 60 would prevent 23 patients from POCD and 83 patients from delirium.
authors.affiliation: Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong. mtvchan@cuhk.edu.hk
authors.forename: Matthew T V
authors.initials: MT
authors.lastname: Chan
authors.forename: Benny C P
authors.initials: BC
authors.lastname: Cheng
authors.forename: Tatia M C
authors.initials: TM
authors.lastname: Lee
authors.forename: Tony
authors.initials: T
authors.lastname: Gin
mesh_terms: D000368:Aged; D000768:Anesthesia, General / Q000009:adverse effects / Q000379:methods*; D044466:Asian People; D003072:Cognition Disorders / Q000209:etiology / Q000517:prevention & control* / Q000523:psychology*; D003118:Color Perception / Q000502:physiology; D056805:Consciousness Monitors; D003693:Delirium / Q000209:etiology / Q000517:prevention & control* / Q000523:psychology*; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D011183:Postoperative Complications / Q000517:prevention & control* / Q000523:psychology*; D011446:Prospective Studies; D012307:Risk Factors; D016896:Treatment Outcome; D014705:Verbal Behavior; D014706:Verbal Learning