title: Depth of anaesthesia and post-operative cognitive dysfunction.
abstract: BACKGROUND
  A deep level of anaesthesia measured by the bispectral index has been found to improve processing speed as one aspect of cognitive function after surgery. The purpose of the present study was to assess the possible effect of the level of anaesthesia on post-operative cognitive dysfunction (POCD) 1 week after surgery, as assessed by a neuropsychological test battery.
  
  
  METHODS
  We included 70 patients >60 years of age scheduled for elective non-cardiac surgery with general anaesthesia. The depth of anaesthesia was monitored using the cerebral state monitor, which provided a cerebral state index (CSI) value. Cognitive function was assessed by the ISPOCD neuropsychological test battery before and at 1 week (or hospital discharge) after surgery and POCD was defined as a Z score above 1.96.
  
  
  RESULTS
  Five patients were not assessed after surgery. The mean CSI was 40 and 43 in patients with (N=9) and without POCD (N=56), respectively (P=0.41). The cumulated time of both deep anaesthesia (CSI<40) and light anaesthesia (CSI>60) did not differ significantly, and no significant correlation was found between the mean CSI and the Z score.
  
  
  CONCLUSIONS
  We were unable to detect a significant association between the depth of anaesthesia and the presence of POCD 1 week after the surgery.
authors.affiliation: Department of Anaesthesia, Centre of Head and Orthopaedics, University Hospital of Copenhagen, Copenhagen, Denmark. jacobsteinmetz@dadlnet.dk
authors.forename: J
authors.initials: J
authors.lastname: Steinmetz
authors.forename: K S
authors.initials: KS
authors.lastname: Funder
authors.forename: B T
authors.initials: BT
authors.lastname: Dahl
authors.forename: L S
authors.initials: LS
authors.lastname: Rasmussen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000768:Anesthesia, General; D018686:Anesthetics, Intravenous / Q000008:administration & dosage; D001288:Attention / Q000502:physiology; D016022:Case-Control Studies; D003071:Cognition / Q000502:physiology*; D003072:Cognition Disorders / Q000209:etiology; D017558:Elective Surgical Procedures; D004569:Electroencephalography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007858:Learning / Q000502:physiology; D008297:Male; D011939:Mental Recall / Q000502:physiology; D008609:Mental Status Schedule; D008875:Middle Aged; D009483:Neuropsychological Tests; D011183:Postoperative Complications; D015742:Propofol / Q000008:administration & dosage; D011446:Prospective Studies; D057190:Stroop Test; D013997:Time Factors; D014145:Trail Making Test; D014706:Verbal Learning / Q000502:physiology
chemical_list: D018686:Anesthetics, Intravenous; D015742:Propofol