title: Comparison of SNAP™ II and BIS Vista indices during normothermic cardiopulmonary bypass under isoflurane anesthesia.
abstract: OBJECTIVE
  Processed EEG monitoring during cardiopulmonary bypass (CPB) may help determine loss of consciousness and depth of anesthesia. This study compared the SNAP(™) II and BIS Vista monitors in patients undergoing isoflurane anesthesia with normothermic CPB.
  
  
  METHODS
  40 subjects undergoing CPB with isoflurane anesthesia were enrolled. Subjects were premedicated with 1-2 mg midazolam approximately 5 min prior to acquisition of baseline index values and anesthesia induced with midazolam and fentanyl. Anesthesia was maintained with isoflurane, midazolam, and fentanyl and a cis-atracurium infusion. SNAP(™) II (version 1.2.9 algorithm 1.88) and BIS Vista (application version 3.00 platform version 2.03) indices were recorded at baseline, pre-induction, post-intubation, incision, start of CPB, every 15 min during CPB, end of CPB, and end of case. Agreement between methods was determined using Pearson correlation and the Bland-Altman method with repeated observa- tions.
  
  
  RESULTS
  Twenty-four male and 12 female subjects completed the analysis. The correlation between SNAP(™) II and BIS Vista index values was 0.61 (P < 0.005). A linear relationship between the difference in the indices and the average index values was observed following the induction of anesthesia. In awake subjects, the bias between the SNAP(™) II and BIS Vista was 5 (95% CI 3-7). The limits of agreement were 23 (95% CI 19-26) and -13 (95% CI -9--16). During anesthesia, the mean difference on a log scale was 0.11 (95% CI 0.09-0.12). The limits of agreement were 0.43 (95% CI 0.40-0.45) and -0.21 (95% CI -0.18--0.24). The antilog of the mean difference demonstrated that the SNAP(™) II value was 28% (95% CI 24-33%) higher than the BIS Vista value following induction of anesthesia.
  
  
  CONCLUSIONS
  The SNAP(™) II monitor demonstrates a consistently positive bias during cardiopulmonary bypass under isoflurane anesthesia compared with the BIS Vista.
authors.affiliation: Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA.
authors.forename: Kinjal M
authors.initials: KM
authors.lastname: Patel
authors.forename: Saadia S
authors.initials: SS
authors.lastname: Sherwani
authors.forename: Paul C
authors.initials: PC
authors.lastname: Fitzgerald
authors.forename: Robert J
authors.initials: RJ
authors.lastname: McCarthy
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018685:Anesthetics, Inhalation / Q000008:administration & dosage; D002315:Cardiopulmonary Bypass / Q000295:instrumentation* / Q000379:methods; D003936:Diagnosis, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D004569:Electroencephalography / Q000187:drug effects* / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D007530:Isoflurane / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation* / Q000379:methods
chemical_list: D018685:Anesthetics, Inhalation; D007530:Isoflurane
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