title: Comparison of spectral entropy and BIS VISTA™ monitor during general anesthesia for cardiac surgery.
abstract: OBJECTIVE
  We compared the primary metrics of the Spectral entropy M-ENTROPY™ module and BIS VISTA™ monitor-i.e., bispectral index (BIS), state entropy (SE), and response entropy (RE) in terms of agreement and correlation during general anesthesia for cardiac surgery. We also evaluated responsiveness of electroencephalogram (EEG)-based and hemodynamic parameters to surgical noxious stimulation, skin incision, and sternotomy, hypothesizing that RE would be a better responsiveness predictor.
  
  
  METHODS
  BIS and entropy sensors were applied before anesthesia induction in 32 patients having elective cardiac surgery. Total intravenous anesthesia was standardized and guided by the BIS index with neuromuscular blockade tested with train-of-four monitoring. Parameters included SE, RE, BIS, forehead electromyography (EMG), and hemodynamic variables. Time points for analyzing BIS, entropy, and hemodynamic values were 1 min before and after: anesthesia induction, intubation, skin incision, sternotomy, cannulation of the aorta, cardiopulmonary bypass (CPB), cross-clamping the aorta, de-clamping the aorta, and end of CPB; also after starting the re-warming phase and at 10, 20, 30, and 40 min following.
  
  
  RESULTS
  The mean difference between BIS and SE (Bland-Altman) was 2.14 (+16/- 11; 95% CI 1.59-2.67), and between BIS and RE it was 0.02 (+14/- 14; 95% CI 0.01-0.06). BIS and SE (r(2) = 0.66; P = 0.001) and BIS and RE (r(2) = 0.7; P = 0.001) were closely correlated (Pearson's). EEG parameters, EMG values, and systolic blood pressure significantly increased after skin incision, and sternotomy. The effect of surgical stimulation (Cohen's d) was highest for RE after skin incision (-0.71; P = 0.0001) and sternotomy (-0.94; P = 0.0001).
  
  
  CONCLUSIONS
  Agreement was poor between the BIS index measured by BIS VISTA™ and SE values at critical anesthesia time points in patients undergoing cardiac surgery. RE was a good predictor of arousal after surgical stimulation regardless of the surgical level of muscle relaxation. Index differences most likely resulted from different algorithms for calculating consciousness level.
authors.affiliation: Department of Anesthesiology, Kuopio University Hospital, P.O. Box 1777, 70211 Kuopio, Finland. tadeusz.musialowicz@kuh.fi
authors.forename: Tadeusz
authors.initials: T
authors.lastname: Musialowicz
authors.forename: Pasi
authors.initials: P
authors.lastname: Lahtinen
authors.forename: Otto
authors.initials: O
authors.lastname: Pitkänen
authors.forename: Jouni
authors.initials: J
authors.lastname: Kurola
authors.forename: Ilkka
authors.initials: I
authors.lastname: Parviainen
mesh_terms: D000368:Aged; D000465:Algorithms; D000768:Anesthesia, General / Q000379:methods*; D001011:Aorta / Q000473:pathology; D001794:Blood Pressure; D006348:Cardiac Surgical Procedures / Q000295:instrumentation* / Q000379:methods*; D002315:Cardiopulmonary Bypass / Q000379:methods; D004576:Electromyography / Q000379:methods; D019277:Entropy; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*