title: Spectral entropy and bispectral index as measures of the electroencephalographic effects of sevoflurane.
abstract: BACKGROUND
  Recently, entropy algorithms have been proposed as electroencephalographic measures of anesthetic drug effects. Datex-Ohmeda (Helsinki, Finland) introduced the Entropy Module, a new electroencephalographic monitor designed for measuring depth of anesthesia. The monitor calculates a state entropy (SE) computed over the frequency range of 0.8-32 Hz and a response entropy (RE) computed over the frequency range of 0.8-47 Hz. The authors investigated the dose-response relation of SE and RE during sevoflurane anesthesia in comparison with the Bispectral Index (BIS).
  
  
  METHODS
  Sixteen patients were studied without surgical stimulus. Anesthesia was induced by sevoflurane inhalation with a tight-fitting facemask. Sevoflurane concentrations were increased and subsequently decreased and increased two to four times until the measurement was stopped and patients were intubated for surgery. The performances of SE, RE, and BIS to predict the estimated sevoflurane effect site concentration, obtained by simultaneous pharmacokinetic and pharmacodynamic modeling, were compared by calculating the correlation coefficients and the prediction probability.
  
  
  RESULTS
  State entropy, RE, and BIS values decreased continuously over the observed concentration range of sevoflurane. Correlation coefficients were slightly but not significantly better for entropy parameters (0.87 +/- 0.09 and 0.86 +/- 0.10 for SE and RE, respectively) than for BIS (0.85 +/- 0.12). Calculating the prediction probability confirmed these results with a prediction probability of 0.84 +/- 0.05 and 0.82 +/- 0.06 for SE and RE, respectively, and 0.80 +/- 0.06 for BIS.
  
  
  CONCLUSIONS
  State entropy and RE seem to be useful electroencephalographic measures of sevoflurane drug effect.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University of Bonn, Bonn, Germany. richard.ellerkmann@ukb.uni-bonn.de
authors.forename: Richard Klaus
authors.initials: RK
authors.lastname: Ellerkmann
authors.forename: Vidal-Markus
authors.initials: VM
authors.lastname: Liermann
authors.forename: Thorsten Michael
authors.initials: TM
authors.lastname: Alves
authors.forename: Ingobert
authors.initials: I
authors.lastname: Wenningmann
authors.forename: Sascha
authors.initials: S
authors.lastname: Kreuer
authors.forename: Wolfram
authors.initials: W
authors.lastname: Wilhelm
authors.forename: Heiko
authors.initials: H
authors.lastname: Roepcke
authors.forename: Andreas
authors.initials: A
authors.lastname: Hoeft
authors.forename: Jörgen
authors.initials: J
authors.lastname: Bruhn
mesh_terms: D000328:Adult; D000465:Algorithms; D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation / Q000493:pharmacokinetics; D003627:Data Interpretation, Statistical; D004569:Electroencephalography / Q000187:drug effects*; D019277:Entropy; D005260:Female; D006801:Humans; D008297:Male; D008738:Methyl Ethers / Q000493:pharmacokinetics; D008954:Models, Biological; D016343:Monitoring, Intraoperative; D011237:Predictive Value of Tests; D000077149:Sevoflurane
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane