Spectral entropy and bispectral index as measures of the electroencephalographic effects of sevoflurane.
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.
Ellerkmann
Richard Klaus
RK
Department of Anesthesiology and Intensive Care Medicine, University of Bonn, Bonn, Germany. richard.ellerkmann@ukb.uni-bonn.de
Liermann
Vidal-Markus
VM
Alves
Thorsten Michael
TM
Wenningmann
Ingobert
I
Kreuer
Sascha
S
Wilhelm
Wolfram
W
Roepcke
Heiko
H
Hoeft
Andreas
A
Bruhn
Jörgen
J
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
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane