Concentration-effect relations, prediction probabilities (Pk), and signal-to-noise ratios of different electroencephalographic parameters during administration of desflurane, isoflurane, and sevoflurane in rats.
BACKGROUND
The authors investigated the suitability of different electroencephalographic parameters to quantify the anesthetic effect of desflurane, isoflurane, and sevoflurane in rats.


METHODS
Ten male Sprague-Dawley rats were anesthetized in a randomized crossover design with maximum values of 11% desflurane, 2.1% isoflurane, and 3.5% sevoflurane. The electroencephalogram was recorded with implanted electrodes and a wireless telemetry system. Concentration-effect relations and signal-to-noise ratios were determined for the approximate entropy and for the median frequency and the spectral edge frequency, which were modified to account for spikes and burst suppression. The prediction probability Pk with respect to the response to a painful stimulus was determined.


RESULTS
All drugs produced deep anesthesia with burst suppression and no response at the highest concentrations. The occurrence of spikes and burst suppression made a modification of median frequency and spectral edge frequency necessary to obtain Pk values greater than 0.5 and monotonic sigmoid concentration-effect relations. The Pk values were between 0.89 and 0.98, with significantly higher values for modified median frequency and spectral edge frequency during desflurane and sevoflurane. The signal-to-noise ratios were between 3.0 and 6.4 dB, with significantly better values for modified spectral edge frequency and approximate entropy during sevoflurane.


CONCLUSIONS
If modified for spikes and burst suppression, median frequency and spectral edge frequency as well as the unmodified approximate entropy were able to assess the anesthetic effect of desflurane, isoflurane, and sevoflurane in rats. For sevoflurane, the modified spectral edge frequency was best with regard to signal-to-noise ratio and prediction probability.
Ihmsen
Harald
H
Department of Anesthesiology, Friedrich-Alexander UniversityErlangen-Nuremberg, Erlangen, Germany. harald.ihmsen@kfa.imed.uni-erlangen.de
Schywalsky
Michael
M
Plettke
Regina
R
Priller
Michael
M
Walz
Florian
F
Schwilden
Helmut
H
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology; D018592:Cross-Over Studies; D000077335:Desflurane; D004558:Electric Stimulation; D004569:Electroencephalography / Q000187:drug effects*; D007530:Isoflurane / Q000031:analogs & derivatives* / Q000494:pharmacology*; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology*; D023421:Models, Animal; D010146:Pain / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D000077149:Sevoflurane
D008738:Methyl Ethers; D000077149:Sevoflurane; D000077335:Desflurane; D007530:Isoflurane