Cerebral cortical effects of desflurane in sheep: comparison with isoflurane, sevoflurane and enflurane.
BACKGROUND
Different volatile anesthetic agents have differing propensities for inducing seizures. A measure of the predilection to develop seizures is the presence of interictal spike discharges (spikes) on the electrocorticogram (ECoG). In this study, we investigated the propensity of desflurane to induce cortical spikes and made a direct objective comparison with enflurane, isoflurane, and sevoflurane. The ECoG effects of desflurane have not been previously reported.


METHODS
After establishment of invasive monitoring and a parasagittal array of eight electrodes to record the ECoG; eight adult merino sheep were given a series of short inhalational anesthetics (using desflurane, enflurane, sevoflurane and isoflurane); each titrated to ECoG burst suppression. Anesthetic effect was estimated by the effects on the approximate entropy of the ECoG. The effect of anesthetic on the spike-rate in the ECoG was analyzed using a non-linear mixed-effect method with a sigmoid Emax model.


RESULTS
A similar 'depth of anesthesia' was achieved for each agent, as estimated by the approximate entropy. The mean (SD) values of Emax for the spike-rate vs. approximate entropy relationship were desflurane 0.5 (0.9), enflurane 17.2 (4.0), isoflurane 0.7 (1.2), and sevoflurane 5.3 (1.2) spikes/min. The spike rate caused by desflurane was similar to isoflurane and significantly lower than that of enflurane (P < 0.001), and sevoflurane (P = 0.009).


CONCLUSIONS
Desflurane induces minimal cerebral cortical spike activity when administered to burst suppression, consistent with its low propensity for inducing seizures in non-epileptic brains. The agents can be ranked by their relative ability to cause spike activity: enflurane >> sevoflurane > isoflurane = desflurane.
Waikato Clinical School, University of Auckland, Hamilton, New Zealand. vossl@waikatodhb.govt.nz
L J
LJ
Voss
G
G
Ludbrook
C
C
Grant
J W
JW
Sleigh
J P M
JP
Barnard
D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D002245:Carbon Dioxide / Q000494:pharmacology; D002540:Cerebral Cortex / Q000187:drug effects*; D000077335:Desflurane; D004569:Electroencephalography / Q000187:drug effects*; D004737:Enflurane / Q000494:pharmacology*; D007530:Isoflurane / Q000031:analogs & derivatives* / Q000494:pharmacology*; D008738:Methyl Ethers / Q000494:pharmacology*; D000077149:Sevoflurane; D012756:Sheep
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D002245:Carbon Dioxide; D000077149:Sevoflurane; D004737:Enflurane; D000077335:Desflurane; D007530:Isoflurane