The anticonvulsant effects of volatile anesthetics on lidocaine-induced seizures in cats.

UNLABELLED: Large concentrations of sevoflurane and isoflurane, but not halothane, induce spikes in the electroencephalogram. To elucidate whether these proconvulsant effects affect lidocaine-induced seizures, we compared the effects of sevoflurane, isoflurane, and halothane in cats. Fifty animals were allocated to 1 of 10 groups: 70% nitrous oxide (N2O), 0.6 minimum alveolar anesthetic concentration (MAC) + 70% N2O, 1.5 MAC + 70% N2O, and 1.5 MAC of each volatile agent in oxygen. Lidocaine 4 mg x kg(-1) x min(-1) was infused IV under mechanical ventilation with muscle relaxation. Electroencephalogram in the cortex, amygdala, and hippocampus and multiunit activities in the midbrain reticular formation (R-MUA) were recorded. Lidocaine induced spikes first from the amygdala or hippocampus in the 70% N2O and halothane groups and from the cortex in the sevoflurane and isoflurane groups. Lidocaine induced seizures in all cats in the 70% N2O and 0.6 MAC + N2O groups. Seizure occurrence was reduced in the 1.5 MAC + N2O group (P < 0.05 versus 70% N2O). The onset of seizure was delayed in the 0.6 MAC + N2O and 1.5 MAC groups for sevoflurane and isoflurane, but not for halothane, compared with the 70% N2O group (P < 0.05). Lidocaine increased R-MUA with seizure by 130%+/-56% in the 70% N2O group. The increase of R-MUA with seizure was more suppressed in the volatile anesthetic groups than in the 70% N2O group (P < 0.05). In the present study, sevoflurane and isoflurane attenuated seizure when the blood lidocaine concentration was accidentally increased. IMPLICATIONS: Increasingly, epidural blockade is combined with general anesthesia to achieve stress-free anesthesia and continuous pain relief in the postoperative period. In the present study, sevoflurane and isoflurane attenuated seizure when the blood lidocaine concentration was accidentally increased.