Ventricular arrhythmogenic dose of adrenaline during sevoflurane, isoflurane, and halothane anaesthesia either with or without ketamine or thiopentone in cats

The doses of adrenaline required to induce ventricular arrhythmia during sevoflurane, isoflurane and halothane anaesthesia, either with or without infusions of ketamine (76 mu g kg(-1) min(-1)) or thiopentone (0.5 mg kg(-1) min(-1)), were determined in cats. Groups of six to eight cats were maintained at end-tidal concentrations equivalent to 1.25 times the minimal alveolar concentration of each anaesthetic. The mean dose of adrenaline required to induce arrhythmia during sevoflurane anaesthesia (19.0 mu g kg(-1)) was approximately 11 times higher than that required during halothane anaesthesia (1.66 mu g kg(-1)) and the same as that required during isoflurane anaesthesia (19.0 mu g kg(-1)). Ketamine tended to decrease the requirement of adrenaline during halothane anaesthesia, but not significantly, and did not change the requirement during isoflurane or sevoflurane anaesthesia. Thiopentone did not change the requirement for adrenaline during halothane, isoflurane or sevoflurane anaesthesia. It was concluded that either with or without ketamine or thiopentone, the effect of sevoflurane on the sensitisation of the feline myocardium to the arrhythmogenic effects of adrenaline was significantly less than that of halothane and not different from that of isoflurane.