Responses to fasting and lipid infusion of epinephrine-induced arrhythmias during halothane anesthesia

Sensitivities to epinephrine in fasted and non-fasted rats anesthetized with halothane or pentobarbital were determined. The arrhythmic threshold for epinephrine, i.e., the dose which upon injection produced four or more premature ventricular contractions, was significantly lower for 12-hour (5.5 +/- 3.2 microgram/kg), 24-hour (2.2 +/- 1.3 microgram/kg) and 48-hour (2.25 +/- 0.6 microgram/kg) fasted rats than for non-fasted rats (10.9 +/- 3.4 microgram/kg) at the same dose of halothane (2.0 per cent). Fasting had no effect on the arrhythmic threshold for epinephrine in rats anesthetized with pentobarbital (35 mg/kg). Infusion of a 10 per cent fatty acid emulsion caused a significant lowering of the arrhythmic threshold for epinephrine of fed rats, while infusion of acetoacetic acid had no effect on the arrhythmic threshold. It is concluded that the combination of fasting and halothane anesthesia renders the heart more sensitive to epinephrine than halothane anesthesia alone.