BACKGROUND: To evaluate the effects of thoracic epidural anesthesia, with or without bilateral vagotomy, epinephrine-induced arrhythmias were studied in 31 rabbits anesthetized with 1 MAC enflurane. METHODS: Logdose protocol was used for the infusion of epinephrine; its arrhythmic dose being defined as the smallest infusion rate produced four or more continuous or intermittent arrhythmias within 15 seconds. RESULTS: The values (geometric mean) of arrhythmic doses and the plasma concentration of epinephrine during arrhythmia were as follows: 10.21 g.kg 1.min 1 and 83.16 ng/ml in epidural control group; 118.90 g.kg 1.min 1 and 677.76 ng/ml in epidural lidocaine group (p<0.05); 6.34 g.kg-1.min 1 and 96.42 ng/ml in intravenous lidocaine group; 8.65 g.kg 1.min-1 and 44.64 ng/ml in vagotomized-epidural control group; and 12.03 g.kg 1.min 1 and 95.35 ng/ml in vagotomized- epidural lidocaine group. CONCLUSIONS: The data suggest that thoracic epidural anesthesia raises the threshold for enflurane- epinephrine arrhythmias in rabbits and that this effect is eliminated by bilateral vagotomy.