Treatment of bupivacaine-induced cardiac arrhythmias in hypoxic and hypercarbic pigs with amiodarone or bretylium.

The treatment of bupivacaine-induced cardiovascular toxicity with amiodarone or bretylium was studied using anesthetized pigs (n = 30). The pigs were given ketamine, glycopyrrolate, enflurane, and pancuronium and made hypoxic (FiO2, 12%; N2O, 88%) and hypercarbic (end-tidal CO2, 7.3-8.0%) before the administration of bupivacaine (4 mg/kg i.v.). The animals were then treated, in a randomized and double-blind fashion, with either amiodarone (n = 10) 10 mg/kg in 5% dextrose solution i.v. followed by a constant infusion of 15 mg/hour, bretylium (n = 10) 20 mg/kg in 5% dextrose solution i.v. followed by a constant infusion of 90 mg/hour, or 5% dextrose solution (n = 10). The animals were resuscitated, if required. After 30 minutes of recovery, the animals that survived were made hypoxic and hypercarbic again and given a second injection of bupivacaine (2 mg/kg IV). Bupivacaine caused marked changes in the ECG; polymorphic ventricular tachycardia (20 cases) or severe bradycardia that resulted in asystole (10 cases). Nine animals out of ten treated with amiodarone survived (stable sinus rhythm, arterial blood pressure at near control level, normocarbia), whereas six animals in the bretylium group and four in the control group died. The difference in survival between the groups was not, however, statistically significant.