Comparison of Resuscitation of Sheep and Dogs after Bupivacaine-Induced Cardiovascular Collapse

Abstract

This study evaluated interspecies sensitivity and ability to resuscitate pentobarbital anesthetized sheep and dogs after cardiovascular toxic doses of bupivacaine. Every minute, 3 mg/kg of bupivacaine was injected into the right atrium over the course of 10 sec until cardiovascular collapse occurred. While the bupivacaine was given, the animals were made apneic for 90 sec and then ventilated with 100% oxygen. After the bupivacaine administration, cardiovascular collapse occurred in the form of electromechanical dissociation progressing to asystole in dogs, whereas in sheep the predominant rhythm was ventricular fibrillation leading to asystole. Resuscitation was performed using open chest heart massage, bretylium for treatment of ventricular tachycardia and fibrillation, and epinephrine with atropine for treatment of electromechanical dissociation or asystole. The initial dose of bupivacaine used to cause cardiovascular collapse was 3.5 +/- 1.2 mg/kg in sheep and 24.6 +/- 8.5 mg/kg in dogs (P less than 0.01). All sheep and dogs were resuscitated from the first cardiovascular collapse. The resuscitation time was 2.1 +/- 1.0 min in dogs and 36.9 +/- 15.4 min in sheep (P less than 0.01). All dogs could be resuscitated after two additional cardiovascular collapses induced by bupivacaine, but no sheep could be resuscitated after a second cardiovascular collapse. Concentrations of bupivacaine in cardiac tissue and serum levels of bupivacaine after the last resuscitation attempt were significantly greater in the dogs than in the sheep. We conclude that sheep are more sensitive to bupivacaine than dogs, but that even sheep can be resuscitated after cardiovascular collapse produced by bupivacaine.