Deleterious effects of bretylium on hemodynamic recovery from ventricular fibrillation

To study the effects of bretylium on the restoration of circulatory function after resuscitation from ventricular fibrillation, closed-chest anesthetized dogs were electrically fibrillated for 1 minute followed by defibrillation (direct-current shock). After one control episode of fibrillation and defibrillation, 16 dogs received a bolus of bretylium (10 mg/kg intravenously). A second episode of fibrillation and defibrillation was induced in eight dogs 3 minutes after bretylium and in eight dogs 4 hours after bretylium. Prior to bretylium, mean arterial blood pressure spontaneously recovered to exceed 200 mm Hg by 2 minutes after defibrillation in all 16 dogs. However, after bretylium, 13 of 16 dogs were in electromechanical dissociation 2 minutes after defibrillation (p less than 0.001). Despite external chest compression, epinephrine, and sodium bicarbonate, a stable blood pressure could not be restored in 6 of 16 dogs. Clofilium, a bretylium analogue lacking sympathetic influences, did not alter the pattern of hemodynamic recovery following defibrillation in five of five dogs. The results suggest that the effects of bretylium on the sympathetic nervous system may profoundly influence the outcome of cardiac resuscitation from fibrillation.