Proarrhythmic effects of intravenous vasopressors.

OBJECTIVE: To review the electrophysiologic properties and the in vitro, ex vivo, animal, and human data regarding proarrhythmic effects of intravenous vasopressors. DATA SOURCES: A comprehensive (MEDLINE) search (1960-1994) was conducted for dopamine, epinephrine, norepinephrine, phenylephrine, and methoxamine. STUDY SELECTION: In vitro and ex vivo studies and investigations performed in animals or humans reporting electrophysiologic and/or proarrhythmic effects of the above intravenous vasopressors were selected. A comprehensive search of all human studies involving these agents was conducted to reveal any proarrhythmic effects that may have been reported. In addition, case reports of proarrhythmic effects associated with these agents were reviewed. DATA EXTRACTION: Data regarding electrophysiologic and proarrhythmic effects of these agents were extracted from in vitro, ex vivo, animal, and human studies. Because few studies with the specific purpose of investigating proarrhythmic effects of vasopressors have been performed in humans, all studies involving these drugs for evaluation of hemodynamic effects, clinical efficacy, or other endpoints in humans were reviewed. In addition, data were extracted from case reports of proarrhythmic effects associated with these agents. DATA SYNTHESIS: Dopamine increases automaticity in Purkinje fibers and has a biphasic effect on action-potential duration. Dopamine has caused both atrial and ventricular tachyarrhythmias in animals. Human data have revealed dose-related sinus tachycardia, with few reports of clinically significant ventricular arrhythmias. Epinephrine shortens sinus cycle length, increases atrial and ventricular automaticity, promotes atrioventricular nodal conduction, and decreases ventricular effective refractory period (ERP). It is well known to induce ventricular fibrillation and decrease the ventricular fibrillation threshold (VFT) in ex vivo models as well as intact animals. In humans, epinephrine may cause dose-related sinus tachycardia, supraventricular arrhythmias, or, more commonly, ventricular arrhythmias. Norepinephrine increases automaticity of the sinoatrial node, atria, and ventricles; promotes atrioventricular nodal conduction; and decreases ventricular ERP. In vitro/ex vivo and animal data have shown that norepinephrine significantly decreases VFT. Although electrophysiologic studies suggest that norepinephrine may be proarrhythmic, few supporting data exist in humans. Phenylephrine demonstrates differential electrophysiologic effects in atrial and ventricular tissue. Most data suggest that phenylephrine causes prolongation of the ventricular ERP. Rather than being proarrhythmic, phenylephrine may be protective against arrhythmias. The drug elevates VFT in dogs. In humans, phenylephrine effectively terminates supraventricular tachycardias and may be protective against ventricular arrhythmias. Like phenylephrine, methoxamine elevates the repetitive extrasystolic, atrial, and ventricular fibrillatory thresholds. Methoxamine also may have antiarrhythmic effects because of alpha-receptor stimulation and reflex vagal activity. Despite the relatively low risk of arrhythmogenicity associated with intravenous vasopressors, patients should be monitored for potential proarrhythmic effects and appropriate action taken as necessary. Critically ill patients often have concurrent conditions, electrolyte disturbances, and underlying arrhythmias that predispose them to a higher risk of vasopressor proarrhythmic effects.
CONCLUSIONS: Controlled data supporting the proarrhythmic potential of intravenous vasopressors in humans are lacking. Sinus tachycardia, asymptomatic ventricular ectopic activity, and other ventricular or supraventricular arrhythmias have been reported in association with dopamine and epinephrine. Phenylephrine and methoxamine have been associated with sinus bradycardia, but otherwise may be antiarrhythmic. Intravenous vasopressors appear relatively safe w