Abstract

The effects of dopamine (1-100 µg/kg) were determined in cats anesthetized with pentobarbital, cyclopropane or halothane. The iv. injection of dopamine increased myocardial contractile force, systolic and diastolic pressure markedly and heart rate slightly. Cardiac arrhythmias were not produced in pentobarbital-anesthetized animals. However, during cyclopropane or halothane inhalation, dopamine produced cardiac arrhythmias or ventricular fibrillation. The arrhythmias could be prevented by the i.v. injection of 0.5 mg/kg of levo H56/28, a beta adrenergic blocking agent, but not by dextro H56/28, which has only [unknown] to [unknown] the beta adrenergic blocking action of the levo isomer. In halothane-anesthetized hypotensive cats, the infusion of 10 µg/kg/min of dopamine for 30 to 60 min increased systolic and diastolic pressure more than 60% without producing cardiac arrhythmias. After weighing the possible beneficial effects of dopamine against the possibility of producing cardiac arrhythmias, it seems reasonable to undertake a cautious study of the value of dopamine in hypotension and shock in patients anesthetized with cyclopropane or halogenated hydrocarbons.