Effects of levodopa on systemic and coronary hemodynamics of intact conscious dogs

Abstract

Effects of Levodopa on Systemic and Coronary Hemodynamics of Intact Conscious Dogs COLIN M. BLOOR, MD; ARTHUR S. LEON, Jr., MS, MD; FRANCIS C. WHITE, BS, La Jolla, California and Nutley, New Jersey The effects of levodopa, lo-30 mg/kg intravenously, 0.1-0.25 mg/kg per min intravenously and 0.1-1.0 mg/kg per min intracoronary, on systemic and coronary hemodynamics were studied in 4 intact, conscious dogs. Phasic circumflex coronary blood ilow (CBF) and cardiac output (CO) were recorded from implanted electromagnetic flow transducers along with mean aortic pressure (AP). Higher intravenous doses of levodopa increased heart rate (HR) from 82 to 113 beats/ min (62%), AP from 110 to 116 mm Hg (5%), CBF from 35 to 102 ml/min (192%) and CO from 3.10 to 4.70 liters/min (54%) while mean coronary resistance and total peripheral vascular resistance decreased 62% and 32%, respectively. Lower intravenous doses of levodopa gave similar responses but of smaller magnitude. Continuous intravenous infusions of levodopa produced changes in systemic and coronary hemodynamics that were similar to those seen with bolus injections. When levodopa was infused via an implanted intracoronary tube at a dose of 0.1 mg/kg per min CBF increased from 45 to 51 ml/min (14%). This was accompanied by a decrease in mean coronary resistance while systemic hemodynamics were unchanged. These results indicate that acute intravenous administration of levodopa produces positive inotropic and chronotropic effects on the heart as weli as systemic and coronary vasodilation. The latter action, as indicated by the changes following intracoronary administration, is at least in part due to a direct action on the coronary arteries. The effects resemble those previously seen with intravenously administered dopamine, except that the latter drug increased peripheral vascular resistance. Vegetative Endocarditis: A Reevaluation NEIL A. BUCHBINDER, MD; WILLIAM C. ROBERTS, MD, FACC,