DOSE-DEPENDENT DIFFERENCES IN CATECHOLAMINE ACTION ON HEART AND PERIPHERY

¹ Anesthesia Laboratory of the Harvard Medical School at the Massachusetts General Hospital, Boston, Massachusetts

Dose-response curves were made in 10 intact anesthetized dogs, following sympathetic and parasympathetic block, of epinephrine and norepinephrine effect upon left ventricular contractile force, cardiac rate, mean arterial blood pressure and mean aortic blood flow. From these measurements resistance, conductance, and indices of internal and external cardiac work were calculated.

The circulatory response to epinephrine and norepinephrine was found to change with increasing doses, reaching maximum effect upon the heart with significantly smaller doses than those needed to produce maximal peripheral effect. Small doses facilitated myocardial contractility and blood flow, which decreased with increasing doses. Large doses of epinephrine and norepinephrine favored the peripheral pressor effect and placed the heart at an increasing disadvantage. The clinical implications of these findings are discussed.