Influence of Vasopressin on Colon Blood Flow in Monkeys

Abstract

Inferior mesenteric arterial blood flow was measured with an electromagnetic blood flowmeter in five anesthetized rhesus monkeys. The effects of vasopressin on this vasculature were determined to evaluate the optimal, safe concentration of this agent during its clinical application in the management of hemorrhagic lesions of the colon. Control flow was 29 +/- 3 (SE) ml min-1; aortic pressure was 124 +/- 4 mm Hg. Intraarterial injections of vasopressin, in doses ranging logarithmically from 5 X 10(-5) to 5 X 10(-2) U kg-1, caused dose-dependent decreases in flow. At the highest dose, vasopressin reduced flow by 50% and increased arterial pressure by 9 mm Hg. When infused, at a rate of 5 X 10(-3) U kg-1 min-1, vasopressin produced a significant and sustained reduction in inferior mesenteric arterial blood flow. Autoregulatory escape was not observed. At this rate, vasopressin increased arterial pressure 10 mm Hg, by the 6th minute of infusion. This hypertension was unaccompanied by significant bradycardia. After cessation of the infusion, flow gradually returned to control values over a period of minutes. These observations indicate that vasopressin is a potent constrictor in the inferior mesenteric arterial circulation of the monkey, and support the use of this agent to control lower intestinal bleeding in man. At a dose of 5 X 10(-3) U kg-1 min-1, vasopressin causes a significant reduction in flow without adverse systemic side effects.