Similarity of arterial and intravenous vasopressin on portal and systemic hemodynamics

The effects of superior mesenteric arterial and intravenous infusions of vasopressin and low and high dose intravenous infusions of vasopressin on splanchnic and systemic hemodynamics were compared in 20 anesthetized dogs. The following parameters were evaluated: flow in the superior mesenteric artery and portal vein, portal and systemic blood pressure, and cardiac output. In the comparison of selective arterial and intravenous infusions, no statistically significant difference was found between the degree of changes in portal flow, portal and systemic blood pressure, and cardiac output. Only the superior mesenteric artery flow showed a greater decrease with the selective arterial injection. In a comparison of intravenous high dose (corresponding to that used clinically) and low dose (one fifth) infusions of vasopressin, a relatively high splanchnic and low systemic effectiveness of the low dose was found. It resulted in only a 15 to 20% smaller effect on flow in the superior mesenteric artery and portal vein and portal pressure; however, about 40% lesser systemic effect on arterial blood pressure and cardiac output than the high dose. The results of this experimental work warrant exploration in clinical practice, preferably by a controlled study. If clinical success in controlling hemorrhage confirms these hemodynamic results, an intravenous low dose infusion of vasopressin would appear to be the method of choice in the vasoconstrictive therapy of gastrointestinal bleeding from varices.