Hemodynamic effects of vasopressin. Can large doses be safely given?

We evaluated the effects of intravenous (IV) vasopressin on central hemodynamics, as well as myocardial and gastrointestinal (GI) blood flow, to delineate an optimal dosage balanced to yield maximum reduction of GI blood flow with minimal adverse cardiac effects. Eight miniature swine were anesthetized, ventilated, catheterized, and infused with vasopressin for three consecutive 30-minute periods at logarithmically increasing doses (0.001, 0.01, and 0.1 units/kg/min). We determined cardiac output, systemic arterial pressure, and microsphere tissue blood flow after each infusion. We found that IV vasopressin (0.001 units/kg/min) produced substantial reductions in blood flow to the GI tract and heart, and reduced the cardiac index (3.0 +/- 0.4 to 2.1 +/- 0.3 L/sq m/min). Increased doses of vasopressin (X 10 and X 100) decreased gastric mucosal blood flow even more, with minimal adverse effects on cardiac output and myocardial blood flow.