Certain cardiovascular effects of vasopressin (Pitressin)

Pitressin was administered intravenously in doses of 0.1 to 1 unit per kilogram of body weight either at once or during a period of thirty minutes to dogs which were anesthetized with pentobarbital sodium. Cardiac output was determined by application of the Fick principle. Systolic and diastolic blood pressures at various points in the heart or pulmonary vessels were recorded by means of strain gauges connected to cardiac catheters. Another strain gauge recorded the blood pressure from a needle inserted into the femoral artery. The blood flow was recorded in heparinized animals from one or both femoral arteries by use of bubble flowmeters. Administration of Pitressin produced definite reduction in cardiac rate, consumption of oxygen, venous content of oxygen and cardiac output. Sometimes the heart became arrhythmic, and extrasystoles appeared soon after injection of Pitressin. Initially, transient increases were noted in both systolic and diastolic blood pressures in the femoral artery. This was soon followed by increases in the systolic and diastolic pressures in the pulmonary artery, in the wedge pressure in the small pulmonary vessels, and in pressures in the left atrium, while pressures in the femoral artery decreased to less than control values and the pulse pressure was much reduced. Administration of Pitressin produced great reduction in femoral blood flow.