Decrease in arterial pressure following heparin injection prior to cardiopulmonary bypass

Evidence exists in the literature that heparin has vasodilating properties. We recorded arterial blood pressure changes that occur after administration of 300 units/kg of beef-lung heparin prior to cardiopulmonary bypass. In 37 out of 43 patients there was a significant decrease in arterial pressure following administration of beef-lung sodium heparin. Systolic blood pressure fell approximately 10 mmHg (1.3 kPa) and diastolic blood pressure fell about 5 mmHg (0.65 kPa). Heart rates remained unchanged. In 7 of the 43 patients in whom pulmonary artery catheters were placed, cardiac output was determined and systemic vascular resistance was calculated. On the basis of these calculations, it seems that a decrease in systemic vascular resistance is responsible for the decrease in arterial blood pressure noted following sodium heparin.