Hemodynamic changes after the administration of protamine

Hemodynamic changes associated with the administration of protamine were studied in 30 dogs divided into three equal groups. Protamine (1 mg X kg-1 X min-1 for 4 min) was administered 10 min after 4 mg X hg-1 heparin was given via a left atrial (LA) line in group A, via a central vein in group B, and via a peripheral vein in group C. Protamine given through the central venous pressure (CVP) line resulted in an immediate and significant decrease in mean arterial pressure (MAP) to 60 +/- 4.5 mm Hg (P less than 0.025) from 72 +/- 7 mm Hg immediately after the protamine and to 58 +/- 5 mm Hg (P less than 0.025) 5 min later and with an increase in cardiac index (CI) to 3.7 +/- 0.3 L X min-1 X m-2 from 2.8 +/- .25 L X min-1 X m-2 immediately after the protamine (P less than 0.005), followed by a decrease back to 2.7 +/- 0.3 L X min-1 X m-2 5 min later. Mean arterial pressure and CI remained unchanged after administration of protamine via the peripheral vein or the left atrium. Systemic vascular resistance (SVR) decreased significantly only after administration of protamine via the CVP and was statistically unchanged when administered via the peripheral and LA line. Plasma histamine levels increased significantly after administration of protamine through the central line but remained unchanged after administration via a peripheral vein or the left atrium.