The effect of differing rates and injection sites on the amount of protamine delivered before detection of hemodynamic alterations in dogs

Objectives-To determine the effect of the route and rate of protamine admin istration on the amount of protamine that could be delivered before a hemod ynanmic reaction occurred in dogs. Study design-Prospective randomized experimental study. Animals-Twenty adult mixed-breed dogs weighing 25.1 +/- 2.5 kg. Methods-Before vascular surgery, the dogs were heparinized to reach an acti vated clotting time (ACT) of 300 seconds. After completion of the vascular surgery, protamine was administered intravenously until a hemodynamic react ion was recorded. The 4 groups of dogs were given protamine at 5 mg/min (sl ow) or 10 mg/min (fast) via the cephalic or the jugular veins. Systemic and pulmonary arterial pressures, central venous pressure (CVP), and pulmonary arterial occlusion pressure (PAOP) were recorded before and after protamin e administration. The dose of protamine was recorded when a reaction occurr ed, which was defined as mean arterial pressure (MAP) <60 mm Hg or mean pul monary arterial pressure (MPAP) >20 mm Hg or more than double the baseline value. Results-Significant decreases in systolic arterial pressure (SAP), MAP, and diastolic arterial pressure (DAP) and significant increases in systolic (S PAP), mean (MPAP), and diastolic (DPAP) pulmonary arterial pressures were r ecorded after protamine administration. The cephalic slow group had signifi cantly fewer protamine reactions than other groups (chi-square = 8.57, P = .03, df = 3). Significantly more protamine could be delivered from the ceph alic vein (52.5 +/- 14.5 mg) compared with the jugular vein (37.6 +/- 16 mg ) before a reaction occurred (P = .048). Conclusion-The rate of administration did not have an effect on the amount of protamine delivered. Adverse reactions were minimized when protamine was administered via the cephalic vein at a slow rate. Clinical Relevance-We would recommend delivering protamine after cardiopulm onary bypass or vascular surgery through a peripheral venous route. (C) Cop yright 2000 by The American College of Veterinary Surgeons.