Do anticoagulation with heparin and protamine reversal alter thrombogenicity of coated and noncoated pulmonary artery catheters?

OBJECTIVE: To clarify the role of anticoagulation with heparin and protamine reversal on the effectiveness of heparin bonding or coating of pulmonary artery catheters in preventing thrombus formation in the Rhesus monkey. DESIGN: A controlled, unblinded, open-labeled study. SETTING: A research laboratory at Tulane School of Medicine (New Orleans, LA). PARTICIPANTS: Twenty-four anesthetized Rhesus monkeys. INTERVENTIONS: The monkeys were assigned to one of four groups. In the first group (group A), non-heparin-coated catheters were inserted into a femoral vein through an incision, advanced proximally for a distance of 30 cm, and left in place for 1 hour. In the second group (group B), heparin-coated catheters were placed and evaluated in the same manner as in group A. In the third group (group C), the primates received 3 mg/kg of heparin intravenously (i.v.) before insertion of a non-heparin-coated pulmonary artery catheter. After the catheter had been in place for 1 hour, protamine, 3 mg/kg i.v., was administered, and the catheter was left in place for an additional hour. In the final group (group D), the primates received 3 mg/kg of heparin i.v. before insertion of a heparin-coated pulmonary artery catheter. After the catheter had been in place for 1 hour, protamine, 3 mg/kg i.v., was administered, and the catheter was left in place for an additional hour. In each group, the catheter was withdrawn with the balloon inflated to minimize any stripping of thrombus from the surface of the catheter. Thrombus was removed from the catheter through a femoral vein cutdown and weighed. Laboratory values were determined for each animal, and clot formation was evaluated in each group. After completion of the study, the animals were returned to the primate breeding colony. MEASUREMENTS AND MAIN RESULTS: There were no significant differences in hematocrit, prothrombin time, partial thromboplastin time, or platelet levels among the four groups; therefore, the data were pooled. Clots were observed on five of six catheters in both groups A and C; however, clot formation was seen in one of six catheters in group B and three of six catheters in group D. There was a statistically significant difference (p < 0.01) in mean clot weight in group A (265 +/- 68 mg; range, 0 to 447 mg) compared with 13 +/- 13 mg in group B (range, 0 to 80 mg). There was no significant difference in mean clot weight in group C (104 +/- 35 mg; range, 0 to 202 mg) compared with group D (24 +/- 16 mg, range, 0 to 98 mg). Additionally, in group C, the mean clot weight was significantly less than in group A. CONCLUSION: Anticoagulation of primates with heparin before catheter insertion imparts some protection to non-coated catheters, and protamine reversal of anticoagulation with heparin may partially negate the protective effect seen with heparin-coated pulmonary artery catheters.

Duke Scholars

Author Muhammad Farooq Anwar Anesthesiology, Pain Management