Complete heparin-coated (CBAS) cardiopulmonary bypass and reduced systemic heparin dose; effects on coagulation and fibrinolysis.

ABSTRACT

OBJECTIVE: Heparin-coated extracorporeal circuits allow reduced amounts of systemic heparin and protamine. However, the effects on the coagulation and fibrinolytic systems when reducing systemic anticoagulation, have partly remained unknown. METHODS: Thirty-three patients undergoing elective first time myocardial revascularization were prospectively randomized either to have a cardiopulmonary bypass (CPB) circuit completely coated with covalently bound heparin, in combination with reduced systemic heparinization (activated clotting time (ACT) > 250 s (n = 17), or to a control group perfused with identical but uncoated circuits and full heparin dose (ACT > 480 s) (n = 16). Tests indicative of thrombin generation, platelet activation, and fibrinolytic activity were performed intraoperatively and postoperatively. RESULTS: During CPB, the plasma level of prothrombin fragment 1.2 (PF 1.2) increased from median 1.5 (1.1-1.9) nmol/l to 5.4 (3.3-6.6) nmol/l in the heparin-coated group, and was significantly higher (P = 0.01) than the increase from 1.4 (1.2-1.9) nmol/l to 3.2 (2.2-4.3) nmol/l seen in the control group. However, the increase on CPB was modest compared to the major elevation observed after completed surgery and reversal of the anticoagulation. The concentrations reached median 9.7 (6.8-19.5) nmol/l in the heparin-coated group and 13.2 (4.2-18.4) nmol/l in the control group (no significant intergroup difference). A similar pattern was observed for the thrombin-antithrombin (TAT) complex. Regression analysis revealed significant correlation between the levels of the thrombin markers and duration of CPB in both groups (P < 0.05). There was no correlation between ACT or plasma heparin levels on bypass and the PF 1.2 and TAT complex. The platelet release of beta-thromboglobulin increased in both groups during CPB and significantly more in the control group at the end of bypass (P < 0.01), indicating less platelet activation in the heparin-coated group. There were no significant intergroup differences with regard to fibrinolytic activity. Plasma fibrinogen as well as platelet counts were unchanged after the operation, compared to baseline. Except for one patient in the control group sustaining perioperative myocardial infarction, the postoperative course was uneventful in all cases. CONCLUSIONS: Completely heparin-coated CPB can safely be performed in combination with reduced systemic heparinization. The heparin and protamine amounts could be lowered to 35% of normal doses. Indications of more thrombin generation on CPB compared to the uncoated controls were seen, but the levels remained within low ranges in both groups. There was no evidence of thromboembolic episodes or clot formation in the extracorporeal circuits.