COMPLETE HEPARIN-COATED (CBAS) CARDIOPULMONARY BYPASS AND REDUCED SYSTEMIC HEPARIN DOSE - EFFECTS ON COAGULATION AND FIBRINOLYSIS

Objective. Heparin-coated extracorporeal circuits allow reduced amount s of systemic heparin and protamine. However, the effects on the coagu lation and fibrinolytic systems when reducing systemic anticoagulation , have partly remained unknown. Methods. Thirty-three patients undergo ing elective first time myocardial revascularization were prospectivel y randomized either to have a cardiopulmonary bypass (CPB) circuit com pletely coated with covalently bound heparin, in combination with redu ced systemic heparinization (activated clotting time (ACT) > 250 s (n = 17), or to a control group perfused with identical but uncoated circ uits and full heparin dose (ACT > 480 s) (n = 16). Tests indicative of thrombin generation, platelet activation, and fibrinolytic activity w ere performed intraoperatively and postoperatively. Results. During CP B, the plasma level of prothrombin fragment 1.2 (PF 1.2) increased fro m median 1.5 (1.1-1.9) nmol/l to 5.4 (3.3-6.6) nmol/l in the heparin-c oated 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 anticoa gulation. The concentrations reached median 9.7 (6.8-19.5) nmol/l in t he heparin-coated group and 13.2 (4.2-18.4) nmol/l in the control grou p (no significant intergroup difference). A similar pattern was observ ed for the thrombin-antithrombin (TAT) complex. Regression analysis re vealed significant correlation between the levels of the thrombin mark ers and duration of CPB in both groups (P < 0.05). There was no correl ation between ACT or plasma heparin levels on bypass and the PF 1.2 an d TAT complex. The platelet re lease 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 diff erences with regard to fibrinolytic activity. Plasma fibrinogen as wel l as platelet counts were unchanged after the operation, compared to b aseline. Except for one patient in the control group sustaining periop erative myocardial infarction, the postoperative course was uneventful in all cases. Conclusions. Completely heparin-coated CPB can safely b e performed in combination with reduced systemic heparinization. The h eparin and protamine amounts could be lowered to 35% of normal doses. Indications of more thrombin generation on CPB compared to the uncoate d controls were seen, but the levels remained within low ranges in bot h groups. There was no evidence of thromboembolic episodes or clot for mation in the extracorporeal circuits.