HEPARIN COATING OF EXTRACORPOREAL CIRCUITS INHIBITS CONTACT ACTIVATION DURING CARDIAC OPERATIONS

Objective: Heparin coating reduces complement activation on the surfac e of extracorporeal circuits, In this study we investigated its effect on activation of the contact system in 30 patients undergoing coronar y artery bypass grafting with the use of a heparin-coated (Duraflo II, Baxter Healthcare Corp., Edwards Division, Santa Ana, Calif.; n = 15) or an uncoated extracorporeal circuit (n = 15), Methods: Plasma marke rs that reflect activation of contact (kallikrein-C1-inhibitor complex es), coagulation (prothrombin fragments F1+2), or fibrinolytic (plasmi n-alpha(2)-antiplasmin complexes) systems were determined before and d uring the operation, The generation of kallikrein-C1-inhibitor complex es was reduced by 62% (p = 0.06) after the onset of cardiopulmonary by pass and by 43% (p = 0.026) after the cessation of bypass in the group in which a heparin-coated circuit was used compared with the group in which the circuit was uncoated, Generation was reduced by 58% (p = 0. 06) when the ratio of kallikrein-C1-inhibitor to prekallikrein after o nset of bypass was considered, We detected significant increases in F1 +2 levels in both groups and increases in plasmin-alpha(2)-antiplasmin complexes in the heparin-coated group at cessation of bypass, but no intergroup differences were observed, Thus use of heparin-coated extra corporeal circuits during cardiac operations reduces formation of kall ikrein-C1-inhibitor complexes when compared with use of uncoated circu its, The heparin coating is not accompanied by similar reductions in c oagulation or fibrinolysis, suggesting that thrombin and plasmin forma tion during cardiopulmonary bypass occurs mainly independently of the contact system activation.