ACTIVATION OF FIBRINOLYSIS IN THE PERICARDIAL CAVITY DURING CARDIOPULMONARY BYPASS

The clotting and fibrinolytic systems are activated by tissue factor a nd by tissue-type plasminogen activator in the pericardial cavity, whe re the thrombogenicity is greater than that of the surface of modern e xtracorporeal circuits. This local activation may have consequences fo r the systemic activation processes during cardiopulmonary bypass. To test this hypothesis, we investigated blood activation by interrupting the blood suction from the pericardial cavity during cardiopulmonary bypass in clinical coronary artery bypass operations. In blood collect ed in the pericardial cavity, thrombin-antithrombin III complex (p < 0 .01), tissue-type plasminogen activator antigen (p < 0.05), fibrinogen degradation products (p < 0.01), and fibrin degradation products (p < 0.01) were significantly higher than in the systemic blood. Plasma he parin was significantly consumed in the pericardial cavity (p < 0.01). Once the pericardial blood was returned to the systemic circulation a fter resumed suction during cardiopulmonary bypass, thrombin-antithrom bin III complex (p < 0.05), fibrinogen degradation products (p < 0.05) , and fibrin degradation product (p < 0.05) concentrations increased s ignificantly in the systemic blood. The effects of pericardial tissue on activation of clotting and fibrinolysis were also studied in vitro. When human plasma was incubated for 5 minutes with rabbit pericardium at reduced heparin concentrations, we found significant generation of thrombin (p < 0.05) and plasmin (p < 0.05). If the thrombin inhibitor hirudin was added, plasmin generation was also inhibited (p < 0.05). The results of the clinical and experimental study are in agreement wi th our hypothesis that tissue factor and tissue-type plasminogen activ ator accelerate the activation of clotting and sequentially of fibrino lysis under conditions of low heparin concentrations in the pericardia l cavity and that this local activation contributes highly to the syst emic activation, affecting hemostasis during cardiopulmonary bypass. T opical use of heparin in the pericardial cavity therefore seems indica ted to reduce blood activation during cardiopulmonary bypass.