THROMBIN PRODUCTION, INACTIVATION AND EXPRESSION DURING OPEN-HEART-SURGERY MEASURED BY ASSAYS FOR ACTIVATION FRAGMENTS INCLUDING A NEW ELISA FOR PROTHROMBIN FRAGMENT-F(1+2)

Activation of coagulation was studied during the peri-operative period in patients undergoing cardiopulmonary bypass (CPB) surgery using act ivation markers which have recently become available: prothrombin frag ment F1 + 2 (F1 + 2), which is a measure of total thrombin generation, and thrombin-antithrombin complex, which is a measure of inactivation of free thrombin by antithrombin. Levels of the specific marker of fi brin breakdown, D-dimer, were also determined. F1 + 2 levels were asse ssed using a newly developed ELISA described herein which employs a ne oantigen-specific capture antibody raised using a synthetic peptide; t he latter antibody has been pre-adsorbed against prothrombin to ensure high specificity for F1 + 2. Increased generation of thrombin during surgery was clearly demonstrated despite maintenance of a high concent ration of heparin during the period of extracorporeal blood circulatio n. There was a close association (r = 0.882) between the generation of thrombin (F1 + 2 levels) and its inhibition (TAT levels). Differences were noted, however, between the information provided by F1 + 2 and T AT, which are interpreted with regard to the different in vivo fates o f F1 + 2 and thrombin. The enhanced activation and inhibition of coagu lation observed during CPB was suppressed once physiological blood cir culation was restored, with F1 + 2 returning to pre-surgical levels wi thin 24 h after surgery. During the post-operative period D-dimer leve ls, which rose in concert with F1 + 2 and TAT levels, remained highly elevated, suggesting that not all of the generated thrombin was inacti vated by antithrombin. It is concluded that heparin is only partially effective as an anticoagulant during CPB surgery. F1 + 2 is an unambig uous marker of thrombin generation and its measurement may be a useful means of evaluating more effective coagulation inhibitors in CPB.