COAGULATION ACTIVATION AND REACTIVE FIBRINOLYSIS IN PATIENTS RECEIVING ORAL ANTICOAGULATION AFTER TOTAL HIP OR KNEE REPLACEMENT

Twenty patients having routine laboratory control of oral anticoagulat ion after total hip or knee arthroplasty were consecutively included i n the study and were anticoagulated at an International Normalized Rat io (INR) between 2.5 and 3.5. Patients with mechanical heart valve pro stheses (n = 20), deep venous thrombosis or pulmonary embolism (n = 20 ), at the same level of oral anticoagulation, served as control groups . Plasma concentrations of prothrombin fragment 1 + 2 and D-dimer were measured and compared. In the mechanical heart valve prosthesis and d eep venous thrombosis groups the median prothrombin fragment 1 + 2 con centrations were significantly lower than in the orthopaedic patient g roup (0.15 and 0.17 nmol/l versus 0.29 nmol/l). The D-dimer concentrat ions displayed a similar picture (150 and 200 mu g/l versus 840 mu g/l ). The D-dimer/prothrombin fragment 1 + 2 ratios in the patients after total hip or knee arthroplasty were significantly higher (12.4) than in the control groups (5.3 and 6.0). These data show that the fibrinol ysis/coagulation balance is enhanced, mainly due to a disproportional rise in D-dimer. After assessing when the D-dimer concentration return s to normal in this anticoagulated group, this parameter may indicate the appropriate duration of oral anticoagulant treatment after surgery for total knee or hip replacement.