Coagulation activation and reactive fibrinolysis in patients receiving oral anticoagulation after total hip or knee replacement.

Twenty patients having routine laboratory control of oral anticoagulation after total hip or knee arthroplasty were consecutively included in the study and were anticoagulated at an International Normalized Ratio (INR) between 2.5 and 3.5. Patients with mechanical heart valve prostheses (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 deep venous thrombosis groups the median prothrombin fragment 1 + 2 concentrations were significantly lower than in the orthopaedic patient group (0.15 and 0.17 nmol/l versus 0.29 nmol/l). The D-dimer concentrations displayed a similar picture (150 and 200 micrograms/l versus 840 micrograms/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 fibrinolysis/coagulation balance is enhanced, mainly due to a disproportional rise in D-dimer. After assessing when the D-dimer concentration returns 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.