The Usefulness of Measuring Anti-Xa Activity for the Prediction of Bleeding Adverse Events During Postsurgical Fondaparinux Anticoagulant Therapy

Objective: Anticoagulation therapy is commonly used to prevent venous thromboembolism after abdominal surgery. However, bleeding during anticoagulation therapy is a problem, particularly in use of fondaparinux (FPX), for which there is no useful monitoring method. In this study, we examined the usefulness of measurement of the inhibitory activity of activated blood coagulation factor X (anti-Xa activity) for prediction of bleeding.Subjects and Methods: The subjects were 67 patients who underwent anticoagulation therapy with FPX after surgery for colorectal cancer. FPX (2.5 mg) was subcutaneously administered from Day 1 to Day 5. Measurement of anti-Xa activity were performed on Days 1, 3, 5 and 7 to evaluate the relationship between anti-Xa activity and bleeding.Results: No symptomatic venous thromboembolism developed in any patient. Bleeding was found in 11 subjects (16.4%). The anti-Xa activity gradually rose after initiation of administration in both the bleeding and non-bleeding groups until day 5. When the anti-Xa activity was compared between the bleeding and non-bleeding groups, the anti-Xa activity was higher in the bleeding group on day 3 (p=0.002).Conclusion: Careful attention to bleeding is required in anticoagulant therapy with FPX. Measurement of anti-Xa activity may be useful for prediction of bleeding.