Patients requiring interruption of long-term oral anticoagulant therapy: the use of fixed sub-therapeutic doses of low-molecular-weight heparin.

INTRODUCTION: We tested the efficacy and safety of fixed doses of low-molecular-weight heparin (LMWH) in patients requiring interruption of vitamin-K antagonist (VKA) because of invasive procedures.
METHODOLOGY: Preoperatively, patients discontinued VKA for 5 +/- 1 days; in those at low risk for thrombosis, LMWH was given at a prophylactic dosage of 3800 UI (nadroparin) or 4000 UI (enoxaparin) anti-factor (F) Xa once daily the night before the procedure. In patients at high risk for thrombosis, LMWH was started early after VKA cessation and given at fixed sub-therapeutic doses (3800 or 4000 UI anti-FXa twice daily) until surgery. Postoperatively, LMWH was reinitiated 12 h after procedure while VKA was reinitiated the day after. Heparin was continued until a therapeutic INR value was reached. The primary efficacy endpoints were the incidence of thromboembolism and major bleeding from VKA suspension (because of surgery) up to 30 +/- 2 days postprocedure.
RESULTS: A total of 328 patients (55.4% at low risk and 44.6% at high risk for thrombosis) were enrolled; 103 (31.4%) underwent major surgery and 225 (68.6%) non-major invasive procedures. Overall, thromboembolic events occurred in six patients (1.8%, 95% confidence interval 0.4-3.2), five belonging to the high-risk group and one belonging to the low-risk group. Overall, major bleeding occurred in seven patients (2.1%, 95 confidence interval 0.6-3.6), six patients belonged to the high-risk group and one belonged to the low-risk group; most of the events occurred in the high-risk group during major surgery.
CONCLUSION: LMWH given at fixed sub-therapeutic doses appears to be a feasible and safe approach for bridging therapy in chronic anticoagulated patients.