Bleeding Risk During Prolonged Dual Anticoagulation With Warfarin and Low‐Molecular‐Weight Heparin: A Retrospective Single‐Centre Study

BACKGROUNDS: Warfarin remains the anticoagulant of choice for selected high-risk patients [1]. Its narrow therapeutic index and pharmacokinetics make perioperative management challenging. Bridging with low-molecular-weight heparin (LMWH) during warfarin re-initiation reduces thromboembolic risk but may increase bleeding risk. METHODS: We conducted a retrospective cohort study on patients managed through the Hospital-in-the-Home (HITH) service at a tertiary centre in Melbourne, Australia. All patients admitted between 1 January and 31 December 2024 undergoing warfarin re-initiation with therapeutic-dose LMWH bridging were included. The primary outcome was bleeding incidence and severity during dual anticoagulation, defined by International Society of Thrombosis and Haemostasis (ISTH) criteria. Secondary analyses evaluated clinical and surgical factors associated with bleeding. RESULTS: Of 2348 HITH admissions, 129 patients were included. Bleeding occurred in 21 patients (16%), including 3 major and 18 minor events; there were no thromboembolic events or deaths. Most bleeding was managed in the community with only two requiring procedural intervention. Postoperative patients had higher bleeding incidence than non-operative re-initiators (23.9% vs. 8.1%; RR 2.96, 95% CI 1.15-7.60; OR 3.58, 95% CI 1.22-10.46; Fisher's exact p = 0.0175). Bleeding occurred at a median of 6 days of dual therapy. Previous long-term warfarin use, renal impairment, higher target INR and elevated anti-Xa exposure were associated with bleeding; target INR and anti-Xa remained independently associated with bleeding on multivariable analysis. CONCLUSIONS: Bleeding risk was more strongly associated with patient- and treatment-related risk factors than bridging duration alone. These findings support risk-stratified warfarin re-initiation and early monitoring during dual therapy.