Which agent is most appropriate for deep vein thrombosis prophylaxis after surgery in moderate/high risk patients?

• A. Aspirin
• B. Warfarin
• C. Low molecular weight heparin
• D. Unfractionated heparin

Answer: (C)

After surgery in patients with moderate to high risk, the goal is to provide reliable, convenient, and safe venous thromboembolism prevention. Low molecular weight heparin fits this best because it enhances antithrombin to mainly inhibit factor Xa (with some IIa activity), has a predictable dose-response, is given subcutaneously with typically no routine monitoring, and reduces DVT risk more effectively than unfractionated heparin while carrying a lower risk of heparin-induced thrombocytopenia. Warfarin isn’t suitable for immediate postoperative prophylaxis due to its delayed onset and need for bridging with heparin and INR checks. Unfractionated heparin requires closer monitoring and has a higher HIT risk, making it less convenient and safer than LMWH in this setting. Aspirin generally provides less protection for DVT in high-risk postoperative patients.