Venous Thromboembolism Prophylaxis

Venous thromboembolism prophylaxis lowers the risk of deep vein thrombosis and pulmonary embolism in patients whose risk of clot exceeds their risk of bleeding. Every admitted adult needs a documented risk assessment on admission and again after any change in condition, because hospital-acquired clots are largely preventable.

Risk assessment. Raised risk comes from reduced mobility, major surgery, trauma, active cancer, sepsis, heart or respiratory failure, previous thrombosis, age over 60 years, obesity, pregnancy and the puerperium, oestrogen-containing drugs and inherited thrombophilia. Scores such as Padua (4 or more is high risk) and Caprini support, but do not replace, judgement.

Bleeding risk. Active bleeding, platelets under 50 x 10^9/L, severe coagulopathy, recent intracranial haemorrhage, uncontrolled hypertension (over 230/120 mmHg), acute stroke with haemorrhage and a lumbar puncture within 12 hours are contraindications to drug prophylaxis. Use mechanical prophylaxis meanwhile.

• Enoxaparin 40 mg subcutaneously once daily. Use 20 mg daily if creatinine clearance is 15 to 30 mL/min or weight is under 50 kg. Body mass index 40 or over: 40 mg twice daily.
• Unfractionated heparin 5000 units subcutaneously every 8 to 12 hours. Preferred when creatinine clearance is under 30 mL/min or in dialysis.
• Dalteparin 5000 units subcutaneously once daily. Tinzaparin 4500 units subcutaneously once daily.
• Fondaparinux 2.5 mg subcutaneously once daily. Used in heparin-induced thrombocytopenia history. Avoid if creatinine clearance is under 20 mL/min and use with caution at 20 to 50 mL/min.
• Mechanical: intermittent pneumatic compression devices are the first choice when drugs are contraindicated. Graduated stockings alone are of limited benefit.

Timing with neuraxial procedures. Give prophylactic low molecular weight heparin at least 12 hours before spinal or epidural puncture and 4 hours after catheter removal. Unfractionated heparin 5000 units: 4 to 6 hours before puncture and 1 hour after removal.

Kidney impairment. Choose unfractionated heparin or reduced-dose low molecular weight heparin. Check anti-Xa activity if it is used for more than 5 days.

Liver disease. A raised INR does not protect against clots. Give prophylaxis unless there is active bleeding or platelets are under 50 x 10^9/L.

Pregnancy. Weight-banded enoxaparin: under 50 kg 20 mg daily, 50 to 90 kg 40 mg daily, 91 to 130 kg 60 mg daily, 131 to 170 kg 80 mg daily. Warfarin, direct oral anticoagulants and fondaparinux are avoided except under specialist direction.

Older adults. Frail older adults on prophylaxis need renal function checked at baseline and each week.

Special groups. In East Africa, immobile patients with HIV, tuberculosis, malignancy, sickle cell disease and postpartum women have high rates of thrombosis, and low molecular weight heparin may not be stocked, so unfractionated heparin is the usual choice.

Monitoring. Check a full blood count at baseline and every 2 to 3 days for 14 days for heparin-induced thrombocytopenia (a platelet fall over 50% or a clot 5 to 14 days after starting). Check creatinine at baseline and weekly.

Referral and escalation. Seek specialist input for platelets under 50 x 10^9/L, a past thrombosis on prophylaxis, mechanical valves, pregnancy and suspected heparin-induced thrombocytopenia.

Stopping. Stop when the patient is fully mobile or at discharge. For medical inpatients this is usually 6 to 14 days; after major cancer surgery continue for 28 days.