Venous thromboembolism is a frequent issue in severe trauma patients. Guidelines for venous thromboembolism prevention include the use of pharmacological thromboprophylaxis, mainly with low-molecular-weight heparin, and/or mechanical thromboprophylaxis. However, a high incidence of venous thromboembolism is observed despite standard dose thromboprophylaxis (such as enoxaparin 40 mg once daily).

An increase of the dose of anticoagulants could improve thromboprophylaxis in trauma patients. To date, two randomised trials have assessed the effect of weight-based low-molecular-weight heparin dosing vs. fixed dose in trauma patients. These pilot studies did not demonstrate a statistical difference between groups although there was a trend in favour of a lower incidence of deep vein thromboses with the increased dose low-molecular-weight heparin prophylaxis. However, both studies included non-severe trauma patients and the second study focused only on deep vein thromboses. Other studies suggested that a superior-than-standard dose of low-molecular-weight heparin, sometimes

guided by the anti-Xa activity, decreases the incidence of venous thromboembolism in severe trauma without increasing bleeding events, but they were observational in nature.

The hypothesis of the HEPTRAUMA trial is that, in severe trauma patients, a thromboprophylaxis with intermediate dose low-molecular-weight heparin (twice the standard dose) decreases the incidence of major venous thromboembolism compared to standard dose.

Inclusion Criteria:

• All adult patients (age ≥18 years) admitted to an intensive care unit following trauma with an expected stay >48 hours and a planned administration of LMWH.
• Affiliation to the French social security system or European (CEAM)

Exclusion Criteria:

• Prehospital cardiac arrest
• Hospital admission >72 hours
• More than one dose of prophylactic anticoagulant already administered since trauma
• Renal failure defined by creatinine clearance of 30 mL/min or less (Cockcroft-Gault formula)
• Body weight >100 kg or <45 kg
• Indication for therapeutic anticoagulation
• Major known thrombophilia (e.g. antiphospholipid syndrome, antithrombin deficiency)
• Constitutional bleeding disorder (haemophilia, von Willebrand disease, coagulation factor deficiency, platelet disorder).
• Thrombocytopenia inferior to 50 G.L-1
• History of heparin-induced thrombocytopenia
• Study drug hypersensitivity
• Limitation of life support, life expectancy ≤7 days or palliative care
• Contraindication to the administration of anticoagulant according to the SPC (Active clinically significant bleeding or a condition associated with a high risk of bleeding, such as a recent haemorrhagic stroke, gastrointestinal ulcer, the presence of a malignant tumour at high risk of bleeding, recent brain, spinal or ophthalmological surgery, known or suspected oesophageal varices, arteriovenous malformations, vascular aneurysms or major intrarachid or intracerebral vascular anomalies.)
• pregnant or breastfeeding woman
• Inclusion in another experimental trial
• Protected person (art. L1121-5 to L1121-8 of the CSP or art. 31 to 35 of European regulation 536/2014)