Objective: To compare the pharmacokinetic profiles of intravenous versus subcutaneous route of administration of LMWH for thromboprophylaxis in critically ill patients

The study is a prospective, monocentric, randomized trial. Patients are randomized to the IV route of administration over a 4-hours infusion of nadroparin 3800 IU or to the SC route of administration. Randomization is stratified according to the need for vasopressor or not. Anti-Xa activity is measured at baseline, and at 1, 2, 4, 6, 8, 12 and 24 hours after the administration was started.

Inclusion Criteria:

• Adults patients > 18 years old admitted in the ICU, and for whom thromboprophylaxis is indicated

Exclusion Criteria:

• renal failure determined by glomerular filtration rate (GFR) < 30 ml/min or need for renal replacement therapy
• liver cirrhosis
• intravascular disseminated coagulation
• contra-indication to thromboprophylaxis for any reason as decided by the treating physician, or indication for therapeutic dosing anticoagulation (recent thrombo-embolic event, atrial fibrillation,…)
• patients receiving low dose of vasopressor (norepinephrine < 0.25 mcg/kg/min) to allow stratification and comparison between patients not on vasopressors and patients with a significant dose of vasopressors (norepinephrine ≥ 0.25 mcg/kg/min)