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)