- invasive mechanical ventilation - thrombocytopenia (platelet count < 80.000 mm3) - coagulopathy: inr >1.5, aptt ratio > 1.4 - impaired renal function (egfr calculated by ckd-epi creatinine equation < 30 ml/min) - known hypersensitivity to enoxaparin - history of heparin induced thrombocytopenia - presence of an active bleeding or a pathology susceptible of bleeding in presence of anticoagulation (e.g. recent haemorrhagic stroke, peptic ulcer, malignant cancer at high risk of haemorrhage, recent neurosurgery or ophthalmic surgery, vascular aneurysms, arteriovenous malformations) - concomitant anticoagulant treatment for other indications (e.g. atrial fibrillation, venous thromboembolism, prosthetic heart valves). - concomitant double antiplatelet therapy - administration of therapeutic doses of lmwh, fondaparinux, or unfractionated heparin (ufh) for more than 72 hours before randomization; prophylactic doses are allowed - pregnancy or breastfeeding or positive pregnancy test - presence of other severe diseases impairing life expectancy (e.g. patients are not expected to survive 28 days given their pre-existing medical condition) - lack or withdrawal of informed consent

- invasive mechanical ventilation - thrombocytopenia (platelet count < 80.000 mm3) - coagulopathy: inr >1.5, aptt ratio > 1.4 - impaired renal function (egfr calculated by ckd-epi creatinine equation < 30 ml/min) - known hypersensitivity to enoxaparin - history of heparin induced thrombocytopenia - presence of an active bleeding or a pathology susceptible of bleeding in presence of anticoagulation (e.g. recent haemorrhagic stroke, peptic ulcer, malignant cancer at high risk of haemorrhage, recent neurosurgery or ophthalmic surgery, vascular aneurysms, arteriovenous malformations) - concomitant anticoagulant treatment for other indications (e.g. atrial fibrillation, venous thromboembolism, prosthetic heart valves). - concomitant double antiplatelet therapy - administration of therapeutic doses of lmwh, fondaparinux, or unfractionated heparin (ufh) for more than 72 hours before randomization; prophylactic doses are allowed - pregnancy or breastfeeding or positive pregnancy test - presence of other severe diseases impairing life expectancy (e.g. patients are not expected to survive 28 days given their pre-existing medical condition) - lack or withdrawal of informed consent