Thromboprophylaxis is recommended for critically ill patients without contraindications and is usually achieved by the subcutaneous daily administration of a low dose of low molecular weight heparin (LMWH). The efficacy of this measure can be assessed by measuring the anticoagulation level obtained in the blood by dosing the anti-Xa activity. However, multiple studies have shown that anti-Xa activities in critically ill patients in the intensive care unit (ICU) are much lower, and below the desired range, than their ward counterparts.

LMWH elimination depends on kidney function and reduced dosing is recommended for patients with renal failure, treated or not with renal replacement therapy (continuous veno-venous hemofiltration (CVVH)). However, some scarce data suggest that even critically ill patients with renal failure treated with reduced or even with standard doses of LMWH, also have lower anti-Xa activities (below the desired range). If confirmed, this finding may suggest that reduced or even standard dosing of LMWH for thromboprophylaxis in critically ill patients with renal failure should be replaced by another dosing regimen or another route of administration. Therefore, this study aims to better characterize the pharmacokinetic profiles of LMWH after administration of a prophylactic dose of enoxaparin daily in patients with renal failure treated or not with CVVH, and to compare them to patients with no renal failure.

Inclusion Criteria:

• Age > 18 year old

• Hospitalized in the ICU.

• Equiped with an arterial line.

• Indication for thromboprophylaxis with a daily prophylactic dose of enoxaparin.

• Additionnally:

  • For cohort 1: severe renal failure (KDIGO stage ≥2) without CVVH AND SOFA score ≥4.
  • For cohort 2: severe renal failure (KDIGO stage ≥2) with CVVH AND sequential organ failure assessment (SOFA) score ≥4.
  • For cohort 3: no renal failure (creatinine clearance > 60 ml/min)

Exclusion Criteria:

• Platelet count < 50 000/μl.
• CHILD PUGH stage C cirrhosis.
• Known coagulation disorder.
• Patient treated in the last 3 days with direct oral anticoagulants.
• Patient treated in the last 24h with LMWH before enrollment.
• High bleeding risk with contra indication for standard dose of LMWH prophylaxis, as per investigator judgment
• Indication for therapeutic anticoagulation (including CVVH with systemic heparin anticoagulation).
• Body weight < 50 kg or > 120 kg.
• Evidence of recovery of renal function before enrollment, based on investigator judgement.

There is no intention to share IPD for this trial.