Continuous Veno-venous Hemodialysis and Continuous Veno-venous Hemodiafiltration on Urea Reduction Rate in Intensive Care Patient

Patients will receive a CVVHD dialysis with a dose of 25ml/kg/h dialysate (100% dialysate), with Fresenius Medical Care multiFiltrate PRO kit and Ultraflux AV1000S filter (polysuflone 1.8m²).Regional anticoagulation with citrate

Patients will receive a CVVHDF dialysis with a dose of 25ml/kg/h dialysate (50% ultrafiltration, 50% dialysate), with Fresenius Medical Care multiFiltrate PRO kit and Ultraflux AV1000S filter (polysuflone 1.8m²). Systemic anticoagulation with heparine