 The aim of the study is therefore to compare perdialytic hemodynamic tolerance and fluid overload after 7 days of SLEDD-f using 2 sodium dialysate concentrations -140 vs 145 mmoll- in ICU AKI patients. The investigators also planned to evaluate and compare mean ultrafiltration rate by patient, total duration of RRT, fluid overload at RRT weaning, ICU length of stay and 28 days ICU mortality using these 2 levels of sodium dialysate concentration. 