 Acute kidney injury AKI requiring renal replacement therapy RRT occurs in 5 to 6 of critically ill patients and is associated with high mortality and significant health resource utilization. Modalities of RRT currently available include intermittent hemodialysisdiafiltration IHDF and continuous renal replacement therapies. Continuous veno-venous therapies have gained wide application in ICUs, often supplanting IHD because of the belief that it is better tolerated in hemodynamically unstable patients. Previous reports have shown however that intermittent therapies may permit similar hemodynamic tolerance but with specific parameters including dialysate composition. Consequently, international guidelines suggest in ICU AKI the use of intermittent modalities with the use of cold dialysate, increased duration session, decreased blood and dialysate flows, and high level of sodium dialysate concentration 145mmoll. Increasing the level of sodium dialysate concentration improves obviously the hemodynamic tolerance but may also result in inflated extracellular volume and fluid overload secondary to sodium transfert from the dialysate compartment to the blood. There is a body of evidence that fluid overload may be harmful to the critically ill, has an adverse impact and worsens outcome. 