Intermittent hemodialysis/diafiltration is a current renal replacement therapy (RRT) institued for ICU patients with AKI. For a better clinical tolerance, iinternational guidelines advise to use cold dialysate, increase duration session, decrease blood and dialysate flows, and increase level of sodium dialysate concentration (≥ 145mmol/l). Indeed, the use of a Na concentration dialysate > 145 mmol/l improves intradialytic hemodynamic tolerance but it may also induce fluid overload by the transfert of sodium from the dialysate compartment to the blood. Yet, fluid overload has been strongly associated with mortality in critically ills. The investigators hypothesized that the use of a level in sodium dialysate at 140 mmol/l with slow low efficiency daily dialysis-filtration (SLEDD-f) will permit a fair intradialytic hemodynamic tolerance without the adverse effect of intradiaclytic Na loading from the dialysate. Two randomized groups of ICU AKI patients treated by SLEDD-f will be compared in terms of intradialytic hemodynamic tolerance and overload accordong to 140 or 145 mmol/l of Na in the dialysate

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 hemodialysis/diafiltration (IHD/F) 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 (≥ 145mmol/l). 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.

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 mmol/l- 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.

Methods: This randomised, single center, prospective and non blinded study is being held in medical ICU at Lapeyronie University Hospital of Montpellier.

Patient more than 18 years old, admitted to the ICU for AKI requiring RRT and with a sSofa score > 5 will be included.

RRT will be an on line predilution SLEDD- with the following parameters: blood flow 200ml/min, dialysate flow 200ml/min, infusate flow 60ml/min, temperature 36°C, membrane polysulfone Fx80. An hemodynamic monitoring will be performed at each dialysis session. Weight, daily input and output and extracellular volume will be monitored during ICU stay.

According to the sodium concentration dialysate: 140 or 145 mmol/l, 2 groups will be randomized and compared regarding to hemodynamic tolerance, fluid overload and outcome.

Hypothesis: The use of a sodium dialysate concentration at 140 mmol/l with SLEDD-f will induce a similar intradialytic hemodynamic tolerance as compared to a Na dialysate at 145 mmmol/l but with a decrease at around 4% of fluid overload.

Inclusion criteria:

• Age > 18 years old
• Acute kidney injury requiring renal replacement therapy
• Dialysis type: on line sustained low efficiency dialy dialysis -filtration
• SOFA score > 5
• Sodium serum level between 135 and 145mmol/l

Exclusion criteria:

• Chronic kidney disease stade IV ou V
• Obstrutive acute kidney injury
• Renal tansplantation in the year before ICU admission
• Moribund with risk of death in the 48 hours
• Vulnerable persons or protected persons
• Pregnant or breastfeeding mother

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