Fluid resuscitation remains the cornerstone for the care of severe trauma patients to compensate for blood loss, to compensate for capillary leak induced by systemic inflammation but also to prevent the detrimental consequences of traumatic rhabdomyolysis. Isotonic saline (NaCl 0.9%), called "physiological serum" is the standard fluid for the resuscitation of severely injured patients. However, the formulation of NaCl 0.9% is not really physiological since its chloride concentration is 1.5 higher than plasma. This excessive chloride concentration leads to hyperchloremic acidosis and to a drop in renal perfusion after isotonic saline infusion. A retrospective study conducted in the perioperative setting (abdominal surgery) reported a significant decrease in mortality and acute kidney injury in 926 patients receiving balanced crystalloid solution compared to a propensity-matched population of 2778 patients receiving isotonic saline. Yunos et al. conducted a prospective sequential period study including 760 patients receiving chloride-rich solution during the first 6-month period and 773 patients receiving chloride-poor solution during the next 6-month period. They reported a decrease in severe acute kidney injury (I or F in the RIFLE classification) in the group receiving chloride-poor solution. Large retrospective studies in intensive care confirmed a beneficial effect of the use of chloride-poor solutions on survival compared to chloride-rich solutions. A recent meta-analysis including 5 small size randomized controlled trials, 1 controlled trial and two retrospective studies, reported also a decrease in acute kidney injury. A recent multicenter study randomized 2778 patients to receive either Plasmalyte 148 or NaCl 0.9% during their ICU stay. No AKI or mortality differences were reported. However, this study included patients with low ICU severity score (mean APACHE II = 14) and at low risk of severe AKI (severe AKI incidence = 9%). Moreover, they received a median amount of fluid of 2000 mL during their ICU stay. This small fluid volume may not be enough to show any difference between rich-chloride and poor-chloride solutions on AKI in this population with low ICU severity scores.

Trauma patients are particularly at risk of AKI during the acute phase of trauma because of hypovolemia (bleeding), rhabdomyolysis and systemic inflammation (traumatic tissue injuries and emergency surgeries). AKI is reported in 18 to 26 % of trauma patients. In our database (TraumaBase®, traumabase.eu) that included at the time of the study the 6 trauma centers of the Paris area (France), we reported a 24% incidence of severe AKI (stage I or F of the RIFLE classification) in the subpopulation of patients needing at least one red blood cell unit transfusion in the 6 first hours of care. Moreover, this subpopulation receives an average amount of 6000 mL of fluid during the first 24 hours of care. We postulate that trauma patients at high risk of AKI receiving high volume of fluid can be the best population target to demonstrate a beneficial effect of Plasmalyte vs isotonic saline on severe AKI occurrence in a prospective, blinded, randomized manner.

Thus, we formulate the following hypothesis:

In a population of trauma patients, at high risk of AKI, a fluid resuscitation with Plasmalyte Viaflo during the 5 first days of care will lower decrease the incidence of severe acute kidney injury (stage 2 or 3 according to the KDIGO classification) compared with a resuscitation with isotonic saline (NaCl 0.9%)