REVERSE-AKI Randomized Controlled Pilot Trial

Inclusion Criteria: 1. 18-years or older and admitted to critical care with an arterial line in place 2. The patient has been in critical care for at least 12 hours but no more than 72 hours 3. The patient has AKI but is not receiving acute RRT: For the purpose of the study AKI is defined the by the following criteria: 1. Increase in serum creatinine over 1.5-times above baseline without a decline of 27umol/l or more from the last preceding measurement (at least 12 hours apart) AND/OR 2. Overall urine output less than 0.5ml/kg/h (or 6ml/kg) for the previous 12h (with urine catheter in place for the period) 4. The patient is judged by the treating clinician not to be intravascularly hypovolemic 5. The patient is likely to remain in critical care for 48 hours after randomization Exclusion Criteria: 1. Active bleeding necessitating transfusion 2. Maintenance fluid therapy is necessary due to diabetic ketoacidosis, non-ketotic coma, severe burns or other clinical reason determined by the medical staff 3. Need for RRT due to intoxication of a dialyzable toxin 4. Commencement of RRT is expected in the next 6 hours 5. On chronic renal replacement therapy (maintenance dialysis or renal transplant) 6. Presence or a strong clinical suspicion of parenchymal AKI (for example glomerulonephritis, vasculitis, acute interstitial nephritis), or post-renal obstruction 7. Severe hyponatremia (Na \<125mmol/L) or hypernatremia (Na \>155mmol/L) 8. Need for extracorporeal membrane oxygenation or molecular absorbent recirculating system (MARS-therapy) 9. Pregnant or lactating 10. Patients who are not to receive full active treatment 11. No baseline creatinine available 12. Lack of consent 13. The patient has been enrolled in another trial where co-enrollment is not feasible