Assessment of Quantity and Utility of water for ICU-Acquired hypernatraemia. A Pilot, Six-Centre, Open-Label, Safety and Physiological Efficacy Randomised Controlled Trial

Patients will be randomised to receive protocolised administration of hypotonic fluid or usual care for 7 days or ICU discharge. - Protocolised hypotonic fluid will be commenced at 100 mL/h, and repeat sodium as measured by blood gas machine will be performed at 6 hours. - Hypotonic fluid can be administered as enteral free water, intravenous 5% glucose, or a combination to achieve the desired rate. - The choice of hypotonic fluid will be at the discretion of the treating clinician. - All patients will also receive 6-hourly sodium measurements for the first 24 hours. - If sodium is less than 142 mmol/L, the hypotonic fluid will cease. - If sodium is greater than or equal to 142 mmol/L AND less than the previous sodium, the hypotonic fluid will continue at the current rate. - If sodium exceeds the previous sodium, the rate of hypotonic fluid will be increased by 100mL/h. - The intervention protocol will be conducted for 7 days, after which all patients receive usual care. There is no protocolised maximum hypotonic fluid rate. Adherence to the protocol will be assessed by review of the medical records. The intervention will be stopped if the patient is started on renal replacement therapy, if the patient is discharged from ICU, if the treating clinician has concerns about cerebral oedema, or, of course, in case of death.