Is the NICE Guideline for maintenance fluid therapy in adults in hospital appropriate?

Background And Aims: The National Institute for Health and Care Excellence's (NICE) Guideline for Maintenance Fluid Therapy in Adults in Hospital is widely used, but the recommendations have not been evaluated properly. In this study, we investigated whether the recommendation of providing 25-30 mL/kg/day of fluid and 1 mmol/kg each of sodium and potassium is sufficient for human needs.

Methods: First, we calculated the distribution of fluid between the extracellular fluid volume (ECV) and intracellular fluid volume (ICV) during a cross-over infusion experiment where 12 volunteers received 25 mL/kg/day of either a high-sodium (154 mmol/L) or low-sodium (54 mmol/L) solution over 48 h. Second, urine samples from 719 volunteers and clinical patients were used to quantify their renal water conservation and excretion of sodium and potassium. Third, retrospective analysis of a diet study was used to extrapolate how large the fluid intake and the electrolyte excretion likely had been in the 719 volunteers and hospital patients who delivered urine.

Results: The high-sodium fluid maintained the ECV but the ICV had decreased by 1.3 L after 48 h. The low-sodium fluid resulted in a volume deficit of 1.7 L that equally affected the ECV and the ICV. Regression equations based on the diet study suggested that the daily intake of water in the 719 subjects averaged 2.6 L and that 2 mmol/kg of sodium and 1 mmol/kg of potassium was excreted.

Conclusion: The NICE guideline recommends too little water and sodium for a human to adequately maintain the ECV and ICV.

Clinical Trial Registrations: EudraCT 2016-001846-24 and ISRCTN 12215472.