A randomized controlled trial of isotonic versus hypotonic maintenance intravenous fluids in hospitalized children

Background: Isotonic saline has been proposed as a safer alternative to traditional hypotonic solutions for intravenous (IV) maintenance fluids to prevent hyponatremia. However, the optimal tonicity of maintenance intravenous fluids in hospitalized children has not been determined. The objective of this study was to estimate and compare the rates of change in serum sodium ([Na]) for patients administered either hypotonic or isotonic IV fluids for maintenance needs. Methods: This was a masked controlled trial. Randomization was stratified by admission type: medical patients and post-operative surgical patients, aged 3 months to 18 years, who required IV fluids for at least 8 hours. Patients were randomized to receive either 0.45% or 0.9% saline in 5.0% dextrose. Treating physicians used the study fluid for maintenance; infusion rate and the use of additional fluids were left to their discretion. Results: Sixteen children were randomized to 0.9% saline and 21 to 0.45% saline. Baseline characteristics, duration (average of 12 hours) and rate of study fluid infusion, and the volume of additional isotonic fluids given were similar for the two groups. [Na] increased significantly in the 0.9% group (+0.20 mmol/L/h [IQR +0.03, +0.4]; P = 0.02) and increased, but not significantly, in the 0.45% group (+0.08 mmol/L/h [IQR -0.15, +0.16]; P = 0.07). The rate of change and absolute change in serum [Na] did not differ significantly between groups. Conclusions: When administered at the appropriate maintenance rate and accompanied by adequate volume expansion with isotonic fluids, 0.45% saline did not result in a drop in serum sodium during the first 12 hours of fluid therapy in children without severe baseline hyponatremia. Confirmation in a larger study is strongly recommended.