Isotonic versus Hypotonic Maintenance Intravenous Fluids in Hospitalized Children

In children without severe baseline hyponatremia, 0.45% saline did not result in a drop in serum sodium during the first 12 hours of fluid therapy when administered at the appropriate maintenance rate and accompanied by adequate volume expansion with isotonic fluids, a recent study has found.

Confirmation of the findings in a larger study is strongly recommended, according to the researchers, who were headed by Thomas G. Saba, MD, of Montreal Children’s Hospital in Canada. The study was published in BMC Pediatrics.

The researchers initiated the study because although isotonic saline has been proposed as a safer alternative to traditional hypotonic solutions for intravenous (IV) maintenance fluids to prevent hyponatremia, the optimal tonicity of maintenance intravenous fluids in hospitalized children has not been determined.

The goal of the 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.

“Although the best choice of solution for IV maintenance needs has not yet been defined, many clinicians, including those at our institution, commonly prescribe 0.45% saline as a sort of ‘compromise’ between the traditional 0.18% saline and a complete switch to isotonic fluids,” the authors wrote in the study abstract. “Therefore, we chose to compare 0.9% saline in 5.0% dextrose to 0.45% saline in 5.0% dextrose (subsequently referred to as 0.9% and 0.45% saline, respectively).”

For the masked, controlled trial, randomization was stratified by admission type, with either medical patients or post-operative surgical patients, aged 3 months to 18 years, who required IV fluids for at least eight 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, but infusion rate and the use of additional fluids were left to their discretion.

“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,” the authors wrote.

SourceA Randomized, Controlled Trial of Isotonic versus Hypotonic Maintenance Intravenous Fluids in Hospitalized Children [BMC Pediatrics]