The objective of this randomized controlled trial was to evaluate the risk of hyponatremia following administration of a isotonic (0.9% saline) compared to a hypotonic (0.45% saline) parenteral maintenance solution (PMS) for 48 hours to postoperative pediatric patients.
Surgical patients 6 months to 16 years of age with an expected postoperative stay of >24 hours were eligible. Patients with an uncorrected baseline plasma sodium level abnormality, hemodynamic instability, chronic diuretic use, previous enrollment, and those for whom either hypotonic PMS or isotonic PMS was considered contraindicated or necessary, were excluded. A fully blinded randomized controlled trial was performed. The primary outcome was acute hyponatremia. Secondary outcomes included severe hyponatremia, hypernatremia, adverse events attributable to acute plasma sodium level changes, and antidiuretic hormone levels.
A total of 258 patients were enrolled and assigned randomly to receive hypotonic PMS (N = 130) or isotonic PMS (N = 128). Baseline characteristics were similar for the 2 groups. Hypotonic PMS significantly increased the risk of hyponatremia, compared with isotonic PMS (40.8% vs 22.7%; relative risk: 1.82 [95% confidence interval: 1.21–2.74]; P = .004). Admission to the pediatric critical care unit was not an independent risk factor for the development of hyponatremia. Isotonic PMS did not increase the risk of hypernatremia (relative risk: 1.30 [95% confidence interval: 0.30–5.59]; P = .722). Antidiuretic hormone levels and adverse events were not significantly different between the groups.
Isotonic PMS is significantly safer than hypotonic PMS in protecting against acute postoperative hyponatremia in children.
Comments
Maintenance electrolytes and maintenance fluids
Having been a long-time advocate and teacher of the Holliday and Segar method (1957) of calculating maintenance fluids and electrolytes in infants and children, I have been reading the controversy in the last decade about the use of hypotonic intravenous fluids in hospitalized children. The recent article by Choong et al continues that controversy based on a randomized controlled trial they employed to detect the incidence of hyponatremia in the group receiving maintenance therapy. Holliday and Segar intended their model, based on calories expended, to be one for maintenance only and not to be used for replacement needs. What is unclear from the current article is whether or not children in this study actually received maintenance amounts of fluids as advocated by these authors. In fact, Choong et al state that 'the rate and total duration of PMS administration....were determined by the treating physician.' Not knowing the rate of this fluid administration in each child in the study group does not convince this reader that the use of hypotonic intravenous solutions for maintenance therapy is harmful if used appropriately. This would be the key as anything more than maintenance amounts of this hypotonic solution could certainly lead to hyponatremia.
Conflict of Interest:
None