Hyponatremia and Hypotonic Intravenous Fluids Are Associated With Unfavorable Outcomes of Bronchiolitis Admissions.

Objectives: Hyponatremia has been associated with unfavorable outcomes when present at admission in children with bronchiolitis. Delayed hyponatremia may be a modifiable risk factor for severe disease that is influenced by intravenous fluid (IVF) tonicity. We hypothesized that both hyponatremia and prescription of severely hypotonic IVF are associated with unfavorable outcomes, and that prescription of severely hypotonic IVF is associated with subsequent hyponatremia.

Methods: Data were retrospectively extracted for 1557 pediatric inpatients with bronchiolitis. Any day on which a subject was prescribed IVF with sodium <70 mEq/L was termed "IVF <70." All other days on which IVF was prescribed were termed "IVF ≥70." Any blood sodium ≤135 mEq/L defined hyponatremia for that day. All other days with sodium available were labeled normonatremia. Variables were compared with Spearman correlation, Wilcoxon rank test, or χ. Significant results had < .05.

Results: Blood sodium levels correlated negatively with hospital length of stay ( = -0.477, < .0001). On each of the first 4 days of hospitalization, significantly increased hospital length of stay was observed in patients with hyponatremia ( = 134 [25.7% of subjects with available sodium data]) versus patients with normonatremia ( = 387 [74.3%]), and in patients prescribed IVF <70 ( = 348 [46.3% of subjects prescribed IVF]) versus patients prescribed IVF ≥70 ( = 403 [53.7%]). Patients prescribed IVF <70 had increased rates of hyponatremia on the subsequent day versus patients prescribed IVF ≥70 (50.0% vs 26.9%, < .001).

Conclusions: In children hospitalized with bronchiolitis, hyponatremia may be a modifiable risk factor for severe disease that may be mitigated by avoiding use of severely hypotonic IVF.