Prevalence of Hyponatremia in Patients With Moderate to Severe Bronchiolitis

Objective: To estimate the frequency and severity of hyponatremia in infants hospitalized with moderate–severe bronchiolitis and to assess its association with the severity of disease and length of stay (LOS). Methodology: It was a single-centre cross-sectional study of consecutive infants with moderate–severe bronchiolitis conducted at Pediatric Medicine Department, Federal Government Polyclinic (FGPC) Hospital, Islamabad, from 01-11-2023 to 30-04-2024. Patients were selected by clinical diagnosis using Pediatric Respiratory Severity Score (PRESS) at presentation. Serum sodium was measured and hyponatremia categorized by standard thresholds. Associations with clinical severity and LOS were tested with chi-square and correlation analyses. Multivariable logistic regression was applied to adjust for confounding variables like age and gender. SPSS version 27 was used for analysis and a P<0.05 was considered significant. Results: Data of total of n=135 eligible infants were analysed.  Hyponatremia was found in 62.2% of cases (mild 63.1%, moderate 36.9%, severe 0%) and was significantly associated with bronchiolitis severity (P<0.001) and longer durations of hospital stay (P<0.001). Serum sodium showed a strong negative correlation with PRESS (r=-0.712; P<0.001) and LOS (r=-0.594); P<0.001). In multivariable adjusted models, severe (vs moderate) bronchiolitis carried markedly greater odds of a higher hyponatremia category (aOR 6.27; 95% CI 2.25–17.45; P<0.001). Conclusions: In infants with bronchiolitis, a low admission serum sodium levels track with higher PRESS and longer LOS. An admission sodium check is recommended along with PRESS-based triage. This will help in identifying children who need closer observation.