Evaluation of Serum Sodium Status as a Predictor of Disease Severity and Clinical Outcomes in Children with Acute Bronchiolitis Admitted To Tertiary Care Unit

Abstract

Background & Objective: Acute bronchiolitis is the predominant cause of lower respiratory tract infections (LRTIs) and pediatric intensive care unit (PICU) admissions among infants worldwide. Hyponatremia (serum sodium <135mEq/L) is a frequent electrolyte imbalance in acute respiratory conditions, typically driven by non-osmotic release of arginine vasopressin (AVP) or dilutional fluid shifts. This study evaluated the relationship between baseline serum sodium levels on admission and disease severity, duration of PICU stay, requirement for mechanical ventilation, and overall clinical outcomes among infants with acute bronchiolitis in a resource-limited tertiary care institution in Karnataka. Materials & Methods: A prospective cohort study was conducted over a two-year period in the PICU of Koppal Institute of Medical Sciences (KIMS), Koppal. Sixty (N=60) children aged 2 months to 2 years with a clinical diagnosis of acute bronchiolitis according to National Institute for Health and Care Excellence (NICE) guidelines were enrolled via convenience sampling. Serum sodium levels were determined within 18 hours of admission. Participants were stratified into two cohorts: Hyponatremic (<135 mEq/L) and Normonatremic (135-145mEq/L). Outcome parameters including oxygen support, mechanical ventilation, comorbid anemia, and length of stay in the PICU and hospital were recorded and analysed. Results: Among the 60 infants evaluated, 21 (35.00%) presented with hyponatremia, whereas 39 (65.00%) were normonatremic. Hyponatremia was most frequent among infants aged under 6 months (57.14% of hyponatremic patients; 12/21). The overall male-to-female ratio was 1.9:1. Age distribution (p = 0.834), gender (p > 0.05), and gestational maturity (p > 0.05) showed no statistically significant differences between the two cohorts. Thirty-eight infants (63.33%) required a PICU stay of <2 days, 19 (31.67%) stayed 2–4 days, and 3 (5.00%) stayed >4 days, showing no significant association with sodium status on admission. High-Flow Nasal Cannula (HFNC) support and invasive mechanical ventilation were required in one patient each. Conclusion: In this tertiary care setting, hyponatremia was a common finding in infants admitted with acute bronchiolitis—particularly among those under 6 months—but was not significantly associated with prolonged PICU stay, need for mechanical ventilation, or increased mortality. Baseline hyponatremia alone does not serve as an independent predictor of disease severity in acute bronchiolitis.