Frequency of Hyponatremia in Children with Severe Pneumonia under the age of 5 Years

Abstract

Background: Pneumonia remains one of the leading causes of morbidity and mortality in children under five years of age, particularly in low- and middle-income countries. Electrolyte disturbances such as hyponatremia are common in severe pneumonia and may contribute to adverse outcomes, yet local data from Pakistan remain limited. Objective: To determine the frequency of hyponatremia in children under five years of age admitted with severe pneumonia. Methods: This descriptive cross-sectional study was conducted at the Paediatric ICU, Department of Pediatric Medicine Unit II, Mayo Hospital, Lahore, from 5th February 2025 to 6th June 2025. A total of 132 children aged 6 months to 5 years fulfilling inclusion criteria were enrolled through non-probability consecutive sampling. After informed consent, demographic and clinical data were collected. Serum sodium was measured at admission, 48 hours, and at discharge. Hyponatremia was defined as serum sodium <135 mmol/L. Data were analyzed using SPSS version 25.0, with stratification and chi-square testing for effect modifiers. A p-value <0.05 was considered significant. Results: The mean age of participants was 26.4 ± 14.8 months; 59.1% were male, and 62.1% belonged to rural areas. At admission, hyponatremia was present in 45 (34.1%) children, which decreased to 38 (28.8%) at 48 hours and 21 (15.9%) at discharge. Mild hyponatremia was most frequent (62.2%), followed by moderate (31.1%) and severe (6.7%). Hyponatremia was significantly more common in children under 2 years of age (44.6% vs. 23.9%, p=0.01), in rural populations (41.5% vs. 22.0%, p=0.02), and in those with symptom duration >5 days (47.8% vs. 26.7%, p=0.01). The mean hospital stay was longer in children with hyponatremia (7.1 ± 2.8 days) compared to those with normal sodium levels (5.4 ± 2.2 days, p=0.004). Conclusion: Hyponatremia is a common finding in children under five years with severe pneumonia, particularly among younger patients, those from rural areas, and those with delayed presentation. Its presence is associated with prolonged hospital stay, highlighting the importance of routine serum sodium monitoring for timely detection and management to improve outcomes.