Association between Serum Hyponatremia and Severity of Respiratory Symptoms in Infants with Respiratory Syncytial Virus Infection

Purpose: Association between hyponatremia and the severity of respiratory symptoms in infants with respiratory syncytial virus (RSV) infection has not yet been studied. This study aimed to compare respiratory symptoms, assessed using the Pediatric Res­ piratory Score (PRS), in infants with RSV infection, with or without hyponatremia. Methods: RSV­positive patients aged <12 months who were admitted with respiratory symptoms within 7 days of onset at Jeonbuk National University Children’s Hospital from January 2016 to December 2019 were retrospectively analyzed. Each patient was categorized into those with or without hyponatremia (serum sodium concentration of <136 mmol/L). Clinical findings included PRS on the day of admission. Results: The mean±standard deviation age of the 125 patients included in the study was 2.7±3.3 months, and, 20 patients (16.0%) showed hyponatremia. Infants with RSV infection and hyponatremia had lower birth weights, longer hospital stays, and higher blood urea nitrogen level. The C­reactive protein level was significantly higher in the hyponatremic infants, who had higher PRSs. The non­hyponatremia group had more normal PRSs than the hyponatremia group, which had more severe PRSs. After adjustment for age at admission, blood urea nitrogen level (OR, 1.218; 95% CI, 1.023 to 1.451; P<0.05), and PRS grade (OR, 2.885; 95% CI, 1.158 to 7.187; P< 0.05) were identified as independent risk factors. Conclusion: Hyponatremia was strongly associated with respiratory severity in infants with RSV. Therefore, infants admitted with RSV infection who show higher PRS grade need to be evaluated and treated for hyponatremia.