Hyponatremia in infants with new onset moderate-severe bronchiolitis : a cross-sectional study

BACKGROUND: The reported cumulative prevalence of hyponatremia (sodium <135 mmol/L) in bronchiolitis is 28%. However, sodium level was never measured by direct potentiometry, the method recommended by the International Federation of Clinical Chemistry and Laboratory Medicine. Aim of this study was to assess the prevalence of hyponatremia, measured by direct potentiometry, in infants with moderate-severe bronchiolitis. METHODS: A prospective cross-sectional study was conducted in infants ≥1month and ≤24months of age with bronchiolitis. RESULTS: 160 consecutive infants were enrolled. Hyponatremia was observed in 91 (57%) patients and occurred more commonly in infants ≤6 months than in older infant (P < 0.005). CONCLUSION: The first study on sodium level measured by the direct potentiometry in infants with bronchiolitis points out that the prevalence of hyponatremia is two-fold higher than so far reported.