Hypotonic solution decreases serum sodium in infants with moderate bronchiolitis.

Aim: To investigate the influence of hypotonic parenteral hydration on serum and urinary sodium and osmolality in infants with moderate bronchiolitis.
Methods: We studied 36 infants (mean age 3.7 ± 2.3 months), with a diagnosis of moderate bronchiolitis admitted to a paediatric emergency unit in São Paulo, Brazil. Patients received a standard parenteral hypotonic solution, according to Holliday and Segar, during the first 24 h, due to respiratory distress. The disease was monitored by a respiratory severity score (RDAI-Respiratory Distress Assessment Instrument), respiratory rate and oxygen saturation. Serum and urinary sodium and osmolality were monitored at admission, 24 and 48 h after admission.
Results: All respiratory parameters improved during hospitalisation. Serum sodium and osmolality dropped after 24 h (136.8 ± 2.8 and 135.8 ± 2.6 mEq/L, p = 0.031; 283.4 ± 4.1 and 281.6 ± 3.9 mOsm/kg, p = 0.004 respectively) as well as urinary osmolality (486.8 ± 243.4 mOsm/kg and 355.7 ± 205.0 mOsm/kg, p < 0.001) when compared to admission.
Conclusion: This study reinforces the occurrence of hyponatraemia in bronchiolitis even in patients with moderate disease and highlights the risk of serum sodium drop caused by hypotonic parenteral hydration.
(©2013 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.)