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Updated: May 6, 2026

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Published on: April 8, 2013
Hypotonic solution decreases serum sodium in infants with moderate bronchiolitis
Regina M Rodrigues1, Benita G S Schvartsman, Sylvia C L Farhat
1Emergency Department, Instituto da Criança do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
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.
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