Fluid status in the first 10 days of life and death/bronchopulmonary dysplasia among preterm infants

Objective To investigate the association between fluid and sodium status in the first 10 postnatal days and death/bronchopulmonary dysplasia (BPD) among infants born <29 weeks’ gestation. Study design Single center retrospective cohort study (2015–2018) of infants born 23–28 weeks’. Three exposure variables were evaluated over the first 10 postnatal days: cumulative fluid balance (CFB), median serum sodium concentration, and maximum percentage weight loss. Primary outcome was death and/or BPD. Multivariable logistic regression adjusting for patient covariates was used to assess the association between exposure variables and outcomes. Results Of 191 infants included, 98 (51%) had death/BPD. Only CFB differed significantly between BPD-free survivors and infants with death/BPD: 4.71 dL/kg (IQR 4.10–5.12) vs 5.11 dL/kg (IQR 4.47–6.07; p < 0.001). In adjusted analyses, we found an association between higher CFB and higher odds of death/BPD (AOR 1.56, 95% CI 1.11–2.25). This was mainly due to the association of CFB with BPD (AOR 1.60, 95% CI 1.12–2.35), rather than with death (AOR 1.08, 95% CI 0.54–2.30). Conclusion Among preterm infants, a higher CFB in the first 10 days after delivery is associated with higher odds of death/BPD. Impact Previous studies suggest that postnatal fluid status influences survival and respiratory function in neonates. Fluid balance, serum sodium concentration, and daily weight changes are commonly used as fluid status indicators in neonates. We found that higher cumulative fluid balance in the first 10 days of life was associated with higher odds of death/bronchopulmonary dysplasia in neonates born <29 weeks. Monitoring of postnatal fluid balance may be an appropriate non-invasive strategy to favor survival without bronchopulmonary dysplasia. We developed a cumulative fluid balance chart with corresponding thresholds on each day to help design future trials and guide clinicians in fluid management.