Early fluid status and severe intraventricular hemorrhage or death in extremely preterm infants.

Background: Measures of early postnatal fluid balance may be associated with severe intraventricular hemorrhage (sIVH) and/or death in extremely preterm infants in the first postnatal week.

Methods: A single-center, retrospective cohort study including actively treated inborn infants weighing ≥ 400 g and 22-27 weeks' gestation from 2014-2021. Longitudinal mixed effect models compared daily fluid balance covariates including serum sodium, percent weight change, total fluid intake, urine output, and fluid balance (daily weight - birth weight /birth weight × 100) among infants with and without sIVH or death, during the first seven postnatal days. Multiple regression and machine learning models were developed to predict sIVH and/or death. Variables that were incorporated into the models included measures of fluid balance, gestational age, birth weight, antenatal corticosteroids, multiples, and sex.

Results: We included 932 infants with mean ± SD gestational age of 25w2d ± 11d and birth weight of 746 ± 212 g of whom 195 (20.9%) had sIVH and/or death. Lower percentage weight change (p < 0.001), higher total fluid intake (p = 0.007), higher sodium (p = 0.007), and positive early fluid balance (p < 0.001) were associated with sIVH and/or death even after adjustment for baseline characteristics. The area under the receiver-operating curve (AUC) for regression models predicting sIVH and/or death incorporating baseline characteristics improved after adding fluid balance measures from 0.75 to 0.80, while the AUC for machine learning models improved from 0.72 to 0.84.

Conclusions: In extremely preterm infants, early fluid status measures were associated with risk of sIVH and/or death. The addition of fluid status measures improves the performance of models predicting sIVH and/or death.