Association between 24-hour urine output during early non-invasive ventilation and short-term adverse outcomes in late preterm infants: a retrospective cohort study.

Background: Despite advances in respiratory management, late preterm infants with severe pneumonia requiring non-invasive ventilation (NIV) remain at risk of short-term adverse outcomes, and early identification of at-risk infants remains challenging. Current clinical assessment during NIV largely relies on respiratory severity and inflammatory parameters, which may not fully capture evolving systemic physiological changes related to circulatory adaptation and organ perfusion. Urine output during the first 24 hours of NIV support is a routinely monitored bedside parameter that may reflect renal perfusion and hemodynamic status and may provide complementary prognostic information beyond conventional indicators. However, whether early urine output is independently associated with short-term adverse outcomes in this population remains unclear. This study aimed to investigate the association between early 24-hour urine output and short-term adverse outcomes in late preterm infants with severe pneumonia receiving NIV support. Methods: This retrospective cohort study included 240 late preterm infants with severe pneumonia admitted to the neonatal intensive care unit (NICU) between June 2023 and December 2025. Short-term adverse outcomes were defined as a composite endpoint including NIV failure, persistent severe hypoxemia, respiratory deterioration, and multiple organ dysfunction syndrome (MODS) within 7 days after NIV initiation. Perinatal characteristics, admission data, and dynamic clinical parameters during the early NIV period were collected. Multivariable logistic regression analysis was performed to identify factors associated with adverse outcomes. Receiver operating characteristic (ROC) analysis was performed as an exploratory analysis to assess the discriminatory performance of 24-hour urine output for short-term adverse outcomes. Results: Among the 240 enrolled infants, 41 (17.1%) developed short-term adverse outcomes. Multivariable logistic regression analysis demonstrated that lower 5-minute Apgar score, higher procalcitonin (PCT) level, and 24-hour urine output were independently associated with short-term adverse outcomes. Lower 24-hour urine output was significantly associated with increased risk of adverse outcomes [adjusted odds ratio (OR) =0.208, 95% confidence interval (CI): 0.107-0.404, P<0.001]. Sensitivity analyses yielded generally consistent findings. Conclusions: Among late preterm infants with severe pneumonia receiving NIV support, lower early 24-hour urine output was associated with a higher risk of short-term adverse outcomes. As a routinely available parameter, 24-hour urine output may provide complementary prognostic information alongside conventional clinical indicators. Further prospective validation is required before its potential clinical application can be determined.