Preceding risks and mortality outcomes of different neonatal acute kidney injury in preterm infants

BackgroundThe aim of the study was to examine preceding risks and mortality outcomes of oliguric and non-oliguric acute kidney injury (AKI) in very preterm infants.MethodsInfants born <= 30 weeks' gestation were included. AKI was diagnosed based on neonatal Kidney Disease: Improving Global Outcomes criteria and was classified as oliguric and non-oliguric according to the urine-output criteria. We used modified Poisson and Cox proportional-hazards models for statistical comparisons.ResultsOf 865 enrolled infants (gestational age 27.2 +/- 2.2 weeks and birth weight 983 +/- 288 gm), 204 (23.6%) developed AKI. Before AKI, the oliguric AKI group had significantly higher prevalence of small-for-gestational age (p = 0.008), lower 5-min Apgar score (p = 0.009) and acidosis (p = 0.009) on admission, and hypotension (p = 0.008) and sepsis (p = 0.001) during admission than the non-oliguric AKI group. Oliguric (adjusted risk ratio 3.58, 95% CI 2.33-5.51; adjusted hazard ratio 4.93, 95% CI 3.14-7.72) instead of non-oliguric AKI had significantly higher mortality risks than no AKI. Oliguric AKI showed significantly higher mortality risks than non-oliguric AKI, irrespective of serum creatinine and severity of AKI.ConclusionsCategorizing AKI as oliguric and non-oliguric was crucial because of the distinct preceding risks and mortality outcomes of these two types of AKI in very preterm neonates.ImpactThe differences of the underlying risks and prognosis between oliguric and non-oliguric AKI in very preterm infants remain unclear.We found that oliguric AKI, but not non-oliguric AKI, carries higher mortality risks than infants without AKI. Oliguric AKI possessed higher mortality risks than non-oliguric AKI, irrespective of concomitant serum creatinine elevation and severe AKI.Oliguric AKI is more associated with prenatal small-for-the-gestational age and perinatal and postnatal adverse events, while non-oliguric AKI is associated with nephrotoxins exposures.Our finding highlighted the importance of oliguric AKI and is helpful in developing future protocol in neonatal critical care.