Background Acute kidney injury (AKI) is a major cause of morbidity and mortality in preterm neonates. Previous studies have shown that AKI is associated with poor outcomes but most of these studies were from single centers with small sample sizes. Objective To determine the risk factors and in-hospital outcomes associated with AKI in a national cohort of preterm infants ≤ 30 weeks gestational age (GA) and birth weight ≤ 1250g. Methods We performed a retrospective cohort study that included preterm infants ≤ 30 weeks GA and birth weight ≤ 1250g using the National Inpatient Sample (NIS) database from 2009 to 2014. The NIS is the largest publicly available all-payer inpatient healthcare database in the United States. The analysis was limited to neonates < 28 days old. Infants transferred to other hospitals were excluded to avoid double counting. We compared demographic, perinatal and clinical characteristics between those with and without AKI. Neonates with AKI were identified using International Classification of Diseases, 9th Revision, and Clinical Modification (ICD-9 CM) diagnosis codes 585.5-585.9. Continuous and categorical variables were analyzed using student t-test and chi-square as appropriate. Binary logistic regression was performed to identify independent risk factors for AKI. Further, we determined if AKI was independently associated with increased length of hospital stay (LOHS), in-hospital mortality and hospital cost. P-value <0.05 was considered statistically significant for all the analyses. Results There were 31,243 neonates ≤ 30 weeks GA, of which 809 had a diagnosis code of AKI, yielding an incidence of 2.6%. Overall, 80.6% were < 26 weeks GA, 44% were male, and 57.5% used Medicaid. AKI was significantly associated (P<0.05) with mechanical ventilation > 96 hours, patent ductus arteriosus (PDA), sepsis, and respiratory distress syndrome (RDS) and vasopressor support. On logistic regression, male gender, GA < 26 weeks and mechanical ventilation > 96 hours and PDA were independent risk factors for AKI as shown in Table 1. Compared with preterm infants without AKI, those with AKI had higher in-hospital mortality (42% vs. 29%; p < 0.0001), longer LOHS (median (IQR): 80 days [22-114] vs. 60 days [5-85]; p < 0.0001) and increased hospital cost (median [IQR]: $172,345.98 [$72,322.77-$291,646.64] vs. $94,109.52 [$27,343.84-$166,237.83]; p < 0.0001). Conclusion Independent risk factors for AKI included male sex, use of mechanical ventilation, lower GA, sepsis, and PDA. AKI was associated with increased in-hospital mortality, LOHS, and increased hospital cost. Strategies and therapies to prevent AKI are greatly needed to improve the outcomes of these vulnerable infants.

Multivariate logistic regression analysis for risk factors for neonatal AKI

Multivariate logistic regression analysis for risk factors for neonatal AKI