Acute Kidney Injury in Premature, Very Low-Birth-Weight Infants

The epidemiology of neonatal acute kidney injury (AKI) is not well established, partly due to lack of a consensus definition. Preterm neonates are likely especially vulnerable to AKI. We performed a retrospective review to assess the incidence of and risk factors for AKI in very low-birth-weight (VLBW), premature infants admitted to a level 4 NICU (2006-2007). AKI was classified using a standardized definition based on changes in serum creatinine (SCr). AKI incidence varied inversely with gestational age (GA): 65% (22-25 weeks), 25% (26-28 weeks), 9% (29-32 weeks) as did severity (p < 0.001). Stage 1 AKI was most common in each cohort. Stages 2 and 3 AKI comprised approximately 60% of AKI in the 22- to 25-week cohort but 20% or less in the older cohorts. By univariate analysis, factors associated with AKI included younger GA, lower BW, lower Apgar scores, hypotension, more frequent treatment with nephrotoxic antimicrobials, longer-duration mechanical ventilation, and higher incidence of patent ductus arteriosus (PDA) requiring treatment. By multiple logistic regression analysis, only GA, hypotension, PDA, and longer duration of mechanical ventilation were independently associated with AKI. AKI was not independently associated with risk of death. Our study suggests that small increases (≥ 0.3 mg/dL) in SCr occur frequently in premature, VLBW infants, and are associated with increased morbidity but not mortality. AKI incidence and severity were highest in the youngest GA cohort. Understanding the epidemiology, risk factors, and impact of neonatal AKI is crucial as long-term premature infant survival continues to improve.