A new approach to recognize term and preterm infants with impaired kidney function (IKF) during the first week of life

Background Current definitions of neonatal acute kidney injury (nAKI) are not sensitive enough to identify all newborns with impaired kidney function (IKF) during the first week of life. Previous studies in term newborns with hypoxic ischemic encephalopathy showed that the rate of serum creatinine (SCr) decline during the first week of life could be used to assess their renal status. Methods We reviewed the medical records of 329 critically ill newborns ≥ 27 weeks of gestational age (GA), to determine whether the rate of SCr decline combined with SCr thresholds provides a sensitive approach to identify newborns with IKF during the first week of life. Results Excluding neonates with nAKI, identified based on standard definitions, a SCr decline < 31 % by the 7 th day of life, combined with a SCr threshold ≥ 0.7 mg/dl, recognized newborns of 40-31 weeks of GA with IKF. A SCr decline < 21% combined with a SCr threshold ≥ 0.8 mg/dl identified newborns of 30-27 weeks of GA with IKF. These neonates (~ 17%) showed a more prolonged hospital stay and required more days of mechanical ventilation, vasoactive drugs, and diuretics, when compared to critically ill controls. Changes in urine output did not distinguish newborns with IKF. Conclusion The rate of SCr decline combined with SCr thresholds identifies newborns with IKF during the first week of life. This distinctive group of newborns that is missed by standard definitions of nAKI, warrants close monitoring in the NICU to prevent acute and chronic renal complications.