Renal oximetry for early acute kidney injury detection in neonates with hypoxic ischemic encephalopathy receiving therapeutic hypothermia

Abstract

Background: Neonates with hypoxic ischemic encephalopathy (HIE) receiving therapeutic hypothermia are at high risk of acute kidney injury (AKI).

Methods: We performed a two-site prospective observational study from 2018 to 2019 to evaluate the utility of renal near-infrared spectroscopy (NIRS) in detecting AKI in 38 neonates with HIE receiving therapeutic hypothermia. AKI was defined by a delayed rate of serum creatinine decline (< 33% on day 3 of life, < 40% on day 5, and < 46% on day 7). Renal saturation (R_sat) and systemic oxygen saturation (SpO2) were continuously measured for the first 96 h of life (HOL). Renal fractional tissue oxygen extraction (RFTOE) was calculated as (SpO2 - R_sat)/(SpO2). Using renal NIRS, urine biomarkers, and perinatal factors, logistic regression was performed to develop a model that predicted AKI.

Results: AKI occurred in 20 of 38 neonates (53%). During the first 96 HOL, R_sat was higher, and RFTOE was lower in the AKI group vs. the no AKI group (P < 0.001). R_sat > 70% had a fair predictive performance for AKI at 48-84 HOL (AUC 0.71-0.79). RFTOE ≤ 25 had a good predictive performance for AKI at 42-66 HOL (AUC 0.8-0.83). The final statistical model with the best fit to predict AKI (AUC = 0.88) included RFTOE at 48 HOL (P = 0.012) and pH of the infants' first postnatal blood gas (P = 0.025).

Conclusions: Lower RFTOE on renal NIRS and pH on infant first blood gas may be early predictors for AKI in neonates with HIE receiving therapeutic hypothermia. A higher resolution version of the Graphical abstract is available as Supplementary information.

Keywords: Acute kidney injury; Hypoxic ischemic encephalopathy; Near-infrared spectroscopy; Neonates; Renal fractional tissue oxygen extraction; Therapeutic hypothermia.