(51) Changes in kidney oxygenation in preterm neonates with oliguric vs. non-oliguric acute kidney injury

Background: Acute kidney injury (AKI) in neonates can be classified by oliguric or non-oliguric as defined by the neonatal modified Kidney Disease: Improving Global Outcomes (KDIGO) guidelines. Oliguric AKI in neonates has higher mortality than non-oliguric AKI when compared to those without AKI. Kidney hypoxia ( < 50%) measured using near infrared spectroscopy (NIRS) has previously been associated with a greater AKI risk in neonates.

Objectives: Evaluate changes in kidney oxygenation between oliguric and non-oliguric AKI.

Design/Methods: In a single-center observational study from 2021-2023, preterm neonates ( < 32 weeks gestational age) had kidney oxygenation continuously measured. AKI was defined by KDIGO using serum creatinine (non-oliguric) and urine output (oliguric) criteria. Two data sets were analyzed: 1) participant level data - all kidney oxygenation data available for each participant and 2) AKI level data - kidney oxygenation 96 hours before each episode of AKI. Data was analyzed with non-parametric testing using GraphPad Prism.

Results: Of 95 preterm neonates recruited, 90 had full data for evaluation and 14 had AKI. There were 21 unique AKI episodes. 11 of 14 neonates with AKI had full kidney oxygenation data allowing for analysis of 12 of the unique AKI episodes; ten stage 1, two stage 2, and no stage 3; of these, 6 were defined as non-oliguric and 6 were defined as oliguric (Figure 1). Demographics for neonates with AKI compared to those without AKI are in Table 1. For the full kidney oxygenation monitoring, neonates with AKI had lower kidney oxygenation compared to those without AKI (59.6% vs. 69.4%, p< 0.01, Figure 2). In the 96 hours leading up to AKI, there were no differences in kidney oxygenation by those who met AKI criteria by non-oliguric vs oliguric (60.9 vs. 53.4, p =0.24). In the time prior to non-oliguric AKI diagnosis, kidney oxygenation decreased significantly (r2=0.36, p = < 0.01) whereas in the time prior to oliguric AKI diagnosis, there was no significant trend in kidney oxygenation (r2=0.01 p=0.3, Figure 3).

Conclusion: Our study aligns with previous research that preterm neonates with AKI have significantly lower kidney oxygenation than those without AKI. Preterm neonates with non-oliguric AKI had a decrease in kidney oxygenation that was significantly associated with AKI, while those with oliguric AKI did not have decreased kidney oxygenation prior to diagnosis.