The lower threshold of hypothermic oxygen delivery to prevent neonatal acute kidney injury

Abstract

Background: Oxygen delivery during cardiopulmonary bypass (CPB) is closely related to postoperative acute kidney injury (AKI). The value of critical indexed oxygen delivery (DO₂i) is a key indicator to reflect oxygen supply in cardiovascular surgery. However, the target DO₂i value for neonates undergoing hypothermic CPB remains unclear.

Methods: One hundred and twenty-six consecutive newborns (≤28 days) undergoing arterial switch operations were retrospectively divided into two groups according to AKI occurrence. Baseline characteristics, intraoperative variables, and clinical outcomes were collected. Multivariate logistic regression analysis and receiver-operating characteristic curve were performed to investigate the association between DO₂i and AKI.

Results: Neonates in the no-AKI group (n = 67) had significantly higher nadir bypass flow and DO₂i during the hypothermic phase compared with the AKI group (n = 59). AKI group had remarkably higher incidences of hepatic dysfunction and peritoneal dialysis requirement compared with newborns without AKI. Mixed venous oxygen saturation (SvO₂) was comparable between the two groups. Base excess (BE)(P = 0.011) value during the hypothermic phase of the AKI group was higher than the no-AKI group. Multivariate analysis showed that hypothermic DO₂i was negatively associated with AKI. The cut-off value of hypothermic DO₂i was 269 mL min^-1 m^-2.

Conclusions: The importance of hypothermic DO₂i should be highlighted, even when SvO₂ was satisfactory. A lower threshold of DO₂i > 269 mL min^-1 m^-2 may help protect neonates from the risk of postoperative AKI.

Impact: The key message of our article is that the lower threshold of DO₂i > 269 mL min^-1 m^-2 may help protect neonates from the risk of AKI after on-pump hypothermic cardiovascular surgery. The critical DO₂i value for neonates undergoing hypothermic CPB remains unclear, and our study may add new evidence for this matter based on the 6-year experience of our center. In this study, the lowest critical value of DO₂i in neonatal hypothermic CPB is determined for the first time, which provides a reference for intra-CPB management strategy to improve the postoperative outcomes of newborns.