Abstract

Background: Among infants undergoing cardiac surgery, AKI may affect as many as 40% of this population and carries an unfavorable prognosis. A range of contributors has been implicated, including early age, cyanotic physiology, and extended time on cardiopulmonary bypass (CPB). Nadir-indexed oxygen delivery (DO2) is an important determinant for early detection of hypoperfusion and anaerobic metabolism during CPB. This study aimed to explore the relationship between nadir DO2 during pediatric CPB and postoperative acute kidney injury. Methods: Between 1 October 2024 and 1 December 2024, we enrolled 40 children who underwent cardiac surgery with CPB [median age 6 months (IQR 4–8), median weight 5.5 kg (IQR 5–7 kg)] into an observational cohort. DO2 was tracked intraoperatively for every patient, and pre- as well as intraoperative variables were examined for independent links to AKI. Postoperative outcomes were then compared between patients who did and did not develop AKI. Results: In our patient population (n = 40), 16 patients (40%) developed AKI according to the pRIFLE criteria (75% risk; 18.7% injury; 6.2% failure; no patient was in the loss or end-stage renal disease categories). Lower nadir DO2 values were associated with postoperative AKI in this exploratory pilot cohort. ROC analysis identified an exploratory nadir DO2 threshold of 360 mL/min/m2 (sensitivity 70%, specificity 80%) associated with postoperative AKI. Because this threshold was both derived and evaluated within the same cohort without validation, it should be regarded only as a preliminary, hypothesis-generating observation with no implication of clinical applicability and requires validation in larger independent cohorts. Conclusions: In this exploratory pilot cohort, lower nadir DO2 during cardiopulmonary bypass was independently associated with postoperative AKI. An exploratory ROC-derived threshold of 360 mL/min/m2 was identified; however, this threshold should be considered hypothesis-generating rather than clinically validated. The consistency of findings across both dichotomous and continuous DO2 analyses strengthens the robustness of the observed association, although larger prospective studies are required to externally validate this threshold, which at present carries no implication of clinical applicability.

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