Nadir Oxygen Delivery During Pediatric Bypass as a Predictor of Acute Kidney Injury

Abstract

Background: Cardiac surgery-associated acute kidney injury (CS-AKI) is common in infants and is associated with negative outcomes. Nadir indexed oxygen delivery (DO₂i) during cardiopulmonary bypass (CPB) is associated with the occurrence of postoperative CS-AKI, with critical thresholds for DO₂i reported to be 262 to 300 mL/min/m² in adults. However, given that infants have a higher metabolic rate and oxygen demand, the critical DO₂i in infants is not comparable with existing adult standards. This study aimed to explore the critical DO₂i threshold during pediatric CPB.

Methods: Between March 2019 and April 2020, 106 consecutive infants undergoing cardiac surgery with CPB were admitted to this prospective observational cohort study. The DO₂i levels of each patient were monitored during CPB. Pre- and intraoperative factors were tested for independent association with CS-AKI. The postoperative outcomes of patients with or without CS-AKI were compared.

Results: In our patient population (n = 83), we identified 25 patients (38.5%) with postoperative CS-AKI. Multivariate analysis revealed 2 independent risk factors for onset of CS-AKI: CPB duration and nadir DO₂i. The lowest suitable DO₂i during CPB in the present population was 353 mL/min/m² (sensitivity, 65.6%; specificity, 74.5%). CS-AKI during pediatric CPB remained significantly associated with an increased morbidity, related mainly to a postoperative low cardiac output syndrome, but not to mortality.

Conclusions: The lowest suitable DO₂i during CPB in the infant population undergoing cardiac surgery was 353 mL/min/m². Below this threshold, there was a high probability of inducing CS-AKI.