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

Background

Cardiac surgery associated acute kidney injury (CS-AKI) is common in infants and associates with negative outcomes. Nadir indexed oxygen delivery (DO ₂i) during cardiopulmonary bypass (CPB) is associated with the occurrence of postoperative CS-AKI, with ‘critical thresholds’ for DO ₂i reported to be 262–300 mL/min/m ² in adults. However, given that infants have a higher metabolic rate and oxygen demand, the critical DO ₂i in infants cannot be referred to the existing adults’ standard. This study aimed to explore the critical DO ₂i threshold during pediatric CPB.

Methods

Between March 2019 and April 2020, 106 consecutive pediatric patients undergoing cardiac surgery with CPB were admitted to this prospective observational cohort study. The DO ₂i levels of each patient were monitored during CPB. Pre- and intraoperative factors were tested for independent association with CS-AKI. The postoperative outcome of patients with or without CS-AKI was 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 DO ₂i. The lowest suitable DO ₂i during CPB in the present population was 353 mL/min/m ² (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 DO ₂i during CPB in the present population undergoing pediatric cardiac surgery was 353 mL/min/m ². And below this threshold, there was a high probability of inducing CS-AKI.