Nadir oxygen delivery is associated with postoperative acute kidney injury in low-weight infants undergoing cardiopulmonary bypass

Background Acute kidney injury (AKI) is common after cardiac surgery with cardiopulmonary bypass (CPB) and is associated with increased mortality and morbidity. Nadir indexed oxygen delivery (DO2i) lower than the critical threshold during CPB is a risk factor for postoperative AKI. The critical DO2i for preventing AKI in children has not been well studied. The study aimed to explore the association between nadir DO2i and postoperative AKI in infant cardiac surgery with CPB. Methods From August 2021 to July 2022, 413 low-weight infants (≤10 kg) undergoing cardiac surgery with CPB were consecutively enrolled in this prospective observational study. Nadir DO2i was calculated during the hypothermia and rewarming phases of CPB, respectively. The association between nadir DO2i and postoperative AKI was investigated in mild hypothermia (32–34°C) and moderate hypothermia (26–32°C). Results A total of 142 (38.3%) patients developed postoperative AKI. In patients undergoing mild hypothermia during CPB, nadir DO2i in hypothermia and rewarming phases was independently associated with postoperative AKI. The cutoff values of nadir DO2i during hypothermia and rewarming phases were 258 mL/min/m2 and 281 mL/min/m2, respectively. There was no significant association between nadir DO2i and postoperative AKI in patients undergoing moderate hypothermia during CPB. Conclusion In low-weight infants undergoing mild hypothermia during CPB, the critical DO2i for preventing AKI was 258 mL/min/m2 in the hypothermia phase and 281 mL/min/m2 for rewarming. Moreover, an individualized critical DO2i threshold should be advocated during CPB.