Cardiac surgery-associated acute kidney injury (CSA-AKI) is one of the most frequent and severe complications after cardiac surgery. The association between acute kidney injury and the mismatch between oxygen consumption and delivery has been well established during cardiopulmonary bypass (CPB). In this study, we aim to explore the prognostic value of the central venous-to-arterial pCO₂ gap during CPB to predict CSA-AKI.

Bicentric retrospective study conducted in two teaching hospitals. All patients who underwent cardiac surgery requiring CPB in two periods between 2019 and 2023 were screened for inclusion. Patients were divided into 2 groups according to the presence or absence of an elevated pCO₂ gap during CPB, which was defined as greater than 6 mmHg. The primary outcome was the occurrence of CSA-AKI.

Among 318 patients included, 213 were in the low pCO₂ gap group and 105 in the elevated pCO₂ gap group. No significant difference in CSA-AKI occurrence was found between groups (32.4% vs. 23.8%; p = 0.14). pCO₂ gap was not a good predictor of CSA-AKI, with an area under the curve for the ROC curve of 0.63 (p = 0.87). Except for SVO₂ during CPB, we did not find any correlation between pCO₂ gap and other tissue perfusion parameters during or after CPB.

We did not find any association between the presence of an elevated pCO₂ gap during CPB and the occurrence of CSA-AKI. This may suggest that a single intraoperative measurement of pCO₂ gap is not a reliable marker of persistent tissue hypoperfusion in this context.