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) and contributes to the development of CSA-AKI. In this study, the investigators aim to explore the use of gap CO2 during cardiac surgery and its relation with CSA-AKI. In order to explore this association, the invetigators built a retrospective, multicentric study. All patient who underwent cardiac surgery with cardiopulmonary bypass in two French ICU between 03/2019 and 04/2023 and for which information about gap CO2 during CPB is available will be included. After inclusion, patient will be divided in two groups according to the presence or absence of an elevated gap CO2. Occurence of CSA-AKI and other outcomes will be compared between groups, using multivariate analysis.

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) and contributes to the development of CSA-AKI. In order to explore this association, investigators build a retrospective study including all patients who underwent cardiac surgery requiring CPB in two French hospitals and for which data about gap CO2 during CPB is available. Patients will be divided into two groups according to the presence or absence of an elevated gap CO2 during CPB, defined as > 6 mmHg. The primary outcome is the occurrence of CSA-AKI, defined by KDIGO recommendations, according gap CO2. Secondary outcomes include others post-operative complications as defined by international guidelines. Performance of gap CO2 to predict CSA-AKI will be evaluated by calculating the Area Under the Curve (AUC) of the associated ROC curve. We'll also assess the correlation between gap CO2 and other perfusion parameters (lactate, svO2) and with mean DO2 during CPB.

Inclusion criteria:

1. Informed patients who did not object to the use of their data in the study.
2. Patients undergoing cardiac surgery with extracorporeal circulation.
3. Patients for whom a pCO2 gap measurement is available during ECG.

Non-inclusion criteria :

1. Heart transplant patients
2. Patients who have received long-term cardiac assistance
3. Minor patients

Patients older than 18, which underwent cardiac surgery with cardiopulmonary bypass

The procedures carried out with the French data privacy authority (CNIL, Commission nationale de l'informatique et des libertés) do not provide for the transmission of the database, nor do the information and consent documents signed by the patients.

Consultation by the editorial board or interested researchers of individual participant data that underlie the results reported in the article after deidentification may nevertheless be considered, subject to prior determination of the terms and conditions of such consultation and in respect for compliance with the applicable regulations.

Beginning 3 months and ending 3 years following article publication. Requests out of these time frame can also be submitted to the sponsor

Researchers who provide a methodologically sound proposal.