This project aims to explore the metabolic characteristics of adverse renal outcomes in high-risk populations after cardiac surgery by using multi-omics techniques, in order to understand the metabolic changes in patients during the process of renal function decline and recovery. At the same time, this project will search for combinations of metabolic markers that predict the occurrence of adverse outcomes, establish predictive models, to help clinical early identification and warning of AKI, and implement prevention and intervention strategies, thereby improving the prognosis of patients and enhancing the safety and success rate of cardiac surgery.

This project is a prospective observational study. It is proposed to be divided into a model development cohort and a model validation cohort. In the model development cohort, it is planned to select patients from the sample bank at high risk of AKI who underwent cardiac surgery. Pick those patients who developed AKI and who did not develop AKI for 1:1 matching, with 30 cases in each group. Blood and urine samples of the patients before the operation and 6-12 hours after cardiac surgery were collected. The non-target metabolome, proteome and transcriptome of the blood and urine samples will be detected. Through a multi-omics combined analysis strategy, significantly different metabolic pathways and metabolic molecule combinations were screened. The occurrence of postoperative AKI was taken as the main endpoint of the study. Through methods such as logistic regression, the combinations of medical history, laboratory data and specimen test results and multi-omics factors that can be used to predict and warn of the main research endpoints at an early stage were preliminarily screened. A predictive model will be established and its non-inferiority over traditional markers will be tested. At the same time, the validation cohort will be established: all high-risk populations who underwent cardiac surgery will be prospectively included. Blood and urine samples will be collected before and within 24 hours after the operation. The target metabolites will be detected in blood and urine samples by ELISA or mass spectrometry, and correlation analysis will be conducted with the research endpoint to verify the stability and reliability of the model.

Inclusion Criteria:

• All patients is going to undergo non-emergency cardiac surgeries, including cardiopulmonary bypass or non-cardiopulmonary bypass surgeries;
• Patients must have the risk of developing AKI, and at least meet one of the following criteria: cardiopulmonary bypass cardiac surgery + at least one risk factor; or non-cardiopulmonary bypass surgery such as simple coronary artery bypass grafting + at least two AKI risk factors.

The risk factors includes:

• Age ≥ 70 years;

  • Diabetes (type 1 or type 2), requiring at least one oral hypoglycemic drug or insulin;

    • 30 ≤ eGFR ≤ 60 mL/min/1.73 m2 (CKD-EPI formula);

      • Recorded history of proteinuria (random urine albumin-to-creatinine ratio UACR > 30 mg/g, or 24-hour urine albumin > 300 mg/24 hours, or urine protein ≥ +1 in urine test strips/urine routine tests);

        • Previous history of hospitalization for congestive heart failure or NYHA classification III/IV;

          • Left ventricular ejection fraction (LVEF) ≤ 40%; ⑦ Previous history of open-chest cardiac surgery;

            • CABG combined with valve surgery; ⑨ Surgery involving more than one heart valve; ⑩ Emergency surgery; ⑪ Preoperative IABP

Exclusion Criteria:

• There were urgent indications for initiating RRT at the time of enrollment, including serum potassium ≥ 6.0 mmol/L, pH value ≤ 7.20, serum bicarbonate ≤ 12 mmol/L, oxygenation index ≤ 200 mmHg; presence of volume overload, severe respiratory failure, etc.;
• Preoperative end-stage CKD (eGFR < 30 mL/min/1.73 m2; or RRT treatment had been received within 4 weeks before enrollment);
• AKI was present at screening. But transient (≤ 5 days) stage 1 AKI after iodinated contrast agent exposure will be included in this study.
• Previous kidney transplantation or urinary tract obstruction and other urinary system diseases;
• End-stage heart disease, HIV infection, hematological tumors, etc.,
• with an expected survival period of < 1 year;
• being in a moribund state (with an anticipated likelihood of death within 48 hours);
• Multiple transfers to ICU;
• Pregnant or lactating women;
• Medical or psychological conditions that the investigator believed might interfere with the subject's participation in the study, or confuse the subject's assessment or study outcome.

The incidence of cardiac surgery-associated AKI (CSA-AKI) varies from 5% to 42%. CSA-AKI is the second most common cause of AKI in the intensive care setting (after sepsis) and is independently associated with increased morbidity and mortality. Patients was diagnosed AKI by KDIGO criteria.