This project aims to detect novel biomarkers from preoperative and early postoperative serum and urine samples of patients to screen and analyze the risk factors for predicting adverse postoperative renal outcomes in high-risk patients in cardiac surgery.

This project will prospectively collect all high-risk individuals who underwent cardiac surgery, collect medical history, laboratory data and specimen test results, and test biomarkers in blood and urine specimens. Previously identified candidate biomarkers include the tumor necrosis factor-like weak inducer of apoptosis receptor (TWEAKR), galectin-9 (Gal-9), perilipin-2 (Plin2), and CCN family member 1, among others. The occurrence of postoperative AKI will be the primary endpoint of the study. The variable factors that can be used to predict and warn the main research endpoints at an early stage were screened through methods such as logistic regression, and their non-inferiority compared with traditional markers was tested. This study will facilitate early clinical identification and early warning of AKI, early implementation of preventive measures and intervention strategies, thereby improving the prognosis of patients and improve the overall safety and success rate of cardiac surgery.

Adult patients were included in the study if they were scheduled for elective open chest cavity cardiac surgeries, with or without the use of cardiopulmonary bypass (CPB). Inclusion criteria required that patients undergoing surgery with CPB must have at least one AKI risk factor, whereas those undergoing surgery without CPB needed to have at least two AKI risk factors.

The AKI risk factors were as follows:

• age >70 years;
• 30 < estimated glomerular filtration rate (eGFR) <60 mL·min-1·1.73 m-2;
• diabetes mellitus, proteinuria;
• a history of congestive heart failure within the previous year;
• a left ventricular ejection fraction of 40% or lower;
• prior cardiac surgery;
• combined coronary artery bypass/valve procedure;
• urgent procedure;
• preoperative intra-aortic balloon pump.

Exclusion criteria:

• pre-existing chronic kidney disease (preoperative estimated glomerular filtration rate [eGFR] < 30 mL/min/1.73 m2);
• previous RRT before cardiac surgery;
• present AKI at screening;
• a history of kidney transplant or other kidney diseases;
• known pregnancy;
• multiple operation during the hospital stay;
• being in a moribund state (with an anticipated likelihood of death within 48 hours).

All high-risk AKI patients who underwent cardiac surgery at Zhongshan Hospital Affiliated to Fudan University.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. The incidence of cardiac surgery-associated AKI (CSA-AKI) varies from 5% to 42%.