rhBNP for Prevention of Cardiac Surgery-Associated Acute Kidney Injury (CSA-AKI)

Inclusion Criteria: * Age ≥ 18 years * Scheduled (elective) cardiac surgery requiring cardiopulmonary bypass * Presence of at least one of the following AKI risk factors: * Age ≥ 70 years * Preoperative renal impairment (eGFR ≤ 60 mL/min/1.73 m² or urine protein ≥ +2 at screening) * Type 2 diabetes mellitus * Heart failure, defined as NYHA Class II-IV with NT-proBNP ≥ 125 pg/mL at screening; for participants with atrial fibrillation, NT-proBNP ≥ 365 pg/mL is required * Able to understand and provide written informed consent, and willing and able to comply with all study protocol requirements Exclusion Criteria: * Cardiogenic shock * Severe hypotension (systolic blood pressure ≤ 90 mmHg) at screening * Restrictive or obstructive cardiomyopathy, pericarditis, or cardiac tamponade * Preoperative chronic kidney disease stage 4 or higher (eGFR \< 30 mL/min/1.73 m²), or renal instability as judged by the investigator * Known AKI diagnosed per KDIGO criteria within 48 hours prior to surgery * Receipt of any form of renal replacement therapy within 30 days prior to surgery * Use of ventricular assist device, intra-aortic balloon pump, or any other mechanical cardiac support device within 7 days prior to surgery * Chronic hepatic insufficiency (Child-Pugh Class B or C) or hepatic dysfunction (ALT or AST \> 2× upper limit of normal \[ULN\], or total bilirubin \> 1.5× ULN) * Active hepatitis B (HBsAg positive with HBV-DNA indicating active viral replication), active hepatitis C (HCV antibody positive with HCV-RNA indicating active viral replication), positive syphilis screen, known HIV infection, or positive HIV test * Confirmed or treated endocarditis, sepsis, or active infection requiring antibiotic treatment within 30 days prior to surgery * Requirement for aortic dissection repair, complex congenital heart surgery, emergency surgery, or life-saving surgery * History of malignant tumor, solid tumor, metastatic tumor, or hematological malignancy within the past 5 years * Prior organ transplantation or current use of immunosuppressive agents * Any condition that may conflict with or contraindicate the use of intravenous vasodilator therapy * Prior adverse reaction to nesiritide (recombinant BNP) * Participation in any other clinical trial within 30 days prior to surgery * Pregnant or breastfeeding women * Any other condition that, in the judgment of the investigator, renders the participant unsuitable for study participation