The goal of this clinical trial is to assess the effect of RenalGuard Therapy in reducing the rates of Acute Kidney Injury (AKI) within 72 hours after cardiac surgery in patients at risk of developing Cardiac Surgery Associated AKI (CSA-AKI) compared to standard-of-care (SoC).

The study is planned to be conducted in 2 clinical sites in the Malaysia - Universiti Malaya Medical Centre and Institut Jantung Negara, Kuala Lumpur, Malaysia.

Participants will be randomized (1:1) to one of the two study groups. The Treatment study group will be managed with the RenalGuard System. The RenalGuard treatment will start after induction of anesthesiology and will run during surgery and for 6-7 hours in the Intensive Care Unit (ICU). The treatment will aim to achieve a urine rate above a predefined urine rate threshold. Patients in the control group will be managed based on the usual clinical practice in cardiac surgery centres as detailed in the recommendations for CSA-AKI prevention by accepted clinical guidelines.

For both study groups general anaesthesia, cardiopulmonary bypass (CPB) run and overall patient care will be based on SoC for cardiac surgery.

Patients will be followed up for up to 7 days post surgery or until discharge, which ever comes first.

Long-term follow up will be performed at 90 days post surgery.

Inclusion Criteria:

1. Male or female and >18 years old.

2. Patient able to give written consent.

3. Scheduled for the following non-emergent cardiac surgery procedure requiring CPB, isolated or in combination:

   • coronary artery bypass graft (CABG)
   • aortic valve replacement or repair alone, with or without aortic root repair
   • mitral, tricuspid, or pulmonic valve replacement or repair
   • simultaneous replacement of several cardiac valves
   • CABG with aortic, mitral, tricuspid, or pulmonic valve replacement or repair
   • Surgery on the aorta: aortic root and/ or ascending aorta
   • AF ablation surgery if combined with other cardiac procedures.
   • ASD closure if combined with other cardiac procedures.
   • Excision of myxoma if combined with other cardiac procedures

4. Have at least one of the following risk factors for CSA-AKI:

   • CKD-EPI eGFR 20-59 mL/min/1.73 m²
   • Undergoing combined surgery (e.g. CABG + Valve)
   • STS Score ≥4 or Logistic EuroScore of ≥5 or, Euroscore II of ≥4
   • Left ventricular ejection fraction (LVEF) ≤ 35%
   • Insulin-requiring diabetes
   • Non-insulin-requiring diabetes with HbA1C ≥ 6.1% in the last 6 months
   • Preoperative anemia (hemoglobin ≤11g/dl for men and women) within 4 weeks of surgery

Exclusion Criteria:

1. Patient requiring emergency surgery
2. Surgery to be performed without CPB
3. Patient receiving furosemide at a dose>100 mg/day orally (or the equivalent dose of an alternative loop diuretic) in the last week
4. Patient who cannot be urethrally catheterize for any reason
5. Patients already dialysis dependent
6. Patients with CKD-EPI eGFR <20 mL/min/1.73 m²
7. Known or suspected AKI (KDIGO criteria) at the time of screening
8. IV contrast within 48 hours of surgery
9. Patients participating in another interventional drug or device study or have received an investigational drug or device treatment within the last 30 days
10. Pregnant patient, self-reported
11. Patients whose planned surgery to be performed under conditions of circulatory arrest or hypothermia with rectal temperature < 28°Celsius (82.4° Fahrenheit)
12. Patient with suspected or confirmed bacteraemia, endocarditis, or pyelonephritis at hospital admission
13. Patients with pneumonia, aspiration, or bilateral pulmonary infiltrates from an infectious aetiology reported on chest x-ray or CT scan in the last 7 days
14. Patients in cardiogenic shock or hemodynamic instability which require inotropes or vasopressors or other mechanical devices (Impella, IABP) within 24 hours prior to surgery
15. Patients on extracorporeal membrane oxygenation (ECMO) or durable ventricular assist device (VAD) at the time of screening, or planned use within 24h prior to surgery
16. Patients currently treated with chemotherapy or radiation therapy that may have an impact on kidney function.
17. Patient underwent prior solid organ transplantation
18. Patients underwent major surgery within the last 3 months
19. Any condition which, in the judgement of the investigator, might increase the risk to the patient

After completion of the study, information regarding the protocol and statistical analysis plan will be shared on request. Additionally anonymised data will be available upon reasonable request.