Importance  Acute kidney injury (AKI) after cardiac surgery is a common and serious complication. Protein loading appears nephroprotective; thus, continuous hyperoncotic albumin infusion may impact AKI following high-risk cardiac surgery.

Objective  To evaluate the effect of postoperative 20% albumin infusion compared with usual care on the occurrence of AKI in high-risk cardiac surgery patients.

Design, Setting, and Participants  This was an investigator-initiated randomized multicenter open-label pragmatic clinical trial. Participants were stratified by site and estimated glomerular filtration rate (eGFR) above and below 60 mL/min/1.73 m². The study was conducted at 7 cardiac centers in Australia and Italy between July 2019 and August 2024. Patients undergoing on-pump cardiac surgery with a preoperative eGFR of greater than 15 mL/min/1.73 m² and less than 60 mL/min/1.73 m² or undergoing a combined cardiac surgical procedure or major aortic surgery were included, excluding those who were in intensive care for longer than 6 hours following the index surgery, had a serum albumin level less than 20 g/L, were dialysis dependent, had a previous kidney transplant, were receiving extracorporeal life support or ventricular assist device, or had an objection to receiving albumin or blood products.

Interventions  Participants were randomized 1:1 within 6 hours after surgery to receive a 300-mL infusion of 20% albumin over 15 hours or usual care, as per clinician discretion. All patients received volume resuscitation and hemodynamic treatment according to participating centers’ protocols.

Main Outcomes and Measures  The primary outcome was stage 1-3 AKI according to the creatinine-based Kidney Disease Improving Global Outcomes definition. The main secondary outcomes included major adverse kidney events and mortality at hospital discharge or day 28 following randomization.

Results  The primary analysis included 307 patients randomized to the 20% albumin group and 304 to usual care. The mean (SD) age was 69 (10.8) years, and 281 patients (45.8%) had an eGFR less than 60 mL/min/1.73 m². The median (IQR) European System for Cardiac Operative Risk Evaluation score-II was 3.23 (1.91-5.30). AKI occurred in 150 of 307 patients in the albumin group (48.9%) vs 132 of 304 in usual care (43.4%) (unadjusted relative risk, 1.13; 95% CI, 0.95-1.34; P = .18; strata-adjusted relative risk, 1.12; 95% CI, 1.04-1.21; P = .003). This effect was more pronounced in patients with an eGFR of <60 mL/min/1.73 m² (adjusted relative risk, 1.14; 95% CI; 1.07-1.22; P < .001). There were more blood transfusions given in the albumin group (116 [37.8%] vs 91 [29.9%]; P = .04) but no other significant differences in secondary outcomes.

Conclusions and Relevance  In this study of cardiac surgery patients at high risk of AKI, an infusion of 20% albumin increased the risk of AKI. These findings do not support the routine use of hyperoncotic albumin infusion in patients undergoing high-risk cardiac surgery.