Cardiac surgery-associated acute kidney injury (CSA-AKI) is a common and important complication. The risk factors for CSA-AKI remain poorly described. We aimed to identify risk factors for CSA-AKI and develop a risk score for persistent CSA-AKI.

We performed a post hoc subgroup analysis restricted to patients who underwent cardiac surgery within the Epidemiology of Surgery Associated Acute Kidney Injury (EPIS-AKI) study. CSA-AKI was defined as AKI (according to the Kidney Disease: Improving Global Outcomes criteria) within 72 h after surgery. Persistent CSA-AKI was defined as CSA-AKI lasting >48 h. We performed multivariable logistic regression analyses to identify risk factors for CSA-AKI and related outcomes.

The original EPIS-AKI study included 3101 cardiac surgery patients. Of these, 802 (25.9%) developed CSA-AKI. On follow-up, 279 of the 802 patients (34.8%) developed persistent CSA-AKI. We identified independent risk factors for CSA-AKI, moderate/severe CSA-AKI, and persistent CSA-AKI. Patients with persistent CSA-AKI had a higher ICU and hospital mortality compared with patients with transient CSA-AKI. We developed a risk score for predicting persistent CSA-AKI with an area under the receiver operating characteristic curve of 0.79 (95% confidence interval, 0.7355–0.8457).

Overall, 25% of cardiac surgery patients developed cardiac surgery-associated acute kidney injury, and 33% of these patients experienced persistent cardiac surgery-associated acute kidney injury, which was associated with poor outcomes. We developed a risk score for predicting persistent cardiac surgery-associated acute kidney injury, the ‘EPIS CSA-AKI risk score’. Pending further external validation, the score might be used to identify patients who have a high risk for developing persistent cardiac surgery-associated acute kidney injury.