Incidence, risk factors and outcomes of postoperative acute kidney injury requiring dialysis after cardiac surgery: a retrospective study from the National Heart Institute of Malaysia.

BACKGROUND

Acute kidney injury (AKI) requiring dialysis is a rare but devastating complication following cardiac surgery, associated with significant morbidity and mortality. While chronic kidney disease (CKD) is a known risk factor, the impact of other perioperative variables and the differential outcomes between CKD and non-CKD patients remain inadequately defined.

OBJECTIVE

To determine the incidence, risk factors, and outcomes of AKI requiring dialysis after cardiac surgery, with stratification by baseline renal function.

METHODS

This retrospective cohort study included adult patients undergoing coronary artery bypass grafting, valve surgery, or combined procedures at the National Heart Institute of Malaysia between January 2022 and July 2024. AKI was defined using KDIGO criteria, and patients with end-stage renal disease on chronic dialysis were excluded. Multivariable logistic regression identified predictors of dialysis-requiring AKI. Propensity score matching was used to compare outcomes between patients with and without CKD.

RESULTS

Among 6,779 patients, the incidence of AKI requiring dialysis was 4.5%. The incidence was significantly higher in patients with CKD (13.9%) compared to matched non-CKD patients (5.5%). Independent predictors included advanced age (AOR 1.038, 95% CI 1.003–1.073), urgent surgery (AOR 2.393, 95% CI 1.211–4.726), diabetes mellitus (AOR 1.798, 95% CI 1.001–3.231), reoperation (AOR 7.202, 95% CI 4.127–12.568), and prolonged ICU stay (AOR 1.148, 95% CI 1.081–1.220). Coronary angiography timing was not associated with increased risk. Mortality was 45.1% among CKD patients and 53.3% among non-CKD patients who developed dialysis-requiring AKI. Compared to those without AKI, mortality risk increased 16-fold in CKD and 30-fold in non-CKD patients. ICU stay was prolonged by approximately two weeks in affected patients.

CONCLUSION

AKI requiring dialysis after cardiac surgery is associated with dramatically increased mortality and healthcare resource utilization, particularly in patients without preexisting CKD. Several modifiable perioperative factors contribute to risk. These findings support the need for early risk stratification, perioperative kidney-protective strategies, and multidisciplinary planning to prevent this serious complication.