Postoperative Acute Kidney Injury in Cardiovascular Surgery Patients with Prolonged Intensive Care Unit Stay: Impact on Mortality and Outcomes

Abstract

Objective To evaluate the association between postoperative acute kidney injury (AKI) and outcomes in adults undergoing cardiovascular surgery who required a prolonged intensive care unit (ICU) stay. Methods We conducted a retrospective cohort study of consecutive cardiovascular surgery patients with ICU stay ≥ 72 hours. AKI was defined and staged using creatinine-based Kidney Disease: Improving Global Outcomes (KDIGO) criteria. The primary outcome was in-hospital mortality. Secondary outcomes were time to extubation, ICU days until ward transfer, and perioperative transfusion exposure (red blood cells/fresh frozen plasma/platelet/apheresis); initiation of renal replacement therapy was assessed exploratorily. Multivariable logistic regression examined the association between AKI and mortality, adjusting for age, sex, baseline renal function/chronic kidney disease (estimated glomerular filtration rate category), hypertension, diabetes, chronic obstructive pulmonary disease, ejection fraction (or Age Creatinine Ejection Fraction score), procedure type (coronary artery bypass grafting/valve/combined), cardiopulmonary bypass and cross-clamping times, transfusions, and post-cardiopulmonary bypass vasoactive/inotropic use where available. Results AKI was frequent after cardiovascular surgery and was independently associated with higher in-hospital mortality in adjusted analyses. Patients with AKI also had longer time to extubation, greater transfusion requirements, and prolonged ICU stay, with a stepwise worsening across KDIGO stages. Findings were consistent in sensitivity analyses. Incomplete urine-output data were acknowledged as a limitation, as oliguria forms part of KDIGO definitions. Conclusion Among cardiovascular surgery patients with prolonged ICU stay, postoperative AKI is a strong predictor of in-hospital mortality and adverse resource-related outcomes. Emphasis on prevention, early detection, and optimized perioperative management may improve prognosis in this high-risk population.