Cardiac surgery-associated acute kidney injury in a single healthcare system: a retrospective observational study

OBJECTIVE: To assess the incidence of cardiac surgery-associated acute kidney injury and to evaluate secondary outcomes, including 30-day mortality, prolonged mechanical ventilation, kidney replacement therapy, renal recovery, and length-of-stay metrics. METHODS: This retrospective observational study analyzed routinely recorded data from a single multi-hospital healthcare system, including all adult cardiac surgery intensive care unit patients between July 1st, 2021, and June 30, 2022. Cardiac surgery-associated acute kidney injury was stratified according to the KDIGO guidelines using serum creatinine. Urine output criteria were incorporated when available. RESULTS: Cardiac surgery-associated acute kidney injury of any stage occurred in 16.7% of patients (stage 1 - 13.6%, stage 2 - 1.8%, and stage 3 - 1.3%). Thirty-day mortality had wide confidence intervals, with odds ratios of 20.8 (95%CI 3.8 - 114) and 93.6 (95%CI 23.4 - 375) for acute kidney injury stages 2 and 3, respectively, compared with stage 0. A total of 27.5% (52/189) of patients with cardiac surgery-associated acute kidney injury did not meet the strict definition of renal recovery at discharge. Median intensive care unit length of stay, average time on mechanical, and time to discharge were significantly longer in patients with cardiac surgery-associated acute kidney injury (p < 0.001). CONCLUSION: Cardiac surgery-associated acute kidney injury is a common postoperative complication associated with substantially increased mortality, prolonged ventilation, longer length of stay, and reduced renal recovery. These findings underscore the clinical importance of early identification, risk stratification, and perioperative management strategies to mitigate harm from acute kidney injury.