Clinical and Economic Burden of Acute Kidney Injury Following Cardiac Surgery: A National Analysis of U.S. Hospitalizations

Background: Acute kidney injury (AKI) is a common complication following cardiac surgery and is associated with increased morbidity and mortality. Contemporary national estimates of its clinical and economic burden in the United States remain limited. Methods: We conducted a retrospective cross-sectional study using the Nationwide Inpatient Sample (NIS) for 2022–2023. Adult hospitalizations undergoing coronary artery bypass grafting (CABG), valve surgery, or combined CABG and valve surgery were identified using ICD-10-PCS codes. Hospitalizations with end-stage kidney disease were excluded. The primary exposure was AKI. Outcomes included in-hospital mortality, length of stay (LOS), non-home discharge, and hospitalization cost. Survey-weighted multivariable regression models were used to evaluate the independent association between AKI and study outcomes. Results: The final cohort included 133,801 hospitalizations, representing an estimated 669,005 cardiac surgery hospitalizations nationally. AKI occurred in 123,240 weighted hospitalizations (18.4%). Compared with hospitalizations without AKI, those with AKI had higher unadjusted mortality (7.21% vs. 0.71%), longer LOS (14.4 vs. 6.3 days), greater rates of non-home discharge (68.1% vs. 41.2%), and higher hospitalization costs ($97,452 vs. $56,253). After adjustment for demographic, socioeconomic, clinical, and procedural characteristics, AKI remained independently associated with in-hospital mortality (adjusted odds ratio [aOR] 9.91, 95% confidence interval [CI] 8.95–11.00), non-home discharge (aOR 2.52, 95% CI 2.42–2.63), prolonged LOS (adjusted rate ratio [aRR] 1.88, 95% CI 1.85–1.91), and increased hospitalization costs (cost ratio 1.59, 95% CI 1.56–1.61). AKI was associated with an adjusted incremental cost of $33,497 per hospitalization, corresponding to an estimated national attributable cost burden of $4.13 billion during the study period. Conclusions: AKI complicates nearly one in five cardiac surgery hospitalizations in the United States and is associated with substantially increased mortality, healthcare utilization, and hospitalization costs. These findings highlight the significant clinical and economic burden of cardiac surgery–associated AKI and support continued efforts to improve prevention, risk stratification, and perioperative management.