Mortality and costs associated with acute kidney injury following major elective, non-cardiac surgery

Objective: This study evaluated postoperative AKI severity and its relation to short- and long-term patient outcomes.Design: A retrospective, single-center cohort study of patients undergoing surgery from January 2015 to May 2020.Setting: An urban, academic medical center.Patients: Adult patients undergoing elective, non-cardiac surgery at our institution with a postoperative length of stay (LOS) of at least 24 h were included.Patients were included in 1-year mortality analysis if their procedure occurred prior to June 2019. Interventions: None. Measurements: Postoperative AKI was identified and staged using the Kidney Disease Improving Global Outcomes definitions. The outcomes analyzed were in-hospital mortality, LOS, total cost of the surgical hospitalization, and 1-year mortality.Main results: Of the 8887 patients studied, 648 (7.3%) had postoperative AKI. AKI was associated with severitydependent increases in all outcomes studied. Patients with AKI had rates of in-hospital mortality of 2.0%, 3.8%, and 12.5% for stage 1, 2, and 3 AKI compared to 0.3% for patients without AKI. Mean total costs of the surgical hospitalization were $23,896 (SD $23,736) for patients without AKI compared to $33,042 (SD $27,115), $39,133 (SD $34,006), and $73,216 ($82,290) for patients with stage 1, 2, and 3 AKI, respectively. In the 6729 patients who met inclusion for 1-year mortality analysis, AKI was also associated with 1-year mortality rates of 13.9%, 19.4%, and 22.7% compared to 5.2% for patients without AKI. In multivariate models, stage 1 AKI patients still had a higher probability of 1-year mortality (OR 1.9, 95% CI 1.3-2.6, p < 0.001) in addition to $4391 of additional costs when compared to patients without AKI (95% CI $2498-$6285, p < 0.001).Conclusions: All stages of postoperative AKI were associated with increased LOS, surgical hospitalization costs, inhospital mortality, and 1-year mortality. These findings suggest that patients with even a low-grade or stage 1 AKI are at higher risk for short- and long-term complications.