Impact of Acute Kidney Injury on Hospitalization Outcomes in Patients with Chronic Kidney Disease Undergoing Cardiac Procedures with Cardiopulmonary Bypass in the United States.

BACKGROUND: Acute kidney injury (AKI) is a common complication after cardiac surgery and is associated with more infections, prolonged recovery, longer hospital stays, increased readmission rates, greater costs, and higher mortality. Patients with pre-existing chronic kidney disease (CKD) are at particularly high risk, with this risk increasing as renal function worsens. Damage caused by AKI may be irreversible, despite a return to baseline GFR, compounding stress on remaining nephrons. Understanding risk in these populations may ultimately help to improve prevention and outcomes. OBJECTIVE: Evaluate the impact of AKI on outcomes and healthcare costs among adults with CKD undergoing cardiac surgery with cardiopulmonary bypass (CPB). METHODS: Multi-institutional, retrospective, observational study using the Healthcare Cost and Utilization Project Nationwide Readmissions Database, 2016-2020 datasets. The total adult cardiac surgery population were those with CKD who underwent cardiac surgery requiring CPB (reporting incidence); from which a subpopulation of adults with severe CKD (stage 3 or 4; based on ICD-10-CM codes during index hospitalization) was assessed (impact of AKI). Patients were categorized as follows, based on AKI status during index hospitalization: no AKI, AKI, or AKI requiring dialysis (a subpopulation of AKI). RESULTS: AKI incidence during initial hospitalization was 55.9% and 77.3% in patients with CKD stage 3 and 4, respectively. AKI requiring dialysis occurred in 3.4% and 14.5% of CKD 3 and 4 patients, respectively. One-third of all AKI cases and half of AKI requiring dialysis cases occurred in patients with CKD stage 3 or 4. In patients with CKD stage 3 or 4, multivariate analysis showed AKI was associated with increased inpatient days, increased risk of 180-day readmission, higher hospitalization costs, and greater odds of in-hospital mortality. Patients experienced the greatest burden when AKI required dialysis. CONCLUSIONS: Incidence of AKI is higher in patients with preexisting CKD stage 3 or 4 vs 1 or 2 and those without CKD. The burden of AKI is elevated in patients with CKD undergoing cardiac surgery with CPB; targeted interventions are needed to prevent poor outcomes.