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.