Time-Dependent Decline in Extraction Ratios for LDL Cholesterol and Fibrinogen During a Single Rheocarna Treatment Session

Abstract

Lipoprotein apheresis is an adjunctive treatment for severe peripheral artery disease (PAD) and is a Category II indication for peripheral vascular diseases in the American Society for Apheresis guidelines. Rheocarna, a direct hemoperfusion adsorption device used in Japan for severe PAD and chronic limb-threatening ischemia (CLTI), is designed to remove LDL cholesterol (LDL-C) and fibrinogen (Fib). Device performance is often summarized by pre−/post-treatment values or a single-point extraction ratio (ER), which may not capture time-dependent changes in adsorption efficiency. We therefore characterized serial ER profiles during Rheocarna treatment in maintenance hemodialysis patients with severe CLTI (5 patients, 10 sessions) and in a closed-loop ex vivo system using pooled plasma. Inlet and outlet samples were obtained serially, and ER was calculated as (C_in − C_out)/C_in × 100. In clinical sessions, median LDL-C ER declined from 73.7% (IQR 70.9–76.2) at baseline to 12.3% (10.3–14.6) at 60 min and 5.2% (3.1–8.2) at 120 min (p < 0.0001). Fib ER similarly declined from 63.3% (59.9–69.9) at baseline to 7.9% (6.2–10.1) at 60 min and 6.5% (5.1–7.5) at 120 min (p < 0.0001). In the ex vivo system, LDL-C ER also decreased over time (p = 0.0274), whereas Fib ER showed a more variable pattern (p = 0.1877). These findings show that extraction efficiency changes substantially during a treatment session and may not be fully captured by a single-point ER. Serial ER profiling may provide a more detailed assessment of the time-dependent performance of adsorption-based apheresis devices.