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.