P95: Novel Outside-In Dialyzer Design Reduces Need for Anticoagulation

Hemodialysis (HD) requires extracorporeal anticoagulation to limit thrombosis formation leading to filter loss, therapy complexity, cost, and risk. We previously reported research on Standard Dialyzers (SD) vs novel Outside-In (OI) flow. In SD blood flows in the fiber Intra-Lumen (IL). Formation of a single thrombus will block the fiber. Thus, multiple thrombi cause loss of surface area, increased axial pressure, and eventual filter blockage. With OI blood flows outside the fiber and dialysate flows in the IL space. Although thrombi form at the same rate as in SD, they have a minimal effect on the blood flow, diffusive clearance, or filtrate flux in OI filters due to three-dimensional interconnected hydrodynamic flow channels. OI dialyzers require the blood contacting selective membrane layer on the outer fiber surface and a housing design minimizing shear/stagnation-induced blood deposition at the inlet and outlet of the fiber bundle. We report on the successful development of hollow fiber OI filters with polyethersulfone (PES) membrane with the hemocompatible selective membrane layer located on the outer fiber surface. These fibers have equivalent hemocompatibility, flux and clearance to current high flux PES fibers. New OI housing designs were optimized using computational fluid dynamics to solve geometry flow/shear problems, fiber bundle packing and porosity adjustments to obtain uniform velocity and shear rates. The new OI filters are designed to minimize blood clotting and need for anticoagulation by reducing blood shear stress and blood flow stagnation, forming uniform flow velocity fields.