Novel substitution technique in intermittent infusion hemodiafiltration (I-HDF) therapy using back filtration as substitution.

An infusion of dialysate into the blood compartment across the membrane using back filtration in dialysis therapy provides a stabilizing blood pressure and a membrane flushing during treatment. We devised a method to flush the membrane effectively and tried to find the optimum infusion patterns for intermittent infusion hemodiafiltration (I-HDF) from the aspect of solute removal by computing the pressure distribution in a diafilter. Bovine blood experiments were performed under following three modes: control HD in which no intentional filtration was involved, and two I-HDF in which back filtration was made either under counter current or under parallel flow. The inner surface of the hollow fiber before and after the experiment was observed using FE-SEM. According to the computation of the pressure distribution, a large amount of normal filtration occurs near the blood inlet in control HD. In addition, when the back filtration is performed under parallel flow, the amount of backfiltration near the blood inlet is 3.43 times higher than that in the case of counter current. Clearance (CL) of inulin remained at the highest level when the back filtration was performed under parallel flow. Near the blood inlet where the fouling was significantly formed, many macropores remained on the membrane when the backfiltration was performed under parallel flow. The degree of fouling showed a distribution along with the blood flow and the pressure distribution. Furthermore, the more effective recovery of CL can be expected by introducing the backfiltration under parallel flow to which fouling was significantly formed.