Potential of dual-skinned, high-flux membranes to reduce backtransport in hemodialysis

Background Potential backfiltration of cytokine-inducing material is a clin ical concern during hemodialysis conducted with high-flux membranes, Novel hollow-fiber membranes were developed that had asymmetric convective solute transport properties, aimed at reducing the passage of potentially harmful molecules from dialysate to blued, while maintaining the desired fluid and solute movement from blood to dialysate. Methods. Sieving coefficient as a function of molecular weight was measured in vitro using polydisperse dextrans. Measurements were conducted using tw o different Rat-sheet membranes in series or using hollow fiber membranes h aving two integrally formed skin layers. Based on measured experimental par ameters, model calculations simulated the performance of a clinical-scale d ialyzer containing these new membranes versus that of a commercially availa ble high Aux dialyzer. Results. Asymmetric convective solute transport was demonstrated using both commercial Rat-sheet and newly developed hollow-fiber membranes. For two f lat-sheet membranes in series, the extent of asymmetric transport was depen dent on the order in which the solution was filtered through the membranes. For the hollow-fiber membranes, the nominal molecular weight cut-off was 2 0 kD in the blood-to-dialysate direction and 13 kD in the dialysate-to-bloo d direction. For this membrane, model calculations predict that clearance o f a beta(2)-microglobulin-sized molecule (11,800 D) would be significantly greater from blood to dialysate than in the reverse direction. even under c onditions of zero net ultrafiltration. Conclusion. A novel hollow-fiber dialysis membrane was developed that allow s greater convective solute transport from blood to dialysate than from dia lysate to blood.