Assessment of removal and adsorption enhancement of high-flux hemodialyzers in convective therapies by a novel in vitro uremic matrix

Abstract

AbstractAdsorption properties of hemodialyzers are traditionally retrieved from diffusive treatments and mainly focused on inflammatory markers and plasma proteins. The possible depurative enhancement of middle and high molecular weight solutes, as well as protein-bound uremic toxins by adsorption in convective treatments, is not yet reported. We used discarded plasma exchanges from uremic patients and out-of-date erythrocytes as a novel in vitro uremic precursor matrix to assess removal and adsorption patterns of distinct material and structure but similar surface hemodialyzers in hemodialysis and on-line hemodiafiltration treatments. We further related the obtained results to the possible underlying membrane pore blocking mechanisms. Convection improved removal but slightly enhanced adsorption in the cellulosic and synthetic dialyzers tested. The polymethylmethacrylate hemodialyzer obtained the highest extracted ($$M_{ext}$$ M ext ) and adsorbed ($$M_{ads}$$ M ads ) mass values when submitted to hemodiafiltration for all molecules analyzed including albumin ($$M_{ext}=15.8\pm 3.9$$ M ext = 15.8 ± 3.9  g, $$M_{ads}=44.3\pm 11.5$$ M ads = 44.3 ± 11.5  mg), whereas the polyamide membrane obtained substantial lower results even for this molecule ($$M_{ext}=2.2\pm 1.2$$ M ext = 2.2 ± 1.2  g, $$M_{ads}=4.2\pm 0.7$$ M ads = 4.2 ± 0.7  mg) under the same treatment parameters. Hemodiafiltration in symmetric and enlarged pore hemodialyzers enhances removal and adsorption by internal pore deposition (intermediate pore-blocking) for middle and high molecular weight toxins but leads to substantial and deleterious albumin depuration.