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

Abstract

Adsorption 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 We used discarded plasma exchanges from uremic patients and out-of-date erythrocytes as a novel in vitro uremic precursor matrix to assess removal and adsorption patterns of distinct material and structure but similar surface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.

Combining Diffusion, Convection and Absorption: A Pilot Study of Polymethylmethacrylate versus Polysulfone Membranes in the Removal of P-Cresyl Sulfate by Postdilution On-Line Hemodiafiltration

“…Several studies have previously demonstrated the efficient removal of other PBUTs such as furancarboxylic acid and pentosidine [46,47], as well as inflammatory markers such as TNF-α, IL-1β, IL-6, and C-reactive protein, by other PMMA dialyzers [48]. The high protein adsorption capacity of these membranes is due to their symmetrical pore structure which provides a large specific surface area [28,49]. Whereas in PMMA membranes the whole membrane thickness is involved in the separation process allowing toxin adsorption, in PS membranes (with asymmetrical pores) only a fine layer of ≈1 µm is responsible for the separation process, while the remaining membrane thickness has structural functions only [20].…”

“…Technical characteristics of the dialyzers. Adapted from Cavalier, 2017; Masakane, 2017; and Gómez, 2020[25,27,28].…”

Distinct Solute Removal Patterns by Similar Surface High-Flux Membranes in Haemodiafiltration: The Adsorption Point of View

“…Once the patient was disconnected, an elution protocol presented elsewhere [18] was implemented. The obtained eluate ( V eluate ∼ 160–250 mL) was collected into 50 mL propylene tubes and stored at −80°C until processing.…”

On the total albumin losses during haemocatharsis

“…Results of such experimental studies have been reported using modules after in vitro tests (e.g. [ 22 ]); however, very few test results are available with “fouled” HC filters after a session (e.g. [ 23 ]), as outlined below.…”