A New Approach for the Filtrate Regeneration System in the Wearable Artificial Kidney

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Abstract
In the filtrate and/or dialysate regeneration system, which is expected to miniaturize the artificial kidney, ammonium decomposed from urea by immobilized urease is removed competitively by ion‐exchangers from coexisting cations. Since divalent cations such as Ca2+ and Mg2+ are more favorably exchanged than ammonium ion, this system needs supplementation of these cations and, thus, additional amount of ion‐exchanger. To minimize these requirements, we utilized positively charged membrane to process cation‐free filtrate in which urea is dialyzed. Positively charged membranes were tested in vitro to evaluate separation efficiency between urea and cations. Equilibrium adsorption of ammonium ion to ion‐exchanger with or without co‐existing cations demonstrates that this filtrate regeneration system can reduce the amount of ion‐exchanger up to one‐half to one‐third of that of the conventional system. In an ex vivo experiment with a mongrel dog, blood urea nitrogen (BUN) concentration was maintained at the same level or up to 23% less than the initial value.