Evolution of hemodialysis membranes

Adsorption of the uremic toxin p-cresol onto hemodialysis membranes and microporous adsorbent zeolite silicalite

Para-cresol CH3C6H4OH is a protein-bound solute which is not eliminated efficiently by hemodialysis systems. In this study, we present adsorption of p-cresol as a complementary process to hemodialysis. The kinetics and isotherms of adsorption onto cellulose-based membranes (cellulose diacetate and triacetate), synthetic membranes (polyamide, polysulfone, polyacrylonitrile and polymethylmethacrylate) and microporous zeolite silicalite (MFI), have been evaluated in static conditions. The results indicate that p-cresol has a low affinity to all membranes but polysulfone and polyamide and that the times to reach equilibrium conditions are slow. In contrast, equilibration time on silicalite is fast (2 min to eliminate 90%) while adsorption levels are high (maximum adsorption about 106 mg g(-1)). Adsorption onto microporous adsorbents could be a novel way to eliminate uremic toxins from blood.

Properties of membranes used for hemodialysis therapy

Recent trends show a progressive increase in the use of modified cellulosic and synthetic dialyzers and a corresponding decrease in the utilization rate of unmodified cellulosic dialyzers. The purpose of this article is to describe current membrane and dialyzer technology, with the focus almost entirely on modified cellulosic and synthetic membranes. A general overview of membrane-related determinants of dialyzer performance is first presented, followed by a discussion of specific characteristics of some of the more commonly used membranes and dialyzers.

Quo vadis dialysis membrane?

The development of dialysis membranes is closely related to the development of dialysis as a routine therapy for patients with kidney failure. Without having membranes and dialyzers available as commodity products, the treatment of more than 1 million uremic patients worldwide would be impossible. Several transition periods can be identified: a change in membrane geometry from flat sheet to capillaries, a shift in market appreciation from cellulose to synthetic polymers, and from low-flux to high-flux dialyzers. This shift is supported by the notion that convective therapies using high-flux membranes allow the removal of large-molecular-weight solutes. From a historical background, three eras of perception can be identified for both membrane and dialysis development. First, the period of survival when nephrologists had to focus on techniques for blood access and availability of membranes. Second, the period of issues dedicated to rather specific features of membranes and dialysis therapy such as dose of dialysis, reuse, sterilization, and membrane biocompatibility. And third, the period of quality tops this sequence with a complicated approach: the principal area of interest from the medical community has switched to issues such as quality of life, morbidity, mortality, therapy standards, and cost-effectiveness. New membrane developments should focus on this situation.