MEMBRANES FOR DIALYSIS

Today, more than 30 different polymers or polymer blends are used as m aterials for dialysis membranes. They can be categorized following the scheme of a family tree of haemodialysis membranes. The trunk represe nts membranes from regenerated cellulose, major branches show either s ynthetically modified cellulose membranes or membranes manufactured fr om synthetic polymers. As the latter are standardly hydrophobic, small branches elucidate the technique on how these materials have been ren dered partially or completely hydrophilic. Complications may arise, wh en comparing membranes only following their polymer names, such as pol ysulfone, polyacrylonitrile or polyamide. Due to varying polymer compo sitions, membranes with the same polymer names may differ in their hae mocompatibility, flux properties and adsorption characteristics. Adsor ption of proteins like beta(2)-microglobulin, fibrinogen and coagulati on factors, complement proteins, or hormones like parathormon and eryt hropoietin are differently adsorbed by dialysis membranes and thus ads orption contributes to the removal characteristics. Of central interes t for membrane development and application is the question of how thes e membranes can be sterilized, as a series of patient adverse reaction s has been attributed to the dialyser sterilization procedures. Apart from the cellulosic membranes Cuprophan and Hemophan, the majority of membranes cannot be sterilized by steam, as these materials degrade wh en exposed to above their class-point temperature. Finally, future asp ects of modern membrane development should not neglect the needs of pa tient populations with specific blood properties, such as diabetics.