Improved hemodialysis membranes for the artificial kidney

A major part of current effort in improving artificial hemodialysis techniques concerns the development of improved membrane structures. Although blood compatibility of membranes is a part of the Battelle program, this discussion is confined to membrane composition, structure, and transport. On the basis of a need for improved hemodialysis techniques, membranes for use in the artificial kidney were prepared and evaluated for urea, creatinine, and uric acid permeability. Water‐soluble polymers were crosslinked to form insoluble, but swellable, membranes. Faster metabolic waste transfer than with the conventional cellulosic membranes was obtained with diisocyanate‐crosslinked poly (vinyl pyrrolidone) and poly (vinyl pyrrolidone)–dextran membranes and with membranes obtained by crosslinking poly (vinyl alcohol) with polyfunctional aldehydes. Membranes prepared from emulsions of vinyl pyrrolidone–ethyl acrylate and vinyl pyrrolidone–styrene copolymers had exceptionally high urea and creatinine dialysis rates, but were deficient in uric acid transfer. This shortcoming was corrected by incorporating solutes such as sucrose into the membranes followed by leaching. Another important approach concerned the development of a relatively high‐strength membrane based on an impermeable nylon resin. Permeability of these membranes which have dialysis characteristics superior to those currently used was obtained through the addition of DMSO and one of several other additives to the coating solution.