Importance of membrane materials for blood purification devices in critical care.

Choosing dialyzers is more important in blood purification in critical care because therapeutic conditions (especially the amount of dialysate) are usually limited. Then, adsorption is the third major mechanism of removing toxic substances from patients in these treatments. Several commercial dialyzers designed for acute blood purification therapy were investigated by performing aqueous ultrafiltration experiments to demonstrate the importance of the membrane materials. Polymethylmethacrylate (PMMA) showed strong adsorptive characteristics to alpha-chymotripsinogen A (MW 25,000) but showed much less adsorptive characteristics to cytochrome C (MW 12,400). On the contrary, polyacrylonitrile (PAN) showed relatively lower affinity and polysulfone (PS) showed essentially no affinity to these proteins. Time and concentration dependent characteristics of clearance for these solutes were also demonstrated in PMMA. These facts were also verified in other dialyzers with another PMMA and polyester polymer alloy (PEPA) designed for chronic hemodialysis, which concluded that adsorption found in PMMA may be due to the occlusion of protein molecules into pores of the membrane. Choosing membrane materials is, therefore, important not only in removing inflammatory cytokines but also considering the loss of albumin in acute and chronic treatments.