Hemodialyzer membrane materials

The flow behavior in miniaturized hemodialyzer modules with two types of biocompatible membrane materials, SMC and SPAN, was investigated by using doubly distilled water as the flowing fluid in both compartments, subsequently termed membrane side (M) and dialysate side (D), respectively (Figure 4.6.1 (c, d)) [12], SMC stands for Synthetically Modified Cellulose and SPAN for Special PolyAcryloNitrile-based copolymer (Akzo Nobel, Membrana GmbH), both types representing standard membrane material. The capillaries made from this hollow... 

Many membrane materials have been developed and are used for hemodialyzers. Today, these include regenerated cellulose, cellulose acetate, polyacrylonitrile, poly(methylmethacrylate), vinyl alcohol-ethylene copolymer, polysulfone, polyamide, and others. 

The relative magnitudes of the three terms on the right-hand side of Equation 15.25 vary with the diffusing substance, the flow conditions of both fluids, and especially with the membrane material and thickness. With the hollow-fiber-type hemodialyzers that are widely used today, membrane resistance usually takes a substantial fraction of the total resistance, and the fraction increases with increasing molecular weight of the diffusing component. 

One aspect of RRT that is overlooked by most clinicians is which hemodialyzer or hemofilter is used during the treatment. The material used to make the membranes of hemodialyzers (for hemodialysis) and hemofilters (for hemofiltration) varies by manufacturer, and recent evidence suggests that which membrane material is used may influence the outcomes of patients with ARF. When blood comes into contact with these membranes, the complement cascade is activated, resulting in an immune reaction. Each type of membrane induces complement to a different degree. Those that cause less of a complement cascade are termed biocompatible, while membranes that induce a large reaction are considered bioincompatible. Bio-... 

Topical microporous-membrane materials used in dialysis are hydrophilic, including cellulose, cellulose acetate, and various acid-resistant polyvinyl copolymers, typically less than 50 pm thick and with pore diameters of 15 to 100 A. Dialysis membranes can be thin because pressures on either side of the membrane are essentially equal. The most common membrane modules are plate-and-frame and hollow-fiber. Compact hollow-fiber hemodialyzers, which are widely used, typically contain several thousand 200-pm-diameter fibers with a wall thickness of 20-30 pm and a length of 10 to 30 cm (Seader and Henley, 2006). 

For example, Ronco [48] suggested the possibility of mixing the biomaterial of a specific membrane with a sorbent material based on a significant enhancement of internal and backfiltration in hollow-fiber hemodialyzers. Thus, the single membrane will have both characteristics, i.e., diffusion and adsorption for removal of uremic acid, and is called mixed matrix membrane (MMM) [49,50]. The MMM concept had been proposed earlier as an alternative to traditional chromatographic column [51]. 

---