Membrane for hemodialysis

Radiation Induced Reactions. Graft polymers have been prepared from poly(vinyl alcohol) by the irradiation of the polymer-monomer system and some other methods. The grafted side chains reported include acrylamide, acrylic acid, acrylonitrile, ethyl acrylate, ethylene, ethyl methacrylate, methyl methacrylate, styrene, vinyl acetate, vinyl chloride, vinyl pyridine and vinyl pyrrolidone (13). Poly(vinyl alcohols) with grafted methyl methacrylate and sometimes methyl acrylate have been studied as membranes for hemodialysis (14). Graft polymers consisting of 50% poly(vinyl alcohol), 25% poly(vinyl acetate) and 25% grafted ethylene oxide units can be used to prepare capsule cases for drugs which do not require any additional plasticizers (15). 

T. Kobayashi, M. Todoki, M. Fujii, T. Takeyama and H. Tanzawa, Permeability and structure of PMMA stereocomplex hollow fiber membrane for hemodialysis, in E. Drioli and M. Nakagaki (Eds.), Proc. Eur.-fpn Cong. Membr. Membr. Processes, Plenum, New York, NY, 1986, pp. 507-513. 

As of 1995, more than 30 different polymer blends were being used in the manufacture of membranes for hemodialysis and hemofiltration (Klinkmann and Vienken, 1995). The various membrane types used for renal replacement therapy can be divided into membranes derived from cellulose (83 percent of 1991 worldwide total) and from synthetic materials (the remaining 17 percent) (Klinkmann and Vienken, 1995). Synthetic membranes have been constructed from such materials as polyacrylonitrile (PAN), polysulfone, polyamide, polymethylmethacrylate, polycarbonate, and ethyl-vinylalchohol copolymer (Klinkmann and Vienken, 1995). In the United States, use of cellulosic materials for membrane construction predominates at around 95 percent of the total number of membranes used (Klinkmann and Vienken, 1995). 

Suitability of a Membrane for Hemodialysis. Experiments are being conducted... 

The hydrophilization of poly(ether sulfone) surfaces used for the production of ultrafiltration membranes for hemodialysis is of special interest Poly(ether sulfone) is a chemically inert and highly thermostable polymer showing a hydrophobic surface which leads to high fibrinogen adsorption and subsequent thromboembolization [111]. This effect is generally avoided by non-desirable heparin doses. The hydrophilization of poly(ether sulfone) surfaces by plasma-induced graftcopolymerization and the introduction of a hydrogel layer without... 

B. Su, S. Sun, C. Zhao, Polyethersulfone hollow fiber membranes for hemodialysis, in A. Carpi, C. Donadio, G. Tramonti, eds.. Progress in Hemodialysis - From Emergent Biotechnology to Clinical Practice, INTEC, Chap. 4, ISBN 978-953-307-377-4, 2011. 

Henne, W., Pohle, R., Lawitzki, F. Dialysis membrane for hemodialysis. German Patent... 

SiroUi, V, Di Stante, S., Stuard, S., Di Liberate, L., Amoroso, L., CappeUi, R, Bonomini, M. BiocompatibiLity and functional performance of a polyethylene glycol acid-grafted cel-lulosic membrane for hemodialysis. Int. J. Artif. Organs 23(6), 356-364 (2000)... 

Physical or physico-chemical capability (Table 1), including mechanical strength, permeation, or sieving characteristics, is another important requirement of biomaterials. Cuprammonium rayon, for instance, maintains its dominant position as the most popular material for hemodialysis (artificial kidney). Thanks to its good mechanical strength, cuprarayon can be fabricated into much thinner membranes than synthetic polymer membranes as a consequence, much better clearance of low-molecular-weight solutes is achieved. 

Many classification schemes for hemodialysis membranes exist. Water permeability through the porous membranes is frequently used.14 Water permeability for a dialyzer is defined by the ultrafiltration coefficient for the particular device (KUF, mL/ h/mmHg). The KUF of any individual fiber will be related to the pore size and has an... 

These membranes are used for the ultrafiltration of biological liquids (blood and urine), for hemodialysis in an artificial kidneys and for hemooxygenation in an artifidal lung The extraordinarily hi water permeability allows us to use the polyionic complexes as the additives to usual film-forming resins for preparing materials with a high coefficient of permeability to water vapor ... 

Figure 12 shows a possible set-up for hemodialysis monitoring. Patients blood is pumped through a dialysis cell, and low molecular weight substances including urea are removed by a semipermeable membrane (cut off 10 kD) and dialysis buffer. The urea enriched dialysate passes through an injection valve and enters a waste container. Due to switching the valve, a defined sample volume is pumped to the ET. Here, enzymatic conversion takes place via immobilized urease and provides information about the current urea concentration. Thus, the hemodialysis effect is automatically monitored via urea analysis and makes an individual treatment possible. 

Figure 1 Relative permeability spectra for synthetic and natural membranes. Curves (1) and (2) represent the glomerular membrane for neutral and anionic solutes, respectively (8), curve (3) hemofiltration membranes (.91, and curve (4) hemodialysis membranes (10), Reproduced with permission from Ref. 52. Copyright 1980 Kidney International.

The processes used to prepare cellulosic membranes generally lead to homogenous cross-sectional structures. Cellulose prepared from xanthate derivatives may exhibit a cuticle or skin structure however, this asymmetry does not produce significant resistance to mass transfer. Most membranes currently used for hemodialysis are prepared via the cuprammonlum process. These membranes do not form a skinned structure during coagulatlon/regeneratlon. 

Blends of isotactic and atactic polymethylmethacrylate (PMMA) in solution have been used to form semipermeable membranes, for both hemodialysis and hemofiltration. Details of the polymer properties are not available (18). 

Polyethylene-co-vlnylaloohol/polyethylene-co-vinylacetate (PVA) polymers have been fabricated into membranes for both hemodialysis and microfiltration. The fabrication procedure and physical properties of the finished membrane material have not been published. Both the PMMA and PVA membranes have been developed in Japan, where most of the application studies have been performed. 

Copper sulfate causes ulceration of the oral and esophageal mucosa, and an acute dose of 7-8 g is usually fatal. Copper intoxication has occurred when copper salts were used to treat extensive skin bums or when copper-containing tubing or dialysis membranes were used for hemodialysis. Pulmonary fibrosis has been described in vineyard workers exposed for many years to fungicidal sprays (e.g., Bordeaux mixture ) containing copper sulfate. About 33-50 mg of copper per year ( 100 /rg/d) dissolves from copper-containing intrauterine contraceptive devices. Part of this copper is lost in menstrual flow, but part is rapidly absorbed. Whether this is harmful is not known but it seems unlikely. Penicillamine is the drug of choice for treatment of copper excess. 

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-... 

FIGURE 41.2 Basic principle of artificial cells Artificial cells are prepared to have some of the properties of biological cells. Like biological cells, artificial cells contain biologically active materials (I). The enclosed material (I) can be retained and separated from undesirable external materials, such as antibodies, leukocytes, and destructive substances. The large surface area and the ultra-thin membrane allow selected substrates (X) and products (Y) to permeate rapidly. Mass transfer across 100 mL of artificial cells can be 100 times higher than that for a standard hemodialysis machine. The synthetic membranes are usually made of ultrathin synthetic polymer membranes for this type of artificial cell. (From Chang, T.M.S., Artif. Cells Blood Substit. ImmobU. Biotechnol., 22(1), vii, 1994.)... 

Apart from these, CS membranes find applications in the field of hemodialysis. The excellent fitm-forming nature and high mechanical strength of CS membranes made it a suitable candidate for hemodialysis application. For example, chitosan-poly(ethylene oxide) blend membranes showed improved permeability and blood compatibility due to their hydrophilic and porous nature [28]. However, the cellulosic membranes and synthetic membranes (made up of polyaryle-thersulfone, polyamide, PVP, polycarbonate, and PAN) have a well-established hemodialysis field as compared to CS-based membranes. 

A very common commercial device for hemodialysis is the C-DAK 4000 artificial kidney of Althin CD Medical, Inc. (acquired by Baxter International, Inc. in March, 2000). This disposable, sterilized membrane module, shown in Figure 19.5, resembles a shell-and-tube heat exchanger. The tubes, which number 10,000, are hollow fibers, 200 microns i.d. by 10 microns wall thickness by 22 cm long, made of hydrophilic microporous cellulose acetate of 15 to 100 A pore diameter. Alternatively, fibers of polycarbonate, polysulfone, and other poly-... 

For hemodialysis membranes, biocompatibility is the primary requirement. It is known that surface properties such as surface roughness play important roles in determining membrane biocompatibihty. It has also been reported that for a given material, smoother surfaces are more biocompatible [64]. Hence, the sinfaces of three different commercial hollow fibers were studied by AFM to compare their roughness parameters. Figures 4.42 and 4.43 show AFM images of inner and outer surfaces, re-... 

Barzin et al. [34] characterized UF poly(ether sulfone) hemodialysis membranes (Chap. 5). The morphologies of both inner and outer surfaces changed on heating either in hot water or in air, and so did the performances of the membranes. The performance data of hollow fibers heated in air at 150 °C was foimd to be the most appropriate for hemodialysis application. 

Cellulose acetate is a modified cellulose that can be melt processed. Cellulose acetate membranes are used for hemodialysis. 

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