Types of Dialyzers

Based on the membrane design and configuration, there are three types of dialyzers available. The design of the membrane is crucial to determine the efficiency of the dialysis (how much and how sufficiently the blood can be filtered). The basic membrane designs for dialyzers are hollow fiber, parallel plate and coil dialyzers, and each one has its own disadvantages and advantages over the other, but all of them ultimately have the same function. 

The hollow-fiber dialyzer is the most effective design for providing low-volume, high efficiency devices with low resistance to flow. It is a composite of capillary, small, hollow 

dialysis tubing for laboratory applications comes in a variety of dimensions and molecular-weight cutoffs (MWCO). In addition to tubing, dialysis membranes are also found in a wide range of different preformatted devices that significantly improve the performance and ease of use of dialysis. The MWCO typically refers to the smallest average molecular mass of a standard molecule that will not effectively diffuse across the membrane upon extended dialysis. Thus, a dialysis membrane with a lOK 

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For some people, it s unbelievable and may sound like a surprise 900 different types of dialyzers are commercially available worldwide in 2014. They differ in geometric design, membrane polymer and surface area, capillary geometry and... 

Fig. 13.2 The standardly used artificial kidney is a dialyzer that contains more them 10,000 capillary membranes. Blood is guided through these hollow fibers whereas the dieilysis fluid is perfused in an opposite direction. Due to size, reproducibility and perfection of engineering features this type of dialyzer now dominates the dialysis market, mostly as a single-use device, since many years. The annual production capacity for hoUow fibers in 2013 made from different polymers is about 450,000,000 km. This figure is equivalent to three-times the distance between the Earth and the sun...

Historically, the development of animal cell culture systems has been dependent upon the development of new types of tissue culture media. Mouse L cells and HeLa cells were developed using a balanced salt solution supplemented with blood plasma, an embryonic tissue extract, and/or serum. In 1955 Eagle developed a nutritionally defined medium, containing all of the essential amino acids, vitamins, cofactors, carbohydrates, salts, and small amounts of dialyzed serum (Table 1). He demonstrated that this minimal essential medium (MEM) supported the long-term growth of mouse L and HeLa ceils. Eagle s MEM was so well defined that the omission of a single essential nutrient eventually resulted in the death of these animal cells in culture. 

In the past several clinical patterns have been described. The most important recognized clinical patterns or types of Al toxicity include two types of encephalopathy. Firstly, the classical dialysis dementia sometimes referred to as dialysis encephalopathy syndrome (DES) or dementia dialytica [24, 28, 37, 42, 70-74] and secondly, the acute or subacute Al encephalopathy [41]. There are also two types of bone disease - either osteomalacia with bone fractures and proximal myopathy or aplastic bone disease [41, 75, 76]. There is quite some confusion in the definitions of Al toxicity in the literature. Because there seems to be an obligatory lag phase of at least several days to weeks for symptoms to occur, acute Al encephalopathy, defined as a direct result of a single overdose, probably does not exist. Because of the long lag phase of several months to years necessary to develop the chronic dialysis encephalopathy and also because acute Al encephalopathy has an abrupt, sudden onset of symptoms one can understand why the term acute is used instead of the more descriptive subacute . The descriptions dialysis dementia [37, 42, 46, 73, 74] and dialysis encephalopathy [33-36, 38, 40, 41, 78] are also unfortunate because true dementia is rare in Al encephalopathy [73] and non-dialyzed patients can also develop these symptoms [78]. There are also many dialysis-related encephalopathy syndromes unrelated to Al. As an example,... 

Dialyzer reactions encompass a broad range of clinical symptoms that include anaphylactic (type A) and nonspecific (type B) events. In the past, these two types of reactions were considered to be part of the first-use syndrome because they occurred much more frequently when new, as opposed to reprocessed, dialyzers were used. Although reprocessing may reduce the incidence of type B events, it has little to no benefit for patients who experience a type A reaction. The... 

The sample must only be in a liquid or suspension in a homogeneous form before introduced into the dialyzer. Heavy solids are separated from the sample by centrifugation before introduction of the fluid into the dialyzer. The time required for the dialysis is about the same as the IC run time so the dialysis time can be overlapped with elution of the previous sample. This type of system lends itself to fully automated sample handling. 

Analytical and preparative separation of proteins soluble in an organic phase (n-propanol) has been carried out on a LiChrosorb-Diol column. This type of chromatography has been termed normal phase (R8). It has been applied to the analysis of proteins in dialyzed fetal calf serum (R8) and in the separation of protected hydrophobic oligopeptides (Nl), but as yet, it has not been used in a clinical chemical application. 

Dialysis membranes can be animal membranes and cellophane, but mostly used membranes are made of cellulose. Now, various-sized dialysis tubes, made by the American Union Carbide and American medical spectrum, are commonly used. The MWCO of the tubes are usually around 10,000. In order to improve the efficiency of dialysis, a variety of devices can also be used, including various types of Zeineh dialyzer (Biomed Instruments Inc. US), by which the speed and efficiency of dialysis can be greatly increased. 

A semipermeable membrane can be used to separate ions from colloidal particles because the ions can pass through the membrane but the colloidal particles cannot. This type of separation is known as dialysis and is used to purify blood in artificial kidney machines. Our kidneys normally remove waste products from blood. In a kidney machine, blood is circulated through a dialyzing tube immersed in a washing solution. The solution contains the same concentrations and kinds of ions as blood but no waste products. Dissolved wastes therefore dialyze out of the blood, but the large colloidal particles such as proteins do not. 

Usually, the dialysate flow rate in the artificial kidney is much larger than that of the blood flow rate. Regardless of the type of the dialyzer (cocurrent, countercurrent, or mixed flow), the extraction ratio E can be expressed as (Cooney, 1980) ... 

In a dialysis process, separation of the different solutes relies on the difference between the rates at which they are transferred across a semipermeable membrane located between the two liquid phases and across which mass transfer takes place. The type of the membrane is the key difference between gas-diffusion and dialysis units both use identical modules. Dialyzers are normally placed in the transport-reaction zone, and they are also occasionally positioned in the loop of the injection valve for... 

Many components in medical devices are made of rubber and rubber blends, consisting of latex, polyisoprene, silicone rubber, fluoroelastomers, ethylene propylene, etc. Some examples of conunercial products refer to seals for medical appliances, O-rings for dialyzers, medical pump seals, intravenous components, feeding devices, etc [http //www.applerubber.com/products/medical-seals.cfm]. However, if the concerned product interacts with tissues or biological fluids, it must fulfill some requirements referring to the biocompatibility, temperature resistance, chemical stability, mechanical properties, and electrical properties. Silicone rubber assures aU of these demands, being the most encountered type of rubber used in the fabrication of medical device parts. It is commonly used for the fabrication of different tubes and catheters because of its hemocompatibility and inert character. 

The preparation of silica gel plates for the cultivation of certain types of bacteria has been described by Muller and Holm (391). A silicic acid sol is made by adding a solution of sodium silicate to hydrochloric acid buffered at about pH 4.5. The gel is permitted to set in Petri dishes, washed, soaked in nutrient solution, and then autoclaved. For a purer medium, the intermediate sol may be dialyzed before it is permitted to set to gel (392). An improved procedure for incorporating nutrients directly into the acid, forming the gel under sterile conditions and eliminating dialysis, was developed by Sterges (393). A simplified method (394) is described as follows. Seven hundred milliliters of 0.5 N HCl is mixed with 300 ml of the mineral nutrient solution to be employed. To I volume of 0.5 N sodium silicate is added 1 volume of lime water, and to this 1 volume of the acid nutrient is added. The mixture is poured into Petri dishes, aged 2 hr, and placed in an oven at lOO C for 1 hr. The use of tetramethyl ester of orthosilicic acid is advocated by Ingelman and co-... 

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