Dialysis, disadvantages

Electrodialysis. In reverse osmosis pressure achieves the mass transfer. In electro dialysis (qv), dc is appHed to a series of alternating cationic and anionic membranes. Anions pass through the anion-permeable membranes but are prevented from migrating by the cationic permeable membranes. Only ionic species are separated by this method, whereas reverse osmosis can deal with nonionic species. The advantages and disadvantages of reverse osmosis are shared by electro dialysis. 

It is obvious from Equation (6) that the processes are accompanied by sodium chloride produdion. The salt content reaches a significant amount that sometimes poses a problem. The NaCl is withdrawn by dialysis that makes the silica fabrication inconvenient owing to this additional time consuming procedure. As a further disadvantage of sodium metasilicate, it is believed to be not very flexible in regulation of the silica morphology [61]. 

Renal replacement therapy (RRT), such as hemodialysis and peritoneal dialysis, maintains fluid and electrolyte balance while removing waste products. See Table 75-4 for indications for RRT in ARF. Intermittent and continuous options have different advantages (and disadvantages) but, after correcting for severity of illness, have similar outcomes. Consequently, hybrid approaches (e.g., sustained low-efficiency dialysis and extended daily dialysis) are being developed to provide the advantages of both. 

Intermittent RRT (e.g., hemodialysis) has the advantage of widespread availability and the convenience of lasting only 3 to 4 hours. Disadvantages include difficult venous dialysis access in hypotensive patients and hypotension due to rapid removal of large amounts of fluid. 

Instead of dialysis, small molecules, such as salts or organochemi-cal substances, can be separated quickly from macromolecules by gel filtration. Buffer exchange is also possible this way. The disadvantage is a dilution of the sample. 

Scale-up of cell cultures makes use of suspension cultures (erythropoietic cells or microcarriers) or, less often use of capillary beds (hollow fibre systems or glass bead columns), but these suffer from the same disadvantages seen with smaller scale cultures ( 3.4.4). In particular, nutrients are depleted as the medium flows through long columns or beds and high rates of flow coupled with recirculation are often employed. Nevertheless, Organon have used a hollow fibre dialysis system for production of monoclonal antibodies (Schonherr et al., 1985). Invitron s hollow fibre system has been used to produce cell conditioned media and the Cell-Pharm System (Jencons Ltd. Appendix 3) will produce up to 20 g cell secreted product per month. 

Lysis of the periplasmic space can alternatively be performed with BBS buffer (0.2 M sodium borate, pH 8.0, 0.16 M sodium chloride). This can lead to a lower yield and has the further disadvantage that dialysis may become necessary to eliminate the buffer. With BBS buffer proceed as follows ... 

Ultrafiltration or gel filtration can be used instead of dialysis to de-salt solutions, or change buffer conditions. These techniques have the advantage of increased speed, but the disadvantage of being less straightforward and needing more complex equipment. 

The most commonly used methods to determine drug binding to plasma proteins are equilibrium dialysis, ultrafiltration, and microdialysis. All have advantages and disadvantages, and results are method- and condition-specific. 

For on-line measurements, the dialysis step is very important because, through dialysis, the solid particles can be retained, the solution can be purified, and also some of the interference can be eliminated. The main disadvantages of dialysis are the slow speed involved... 

The main disadvantage with PD is the risk of infection causing peritonitis. Incidence rates of peritonitis have decreased over the years and the current standard from the United Kingdom Rena Association is that the peritonitis rate should be less than 1 episode per 18 patient months. The immediate effect of peritonitis is to reduce UF, and repeated episodes can cause scarring and fibrosis with permanent loss of filtration. Icodextrin, a nonglucose polymer, may have some value in improving UF in patients with loss of peritoneal fimction. However, loss of UF in the setting of loss of RRF usually requires transfer of dialysis modality to HD. 

Two major disadvantages of dialysis and chromatographic methods, as well as ISE and ASV, are adsorption of interacting species and disturbing of complexation equilibria. Further, ISE and ASV are applicable adequately only to a limited typology of metal ions (e.g., Cu " ", Cd " ", Pb " ", and Zn-+). An important advantage of UF methods is that they do not take as much experimental time as does dialysis, and do not disturb the complexation equilibria. 

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