Advances in blood component separation and plasma treatment for therapeutics
The separation of blood cells from plasma is done routinely by centrifugal techniques.
Membranes for plasma separation.
Membrane modules vary in surface area from about 0,15 to 0,8 m2. Membrane plasma separation is a relatively simple process. At relatively low transmembrane pressure (generally less than 50 mm Hg), adequate plasma fluxes can be achieved. Equipment requirements are only minimal and the operation is much akin to that for other extracorporeal treatment technologies as hemodialysis, hemofiltration and hemoperfusion.
Membrane of on-line plasma treatment.
Plasma exchange whether by centrifugal or membrane techniques requires that the plasma discarded be replaced by physiological solution, which in most cases is en albumin solution. Because essential plasma components as well as pathological ones, are removed during plasma exchange, techniques designed to remove only the pathological components would be highly desirable. Review of the disease states treated by plasma exchange reveals that mane of the marker solutes ere off molecular weight larger (generally greater than 100 000 daltons) than albumin, suggesting membrane filtration as physical separation techniques for their removal.
With presently available membranes, selective passage of albumin (near 70 000 daltons) and lower molecular weight solutes with complete retention of larger molecular weight solutes is difficult to achieve. However, such a complete separation may not be desirable since many higher molecular weight solutes are normal components of plasma To apply some selectivity in the separation of the marker solutes with a high return to the normal constituents of plasma and thus no requirement for plasma product infusion, the technique of cryofiltration was applied.
Cryofiltration is the on-line technique of plasma treatment consisting of plasma cooling followed by membrane filtration. By cooling the plasma, cryogel is deposited on the membrane during the Filtration process. The cryogel has been shown to contain concentrated quantities of the marker solutes. Response to therapy in the majority of patients with rheumatoid arthritis has been from good to excellent. In treatments, decreases in marker solutes have been noted coupled with improvement in clinical symptomology.
Membrane technology appears very promising in the separation and treatment of plasma on-line. Chronic treatment therapies appear safe and well tolerated by the patients.
New words
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centrifugal technique – центрифужные технологии
plasma exchange – плазмообмен
therapeutic – терапевтический
metabolic – метаболический
multiple – множественный
extracorporeal – экстракорпоральный
Artificial oxygen carries
Artificial oxygen (O2) carries aim at improving O2delivery Artificial O2carries thus may be used as alternative to allogeneic blood transfusions or to improve tissue oxygenation and function of organs with marginal O2supply. Artificial O2carries can be grouped into modified hemoglobin (Hb) solutions and perfluorocarbon (PFC) emulsions. The native human Hg molecule needs to be modified in order to decrease O2affinity and to prevent rapid dissociation of the native tetramer into dimers. The O2transport characteristics of modified Hb solutions and PFC emulsions are fundamentally different. The Hb solutions exhibit a sigmoidal O2dissociation curve similar to blood. In contrast, the PFC emulsions are characterised by a linear relationship between O2partial pressure and O2content. Hb solutions thus provide O2transport and unloading capacity similar to blood. This means that already at a relatively low arterial O2partial pressure substantial amounts of O2are being transported. In contrast, relatively high arterial O2partial pressures are necessary to maximize the O2transport capacity of PFC emulsions. Modified Hb solutions are very promising in improving O2transport and tissure oxygenation to a physiologically relevant degree. Because cross-matching is unnecessary, these solutions hold great promise as alternative to allogeneic blood transfusions and as O2therapeutics, which might be of great value also in the prehospital resuscitation of trauma victims or in specific situations in intensive care medicine. In patients with a reduced cardiac contractility and normal or elevated mean arterial pressure Hb infusion may increase systemic and pulmonary vascular resistances with consequent reduction in, cardiac output. In contrast, in a previously healthy trauma victim, suffering from severe hypovolaemia due to massive haemorrhage, the combined effects of volume replacement, added O2transport capacity, and mild vasoconstriction due to the infusion of a modified Hb solution may be beneficial.
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PFC are carbonfluorine compounds characterised by a high gas-dissolving capacity, low viscosity, and chemical and biological inertness. Manufacturing an emulsion with very specific characteristics is a great technologic challenge. After intravenous application, the droplets of the emulsion are being taken up by the reticular-endothelial system, droplets are slowly broken down, the PFC molecules are being taken up in the blood again and transported to the lungs, where the unaltered PFC molecules are finally excreted via exhalation. The ability of PFC emulsions to transport and efficiently unload O2is undisputed. With the application of perflubron emulsion, cardiac output tender to increase.
New words
saturation – насыщение гемоглобина кислородом
emulsion – эмульсия
oxygen – кислород
solution – раствор
O2transport – транспорт кислорода
tissure oxygenation – оксигенация тканей
physiological – физиологический
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