Artificial extracorporeal kidney

Artificial liver support systems aim at the extracorporeal removal of water soluble and protein-bound toxins (albumin being the preferential binding protein) associated with hepatic failure. Albumin contains reversible binding sites for substances such as fatty acids, hormones, enzymes, dyes, trace metals and drugs [26] and therefore helps elimination by kidneys of substances that are toxic in the unbound state. It should be noticed that the range of substances to be removed is broad and not completely identified. Clinical studies showed that the critical issue of the clinical syndrome in liver failure is the accumulation of toxins not cleared by the failing liver. Based on this hypothesis, the removal of lipophilic, albumin-bound substances, such as bilirubin, bile adds, metabolites of aromatic amino acids, medium-chain fatty acids, and cytokines, should be benefidal to the dinical course of a patient in liver failure. 

Several other reactors for immobilized heparinase have been designed (53,54). The initial reactor (47) caused no more blood damage than conventionally used extracorporeal devices such as the artificial kidney machine (54a). By controlling the mode of immobilized enzyme bead suspension, all blood damage can be essentially eliminated (54). The FDA... 

Extracorporeal medical machines (e.g., artificial kidney, pump-oxygenator) perfused with blood have been an effective part of the therapeutic armamentarium for many years. These devices all rely on systemic heparinization to provide blood compatibility. Despite continuous efforts to improve anticoagulation techniques, many patients still develop coagulation abnormalities with the use of these devices (1-3). Even longer perfusion times may occur with machines such as the membrane oxygenator. In such cases, the drawbacks of systemic heparinization are multiplied (4). A number of ap-... 

At present, synthetic blood filters are routinely placed at the effluent of extracorporeal devices such as the pump-oxygenator or artificial kidney to remove clots or aggregates formed during the perfusion. The filters used in oxygenators can be as large as 2 L, whereas those used in renal dialysis are only several milliliters. With further development, heparinase could be immobilized to polymers in these filters. In this case, the filter could remove both clots and heparin. 

Certainly with the modern emphasis on artificial body replacement parts and the success of implanted bits of hardware and assist devices for the heart (valves, heart bypass and pacemakers) and kidneys (renal dialysis), a substitute device for the natural lung should be considered. Artificial lungs are used daily for short-term (3- hours) heart-lung bypas in large, specialized health care centers. These are extracorporeal... 

Heparinase, an enzyme that degrades heparin into small polysaccharides, has also been immobilized into an extracorporeal device (artificial kidney bioreactor) to eliminate the anticoagulant properties of heparin (used to prevent clotting in the device) before the blood returns to the patient. ... 

Extracorporeal devices are mechanical organs that are used for blood purification they include the artificial kidney (dialyser), the artificial liver, and the mechanical lung. The function and performance of these devices both benefit from fibre and textile technology. Extracorporeal devices must possess certain requirements, such as bacterial resistance, and they must be anti-allergenic and non-toxic, have good breathability, and possess the ability to withstand sterilisation. Table 5.3 illustrates the function of each device and the materials used in their manufacture. 

With haemodialysis the blood passes an artificial kidney via extracorporeal circulation. The artificial kidney removes waste products and fluid. This happens mainly by osmosis (diffusion) via a semipermeable membrane, and partly by convection that is via the transport of water and waste products forced by pressure (idtrafiltration). 

Extracorporeal devices such as artificial kidney hver, lung, etc. 

Healthcare and hygiene textiles Extracorporeal devices Bedding, protective clothing, surgical gowns, clothes, wipes, etc. Artificial kidney, artificial liver, artificial lung, bioreactors, etc. 

Extracorporeal artificial organs provide mass-transfer operations to support failing or impaired organ systems [126]. Common examples include kidney substitute, hemodialysis, cardiopulmonary bypass (CPB), apheresis therapy, peritoneal dialysis, lung substitute and assist, and plasma separation. A critical component involved in the extracorporeal artificial organ is the membrane, which serves to separate the undesired substance from the blood or plasma. Ideally, materials used as the membrane in these particular applications should have appropriate cellular and molecular permeability, as well as blood compatibility (i.e., hemocompatibility). Over the years, both natural and synthetic polymers have been used as membrane materials. 

Capillary membranes (microporous hollow fibers) are an integral part of artificial lungs and kidneys. They represent extracorporeal applications where both the fibers and the textile structure are in direct contact with biood. For hemodialysis, mainly fibers made from cellulose, polysulfone, polymethylmethacrylate, and polyacrylonitrile are used. In oxygenators, mainly microporous hollow fibers made from polymethylpentene and silicone are used. Microporous hollow fibers can be... 

After haemodialysis, heat production showed a further increase (Table 29), presumably due to heparinization. Heparin is used as an anticoagulant to inhibit blood clotting during extracorporeal circulation of blood in the artificial kidney. Heparin is known to release enzymes, such as lipases and diamino oxidases, into the circulation. Thereby exothermic chemical reactions are expected to be induced in the plasma. On the other hand, oxygen consumption decreased significantly after haemodialysis, probably due to removal of oxygen-consuming substances. 

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