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PubMed2004

Artificial in vivo biofiltration: slow continuous intravenous plasmafiltration (SCIP) and artificial organ support.

An intravenous plasmafiltration (SCIP) catheter has been developed and is proposed for clinical investigation into the alleviation of acute fluid overload by SCUF of the extracted plasma. The system utilizes a unique backflushing technique, high intravenous shear flow rates and biocompatible polymers to minimize protein and platelet aggregation along the filter surfaces. The absence of platelets from the extracted plasma promotes the longevity of ultrafiltration cartridges, thus theoretically minimizing attendant labor associated with continuous renal replacement therapies. Clinical studies are currently being planned for the near future. Plasma SCUF is envisioned as a predecessor technology to future applications in therapeutic apheresis, tissue engineering, therapeutic sorbent technologies. Further, with improved longevity profiles, intravenous SCUF or dialysis and implantable or wearable artificial organs based upon artificial in vivo biofiltration are possible.

Artificial Organs↗
PubMed1987

Biocompatibility of artificial organs: an overview.

Papers that are presented in this symposium on biocompatibility of foreign surfaces used in artificial organs are commented upon and set in an overall context of the biocompatibility of foreign surfaces to blood. A working formulation of the events comprising lack of biocompatibility of hemodialysis membranes to the complement system is given as a possible model to which other foreign surfaces may be compared.

Animals↗
PubMedDate not supplied

Current concepts of thrombosis and infection in artificial organs.

Significant progress is being made on many fronts in the understanding and prevention of thrombosis and infections with artificial organs. It is likely that these advances will enable both implanted and temporary prosthetic cardiovascular devices to occupy an increasing role in clinical medicine in the future.

Animals↗
PubMed2000

Mechanical degradation of polyacrylamide solutions as a model for flow induced blood damage in artificial organs.

Human or animal blood is normally used as a test fluid for the in vitro evaluation of hemolysis by artificial organs. However, blood has some disadvantages (large biological variability and problems with cleaning the devices). For that reason, we searched for a reproducible technical fluid with blood-like flow characteristics that exhibits similar shear depending destruction. In this study, a direct comparison between erythrocyte damage of bovine blood and shear-induced degradation of polyacrylamide solution is given. A uniform shear field was applied to the fluids using a shear device with a plate-plate geometry. It was shown that similarities exist between erythrocytes disaggregation and breakdown of super molecular structures in polymer solutions, caused by mechanical stress. In both cases steady low shear viscositity was diminished and the elastic component of complex viscosity of blood and polymer solutions has been reduced. There is a correlation between shear-induced hemolysis of bovine blood and mechanical polymer-degradation, which depends on the applied shear stresses.

Acrylic Resins↗
PubMedDate not supplied

The biocompatibility of artificial organs.

Thromboembolic events in very short-term ventricular assistance have been uncommon. However, patients who are bridged or have long-term artificial heart implantations have almost uniformly experienced serious thromboembolic sequelae. Anticoagulation regimens for this form of circulatory assistance have varied but results are inconclusive. Intravenous heparin is commonly used, while low molecular weight Dextran, aspirin, and other antithrombotic agents are occasionally used. Mechanical cardiac valve failures requiring reoperation are due primarily to thrombosis, tissue overgrowth, and structural failure. Reoperations of tissue valves indicate sterile degeneration, usually related to calcification and tears, as the principal cause of failure. Despite improvements in biomaterials and an appreciation of the influence of disordered flow on graft patency, antithrombotic therapy represents the most clinically relevant approach to prevention of occlusion of vascular prostheses. The location of neointimal hyperplasia in vascular prostheses is different from that in vein grafts, the effect concentrating at the anastomosis. No clear rationale exists for antithrombotic therapy for hyperplasia in this instance. However, a rationale does exist for early antithrombotic therapy to reduce surface thrombogenicity. The lessons learned from clinical trials of antithrombotic therapy in the case of vein grafts might be profitably studied with regard to synthetic grafts and other artificial organs. Early low-dose aspirin and, possibly, dextran-40 treatment are justified in this case. However, continuation of these therapies past the early healing phase does not appear warranted. Clinical and experimental studies with hemodialysis and other membranes suggest complement activation through the alternate pathway is commonly observed; the biologic responses are consistent with the known properties of C5a. Factors governing anaphylatoxin exposure can be ascribed to the nucleophilicity and number of surface reactive groups. Elimination of surface reactive groups, or binding of bystander plasma proteins such as albumin, may be expected to limit complement activation.

Artificial Organs↗
PubMed2000

Gel-impregnated pore membranes with mesh-size asymmetry for biohybrid artificial organs.

Membranes based on mechanically supported poly(vinyl alcohol) (PVA) hydrogels with mesh-size asymmetry were developed for potential application in biohybrid artificial organs. The pores of cellulose ester microfiltration membranes were impregnated with a PVA solution, which was lightly crosslinked with glutaraldehyde and then modified under a glutaraldehyde gradient to produce mesh-size asymmetry. Permeation experiments were performed with the resulting homogeneous and asymmetric gel-impregnated pore membranes (GIPMs). Creatinine (MW: 113), goat Fab (MW: 50 kD) and human IgG (MW: 150 kD) were used to simulate the molecular size of nutrients, therapeutic proteins, and immunological molecules, respectively. The transport properties of the GIPMs were compared to those of conventional ultrafiltration (UF) and dialysis membranes. Experimental results indicate that GIPMs with mesh-size asymmetry have thickness-normalized creatinine permeabilities that are slightly higher than those in cellulosic UF membranes but as much as 100% greater than those in polysulfone UF or cellulosic dialysis membranes. IgG permeabilities in the GIPMs are from 5 to 50 times lower than those in the UF membranes. Fab permeabilities are 6 to 40 times higher in the UF membranes than those in the GIPMs, but the required permeability for a therapeutic protein is application specific. GIPMs may also be suitable as an alternative for hemodialysis.

Animals↗
PubMedDate not supplied

[Artificial organs].

Explore the source record for details and available documents.

Artificial Organs↗
PubMed1996

Membranes in artificial organs.

Membrane processes by a pivotal and enabling role in modern replacement therapy for acute and chronic organ failure and in the management of immunologic diseases. In fact, virtually all contemporary extra-corporeal blood purification methods employ membrane devices, and the next generation of artificial organs and tissue engineering therapies are almost certain to be similarly grounded in membrane technology. In this short essay, we comment on the similarities and differences among synthetic membranes and their natural counterparts and also provide a critical overview of the demographics and technology of hemodialysis, hemofiltration, apheresis, oxygenation, and emerging membrane technologies and applications.

Artificial Organs↗
PubMedDate not supplied

The possibility of improving biocompatibility by removing anaphylatoxins from the circuit of blood-perfused artificial organs.

The possibility of reducing bioreactivity during extracorporeal circulation by removing bioactive substances "turned on" in the devices is described in this paper. The bioreaction and bioactive products, as represented by neutrophil reaction and activated complement fragments generated during the use of a blood-perfused artificial organ, were studied as a model. Hemoperfusion with activated charcoal (AC) was used to remove the activated complement fragments. The adsorption of anaphylatoxins (C3a, C4a, and C5a) was evaluated following plasma perfusion through AC in vitro, all three of which were satisfactorily adsorbed. Six kinds of AC (three HEMA coated AC, two uncoated AC, and one cellulose coated AC) were compared with respect to adsorption of C5a in vitro. Uncoated AC adsorbed well and rapidly, but the coating with HEMA made adsorption take place slowly. The cellulose coating activated complement and did not decrease plasma C5a levels. After the adsorption of anaphylatoxins was confirmed, each of the AC columns was placed on-line after a cuprophan dialyzer in five chronic hemodialysis patients. C3a levels and neutrophil counts were compared with those obtained during usual hemodialysis (HD). By using heparin treated, uncoated AC, elevation of C3a levels and transient neutropenia were suppressed. Peak C3a with AC was reduced by 150% compared with prevalues, and the neutropenia nadir increased from 20% to 40% of baseline. The adsorption ability influenced the reduction in neutropenia. The heparinized uncoated AC and the column with large volumes of HEMA-coated AC had the best effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaphylatoxins↗