ISSN:0022-233X    

DOI:10.1080/00222337008074358

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Intervention during circulatory insufficiency invariably produces certain basic changes in the blood itself and, as a consequence, in the functional aspects of blood-tissue exchange. Several categories of disturbances can be recognized: 1) Changes in the fluidity of the blood as a consequence of activation of blood coagulation mechanisms; 2) alterations in the physical properties of the red blood cells leading to abnormally high shear forces at the blood stream-vessel wall interface and to hemolysis; 3) inability of artificial systems to maintain integrity of vascular endothelium, and the blood capillary barrier in particular; 4) red blood cell aggregation and changes in the rheological properties of the blood.

ISSN:0022-233X    

DOI:10.1080/00222337008074359

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The past has seen the evolution of hemodialysis from a very complex operation to a systematized approach which allows the procedure to be instituted by minimally trained individuals. The first big advance in the application of hemodialysis to the problem of chronic renal insufficiency came in 1960 when a permanently implanted arteriovenous plastic fistulae was established. Improvements in dialyzer design and the logistics of hemodialysis since then have resulted in expansion of hemodialysis facilities. There is still a deficit between facilities available and suitable patients in need of therapy. Closure of this gap will depend upon a cheap, small, disposable dialyzer which most patients can operate themselves. In addition, an improvement in kidney transplantation results will remove many patients from the pool of those needing hemodialysis. It is likely that other medical applications of hemodialysis will be discovered in the future.

ISSN:0022-233X    

DOI:10.1080/00222337008074360

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The medical grade silicones are probably the most widely used of all the synthetic polymers for permanently implanted subdermal devices. This paper reviews the chemistry of these materials from the original polymer manufacturing through the various stages necessary to obtain the types of heat vulcanizing silicone rubber, room temperature vulcanizing silicone rubber, and silicone rubber adhesive most commonly used in medical applications.

ISSN:0022-233X    

DOI:10.1080/00222337008074361

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

A knowledge of the structure of the double layer is essential in the investigation of reactions at an inierface between two dissimilar media. This aspect is briefly presented in respect to charge separation and potential distribution in the interfacial region. The types of reactions that can occur at solid-solution interfaces (electron transfer, electrosorption, and electro-phoretic deposition) are discussed. The electrokinetic methods for determination of surface charge characteristics of insulator materials in electrodes are reviewed. Thrombosis on the blood vessel wall and on prosthetic materials is an interfacial chemical reaction. The evidence for an electrochemical mechanism of thrombosis on conducting materials is outlined. Under normal conditions, the blood vessel wall is negatively charged. Injury or atherosclerosis makes it less negatively or even positively charged. With decrease of pH, there is an increase in the surface charge density of the blood vessel wall with an isoelectric point at a pH of about 4.5. Materials treated chemically so as to introduce negatively charged groups (sulfonate, carboxylate, heparinized, anionic ioplex) tend to be antithrombogenic while positively charged surfaces (cationic Ioplex, quarternary ammonium group) are thrombogenic. A useful criterion for antithrombogenic polymer materials is that their surfaces must have a uniform negative charge.

ISSN:0022-233X    

DOI:10.1080/00222337008074362

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The use of persistent electrical polarization in polymers has been explored as a means of reducing surface thrombogenicity. Parallel efforts have been carried out on the characterization of surface properties related to the electret state in polymers, on the stability of the electret state in desirable prosthetic materials under simulated blood pumping conditions, and on in vitro and in vivo blood compatibility experiments. Preliminary correlations among critical surface tension, electrical polarization, and blood compatibility have been obtained. In vitro blood compatibility has been explored using both a modified Lee-White clotting test and a platelet adsorption experiment. No significant difference in clotting time was found for polarized samples; however, those with a negative charge did adsorb fewer platelets. A series of in vivo studies has been carried out using electrified right atrial flags (36) of poly-vinylidene chloride and vena cava rings (22) of FEP Teflon, Hypalon rubber, and Hypalon/2% polysulfonate. Negatively polarized samples showed improved blood compatibility in all cases. About 2/3 of the negatively charged atrial flags showed little or no thrombus and the remainder moderate thrombus whereas 2/3 of the positively charged flags showed severe thrombus. About 3/4 of the negative ring implants showed little or no thrombus. A correlation with anomalous contact angle or low charge was found in 4 of 6 cases of the rings with moderate to heavy thrombus.

ISSN:0022-233X    

DOI:10.1080/00222337008074363

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

A series of epoxy resins has been formulated on the basis of obtaining low water sorption, low water vapor permeability, retention of electrical properties, and resistance to biodegradation by the body. These resins have been tested for these properties both by accelerated aging in 100°C water and in vivo studies.

ISSN:0022-233X    

DOI:10.1080/00222337008074364

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

There are three types of foreign body reactions to plastic implants: 1) reactions due to physical characteristics of the implant, 2) reactions due directly to chemical properties of the implant, and 3) immune reactions. Responses which vary with the physical properties of the implant are epithelial encapsulation of the plastic, epithelial keratinization in cutaneous implants, thickening of the connective tissue fibrous capsule, formation of ground substance, and the presence of giant cells. Responses related directly to chemical toxicity of the plastic are epithelial hypertrophy (with mild irritants), inhibition of epithelial growth (with more toxic irritants), connective tissue inflammation, accumulation of a cellular glycoproteins, and vacuolization of host tissue. Finally, reactions due to infection or the presence of other antigens are characterized by inhibition of epithelial growth, invasion of epithelium by leukocytes, and proliferation of inflammatory tissue with a large population of plasma and other round cells.

ISSN:0022-233X    

DOI:10.1080/00222337008074365

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

A rapid in vitro screening protocol to guide selection and monitoring of polymers for implant or extracorporeal applications is described. There are four main procedures under the protocol: 1) and 2) measurement of physical property change over thermal and simulated biochemical stress, 3) infrared spectrophotometric assay of migratible species developed over simulated biochemical stress, and 4) cell culture sensitivity to those migratible species. In vivo biochemical stress was simulated and accelerated by exposing polymer specimens to a pseudoextracellular fluid (PECF) at 120°C for 62 hr.

ISSN:0022-233X    

DOI:10.1080/00222337008074366

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Asymmetric membranes of cellulose acetate and cellulose acetate modified with pendant amino groups have been evaluated for ultrafiltration and dialysis properties. Ultrafiltration rates from 4 to 30 times that of Cuprophan were obtained. During the ultrafiltration test, up to 89% of inulin in the test solution permeated with the ultrafitrate in contrast to the 14% permeation of inulin through a Cuprophan membrane. In spite of the apparently facile permeation of high molecular weight species (e.g., inulin) through the experimental membranes, human albumin was quantitatively reflected. Dialysis tests indicate that cellulose acetate membranes 38 μ or less in thickness should surpass 23-μ-thick (wet) Cuprophan in purely diffusional transport of blood solutes of low molecular weight.

ISSN:0022-233X    

DOI:10.1080/00222337008074367

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor