RESUMEN
A new method has been developed to evaluate the relative thrombogenicity of vascular catheters. The technique provides a means to quantitatively differentiate between catheters made from different polymeric materials. Autologous In-111 labeled platelets were infused into a dog model and catheters were then inserted into the external jugular vein of the dog. The neck region was scanned using gamma camera imaging. Comparisons between catheter materials were made using computer generated uptake slopes during the first 40 min of the scan. In addition to scintigraphy, visual assessment of thrombus deposition, thrombus weight, platelet deposition, and scanning electron microscopy were used to validate the technique. Poly(vinyl chloride), polyurethane, heparinized polyurethane, and silicone catheter materials were tested. It was found that heparinized polyurethane was the least thrombogenic of all materials evaluated.
Asunto(s)
Cateterismo/instrumentación , Trombosis/etiología , Animales , Materiales Biocompatibles , Plaquetas , Cateterismo/efectos adversos , Perros , Indio , Microscopía Electrónica de Rastreo , Agregación Plaquetaria , Cloruro de Polivinilo , Radioisótopos , Cintigrafía , Siliconas , Trombosis/diagnóstico por imagen , Trombosis/patologíaRESUMEN
In the last decade a number of chemically fixed, soft tissue based bioprostheses have become commercially available. Chemical fixation of these materials changes a number of their physical and chemical properties. Quantitation of these effects has been difficult because of: anisotropy of the biopolymers, variable composition of the materials, and sample size and configuration limitations. Collagen tape, made from reconstituted collagen, has been chosen as a model material because it alleviates many of the aforementioned problems. Its constituent fibers are homogeneous and unidirectional. The cross-sectional area is constant. Thus, the resultant uniaxial tensile stress-strain relationship is reproducible to allow for systematic parametric studies. Results are presented for the change in tensile properties of the collagen tape as a function of exposure time to glutaraldehyde fixative. These properties are described by the equation: sigma = A (eB epsilon-1) The tensile properties of fresh and fixed pericardial tissue were also tested and corroborative results were found.
Asunto(s)
Bioprótesis , Colágeno/fisiología , Modelos Biológicos , Animales , Bovinos , Tejido Conectivo/fisiología , Estudios de Evaluación como Asunto , Microscopía Electrónica de Rastreo , Conformación Molecular , Resistencia a la TracciónRESUMEN
Activated carbon is a high surface area adsorbent. Its ability to adsorb nitrogenous metabolic wastes and exogenous poisons from blood has been well documented. Polymeric coatings on activated carbon enhance its biotolerability and make it feasible for use in hemoperfusion devices. The only drawback seems to be the presence of microparticles on the carbon surface. These particles may become emboli during hemoperfusion. This paper describes a series of in vitro tests used to evaluate many commercially available granular and pelletized activated carbons. The tests were as follows: 1) creatinine adsorption capacity and kinetics, 2) initial cleanliness, 3) washability, 4) attrition resistance, and 5) carbon particle surface morphologymone grade of activated carbon has been chosen for hemoperfusion studies on the basis of the above evaluations; The nature of the microparticles and the approach used to remove them from this carbon is described.
