Blood response

Journal of Materials Science. Materials in Medicine 14, No.10, Oct.2003, p.905-12 BLOOD RESPONSE TO PLASTICIZED POLYVINYL CHLORIDE. DEPENDENCE OF FIBRINOGEN ADSORPTION ON PLASTICIZER SELECTION AND SURFACE PLASTICIZER LEVEL... 

A study has been carried out on the interactions of blood with plasticised poly(vinyl chloride) biomaterials in a tubular form. The influence of different factors such as the biomaterial, antithrombotic agent, blood condition and the nature of the application is represented when considering the blood response in the clinical utilisation of the plasticised PVC. The PVC was plasticised with di-(2-ethylhexyl)phthalate (DEHP) and tri-(2-ethylhexyl)trimellitate (TEHTM)and in-vitro and ex-vivo procedures used to study the biomaterial with respect to the selection of the plasticiser. The blood response was measured in terms of the measurement of fibrinogen adsorption capacity, thrombin-antithrombin III complex and the complement component C3a. X-ray photoelectron spectroscopy was used for surface characterisation of the polymers and the data obtained indicated that in comparison with DEHP-PVC, there is a higher reactivity... 

The two-lump model was scaled using machine unit scaling and programmed on the hybrid computer. The most significant advantage of the tissue lump-capillary lump model over a single lump model is the possibility of observing tissue response characteristics separate from the blood response. 

The tissue lump-capillary lump approximation allows the tissue lump response to be investigated separately from the blood response. The... 

Blood responses. Blood is the fluid which transports body nutrients and waste products to and from the extravscular tissue and organs, and as such is a vital and special body tissue. The major response of blood to any foreign surface (which includes most extravascular surfaces of the body s own tissues) is first to deposit a layer of proteins and then, within seconds to minutes, a thrombus composed of blood cells and fibrin (a fibrous protein). The character of the thrombus will depend on the rate and pattern of blood flow in the vicinity. Thus, the design of the biomaterial system is particularly important for cardiovascular implants and devices. The thrombus may break off and flow downstream as an embolus and this can be a very dangerous event. In some cases the biomaterial interface may eventually "heal" and become covered with a "passive" layer of protein and/or cells. Growth of a continuous monolayer of endothelial cells onto this interface is the one most desirable end-point for a biomaterial in contact with blood. Figure 10 summarizes possible blood responses to polymeric biomaterials. 

Test techniques for both tissue and blood responses of bio-materials have evolved significantly over the past several years. Increased government regulation of biomaterials in medical devices (as legislated in the U.S.A. in 1976 by the Medical Devices Amendments Act) has stimulated the development of a number of common vitro and vivo animal test systems for screening a wide variety of biomaterials and devices or implants for both tissue and blood responses. Tissue tests encompass a variety of in vitro and in vivo techniques. Blood tests include in vitro, ex vivo, and in vivo techniques. It is unlikely that successful medical devices or implants can be perfected for human use without such preliminary vitro and (especially) animal tests. 

Figure 10. Blood responses to foreign materials depend on the material as well as its design and the character of the blood flow near the biomaterial surface.

Platelet One of the formed elements of blood responsible for blood coagulation. 

F. In vivo blood responses (animal model technique)... 

Correlation of Physical Surface Properties with Blood Responses... 

This is still a very confused field. An excellent introduction to the questions of tissue and blood response to implanted polymers has been written by Bagnall together with a lead to key references in this field. Review papers by Bruck dealing with the interaction of both natural and synthetic surfaces with blood. 

Table 2. Selected methods for evaluating blood response of exposure to...

Figure 2 indicates the unequivocal rise in blood catecholamines obtained in normal subjects within the very first minutes after intravenous glucagon injection. This effect is very transitory. In fact, table I shows that, 5 and 15 min after the glucagon injection, there is no detectable change in the catecholamines blood level in the normal subjects as well as in the hypertensive patients. On the contrary, in the two cases of pheochromocytoma, a rise in blood adrenaline and noradrenaline has been obtained. The values reached in case I.F. are particularely high in this particular case, the catecholamines blood response is completely normalized six weeks after the removal of the tumor. 

Their evidence for the importance of fraction C was based on the following results. The continuous administration, over a ten day pmod, of primary factor, as fraction E, together with fraction A but with minimal amounts of fraction C (fraction E contained sufficient fraction F), induced only slight reticulocyte and erythrocyte responses. An increase in the amount of fraction C, however, was followed by a satisfactory blood response as seen in Fig. 2. 

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