RESUMEN
A stable heparinized surface was prepared by sequential treatment of polyethylene with water solutions of hexadecylamine hydrochloride, heparin and glutardialdehyde. In order to explain the "non-thrombogenic" properties of this surface, it was evaluated with regard to prevention of platelet adhesion and aggregation. Human heparinized blood (2 and 10 IU/ml) with 51Cr-labelled autologous platelets was rotated for 60 minutes in untreated and heparin-treated circular tubings. The surface area/blood volume ratio was varied and an air-blood interface was present. In untreated tubings, platelet adhesion and aggregation increased in proportion to the size of the surface area/blood volume ratio, irrespective of the heparin concentrations of the blood. In the heparin-treated tubings, there was no measurable platelet adhesion to the surface and no platelet aggregation in the blood. The difference between the heparinized and the untreated surfaces with regard to platelet adhesion was discernible even after 10 minutes storage of stagnant blood. It is concluded that platelet adhesion and aggregation induced by exposure of blood to a foreign surface in an in vitro experimental model can be prevented by a stable heparin coating of the surface.
Asunto(s)
Heparina/farmacología , Adhesividad Plaquetaria , Agregación Plaquetaria , Aldehídos , Humanos , Propiedades de Superficie , Factores de TiempoRESUMEN
Heparin can be bound to polymer surfaces by precipitation of an ionic heparin-amine complex which can be stabilized against dissolution by treatment with glutardialdehyde. The aim of this investigation was to study the degree and course of desorption of heparin from such a heparinized surface on contact with blood. This desorption must be considered when analysing the interaction between the heparinized surface and blood. Different heparinized surfaces were prepared by using 35S-labelled heparin, and the desorption of heparin on exposure in vitro to citrated plasma or heparinized blood as well as during exposure at in vivo conditions was quantified. During in vitro experiments, the glutardialdehyde stabilized surface became stable with no further desorption of heparin after an initial loss of about 3% of the initial surface-bound heparin. Under in vivo conditions, there was an initial loss of about 12%. There was no further loss from surfaces inserted into the circulation of the dog for seven days as compared to those inserted for one hour.
Asunto(s)
Sangre , Heparina/farmacología , Polímeros , Adsorción , Humanos , Propiedades de Superficie , Factores de TiempoRESUMEN
Threshold curves with large and small surface intracardiac pacemaker electrodes are compared. The 2 msec. impulse threshold with a 47 sq. mm. electrode was 3.6 v. (4.3 mA.) on the fourteenth postoperative day, when it reached its maximum, and 2.8 v. (3.1 mA.) one month after the operation. These values were 45 and 30 per cent lower with a 6 sq. mm. electrode. Thresholds increased by about 20 per cent when the impulse duration was shortened from 2 to 0.5 msec. The small surface electrode consumed about 35 per cent less current than the 47 sq. mm. one. A newly designed large area-small surface electrode with the shape of an open cage, seems to have the advantages of less increase in postoperative thresholds and good attachment to the endocardial wall.