A canine ex vivo series shunt for evaluating thrombus deposition on polymer surfaces

A new acute canine ex vivo femoral A-V series shunt experiment is described. Platelet and fibrinogen deposition on a series of up to ten different polymers may be tested in the same nonanticoagulated animal. The method reduces the time and expense associated with animal testing, and also allows for the simultaneous monitoring of platelet and fibrinogen deposition on a number of polymer surfaces. The series shunt technique was used to examine platelet and fibrinogen deposition on polyethylene, Silastic, polyvinylchloride, and oxidized polyethylene surfaces. Following an initial period of minimal deposition, platelet deposition increased dramatically to a peak by about 15-20 min of blood contact on all surfaces studied. The amount of adsorbed fibrinogen fell from initial levels to a minimum at about 5-10 min of blood contact and then increased to a peak at about the same time as observed for the platelet response. Oxidized polyethylene was the most thrombogenic surface studied, followed by polyethylene, polyvinylchloride, and Silastic. Peak platelet and fibrinogen levels were found to be inversely related to flow rate over the range studied. In this experiment it appears that the interaction of blood components with a foreign surface in vivo or ex vivo is localized to the interface with the flowing blood. Within experimental errors, no effect of segment position or any downstream effects were observed. These results suggest that a series shunt may be used to investigate the short-term interactions of blood with a number of test surfaces.