The antithrombotic effect of some EUROBIOMAT project test polymers in vivo.

The antithrombotic effect of six polymers was tested by weighing the amount of thrombus formed on polymer catheters of diameters 1.45-1.7 mm inserted in rat vein for one hour, and compared to that of platinum of diameter 0.5 mm. Ten observations were made of each polymer. The order of decreasing biocompatibility in microgram thrombus/sq mm surface was polyetheruethane (14.6), polypropolene (17.9), polyvinylchloride DEHP (23.5), polyethylene (27.3), polyvinylchloride TOTM (37.8) and polymethylsiloxane (39.1). Deposit on platinum was 200 micrograms/sq mm. These levels correspond to those attained by 150-333 iu heparin given intravenously, or warfarin from just inside the non-haemorrhagic (15% factor II) to the high-risk haemorrhagic range (8% factor II). Current polymer surface may exceed the antithrombotic biocompatibility afforded by drugs to platinum surface.