On the Blood Compatibility of a Heparin-Polyvinyl Alcohol Hydrogel

Abstract

Heparin immobilized onto polyvinyl alcohol (PVA) by action of glutaraldehyde has been shown to be biologically active in a novel parallel flow arteriovenous shunt in dogs. The heparin-PVA hydrogel was applied as a coating to chromic acid etched polyethylene tubing. A pair of Y-connectors was used to divert < 2% of the flow in the AV shunt through the heparinized tube which remained patent for longer than two hours while a control tube without heparin was occluded within 30 minutes at a main shunt flow rate of 150 ml/min. This enhanced patency was achieved without significant release from the surface, consistent with earlier experiments attributing the thromboresistance of the heparin-PVA hydrogel to the formation of a surface bound inactive thrombin-anti- thrombin III complex. In vitro test systems used to assess the platelet reactivity of immobilized heparin have not revealed any effect in contrast to ex vivo studies where platelet adhesion and aggregation was significantly reduced by immobilized heparin. These demonstrate the utility of heparin PVA hydrogel for preparing materials with potential long term thromboresistance and for testing validity of the hypothesied limitations to the long term use of immobilized heparin.