Platelet deposition onto polymeric surfaces during shunting.

In an attempt to develop blood-contacting tubes that can be applied for short-term uses with a reduced heparin concentration or, ideally, without heparinization, we evaluated the blood compatibility of polymeric materials with a rabbit ex vivo shunt model. The shunt tubes employed were made of silicone, plasticized poly(vinyl chloride) (PVC), and segmented poly(ether urethane) (PU). In addition, two kinds of surface-modified tube were used: poly(vinyl alcohol) (PVA)-coated PVC and poly(dimethylacrylamide) (PDMAA)-grafted PU. The ex vivo shunt results correlated well with protein adsorption and platelet adhesion in vitro. The following order for the extent of platelet deposition was given, irrespective of the blood-contacting duration: PDMAA-grafted PU < PVA-coated PVC < PU < silicone, PVC. It is likely that many platelet aggregates detached from the PVA-coated PVC surface. For PDMAA-grafted PU, no trace of detachment of aggregates could be detected on any of the SEM photographs. The number and morphology of blood cells adhered onto the tube surfaces during ex vivo shunting were dependent on the kind of polymer surfaces, the blood exposure time, and the flow rate of blood.