BIOMATERIALS FOR ROTARY BLOOD PUMPS

Rotary blood pumps are used for cardiac assist and cardiopulmonary sup port since mechanical blood damage is less than with conventional roll er pumps. The high shear rate in the rotary pump and the reduced antic oagulation of the patient during prolonged pumping enforces high deman ds on the biocompatibility of the materials in the pump in order to pr event thrombus formation. Materials with a very hydrophobic character appear to adsorb much thrombin and induce a conformational change of f ibrinogen, resulting in a surface with a high affinity for platelet in teraction. Furthermore, heigh shear forces of 120 dyne-s-cm(2) in rota ry pumps induce platelet release and platelet aggregation. Thus, hydro phobic materials and high shear rates should be prevented to avoid thr ombus formation in rotary blood pumps.