Progress and Problems in Blood-Compatible Polymers

Abstract

Compatibility with blood means, in broadest terms, no adverse effect on blood or any of its components. The complex nature of blood with its formed elements, coagulation system, and multitude of proteins puts not only a variety of restrictions, largely undefined, on the blood-contacting surface, but also makes the determination of blood compatibility an added significant problem. Further complicating the matter is the reverse requirement—no adverse effects by the blood on the polymer. Of the possible adverse effects of a foreign surface on blood, thrombogenesis—promotion of clotting—being most obvious and of immediate consequence, has received, the most attention. Fortunately, this very serious and disabling aspect of incompatibility can be overcome sufficiently by the administration of systemic anticoagulants such as heparin or coumadin to permit the use of the lifesaving devices such as heart-lung and kidney machines and artificial heart valves. Early postulates as to factors increasing thromboresistance included increased hydrophobicity, increased negative surface charge, and increased surface smoothness. The first real indication that thromboresistance was within grasp was the finding by a group at the University of Wisconsin (1) that heparin, ionically bonded to a surface, did provide a very significant degree of thromboresistance.