Prevention of platelet adhesion to porous surfaces.

Porous samples of cellulose diacetate/nitrate CAN (millipore filter), polycarbonate PC (nuclepore filter), cellulose diacetate Ca, and polydimethyl siloxane SR of various pore sizes were immersed in stirred heparinized human blood while being perfused with lactated Ringer's solution at various rates. Control samples were exposed to the blood in the absence of perfusion. The control tests showed that CAN and PC adhered platelets rapidly to plateau levels of 1--5 X 10(6)/cm2 in approximately 4 min, while CA and SR remained platelet-free. The critical perfusion rate vp* to prevent adhesion of platelets (and all formed elements) to the CAN and PC was approximately 0.1 cc/min cm2 at a shear rate of approximately 620 sec-1 independent of pore size tested. vp* increased slightly with stirring rate. A simplified diffusion-convection model was used to qualitatively account for the effects observed.