Plasma clots formed in the presence of erythrocytes have pores large enough to allow significant perfusion induced washout of red cells. Erythrocyte washout is a function of gel pore size and erythrocyte flexibility. This study evaluated the possibility of increasing cell washout by enhancing gel pore size and/or erythrocyte flexibility. Addition of increasing concentrations of Dextran 40 resulted in gels composed of large fibers with large intervening pores. Gel fiber mass-to-length ratios increased from 2.6 to 8.1 x 10(13) Da/cm as Dextran 40 concentration increased from 0 to 12 mg/ml. Over the same dextran concentration range, perfusion measurements revealed an increase in gel pore diameter from 1.4 to 3.5 x 10(-4) cm and an increase in erythrocyte washout from 8.2 to 30.4% during a 1.5 gel volume exchange. Pentoxifylline was added to blood to enhance erythrocyte flexibility. Whereas turbidity measurements indicated minimal direct impact of pentoxifylline (50 micrograms/ml) on fibrin assembly or structure, perfusion measurements indicated an increase in erythrocyte washout from 8.1 to 13.4% after a 1.5 gel volume exchange. Efforts to evaluate pentoxifylline effects at higher concentrations were hampered by decreased adhesion of the gel to the sides of the perfusion chamber. These results indicate that it may be possible to enhance erythrocyte washout and thereby increase diffusion and perfusion of materials through in situ clots.
Blood Coagulation Dextrans