Platelet retention in columns packed with glass beads.

Abstract

Platelet retention in columns packed with glass beads has been theoretically analyzed in a manner similar to that commonly used to describe the behavior of fixed-bed adsorbers. Combining the results of this analysis with experimental observations has confirmed that the process of platelet deposition from whole blood onto glass bead surfaces is entirely adsorption controlled. In contrast to this finding, a theory often used to predict the performance of a wide range of filtration processes has been utilized to show that platelet deposition from PRP is dominated not by the adsorption step, but by resistances to platelet transport which are confined to the plasma phase. Furthermore, a direct relationship between platelet retention in glass bead columns and hematocrit has been observed using whole blood and ghost cell suspensions. These results, which are in accord with observations made by Zuckeret al. (1972), strongly suggest that ADP released from red cells cannot account for the increased retention with increased hematocrit. This behavior can be explained, however, by recognizing that the efective platelet diffusivity is considerably enhanced by increasing the hematocrit of red cell or ghost cell suspensions and consequently the frequency of cell-cell interactions. As confirmed experimentally, these physical interactions, as opposed to biochemical factors, are primarily responsible for determining the observed changes in platelet retention when the suspending medium is gradually changed from PRP (0% hct) to normal hematocrit values. Furthermore, theoretical and experimental techniques are described which permit, for the first time, a quantitative measure of platelet retention in columns packed with glass beads which is independent of both hemodynamic factors and column geometry. This new measure of platelet retention is shown to relate directly to the affinity of platelets for one another and for solid surfacesin vitro, thereby offering the possibility of using glass bead columns as highly sensitive diagnostic tools for the detection of hemorrhagic disorders.