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 Zucker et 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 effective 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 surfaces in vitro,

thereby offering the possibility of using glass bead columns as highly sensitive diagnostic

tools for the detection of hemorrhagic disorders.