Biomedical Engineering Reference
In-Depth Information
Secondary
dialysate
Blood
Albumin dialysate
Blood
Albumin
Dialysate
AD
membrane
AR
column
AC
column
CD
membrane
HF
membrane
AF
membrane
AR
column
NR
column
Figure 1. Liver support devices. On the left: MARS (AD: albumin dialyzer; CD: con-
ventional dialyzer; AR: anionic resin column, AC: activated carbon column); a similar
scheme, excluding dialysate regeneration and recirculation, applies to SPAD. On the right:
Prometheus (NR: polymeric non-ionic resin column; AF: plasma fractionator, HF: high-
flux dialyzer); adsorption is performed directly after plasma filtration on a polysulphone
membrane.
focused on removal of bilirubin, that is a standard marker of the clinical state of liver-failure
patients and can be considered as representative of a wide class of strongly albumin-bound
toxins. Nevertheless, the results and the considerations reported in this chapter can be ex-
tended to other strongly albumin-bound toxins and other albumin dialysis LSDs.
2.
Thermodynamic Considerations
2.1.
Bilirubin-Albumin Binding
One of the key role of serum albumin is binding and transport in blood of a variety of
endogenous and exogenous molecules that include, among others, fatty acids, bile acids,
heterocyclic compounds as bilirubin, aromatic aminoacids as tryptophan and other indols.
As for bilirubin, it is generally agreed that the albumin molecule has one high affinity
binding site (Sudlow I) and one (or more) low affinity site(s) for this metabolite: neglect-
ing, for the sake of simplicity, the formation of complexes with more than two bilirubin
molecules, the following binding equilibria can be considered in a liquid phase containing
albumin and bilirubin
A+B AB
(1)
AB+B AB 2
(2)
with equilibrium constants given by
Μ AB −Μ A −Μ 0 B
RT
C AB
C A C B
K 1
= exp
=
(3)
 
 
 
 
 
 
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