Abstract
This chapter is focused on the design of artificial liver support devices (LSD). After a short overview of liver functions and pathologies, aimed at defining the minimum requirements for artificial devices, a survey of the different artificial liver support devices developed and used in clinical practice is reported. Subsequently, starting from a description of the physicochemical phenomena that characterize each unit operation used in the detoxification process (albumin dialysis and toxin adsorption), mathematical models of dialysis and adsorption units are developed and combined into an LSD model. A proposal for a first approach to a patient-device model is also considered to predict the evolution in time of toxin levels in patient blood and to evaluate the effectiveness of the treatment. The chapter ends with a survey on the bio-artificial liver devices.
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Notes
- 1.
MARS® can be considered as the earliest application of the albumin dialysis process. However, here MARS® is presented after SPAD following the order of increasing complexity.
- 2.
In contrast, high-volume plasma exchange, where patient’s plasma was removed by plasma filtration and replaced by fresh frozen plasma, may be capable of removing and replacing albumin (and other plasma proteins).
- 3.
It is generally agreed that the albumin molecule has one high-affinity binding site and one (or more) low-affinity site(s) for bilirubin; assuming independent binding of bilirubin to the two sites, the bound fraction of bilirubin is given by
Furthermore, a decrease of the apparent binding constant \(K_{B}\) from \(5\times 10^{7}\,{\mathrm{M}^{-1}}\) at low albumin concentration (15 µM) to \(5.4\times 10^{6}\,{\mathrm{M}^{-1}}\) at higher albumin concentration (300 µM) is also observed [155]; therefore, the saturation limit is not linear in the albumin concentration [157].
- 4.
When the affinity of the toxin for albumin is very high in both solutions (i.e., when the conditions given in Eq. 8.6 hold in both solutions), virtually all the toxin is in the bound form in both solutions and it may be assumed that \(c_{AT}\simeq c_{tox}\) and \(c_{A}\simeq c_{alb}-c_{tox}\)).
- 5.
A rigorous development, without the assumption \(c_{ tox }\ll c_{ alb }\) is reported in [143].
- 6.
For the derivation refer to Sect. 7.8.
- 7.
With regards to the data presented in [185], it is interesting to note that the presence of albumin in the solution resulted in a “back translation” of the breakthrough curves and decrease of breakthrough time compared to tryptophan adsorption from albumin-free solutions. This effect increased with increasing albumin concentration, reflecting the reduction of tryptophan uptake from albumin-containing solutions.
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© 2017 Springer-Verlag London
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Annesini, M.C., Marrelli, L., Piemonte, V., Turchetti, L. (2017). Artificial and Bio-Artificial Liver. In: Artificial Organ Engineering. Springer, London. https://doi.org/10.1007/978-1-4471-6443-2_8
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DOI: https://doi.org/10.1007/978-1-4471-6443-2_8
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