Biomedical Engineering Reference
In-Depth Information
6.
Conclusions
In this chapter, the application of an engineering analysis to albumin dialysis liver sup-
port devices was presented. Starting from the physico-chemical description of the ele-
mentary processes occurring in the device units, a mathematical model of a recirculating
albumin dialysis liver support device was built. The model was subsequently used to cal-
culate bilirubin clearances obtained by the device with different operating conditions. The
analysis was focused on bilirubin removal, since this toxin is an important marker of the
clinical state of liver failure patients and can also be considered representative of a wide
class of strongly albumin-bound toxins.
This approach proved to be helpful in gaining a deeper insight into the working princi-
ples of liver support devices, providing a rationale for some empirical findings and leading
to the detection of design issues.
In particular, the possible existence of an optimum dialysate albumin concentration
emerged. The optimal value should be determined as a trade-off between two opposing
effects of an increase of this parameter: the improvement of albumin dialysis efficiency on
one hand, and the impairment of dialysate regeneration by adsorption on the other hand.
The simulations, based partially on parameters determined by in vitro experiments,
showed that, for a device operating in conditions similar to those of MARS, the main effect
of a further increase of dialysate albumin concentration would be a reduction of dialysate
regeneration efficiency and, therefore, a more rapid reduction of the the device performance
with time. Furthermore, for such a device, overall bilirubin clearances didn't exceed 4%
of the blood flow-rate fed to the membrane module (in accordance with some literature
data), this poor performance being limited by the slow bilirubin mass transfer across the
membrane.
The information presented in this chapter can be helpful for the optimization of existing
liver support devices and for the design of new ones; nevertheless, for a complete assess-
ment of the performance of a given device, a similar analysis should be extended to the
clearance of other toxins and some of the model parameters should be also checked against
clinical data.
Acknowledgments
The Authors thank prof. Luigi Marrelli for his insightful comments, prof. Gilnardo
Novelli and dott. Vincenzo Morabito for the useful discussion about the medical aspects.
This work was financially supported by University of Rome “La Sapienza”
References
Abe, T; Shono, M; Kodama, T; Kita, Y; Fukagawa, M; Akizawa, T. Extracorporeal albu-
min dialysis.
Theapeutic Apheresis and Dialysis
, 2004, 8, 217- 222.
Annesini, MC; Di Paola, L; Marrelli, L; Piemonte, V; Turchetti, L. Bilirubin removal
from albumin-containing solution by adsorption on polymer resin.
The International
Journal of Artificial Organs
, 2005, 28, 686-693.
