From Vascular Corrosion Cast to Electrical Analog Model for the Study of Human Liver Hemodynamics and Perfusion

Abstract

Hypothermic machine perfusion (HMP) is experiencing a revival in organ preservation due to the limitations of static cold storage and the need for better preservation of expanded criteria donor organs. For livers, perfusion protocols are still poorly defined, and damage of sinusoidal endothelial cells and heterogeneous perfusion are concerns. In this study, an electrical model of the human liver blood circulation is developed to enlighten internal pressure and flow distributions during HMP. Detailed vascular data on two human livers, obtained by combining vascular corrosion casting, micro-CT-imaging and image processing, were used to set up the electrical model. Anatomical data could be measured up to 5--6 vessel generations in each tree and showed exponential trend lines, used to predict data for higher generations. Simulated flow and pressure were in accordance with literature data. The model was able to simulate effects of pressure-driven HMP on liver hemodynamics and reproduced observations such as flow competition between the hepatic artery and portal vein. Our simulations further indicate that, from a pure biomechanical (shear stress) standpoint, HMP with low pressures should not result in organ damage, and that fluid viscosity has no effect on the shear stress experienced by the liver microcirculation in pressure-driven HMP.

Flow Competition between Hepatic Arterial and Portal Venous flow during Hypothermic Machine Perfusion Preservation of Porcine Livers

“…This seems to make sense, as P HA is higher compared to the P PV , and the hepatic natural flow regulation mechanisms, as described above, might be impaired or 13 deficient during the reduced metabolic state of hypothermia. In another study, the blood circulation through a human liver was mathematically simulated using an electrical model (23). The results of this model illustrated the appearance of flow competition when using an increased P HA or obstructed VCI as boundary conditions.…”

Porcine liver vascular bed in Biodur E20 corrosion casts

“…The most commonly used resins (Table 1) are methyl methacrylates such as Mercox [2] or modified Batson's 17 [5,6]. Methyl methacrylates are generally capillary-passable and alcohol non-resistant.…”

“…Its functional capacity is dependent on establishing new microcirculation [9]. Detailed anatomical data for the liver microvasculature are required to identify processes of vascular development or regression [17], for quantitative analysis [18,19,31] or for blood-flow modelling [5,29]. Vascular corrosion casts enable the creation of three-dimensional (3D) replicas of vascular trees.…”

Blood Flow Simulation for the Liver after a Virtual Right Lobe Hepatectomy

“…For hepatic circulation models we follow the strategy of Debautt et al [5], who employed a dual source circuit to study hepatic perfusion.…”

“…The difference between our model and that of [5] is that, instead of employing a large number of pi-filters for various PV, HV and HA generations, we simply used one pi-filter for each tree, therefore significantly simplified the circuit. The circuit, shown in Fig.…”