312.9: Mathematical Modelling to Determine Segment Perfusion Parameters for Living Donor Liver Transplantation

Abstract

Introduction: Adult-to-Adult Living Donor Liver Transplantation (A2ALL-1) Cohort Study focused on hepatic blood flow and effect of portal modulation in smaller and left lobe grafts demonstrating a significantly (p = 0.03) higher graft dysfunction in modulated recipients versus unmodulated. The study concluded the need for prespecified portal flow and hepatic venous outflow modulation protocols to better define outcomes of volumetric interventions. We developed a mathematical model of the liver to determine hemodynamic parameters across segments following simulated liver resections and middle hepatic vein interventions in both the remnant donor liver and recipient grafts to predict functional graft outcomes prior to reperfusion. Methods: Arterial/portal/hepatic vein and terminal portal triad diameters from 12 deceased donor livers and biopsies were used in a custom lumped parameter model developed in MATLAB {Fig(a)}. Blood flow is modeled using the Hagen-Poiseuille equation, and the continuity equation is solved to obtain volume flow rate of the whole liver at every point throughout the network {Fig(b)}. Simulated right hepatectomy in the plane of resection shown in Fig(a) is used to derive variations in blood flow and volume through the modeled left liver lobe {Fig(c)}.Results: Schematic illustrations of the modeling components of liver segments demonstrate volume flow rate encoded in pseudocolor mapping in the donor liver before and after right hepatectomy {Fig(b&c)}. Localized increase in blood flow through 2nd and 3rd generations of vessel division is especially apparent in the donor’s simulated remnant left lobe {Fig(c)}. Volume and flow rate alterations in hepatic venous outflow following ligation/reconstruction of middle hepatic veins in the remnant left lobe is evident. Perfusion parameters in the donor graft are also captured to simulate graft perfusion prior to reperfusion in the recipient. Conclusion: Surgical intervention on the middle hepatic vein (MHV) is critical for donor remnant liver outflow and optimal perfusion in the donor graft. Mathematical simulations to predict hemodynamic inflow – outflow parameters in living donor liver transplantation could help guide MHV ligation and reconstruction as well as predict graft perfusion parameters prior to reperfusion.