Normothermic machine perfusion for donor liver preservation

Abstract

Currently, liver transplantation is the only treatment for end-stage liver failure. Unfortunately, a sever shortage of donor organs causes significant mortality amongst patients awaiting transplantation. The donor organ shortage could be alleviated by using organs that are normally not accepted for transplantation, in particular organs obtained from so called non-heart beating donors (NHBD). However, currently used methods for donor organ storage prior to transplantation are unsuitable for this purpose. This thesis focuses on the exploration of normothermic machine perfusion (NMP) as alternative for static cold storage (SCS), the current clinical fold standard, in order to expand the donor organ pool. The first experimental section, chapter two, describes the development of a small animal model for NMP. With our model, we were able to maintain rat livers in a steady state for up to 12 hours, allowing subsequent orthotopic transplantation. Chapter three describes how we used our NMP model for preservation of NHBD rat livers. To model NHBD, rat livers were subjected to 60 minutes of ex-vivo warm ischemia at 34 °C. Subsequently, they were preserved by SCS at 4 °C, or by NMP at 37 °C. Graft viability was evaluated by orthotopic transplantation into syngeneic recipients. Short-term graft function was evaluated during ex-vivo sanguineous reperfusion. A drawback of the use of NMP for organ preservation is the complexity of the device required as opposed to SCS. This could be overcome by combining an initial period of SCS during transportation, with NMP once the organ has reached its destination in a transplant centre. Chapter four therefore evaluates whether a combination of NMP and SCS could be used for preservation of ischemic rat livers. We subjected livers to 45 min of ex-vivo warm ischemia and subsequently preserved them with a combination of 3 hours NMP at 37 °C, followed by 3 hours of cold storage in UW solution, or by 6 hours of cold storage UW solution alone. Graft viability was evaluated in an orthotopic transplantation model. Whether normothermic conditions are necessary for ischemic liver resuscitation has been subject to debate. In the following section, chapter five, we therefore evaluated the feasibility of using sub-normothermic machine perfusion for NHBD resuscitation. Rat livers subjected to one hour of ex-vivo ischemia were preserved with SNMP at either 20 or 30oC for 5 hours, followed by orthotropic transplantation. Short-term graft function was evaluated during ex-vivo reperfusion with diluted whole blood. Chapter six describes the use of metabolic flux analyis (MFA) to perform a dynamic metabolic analysis of fresh and ischemic livers during NMP. To evaluate the multiple pathways involved in recovery, MFA was used to correlate 28 measured and 34 calculated metabolite rates of uptake or release from hourly perfusion time points of ischemic and fresh organs during NMP. The final chapters seven through nine describe how data obtained during ex-vivo diluted blood reperfusion, is correlated with transplant-survival of ischemic rat livers after NMP to identify a predictor of transplant outcome using various mathematical models.