Prolonged Cold Ischemic Time Before Normothermic Machine Perfusion Accentuates Postreperfusion Hepatocellular Injury

Background: Prolonged cold ischemic time (CIT) before liver transplantation with static cold storage preservation is associated with higher rates of ischemia-related complications. With the introduction of normothermic machine perfusion (NMP), the overall incidence of early allograft dysfunction and biliary complications is lower. NMP can be used as a device-to-donor approach (with short CIT) or back-to-base model which is typically associated with longer CIT. It is unknown if NMP can rehabilitate organs that have suffered from prolonged CIT. Methods: Livers from a Yorkshire cross-bred pig donation after circulatory death model were recovered using conventional in situ flush with University of Wisconsin solution after systemic heparinization, followed by static cold storage in University of Wisconsin solution at 4 °C for short (2 h), long (24 h), or extended (48 h) periods of CIT before ex situ NMP. Visual appearance of the liver, perfusion hemodynamics including pressure and flow, as well as perfusate concentration of lactate, aspartate aminotransferase, and alanine aminotransferase, bile production, and histological evaluation of liver biopsies stained with hematoxylin and eosin and caspase-3 were compared between groups during NMP. Results: In addition to gross visual differences in the heterogeneity of livers with long or extended CIT compared with short CIT, the NMP perfusate from livers with extended CIT demonstrated an elevation in lactate that did not decrease with time. Although livers with long CIT showed a temporal reduction in NMP perfusate lactate concentration similar to those with short CIT, there was associated hepatocellular injury in the long CIT group manifested in the form of higher aspartate aminotransferase and alanine aminotransferase in perfusate, and increased frequency of caspase-3 positive cells indicating increased apoptosis. Conclusions: While NMP offers improved clinical outcomes post-liver transplantation, the application of NMP in back-to-base format with prolonged CIT before NMP requires further evaluation to understand the impact of ischemia-reperfusion injury.