Machine perfusion of the liver: past, present and future

Abstract

This review considers the potential of machine perfusion to preserve livers for clinical transplantation, including steatotic or ischaemically damaged grafts and aims to go over the most significant achievements in liver machine perfusion over the last year. To reach acceptance in liver preservation, machine perfusion will need to improve outcomes compared with simple cold storage (SCS), provide objective measures of graft viability, and resuscitate less-than-ideal grafts before transplantation. Current machine perfusion protocols comprise both hypothermic (HMP) and normothermic (NMP) approaches. HMP increases energy stores compared to SCS, and NMP shows additional resuscitative potential. Dutkowski transplanted ischaemically damaged pig livers after HMP following SCS, which avoided graft failure observed after SCS alone. Guarrera performed 20 clinical transplants after 4-7 h HMP. Friend has performed porcine transplantations after NMP of 4-20 h and univocally demonstrated the significant resuscitative effects on ischaemically damaged grafts otherwise destined to fail. Whereas NMP promises resuscitative effects, it demands challenging, near-physiologic conditions. Subnormothermic perfusion is being tested as a promising medium in between. Despite recent substantial improvements, liver preservation by machine perfusion remains limited and in contrast to the global revival of kidney machine perfusion. However, liver machine perfusion may be close to returning to clinical practice if it has not already done so. History shows that superiority alone does not guarantee immediate clinical use. Further clear-cut benefits of machine perfusion such as viability assessment will have to be accompanied by usability and human factors, and innovative and improved perfusion solutions applied in novel perfusion protocols.