A reproducible extended ex-vivo normothermic machine liver perfusion protocol utilising improved nutrition and targeted vascular flows

Abstract

Normothermic machine perfusion of donor livers has become standard practice in the field of transplantation, allowing the assessment of organs and safe extension of preservation times. Alongside its clinical uses, there has been expanding interest in extended normothermic machine perfusion (eNMP) of livers as a potential vehicle for medical research. Reproducible extended normothermic machine perfusion has remained elusive due to its increased complexity and monitoring requirements. We set out to develop a reproducible protocol for the extended normothermic machine perfusion of whole human livers. Human livers declined for transplantation were perfused using a blood-based perfusate at 36 °C using the Liver Assist device (XVIVO, Sweden), with continuous veno-venous haemofiltration in-parallel. We developed the protocol in a stepwise fashion. Perfusion techniques utilised included: targeted physiological vascular flows, phosphate replacement (to prevent hypophosphataemia), N-acetylcysteine (to prevent methaemoglobin accumulation), and the utilisation of sodium lactate as both a nutritional source and real-time measure of hepatocyte function. All five human livers perfused with the developed protocol showed preserved function with a median perfusion time of 168 h (range 120–184 h), with preserved viability throughout. Livers can be reproducibly perfused in excess of 120 (range 121–184) hours with evidence of preserved hepatocyte and cholangiocyte function. Clarke et al. present a reproducible protocol for the extended normothermic machine perfusion of human livers. Function and are preserved in five human livers perfused between 121–184 h. Circulating blood through human livers at normal body temperature allows transplant surgeons to assess the function of the liver and safely extend the time it is out of the body prior to transplantation. Extending this perfusion of livers beyond 24 h has proven difficult. We evaluated improved techniques to circulate blood through the liver. We found the improved techniques could enable a machine to be used to reliably perfuse livers for more than 24 h, whilst preserving the function of the liver. Our improved method included varying the blood flow according to liver size and removing waste products from the circulating blood. Using our method could enable more livers to be used successfully in transplant operations, reducing the waiting times for people requiring liver transplantation and improving their quality of life.