Dual Hypothermic Oxygenated Machine Perfusion in Liver Transplantation Using Allografts From Donors After Brain Death

This will be a parallel, randomized controlled study on the effects of end-ischemic hypothermic oxygenated machine perfusion in liver transplantations from donors after brain death. Patients will be randomized to either hypothermic perfusion or simple cold storage (1:3 ratio). The primary end-point will be model for early graft dysfunction (MEAF) score, a recently validated continuous measure of allograft function in the early period after liver transplantation, calculated using serum alanine transaminase (ALT) activity, international normalized ratio for prothrombin time (INR), and serum bilirubin concentration within 3 first postoperative days. In the original study, the mean MEAF score was 5.01 with a standard deviation of 1.99. The primary hypothesis of this study is reduction of the mean MEAF score from 5 to 3.5 using hypothermic oxygenated machine perfusion. With the thresholds for type I error of 0.05 and power of 0.90, respectively, 1:3 allocation ratio, and a standard deviation of 1.99, the number of patients required to detect such difference is 26 in the hypothermic perfusion group and 78 in the simple cold storage group (104 in total). The inclusion criteria will comprise age >18 years, deceased-donor liver transplantation, and provision of informed consent. Exclusion criteria will comprise donation after cardiac death and either reduced or split graft. Secondary outcome measures will include 2-year recipient and graft survival, 2-year incidence of biliary complications, and complications in the 90-day postoperative period classified by type and their severity according to the Clavien-Dindo grading system.

Following provision of informed consent, recipients will be randomly assigned in a 1:3 ratio to either hypothermic perfusion group or simple static cold storage group. In the hypothermic perfusion group, allografts will be subject to end-ischemic hypothermic oxygenated perfusion at 12 degrees Celsius through both hepatic artery and portal vein after a period of simple cold storage at 4 degrees Celsius and immediately prior to implantation. The perfusion will last at least 2 hours and the period will be prolonged in case of ongoing hepatectomy, in order to perform graft implantation immediately after perfusion. Two wedge allograft biopsies will be performed at the beginning and after 2 hours of perfusion for the assessment of micro- and macrovesicular steatosis and ATP content. Samples of the perfusate will be taken at the beginning and every 30 minutes for the assessment of sodium, potassium, and lactate concentration, CO2 partial pressure, and FMN. Perfusate temperature, portal and arterial flow, and portal and arterial resistance will be closely monitored during the procedure. In the simple cold storage group, the allografts will be stored in perfusate at 4 degrees Celsius from the procurement until implantation. At the end of simple cold storage, a wedge biopsy will be taken for the assessment of micro- and macrovesicular steatosis and ATP content. In both groups during the back-table procedure, the allograft will be flushed with 1 litre of perfusate through the portal vein. At the end of flushing, a sample of perfusate will be taken from the right hepatic vein for assessment of FMN and lactate concentration.

In both groups, clinical, anthropometric, and laboratory pre-transplant data will be collected. This includes: indication for transplantation, Child-Turcotte-Pugh classification, presence of hepatitis B and C virus infection, model for end-stage liver disease (MELD) score (without exception points), patient weight, height, body mass index, and waist circumference, serum bilirubin, creatinine, glucose and albumin concentration, INR, and serum activity of transaminases. Relevant donor and procurement data will be collected, including donor age, height, body mass index, cause of death, ethnicity, serum sodium and bilirubin concentration, serum activity of transaminases, INR, and extraction time. Donor risk index will be calculated in every case. Duration of cold ischemia and several intraoperative parameters will be collected, including: duration of warm ischemia, intraoperative transfusions, serum sodium and potassium changes, occurrence of post-reperfusion syndrome, and duration of operation. A wedge biopsy will be performed in all patients 90 minutes after portal reperfusion for histological assessment of ischemia-reperfusion injury (Suzuki score), apoptosis, endothelial activation (vWF and P-selectin), activation of innate immunity (TLR4) , oxidative injury (MDA), and ATP content. Blood samples will be collected immediately prior to reperfusion, 90 minutes after reperfusion, and at first postoperative day for the assessment of proinflammatory cytokines (TNFα, IL-2, IL-10), nuclear damage (HMGB1, 8-OHdG) and hepatocyte and cholangiocyte injury (transaminases and GGT activity). Following transplantation, all patients will be strictly followed according to the centre protocol with the assessment of serum activity of transaminases and GGTP, bilirubin and creatinine concentration, and INR twice daily within the first 3 postoperative days and daily or once every 2-3 days (according to the clinical assessment) thereafter. All complications occurring during the 90-postoperative period will be recorded, including primary non-function, early allograft dysfunction, biliary leaks, rejection episodes, and vascular complications. After hospital discharge, patients will be followed-up according to the center protocol with regular appointments in the outpatient clinic, every 2 weeks within first 2 months post-transplantation, every month up to 6 months, every 2-3 months up to 1 year, and every 3-6 months thereafter. Occurrence of all complications, particularly biliary complications, will be recorded. Both groups will be compared with respect to primary and secondary outcome measures, other pre-defined clinical outcomes, allograft injury and ATP content before implantation, and signs of ischemia-reperfusion injury, oxidative damage, apoptosis, ATP content, activation of innate immunity, and endothelial activation in allograft biopsies after reperfusion. Comparisons will also include pro-inflammatory cytokine release, circulating markers of nuclear injury, and other laboratory markers of allograft function and injury. Analyses of perfusate samples and allograft biopsies obtained before and after reperfusion is planned in order to determine both the impact of hypothermic perfusion on hepatic ATP content and mitochondrial injury (FMN). Further, results of perfusate analyses (particularly FMN) will be evaluated for potential association with clinical outcome measures, results of post-reperfusion allograft biopsies assessment, and serum markers of allograft function, injury, and inflammatory response in order to determine its role in pre-transplant assessment of allograft viability.