Viability assessment of the liver during ex-situ machine perfusion prior to transplantation.

PURPOSE OF REVIEW: In an attempt to reduce waiting list mortality in liver transplantation, less-than-ideal quality donor livers from extended criteria donors are increasingly accepted. Predicting the outcome of these organs remains a challenge. Machine perfusion provides the unique possibility to assess donor liver viability pretransplantation and predict postreperfusion organ function. RECENT FINDINGS: Assessing liver viability during hypothermic machine perfusion remains challenging, as the liver is not metabolically active. Nevertheless, the levels of flavin mononucleotide, transaminases, lactate dehydrogenase, glucose and pH in the perfusate have proven to be predictors of liver viability. During normothermic machine perfusion, the liver is metabolically active and in addition to the perfusate levels of pH, transaminases, glucose and lactate, the production of bile is a crucial criterion for hepatocyte viability. Cholangiocyte viability can be determined by analyzing bile composition. The differences between perfusate and bile levels of pH, bicarbonate and glucose are good predictors of freedom from ischemic cholangiopathy. SUMMARY: Although consensus is lacking regarding precise cut-off values during machine perfusion, there is general consensus on the importance of evaluating both hepatocyte and cholangiocyte compartments. The challenge is to reach consensus for increased organ utilization, while at the same time pushing the boundaries by expanding the possibilities for viability testing.

The economic impact of machine perfusion technology in liver transplantation.

INTRODUCTION: Several clinical studies have demonstrated the safety, feasibility, and efficacy of machine perfusion in liver transplantation, although its economic outcomes are still underexplored. This review aimed to examine the costs related to machine perfusion and its associated outcomes. METHODS: Expert opinion of several groups representing different machine perfusion modalities. Critical analysis of the published literature reporting the economic outcomes of the most used techniques of machine perfusion in liver transplantation (normothermic and hypothermic ex situ machine perfusion and in situ normothermic regional perfusion). RESULTS: Machine perfusion costs include disposable components of the perfusion device, perfusate components, personnel and facility fees, and depreciation of the perfusion device or device lease fee. The limited current literature suggests that although this upfront cost varies between perfusion modalities, its use is highly likely to be cost-effective. Optimization of the donor liver utilization rate, local conditions of transplant programs (long waiting list times and higher MELD scores), a decreased rate of complications, changes in logistics, and length of hospital stay are potential cost savings points that must highlight the expected benefits of this intervention. An additional unaccounted factor is that machine perfusion optimizing donor organ utilization allows patients to be transplanted earlier, avoiding clinical deterioration while on the waiting list and the costs associated with hospital admissions and other required procedures. CONCLUSION: So far, the clinical benefits have guided machine perfusion implementation in liver transplantation. Albeit there is data suggesting the economic benefit of the technique, further investigation of its costs to healthcare systems and society and associated outcomes is needed.

Subnormothermic Machine Perfusion of Steatotic Livers Results in Increased Energy Charge at the Cost of Anti-Oxidant Capacity Compared to Normothermic Perfusion.

There continues to be significant debate regarding the most effective mode of ex situ machine perfusion of livers for transplantation. Subnormothermic (SNMP) and normothermic machine perfusion (NMP) are two methods with different benefits. We examined the metabolomic profiles of discarded steatotic human livers during three hours of subnormothermic or normothermic machine perfusion. Steatotic livers regenerate higher stores of ATP during SNMP than NMP. However, there is a significant depletion of available glutathione during SNMP, likely due to an inability to overcome the high energy threshold needed to synthesize glutathione. This highlights the increased oxidative stress apparent in steatotic livers. Rescue of discarded steatotic livers with machine perfusion may require the optimization of redox status through repletion or supplementation of reducing agents.

Transplantation of High-risk Donor Livers After Ex Situ Resuscitation and Assessment Using Combined Hypo- and Normothermic Machine Perfusion: A Prospective Clinical Trial.

OBJECTIVE: The aim of this study was to evaluate sequential hypothermic and normothermic machine perfusion (NMP) as a tool to resuscitate and assess viability of initially declined donor livers to enable safe transplantation. SUMMARY BACKGROUND DATA: Machine perfusion is increasingly used to resuscitate and test the function of donor livers. Although (dual) hypothermic oxygenated machine perfusion ([D]HOPE) resuscitates livers after cold storage, NMP enables assessment of hepatobiliary function. METHODS: In a prospective clinical trial, nationwide declined livers were subjected to ex situ NMP (viability assessment phase), preceded by 1-hour DHOPE (resuscitation phase) and 1 hour of controlled oxygenated rewarming (COR), using a perfusion fluid containing an hemoglobin-based oxygen carrier. During the first 2.5 hours of NMP, hepatobiliary viability was assessed, using predefined criteria: perfusate lactate <1.7 mmol/L, pH 7.35 to 7.45, bile production >10 mL, and bile pH >7.45. Livers meeting all criteria were accepted for transplantation. Primary endpoint was 3-month graft survival. RESULTS: Sixteen livers underwent DHOPE-COR-NMP. All livers were from donors after circulatory death, with median age of 63 (range 42-82) years and median Eurotransplant donor risk index of 2.82. During NMP, all livers cleared lactate and produced sufficient bile volume, but in 5 livers bile pH remained <7.45. The 11 (69%) livers that met all viability criteria were successfully transplanted, with 100% patient and graft survival at 3 and 6 months. Introduction of DHOPE-COR-NMP increased the number of deceased donor liver transplants by 20%. CONCLUSIONS: Sequential DHOPE-COR-NMP enabled resuscitation and safe selection of initially declined high-risk donor livers, thereby increasing the number of transplantable livers by 20%. TRIAL REGISTRATION: www.trialregister.nl; NTR5972.

Current policy for allocation of donor livers in the Netherlands advantages primary sclerosing cholangitis patients on the liver transplantation waiting list-a retrospective study.

Studies from the USA and Nordic countries indicate primary sclerosing cholangitis (PSC) patients have low mortality on the liver transplantation (LTx) waiting list. However, this may vary among geographical areas. Therefore, we compared waiting list mortality and post-transplant survival between laboratory model for end-stage liver disease (LM) and MELD exception (ME)-prioritized PSC and non-PSC candidates in a nationwide study in the Netherlands. A retrospective analysis of patients waitlisted from 2006 to 2013 was conducted. A total of 852 candidates (146 PSC) were waitlisted of whom 609 (71.5%) underwent LTx and 159 (18.7%) died before transplantation. None of the ME PSC patients died, and they had a higher probability of LTx than LM PSC [HR obtained by considering ME as a time-dependent covariate (HRME 9.86; 95% CI 6.14-15.85)] and ME non-PSC patients (HRME 4.60; 95% CI 3.78-5.61). After liver transplantation, PSC patients alive at 3 years of follow-up had a higher probability of relisting than non-PSC patients (HR 7.94; 95% CI 1.98-31.85) but a significantly lower mortality (HR 0.51; 95% CI 0.27-0.95). In conclusion, current LTx prioritization advantages PSC patients on the LTx waiting list. Receiving ME points is strongly associated with timely LTx.

Criteria for viability assessment of discarded human donor livers during ex vivo normothermic machine perfusion.

Although normothermic machine perfusion of donor livers may allow assessment of graft viability prior to transplantation, there are currently no data on what would be a good parameter of graft viability. To determine whether bile production is a suitable biomarker that can be used to discriminate viable from non-viable livers we have studied functional performance as well as biochemical and histological evidence of hepatobiliary injury during ex vivo normothermic machine perfusion of human donor livers. After a median duration of cold storage of 6.5 h, twelve extended criteria human donor livers that were declined for transplantation were ex vivo perfused for 6 h at 37 °C with an oxygenated solution based on red blood cells and plasma, using pressure controlled pulsatile perfusion of the hepatic artery and continuous portal perfusion. During perfusion, two patterns of bile flow were identified: (1) steadily increasing bile production, resulting in a cumulative output of ≥ 30 g after 6 h (high bile output group), and (2) a cumulative bile production <20 g in 6 h (low bile output group). Concentrations of transaminases and potassium in the perfusion fluid were significantly higher in the low bile output group, compared to the high bile output group. Biliary concentrations of bilirubin and bicarbonate were respectively 4 times and 2 times higher in the high bile output group. Livers in the low bile output group displayed more signs of hepatic necrosis and venous congestion, compared to the high bile output group. In conclusion, bile production could be an easily assessable biomarker of hepatic viability during ex vivo machine perfusion of human donor livers. It could potentially be used to identify extended criteria livers that are suitable for transplantation. These ex vivo findings need to be confirmed in a transplant experiment or a clinical trial.

The price of donation after cardiac death in liver transplantation: a prospective cost-effectiveness study.

This study aims to perform a detailed prospective observational multicenter cost-effectiveness study by comparing liver transplantations with donation after brain death (DBD) and donation after cardiac death (DCD) grafts. All liver transplantations in the three Dutch liver transplant centers between 2004 and 2009 were included with 1-year follow-up. Primary outcome parameter was cost per life year after transplantation. Secondary outcome parameters were 1-year patient and graft survival, complications, and patient-level costs. From 382 recipients that underwent 423 liver transplantations, 293 were primarily transplanted with DBD and 89 with DCD organs. Baseline characteristics were not different between both groups. The Donor Risk Index was significantly different as were cold and warm ischemic time. Ward stay was significantly longer in DCD transplantations. Patient and graft survival were not significantly different. Patients receiving DCD organs had more and more severe complications. The cost per life year for DBD was € 88,913 compared to € 112,376 for DCD. This difference was statistically significant. DCD livers have more and more severe complications, more reinterventions and consequently higher costs than DBD livers. However, patient and graft survival was not different in this study. Reimbursement should be differentiated to better accommodate DCD transplantations.

Interlaboratory variability in assessment of the model of end-stage liver disease score.

BACKGROUND: The model of end-stage liver disease (MELD) score is nowadays widely used to prioritize patients for liver transplantation. AIMS: To assess the contribution of the individual components of the MELD score in interlaboratory variability. METHODS: We sent 15 samples from patients listed for liver transplantation to seven different European laboratories who were asked to measure all three variables. In addition, 10 samples from patients on oral anticoagulant treatment were sent to the same labs for the international normalised ratio (INR) measurement. RESULTS AND CONCLUSIONS: In all 15 samples, a substantial and clinically relevant variation in the calculated MELD score was observed between laboratories. The mean difference in the MELD score between the highest- and the lowest-scoring laboratory was 4.8. The variation in creatinine measurements resulted in differences of up to three MELD points in a single patient when comparing the highest and the lowest scoring lab. The variation in bilirubin measurements only accounted for a difference of one point between the highest- and the lowest-scoring laboratory, but the variation in INRs resulted in differences of 2 to 12 MELD points. MELD scores or INR values were not substantially different in laboratories that used the Owren instead of the more widely used Quick methodology for INR measurements. The variability in the INR in patients on oral anticoagulants was substantially less as compared with the variability in patients with liver disease. In conclusion, we observed a large interlaboratory variation in the MELD score. This variation in the MELD score is primarily caused by the INR.