Controlled Oxygenated Rewarming of Cold Stored Livers Prior to Transplantation: First Clinical Application of a New Concept

Complex Hepatectomy Under Total Vascular Exclusion of the Liver Preserving the Caval Flow with Portal Hypothermic Perfusion and Temporary Portacaval Shunt: A Proof of Concept

BACKGROUND

Hypothermic liver perfusion decreases ischemia/reperfusion injury during hepatectomy under standard total vascular exclusion (TVE) of the liver. This surgery needs venovenous bypass and is hampered by high morbi-mortality. TVE preserving the inferior vena cava (IVC) flow is hemodynamically well tolerated but remains limited in duration when performed under liver normothermia. The objective of this study was to report the results of TVE preserving the caval flow, modified to allow hypothermic liver perfusion and obviate splanchnic congestion.

PATIENTS AND METHODS

The technique, indicated for tumors abutting large tributaries of the hepatic veins but sparing their roots in IVC and the latter, was applied when TVE was anticipated to last for ≥ 60 min. It combines continuous TVE preserving the IVC flow with hypothermic liver perfusion and temporary portacaval shunt (PCS). Results are given as median (range).

RESULTS

Vascular control was achieved in 13 patients with excellent hemodynamical tolerance. PCS was direct or via an interposed synthetic graft (five and eight cases, respectively). Liver temperature dropped to 16.5 (6-24) °C under perfusion of 2 (2-4) L of cold perfusate. TVE lasted 67 (54-125) min and 4.5 (0-8) blood units were transfused. Resection was major in nine cases and was complete in all cases. Five complications occurred in four patients, and the 90-day mortality rate was zero.

CONCLUSIONS

This technique maintains stable hemodynamics and combines the advantages of in situ or ex situ standard TVE with hypothermic liver perfusion, without their inherent prolongation of ischemia time and need for venovenous bypass.

Preclinical validation of a customized circuit for ex situ uninterrupted cold-to-warm prolonged perfusion of the liver

CONTEXT

Clinical adoption of ex situ liver perfusion is growing. While hypothermic perfusion protects against ischemia-reperfusion injury in marginal grafts, normothermic perfusion enables organ viability assessment and therefore selection of borderline grafts. The combination of hypothermic and normothermic perfusion, known as "cold-to-warm," may be the optimal sequence for organ preservation, but is difficult to achieve with most commercial perfusion systems. We developed an adaptable customized circuit allowing uninterrupted "cold-to-warm" perfusion and conducted preclinical studies on healthy porcine livers and discarded human livers to demonstrate the circuit's efficacy.

METHODS

In collaboration with bioengineers, we developed a customized circuit that adapts to extracorporeal circulation consoles used in cardiovascular surgery and includes a proprietary reservoir enabling easy perfusate change without interrupting perfusion. This preclinical study was conducted on porcine and human livers. Perfusion parameters (pressures, flows, oxygenation) and organ viability were monitored.

RESULTS

The customized circuit was adapted to a LivaNova S5® console, and the perfusions were flow-driven with real-time pressure monitoring. Ten porcine liver and 12 discarded human liver perfusions were performed during 14 to 18 h and 7 to 25 h, respectively. No hyperpressure was observed (porcine and human portal pressure 2-6 and 2-8 mm Hg; arterial pressure 10-65 and 20-65 mm Hg, respectively). No severe histological tissue injury was observed (Suzuki score ≤ 3 at the end of perfusion). Seven (70%) porcine livers and five (42%) human livers met the UK viability criteria.

CONCLUSION

The customized circuit and system design enables smooth uninterrupted "cold-to-warm" perfusion not present in current commercial perfusion systems.

Current Techniques and Indications for Machine Perfusion and Regional Perfusion in Deceased Donor Liver Transplantation

Since the advent of University of Wisconsin preservation solution in the 1980s, clinicians have learned to work within its confines. While affording improved outcomes, considerable limitations still exist and contribute to the large number of livers that go unused each year, often for fear they may never work. The last 10 years have seen the widespread availability of new perfusion modalities which provide an opportunity for assessing organ viability and prolonged organ storage. This review will discuss the role of in situ normothermic regional perfusion for livers donated after circulatory death. It will also describe the different modalities of ex situ perfusion, both normothermic and hypothermic, and discuss how they are thought to work and the opportunities afforded by them.

Machine perfusion in liver transplantation

BACKGROUND

Liver transplantation is the only chance of cure for people with end-stage liver disease and some people with advanced liver cancers or acute liver failure. The increasing prevalence of these conditions drives demand and necessitates the increasing use of donated livers which have traditionally been considered suboptimal. Several novel machine perfusion preservation technologies have been developed, which attempt to ameliorate some of the deleterious effects of ischaemia reperfusion injury. Machine perfusion technology aims to improve organ quality, thereby improving outcomes in recipients of suboptimal livers when compared to traditional static cold storage (SCS; ice box).

OBJECTIVES

To evaluate the effects of different methods of machine perfusion (including hypothermic oxygenated machine perfusion (HOPE), normothermic machine perfusion (NMP), controlled oxygenated rewarming, and normothermic regional perfusion) versus each other or versus static cold storage (SCS) in people undergoing liver transplantation.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 10 January 2023.

SELECTION CRITERIA

We included randomised clinical trials which compared different methods of machine perfusion, either with each other or with SCS. Studies comparing HOPE via both hepatic artery and portal vein, or via portal vein only, were grouped. The protocol detailed that we also planned to include quasi-randomised studies to assess treatment harms.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were 1. overall participant survival, 2. quality of life, and 3. serious adverse events. Secondary outcomes were 4. graft survival, 5. ischaemic biliary complications, 6. primary non-function of the graft, 7. early allograft function, 8. non-serious adverse events, 9. transplant utilisation, and 10. transaminase release during the first week post-transplant. We assessed bias using Cochrane's RoB 2 tool and used GRADE to assess certainty of evidence.

MAIN RESULTS

We included seven randomised trials (1024 transplant recipients from 1301 randomised/included livers). All trials were parallel two-group trials; four compared HOPE versus SCS, and three compared NMP versus SCS. No trials used normothermic regional perfusion. When compared with SCS, it was uncertain whether overall participant survival was improved with either HOPE (hazard ratio (HR) 0.91, 95% confidence interval (CI) 0.42 to 1.98; P = 0.81, I2 = 0%; 4 trials, 482 recipients; low-certainty evidence due to imprecision because of low number of events) or NMP (HR 1.08, 95% CI 0.31 to 3.80; P = 0.90; 1 trial, 222 recipients; very low-certainty evidence due to imprecision and risk of bias). No trials reported quality of life. When compared with SCS alone, HOPE was associated with improvement in the following clinically relevant outcomes: graft survival (HR 0.45, 95% CI 0.23 to 0.87; P = 0.02, I2 = 0%; 4 trials, 482 recipients; high-certainty evidence), serious adverse events in extended criteria DBD liver transplants (OR 0.45, 95% CI 0.22 to 0.91; P = 0.03, I2 = 0%; 2 trials, 156 participants; moderate-certainty evidence) and clinically significant ischaemic cholangiopathy in recipients of DCD livers (OR 0.31, 95% CI 0.11 to 0.92; P = 0.03; 1 trial, 156 recipients; high-certainty evidence). In contrast, NMP was not associated with improvement in any of these clinically relevant outcomes. NMP was associated with improved utilisation compared with SCS (one trial found a 50% lower rate of organ discard; P = 0.008), but the reasons underlying this effect are unknown. We identified 11 ongoing studies investigating machine perfusion technologies.

AUTHORS' CONCLUSIONS

In situations where the decision has been made to transplant a liver donated after circulatory death or donated following brain death, end-ischaemic HOPE will provide superior clinically relevant outcomes compared with SCS alone. Specifically, graft survival is improved (high-certainty evidence), serious adverse events are reduced (moderate-certainty evidence), and in donors after circulatory death, clinically relevant ischaemic biliary complications are reduced (high-certainty evidence). There is no good evidence that NMP has the same benefits over SCS in terms of these clinically relevant outcomes. NMP does appear to improve utilisation of grafts that would otherwise be discarded with SCS; however, the reasons for this, and whether this effect is specific to NMP, is not clear. Further studies into NMP viability criteria and utilisation, as well as head-to-head trials with other perfusion technologies are needed. In the setting of donation following circulatory death transplantation, further trials are needed to assess the effect of these ex situ machine perfusion methods against, or in combination with, normothermic regional perfusion.

Long-term ex situ normothermic perfusion of human split livers for more than 1 week

Current machine perfusion technology permits livers to be preserved ex situ for short periods to assess viability prior to transplant. Long-term normothermic perfusion of livers is an emerging field with tremendous potential for the assessment, recovery, and modification of organs. In this study, we aimed to develop a long-term model of ex situ perfusion including a surgical split and simultaneous perfusion of both partial organs. Human livers declined for transplantation were perfused using a red blood cell-based perfusate under normothermic conditions (36 °C) and then split and simultaneously perfused on separate machines. Ten human livers were split, resulting in 20 partial livers. The median ex situ viability was 125 h, and the median ex situ survival was 165 h. Long-term survival was demonstrated by lactate clearance, bile production, Factor-V production, and storage of adenosine triphosphate. Here, we report the long-term ex situ perfusion of human livers and demonstrate the ability to split and perfuse these organs using a standardised protocol.

Comparison Between Terminal or Preterminal Conditioning of Donor Livers by Ex Situ Machine Perfusion

BACKGROUND

The successful implementation of end-ischemic normothermic machine perfusion (NMP) into clinical practice comes along with unusual demands for trained personnel and technical facilities in the implantation clinic. This creates an interest to bundle expertise and professional equipment for execution of MP at regional pump centers at the disadvantage of adding a second short period of cold preservation while sending the reconditioned grafts to the actual implant clinic. Differences of liver recovery upon reperfusion either immediately after NMP or after 3 h of cold storage subsequent to NMP should therefore be evaluated.

METHODS

Rat livers were cold stored for 18 h, subjected to 2 h of NMP, and then either directly evaluated by ex vivo reperfusion or exposed to a second cold storage period of 3 h to simulate transport from the hub center to the implant clinic. Livers stored for 18 h by cold storage only served as controls.

RESULTS

Both MP regimens significantly reduced hepatic enzyme release and improved bile production, clearance of lactate, and energetic recovery compared with the controls. However, no differences were seen between the 2 MP groups.

CONCLUSIONS

The study provides first evidence that machine perfusion at regional perfusion centers may be a safe and economical alternative to the widespread individual efforts in the respective implantation clinics.

A Review of Machine Perfusion Strategies in Liver Transplantation

The acceptance of liver transplantation as the standard of care for end-stage liver diseases has led to a critical shortage of donor allografts. To expand the donor organ pool, many countries have liberalized the donor criteria including extended criteria donors and donation after circulatory death. These marginal livers are at a higher risk of injury when they are preserved using the standard static cold storage (SCS) preservation techniques. In recent years, research has focused on optimizing organ preservation techniques to protect these marginal livers. Machine perfusion (MP) of the expanded donor liver has witnessed considerable advancements in the last decade. Research has showed MP strategies to confer significant advantages over the SCS techniques, such as longer preservation times, viability assessment and the potential to recondition high risk allografts prior to implantation. In this review article, we address the topic of MP in liver allograft preservation, with emphasis on current trends in clinical application. We discuss the relevant clinical trials related to the techniques of hypothermic MP, normothermic MP, hypothermic oxygenated MP, and controlled oxygenated rewarming. We also discuss the potential applications of ex vivo therapeutics which may be relevant in the future to further optimize the allograft prior to transplantation.

Strategies for organ preservation: Current prospective and challenges

In current therapeutic approaches, transplantation of organs provides the best available treatment for a myriad of end-stage organ failures. However, shortage of organ donors, lacunae in preservation methods, and lack of a suitable match are the major constraints in advocating this life-sustaining therapy. There has been continuous progress in the strategies for organ preservation since its inception. Current strategies for organ preservation are based on the University of Wisconsin (UW) solution using the machine perfusion technique, which allows successful preservation of intra-abdominal organs (kidney and liver) but not intra-thoracic organs (lungs and heart). However, novel concepts with a wide range of adapted preservation technologies that can increase the shelf life of retrieved organs are still under investigation. The therapeutic interventions of in vitro-cultured stem cells could provide novel strategies for replacement of nonfunctional cells of damaged organs with that of functional ones. This review describes existing strategies, highlights recent advances, discusses challenges and innovative approaches for effective organ preservation, and describes application of stem cells to restore the functional activity of damaged organs for future clinical practices.

A Narrative Review of the Applications of Ex-vivo Human Liver Perfusion

Ex-vivo perfusion describes the extra-corporeal delivery of fluid to an organ or tissue. Although it has been widely studied in the context of organ preservation and transplantation, it has also proven to be an invaluable tool in the development of novel models for translational pre-clinical research. Here, we review the literature reporting ex-vivo human liver perfusion experiments to further understand current perfusion techniques and protocols together with their applications. A computerised search was made of Ovid, MEDLINE, and Embase using the search words "ex-vivo liver or hepatic perfusion". All relevant studies in English describing experiments using ex-vivo perfusion of human livers between 2016 and 2021, inclusive, were included. Of 21 reviewed studies, 19 used ex-vivo human liver perfusion in the context of allogeneic liver transplantation. The quality and size of the studies varied considerably. Human liver perfusion was almost exclusively limited to whole organs and "split" livers, although one study did describe the successful perfusion of tissue sections following a partial hepatectomy. This review of recent literature involving ex-vivo human liver perfusion demonstrates that the technique is not limited to whole liver perfusion. Split-liver perfusion is extremely valuable allowing one lobe to act as a control and increasing the number available for research. This review also highlights the present lack of any reports of segmental liver perfusion. The discarded donor liver is a scarce resource, and the successful use of segmental perfusion has the potential to expand the available experimental models to facilitate pre-clinical experimentation.

Hospital-Based Health Technology Assessment of Machine Perfusion Systems for Human Liver Transplantation

Based on published data, we have carried out a hospital-based health technology assessment of machine perfusion in adult liver transplantation using cold storage as a comparator, and within the perspective of a national health system-based hospital practice and disease-related group reimbursement policy. A systematic literature review on machine perfusion for adult liver transplantation was conducted exploring the Pubmed, CINAHL, Scopus, Embase, and Cochrane databases. The literature was analyzed with the intent to provide information on 6 dimensions and 19 items of the hospital-based health technology assessment framework derived from previous studies. Out of 705 references, 47 (6.7%) were retained for current analysis. Use of machine perfusion was associated with advantages over cold storage, i.e., a 10%–50% reduced risk for early allograft dysfunction, 7%–15% less ischemia reperfusion injury; 7%–50% fewer ischemic biliary complications, comparable or improved 1-year graft and patient survival, and up to a 50% lower graft discard rate. Hospital stay was not longer, and technical failures were anecdotal. Information on costs of machine perfusion is limited, but this technology is projected to increase hospital costs while cost-effectiveness analysis requires data over the transplant patient lifetime. No hospital-based health technology assessment study on machine perfusion in liver transplantation was previously conducted. From the hospital perspective, there is evidence of the clinical advantages of this novel technology, but strategies to counterbalance the increased costs of liver transplantation are urgently needed. Further studies should focus on the ethical, social, and organizational issues related to machine perfusion.

Ultrastructural changes in porcine liver sinusoidal endothelial cells of machine perfused liver donated after cardiac death

BACKGROUND

The machine perfusion (MP) preservation including hypothermic MP (HMP) and midthermic MP (MMP) has been considered as a promising strategy to preserve the functions of liver donated after cardiac death. The importance of understanding liver sinusoidal endothelial cells (LSEC) damage in regulating liver injury during MP has been emphasized. However, the ultrastructural changes in the LSEC and sinusoids around them after MP are unclear.

AIM

To investigate the ultrastructural changes in the LSEC and sinusoids around them after MP.

METHODS

Porcine liver grafts undergo a warm ischemia time of 60 minutes perfused for 4 h with modified University of Wisconsin gluconate solution. Group A grafts were preserved with HMP at 8 °C constantly for 4 h. Group B grafts were preserved with a rewarming solution at 22 °C by MMP for 4 h. Then the ultrastructural changes in the LSEC and sinusoids in Group A and B were comparatively analyzed by using osmium-maceration scanning electron microscopy with complementary transmission electron microscopy methods.

RESULTS

An analysis of the LSEC after warm ischemia revealed that mitochondria with condensed-shaped cristae, abnormal vesicles, reduction of ribosomes and the endoplasmic reticulum (ER) surround the mitochondria appeared. The MP subsequent after warm ischemia alleviate the abnormal vesicles and reduction of ribosomes in LSEC, which indicated the reduction of the ER damage. However, MMP could restore the tubular mitochondrial cristae, while after HMP the condensed and narrow mitochondrial cristae remained. In addition, the volume of the sinusoidal space in the liver grafts after MMP were restored, which indicated a lower risk of pressure injury than HMP.

CONCLUSION

MMP alleviates the ER damage of LSEC by warm ischemia, additionally restore the metabolism of LSEC via the normalization of mitochondria and prevent the share stress damage of liver grafts.

Robotic Kidney Transplant: The Modern Era Technical Revolution

Since the mid 20th century, transplantation has been a fast-developing field of contemporary medicine. The technical aspects of transplant operations were developed in the 1950s, with little significant change for >50 y. Those techniques allowed completion of various organ transplants and successful patient outcomes, but they also carried the inherent disadvantages of open surgery, such as postoperative pain, wound complications and infections, and prolonged length of hospital stay. The introduction and adoption of minimally invasive surgical techniques in the early 1990s to various surgical specialties including general, gynecologic, and urologic surgery led to significant improvements in postoperative patient care and outcomes. Organ transplantation, with its precision demanding vascular anastomoses, initially had been considered infeasible to accomplish with conventional laparoscopic devices. The institution of robotic surgical technology in the late 1990s and its subsequent wide utilization in fields of surgery changed its accessibility and acceptance. With the steady camera, 3D views, and multidirectional wrist motions, surgical robotics opened new horizons for technically demanding surgeries such as transplantation to be completed in a minimally invasive fashion. Furthermore, the hope was this technique could find a niche to treat patients who otherwise are not deemed surgical candidates in many fields including transplantation. Here in, robotics in kidney transplantation and its ability to help provide equity through access to transplantation will be discussed.

Hemoglobin-Based Oxygen Carriers: Potential Applications in Solid Organ Preservation

Ameliorating graft injury induced by ischemia and hypoxia, expanding the donor pool, and improving graft quality and recipient prognosis are still goals pursued by the transplant community. The preservation of organs during this process from donor to recipient is critical to the prognosis of both the graft and the recipient. At present, static cold storage, which is most widely used in clinical practice, not only reduces cell metabolism and oxygen demand through low temperature but also prevents cell edema and resists apoptosis through the application of traditional preservation solutions, but these do not improve hypoxia and increase oxygenation of the donor organ. In recent years, improving the ischemia and hypoxia of grafts during preservation and repairing the quality of marginal donor organs have been of great concern. Hemoglobin-based oxygen carriers (HBOCs) are “made of” natural hemoglobins that were originally developed as blood substitutes but have been extended to a variety of hypoxic clinical situations due to their ability to release oxygen. Compared with traditional preservation protocols, the addition of HBOCs to traditional preservation protocols provides more oxygen to organs to meet their energy metabolic needs, prolong preservation time, reduce ischemia–reperfusion injury to grafts, improve graft quality, and even increase the number of transplantable donors. The focus of the present study was to review the potential applications of HBOCs in solid organ preservation and provide new approaches to understanding the mechanism of the promising strategies for organ preservation.

Machine perfusion of the liver: Putting the puzzle pieces together

The realm of extended criteria liver transplantation created the 'adjacent possible' for dynamic organ preservation. Machine perfusion of the liver greatly expanded donor organ preservation possibilities, reaching before unattainable goals, including the mitigation of ischemia-reperfusion injury, viability assessment, and organ reconditioning prior to transplantation. However, current scientific evidence lacks uniformity between studies, perfusion protocols, and acceptance criteria. Construction of collaborative research networks for sharing knowledge should, therefore, enable the development of high-level evidence and guidelines for machine perfusion utilization, including donor acceptance criteria. Finally, this approach shall guarantee conditions for further progress to occur.

Normothermic Machine Perfusion (NMP) of the Liver - Current Status and Future Perspectives

A shortage of available organs for liver transplantation has led transplant surgeons and researchers to seek for innovative approaches in hepatoprotection and improvement of marginal allografts. The most exciting development in the past decade has been continuous mechanical perfusion of livers with blood or preservation solution to mitigate ischemia-reperfusion injury in contrast to the current standard of static cold storage. Two variations of machine perfusion have emerged in clinical practice. During hypothermic oxygenated perfusion the liver is perfused using a red blood cell-free perfusate at 2-10°C. In contrast, normothermic machine perfusion mimics physiologic liver perfusion using a red blood cell-based solution at 35.5-037.5°C, offering a multitude of potential advantages. Putative effects of normothermic perfusion include abrogation of hyperfibrinolysis after reperfusion and inflammation, glycogen repletion, and regeneration of adenosine triphosphate. Research in normothermic machine perfusion focuses on development of biomarkers predicting allograft quality and susceptibility to ischemia-reperfusion injury. Moreover, normothermic perfusion of marginal allografts allows for application of a variety of therapeutic interventions potentially enhancing organ quality. Both methods need to be subjected to translational investigation and evaluation in clinical trials. A clear advantage is transformation of an emergency procedure at night into a planned daytime surgery. Current clinical trials suggest that normothermic perfusion not only increases the use of hepatic allografts but is also associated with milder ischemia-reperfusion injury, resulting in a reduced risk of early allograft dysfunction and less biliary complications, including ischemic cholangiopathy, compared to static cold storage. The aim of this review is to give a concise overview of normothermic machine perfusion and its current applications, benefits, and possible advances in the future.

Advanced technologies for the preservation of mammalian biospecimens

The three classical core technologies for the preservation of live mammalian biospecimens-slow freezing, vitrification and hypothermic storage-limit the biomedical applications of biospecimens. In this Review, we summarize the principles and procedures of these three technologies, highlight how their limitations are being addressed via the combination of microfabrication and nanofabrication, materials science and thermal-fluid engineering and discuss the remaining challenges.

Transcriptomic profiles of human livers undergoing rewarming machine perfusion before transplantation-first insights

Machine perfusion by controlled oxygenated rewarming (COR) is feasible and safe in clinical application and result in a promising outcome. This study utilizes next-generation sequencing (NGS) to investigate the transcriptome of human liver tissue undergoing COR before liver transplantation. Cold-stored livers were subjected to machine-assisted slow COR for ~120 min before transplantation. Biopsies were taken before (preCOR) and after COR (postCOR) and 1 h after reperfusion (postRep). The samples were sequenced, using RNA-seq to analyze differential transcriptional changes between the different stages and treatments of the grafts. Comparison of differential gene expression preCOR and postCOR demonstrated 10 upregulated genes. postRep 97 and 178 genes were upregulated and 7 and 13 downregulated compared to preCOR and postCOR, respectively. A shift of gene expressions by machine perfusion to the TGF-beta pathway was observed. The present study demonstrates distinct transcriptome profiles associated with machine perfusion by COR and transplantation of human livers. Such data provide a deeper understanding of the molecular mechanisms of machine perfusion technology in human liver transplantation.

Mitochondrial Reprogramming—What Is the Benefit of Hypothermic Oxygenated Perfusion in Liver Transplantation?

Although machine perfusion is a hot topic today, we are just at the beginning of understanding the underlying mechanisms of protection. Recently, the first randomized controlled trial reported a significant reduction of ischemic cholangiopathies after transplantation of livers donated after circulatory death, provided the grafts were treated with an endischemic hypothermic oxygenated perfusion (HOPE). This approach has been known for more than fifty years, and was initially mainly used to preserve kidneys before implantation. Today there is an increasing interest in this and other dynamic preservation technologies and various centers have tested different approaches in clinical trials and cohort studies. Based on this, there is a need for uniform perfusion settings (perfusion route and duration), and the development of general guidelines regarding the duration of cold storage in context of the overall donor risk is also required to better compare various trial results. This article will highlight how cold perfusion protects organs mechanistically, and target such technical challenges with the perfusion setting. Finally, the options for viability testing during hypothermic perfusion will be discussed.

[Machine Perfusion for Liver Transplantation - What is Possible and Where Do We Stand in Germany? Review of the Literature and Results of a National Survey]

Machine perfusion of donor livers is currently regarded as the most important innovation in transplant surgery to address the continuing shortage of organs in liver transplantation. Hypothermic machine perfusion (HMP) is safe to use and appears to reduce the risk of biliary complications and improve the long-term survival of transplanted organs following preservation by cold static storage - even in donors after cardiac death. A potential functional test of donor organs during HMP uses flavin mononucleotide and is still under clinical investigation. Normothermic machine perfusion (NMP) has a greater risk of technical problems, but functional testing using conventional laboratory parameters during NMP allows significant expansion of the donor pool, even though no prospective randomised study has been able to demonstrate a survival advantage for transplanted organs after NMP. In addition, the preservation time of the donor organs can be significantly extended with the help of NMP, which is particularly advantageous for complex recipient operations and/or logistics. Both methods could be applied for various scenarios in transplantation medicine - theoretically also in combination. The majority of German transplant centres regard machine perfusion as an important innovation and already actively perform perfusions or are in preparation for doing so. However, the overall practical experience in Germany is still relatively low, with only 2 centres having performed more than 20 perfusions. In the coming years, multi-centre efforts to conduct clinical trials and to develop national guidelines on machine perfusion will therefore be indispensable in order to define the potential of these technological developments objectively and to exploit it optimally for the field of transplantation medicine.

Early Allograft Dysfunction Increases Hospital Associated Costs After Liver Transplantation-A Propensity Score-Matched Analysis

Concepts to ameliorate the continued mismatch between demand for liver allografts and supply include the acceptance of allografts that meet extended donor criteria (ECD). ECD grafts are generally associated with an increased rate of complications such as early allograft dysfunction (EAD). The costs of liver transplantation for the health care system with respect to specific risk factors remain unclear and are subject to change. We analyzed 317 liver transplant recipients from 2013 to 2018 for outcome after liver transplantation and hospital costs in a German transplant center. In our study period, 1-year survival after transplantation was 80.1% (95% confidence interval: 75.8%-84.6%) and median hospital stay was 33 days (interquartile rage: 24), with mean hospital costs of €115,924 (SD €113,347). There was a positive correlation between costs and laboratory Model for End-Stage Liver Disease score (r_s = 0.48, P < 0.001), and the development of EAD increased hospital costs by €26,229. ECD grafts were not associated with a higher risk of EAD in our cohort. When adjusting for recipient-associated risk factors such as laboratory Model for End-Stage Liver Disease score, recipient age, and split liver transplantation with propensity score matching, only EAD and cold ischemia increased total costs. Conclusion: Our data show that EAD leads to significantly higher hospital costs for liver transplantation, which are primarily attributed to recipient health status. Strategies to reduce the incidence of EAD are needed to control costs in liver transplantation.

Ex vivo machine perfusion: current applications and future directions in liver transplantation

BACKGROUND

Liver transplantation is the only curative treatment option for end-stage liver disease; however, its use remains limited due to a shortage of suitable organs. In recent years, ex vivo liver machine perfusion has been introduced to liver transplantation, as a means to expand the donor organ pool.

PURPOSE

To present a systematic review of prospective clinical studies on ex vivo liver machine perfusion, in order to assess current applications and highlight future directions.

METHODS

A systematic literature search of both PubMed and ISI web of science databases as well as the ClinicalTrials.gov registry was performed.

RESULTS

Twenty-one articles on prospective clinical trials on ex vivo liver machine perfusion were identified. Out of these, eight reported on hypothermic, eleven on normothermic, and two on sequential perfusion. These trials have demonstrated the safety and feasibility of ex vivo liver machine perfusion in both standard and expanded criteria donors. Currently, there are twelve studies enrolled in the clinicaltrials.gov  registry, and these focus on use of ex vivo perfusion in extended criteria donors and declined organs.

CONCLUSION

Ex vivo liver machine perfusion seems to be a suitable strategy to expand the donor pool for liver transplantation and holds promise as a platform for reconditioning diseased organs.

Research progress on hepatic machine perfusion

Nowadays, liver transplantation is the most effective treatment for end-stage liver disease. However, the increasing imbalance between growing demand for liver transplantation and the shortage of donor pool restricts the development of liver transplantation. How to expand the donor pool is a significant problem to be solved clinically. Many doctors have devoted themselves to marginal grafting, which introduces livers with barely passable quality but a high risk of transplant failure into the donor pool. However, existing common methods of preserving marginal grafts lead to both high risk of postoperative complications and high mortality. The application of machine perfusion allows surgeons to make marginal livers meet the standard criteria for transplant, which shows promising prospect in preserving and repairing donor livers and improving ischemia reperfusion injury. This review summarizes the progress of recent researches on hepatic machine perfusion.

Mitochondria as Therapeutic Targets in Transplantation

Advances in surgical procedures, technology, and immune suppression have transformed organ transplantation. However, the metabolic changes that occur during organ retrieval, storage, and implantation have been relatively neglected since the developments many decades ago of cold storage organ preservation solutions. In this review we discuss how the metabolic changes that occur within the organ during transplantation, particularly those associated with mitochondria, may contribute to the outcome. We show how a better understanding of these processes can lead to changes in surgical practice and the development of new drug classes to improve the function and longevity of transplanted grafts, while increasing the pool of organs available for transplantation.

Tryptophan Metabolism via the Kynurenine Pathway: Implications for Graft Optimization during Machine Perfusion

Access to liver transplantation continues to be hindered by the severe organ shortage. Extended-criteria donor livers could be used to expand the donor pool but are prone to ischemia-reperfusion injury (IRI) and post-transplant graft dysfunction. Ex situ machine perfusion may be used as a platform to rehabilitate discarded or extended-criteria livers prior to transplantation, though there is a lack of data guiding the utilization of different perfusion modalities and therapeutics. Since amino acid derivatives involved in inflammatory and antioxidant pathways are critical in IRI, we analyzed differences in amino acid metabolism in seven discarded non-steatotic human livers during normothermic- (NMP) and subnormothermic-machine perfusion (SNMP) using data from untargeted metabolomic profiling. We found notable differences in tryptophan, histamine, and glutathione metabolism. Greater tryptophan metabolism via the kynurenine pathway during NMP was indicated by significantly higher kynurenine and kynurenate tissue concentrations compared to pre-perfusion levels. Livers undergoing SNMP demonstrated impaired glutathione synthesis indicated by depletion of reduced and oxidized glutathione tissue concentrations. Notably, ATP and energy charge ratios were greater in livers during SNMP compared to NMP. Given these findings, several targeted therapeutic interventions are proposed to mitigate IRI during liver machine perfusion and optimize marginal liver grafts during SNMP and NMP.

The ultrastructural characteristics of bile canaliculus in porcine liver donated after cardiac death and machine perfusion preservation

The effects of each type of machine perfusion preservation (MP) of liver grafts donated after cardiac death on the bile canaliculi of hepatocytes remain unclear. We analyzed the intracellular three-dimensional ultrastructure of the bile canaliculi and hepatocyte endomembrane systems in porcine liver grafts after warm ischemia followed by successive MP with modified University of Wisconsin gluconate solution. Transmission and osmium-maceration scanning electron microscopy revealed that lumen volume of the bile canaliculi decreased after warm ischemia. In liver grafts preserved by hypothermic MP condition, bile canaliculi tended to recover in terms of lumen volume, while their microvilli regressed. In contrast, midthermic MP condition preserved the functional form of the microvilli of the bile canaliculi. Machine perfusion preservation potentially restored the bile canaliculus lumen and alleviated the cessation of cellular endocrine processes due to warm ischemia. In addition, midthermic MP condition prevented the retraction of the microvilli of bile canaliculi, suggesting further mitigation of the damage of the bile canaliculi.

Subzero non-frozen preservation of human livers in the supercooled state

Preservation of human organs at subzero temperatures has been an elusive goal for decades. The major complication hindering successful subzero preservation is the formation of ice at temperatures below freezing. Supercooling, or subzero non-freezing, preservation completely avoids ice formation at subzero temperatures. We previously showed that rat livers can be viably preserved three times longer by supercooling as compared to hypothermic preservation at +4 °C. Scalability of supercooling preservation to human organs was intrinsically limited because of volume-dependent stochastic ice formation at subzero temperatures. However, we recently adapted the rat preservation approach so it could be applied to larger organs. Here, we describe a supercooling protocol that averts freezing of human livers by minimizing air-liquid interfaces as favorable sites of ice nucleation and uses preconditioning with cryoprotective agents to depress the freezing point of the liver tissue. Human livers are homogeneously preconditioned during multiple machine perfusion stages at different temperatures. Including preparation, the protocol takes 31 h to complete. Using this protocol, human livers can be stored free of ice at -4 °C, which substantially extends the ex vivo life of the organ. To our knowledge, this is the first detailed protocol describing how to perform subzero preservation of human organs.

Hypothermic Oxygenated New Machine Perfusion System in Liver and Kidney Transplantation of Extended Criteria Donors:First Italian Clinical Trial

With the aim to explore innovative tools for organ preservation, especially in marginal organs, we hereby describe a clinical trial of ex-vivo hypothermic oxygenated perfusion (HOPE) in the field of liver (LT) and kidney transplantation (KT) from Extended Criteria Donors (ECD) after brain death. A matched-case analysis of donor and recipient variables was developed: 10 HOPE-ECD livers and kidneys (HOPE-L and HOPE-K) were matched 1:3 with livers and kidneys preserved with static cold storage (SCS-L and SCS-K). HOPE and SCS groups resulted with similar basal characteristics, both for recipients and donors. Cumulative liver and kidney graft dysfunction were 10% (HOPE L-K) vs. 31.7%, in SCS group (p = 0.05). Primary non-function was 3.3% for SCS-L vs. 0% for HOPE-L. No primary non-function was reported in HOPE-K and SCS-K. Median peak aspartate aminotransferase within 7-days post-LT was significantly higher in SCS-L when compared to HOPE-L (637 vs.344 U/L, p = 0.007). Graft survival at 1-year post-transplant was 93.3% for SCS-L vs. 100% of HOPE-L and 90% for SCS-K vs. 100% of HOPE-K. Clinical outcomes support our hypothesis of machine perfusion being a safe and effective system to reduce ischemic preservation injuries in KT and in LT.

Addressing organ shortages: progress in donation after circulatory death for liver transplantation

Reducing wait list mortality among patients awaiting liver transplantation remains a substantial challenge because of organ shortage. In efforts to expand the donor pool there has been a trend toward increased use of donation after circulatory death (DCD) liver grafts. However, these marginal grafts are prone to higher complication rates, particularly biliary complications. In addition, many procured DCD livers are then deemed unsuitable for transplant. Despite these limitations, DCD grafts represent an important resource to address the current organ shortage, and as such there are research efforts directed toward improving the use of and outcomes for transplantation of these grafts. We review the current progress in DCD liver transplantation.

Ischemia-Reperfusion Injury in Marginal Liver Grafts and the Role of Hypothermic Machine Perfusion: Molecular Mechanisms and Clinical Implications

Ischemia-reperfusion injury (IRI) constitutes a significant source of morbidity and mortality after orthotopic liver transplantation (OLT). The allograft is metabolically impaired during warm and cold ischemia and is further damaged by a paradox reperfusion injury after revascularization and reoxygenation. Short-term and long-term complications including post-reperfusion syndrome, delayed graft function, and immune activation have been associated with IRI. Due to the current critical organ shortage, extended criteria grafts are increasingly considered for transplantation, however, with an elevated risk to develop significant features of IRI. In recent years, ex vivo machine perfusion (MP) of the donor liver has witnessed significant advancements. Here, we describe the concept of hypothermic (oxygenated) machine perfusion (HMP/HOPE) approaches and highlight which allografts may benefit from this technology. This review also summarizes clinical applications and the main aspects of ongoing randomized controlled trials on hypothermic perfusion. The mechanistic aspects of IRI and hypothermic MP-which include tissue energy replenishment, optimization of mitochondrial function, and the reduction of oxidative and inflammatory damage following reperfusion-will be comprehensively discussed within the context of current preclinical and clinical evidence. Finally, we highlight novel trends and future perspectives in the field of hypothermic MP in the context of recent findings of basic and translational research.

Long-term Outcomes After Controlled Oxygenated Rewarming of Human Livers Before Transplantation

Controlled oxygenated rewarming (COR) has been shown to be a feasible and safe method in clinical practice and to reduce peak serum transaminases after liver transplantation. This study aimed to demonstrate further clinical experience of this method of now 18 clinical liver transplantations utilizing COR and demonstrate the long-term results.

Methods

In this extended series of 18 patients, cold-stored livers were subjected to machine-assisted slow COR for ≈120 minutes before transplantation. A cohort of 178 patients transplanted during the same period with similar clinical characteristics were used for comparison of key outcomes.

Results

All livers were perfused in accordance to the COR protocol without incidences and transplanted successfully. Early allograft dysfunction was observed in 2 (11.1%) cases after COR. Liver elasticity measurements indicated normal healthy liver parenchyma at the last follow-up. Graft survival demonstrated excellent outcomes after COR. The 1-, 3-, and 5-year patient survival rates were 100%, 100%, and 93.8% compared with 84.5%, 82.0%, and 75.8% in the control group (P = 0.12).

Conclusions

The present study demonstrates excellent clinical outcomes after COR before liver transplantation. Comparison with a control cohort shows superiority of graft survival. Further evidence is needed to assess this promising method to improve organ preservation, finally.

Effect of Rewarming on Leukocyte-Endothelial Interaction After Deep Hypothermic Preservation

BACKGROUND The preservation of harvested organs plays an essential role in transplantation. Cold hypothermia is frequently applied but may lead to graft compromise resulting from reperfusion and rewarming injury. This study investigates the effect of deep hypothermia and posterior rewarming on leukocyte-endothelial interactions and junctional adhesion molecules. MATERIAL AND METHODS We established an in vitro model to investigate the transendothelial migration of leukocytes (TEM) during deep hypothermia (4°C) as well as during the post-hypothermic rewarming process. Additionally, leukocyte-endothelial interactions were analyzed by quantifying surface expression of the junctional adhesion molecules A (JAMA-A and JAM-B). RESULTS While deep hypothermia at 4°C was associated with reduced leukocyte infiltration, rewarming after hypothermic preservation resulted in a significant increase in TEM. This process is mainly triggered by activation of endothelial cells. Post-hypothermic rewarming caused a significant downregulation of JAM-A, whereas JAM-B was not altered through temperature modulation. CONCLUSIONS Hypothermia exerts a protective effect consisting of reduced leukocyte-endothelial interaction. Rewarming after hypothermic preservation, however, causes considerable upregulation of leukocyte infiltration. Downregulation of JAM-A may play a role in modulating TEM during hypothermia and rewarming. We conclude that the rewarming process is an essential but underestimated aspect during transplantation.

Pumping new life into old ideas: Preservation and rehabilitation of the liver using ex situ machine perfusion

Recent advances in machine perfusion technology have reinvigorated the field of liver transplantation with the possibilities of vastly improving the efficiency and safety of the life-saving procedure. With this improved preservation technology, transplant surgeons are now able to use previously untransplantable donor livers without significantly compromising patient outcomes. Early clinical studies demonstrate the ability to extend preservation times and assess a graft's potential viability using normothermic machine perfusion, in addition to restoring the energy supply in donor livers by supporting metabolism through circulation of vital nutrients and blood-based oxygen carriers. Future endeavors for surgeons and scientists should focus on improving criteria to assess viability, optimizing protocols for perfusion research, investigating mechanisms of poor graft viability, and targeting these mechanisms with novel therapies to improve graft function prior to transplantation. Long-term goals include extending preservation times on the scale of days to weeks, enabling long-distance organ sharing, and establishing regional organ perfusion centers to streamline the procurement, perfusion, and transplantation process.

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.

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.

The impact on the bioenergetic status and oxidative-mediated tissue injury of a combined protocol of hypothermic and normothermic machine perfusion using an acellular haemoglobin-based oxygen carrier: The cold-to-warm machine perfusion of the liver

Introduction

The combination of hypothermic and normothermic machine perfusion (HMP+NMP) of the liver provides individual benefits of both techniques, improving the rescue of marginal organs. The aim of this study was to investigate the effect on the bioenergetic status and the oxidative-mediated tissue injury of an uninterrupted combined protocol of HMP+NMP using a single haemoglobin-based oxygen carrier (HBOC)-based perfusate.

Methods

Ten discarded human donor livers had either 2 hours of dual hypothermic oxygenated perfusion (D-HOPE) with sequential controlled rewarming (COR) and then NMP using the HBOC-based perfusate uninterruptedly (cold-to-warm group); or 2 hours of hypothermic oxygenated perfusion (HOPE) with an oxygen carrier-free perfusate, followed by perfusate exchange and then NMP with an HBOC-based perfusate. Markers of liver function, tissue adenosine triphosphate (ATP) levels and tissue injury were systematically assessed.

Results

The hypothermic phase downregulated mitochondrial respiration and increased ATP levels in both groups. The cold-to-warm group presented higher arterial vascular resistance during rewarming/NMP (p = 0.03) with a trend of lower arterial flow (p = 0.09). At the end of NMP tissue expression of markers of reactive oxygen species production, oxidative injury and inflammation were comparable between the groups.

Conclusion

The uninterrupted combined protocol of HMP+NMP using an HBOC-based perfusate—cold-to-warm MP—mitigated the oxidative-mediated tissue injury and enhanced hepatic energy stores, similarly to an interrupted combined protocol; however, it simplified the logistics of this combination and may favour its clinical applicability.

Machine perfusion strategies in liver transplantation

Machine perfusion is a hot topic in liver transplantation and several new perfusion concepts are currently developed. Prior to introduction into routine clinical practice, however, such perfusion approaches need to demonstrate their impact on liver function, post-transplant complications, utilization rates of high-risk organs, and cost benefits. Therefore, based on results of experimental and clinical studies, the community has to recognize the limitations of this technology. In this review, we summarize current perfusion concepts and differences between protective mechanisms of ex- and in-situ perfusion techniques. Next, we discuss which graft types may benefit most from perfusion techniques, and highlight the current understanding of liver viability testing. Finally, we present results from recent clinical trials involving machine liver perfusion, and analyze the value of different outcome parameters, currently used as endpoints for randomized controlled trials in the field.

Influence of 4 preservation solutions on ICU stay, graft and patient survival following liver transplantation

OBJECTIVE

The goal of this study was to evaluate the prognostic role of four preservation solutions in liver transplantation (LT).

PATIENTS AND METHODS

This is a retrospective study originating from 22 French centers performing LT, registered in the prospective databank of the Cristal Biomedicine Agency between 2008 and 2013. The preservation solutions used were Celsior (CS), Institut Georges Lopez (IGL)-1, Solution de Conservation des Organes et des Tissus (SCOT) 15 and University of Wisconsin (UW) solutions. Exclusion criteria were preservation with unknown or inhomogeneous solutions, or Histidine-tryptophan-ketoglutarate (HTK) solution (representing only 3% of LT). Patient survival was the main endpoint. Secondary endpoints were graft survival and duration of stay in intensive care.

RESULTS

Of 6347 LT performed, 4928 were included in this study, for which the distribution of preservation solution was CS (30%), IGL-1 (44%), SCOT 15 (10%) and UW (16%). Patient survival was 86%, 80% and 74% at 1, 3 and 5 years after LT, respectively, without any statistically significant difference between the four solutions (P=0.78). Graft survival was 82%, 75% and 69% at 1, 3 and 5 years after LT, respectively, without any statistically significant difference between the four solutions (P=0.80). Duration of intensive care was different according to the solution used in univariate analysis (P<0.001), but this effect disappeared in multivariate analysis when the center performing the transplantation was accounted for.

CONCLUSION

The type of preservation solution used (CS, IGL-1, SCOT 15 or UW) did not have any influence on patient or graft survival after LT.

Can hypothermic oxygenated perfusion (HOPE) rescue futile DCD liver grafts?

BACKGROUND

The new UK-DCD-Risk-Score has been recently developed to predict graft loss in DCD liver transplantation. Donor-recipient combinations with a cumulative risk of >10 points were classified as futile and achieved an impaired one-year graft survival of <40%. The aim of this study was to show, if hypothermic oxygenated perfusion (HOPE) can rescue such extended DCD livers and improve outcomes.

METHODS

"Futile"-classified donor-recipient combinations were selected from our HOPE-treated human DCD liver cohort (01/2012-5/2017), with a minimum follow-up of one year. Main risk factors, which contribute to the classification "futile" include: elderly donors>60years, prolonged functional donor warm ischemia time (fDWIT > 30min), long cold ischemia time>6hrs, donor BMI>25 kg/m², advanced recipient age (>60years), MELD-score>25points and retransplantation status. Endpoints included all outcome measures during and after DCD LT.

RESULTS

Twenty-one donor-recipient combinations were classified futile (median UK-DCD-Risk-Score:11 points). The median donor age and fDWIT were 62 years and 36 min, respectively. After cold storage, livers underwent routine HOPE-treatment for 120 min. All grafts showed immediate function. One-year and 5-year tumor death censored graft survival was 86%.

CONCLUSION

HOPE-treatment achieved excellent outcomes, despite high-risk donor and recipient combinations. Such easy, endischemic perfusion approach may open the door for an increased utilization of futile DCD livers in other countries.

[Modern concepts for the dynamic preservation of the liver and kidneys in the context of transplantation]

The increasing demand on donor grafts has forced experimental research on transplantation medicine to develop more efficient organ preservation strategies. Simple cold storage of grafts rarely offers optimal conditions for extended criteria donor organs. Hypothermic, oxygenated machine perfusion (HMP) is a classical method of dynamic organ preservation, which enables the provision of oxygen and nutrients to the tissue and provides a metabolic recovery of the graft prior to implantation. A more modern approach is normothermic machine perfusion (NMP), which instead simulates physiological conditions and enables an ex vivo evaluation and treatment of organ grafts. However, studies have found that a preceding period of cold storage significantly mitigates the functional advantage of NMP. A strategy to circumvent this phenomenon is controlled oxygenated rewarming (COR). The cold-stored graft is slowly and gradually rewarmed to subnormothermic or normothermic temperatures, providing a gentle adaption of energy metabolism and counteracting events of rewarming injury.

Transplantation of high-risk donor livers after resuscitation and viability assessment using a combined protocol of oxygenated hypothermic, rewarming and normothermic machine perfusion: study protocol for a prospective, single-arm study (DHOPE-COR-NMP trial)

INTRODUCTION

Extended criteria donor (ECD) livers are increasingly accepted for transplantation in an attempt to reduce the gap between the number of patients on the waiting list and the available number of donor livers. ECD livers; however, carry an increased risk of developing primary non-function (PNF), early allograft dysfunction (EAD) or post-transplant cholangiopathy. Ischaemia-reperfusion injury (IRI) plays an important role in the development of these complications. Machine perfusion reduces IRI and allows for reconditioning and subsequent evaluation of liver grafts. Single or dual hypothermic oxygenated machine perfusion (DHOPE) (4°C-12°C) decreases IRI by resuscitation of mitochondria. Controlled oxygenated rewarming (COR) may further reduce IRI by preventing sudden temperature shifts. Subsequent normothermic machine perfusion (NMP) (37°C) allows for ex situ viability assessment to facilitate the selection of ECD livers with a low risk of PNF, EAD or post-transplant cholangiopathy.

METHODS AND ANALYSIS

This prospective, single-arm study is designed to resuscitate and evaluate initially nationwide declined ECD livers. End-ischaemic DHOPE will be performed for the initial mitochondrial and graft resuscitation, followed by COR of the donor liver to a normothermic temperature. Subsequently, NMP will be continued to assess viability of the liver. Transplantation into eligible recipients will proceed if all predetermined viability criteria are met within the first 150 min of NMP. To facilitate machine perfusion at different temperatures, a perfusion solution containing a haemoglobin-based oxygen carrier will be used. With this protocol, we aim to transplant extra livers. The primary endpoint is graft survival at 3 months after transplantation.

ETHICS AND DISSEMINATION

This protocol was approved by the medical ethical committee of Groningen, METc2016.281 in August 2016 and registered in the Dutch Trial registration number TRIAL REGISTRATION NUMBER: NTR5972, NCT02584283.