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

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: Livers can be reproducibly perfused in excess of 120 (range 121-184) hours with evidence of preserved hepatocyte and cholangiocyte function.

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.

SIMAP500: A novel risk score to identify recipients at higher risk of hepatocellular carcinoma recurrence following liver transplantation.

BACKGROUND: Recurrence of hepatocellular carcinoma (HCC) following liver transplantation (LT) has a devastating influence on recipients' survival; however, the risk of recurrence is not routinely stratified. Risk stratification is vital with a long LT waiting time, as that could influence the recurrence despite strict listing criteria. AIM: This study aims to identify predictors of recurrence and develop a novel risk prediction score to forecast HCC recurrence following LT. METHODS: A retrospective review of LT for HCC recipients at University Hospitals Birmingham between July 2011 and February 2020. Univariate and multivariate analyses were performed to identify recurrence predictors, based on which the novel SIMAP500 (satellite nodules, increase in size, microvascular invasion, AFP > 500, poor differentiation) risk score was proposed. RESULTS: 234 LTs for HCC were performed with a median follow-up of 5.3 years. Recurrence developed in 25 patients (10.7%). On univariate analyses, RETREAT score > 3, α-fetoprotein (AFP) at listing 100-500 and > 500, bridging, increased tumour size between imaging at the listing time and explant histology, increase in the size of viable tumour between listing and explant, presence of satellite nodules, micro- and macrovascular invasion on explant and poor differentiation of tumours were significantly associated with recurrence, based on which, the SIMAP500 risk score is proposed. The SIMAP500 demonstrated an excellent predictive ability (c-index = 0.803) and outperformed the RETREAT score (c-index = 0.73). SIMAP500 is indicative of the time to disease recurrence. CONCLUSION: SIMAP500 risk score identifies the LT recipients at risk of HCC recurrence. Risk stratification allows patient-centric post-transplant surveillance programs. Further validation of the score is recommended.

Discarded livers tested by normothermic machine perfusion in the VITTAL trial: Secondary end points and 5-year outcomes.

Normothermic machine perfusion (NMP) enables pretransplant assessment of high-risk donor livers. The VITTAL trial demonstrated that 71% of the currently discarded organs could be transplanted with 100% 90-day patient and graft survivals. Here, we report secondary end points and 5-year outcomes of this prospective, open-label, phase 2 adaptive single-arm study. The patient and graft survivals at 60 months were 82% and 72%, respectively. Four patients lost their graft due to nonanastomotic biliary strictures, one caused by hepatic artery thrombosis in a liver donated following brain death, and 3 in elderly livers donated after circulatory death (DCD), which all clinically manifested within 6 months after transplantation. There were no late graft losses for other reasons. All the 4 patients who died during the study follow-up had functioning grafts. Nonanastomotic biliary strictures developed in donated after circulatory death livers that failed to produce bile with pH >7.65 and bicarbonate levels >25 mmol/L. Histological assessment in these livers revealed high bile duct injury scores characterized by arterial medial necrosis. The quality of life at 6 months significantly improved in all but 4 patients suffering from nonanastomotic biliary strictures. This first report of long-term outcomes of high-risk livers assessed by normothermic machine perfusion demonstrated excellent 5-year survival without adverse effects in all organs functioning beyond 1 year (ClinicalTrials.gov number NCT02740608).

N-acetylcysteine: a novel approach to methaemoglobinaemia in normothermic liver machine perfusion.

Extended duration of normothermic machine perfusion (NMP) provides opportunities to resuscitate suboptimal donor livers. This intervention requires adequate oxygen delivery typically provided by a blood-based perfusion solution. Methaemoglobin (MetHb) results from the oxidation of iron within haemoglobin and represents a serious problem in perfusions lasting > 24 h. We explored the effects of anti-oxidant, N-acetylcysteine (NAC) on the accumulation of methaemoglobin. NMP was performed on nine human donor livers declined for transplantation: three were perfused without NAC (no-NAC group), and six organs perfused with an initial NAC bolus, followed by continuous infusion (NAC group), with hourly methaemoglobin perfusate measurements. In-vitro experiments examined the impact of NAC (3 mg) on red cells (30 ml) in the absence of liver tissue. The no-NAC group sustained perfusions for an average of 96 (range 87-102) h, universally developing methaemoglobinaemia (≥ 2%) observed after an average of 45 h, with subsequent steep rise. The NAC group was perfused for an average of 148 (range 90-184) h. Only 2 livers developed methaemoglobinaemia (peak MetHb of 6%), with an average onset of 116.5 h. Addition of NAC efficiently limits formation and accumulation of methaemoglobin during NMP, and allows the significant extension of perfusion duration.

Machine perfusion and the prevention of ischemic type biliary lesions following liver transplant: What is the evidence?

The widespread uptake of different machine perfusion (MP) strategies for liver transplant has been driven by an effort to minimize graft injury. Damage to the cholangiocytes during the liver donation, preservation, or early posttransplant period may result in stricturing of the biliary tree and inadequate biliary drainage. This problem continues to trouble clinicians, and may have catastrophic consequences for the graft and patient. Ischemic injury, as a result of compromised hepatic artery flow, is a well-known cause of biliary strictures, sepsis, and graft failure. However, very similar lesions can appear with a patent hepatic artery and these are known as ischemic type biliary lesions (ITBL) that are attributed to microcirculatory dysfunction rather than main hepatic arterial compromise. Both the warm and cold ischemic period duration appear to influence the onset of ITBL. All of the commonly used MP techniques deliver oxygen to the graft cells, and therefore may minimize the cholangiocyte injury and subsequently reduce the incidence of ITBL. As clinical experience and published evidence grows for these modalities, the impact they have on ITBL rates is important to consider. In this review, the evidence for the three commonly used MP strategies (abdominal normothermic regional perfusion [A-NRP], hypothermic oxygenated perfusion [HOPE], and normothermic machine perfusion [NMP] for ITBL prevention has been critically reviewed. Inconsistencies with ITBL definitions used in trials, coupled with variations in techniques of MP, make interpretation challenging. Overall, the evidence suggests that both HOPE and A-NRP prevent ITBL in donated after circulatory death grafts compared to cold storage. The evidence for ITBL prevention in donor after brain death grafts with any MP technique is weak.

Low C-reactive Protein and Urea Distinguish Primary Nonfunction From Early Allograft Dysfunction Within 48 Hours of Liver Transplantation.

Primary nonfunction (PNF) is a life-threatening complication of liver transplantation (LT), but in the early postoperative period, it can be difficult to differentiate from early allograft dysfunction (EAD). The aim of this study was to determine if serum biomarkers can distinguish PNF from EAD in the initial 48 h following LT. Materials and Methods: A retrospective study of adult patients that underwent LT between January 2010 and April 2020 was performed. Clinical parameters, absolute values and trends of C-reactive protein (CRP), blood urea, creatinine, liver function tests, platelets, and international normalized ratio in the initial 48 h after LT were compared between the EAD and PNF groups. Results: There were 1937 eligible LTs, with PNF and EAD occurring in 38 (2%) and 503 (26%) patients, respectively. A low serum CRP and urea were associated with PNF. CRP was able to differentiate between the PNF and EAD on postoperative day (POD)1 (20 versus 43 mg/L; P < 0.001) and POD2 (24 versus 77; P < 0.001). The area under the receiver operating characteristic curve (AUROC) of POD2 CRP was 0.770 (95% confidence interval [CI] 0.645-0.895). The urea value on POD2 (5.05 versus 9.0 mmol/L; P = 0.002) and trend of POD2:1 ratio (0.71 versus 1.32 mmol/L; P < 0.001) were significantly different between the groups. The AUROC of the change in urea from POD1 to 2 was 0.765 (95% CI 0.645-0.885). Aspartate transaminase was significantly different between the groups, with an AUROC of 0.884 (95% CI 0.753-1.00) on POD2. Discussion: The biochemical profile immediately following LT can distinguish PNF from EAD; CRP, urea, and aspartate transaminase are more effective than ALT and bilirubin in distinguishing PNF from EAD in the initial postoperative 48 h. Clinicians should consider the values of these markers when making treatment decisions.

Liver Disease in GLIS3 Mutations: Transplant Considerations and Bile Duct Paucity on Explant Histology.

GLI-similar 3 (GLIS3) gene mutation heterozygosity is characterized by neonatal diabetes and hypothyroidism. It has wide phenotypic variability. Liver disease is prevalent, and its complications in some phenotypes are life-limiting. Transplantation and the pathogenesis of GLIS3 liver disease are not well explored in the literature. We report 2 cases of children with GLIS3 mutations with chronic liver disease who required liver transplantation and we present a literature review discussing the pathogenic mechanisms and liver histology. Histology demonstrated predominantly biliary cirrhosis consistent with abnormal bile duct development. Both patients were considered for multi-organ transplantation (liver, pancreas with or without kidney) before receiving a liver transplant alone. Postoperative management can be challenging due to infection, renal disease, and brittle diabetes. GLIS3 mutations need to be added to the list of non-syndromic causes of bile duct paucity in the liver. Liver transplantation should be considered in patients with life-limiting complications related to liver disease.

Comparable Overall Survival in Patients with Hepatocellular Carcinoma Diagnosed within and outside a Surveillance Programme: The Potential Impact of Liver Cirrhosis.

Hepatocellular carcinoma (HCC) is the third leading cause of cancer death, and its incidence is rising. Mortality from HCC is predicted to increase by 140% by 2035. Surveillance of high-risk patients with cirrhosis or chronic liver disease may be one means of reducing HCC mortality, but the level of supporting evidence for international guidelines is low/moderate. This study explores the real-world experience of HCC surveillance at a tertiary referral centre. Electronic patient records for all new HCCs diagnosed between August 2012 and December 2021 were retrospectively reviewed. Patient and tumour characteristics were evaluated, including the co-existence of chronic liver disease, cancer treatment and survival, and categorised according to HCC diagnosis within or outside a surveillance programme. Patients with HCC who presented through surveillance had smaller tumours diagnosed at an earlier stage, but this did not translate into improved overall survival. All patients in surveillance had chronic liver disease, including 91% (n = 101) with cirrhosis, compared to 45% (n = 29) in the non-surveillance cohort. We propose that the immune dysfunction associated with cirrhosis predisposes patients to a more aggressive tumour biology than the largely non-cirrhotic population in the non-surveillance group.

Incidence of Gastrointestinal Bleeding After Transesophageal Echocardiography Use in Orthotopic Liver Transplantation.

The risk of upper gastrointestinal bleeding (UGIB) after transesophageal echocardiography (TEE) in patients with high grade esophageal varices (EV) that are undergoing Orthotopic Liver transplantation (OLT) is poorly understood. This was a retrospective single-centre cohort study in all patients that underwent OLT at Queen Elizabeth Hospital Birmingham between September 2016 and September 2018. The primary outcome was to determine the incidence of UGIB in patients that have undergone OLT with EV that received TEE. 401 patients were included in the study, of which 320 (80%) received TEE. The incidence of post-operative UGIB in patients that received TEE was 1.6% (5/320) in the entire cohort: 2.7% (4/149) in patients with no evidence of EV and 0.6% (1/171) in patients with EV. UGIB occurred in 1 patient with grade 2 EV and did not occur in patients with grade 1 or 3 EV. The incidence of UGIB in patients that received TEE was not statistically different to patients that did not: 1.6% (5/320) vs. 3.7% (3/81) p = 0.218. In conclusion, in patients that underwent OLT, intra-operative TEE use was associated with low rates of UGIB, even in cohorts with high grade EV. This suggests that TEE is a relatively safe method of haemodynamic monitoring in patients undergoing OLT.

Safety of Intraoperative Blood Salvage During Liver Transplantation in Patients With Hepatocellular Carcinoma: A Systematic Review and Meta-analysis.

OBJECTIVE: The effects of intraoperative blood salvage (IBS) on time to tumor recurrence, disease-free survival and overall survival in hepatocellular carcinoma (HCC) patients undergoing liver transplantation were assessed to evaluate the safety of IBS. BACKGROUND: IBS is highly effective to reduce the use of allogeneic blood transfusion. However, the safety of IBS during liver transplantation for patients with HCC is questioned due to fear of disseminating malignant cells. METHODS: Comprehensive searches through June 2021 were performed in 8 databases. The methodological quality of included studies was assessed using the Robins-I tool. Meta-analysis with the generic inverse variance method was performed to calculate pooled hazard ratios (HRs) for disease-free survival, HCC recurrence and overall survival. RESULTS: Nine studies were included (n=1997, IBS n=1200, no-IBS n=797). Use of IBS during liver transplantation was not associated with impaired disease-free survival [HR=0.90, 95% confidence interval (CI)=0.66-1.24, P=0.53, IBS n=394, no-IBS n=329], not associated with increased HCC recurrence (HR=0.83, 95% CI=0.57-1.23, P=0.36, IBS n=537, no-IBS n=382) and not associated with impaired overall survival (HR=1.04, 95% CI=0.79-1.37, P=0.76, IBS n=495, no-IBS n=356). CONCLUSIONS: Based on available observational data, use of IBS during liver transplantation in patients with HCC does not result in impaired disease-free survival, increased HCC recurrence or impaired overall survival. Therefore, use of IBS during liver transplantation for HCC patients is a safe procedure.

Normothermic Machine Perfusion-Improving the Supply of Transplantable Livers for High-Risk Recipients.

The effectiveness of liver transplantation to cure numerous diseases, alleviate suffering, and improve patient survival has led to an ever increasing demand. Improvements in preoperative management, surgical technique, and postoperative care have allowed increasingly complicated and high-risk patients to be safely transplanted. As a result, many patients are safely transplanted in the modern era that would have been considered untransplantable in times gone by. Despite this, more gains are possible as the science behind transplantation is increasingly understood. Normothermic machine perfusion of liver grafts builds on these gains further by increasing the safe use of grafts with suboptimal features, through objective assessment of both hepatocyte and cholangiocyte function. This technology can minimize cold ischemia, but prolong total preservation time, with particular benefits for suboptimal grafts and surgically challenging recipients. In addition to more physiological and favorable preservation conditions for grafts with risk factors for poor outcome, the extended preservation time benefits operative logistics by allowing a careful explant and complicated vascular reconstruction when presented with challenging surgical scenarios. This technology represents a significant advancement in graft preservation techniques and the transplant community must continue to incorporate this technology to ensure the benefits of liver transplant are maximized.

In situ normothermic regional perfusion versus ex situ normothermic machine perfusion in liver transplantation from donation after circulatory death.

In situ normothermic regional perfusion (NRP) and ex situ normothermic machine perfusion (NMP) aim to improve the outcomes of liver transplantation (LT) using controlled donation after circulatory death (cDCD). NRP and NMP have not yet been compared directly. In this international observational study, outcomes of LT performed between 2015 and 2019 for organs procured from cDCD donors subjected to NRP or NMP commenced at the donor center were compared using propensity score matching (PSM). Of the 224 cDCD donations in the NRP cohort that proceeded to asystole, 193 livers were procured, resulting in 157 transplants. In the NMP cohort, perfusion was commenced in all 40 cases and resulted in 34 transplants (use rates: 70% vs. 85% [p = 0.052], respectively). After PSM, 34 NMP liver recipients were matched with 68 NRP liver recipients. The two cohorts were similar for donor functional warm ischemia time (21 min after NRP vs. 20 min after NMP; p = 0.17), UK-Donation After Circulatory Death risk score (5 vs. 5 points; p = 0.38), and laboratory Model for End-Stage Liver Disease scores (12 vs. 12 points; p = 0.83). The incidence of nonanastomotic biliary strictures (1.5% vs. 2.9%; p > 0.99), early allograft dysfunction (20.6% vs. 8.8%; p = 0.13), and 30-day graft loss (4.4% vs. 8.8%; p = 0.40) were similar, although peak posttransplant aspartate aminotransferase levels were higher in the NRP cohort (872 vs. 344 IU/L; p < 0.001). NRP livers were more frequently allocated to recipients suffering from hepatocellular carcinoma (HCC; 60.3% vs. 20.6%; p < 0.001). HCC-censored 2-year graft and patient survival rates were 91.5% versus 88.2% (p = 0.52) and 97.9% versus 94.1% (p = 0.25) after NRP and NMP, respectively. Both perfusion techniques achieved similar outcomes and appeared to match benchmarks expected for donation after brain death livers. This study may inform the design of a definitive trial.

Meta-analysis of interrupted versus continuous suturing for Roux-en-Y hepaticojejunostomy and duct-to-duct choledochocholedochostomy.

AIMS: To compare outcomes of interrupted (IS) and continuous (CS) suturing techniques for Roux-en-Y hepaticojejunostomy and duct-to-duct choledochocholedochostomy. METHODS: The study protocol was prospectively registered in PROSPERO (registration number: CRD42021286294). A systematic search of MEDLINE, CENTRAL, and Web of Science and bibliographic reference lists were conducted (last search: 14th March 2022). All comparative studies reporting outcomes of IS and CS in hepaticojejunostomy and choledochocholedochostomy were included and their risk of bias was assessed using ROBINS-I tool. Overall biliary complications, bile leak, biliary stricture, cholangitis, liver abscess, and anastomosis time were the evaluated outcome parameters. RESULTS: Ten comparative studies (2 prospective and 8 retrospective) were included which reported 1617 patients of whom 1186 patients underwent Roux-en-Y hepaticojejunostomy (IS: 789, CS: 397) and the remaining 431 patients underwent duct-to-duct choledochocholedochostomy (IS: 168, CS: 263). Although use of IS for hepaticojejunostomy was associated with significantly longer anastomosis time (MD: 14.15 min, p=0.0002) compared to CS, there was no significant difference in overall biliary complications (OR: 1.34, p=0.11), bile leak (OR: 1.64, p=0.14), biliary stricture (OR: 0.84, p=0.65), cholangitis (OR: 1.54, p=0.35), or liver abscess (OR: 0.58, p=0.40) between two groups. Similarly, use of IS for choledochocholedochostomy was associated with no significant difference in risk of overall biliary complications (OR: 0.92, p=0.90), bile leak (OR: 1.70, p=0.28), or biliary stricture (OR: 1.07, p=0.92) compared to CS. CONCLUSIONS: Interrupted and continuous suturing techniques for Roux-en-Y hepaticojejunostomy or duct-to-duct choledochocholedochostomy seem to have comparable clinical outcomes. The available evidence may be subject to confounding by indication with respect to diameter of bile duct. Future high-quality research is encouraged to report the outcomes with respect to duct diameter and suture material.

Acute-on-chronic liver failure: A 20-year retrospective review of a tertiary paediatric liver centre.

AIM: Acute-on-chronic liver failure (ACLF) is an acute deterioration of pre-existing chronic liver disease related to a precipitating event. We characterised paediatric ACLF at Birmingham Children's Hospital (BCH) utilising European Association of Liver Disease CLIF criteria, including prevalence, triggers and outcomes. METHODS: All BCH patients from 2000 to 2020 with CLD who underwent initial liver transplant or died on the transplant waiting list or whilst too unwell to be listed were reviewed. RESULTS: From 2000 to 2020, 24 (4%) children with ACLF were identified. Death occurred in 18 (75%). Transplant occurred in 9 (36%), 3 of which died. ACLF triggers were sepsis organism negative 11 (46%), sepsis organism positive 8 (33%) and GI bleed 5 (17%). Bilirubin at the time of transplant/death in those with ACLF who lived compared with those who died was 529 umol/L (381) versus 665 (210) (p=0.38), creatinine 138 umol/L (147) versus 67 (46) (p=0.41), PT 33 sec (14) versus (32 (15) (p = 0.72), Grade 3, 4 hepatic encephalopathy 1 (17%) versus 10 (56%) (p = 0.17), vasopressor use 1 (17%) versus 17 (94%) (p = 0.001) and ventilation 3 (50%) versus 17 (94%) (p = 0.035). CONCLUSION: Acute-on-chronic liver failure whilst infrequent has high rates of mortality. The use of vasopressors and ventilation is more frequent in those who die from ACLF.

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.

Introduction of the Concept of Diagnostic Sensitivity and Specificity of Normothermic Perfusion Protocols to Assess High-Risk Donor Livers.

Normothermic machine perfusion (NMP) allows objective assessment of donor liver transplantability. Several viability evaluation protocols have been established, consisting of parameters such as perfusate lactate clearance, pH, transaminase levels, and the production and composition of bile. The aims of this study were to assess 3 such protocols, namely, those introduced by the teams from Birmingham (BP), Cambridge (CP), and Groningen (GP), using a cohort of high-risk marginal livers that had initially been deemed unsuitable for transplantation and to introduce the concept of the viability assessment sensitivity and specificity. To demonstrate and quantify the diagnostic accuracy of these protocols, we used a composite outcome of organ use and 24-month graft survival as a surrogate endpoint. The effects of assessment modifications, including the removal of the most stringent components of the protocols, were also assessed. Of the 31 organs, 22 were transplanted after a period of NMP, of which 18 achieved the outcome of 24-month graft survival. The BP yielded 94% sensitivity and 50% specificity when predicting this outcome. The GP and CP both seemed overly conservative, with 1 and 0 organs, respectively, meeting these protocols. Modification of the GP and CP to exclude their most stringent components increased this to 11 and 8 organs, respectively, and resulted in moderate sensitivity (56% and 44%) but high specificity (92% and 100%, respectively) with respect to the composite outcome. This study shows that the normothermic assessment protocols can be useful in identifying potentially viable organs but that the balance of risk of underuse and overuse varies by protocol.