Long-term outcomes after hypothermic oxygenated machine perfusion and transplantation of 1,202 donor livers in a real-world setting (HOPE-REAL study).

BACKGROUND & AIMS: Despite strong evidence for improved preservation of donor livers by machine perfusion, longer post-transplant follow-up data are urgently needed in an unselected patient population. We aimed to assess long-term outcomes after transplantation of hypothermic oxygenated machine perfusion (HOPE)-treated donor livers based on real-world data (i.e., IDEAL-D stage 4). METHODS: In this international, multicentre, observational cohort study, we collected data from adult recipients of HOPE-treated livers transplanted between January 2012 and December 2021. Analyses were stratified by donation after brain death (DBD) and donation after circulatory death (DCD), sub-divided by their respective risk categories. The primary outcome was death-censored graft survival. Secondary outcomes included the incidence of primary non-function (PNF) and ischaemic cholangiopathy (IC). RESULTS: We report on 1,202 liver transplantations (64% DBD) performed at 22 European centres. For DBD, a total number of 99 benchmark (8%), 176 standard (15%), and 493 extended-criteria (41%) cases were included. For DCD, 117 transplants were classified as low risk (10%), 186 as high risk (16%), and 131 as futile (11%), with significant risk profile variations among centres. Actuarial 1-, 3-, and 5-year death-censored graft survival rates for DBD and DCD livers were 95%, 92%, and 91%, vs. 92%, 87%, and 81%, respectively (log-rank p = 0.003). Within DBD and DCD strata, death-censored graft survival was similar among risk groups (log-rank p = 0.26, p = 0.99). Graft loss due to PNF or IC was 2.3% and 0.4% (DBD), and 5% and 4.1% (DCD). CONCLUSIONS: This study shows excellent 5-year survival after transplantation of HOPE-treated DBD and DCD livers with low rates of graft loss due to PNF or IC, irrespective of their individual risk profile. HOPE treatment has now reached IDEAL-D stage 4, which further supports its implementation in routine clinical practice. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05520320. IMPACT AND IMPLICATIONS: This study demonstrates the excellent long-term performance of hypothermic oxygenated machine perfusion (HOPE) treatment of donation after circulatory and donation after brain death liver grafts irrespective of their individual risk profile in a real-world setting, outside the evaluation of randomised-controlled trials. While previous studies have established safety, feasibility, and efficacy against the current standard, according to the IDEAL-D evaluation framework, HOPE treatment has now reached the final IDEAL-D stage 4, which further supports its implementation in routine clinical practice.

Assessment of liver graft quality during hypothermic oxygenated perfusion: the first international validation study.

BACKGROUND AND AIM: While it is currently assumed that liver assessment is only possible during normothermic machine perfusion (NMP), there is uncertainty regarding a reliable and quick prediction of graft injury during ex situ hypothermic oxygenated perfusion (HOPE). We therefore intended to test, in an international liver transplant cohort, recently described mitochondrial injury biomarkers measured during HOPE before liver transplantation. STUDY DESIGN: Perfusate samples of human livers from 10 centers in 7 countries with HOPE-experience were analyzed for released mitochondrial compounds, i.e. flavin mononucleotide (FMN), NADH, purine derivates and inflammatory markers. Perfusate FMN was correlated with graft loss due to primary non-function or symptomatic non-anastomotic biliary strictures (NAS), and kidney failure, as well as liver injury after transplantation. Livers deemed unsuitable for transplantation served as negative control. RESULTS: We collected 473 perfusate samples of human DCD (n=315) and DBD livers (n=158). Fluorometric assessment of FMN in perfusate was validated by mass spectrometry (R=0.7011,p<0.0001). Graft loss due to primary non-function or cholangiopathy was predicted by perfusate FMN values (c-statistic mass spectrometry 0.8418 (95%CI 0.7466-0.9370,p<0.0001), c-statistic fluorometry 0.7733 (95%CI 0.7006-0.8461,p<0.0001). Perfusate FMN values were also significantly correlated with symptomatic NAS and kidney failure, and superior in prediction of graft loss when compared to conventional scores derived from donor and recipient parameters, such as the donor risk index and the balance of risk score. Mitochondrial FMN values in liver tissues of non-utilized livers were low, and inversely correlated to high perfusate FMN values and purine metabolite release. CONCLUSIONS: This first international study validates the predictive value of the mitochondrial co-factor FMN, released from complex I during HOPE, and may therefore contribute to a better risk stratification of injured livers before implantation. IMPACT AND IMPLICATIONS: Analysis of 473 perfusates, collected from 10 international centers during hypothermic oxygenated perfusion (HOPE), revealed that mitochondria derived flavin mononucleotide (FMN) values in perfusate is predictive for graft loss, cholangiopathy, and kidney failure after liver transplantation. This result is of high clinical relevance, as recognition of graft quality is urgently needed to improve the safe utilization of marginal livers. Ex-situ machine perfusion approaches, such as HOPE, are therefore likely to increase the number of useable liver grafts.

Are there any benefits of prolonged hypothermic oxygenated perfusion? - Results from a national retrospective study.

BACKGROUND: Dual hypothermic oxygenated perfusion (DHOPE) is increasingly being used to extend liver preservation to improve transplant logistics. However, little is known about its benefits in high-risk liver grafts. This study aimed to investigate whether prolonged DHOPE provides benefits other than improved logistics in all liver types. METHODS: We performed a national retrospective cohort study of 177 liver transplants from 12 Italian centers preserved with DHOPE for ≥4h between 2015 and 2022. A control group of 177 DHOPEs of <4h during the same period was created using 1:1 propensity score matching. The impact of risk profiles and preservation times on the outcomes was assessed using univariable and multivariable regression models. RESULTS: No significant differences in post-transplant outcomes were found between prolonged and short DHOPEs. However, the prolonged group had a significantly lower incidence of post-transplant acute kidney injury (AKI) compared to the short group (30.5% vs. 44.6%, p=0.008). Among prolonged DHOPEs, no differences in transplant outcomes were observed according to donor risk index (DRI), Eurotransplant definition for marginal grafts, and balance of risk (BAR) score. DHOPE duration was associated with a lower risk of AKI in multivariable models adjusted for DRI, Eutrotransplant marginal grafts, and BAR score. Prolonged HOPE confirmed its protective effect against AKI in a multivariable model adjusted for donor and recipient risk factors [OR: 0.412, 95%CI: 0.200-0.850, p=0.016]. CONCLUSIONS: Prolonged DHOPE is widely used to improve transplant logistics, provides good results with high-risk grafts, and appears to be associated with a lower risk of post-transplant AKI. These results provide further insight into the important role of DHOPE in preventing post-transplant complications.

Recipient hepatectomy technique may affect oncological outcomes of liver transplantation for hepatocellular carcinoma.

To date, caval sparing (CS) and total caval replacement (TCR) for recipient hepatectomy in liver transplantation (LT) have been compared only in terms of surgical morbidity. Nonetheless, the CS technique is inherently associated with an increased manipulation of the native liver and later exclusion of the venous outflow, which may increase the risk of intraoperative shedding of tumor cells when LT is performed for HCC. A multicenter, retrospective study was performed to assess the impact of recipient hepatectomy (CS vs. TCR) on the risk of posttransplant HCC recurrence among 16 European transplant centers that used either TCR or CS recipient hepatectomy as an elective protocol technique. Exclusion criteria comprised cases of non-center-protocol recipient hepatectomy technique, living-donor LT, HCC diagnosis suspected on preoperative imaging but not confirmed at the pathological examination of the explanted liver, HCC in close contact with the IVC, and previous liver resection for HCC. In 2420 patients, CS and TCR approaches were used in 1452 (60%) and 968 (40%) cases, respectively. Group adjustment with inverse probability weighting was performed for high-volume center, recipient age, alcohol abuse, viral hepatitis, Child-Pugh class C, Model for End-Stage Liver Disease score, cold ischemia time, clinical HCC stage within Milan criteria, pre-LT downstaging/bridging therapies, pre-LT alphafetoprotein serum levels, number and size of tumor nodules, microvascular invasion, and complete necrosis of all tumor nodules (matched cohort, TCR, n = 938; CS, n = 935). In a multivariate cause-specific hazard model, CS was associated with a higher risk of HCC recurrence (HR: 1.536, p = 0.007). In conclusion, TCR recipient hepatectomy, compared to the CS approach, may be associated with some protective effect against post-LT tumor recurrence.

Machine perfusion techniques for liver transplantation - A meta-analysis of the first seven randomized-controlled trials.

BACKGROUND & AIMS: Machine perfusion is increasingly being tested in clinical transplantation. Despite this, the number of large prospective clinical trials remains limited. The aim of this study was to compare the impact of machine perfusion vs. static cold storage (SCS) on outcomes after liver transplantation. METHODS: A systematic search of MEDLINE, EMBASE, CINAHL and the Cochrane Central Register of Controlled Trials (CENTRAL) was conducted to identify randomized-controlled trials (RCTs) comparing "post-transplant" outcomes following machine perfusion vs. SCS. Data were pooled using random effect models. Risk ratios (RRs) were calculated for relevant outcomes. The quality of evidence was rated using the GRADE-framework. RESULTS: Seven RCTs were identified (four on hypothermic oxygenated [HOPE] and three on normothermic machine perfusion [NMP]), including a total number of 1,017 patients. Both techniques were associated with significantly lower rates of early allograft dysfunction (NMP: n = 41/282, SCS: n = 74/253, RR 0.50, 95% CI 0.30-0.86, p = 0.01, I2 = 39%; HOPE: n = 45/241, SCS: n = 97/241, RR 0.48, 95% CI 0.35-0.65, p < 0.00001, I2 = 5%). The HOPE approach led to a significant reduction in major complications (Clavien Grade ≥IIIb; HOPE: n = 90/241; SCS: n = 117/241, RR 0.76, 95% CI 0.63-0.93, p = 0.006, I2 = 0%), "re-transplantation" (HOPE: n = 1/163; SCS: n = 11/163; RR 0.21, 95% CI 0.04-0.96, p = 0.04; I2 = 0%) and graft loss (HOPE: n = 7/163; SCS: n = 19/163; RR 0.40, 95% CI 0.17-0.95, p = 0.04; I2 = 0%). Both perfusion techniques were found to 'likely' reduce overall biliary complications and non-anastomotic strictures. CONCLUSIONS: Although this study provides the highest current evidence on the role of machine perfusion, outcomes remain limited to a 1-year follow-up after liver transplantation. Comparative RCTs and large real-world cohort studies with longer follow-up are required to enhance the robustness of the data further, thereby supporting the introduction of perfusion technologies into routine clinical practice. PROSPERO-REGISTRATION: CRD42022355252. IMPACT AND IMPLICATIONS: For a decade, two dynamic perfusion concepts have increasingly been tested in several transplant centres worldwide. We undertook the first systematic review and meta-analysis and identified seven published RCTs, including 1,017 patients, evaluating the effect of machine perfusion (hypothermic and normothermic perfusion techniques) compared to static cold storage in liver transplantation. Both perfusion techniques were associated with lower rates of early allograft dysfunction in the first week after liver transplantation. Hypothermic oxygenated perfusion led to a reduction in major complications, lower "re-transplantation" rates and better graft survival. Both perfusion strategies were found to 'likely' reduce overall biliary complications and non-anastomotic biliary strictures. This study provides the highest current evidence on the role of machine perfusion. Outcomes remain limited to a 1-year post-transplant follow-up. Larger cohort studies with longer follow-up and clinical trials comparing the perfusion techniques are required. This is especially relevant to provide clarity and optimise implementation processes further to support the commissioning of this technology worldwide.

Utilization of livers donated after circulatory death for transplantation - An international comparison.

BACKGROUND & AIMS: Liver graft utilization rates are a hot topic due to the worldwide organ shortage and the increasing number of transplant candidates on waiting lists. Liver perfusion techniques have been introduced in several countries, and may help to increase the organ supply, as they potentially enable the assessment of livers before use. METHODS: Liver offers were counted from donation after circulatory death (DCD) donors (Maastricht type III) arising during the past decade in eight countries, including Belgium, France, Italy, the Netherlands, Spain, Switzerland, the UK, and the US. Initial type-III DCD liver offers were correlated with accepted, recovered and implanted livers. RESULTS: A total number of 34,269 DCD livers were offered, resulting in 9,780 liver transplants (28.5%). The discard rates were highest in the UK and US, ranging between 70 and 80%. In contrast, much lower DCD liver discard rates, e.g. between 30-40%, were found in Belgium, France, Italy, Spain and Switzerland. In addition, we observed large differences in the use of various machine perfusion techniques, as well as in graft and donor risk factors. For example, the median donor age and functional donor warm ischemia time were highest in Italy, e.g. >40 min, followed by Switzerland, France, and the Netherlands. Importantly, such varying risk profiles of accepted DCD livers between countries did not translate into large differences in 5-year graft survival rates, which ranged between 60-82% in this analysis. CONCLUSIONS: Overall, DCD liver discard rates across the eight countries were high, although this primarily reflects the situation in the Netherlands, the UK and the US. Countries where in situ and ex situ machine perfusion strategies were used routinely had better DCD utilization rates without compromised outcomes. IMPACT AND IMPLICATIONS: A significant number of Maastricht type III DCD livers are discarded across Europe and North America today. The overall utilization rate among eight Western countries is 28.5% but varies significantly between 18.9% and 74.2%. For example, the median DCD-III liver utilization in five countries, e.g. Belgium, France, Italy, Switzerland, and Spain is 65%, in contrast to 24% in the Netherlands, UK and US. Despite this, and despite different rules and strategies for organ acceptance and preservation, 1- and 5-year graft survival rates remain fairly similar among all participating countries. A highly varying experience with modern machine perfusion technology was observed. In situ and ex situ liver perfusion concepts, and application of assessment tools for type-III DCD livers before transplantation, may be a key explanation for the observed differences in DCD-III utilization.

Perfusion fluid-related infections in liver transplant recipients: A 5-year, single-center, retrospective study.

BACKGROUND: Perfusion fluid (PRF) is employed in liver transplantation (LTx) to maintain graft viability. Still, it represents a new potential way of infection transmission in LTx recipients (LTRs). Currently, no systematic research has investigated this topic. METHODS: Five-year single-center retrospective study conducted on LTRs from January 2017 to December 2021. We analyzed the incidence of positive PRF culture (PRF+) and perfusion fluid-related infections (PRF-RI) and their associated factors. We also assessed 1-year mortality, both overall and infection-related. RESULTS: Overall, 234 LTx were included. PRF+ were found in 31/234 (13.2%) LTx for a total of 37 isolates, with >1 isolate identified in 5 (2.1%) cases. High-risk microorganisms (Enterobacterales 13/37, Enterococcus spp. 4/37, S. aureus 3/37, P. aeruginosa 2/37) were isolated in 25/37 (67.6%) LTRs, the remaining being coagulase-negative staphylococci (12/37, 32.4%). Antimicrobial prophylaxis was administered to all LTRs, always active against the isolate even if suboptimal in 19 cases (61.3%). PRF-RI developed in 4/234 LTx (1.7%), and prophylaxis was considered suboptimal in 2/4 of them. The isolation of >1 microorganism in PRF culture was associated with an increased risk of developing PRF-RI (OR 37.5 [95%CI 2.6-548.4], p = .01). PRF-RI were associated with longer ICU stays (p = .005) and higher 1-year mortality, both overall and related to infections (p = .001). CONCLUSION: Despite PRF+ being infrequent, only a minority of patients develops PRF-RI. Nonetheless, once occurred, PRF-RI seems to increase morbidity and mortality rates.

Prolonged preservation by hypothermic machine perfusion facilitates logistics in liver transplantation: A European observational cohort study.

A short period (1-2 h) of hypothermic oxygenated machine perfusion (HOPE) after static cold storage is safe and reduces ischemia-reperfusion injury-related complications after liver transplantation. Machine perfusion time is occasionally prolonged for logistical reasons, but it is unknown if prolonged HOPE is safe and compromises outcomes. We conducted a multicenter, observational cohort study of patients transplanted with a liver preserved by prolonged (≥4 h) HOPE. Postoperative biochemistry, complications, and survival were evaluated. The cohort included 93 recipients from 12 European transplant centers between 2014-2021. The most common reason to prolong HOPE was the lack of an available operating room to start the transplant procedure. Grafts underwent HOPE for a median (range) of 4:42 h (4:00-8:35 h) with a total preservation time of 10:50 h (5:50-20:50 h). Postoperative peak ALT was 675 IU/L (interquartile range 419-1378 IU/L). The incidence of postoperative complications was low, and 1-year graft and patient survival were 94% and 88%, respectively. To conclude, good outcomes are achieved after transplantation of donor livers preserved with prolonged (median 4:42 h) HOPE, leading to a total preservation time of almost 21 h. These results suggest that simple, end-ischemic HOPE may be utilized for safe extension of the preservation time to ease transplantation logistics.

A multicentre outcome analysis to define global benchmarks for donation after circulatory death liver transplantation.

BACKGROUND & AIMS: The concept of benchmarking is established in the field of transplant surgery; however, benchmark values for donation after circulatory death (DCD) liver transplantation are not available. Thus, we aimed to identify the best possible outcomes in DCD liver transplantation and to propose outcome reference values. METHODS: Based on 2,219 controlled DCD liver transplantations, collected from 17 centres in North America and Europe, we identified 1,012 low-risk, primary, adult liver transplantations with a laboratory MELD score of ≤20 points, receiving a DCD liver with a total donor warm ischemia time of ≤30 minutes and asystolic donor warm ischemia time of ≤15 minutes. Clinically relevant outcomes were selected and complications were reported according to the Clavien-Dindo-Grading and the comprehensive complication index (CCI). Corresponding benchmark cut-offs were based on median values of each centre, where the 75th-percentile was considered. RESULTS: Benchmark cases represented between 19.7% and 75% of DCD transplantations in participating centres. The 1-year retransplant and mortality rates were 4.5% and 8.4% in the benchmark group, respectively. Within the first year of follow-up, 51.1% of recipients developed at least 1 major complication (≥Clavien-Dindo-Grade III). Benchmark cut-offs were ≤3 days and ≤16 days for ICU and hospital stay, ≤66% for severe recipient complications (≥Grade III), ≤16.8% for ischemic cholangiopathy, and ≤38.9 CCI points 1 year after transplant. Comparisons with higher risk groups showed more complications and impaired graft survival outside the benchmark cut-offs. Organ perfusion techniques reduced the complications to values below benchmark cut-offs, despite higher graft risk. CONCLUSIONS: Despite excellent 1-year survival, morbidity in benchmark cases remains high. Benchmark cut-offs targeting morbidity parameters offer a valid tool to assess the protective value of new preservation technologies in higher risk groups and to provide a valid comparator cohort for future clinical trials. LAY SUMMARY: The best possible outcomes after liver transplantation of grafts donated after circulatory death (DCD) were defined using the concept of benchmarking. These were based on 2,219 liver transplantations following controlled DCD donation in 17 centres worldwide. Donor and recipient combinations with higher risk had significantly worse outcomes. However, the use of novel organ perfusion technology helped high-risk patients achieve similar outcomes as the benchmark cohort.

A Minimally Invasive and Highly Effective Extracorporeal CO2 Removal Device Combined With a Continuous Renal Replacement Therapy.

OBJECTIVES: Extracorporeal carbon dioxide removal is used to treat patients suffering from acute respiratory failure. However, the procedure is hampered by the high blood flow required to achieve a significant CO2 clearance. We aimed to develop an ultralow blood flow device to effectively remove CO2 combined with continuous renal replacement therapy (CRRT). DESIGN: Preclinical, proof-of-concept study. SETTING: An extracorporeal circuit where 200 mL/min of blood flowed through a hemofilter connected to a closed-loop dialysate circuit. An ion-exchange resin acidified the dialysate upstream, a membrane lung to increase Pco2 and promote CO2 removal. PATIENTS: Six, 38.7 ± 2.0-kg female pigs. INTERVENTIONS: Different levels of acidification were tested (from 0 to 5 mEq/min). Two l/hr of postdilution CRRT were performed continuously. The respiratory rate was modified at each step to maintain arterial Pco2 at 50 mm Hg. MEASUREMENTS AND MAIN RESULTS: Increasing acidification enhanced CO2 removal efficiency of the membrane lung from 30 ± 5 (0 mEq/min) up to 145 ± 8 mL/min (5 mEq/min), with a 483% increase, representing the 73% ± 7% of the total body CO2 production. Minute ventilation decreased accordingly from 6.5 ± 0.7 to 1.7 ± 0.5 L/min. No major side effects occurred, except for transient tachycardia episodes. As expected from the alveolar gas equation, the natural lung Pao2 dropped at increasing acidification steps, given the high dissociation between the oxygenation and CO2 removal capability of the device, thus Pao2 decreased. CONCLUSIONS: This new extracorporeal ion-exchange resin-based multiple-organ support device proved extremely high efficiency in CO2 removal and continuous renal support in a preclinical setting. Further studies are required before clinical implementation.

Clinical assessment of liver metabolism during hypothermic oxygenated machine perfusion using microdialysis.

BACKGROUND: While growing evidence supports the use of hypothermic oxygenated machine perfusion (HOPE) in liver transplantation, its effects on liver metabolism are still incompletely understood. METHODS: To assess liver metabolism during HOPE using microdialysis (MD), we conducted an open-label, observational pilot study on 10 consecutive grafts treated with dual-HOPE (D-HOPE). Microdialysate and perfusate levels of glucose, lactate, pyruvate, glutamate, and flavin mononucleotide (FMN) were measured during back table preparation and D-HOPE and correlated to graft function and patient outcome. RESULTS: Median (IQR) MD and D-HOPE time was 228 (210, 245) and 116 (103, 143) min. Three grafts developed early allograft dysfunction (EAD), with one requiring retransplantation. During D-HOPE, MD glucose and lactate levels increased (ANOVA = 9.88 [p = 0.01] and 3.71 [p = 0.08]). Their 2nd-hour levels were higher in EAD group and positively correlated with L-GrAFT score. 2nd-hour MD glucose and lactate were also positively correlated with cold ischemia time, macrovesicular steatosis, weight gain during D-HOPE, and perfusate FMN. These correlations were not apparent when perfusate levels were considered. In contrast, MD FMN levels invariably dropped steeply after D-HOPE start, whereas perfusate FMN was higher in dysfunctioning grafts. CONCLUSION: MD glucose and lactate during D-HOPE are markers of hepatocellular injury and could represent additional elements of the viability assessment.

Mitochondria and ischemia reperfusion injury.

PURPOSE OF REVIEW: This review describes the role of mitochondria in ischemia-reperfusion-injury (IRI). RECENT FINDINGS: Mitochondria are the power-house of our cells and play a key role for the success of organ transplantation. With their respiratory chain, mitochondria are the main energy producers, to fuel metabolic processes, control cellular signalling and provide electrochemical integrity. The mitochondrial metabolism is however severely disturbed when ischemia occurs. Cellular energy depletes rapidly and various metabolites, including Succinate accumulate. At reperfusion, reactive oxygen species are immediately released from complex-I and initiate the IRI-cascade of inflammation. Prior to the development of novel therapies, the underlying mechanisms should be explored to target the best possible mitochondrial compound. A clinically relevant treatment should recharge energy and reduce Succinate accumulation before organ implantation. While many interventions focus instead on a specific molecule, which may inhibit downstream IRI-inflammation, mitochondrial protection can be directly achieved through hypothermic oxygenated perfusion (HOPE) before transplantation. SUMMARY: Mitochondria are attractive targets for novel molecules to limit IRI-associated inflammation. Although dynamic preservation techniques could serve as delivery tool for new therapeutic interventions, their own inherent mechanism should not only be studied, but considered as key treatment to reduce mitochondrial injury, as seen with the HOPE-approach.

The Interplay between Gut Microbiota and the Immune System in Liver Transplant Recipients and Its Role in Infections.

Liver transplantation (LT) is a life-saving strategy for patients with end-stage liver disease, hepatocellular carcinoma, and acute liver failure. LT success can be hampered by several short-term and long-term complications. Among them, bacterial infections, especially those due to multidrug-resistant germs, are particularly frequent, with a prevalence between 19 and 33% in the first 100 days after transplantation. In the last decades, a number of studies have highlighted how the gut microbiota (GM) is involved in several essential functions to ensure intestinal homeostasis, becoming one of the most important virtual metabolic organs. The GM works through different axes with other organs, and the gut-liver axis is among the most relevant and investigated ones. Any alteration or disruption of the GM is defined as dysbiosis. Peculiar phenotypes of GM dysbiosis have been associated with several liver conditions and complications, such as chronic hepatitis, fatty liver disease, cirrhosis, and hepatocellular carcinoma. Moreover, there is growing evidence of the crucial role of the GM in shaping the immune response, both locally and systemically, against pathogens. This paves the way to the manipulation of the GM as a therapeutic instrument to modulate infectious risk and outcome. In this minireview, we provide an overview of the current understanding of the interplay between the gut microbiota and the immune system in liver transplant recipients and the role of the former in infections.

The Role of Ex Situ Hypothermic Oxygenated Machine Perfusion and Cold Preservation Time in Extended Criteria Donation After Circulatory Death and Donation After Brain Death.

Hypothermic oxygenated machine perfusion (HOPE) has the potential to counterbalance the detrimental consequences of cold and warm ischemia time (WIT) in both donation after brain death (DBD) and donation after circulatory death (DCD). Herein we investigated the protective effects of HOPE in extended criteria donor (ECD) DBD and overextended WIT DCD grafts. The present retrospective case series included 50 livers subjected to end-ischemic HOPE or dual DHOPE in 2 liver transplantation (LT) centers from January 2018 to December 2019. All DCD donors were subjected to normothermic regional perfusion before organ procurement. Results are expressed as median (interquartile range [IQR]). In the study period, 21 grafts were derived from overextended WIT DCD donors (total WIT 54 [IQR, 40-60] minutes and 75% classified as futile), whereas 29 were from ECD DBD. A total of 3 biliary complications and 1 case of ischemia-type biliary lesion were diagnosed. The rate of early allograft dysfunction (EAD) was 20%, and those patients had higher Comprehensive Complication Index scores. Through a changing point analysis, cold preservation time >9 hours was associated with prolonged hospital stays (P = 0.02), higher rates of EAD (P = 0.009), and worst post-LT complications (P = 0.02). Logistic regression analyses indicated a significant relationship between cold preservation time and EAD. No differences were shown in terms of the early post-LT results between LTs performed with DCD and DBD. Overall, our data are fully comparable with benchmark criteria in LT. In conclusion, the application of DHOPE obtained satisfactory and promising results using ECD-DBD and overextended DCD grafts. Our findings indicate the need to reduce cold preservation time also in the setting of DHOPE, particularly for grafts showing poor quality.

Sequential Use of Normothermic Regional and Ex Situ Machine Perfusion in Donation After Circulatory Death Liver Transplant.

In Italy, 20 minutes of a continuous flat line on an electrocardiogram are required for declaration of death. In the setting of donation after circulatory death (DCD), prolonged warm ischemia time prompted the introduction of abdominal normothermic regional perfusion (NRP) followed by postprocurement ex situ machine perfusion (MP). This is a retrospective review of DCD liver transplantations (LTs) performed at 2 centers using sequential NRP and ex situ MP. From January 2018 to April 2019, 34 DCD donors were evaluated. Three (8.8%) were discarded before NRP, and 11 (32.4%) were discarded based on NRP parameters (n = 1, 3.0%), liver macroscopic appearance at procurement and/or biopsy results (n = 9, 26.5%), or severe macroangiopathy at back-table evaluation (n = 1, 3.0%). A total of 20 grafts (58.8%; 11 uncontrolled DCDs, 9 controlled DCDs) were considered eligible for LT, procured and perfused ex situ (9 normothermic and 11 dual hypothermic MPs). In total, 18 (52.9%; 11 uncontrolled) livers were eventually transplanted. Median (interquartile range) no-flow time was 32.5 (30-39) minutes, whereas median functional warm ischemia time was 52.5 (47-74) minutes (controlled DCD), and median low-flow time was 112 minutes (105-129 minutes; uncontrolled DCD). There was no primary nonfunction, while postreperfusion syndrome occurred in 8 (44%) recipients. Early allograft dysfunction happened in 5 (28%) patients, while acute kidney injury occurred in 5 (28%). After a median follow-up of 15.1 (9.5-22.3) months, 1 case of ischemic-type biliary lesions and 1 patient death were reported. DCD LT is feasible even with the 20-minute no-touch rule. Strict NRP and ex situ MP selection criteria are needed to optimize postoperative results.

Normothermic with or without hypothermic oxygenated perfusion for DCD before liver transplantation: European multicentric experience.

Grafts from donors with cardiac death (DCD) are subject to warm ischemia time (WIT) due to the no-touch-period (20 min in Italy and 5 min in France). These livers (LT) have higher rates of early allograft dysfunction (EAD), primary non-function (PNF), and ischemic cholangiopathy (IC) compared to LT from brain dead donors (DBD). Normothermic regional perfusion (NRP) is a beneficial strategy to mitigate organ damage; a further approach is the application of ex vivo hypothermic oxygenated perfusion (HOPE) after cold storage (CS). We retrospectively analyzed LTs performed from 2016 to 2019 at three transplant centers using NRP-DCD grafts: Bologna and Milan treated with HOPE (group A), Rennes preserved using CS (group B). No-flow period, total and functional WIT were significantly higher in group A than in group B (30.5±7.7 vs. 20.5±4.1; 56.5±20.4 vs. 39.1±21.6; 41.9±12.5 vs. 25.5±3.7; respectively, P < .05), without differences in the postoperative course. In particular, the two groups had similar rates of EAD (21.1% vs. 25.0%), PNF (5.3% vs. 6.3%), IC (0% vs. 12.5%, P = .112), and non-IC biliary complications (0% vs. 6.3%, P = .457), re-LT (10.5% vs.12.5%). This occurred despite a high rate of UK DCD risk score > 10 (63.2% A vs. 17.6% B, P = .000), which theoretically would make a large number of these transplants "futile." In conclusion, Italian and French groups had similar post-LT outcomes, probably related to the use of HOPE after CS in the case of long WIT.

Extracorporeal Chloride Removal by Electrodialysis. A Novel Approach to Correct Acidemia.

Rationale: Acidemia is a severe condition among critically ill patients. Despite lack of evidence, sodium bicarbonate is frequently used to correct pH; however, its administration is burdened by several side effects. We hypothesized that the reduction of plasma chloride concentration could be an alternative strategy to correct acidemia.Objectives: To evaluate feasibility, safety, and effectiveness of a novel strategy to correct acidemia through extracorporeal chloride removal by electrodialysis.Methods: Ten swine (six treated and four control animals) were sedated, mechanically ventilated and connected to an extracorporeal electrodialysis device capable of selectively removing chloride. In random order, an arterial pH of 7.15 was induced either through reduction of ventilation (respiratory acidosis) or through lactic acid infusion (metabolic acidosis). Acidosis was subsequently sustained for 12-14 hours. In treatment pigs, soon after reaching target acidemia, electrodialysis was started to restore pH.Measurements and Main Results: During respiratory acidosis, electrodialysis reduced plasma chloride concentration by 26 ± 5 mEq/L within 6 hours (final pH = 7.36 ± 0.04). Control animals exhibited incomplete and slower compensatory response to respiratory acidosis (final pH = 7.29 ± 0.03; P < 0.001). During metabolic acidosis, electrodialysis reduced plasma chloride concentration by 15 ± 3 mEq/L within 4 hours (final pH = 7.34 ± 0.07). No effective compensatory response occurred in control animals (final pH = 7.11 ± 0.08; P < 0.001). No complications occurred.Conclusions: We described the first in vivo application of an extracorporeal system targeted to correct severe acidemia by lowering plasma chloride concentration. Extracorporeal chloride removal by electrodialysis proved to be feasible, safe, and effective. Further studies are warranted to assess its performance in the presence of impaired respiratory and renal functions.

Machine Perfusions in Liver Transplantation: The Evidence-Based Position Paper of the Italian Society of Organ and Tissue Transplantation.

The use of machine perfusion (MP) in liver transplantation (LT) is spreading worldwide. However, its efficacy has not been demonstrated, and its proper clinical use has far to go to be widely implemented. The Società Italiana Trapianti d'Organo (SITO) promoted the development of an evidence-based position paper. A 3-step approach has been adopted to develop this position paper. First, SITO appointed a chair and a cochair who then assembled a working group with specific experience of MP in LT. The Guideline Development Group framed the clinical questions into a patient, intervention, control, and outcome (PICO) format, extracted and analyzed the available literature, ranked the quality of the evidence, and prepared and graded the recommendations. Recommendations were then discussed by all the members of the SITO and were voted on via the Delphi method by an institutional review board. Finally, they were evaluated and scored by a panel of external reviewers. All available literature was analyzed, and its quality was ranked. A total of 18 recommendations regarding the use and the efficacy of ex situ hypothermic and normothermic machine perfusion and sequential normothermic regional perfusion and ex situ MP were prepared and graded according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) method. A critical and scientific approach is required for the safe implementation of this new technology.