Developing a donation after cardiac death risk index for adult and pediatric liver transplantation

[Organ donation and organ assessment after primary circulatory death and secondary brain death]

BACKGROUND

The global organ shortage is the biggest obstacle to expand urgently needed liver transplantation activities. In addition to donation after brain death (DBD), donation after primary circulatory death (DCD) has also been introduced in many European countries to increase the number of donated organs.

OBJECTIVE

This article summarizes the legal and ethical aspects of DCD, the practical donation process of DCD, the clinical results of DCD liver transplantation with a special focus on organ assessment before a planned DCD liver transplantation.

RESULTS

In Europe 11 countries have active DCD liver transplantation programs and a total of 1230 DCD liver transplantations were performed in Europe in 2023. The highest proportion of DCD liver transplantations were recorded in Belgium (52.8%), the Netherlands (42.8%) and Switzerland (32.1%). The adequate selection of donors and recipients is crucial in DCD transplantation and the use of DCD livers particularly depends on the preparedness of the healthcare system for routine machine perfusion. The leaders are Belgium, France and Italy which implant around 68-74% of DCD organs. With an adequate organ assessment, the long-term results of DBD and DCD liver transplantations are comparable. To assess mitochondrial damage and thus organ quality, hypothermic oxygenated machine perfusion (HOPE) was introduced and has the secondary benefit of mitochondrial protection through oxygenation. The establishment of aerobic metabolism in mitochondria under hypothermia leads to a reduction of toxic metabolites and the restoration of ATP storage, which subsequently leads to a reperfusion light during implantation.

CONCLUSION

Expanding the donor pool with DCD donors can counteract the global organ shortage. With adequate patient selection and routine organ assessment short-term and also long-term outcomes of DBD and DCD liver transplantation are comparable.

Strategies to Improve the Utilization and Function of DCD Livers

Despite the increased usage of livers from donation after circulatory death (DCD) donors in the last decade, many patients remaining on the waitlist who need a liver transplant. Recent efforts have focused on maximizing the utilization and outcomes of these allografts using advances in machine perfusion technology and other perioperative strategies such as normothermic regional perfusion (NRP). In addition to the standard donor and recipient matching that is required with DCD donation, new data regarding the impact of graft steatosis, extensive European experience with NRP, and the increasing use of normothermic and hypothermic machine perfusion have shown immense potential in increasing DCD organ overall utilization and improved outcomes. These techniques, along with viability testing of extended criteria donors, have generated early promising data to consider the use of higher-risk donor organs and more widespread adoption of these techniques in the United States. This review explores the most recent international literature regarding strategies to optimize the utilization and outcomes of DCD liver allografts, including donor-recipient matching, perioperative strategies including NRP versus rapid controlled DCD recovery, viability assessment of discarded livers, and postoperative strategies including machine perfusion versus pharmacologic interventions.

DCD liver transplant in patients with a MELD over 35

Introduction

Donation after circulatory death (DCD) liver transplantation (LT) makes up well less than 1% of all LTs with a Model for End-Stage Liver Disease (MELD)≥35 in the United States. We hypothesized DCD-LT yields acceptable ischemia-reperfusion and reasonable outcomes for recipients with MELD≥35.

Methods

We analyzed recipients with lab-MELD≥35 at transplant within the UCSF (n=41) and the UNOS (n=375) cohorts using multivariate Cox regression and propensity score matching.

Results

In the UCSF cohort, five-year patient survival was 85% for DCD-LTs and 86% for matched-Donation after Brain Death donors-(DBD) LTs (p=0.843). Multivariate analyses showed that younger donor/recipient age and more recent transplants (2011-2021 versus 1999-2010) were associated with better survival. DCD vs. DBD graft use did not significantly impact survival (HR: 1.2, 95%CI 0.6-2.7). The transaminase peak was approximately doubled, indicating suggesting an increased ischemia-reperfusion hit. DCD-LTs had a median post-LT length of stay of 11 days, and 34% (14/41) were on dialysis at discharge versus 12 days and 22% (9/41) for DBD-LTs. 27% (11/41) DCD-LTs versus 12% (5/41) DBD-LTs developed a biliary complication (p=0.095). UNOS cohort analysis confirmed patient survival predictors, but DCD graft emerged as a risk factor (HR: 1.5, 95%CI 1.3-1.9) with five-year patient survival of 65% versus 75% for DBD-LTs (p=0.016). This difference became non-significant in a sub-analysis focusing on MELD 35-36 recipients. Analysis of MELD≥35 DCD recipients showed that donor age of <30yo independently reduced the risk of graft loss by 30% (HR, 95%CI: 0.7 (0.9-0.5), p=0.019). Retransplant status was associated with a doubled risk of adverse event (HR, 95%CI: 2.1 (1.4-3.3), p=0.001). The rejection rates at 1y were similar between DCD- and DBD-LTs, (9.3% (35/375) versus 1,541 (8.7% (1,541/17,677), respectively).

Discussion

In highly selected recipient/donor pair, DCD transplantation is feasible and can achieve comparable survival to DBD transplantation. Biliary complications occurred at the expected rates. In the absence of selection, DCD-LTs outcomes remain worse than those of DBD-LTs.

Comparison of Biliary Complications Rates After Brain Death, Donation After Circulatory Death, and Living-Donor Liver Transplantation: A Single-Center Cohort Study

Donation-after-circulatory-death (DCD), donation-after-brain-death (DBD), and living-donation (LD) are the three possible options for liver transplantation (LT), each with unique benefits and complication rates. We aimed to compare DCD-, DBD-, and LD-LT-specific graft survival and biliary complications (BC). We collected data on 138 DCD-, 3,027 DBD- and 318 LD-LTs adult recipients from a single center and analyzed patient/graft survival. BC (leak and anastomotic/non-anastomotic stricture (AS/NAS)) were analyzed in a subset of 414 patients. One-/five-year graft survival were 88.6%/70.0% for DCD-LT, 92.6%/79.9% for DBD-LT, and, 91.7%/82.9% for LD-LT. DCD-LTs had a 1.7-/1.3-fold adjusted risk of losing their graft compared to DBD-LT and LD-LT, respectively (p < 0.010/0.403). Bile leaks were present in 10.1% (DCD-LTs), 7.2% (DBD-LTs), and 36.2% (LD-LTs) (ORs, DBD/LD vs. DCD: 0.7/4.2, p = 0.402/<0.001). AS developed in 28.3% DCD-LTs, 18.1% DBD-LTs, and 43.5% LD-LTs (ORs, DBD/LD vs. DCD: 0.5/1.8, p = 0.018/0.006). NAS was present in 15.2% DCD-LTs, 1.4% DBDs-LT, and 4.3% LD-LTs (ORs, DBD/LD vs. DCD: 0.1/0.3, p = 0.001/0.005). LTs w/o BC had better liver graft survival compared to any other groups with BC. DCD-LT and LD-LT had excellent graft survival despite significantly higher BC rates compared to DBD-LT. DCD-LT represents a valid alternative whose importance should increase further with machine/perfusion systems.

Disparities in the Use of Older Donation After Circulatory Death Liver Allografts in the United States Versus the United Kingdom

BACKGROUND

This study aimed to assess the differences between the United States and the United Kingdom in the characteristics and posttransplant survival of patients who received donation after circulatory death (DCD) liver allografts from donors aged >60 y.

METHODS

Data were collected from the UK Transplant Registry and the United Network for Organ Sharing databases. Cohorts were dichotomized into donor age subgroups (donor >60 y [D >60]; donor ≤60 y [D ≤60]). Study period: January 1, 2001, to December 31, 2015.

RESULTS

1157 DCD LTs were performed in the United Kingdom versus 3394 in the United States. Only 13.8% of US DCD donors were aged >50 y, contrary to 44.3% in the United Kingdom. D >60 were 22.6% in the United Kingdom versus 2.4% in the United States. In the United Kingdom, 64.2% of D >60 clustered in 2 metropolitan centers. In the United States, there was marked inter-regional variation. A total of 78.3% of the US DCD allografts were used locally. One- and 5-y unadjusted DCD graft survival was higher in the United Kingdom versus the United States (87.3% versus 81.4%, and 78.0% versus 71.3%, respectively; P < 0.001). One- and 5-y D >60 graft survival was higher in the United Kingdom (87.3% versus 68.1%, and 77.9% versus 51.4%, United Kingdom versus United States, respectively; P < 0.001). In both groups, grafts from donors ≤30 y had the best survival. Survival was similar for donors aged 41 to 50 versus 51 to 60 in both cohorts.

CONCLUSIONS

Compared with the United Kingdom, older DCD LT utilization remained low in the United States, with worse D >60 survival. Nonetheless, present data indicate similar survivals for older donors aged ≤60, supporting an extension to the current US DCD age cutoff.

Donation after Circulatory Death Liver Transplantation in Paediatric Recipients

Waiting list mortality together, with limited availability of organs, are one of the major challenges in liver transplantation (LT). Especially in the paediatric population, another limiting factor is the scarcity of transplantable liver grafts due to additional concerns regarding graft size matching. In adults, donation after circulatory death (DCD) liver grafts have been used to expand the donor pool with satisfactory results. Although several studies suggest that DCD livers could also be used in paediatric recipients with good outcomes, their utilisation in children is still limited to a small number of reports. Novel organ perfusion strategies could be used to improve organ quality and help to increase the number of DCD grafts utilised for children. With the current manuscript, we present the available literature of LT using DCD grafts in paediatric recipients, discussing current challenges with the use of these livers in children and how machine perfusion technologies could be of impact in the future.

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 75^th-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.

Advantages and Limitations of Clinical Scores for Donation After Circulatory Death Liver Transplantation

Background: Scoring systems have been proposed to select donation after circulatory death (DCD) donors and recipients for liver transplantation (LT). We hypothesized that complex scoring systems derived in large datasets might not predict outcomes locally. Methods: Based on 1-year DCD-LT graft survival predictors in multivariate logistic regression models, we designed, validated, and compared a simple index using the University of California, San Francisco (UCSF) cohort (n = 136) and a universal-comprehensive (UC)-DCD score using the United Network for Organ Sharing (UNOS) cohort (n = 5,792) to previously published DCD scoring systems. Results: The total warm ischemia time (WIT)-index included donor WIT (dWIT) and hepatectomy time (dHep). The UC-DCD score included dWIT, dHep, recipient on mechanical ventilation, transjugular-intrahepatic-portosystemic-shunt, cause of liver disease, model for end-stage liver disease, body mass index, donor/recipient age, and cold ischemia time. In the UNOS cohort, the UC-score outperformed all previously published scores in predicting DCD-LT graft survival (AUC: 0.635 vs. ≤0.562). In the UCSF cohort, the total WIT index successfully stratified survival and biliary complications, whereas other scores did not. Conclusion: DCD risk scores generated in large cohorts provide general guidance for safe recipient/donor selection, but they must be tailored based on non-/partially-modifiable local circumstances to expand DCD utilization.

Ischemic Cholangiopathy Postdonation After Circulatory Death Liver Transplantation: Donor Hepatectomy Time Matters

Background.

Outcomes of liver transplantation (LT) from donation after circulatory death (DCD) have been improving; however, ischemic cholangiopathy (IC) continues to be a problem. In 2014, measures to minimize donor hepatectomy time (DHT) and cold ischemic time (CIT) have been adopted to improve DCD LT outcomes.

Methods.

Retrospective review of all patients who underwent DCD LT between 2005 and 2017 was performed. We compared outcomes of patients who were transplanted before 2014 (historic group) with those who were transplanted between 2014 and 2017 (modern group).

Results.

We identified 112 patients; 44 were in the historic group and 68 in the modern group. Donors in the historic group were younger (26.5 versus 33, P = 0.007) and had a lower body mass index (26.2 versus 28.2, P = 0.007). DHT (min) and CIT (h) were significantly longer in the historic group (21.5 versus 14, P < 0.001 and 5.3 versus 4.2, P < 0.001, respectively). Fourteen patients (12.5%) developed IC, with a significantly higher incidence in the historic group (23.3% versus 6.1%, P = 0.02). There was no difference in graft and patient survival between both groups.

Conclusion.

In appropriately selected recipients, minimization of DHT and CIT may decrease the incidence of IC. These changes can potentially expand the DCD donor pool.

Applicability of the UK DCD Risk Score in the modern era of liver transplantation: a U.S. update

Careful graft and recipient selection have resulted in improved outcomes in liver transplantation (LT) using donation after cardiac death (DCD) organs. The UK DCD Risk Score was established as a risk stratification tool to guide selection. We evaluated the applicability of the UK DCD Risk Score in a contemporary US cohort of adult DCD LT recipients using the United Network for Organ Sharing registry (2011-2020). 3,899 DCD LTs were included in our study (UK DCD Risk Score 0-5 points: 1,438 [36.9%], 6-9 points: 1,920 [49.2%]; 10-20 points: 541 [13.9%]). Compared to a score of 6-9 points, a score of 0-5 points was associated with decreased risk of graft loss (HR = 0.80, 95%CI: 0.68-0.94, P = 0.006), while a score of 10-20 points was associated with increased risk of graft loss (HR = 1.23, 95%CI: 1.01-1.51, P = 0.04). The 5-year graft survival for patients with risk scores of 0-5, 6-9, and 10-20 were 75.9%, 71.7%, and 67.9%, respectively. The C-statistic for the UK DCD Risk Score in our contemporary cohort was 0.611. The UK DCD Risk Score demonstrates a more limited ability to differentiate recipient outcomes in the modern era of DCD LT in the US. Acceptable long-term outcomes are achievable for patients stratified to the highest-risk group. This article is protected by copyright. All rights reserved.

Recommendations for Donor and Recipient Selection and Risk Prediction: Working Group Report From the ILTS Consensus Conference in DCD Liver Transplantation

Although the utilization of donation after circulatory death donors (DCDs) for liver transplantation (LT) has increased steadily, much controversy remains, and no common acceptance criteria exist with regard to donor and recipient risk factors and prediction models. A consensus conference was organized by International Liver Transplantation Society on January 31, 2020, in Venice, Italy, to review the current clinical practice worldwide regarding DCD-LT and to develop internationally accepted guidelines. The format of the conference was based on the grade system. International experts in this field were allocated to 6 working groups and prepared evidence-based recommendations to answer-specific questions considering the currently available literature. Working group members and conference attendees served as jury to edit and confirm the final recommendations presented at the end of the conference by each working group separately. This report presents the final statements and recommendations provided by working group 2, covering the entire spectrum of donor and recipient risk factors and prediction models in DCD-LT.

Early Allograft Dysfunction and Complications in DCD Liver Transplantation: Expert Consensus Statements From the International Liver Transplantation Society

Livers for transplantation from donation after circulatory death donors are relatively more prone to early and ongoing alterations in graft function that might ultimately lead to graft loss and even patient death. In consideration of this fact, this working group of the International Liver Transplantation Society has performed a critical evaluation of the medical literature to create a set of statements regarding the assessment of early allograft function/dysfunction and complications arising in the setting of donation after circulatory death liver transplantation.

Comparable graft survival is achievable with the usage of donation after circulatory death liver grafts from donors at or above 70 years of age: A long-term UK national analysis

The aim of the study was to assess the UK donation after circulatory death (DCD) liver transplant experience from donors ≥70 years. Nationwide UK DCD retrospective analysis was conducted between 2001 and 2015 (n = 1163). Recipients were divided into group 1 vs. group 2 (donors 70≥ vs. <70 years, respectively). group 1 (n = 69, 5.9%) recipients were older (median 59 vs. 55 years, p = .001) and had longer waitlist time (128 vs. 84 days; p = .039). 94.2% of group 1 clustered in London and Birmingham, where the two busiest centers are located. group 1 allografts had higher UKDRI and UK DCD Risk Scores but similar WIT and CIT and were more likely to have been imported. Both groups had similar 1-, 3-, and 5-year graft survival (group 1, 90%, 81.4%, and 74% vs. group 2, 88.6%, 81.4%, and 78.6%, respectively; p = .54). Both groups had similar ICU stay length (p = .22), 3-month hepatic artery thrombosis rates (4.4% vs 4.0%; p = .9), and 12-month readmission rates for all biliary complications (20.3% vs 25.7%; p = .32). This study demonstrates that acceptable outcomes are achievable using older grafts in a highly selected cohort at experienced centers. Advanced age should not be an absolute contraindication to utilizing a DCD graft from donors aged ≥70 years.

Donor Warm Ischemia Time in DCD Liver Transplantation-Working Group Report From the ILTS DCD, Liver Preservation, and Machine Perfusion Consensus Conference

Donation after circulatory death (DCD) grafts are commonly used in liver transplantation. Attributable to the additional ischemic event during the donor warm ischemia time (DWIT), DCD grafts carry an increased risk for severe ischemia/reperfusion injury and postoperative complications, such as ischemic cholangiopathy. The actual ischemia during DWIT depends on the course of vital parameters after withdrawal of life support and varies widely between donors. The ischemic period (functional DWIT) starts when either Spo2 or blood pressure drop below a certain point and lasts until the start of cold perfusion during organ retrieval. Over the years, multiple definitions and thresholds of functional DWIT duration have been used. The International Liver Transplantation Society organized a Consensus Conference on DCD, Liver Preservation, and Machine Perfusion on January 31, 2020 in Venice, Italy. The aim of this conference was to reach consensus about various aspects of DCD liver transplantation in context of currently available evidence. Here we present the recommendations with regards to the definitions used for DWIT and functional DWIT, the importance of vital parameters after withdrawal of life support, and acceptable thresholds of duration of functional DWIT to proceed with liver transplantation.

Donation after circulatory death liver transplantation: An in-depth analysis and propensity score-matched comparison

BACKGROUND

Careful donor-recipient matching and reduced ischemia times have improved outcomes following donation after circulatory death (DCD) liver transplantation (LT). This study examines a single-center experience with DCD LT including high-acuity and hospitalized recipients.

METHODS

DCD LT outcomes were compared to a propensity score-matched (PSM) donation after brain death (DBD) LT cohort (1:4); 32 DCD LT patients and 128 PSM DBD LT patients transplanted from 2008 to 2018 were included. Analyses included Kaplan-Meier estimates and Cox proportional hazards models examining patient and graft survival.

RESULTS

Median MELD score in the DCD LT cohort was 22, with median MELD of 27 for DCD LT recipients with decompensated cirrhosis. No difference in mortality or graft loss was found (p < .05) between DCD LT and PSM DBD LT at 3 years post-transplant, nor was DCD an independent risk factor for patient or graft survival. Post-LT severe acute kidney injury was similar in both groups. Ischemic-type biliary lesions (ITBL) occurred in 6.3% (n = 2) of DCD LT recipients, resulting in 1 graft loss and 1 death.

CONCLUSION

This study supports that DCD LT outcomes can be similar to DBD LT, with a low rate of ITBL, in a cohort including high-acuity recipients. Strict donor selection criteria, ischemia time minimization, and avoiding futile donor/recipient combinations are essential considerations.

Expanding Role of Donation After Circulatory Death Donors in Liver Transplantation

Better understanding of how to utilize donation after circulatory death (DCD) liver grafts has resulted in improved national outcomes and expansion in the number of DCD liver transplants (LTs). This improvement has been driven by better donor and recipient matching, careful evaluation of hemodynamics during withdrawal of life support, and refinement of the procurement operation. Changes to liver allocation likely will result in increased utilization of DCD liver grafts. Ischemic cholangiopathy remains the Achilles heel of DCD LTs and, although rates have fallen with improved protocols, a certain rate likely is unavoidable. This review discusses contemporary issues with DCD LTs.

Adult split liver transplantation: A PRISMA-compliant Chinese single-center retrospective case-control study

Although pediatric split liver transplantation (SLT) has been proven safe and the waitlist mortality rate has been successfully reduced, the safety of adult SLT has not been confirmed.Using 1:2 matching, 47 recipients who underwent adult SLT were matched to 94 of 743 recipients who underwent adult whole graft liver transplantation (WGLT). Eventually, 141 recipients were included in the case-control study. Subgroup analysis of 43 recipients in the SLT group was performed based on the presence of the middle hepatic vein (MHV) in the grafts.No significant differences in 5-year survival (80.8% vs 81.6%, P = .465) were observed between the adult SLT and WGLT groups. However, compared to recipients in the WGLT group, those in the SLT group had more Clavien-Dindo grade III-V complications, longer hospitalization duration, and higher mortality within 45 days. Furthermore, on multivariate analysis, 45-day postoperative mortality in recipients in the SLT group was mainly affected by hyperbilirubinemia within postoperative day (POD) 7-14, surgery time, and intraoperative blood loss. Subgroup analysis showed no significant differences in hyperbilirubinemia within POD 7-14, complications, and survival rate between SLTMHV(+) and SLTMHV [-].Adult SLT is safe and effective based on long-term survival rates; however, a reduction in the incidence of short-term complications is required. Non-obstructive hyperbilirubinemia within POD 7 to 14 is an independent predictor of short-term mortality after SLT.

Expedited placement to maximize utilization of marginal organs

PURPOSE OF REVIEW

Deceased donation represents the largest supply of organs for transplant in the United States. Organs with suboptimal characteristics related to donor disease or recovery-related issues are increasingly discarded at the time of recovery, prompting late allocation to candidates later in the match sequence. Late allocation contributes to organ injury by prolonging cold ischemia, which may further lead to the risk of organ discard, despite the potential to provide benefit to certain transplant candidates.

RECENT FINDINGS

Expedited placement of marginal organs has emerged as a strategy to address the growing problem of organ discard of marginal organs that have been declined late after recovery. In this review, we describe the basis for expedited organ placement, and approaches to facilitating placement of these grafts, drawing examples from kidney and liver donation and transplantation globally.

SUMMARY

There is significant global variation in practice related to late allocation. Multiple policy mechanisms exist to facilitate expedited placement, including simultaneous offers to multiple centers, predesignation of aggressive centers, and increasing organ procurement organization autonomy in late allocation. Optimizing late allocation of deceased donor organs holds significant promise to increase the number of transplants.

Livers From Pediatric Donation After Circulatory Death Donors Represent a Viable and Underutilized Source of Allograft

Despite increased numbers of donation after circulatory death (DCD) donors, pediatric DCD livers are underused. To investigate possible reasons for this discrepancy, we conducted a retrospective cohort study using 2 data sets from the Organ Procurement and Transplantation Network for all deceased liver donors and for all recipients of DCD liver transplants from March 8, 1993, to June 30, 2018. Pediatric (0-12 years) and adolescent (13-17 years) DCD donors were compared with those aged 18-40 years. We found that pediatric DCD allografts are recovered at a significantly lower rate than from 18-to-40-year-old donors (27.3% versus 56.3%; P < 0.001). However, once recovered, these organs are transplanted at a similar rate to those from the 18-to-40-year-old donor cohort (74.7% versus 74.2%). Significantly more pediatric DCD livers (odds ratio [OR], 3.75; confidence interval [CI], 3.14-4.47) were not recovered compared with adult organs, which were most commonly not recovered due to organ quality (10.2% versus 7.1%; P < 0.001). The 10-year relative risks (RRs) for graft failure and patient death were similar between pediatric and adult DCD donors, with adolescent DCD livers demonstrating improved outcomes. DCD livers transplanted into pediatric donors were protective against graft failure (RR, 0.46; 95% confidence interval [CI], 0.21-0.99) and patient death (RR, 0.16; 95% CI, 0.04-0.69). In conclusion, despite lower rates of recovery, pediatric DCD livers represent a viable organ source for certain adults and children.

Donation after Circulatory Death: Potential Mechanisms of Injury and Preventative Strategies

Donation after circulatory death (DCD) donors represent a potential means to help address the disparity between the number of patients awaiting liver transplantation (LT) and the availability of donor livers. While initial enthusiasm for DCD LT was high in the early 2000s, early reports of high rates of biliary complications and inferior graft survival resulted in reluctance among many transplant centers to use DCD liver grafts. As with all innovations in transplant practice, there is undoubtedly a learning curve associated with the optimal utilization of liver grafts from DCD donors. More contemporary data has demonstrated that results with DCD LT are improving and the number of DCD LT performed annually has been steadily increasing. In this concise review, potential mechanisms of injury for DCD livers are discussed along with strategies that have been employed in clinical practice to improve DCD LT outcomes.

Donation after circulatory death liver transplantation: consensus statements from the Spanish Liver Transplantation Society

Livers from donation after circulatory death (DCD) donors are an increasingly more common source of organs for transplantation. While there are few high-level studies in the field of DCD liver transplantation, clinical practice has undergone progressive changes during the past decade, in particular due to mounting use of postmortem normothermic regional perfusion (NRP). In Spain, uncontrolled DCD has been performed since the late 1980s/early 1990s, while controlled DCD was implemented nationally in 2012. Since 2012, the rise in DCD liver transplant activity in Spain has been considerable, and the great majority of DCD livers transplanted in Spain today are recovered with NRP. A panel of the Spanish Liver Transplantation Society was convened in 2018 to evaluate current evidence and accumulated experience in DCD liver transplantation, in particular addressing issues related to DCD liver evaluation, acceptance criteria, and recovery as well as recipient selection and postoperative management. This panel has created a series of consensus statements for the standard of practice in Spain and has published these statements with the hope they might help guide other groups interested in implementing new forms of DCD liver transplantation and/or introducing NRP into their clinical practices.

The Changing Landscapes in DCD Liver Transplantation

Purpose of Review

The transplant community continues to look for ways to help address the discordance between donor liver graft availability and patients on the liver transplant waiting list. Donation after circulatory death (DCD) donor livers represents one potential means to help address this discordance. The present review describes the changing landscape of DCD liver transplantation (LT).

Recent Findings

The number of DCD LTs performed annually within the USA has continued to grow on an annual basis. Importantly, national data has demonstrated that outcomes with DCD LT have been improving. This improvement has been driven by better understanding of how to successfully utilize these organs through better donor and recipient matching and careful evaluation of both hemodynamics during withdrawal of life support and the refinement of the procurement operation.

Summary

Despite these improvements in outcome, ischemic cholangiopathy (IC) continues to be the Achilles heel of DCD LT. Emerging technologies such as various forms of machine perfusion may allow for reduction of complications and better prognostication of the risk associated with DCD liver grafts.

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.

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.

The UK-DCD-Risk-Score - practical and new guidance for allocation of a specific organ to a recipient?

Introduction: Multiple factors contribute to the overall outcome in donation after circulatory death liver transplantation. The majority is however inconsistently reported with various acceptance criteria and thresholds, when to decline a specific graft. Recent improvement in outcome was based on an increased awareness of the cumulative risk, combining donor and recipient parameters, which encouraged the community to accept livers with an overall higher risk. Areas covered: This review pictures the large number of risk factors in this field with a special focus on parameters, which contribute to available prediction models. Next, features of the recently developed UK-DCD-Risk-Score, which led to a significantly impaired graft survival, above a suggested threshold of >10 score points, are discussed. The clinical impact of this new model on the background of other prediction tools with their subsequent limitations is highlighted in a next chapter. Finally, we provide suggestions, how to further improve outcomes in this challenging field of transplantation. Expert opinion: Despite the recent development of new prediction models, including the UK-DCD-Risk-Score, which provides a sufficient prediction of graft loss after DCD liver transplantation, the consideration of other confounders is essential to better understand the overall risk and metabolic liver status to improve the comparability of clinical studies. More uniform definitions and thresholds of individual risk factors are required.

Normothermic Machine Perfusion (NMP) Inhibits Proinflammatory Responses in the Liver and Promotes Regeneration

Liver transplantation (LT) is a successful treatment for patients with liver failure. However, organ shortage results in over 11% of patients losing their chance of a transplant attributed to liver decompensation (LD) and death. Ischemia/reperfusion injury (IRI) following conventional cold storage (CS) is a major cause of injury leading to graft loss after LT. Normothermic machine perfusion (NMP), a method of organ preservation, provides oxygen and nutrition during preservation and allows aerobic metabolism. NMP has recently been shown to enable improved organ utilization and posttransplant outcomes following a phase I and a phase III randomized trial. The aim of the present study is to assess the impact of NMP on reducing IRI and to define the underlying mechanisms. We transplanted and compared 12 NMP with 27 CS-preserved livers by performing gene microarray, immunoprofiling of hepatic lymphocytes, and immunochemistry staining of liver tissues for assessing necrosis, platelet deposition, and neutrophil infiltration, and the status of steatosis after NMP or CS prereperfusion and postreperfusion. Recipients receiving NMP grafts showed significantly lower peak aspartate aminotransferase (AST) levels than those receiving CS grafts. NMP altered gene-expression profiles of liver tissue from proinflammation to prohealing and regeneration. NMP also reduced the number of interferon gamma (IFN-γ) and interleukin (IL)-17-producing T cells and enlarged the CD4^pos CD25^high CD127^neg FOXP3^pos regulatory T cell (Treg) pool. NMP liver tissues showed less necrosis and apoptosis in the parenchyma and fewer neutrophil infiltration compared to CS liver tissues. Conclusion: Reduced IRI in NMP recipients was the consequence of the combination of inhibiting inflammation and promoting graft regeneration.

Retrieval Practice or Overall Donor and Recipient Risk: What Impacts on Outcomes After Donation After Circulatory Death Liver Transplantation in the United Kingdom?

Parameters of retrieval surgery are meticulously documented in the United Kingdom, where up to 40% of livers are donation after circulatory death (DCD) donations. This retrospective analysis focuses on outcomes after transplantation of DCD livers, retrieved by different UK centers between 2011 and 2016. Donor and recipient risk factors and the donor retrieval technique were assessed. A total of 236 DCD livers from 9 retrieval centers with a median UK DCD risk score of 5 (low risk) to 7 points (high risk) were compared. The majority used University of Wisconsin solution for aortic flush with a median hepatectomy time of 27-44 minutes. The overall liver injury rate appeared relatively high (27.1%) with an observed tendency toward more retrieval injuries from centers performing a quicker hepatectomy. Among all included risk factors, the UK DCD risk score remained the best predictor for overall graft loss in the multivariate analysis (P < 0.001). In high-risk and futile donor-recipient combinations, the occurrence of liver retrieval injuries had negative impact on graft survival (P = 0.023). Expectedly, more ischemic cholangiopathies (P = 0.003) were found in livers transplanted with a higher cumulative donor-recipient risk. Although more biliary complications with subsequent graft loss were found in high-risk donor-recipient combinations, the impact of the standardized national retrieval practice on outcomes after DCD liver transplantation was minimal.

Warm ischemia time and elevated serum uric acid are associated with metabolic syndrome after liver transplantation with donation after cardiac death

AIM

To describe the prevalence of posttransplant metabolic syndrome (PTMS) after donation after cardiac death (DCD) liver transplantation (LT) and the pre- and postoperative risk factors.

METHODS

One hundred and forty-seven subjects who underwent DCD LT from January 2012 to February 2016 were enrolled in this study. The demographics and the clinical characteristics of pre- and post-transplantation were collected for both recipients and donors. PTMS was defined according to the 2004 Adult Treatment Panel-III criteria. All subjects were followed monthly for the initial 6 mo after discharge, and then, every 3 mo for 2 years. The subjects were followed every 6 mo or as required after 2 years post-LT.

RESULTS

The prevalence of PTMS after DCD donor orthotopic LT was 20/147 (13.6%). Recipient’s body mass index (P = 0.024), warm ischemia time (WIT) (P = 0.045), and posttransplant hyperuricemia (P = 0.001) were significantly associated with PTMS. The change in serum uric acid levels in PTMS patients was significantly higher than that in non-PTMS patients (P < 0.001). After the 1^st mo, the level of serum uric acid of PTMS patients rose continually over a period, while it was unaltered in non-PTMS patients. After transplantation, the level of serum uric acid in PTMS patients was not associated with renal function.

CONCLUSION

PTMS could occur at early stage after DCD LT with growing morbidity with the passage of time. WIT and post-LT hyperuricemia are associated with the prevalence of PTMS. An increased serum uric acid level is highly associated with PTMS and could act as a serum marker in this disease.

Impact of Machine Perfusion on Biliary Complications after Liver Transplantation

We describe in this review the different types of injuries caused to the biliary tree after liver transplantation. Furthermore, we explain underlying mechanisms and why oxygenated perfusion concepts could not only protect livers, but also repair high-risk grafts to prevent severe biliary complications and graft loss. Accordingly, we summarize experimental studies and clinical applications of machine liver perfusion with a focus on biliary complications after liver transplantation. Key points: (1) Acute inflammation with subsequent chronic ongoing liver inflammation and injury are the main triggers for cholangiocyte injury and biliary tree transformation, including non-anastomotic strictures; (2) Hypothermic oxygenated perfusion (HOPE) protects livers from initial oxidative injury at normothermic reperfusion after liver transplantation. This is a unique feature of a cold oxygenation approach, which is effective also end-ischemically, e.g., after cold storage, due to mitochondrial repair mechanisms. In contrast, normothermic oxygenated perfusion concepts protect by reducing cold ischemia, and are therefore most beneficial when applied instead of cold storage; (3) Due to less downstream activation of cholangiocytes, hypothermic oxygenated perfusion also significantly reduces the development of biliary strictures after liver transplantation.

Prediction of rat liver transplantation outcomes using energy metabolites measured by microdialysis

BACKGROUND

Warm ischemia jeopardizes graft quality and recipient survival in donation after cardiac death (DCD) transplantation. Currently, there is no system to objectively evaluate the liver quality from DCD. The present study tried to use energy metabolites to evaluate the donor liver quality.

METHODS

We divided 195 Sprague-Dawley rats into five groups: the control (n = 39), warm ischemic time (WIT) 15 min (n = 39), WIT 30 min (n = 39), WIT 45 min (n = 39), and WIT 60 min (n = 39) groups. Three rats from each group were randomly selected for pretransplant histologic evaluation of warm ischemia-related damage. The remaining 36 rats were randomly divided into donors and recipients of 18 liver transplantations, and were subjected to postoperative liver function and survival analyses. Between cardiac arrest and cold storage, liver energy metabolites including glucose, lactate, pyruvate, and glycerol were measured by microdialysis. The lactate to pyruvate ratio (LPR) was calculated.

RESULTS

The changes in preoperative pathology with warm ischemia were inconspicuous, but the trends in postoperative pathology and aminotransferase levels were consistent with preoperative energy metabolite measurements. The 30-day survival rates of the control and WIT 15, 30, 45, and 60 min groups were 100%, 81.82%, 76.92%, 58.33%, and 25.00%, respectively. The areas under the receiver operating characteristic curves of glucose, lactate, glycerol, and LPR were 0.87, 0.88, 0.88, and 0.92, respectively.

CONCLUSION

Glucose, lactate, glycerol, and LPR are predictors of graft quality and survival outcomes in DCD transplantation.

The UK DCD Risk Score: A new proposal to define futility in donation-after-circulatory-death liver transplantation

BACKGROUND & AIMS

Primary non-function and ischaemic cholangiopathy are the most feared complications following donation-after-circulatory-death (DCD) liver transplantation. The aim of this study was to design a new score on risk assessment in liver-transplantation DCD based on donor-and-recipient parameters.

METHODS

Using the UK national DCD database, a risk analysis was performed in adult recipients of DCD liver grafts in the UK between 2000 and 2015 (n = 1,153). A new risk score was calculated (UK DCD Risk Score) on the basis of a regression analysis. This is validated using the United Network for Organ Sharing database (n = 1,617) and our own DCD liver-transplant database (n = 315). Finally, the new score was compared with two other available prediction systems: the DCD risk scores from the University of California, Los Angeles and King's College Hospital, London.

RESULTS

The following seven strongest predictors of DCD graft survival were identified: functional donor warm ischaemia, cold ischaemia, recipient model for end-stage liver disease, recipient age, donor age, previous orthotopic liver transplantation, and donor body mass index. A combination of these risk factors (UK DCD risk model) stratified the best recipients in terms of graft survival in the entire UK DCD database, as well as in the United Network for Organ Sharing and in our own DCD population. Importantly, the UK DCD Risk Score significantly predicted graft loss caused by primary non-function or ischaemic cholangiopathy in the futile group (>10 score points). The new prediction model demonstrated a better C statistic of 0.79 compared to the two other available systems (0.71 and 0.64, respectively).

CONCLUSIONS

The UK DCD Risk Score is a reliable tool to detect high-risk and futile combinations of donor-and-recipient factors in DCD liver transplantation. It is simple to use and offers a great potential for making better decisions on which DCD graft should be rejected or may benefit from functional assessment and further optimization by machine perfusion.

LAY SUMMARY

In this study, we provide a new prediction model for graft loss in donation-after-circulatory-death (DCD) liver transplantation. Based on UK national data, the new UK DCD Risk Score involves the following seven clinically relevant risk factors: donor age, donor body mass index, functional donor warm ischaemia, cold storage, recipient age, recipient laboratory model for end-stage liver disease, and retransplantation. Three risk classes were defined: low risk (0-5 points), high risk (6-10 points), and futile (>10 points). This new model stratified best in terms of graft survival compared to other available models. Futile combinations (>10 points) achieved an only very limited 1- and 5-year graft survival of 37% and less than 20%, respectively. In contrast, an excellent graft survival has been shown in low-risk combinations (≤5 points). The new model is easy to calculate at the time of liver acceptance. It may help to decide which risk combination will benefit from additional graft treatment, or which DCD liver should be declined for a certain recipient.