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

British Transplantation Society guidelines on abdominal organ transplantation from deceased donors after circulatory death

The British Transplantation Society (BTS) 'Guideline on transplantation from deceased donors after circulatory death' has recently been updated and this manuscript summarises the relevant recommendations in abdominal organ transplantation from Donation after Circulatory Death (DCD) donors, encompassing the chapters on liver, kidney, pancreas and islet cell transplantation.

Machine Perfusion for Extended Criteria Donor Livers: What Challenges Remain?

Based on the renaissance of dynamic preservation techniques, extended criteria donor (ECD) livers reclaimed a valuable eligibility in the transplantable organ pool. Being more vulnerable to ischemia, ECD livers carry an increased risk of early allograft dysfunction, primary non-function and biliary complications and, hence, unveiled the limitations of static cold storage (SCS). There is growing evidence that dynamic preservation techniques—dissimilar to SCS—mitigate reperfusion injury by reconditioning organs prior transplantation and therefore represent a useful platform to assess viability. Yet, a debate is ongoing about the advantages and disadvantages of different perfusion strategies and their best possible applications for specific categories of marginal livers, including organs from donors after circulatory death (DCD) and brain death (DBD) with extended criteria, split livers and steatotic grafts. This review critically discusses the current clinical spectrum of livers from ECD donors together with the various challenges and posttransplant outcomes in the context of standard cold storage preservation. Based on this, the potential role of machine perfusion techniques is highlighted next. Finally, future perspectives focusing on how to achieve higher utilization rates of the available donor pool are highlighted.

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.

Temporal Trends in Utilization and Outcomes of DCD Livers in the United States

BACKGROUND

Historically, donation after circulatory death (DCD) livers were frequently discarded because of higher mortality and graft loss after liver transplantation (LT). However, the demand for LT continues to outstrip the supply of "acceptable" organs. Additionally, changes in the donor pool, organ allocation, and clinical management of donors and recipients, and improved clinical protocols might have altered post-DCD-LT outcomes.

METHODS

We studied 5975 recovered DCD livers using US Scientific Registry of Transplant Recipients data from 2005 to 2017, with a comparison group of 78 235 adult donation after brain death (DBD) livers recovered during the same time period. We quantified temporal trends in discard using adjusted multilevel logistic regression and temporal trends in post-LT mortality and graft loss for DCD LT recipients using adjusted Cox regression.

RESULTS

DCD livers were more likely to be discarded than DBD livers across the entire study period, and the relative likelihood of discard increased over time (adjusted odds ratio [aOR] of discard DCD versus DBD 3.854.455.14 2005-2007, 5.225.876.59 2015-2017) despite improving outcomes after DCD LT. Mortality risk for DCD LTs decreased in each time period (compared with 2005-2007, aHR 2008-2011 0.720.840.97, aHR 2012-2014 0.480.580.70, aHR 2015-2017 0.340.430.55), as did risk of graft loss (compared with 2005-2007, aHR 2008-2011 0.690.810.94, aHR 2012-2014 0.450.550.67, aHR 2015-2017 0.360.450.56).

CONCLUSIONS

Despite dramatic improvements in outcomes of DCD LT recipients, DCD livers remain substantially more likely to be discarded than DBD livers, and this discrepancy has actually increased over time. DCD livers are underutilized and have the potential to expand the donor pool.

Antemortem Heparin in Organ Donation After Circulatory Death Determination: A Systematic Review of the Literature

Donation after circulatory death determination frequently involves antemortem heparin administration to mitigate peri-arrest microvascular thrombosis. We systematically reviewed the literature to: (1) describe heparin administration practices and (2) explore the effects on transplant outcomes. We searched MEDLINE and EMBASE for studies reporting donation after circulatory death determination heparin practices including use, dosage, and timing (objective 1). To explore associations between antemortem heparin and transplant outcomes (objective 2), we (1) summarized within-study comparisons and (2) used meta-regression analyses to examine associations between proportions of donors that received heparin and transplant outcomes. We assessed risk of bias using the Newcastle Ottawa Scale and applied the GRADE methodology to determine certainty in the evidence. For objective 1, among 55 eligible studies, 48 reported heparin administration to at least some donors (range: 15.8%-100%) at variable doses (up to 1000 units/kg) and times relative to withdrawal of life-sustaining therapy. For objective 2, 7 studies that directly compared liver transplants with and without antemortem heparin reported lower rates of primary nonfunction, hepatic artery thrombosis, graft failure at 5 y, or recipient mortality (low certainty of evidence). In contrast, meta-regression analysis of 32 liver transplant studies detected no associations between the proportion of donors that received heparin and rates of early allograft dysfunction, primary nonfunction, hepatic artery thrombosis, biliary ischemia, graft failure, retransplantation, or patient survival (very low certainty of evidence). In conclusion, antemortem heparin practices vary substantially with an uncertain effect on transplant outcomes. Given the controversies surrounding antemortem heparin, clinical trials may be warranted.

A systematic review and meta-analyses of regional perfusion in donation after circulatory death solid organ transplantation

In donation after circulatory death (DCD), (thoraco)abdominal regional perfusion (RP) restores circulation to a region of the body following death declaration. We systematically reviewed outcomes of solid organ transplantation after RP by searching PubMed, Embase, and Cochrane libraries. Eighty-eight articles reporting on outcomes of liver, kidney, pancreas, heart, and lung transplants or donor/organ utilization were identified. Meta-analyses were conducted when possible. Methodological quality was assessed using National Institutes of Health (NIH)-scoring tools. Case reports (13/88), case series (44/88), retrospective cohort studies (35/88), retrospective matched cohort studies (5/88), and case-control studies (2/88) were identified, with overall fair quality. As blood viscosity and rheology change below 20 °C, studies were grouped as hypothermic (HRP, ≤20 °C) or normothermic (NRP, >20 °C) regional perfusion. Data demonstrate that RP is a safe alternative to in situ cold preservation (ISP) in uncontrolled and controlled DCDs. The scarce HRP data are from before 2005. NRP appears to reduce post-transplant complications, especially biliary complications in controlled DCD livers, compared with ISP. Comparisons for kidney and pancreas with ISP are needed but there is no evidence that NRP is detrimental. Additional data on NRP in thoracic organs are needed. Whether RP increases donor or organ utilization needs further research.

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.

Regulations and Procurement Surgery in DCD Liver Transplantation: Expert Consensus Guidance From the International Liver Transplantation Society

Donation after circulatory death (DCD) donors are an increasingly more common source of livers for transplantation in many parts of the world. Events that occur during DCD liver recovery have a significant impact on the success of subsequent transplantation. This working group of the International Liver Transplantation Society evaluated current evidence as well as combined experience and created this guidance on DCD liver procurement. Best practices for the recovery and transplantation of livers arising through DCD after euthanasia and organ procurement with super-rapid cold preservation and recovery as well as postmortem normothermic regional perfusion are described, as are the use of adjuncts during DCD liver procurement.

Donation after circulatory death and liver transplantation: a cohort study

Donations after circulatory death (DCD) are still challenging in Italy because of prolonged ischemia time (tWIT) due to the law and logistical issues. This cohort study was primarily aimed at assessing the association between successful transplantation and DCD types in the North Italy Transplant program. Adjusted risk ratios (RR) and 95% confidence intervals (CIs) for type III versus type II DCD were estimated using a Poisson regression model with a robust error variance. All consecutive DCD between 2008 and 2020 were included. Among 142 DCD, 102 were eligible for liver donation, and 96 were proposed: 68/69 (99%) and 28/33 (85%) type III and II DCD, respectively. Sixty-nine livers were recovered, 51/68 (75%) from type III and 18/28 (64%) from type II DCD, respectively (RR: 1.18; 95% CI: 0.87-1.60). After ex-vivo perfusion, 50/68 (74%) and 14/28 (50%) livers from type III and type II DCD were transplanted (RR: 1.49; 95% CI: 1.01-2.19). The estimate decreased after further controlling for tWIT (RR: 1.11; 95% CI: 0.55-2.24). Five patients (7.8%) experienced a PNF, 3/50 and 2/14 from type III and type II DCD, respectively. Type III DCD livers were more likely to be transplanted than type II. Warm ischemia time might explain this difference.

Wide Variation in the Percentage of Donation After Circulatory Death Donors Across Donor Service Areas: A Potential Target for Improvement

BACKGROUND

Substantial differences exist in the clinical characteristics of donors across the 58 donor service areas (DSAs). Organ procurement organization (OPO) performance metrics incorporate organs donated after circulatory determination of death (DCDD) donors but do not measure potential DCDD donors.

METHODS

Using 2011-2016 United Network for Organ Sharing data, we examined the variability in DCDD donors/all deceased donors (%DCDD) across DSAs. We supplemented United Network for Organ Sharing data with CDC death records and OPO statistics to characterize underlying process and system factors that may correlate with donors and utilization.

RESULTS

Among 52 184 deceased donors, the %DCDD varied widely across DSAs, with a median of 15.1% (interquartile range [9.3%, 20.9%]; range 0.0%-32.0%). The %DCDD had a modest positive correlation with 4 DSA factors: median match model for end-stage liver disease, proportion of white deaths out of total deaths, kidney center competition, and %DCDD livers by a local transplant center (all Spearman coefficients 0.289-0.464), and negative correlation with 1 factor: mean kidney waiting time (Spearman coefficient -0.388). Adjusting for correlated variables in linear regression explained 46.3% of the variability in %DCDD.

CONCLUSIONS

Donor pool demographics, waitlist metrics, center competition, and DCDD utilization explain only a portion of the variability of DCDD donors. This requires further studies and policy changes to encourage consideration of all possible organ donors.

Heme oxygenase-1-modified bone marrow mesenchymal stem cells combined with normothermic machine perfusion to protect donation after circulatory death liver grafts

BACKGROUND

Donation after circulatory death (DCD) liver grafts have a poor prognosis after transplantation. We investigated whether the outcome of DCD donor organs can be improved by heme oxygenase 1 (HO-1)-modified bone marrow-derived mesenchymal stem cells (BMMSCs) combined with normothermic machine perfusion (NMP), and explored its underlying mechanisms.

METHODS

BMMSCs were isolated, cultured, and transduced with the HO-1 gene. An NMP system was established. DCD rat livers were obtained, preserved by different methods, and the recipients were divided into 5 groups: sham operation, static cold storage (SCS), NMP, BMMSCs combined with NMP, and HO-1/BMMSCs combined with NMP (HBP) groups. Rats were sacrificed at 1, 7, and 14 days after surgery; their blood and liver tissue samples were collected; and liver enzyme and cytokine levels, liver histology, high-mobility group box 1 (HMGB1) levels in monocytes and liver tissues, and expression of Toll-like receptor 4 (TLR4) pathway-related molecules were evaluated.

RESULTS

After liver transplantation, the SCS group showed significantly increased transaminase levels, liver tissue damage, and shorter survival time. The HBP group showed lower transaminase levels, intact liver morphology, prolonged survival time, and decreased serum and liver proinflammatory cytokine levels. In the NMP and SCS groups, HMGB1 expression in the serum, monocytes, and liver tissues and TLR4 pathway-related molecule expression were significantly decreased.

CONCLUSIONS

HO-1/BMMSCs combined with NMP exerted protective effects on DCD donor liver and significantly improved recipient prognosis. The effect of HO-1/BMMSCs was greater than that of BMMSCs and was mediated via HMGB1 expression and TLR4 pathway inhibition.

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.