A critical analysis of liver allograft utilization from the US deceased donor pool

Pediatric discard risk index for predicting pediatric liver allograft discard

BACKGROUND

Of the 600 pediatric candidates added to the liver waiting list annually, 100 will remain waiting while over 100 liver allografts are discarded, often for subjective reasons.

METHODS

We created a risk index to predict discard to better optimize donor supply. We used the UNOS database to retrospectively analyze 17 367 deceased donors (≤18 years old) through univariate and multivariate logistic regression models. Deceased donor clinical characteristics and laboratory values were independent variables with discard being the dependent variable in the analysis. Significant univariate factors (P-value < .05) comprised the multivariate analysis. Significant variables from the multivariate analysis were incorporated into the pDSRI, producing a risk score for discard.

RESULTS

From 17 potential factors, 11 were identified as significant predictors (P < .05) of pediatric liver allograft discard. The most significant risk factors were as follows: DCD; total bilirubin >10 mg/dL, and alanine transaminase (ALT) ≥500 IU/L. The pDSRI has a C-statistic of 0.846 for the training set and 0.840 for the validation set.

CONCLUSION

The pDSRI uses 11 significant risk factors, including elevated liver function tests, donor demographics, and donor risk/type to accurately predict risk of pediatric liver allograft discard and serve as a tool that may maximize donor yield.

The Delivery of Multipotent Adult Progenitor Cells to Extended Criteria Human Donor Livers Using Normothermic Machine Perfusion

Background: Pre-clinical research with multi-potent adult progenitor cells (MAPC® cells, Multistem, Athersys Inc., Cleveland, Ohio) suggests their potential as an anti-inflammatory and immunomodulatory therapy in organ transplantation. Normothermic machine perfusion of the liver (NMP-L) has been proposed as a way of introducing therapeutic agents into the donor organ. Delivery of cellular therapy to human donor livers using this technique has not yet been described in the literature. The primary objectives of this study were to develop a technique for delivering cellular therapy to human donor livers using NMP-L and demonstrate engraftment. Methods: Six discarded human livers were perfused for 6 h at 37°C using the Liver Assist (Organ Assist, Groningen). 50 × 106 CMPTX-labeled MAPC cells were infused directly into the right lobe via the hepatic artery (HA, n = 3) or portal vein (PV, n = 3) over 20 min at different time points during the perfusion. Perfusion parameters were recorded and central and peripheral biopsies were taken at multiple time-points from both lobes and subjected to standard histological stains and confocal microscopy. Perfusate was analyzed using a 35-plex multiplex assay and proteomic analysis. Results: There was no detrimental effect on perfusion flow parameters on infusion of MAPC cells by either route. Three out of six livers met established criteria for organ viability. Confocal microscopy demonstrated engraftment of MAPC cells across vascular endothelium when perfused via the artery. 35-plex multiplex analysis of perfusate yielded 13 positive targets, 9 of which appeared to be related to the infusion of MAPC cells (including Interleukin's 1b, 4, 5, 6, 8, 10, MCP-1, GM-CSF, SDF-1a). Proteomic analysis revealed 295 unique proteins in the perfusate from time-points following the infusion of cellular therapy, many of which have strong links to MAPC cells and mesenchymal stem cells in the literature. Functional enrichment analysis demonstrated their immunomodulatory potential. Conclusion: We have demonstrated that cells can be delivered directly to the target organ, prior to host immune cell population exposure and without compromising the perfusion. Transendothelial migration occurs following arterial infusion. MAPC cells appear to secrete a host of soluble factors that would have anti-inflammatory and immunomodulatory benefits in a human model of liver transplantation.

Can reporting more lead to less? The role of metrics in assessing liver transplant program performance

Appropriate metrics for performance analysis is an active topic of debate within the transplant community. This study explores current proposals on metric expansion as well as potential metrics and prospective collaborations that have not received widespread discussion within the transplant community. The premature introduction of additional, nonvalidated metrics risks behaviors that may undermine donor utilization and patient access to transplantation.

A preliminary European Liver and Intestine Transplant Association-European Liver Transplant Registry study on informed recipient consent and extended criteria liver donation

The European Liver and Intestine Transplant Association (ELITA) and the European Liver Transplant Registry (ELTR) coordinated the distribution to European liver transplantation centers of an electronic questionnaire, developed by the first author, concerning the definition of extended criteria liver donation (ECD) and the implication for informed consent of transplant recipients. Completed questionnaires were received from 35 centers. All centers accepted ECD liver donors. The criteria for defining a liver donor as ECD were as follows: steatosis in 33 centers (94%); age up to 80 years in 15 centers (43%); serum sodium >165 mmol/L in 25 centers (71%); intensive care unit (ICU) stay with ventilation longer than 7 days in 17 centers (48%); aspartate aminotransferase (AST) >90 U/L, in 6 centers (17%); body mass index (BMI) >30 in 19 centers (54%); alanine aminotransferase (ALT) >105 U/L in 8 centers (23%); serum bilirubin >3 mg/dL in 15 centers (43%); and all criteria together in 2 centers (6%). Thirty-one centers informed the transplantation candidate of the ECD status of the donor, 20 (65%) when the patient registered for transplantation, 1 (3%) when an ECD liver became available, and 10 centers (32%) on both occasions. Thirteen centers required the liver transplantation candidate to sign a special consent form. Twenty centers informed the potential recipient of the donor's serology. Only 6 centers informed the potential recipient of any high-risk behavior of the donor.

Postoperative care/critical care of the transplant patient

Critical care of the general surgical patient requires synthesis of the patient's physiology, intraoperative events, and preexisting comorbidities. Evaluating an abdominal solid-organ transplant recipient after surgery adds a new dimension to clinical decisions because the transplanted allograft has undergone its own physiologic challenges and now must adapt to a new environment. This donor-recipient interaction forms the foundation for assessment of early allograft function (EAF). The intensivist must accurately assess and support EAF within the context of the recipient's current physiology and preexisting comorbidities. Optimizing EAF is essential because allograft failure is a significant predictor of recipient morbidity and mortality.

Expedited liver allocation in the United States: a critical analysis

The fate of donor livers allocated via an out-of-sequence expedited placement (EP) pathway has not been previously examined. We determined the originating and receiving United Network for Organ Sharing (UNOS) regions of all donor livers procured between January 1, 2010 and October 31, 2012 and placed out of sequence with UNOS bypass code 863 (EP attempt) or 898 (miscellaneous). We reviewed the early function of these liver grafts and assessed the effect of EP allocation on wait-listed patients at our center. Registrants at our center were eligible to receive 1298 liver offers during the interval studied: 218 (16.8%) of these liver offers bypassed our center and were allocated to other centers and used in patients lower on the match-run list. During the study interval, 560 livers were allocated in the United States by EP. Regions 1, 5, 7, 9, and 10 used the greatest number of EP-placed grafts. Region 1 (New England) used the greatest proportion of all EP livers (33% of all imported EP livers in the United States, P < 0.001 versus all other regions). Graft function data were available for 560 livers placed by EP: 491 (88%) of these grafts were functioning at a mean of 399.5 days after transplantation. In conclusion, the transplantation of livers allocated by means of an expedited refusal code is asymmetric across regions and, in some instances, results in the bypassing of patients with higher wait-list priority but without notification of the bypassed center. Short-term graft function after EP allocation is excellent. Policies governing EP allocation should be created in order to improve access to available organs.

Donor-recipient matching: myths and realities

Liver transplant outcomes keep improving, with refinements of surgical technique, immunosuppression and post-transplant care. However, these excellent results and the limited number of organs available have led to an increasing number of potential recipients with end-stage liver disease worldwide. Deaths on waiting lists have led liver transplant teams maximize every organ offered and used in terms of pre and post-transplant benefit. Donor-recipient (D-R) matching could be defined as the technique to check D-R pairs adequately associated by the presence of the constituents of some patterns from donor and patient variables. D-R matching has been strongly analysed and policies in donor allocation have tried to maximize organ utilization whilst still protecting individual interests. However, D-R matching has been written through trial and error and the development of each new score has been followed by strong discrepancies and controversies. Current allocation systems are based on isolated or combined donor or recipient characteristics. This review intends to analyze current knowledge about D-R matching methods, focusing on three main categories: patient-based policies, donor-based policies and combined donor-recipient systems. All of them lay on three mainstays that support three different concepts of D-R matching: prioritarianism (favouring the worst-off), utilitarianism (maximising total benefit) and social benefit (cost-effectiveness). All of them, with their pros and cons, offer an exciting controversial topic to be discussed. All of them together define D-R matching today, turning into myth what we considered a reality in the past.

Liver transplant using donors after cardiac death: a single-center approach providing outcomes comparable to donation after brain death

OBJECTIVES

Organ donation after cardiac death remains an available resource to meet the demand for transplant. However, concern persists that outcomes associated with donation after cardiac death liver allografts are not equivalent to those obtained with organ donation after brain death. The aim of this matched case control study was to determine if outcomes of liver transplants with donation after cardiac death donors is equivalent to outcomes with donation after brain death donors by controlling for careful donor and recipient selection, surgical technique, and preservation solution.

MATERIALS AND METHODS

A retrospective, matched case control study of adult liver transplant recipients at the University of Tennessee/Methodist University Hospital Transplant Institute, Memphis, Tennessee was performed. Thirty-eight donation after cardiac death recipients were matched 1:2, with 76 donation after brain death recipients by recipient age, recipient laboratory Model for End Stage Liver Disease score, and donor age to form the 2 groups. A comprehensive approach that controlled for careful donor and recipient matching, surgical technique, and preservation solution was used to minimize warm ischemia time, cold ischemia time, and ischemia-reperfusion injury.

RESULTS

Patient and graft survival rates were similar in both groups at 1 and 3 years (P = .444 and P = .295). There was no statistically significant difference in primary nonfunction, vascular complications, or biliary complications. In particular, there was no statistically significant difference in ischemic-type diffuse intrahepatic strictures (P = .107).

CONCLUSIONS

These findings provide further evidence that excellent patient and graft survival rates expected with liver transplants using organ donation after brain death donors can be achieved with organ donation after cardiac death donors without statistically higher rates of morbidity or mortality when a comprehensive approach that controls for careful donor and recipient matching, surgical technique, and preservation solution is used.

Development of organ-specific donor risk indices

Because of the shortage of deceased donor organs, transplant centers accept organs from marginal deceased donors, including older donors. Organ-specific donor risk indices have been developed to predict graft survival with various combinations of donor and recipient characteristics. Here we review the kidney donor risk index (KDRI) and the liver donor risk index (LDRI) and compare and contrast their strengths, limitations, and potential uses. The KDRI has a potential role in developing new kidney allocation algorithms. The LDRI allows a greater appreciation of the importance of donor factors, particularly for hepatitis C virus-positive recipients; as the donor risk index increases, the rates of allograft and patient survival among these recipients decrease disproportionately. The use of livers with high donor risk indices is associated with increased hospital costs that are independent of recipient risk factors, and the transplantation of livers with high donor risk indices into patients with Model for End-Stage Liver Disease scores < 15 is associated with lower allograft survival; the use of the LDRI has limited this practice. Significant regional variations in donor quality, as measured by the LDRI, remain in the United States. We also review other potential indices for liver transplantation, including donor-recipient matching and the retransplant donor risk index. Although substantial progress has been made in developing donor risk indices to objectively assess donor variables that affect transplant outcomes, continued efforts are warranted to improve these indices to enhance organ allocation policies and optimize allograft survival.