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Computer simulation has played a pivotal role in analyzing alternative organ allocation strategies in transplantation. The current approach to producing cohorts of organ donors and candidates for individual-level simulation requires directly re-sampling retrospective data from a transplant registry. This historical data may reflect outmoded policies and practices as well as systemic inequities in candidate listing, limiting contemporary applicability of simulation results. We describe the development of an alternative approach for generating synthetic donors and candidates using hierarchical Bayesian network probability models. We developed two Bayesian networks to model dependencies among 10 donor and 36 candidate characteristics relevant to waitlist survival, donor-candidate matching, and post-transplant survival. We estimated parameters for each model using Scientific Registry of Transplant Recipients (SRTR) data. For 100 donor and 100 candidate synthetic populations generated, proportions for each categorical donor or candidate attribute, respectively, fell within one percentage point of observed values; the interquartile ranges (IQRs) of each continuous variable contained the corresponding SRTR observed median. Comparisons of synthetic to observed stratified distributions demonstrated the ability of the method to capture complex joint variability among multiple characteristics. We also demonstrated how changing two upstream population parameters can exert cascading effects on multiple relevant clinical variables in a synthetic population. Generating synthetic donor and candidate populations in transplant simulation may help overcome critical limitations related to the re-sampling of historical data, allowing developers and decision makers to customize the parameters of these populations to reflect realistic or hypothetical future states., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Gunsalus et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Objectives: To study the impact of using the US Public Health Service broadened definition of "increased-risk" donors (2013) in comparison with "high-risk" (1994) and standard infectious risk donors on lung transplant recipient outcomes., Methods: Patients who underwent lung transplant between January 1, 2006, and May 31, 2017, in the Scientific Registry of Transplant Recipients were divided into 2 cohorts, recipients of: (1) high-risk donors: January 1, 2006, to October 1, 2013, and (2) increased-risk donors: January 1, 2014, to May 31, 2017, and compared with matched recipients who received standard-risk donors. Risks for acute rejection, patient, and graft survival using propensity score matched cohorts, multivariable logistic, and Cox models were examined., Results: In total, 18,490 lung transplant recipients were analyzed with 36% transplanted during the increased-risk donor definition period. The proportion of donors classified as nonstandard infectious risk increased with the definition change (8% high-risk donors vs 22% increased-risk donors; P < .001). In both cohorts, male patients with a lower forced expiratory volume in 1 second and greater creatinine were more likely to receive an organ from increased risk donors. Neither graft nor patient survival differed by donor type in either period. Acute treated rejection within 1 year did not differ by period for recipients of increased risk donors (odds ratio, 0.87; P = .23) or recipients of high-risk donors (odds ratio, 1.2; P = .27)., Conclusions: The 2013 broadened definition of donor risk increased the proportion of nonstandard infectious risk donors. Recipients of increased/high-risk donors had similar graft and patient survival compared with standard-risk donors., (Copyright © 2019 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.)

Objectives: This study aims to understand the complex factors affecting heart transplant survival and to determine the importance of possible sex-specific risk factors., Background: Heart transplant allocation is primarily focused on preventing waitlist mortality. To prevent organ wastage, future allocation must balance risk of waitlist mortality with post-transplantation mortality. However, more information regarding risk factors after heart transplantation is needed., Methods: We included all adults (30,606) in the Scientific Registry of Transplant Recipients database who underwent isolated heart transplantation from January 1, 2004, to July 1, 2018. Mortality (8,278 deaths) was verified with the complete Social Security Death Index with a median follow-up of 3.9 years. Temporal decomposition was used to identify phases of survival and phase-specific risk factors. The random survival forests method was used to determine importance of mortality risk factors and their interactions., Results: We identified 3 phases of mortality risk: early post-transplantation, constant, and late. Sex was not a significant risk factor. There were several interactions predicting early mortality such as pretransplantation mechanical ventilation with presence of end-organ function (bilirubin, renal function) and interactions predicting later mortality such as diabetes and older age (donor and recipient). More complex interactions predicting early-, mid-, and late-mortality existed and were identified with machine learning (i.e., elevated bilirubin, mechanical ventilation, and dialysis)., Conclusions: Post-heart transplant mortality risk is complex and dynamic, changing with time and events. Sex is not an important mortality risk factor. To prevent organ wastage, end-organ dysfunction should be resolved before transplantation as much as possible., (Copyright © 2020 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: The thoracic simulated allocation model (TSAM) is used by the Scientific Registry of Transplant Recipients to predict the relative effect of organ allocation policy changes. A new lung allocation policy changing the first unit of allocation from donation service area to 250 nautical miles took effect on November 24, 2017. We studied TSAM's ability to correctly predict trends caused by changes in allocation policy., Methods: We compared the population characteristics from the TSAM cohort, 6,386 lung transplant candidates from 2009 to 2011, with the observed cohort of 7,601 candidates from the year before the policy change on November 24, 2017, and the year after. Simulations were run 10 times. Waitlist mortality and transplant rates were calculated and compared with observed mortality and transplant rates in the years before and after the policy change., Results: TSAM correctly predicted no change in overall waitlist mortality or transplant rates with the policy change. Observed waitlist mortality values were higher, as were transplant rates, because of increased organ donation and population change. TSAM predicted increased transplant rates for diagnosis group D (idiopathic pulmonary fibrosis), decreased rates for group A (chronic obstructive pulmonary disease), and increased rates for candidates with lung allocation score ≥50, but these changes did not occur in the waitlist and transplant populations after the policy change., Conclusions: TSAM correctly predicted the relative trends caused by a change in allocation policy but smaller sub-group predictions were not seen., (Copyright © 2019 International Society for Heart and Lung Transplantation. All rights reserved.)

The primary goal of US lung allocation policy is to ensure that candidates with the highest risk for mortality receive appropriate access to lung transplant. In 2018, 2562 lung transplants were performed in the US, reflecting a 31% increase over the past 5 years. More candidates are being listed for lung transplant, and the number of donors has increased substantially. Despite an increase of 84 lung transplants in 2018, 365 adult candidates died or became too sick to undergo transplant. In 2018, 24 new child (ages 0-11 years) candidates were added to the lung transplant waiting list. Fifteen lung transplants were performed in recipients aged 0-11 years, three in recipients aged younger than 1 year, two in recipients aged 1-5 years, and ten in recipients aged 6-11 years. Of 27 child candidates removed from the waiting list in 2018, 16 (59.3%) were removed due to undergoing transplant, six (22.2%) due to death, one (3.7%) due to improved condition, and one (3.7%) due to becoming too sick to undergo transplant., (.)

Each year since 2012, the number of lung transplants has increased, reflecting an increase in the number of donors, improved use of recovered organs, and more candidates being listed for transplant. However, the need for organs continues to outpace available donors. Despite an increase of 126 donors in 2017, 1360 candidates remained on the waiting list at the end of the year, and 326 patients died or became too sick to undergo transplant. Approximately 14,000 individuals were living with a lung transplant in 2017; 9492 were aged 50 years or older, 4075 were aged 18-49 years, and 408 were aged younger than 18 years., (.)

Variation in heart and lung offer acceptance practices may affect numbers of transplanted organs and create variability in waitlist mortality. To investigate these issues, offer acceptance ratios, or adjusted odds ratios, for heart and lung transplant programs individually and for all programs within donation service areas (DSAs) were estimated using offers from donors recovered July 1, 2016, and June 30, 2017. Logistic regressions estimated the association of DSA-level offer acceptance ratios with donor yield and local placement of organs recovered in the DSA. Competing risk methodology estimated the association of program-level offer acceptance ratios with incidence and rate of waitlist removals due to death or becoming too sick to undergo transplant. Higher DSA-level offer acceptance was associated with higher yield (odds ratios [ORs]: lung, 1.04 1.11 1.19 ; heart, 1.09 1.21 1.35 ) and more local placement of transplanted organs (ORs: lung, 1.01 1.12 1.24 ; heart, 1.47 1.69 1.93 ). Higher program-level offer acceptance was associated with lower incidence of waitlist removal due to death or becoming too sick to undergo transplant (hazard ratios [HRs]: heart, 0.80 0.86 0.93 ; lung, 0.67 0.75 0.83 ), but not with rate of waitlist removal (HRs: heart, 0.91 0.98 1.06 ; lung, 0.89 0.99 1.10 ). Heart and lung offer acceptance practices affected numbers of transplanted organs and contributed to program-level variability in the probability of waitlist mortality., (© 2018 The American Society of Transplantation and the American Society of Transplant Surgeons.)

In 2015, 2409 active candidates aged 12 years or older were added to the lung transplant waiting list; 2072 transplants were performed, the most of any year. The median waiting time for candidates listed in 2015 was 3.4 months; the shortest waiting time was for diagnosis group D. Despite the highest recorded transplant rate of 157 per 100 waitlist years, waitlist mortality continued a steady decade-long rise to a high of 16.5 deaths per 100 waitlist years. Measures of short- and long-term survival showed no trend toward improved overall survival in the past 5 years, except that 6-month death rates decreased from 9.4% in 2005 to 7.9% in 2014. At 5 years posttransplant, 55.5% of recipients remained alive. In 2015, 23 new child (ages 0-11 years) candidates were added to the list; 17 transplants were performed. Incidence of death was 6.1% at 6 months and 8.2% at 1 year for transplants in 2013-2014. Important policy changes will affect access to transplant. In February 2015, OPTN implemented a comprehensive revision of the lung allocation score to better reflect mortality risk. Broader geographic sharing of donor lungs for pediatric candidates and allowance for selected transplants across blood types for candidates aged younger than 2 years have been approved and are expected to improve pediatric access to transplant. The impact of these changes on lung transplant trends will be observed in the coming years., (.)

US pediatric transplant candidates have limited access to lung transplant due to the small number of donors within current geographic boundaries, leading to assertions that the current lung allocation system does not adequately serve pediatric patients. We hypothesized that broader geographic sharing of pediatric (adolescent, 12-17 years; child, <12 years) donor lungs would increase pediatric candidate access to transplant. We used the thoracic simulated allocation model to simulate broader geographic sharing. Simulation 1 used current allocation rules. Simulation 2 offered adolescent donor lungs across a wider geographic area to adolescents. Simulation 3 offered child donor lungs across a wider geographic area to adolescents. Simulation 4 combined simulations 2 and 3. Simulation 5 prioritized adolescent donor lungs to children across a wider geographic area. Simulation 4 resulted in 461 adolescent transplants per 100 patient-years on the waiting list (range 417-542), compared with 206 (range 180-228) under current rules. Simulation 5 resulted in 388 adolescent transplants per 100 patient-years on the waiting list (range 348-418) and likely increased transplant rates for children. Adult transplant rates, waitlist mortality, and 1-year posttransplant mortality were not adversely affected. Broader geographic sharing of pediatric donor lungs may increase pediatric candidate access to lung transplant., (© Copyright 2015 The American Society of Transplantation and the American Society of Transplant Surgeons.)

This document was developed through the collaborative efforts of the Society of Critical Care Medicine, the American College of Chest Physicians, and the Association of Organ Procurement Organizations. Under the auspices of these societies, a multidisciplinary, multi-institutional task force was convened, incorporating expertise in critical care medicine, organ donor management, and transplantation. Members of the task force were divided into 13 subcommittees, each focused on one of the following general or organ-specific areas: death determination using neurologic criteria, donation after circulatory death determination, authorization process, general contraindications to donation, hemodynamic management, endocrine dysfunction and hormone replacement therapy, pediatric donor management, cardiac donation, lung donation, liver donation, kidney donation, small bowel donation, and pancreas donation. Subcommittees were charged with generating a series of management-related questions related to their topic. For each question, subcommittees provided a summary of relevant literature and specific recommendations. The specific recommendations were approved by all members of the task force and then assembled into a complete document. Because the available literature was overwhelmingly comprised of observational studies and case series, representing low-quality evidence, a decision was made that the document would assume the form of a consensus statement rather than a formally graded guideline. The goal of this document is to provide critical care practitioners with essential information and practical recommendations related to management of the potential organ donor, based on the available literature and expert consensus.

Lungs are allocated to adult and adolescent transplant candidates (aged ⩾ 12 years) on the basis of age, geography, blood type compatibility, and the lung allocation score (LAS), which reflects risk of waitlist mortality and probability of posttransplant survival. In 2013, the most adult candidates, 2394, of any year were added to the list. Overall median waiting time for candidates listed in 2013 was 4.0 months. The preferred procedure remained bilateral lung transplant, representing approximately 70% of lung transplants in 2013. Measures of short-term and longterm survival have plateaued since the implementation of the LAS in 2005. The number of new child candidates (aged 0-11 years) added to the lung transplant waiting list increased to 39 in 2013. A total of 28 lung transplants were performed in child recipients, 3 for ages younger than 1 year, 9 for ages 1 to 5 years, and 16 for ages 6 to 11 years. The diagnosis of pulmonary hypertension was associated with higher survival rates than cystic fibrosis or other diagnosis (pulmonary fibrosis, bronchiolitis obliterans, bronchopulmonary dysplasia). For child candidates, infection was the leading cause of death in year 1 posttransplant and graft failure in years 2 to 5., (© Copyright 2015 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Rationale: Donation after circulatory determination of death (DCDD) has the potential to increase the number of organs available for transplantation. Because consent and management of potential donors must occur before death, DCDD raises unique ethical and policy issues., Objectives: To develop an ethics and health policy statement on adult and pediatric DCDD relevant to critical care and transplantation stakeholders., Methods: A multidisciplinary panel of stakeholders was convened to develop an ethics and health policy statement. The panel consisted of representatives from the American Thoracic Society, Society of Critical Care Medicine, International Society for Heart and Lung Transplantation, Association of Organ Procurement Organizations, and the United Network of Organ Sharing. The panel reviewed the literature, discussed important ethics and health policy considerations, and developed a guiding framework for decision making by stakeholders., Results: A framework to guide ethics and health policy statement was established, which addressed the consent process, pre- and post mortem interventions, the determination of death, provisions of end-of-life care, and pediatric DCDD., Conclusions: The information presented in this Statement is based on the current evidence, experience, and clinical rationale. New clinical research and the development and dissemination of new technologies will eventually necessitate an update of this Statement.