National Trends in Extended Criteria Donor Utilization and Outcomes for Lung Transplantation

Scoring donor lungs for graft failure risk: The Lung Donor Risk Index (LDRI)

Lung transplantation lags behind other solid organ transplants in donor lung utilization due, in part, to uncertainty regarding donor quality. We sought to develop an easy-to-use donor risk metric that, unlike existing metrics, accounts for a rich set of donor factors. Our study population consisted of n = 26 549 adult lung transplant recipients abstracted from the United Network for Organ Sharing Standard Transplant Analysis and Research file. We used Cox regression to model graft failure (GF; earliest of death or retransplant) risk based on donor and transplant factors, adjusting for recipient factors. We then derived and validated a Lung Donor Risk Index (LDRI) and developed a pertinent online application (https://shiny.pmacs.upenn.edu/LDRI_Calculator/). We found 12 donor/transplant factors that were independently predictive of GF: age, race, insulin-dependent diabetes, the difference between donor and recipient height, smoking, cocaine use, cytomegalovirus seropositivity, creatinine, human leukocyte antigen (HLA) mismatch, ischemia time, and donation after circulatory death. Validation showed the LDRI to have GF risk discrimination that was reasonable (C = 0.61) and higher than any of its predecessors. The LDRI is intended for use by transplant centers, organ procurement organizations, and regulatory agencies and to benefit patients in decision-making. Unlike its predecessors, the proposed LDRI could gain wide acceptance because of its granularity and similarity to the Kidney Donor Risk Index.

Validation of a novel donor lung scoring system based on the updated lung Composite Allocation Score

Lung transplantation (LTx) continues to have lower rates of long-term graft survival compared with other organs. Additionally, lung utilization rates from brain-dead donors remain substantially lower compared with other solid organs, despite a growing need for LTx and the significant risk of waitlist mortality. This study aims to examine the effects of using a combination of the recently described novel lung donor (LUNDON) acceptability score and the newly adopted recipient lung Composite Allocation Score (CAS) to guide transplantation. We performed a review of nearly 18 000 adult primary lung transplants from 2015-2022 across the US with retroactive calculations of the CAS value. The medium-CAS group (29.6-34.5) had superior 1-year posttransplant survival. Importantly, the combination of high-CAS (> 34.5) recipients with low LUNDON score (≤ 40) donors had the worst survival at 1 year compared with any other combination. Additionally, we constructed a model that predicts 1-year and 3-year survival using the LUNDON acceptability score and CAS values. These results suggest that caution should be exercised when using marginally acceptable donor lungs in high-priority recipients. The use of the LUNDON score with CAS value can potentially guide clinical decision-making for optimal donor-recipient matches for LTx.

Postoperative Acute Kidney Injury and Long-Term Outcomes After Lung Transplantation

BACKGROUND

This study sought to characterize perioperative risk factors of acute kidney injury (AKI) and report outcomes associated with its development in the immediate postoperative setting after lung transplantation.

METHODS

Study investigator performed a retrospective analysis of all adult patients undergoing primary lung transplantation at a single institution from January 1, 2011 to December 31, 2021 AKI was defined using Kidney Disease: Improving Global Outcomes (KDIGO) criteria after lung transplantation and was stratified on the basis of whether patients required renal replacement therapy (RRT; AKI-no RRT vs AKI-RRT).

RESULTS

Of the 754 patients included, 369 (48.9%) any AKI developed in the postoperative period (252 AKI-no RRT vs 117 AKI-RRT). Risk factors for postoperative AKI included higher preoperative creatinine levels (odds ratio [OR], 5.15; P < .001), lower preoperative estimated glomerular filtration rate (OR, 0.99; P < 0.018), delayed chest closure (OR, 2.72; P < .001), and higher volumes of postoperative blood products (OR, 1.09; P < .001) in the multivariable analysis. On univariate analysis, both AKI groups were also associated with higher rates of pneumonia (P < .001), reintubation (P < .001), mortality on index admission (P < 0.001), longer ventilator duration (P < .001), longer intensive care unit length of stay (P < .001), and longer hospital length of stay (P < .001), with the highest rates in the AKI-RRT group. In a multivariable survival analysis, postoperative AKI-no RRT (hazard ratio [HR], 1.50; P = .006) and AKI-RRT (HR, 2.70; P < .001) were associated with significantly worse survival independent of severe grade 3 primary graft dysfunction at 72 hours (HR, 1.45; P = .038).

CONCLUSIONS

The development of postoperative AKI was associated with numerous preoperative and intraoperative factors. Postoperative AKI remained significantly associated with poorer posttransplantation survival. Severe cases of AKI necessitating RRT portended the worst survival after lung transplantation.

Lung Transplantation Outcomes in Recipients Aged 70 Years or Older and the Impact of Center Volume

OBJECTIVE

To evaluate trends and outcomes of lung transplants (LTx) in recipients ≥ 70 years.

METHODS

We performed a retrospective analysis of the UNOS database identifying all patients undergoing LTx (May 2005-December 2022). Baseline characteristics and postoperative outcomes were compared by age (<70 years, ≥70 years) and center volume. Kaplan-Meier analyses were performed with pairwise comparisons between subgroups.

RESULTS

34,957 patients underwent LTx, of which 3236 (9.3%) were ≥70 years. The rate of LTx in recipients ≥ 70 has increased over time, particularly in low-volume centers (LVCs); consequently, high-volume centers (HVCs) and LVCs perform similar rates of LTx for recipients ≥ 70. Recipients ≥ 70 had higher rates of receiving from donor after circulatory death lungs and of extended donor criteria. Recipients ≥ 70 were more likely to die of cardiovascular diseases or malignancy, while recipients < 70 of chronic primary graft failure. Survival time was shorter for recipients ≥ 70 compared to recipients < 70 old (hazard ratio (HR): 1.36, 95% confidence interval (CI): 1.28-1.44, p < 0.001). HVCs were associated with a survival advantage in recipients < 70 (HR: 0.91, 95% CI: 0.88-0.94, p < 0.001); however, in recipients ≥ 70, survival was similar between HVCs and LVCs (HR: 1.11, 95% CI: 0.99-1.25, p < 0.08). HVCs were more likely to perform a bilateral LTx (BLT) for obstructive lung diseases compared to LVCs, but there was no difference in BLT and single LTx likelihood for restrictive lung diseases.

CONCLUSIONS

Careful consideration is needed for recipient ≥ 70 selection, donor assessment, and post-transplant care to improve outcomes. Further research should explore strategies that advance perioperative care in centers with low long-term survival for recipients ≥ 70.

Expanding Donor Options for Lung Transplant: Extended Criteria, Donation After Circulatory Death, ABO Incompatibility, and Evolution of Ex Vivo Lung Perfusion

Only using brain-dead donors with standard criteria, the existing donor shortage has never improved in lung transplantation. Currently, clinical efforts have sought the means to use cohorts of untapped donors, such as extended criteria donors, donation after circulatory death, and donors that are ABO blood group incompatible, and establish the evidence for their potential contribution to the lung transplant needs. Also, technical maturation for using those lungs may eliminate immediate concerns about the early posttransplant course, such as primary graft dysfunction or hyperacute rejection. In addition, recent clinical and preclinical advances in ex vivo lung perfusion techniques have allowed the safer use of lungs from high-risk donors and graft modification to match grafts to recipients and may improve posttransplant outcomes. This review summarizes recent trends and accomplishments and future applications for expanding the donor pool in lung transplantation.

Airway oscillometry parameters in baseline lung allograft dysfunction: Associations from a multicenter study

BACKGROUND

Baseline lung allograft dysfunction (BLAD), the failure to achieve ≥80%-predicted spirometry after lung transplant (LTx), is associated with impaired survival. Physiologic abnormalities in BLAD are poorly understood. Airway oscillometry measures respiratory system mechanics and may provide insight into understanding the mechanisms of BLAD.

OBJECTIVES

This study aims to describe and measure the association between airway oscillometry parameters [Reactance (X_rs5, Ax), Resistance (R_rs5, R_rs5-19)] (1) stable LTx recipients, comparing those with normal spirometry and those with BLAD; and (2) in recipients with chronic lung allograft dysfunction (CLAD), comparing those with normal baseline spirometry and those with BLAD.

METHODS

A multi-center cross-sectional study was performed including bilateral LTx between January 2020 and June 2021. Participants performed concurrent airway oscillometry and spirometry. Multivariable logistic regression was performed to measure the association between oscillometry parameters and BLAD.

RESULTS

A total of 404 LTx recipients performed oscillometry and 253 were included for analysis. Stable allograft function was confirmed in 149 (50.2%) recipients (92 (61.7%) achieving normal spirometry and 57 (38.3%) with BLAD). Among stable LTx recipients, lower X_rs5 Z-Score (aOR 0.50 95% CI 0.37-0.76, p = 0.001) was independently associated with BLAD. CLAD was present in 104 (35.0%) recipients. Among recipients with CLAD, lower X_rs5 Z-Score (aOR 0.73 95% CI 0.56-0.95, p = 0.02) was associated with BLAD.

CONCLUSIONS

Oscillometry provides novel physiologic insights into mechanisms of BLAD. The independent association between X_rs5 and BLAD, in both stable recipients and those with CLAD suggests that respiratory mechanics, in particular abnormal elastance, is an important physiologic feature. Further longitudinal studies are needed to understand the trajectory of oscillometry parameters in relation to allograft outcomes.

Lungs From Donors ≥70 Years of Age for Transplantation-Do Long-Term Outcomes Justify Their Use?

Donor shortages have led transplant centers to extend their criteria for lung donors. Accepting lung donors ≥70 years of age has previously shown good short-term outcomes; however, no mid- and long-term outcome data on these extended criteria donors has been published to date. In this study, all patients who underwent lung transplantation between 06/2010 and 12/2019 were included in the analysis, and the outcomes were compared between patients receiving organs from donors <70 years of age and patients transplanted with lungs from donors ≥70 years of age. Among the 1,168 lung-transplanted patients, 62 patients received lungs from donors ≥70 years of age. The recipient age of those receiving older organs was significantly higher, and they were more likely to suffer from obstructive lung disease. Older donors were exposed to significantly shorter periods of mechanical ventilation prior to donation, had higher Horowitz indices, and were less likely to have smoked. The postoperative time on mechanical ventilation, time on ICU, and total hospital stay were comparable. The overall survival as well as CLAD-free survival showed no differences between both groups in the follow-up period. Utilization of lungs from donors ≥70 years of age leads to excellent mid- and long-term results that are similar to organs from younger donors when the organs from older donors are carefully preselected.

Diagnostic and Therapeutic Implications of Ex Vivo Lung Perfusion in Lung Transplantation: Potential Benefits and Inherent Limitations

Ex vivo lung perfusion (EVLP), a technique in which isolated lungs are continually ventilated and perfused at normothermic temperature, is emerging as a promising platform to optimize donor lung quality and increase the lung graft pool. Over the past few decades, the EVLP technique has become recognized as a significant achievement and gained much attention in the field of lung transplantation. EVLP has been demonstrated to be an effective platform for various targeted therapies to optimize donor lung function before transplantation. Additionally, some physical parameters during EVLP and biological markers in the EVLP perfusate can be used to evaluate graft function before transplantation and predict posttransplant outcomes. However, despite its advantages, the clinical practice of EVLP continuously encounters multiple challenges associated with both intrinsic and extrinsic limitations. It is of utmost importance to address the advantages and disadvantages of EVLP for its broader clinical usage. Here, the pros and cons of EVLP are comprehensively discussed, with a focus on its benefits and potential approaches for overcoming the remaining limitations. Directions for future research to fully explore the clinical potential of EVLP in lung transplantation are also discussed.

Devices for donor lung preservation

INTRODUCTION

Lung transplantation is the gold standard for the treatment of end stage lung disease but is limited by donor availability. Recently, the donor pool has seen significant expansion with liberalization of donor criteria. However, extended criteria donors can require additional time to prepare for implantation, necessitating additional preservation time of donor lungs.

AREAS COVERED

We present a review of current lung transplant storage strategies including new methodologies and technological advancements. The current standard, static cold storage, is a simple and cost-effective method of preserving grafts, but offers little flexibility with limited ability to mitigate ischemic-reperfusion injury, inflammation, and hypothermic tissue damage. Novel ex vivo lung perfusion (EVLP) devices, TransMedics OCS and XVIVO perfusion systems, extend preservation time by perfusing, and ventilating donor lungs while simultaneously allowing for evaluation of lung viability. Perfusate, preservation solutions, additives, temperature regulation, and assessment of organ damage are all critical components when evaluating the success and outcomes of these devices.

EXPERT OPINION

EVLP devices are more costly and often require additional resources and personnel support compared to static cold storage, but may provide the opportunity to extend preservation time, perform functional assessment, mitigate ischemic injury, and optimize extended criteria donors.

Exploring predisposing factors and pathogenesis contributing to injuries of donor lungs

INTRODUCTION

Lung transplantation (LTx) remains the only therapeutic strategy for patients with incurable lung diseases. However, its use has been severely limited by the narrow donor pool and potential concerns of inferior quality of donor lungs, which are more susceptible to external influence than other transplant organs. Multiple insults, including various causes of death and a series of perimortem events, may act together on donor lungs and eventually culminate in primary graft dysfunction (PGD) after transplantation as well as other poor short-term outcomes.

AREAS COVERED

This review focuses on the predisposing factors contributing to injuries to the donor lungs, specifically focusing on the pathogenesis of these injuries and their impact on post-transplant outcomes. Additionally, various maneuvers to mitigate donor lung injuries have been proposed.

EXPERT OPINION

The selection criteria for eligible donors vary and may be poor discriminators of lung injury. Not all transplanted lungs are in ideal condition. With the rapidly increasing waiting list for LTx, the trend of using marginal donors has become more apparent, underscoring the need to gain a deeper understanding of donor lung injuries and discover more donor resources.

Complement-targeting therapeutics for ischemia-reperfusion injury in transplantation and the potential for ex vivo delivery

Organ shortages and an expanding waitlist have led to increased utilization of marginal organs. All donor organs are subject to varying degrees of IRI during the transplant process. Extended criteria organs, including those from older donors and organs donated after circulatory death are especially vulnerable to ischemia-reperfusion injury (IRI). Involvement of the complement cascade in mediating IRI has been studied extensively. Complement plays a vital role in the propagation of IRI and subsequent recruitment of the adaptive immune elements. Complement inhibition at various points of the pathway has been shown to mitigate IRI and minimize future immune-mediated injury in preclinical models. The recent introduction of ex vivo machine perfusion platforms provides an ideal window for therapeutic interventions. Here we review the role of complement in IRI by organ system and highlight potential therapeutic targets for intervention during ex vivo machine preservation of donor organs.

Trends in marginal lung allograft survival: advanced-age donors improve

INTRODUCTION

Although lung demand continues to outpace supply, 75% of potential donor lungs are discarded without being transplanted in the United States. To identify the discarded cohorts best suited to alleviate the lung shortage and reduce waitlist mortality, we explored changes in survival over time for five marginal donor definitions: age >60 years, smoking history >20 pack-years, PaO2/FiO2 <300mmHg, purulent bronchoscopic secretions, and chest radiograph infiltrates.

METHODS

Our retrospective cohort study separated 27,803 lung recipients in the UNOS Database into three 5-year eras by transplant date: 2005-2009, 2010-2014, and 2015-2019. Multivariable Cox proportional hazards regression and Kaplan-Meier analysis with log-rank test were used to compare survival across the eras.

RESULTS

Three definitions-low PaO 2/FiO 2, purulent bronchoscopic secretions, and abnormal chest radiographs-did not bear out as truly marginal, demonstrating lack of significantly elevated risk. Advanced donor age demonstrated considerable survival improvement (HR (95% CI): 1.47 (1.26-1.72) in 2005-2009 down to 1.14 (0.97-1.35) for 2015-2019), with protective factors being recipients <60 years, moderate recipient BMI, and low Lung Allocation Score. Donors with smoking history failed to demonstrate any significant improvement (HR (95% CI): 1.09 (1.01-1.17) in 2005-2009 increasing to 1.22 (1.08-1.38) in 2015-2019).

CONCLUSIONS

Advanced donor age, previously the most significant risk factor, has improved to near- benchmark levels, demonstrating the possibility for matching older donors to healthier non-elderly recipients in selected circumstances. Low PaO 2/FiO 2, bronchoscopic secretions, and abnormal radiographs demonstrated survival on par with standard donors. Significant donor smoking history, a moderate risk factor, has failed to improve. This article is protected by copyright. All rights reserved.

The role of radiology in addressing the challenge of lung cancer after lung transplantation

The importance of lung cancer as a complication of lung transplantation is increasingly recognised. It may become an important survival-limiting factor in lung transplant patients as management of other complications continues to improve and utilisation of extended criteria donors grows. Radiology can play a key role in tackling this issue at multiple stages in the transplantation pathway and follow-up process. Routine chest CT as part of pre-transplant recipient assessment (and donor assessment if available) can identify suspicious lung lesions with high sensitivity and detect chronic structural lung diseases such as pulmonary fibrosis associated with an increased risk of malignancy post-transplant. Pre-transplant CT also provides a comparison for later CT studies in the assessment of nodules or masses. The potential role of regular chest CT for lung cancer screening after transplantation is less certain due to limited available evidence on its efficacy. Radiologists should be cognisant of how the causes of pulmonary nodules in lung transplant patients may differ from the general population, vary with time since transplantation and require specific recommendations for further investigation/follow-up as general guidelines are not applicable. As part of the multidisciplinary team, radiology is involved in an aggressive diagnostic and therapeutic management approach for nodular lung lesions after transplant both through follow-up imaging and image-guided tissue sampling. This review provides a comprehensive overview of available clinical data and evidence on lung cancer in lung transplant recipients, and in particular an assessment of the current and potential roles of pre- and post-transplant imaging. KEY POINTS: • Lung cancer after lung transplantation may become an increasingly important survival-limiting factor as mortality from other complications declines. • There are a number of important roles for radiology in tackling the issue which include pre-transplant CT and supporting an aggressive multidisciplinary management strategy where lung nodules are detected in transplant patients. • The introduction of routine surveillance chest CT after transplant in addition to standard clinical follow-up as a means of lung cancer screening should be considered.

Primary Graft Dysfunction: The Role of Aging in Lung Ischemia-Reperfusion Injury

Transplant centers around the world have been using extended criteria donors to remedy the ongoing demand for lung transplantation. With a rapidly aging population, older donors are increasingly considered. Donor age, at the same time has been linked to higher rates of lung ischemia reperfusion injury (IRI). This process of acute, sterile inflammation occurring upon reperfusion is a key driver of primary graft dysfunction (PGD) leading to inferior short- and long-term survival. Understanding and improving the condition of older lungs is thus critical to optimize outcomes. Notably, ex vivo lung perfusion (EVLP) seems to have the potential of reconditioning ischemic lungs through ex-vivo perfusing and ventilation. Here, we aim to delineate mechanisms driving lung IRI and review both experimental and clinical data on the effects of aging in augmenting the consequences of IRI and PGD in lung transplantation.

Impact of ex vivo lung perfusion on brain-dead donor lung utilization: The French experience

Ex vivo lung perfusion (EVLP) is a valuable method for expanding the lung donor pool. Its indications currently differ across centers. This national retrospective cohort study aimed to describe the profile of donors with lungs transplanted after EVLP and determine the effectiveness of EVLP on lung utilization. We included brain-dead donors with at least one lung offered between 2012 and 2019 in France. Lungs transplanted without or after EVLP were compared with those that were rejected. Donor group phenotypes were determined with multiple correspondence analysis (MCA). The association between donor factors and lung transplantation was assessed with a multivariable multinomial logistic regression. MCA revealed that donors whose lungs were transplanted after EVLP had profiles similar to the donors whose lungs were declined and quite different from those of donors with lungs transplanted without EVLP. Donor predictors of graft nonuse included age ≥50 years, smoking history, PaO₂ /FiO₂ ratio ≤300 mmHg, abnormal chest imaging, and purulent secretions. EVLP increased utilization of lungs from donors with a smoking history, PaO₂ /FiO₂ ratio ≤300 mmHg, and abnormal chest imaging.

The Year in Cardiothoracic Transplant Anesthesia: Selected Highlights From 2020 Part I - Lung Transplantation

This special article focuses on the highlights in cardiothoracic transplantation literature in the year 2020. Part I encompasses the recent literature on lung transplantation, including the advances in preoperative assessment and optimization, donor management, including the use of ex-vivo lung perfusion, recipient management, including those who have been infected with coronavirus disease 2019, updates on the perioperative management, including the use of extracorporeal membrane oxygenation, and long-term outcomes.

Impact of center donor acceptance patterns on utilization of extended-criteria donors and outcomes

BACKGROUND

This study investigated the impact of transplanting center donor acceptance patterns on usage of extended-criteria donors (ECDs) and posttransplant outcomes following orthotopic heart transplantation (OHT).

METHODS

The Scientific Registry of Transplant Recipients was queried to identify heart donor offers and adult, isolated OHT recipients in the United States from January 1, 2013 to October 17, 2018. Centers were stratified into three equal-size terciles based on donor heart acceptance rates (<13.7%, 13.7%-20.2%, >20.2%). Overall survival was compared between recipients of ECDs (≥40 years, left ventricular ejection fraction [LVEF] <60%, distance ≥500 miles, hepatitis B virus [HBV], hepatitis C virus [HCV], or human immunodeficiency virus [HIV], or ≥50 refusals) and recipients of traditional-criteria donors, and among transplanting terciles.

RESULTS

A total of 85,505 donor heart offers were made to 133 centers with 15,264 (17.9%) accepted for OHT. High-acceptance programs (>20.2%) more frequently accepted donors with LVEF <60%, HIV, HCV, and/or HBV, ≥50 offers, or distance >500 miles from the transplanting center (each p < .001). Posttransplant survival was comparable across all three terciles (p = .11). One- and five-year survival were also similar across terciles when examining recipients of all five ECD factors. Acceptance tier and increasing acceptance rate were not found to have any impact on mortality in multivariable modeling. Of ECD factors, only age ≥40 years was found to have increased hazards for mortality (hazard ratio, 1.33; 95% confidence interval [CI], 1.22-1.46; p < .001).

CONCLUSIONS

Of recipients of ECD hearts, outcomes are similar across center-acceptance terciles. Educating less aggressive programs to increase donor acceptance and ECD utilization may yield higher national rates of OHT without major impact on outcomes.