Association Between Prolonged Graft Ischemia and Primary Graft Failure or Survival Following Lung Transplantation

Donor Lung Preservation at 10°C: Clinical and Logistical Impact

INTRODUCTION

Cold static donor lung preservation at 10°C appears to be a promising method to safely extend the cold ischemic time (CIT) and improve lung transplant (LTx) logistics.

METHODS

LTx from November 2021 to February 2023 were included in this single institution, prospective, non-randomized study comparing prolonged preservation at 10°C versus standard preservation on ice. The inclusion criteria for 10°C preservation were suitable grafts for LTx without any donor retrieval concerns.

PRIMARY ENDPOINT

primary graft dysfunction (PGD) grade-3 at 72-h. Secondary endpoints: clinical outcomes, cytokine profile and logistical impact.

RESULTS

Thirty-three out of fifty-seven cases were preserved at 10°C. Donor and recipient characteristics were similar across the groups. Total preservation times (h:min) were longer (p<0.001) in the 10°C group [1st lung: median 12:09 (IQR 9:23-13:29); 2nd: 14:24 (12:00-16:20)] vs. standard group [1st lung: median 5:47 (IQR 5:18-6:40); 2nd: 7:15 (6:33-7:40)]. PGD grade-3 at 72-h was 9.4% in 10°C group vs. 12.5% in standard group (p=0.440). Length of mechanical ventilation (MV), ICU and hospital stays were similar in both groups. Thirty and ninety-day mortality rates were 0% in 10°C group (vs. 4.2% in standard group). IL-8 concentration was significantly higher 6-h post-LTx in the standard group (p=0.025) and IL-10 concentration was increased 72-h post-LTx in the 10°C group (p=0.045).

CONCLUSIONS

Preservation at 10°C may represent a safe and feasible strategy to intentionally prolong the CIT. In our center, extending the CIT at 10°C may allow for semi-elective LTx and improve logistics with similar outcomes compared to the current standard preservation on ice.

Impact of Prolonged Cold Ischemia Time on Long-Term Survival in Lung Transplant Recipients

BACKGROUND

Cold ischemia time (CIT) influences short- and long-term outcomes in lung transplant recipients. Most studies proved that prolonged CIT causes increased mortality. This study aimed to investigate the impact of prolonged CIT on patient survival time after lung transplantation (LTx).

METHODS

The retrospective study group consisted of 139 patients who underwent double LTx in a single center between January 2018 and August 2022. Prolonged ischemic time (PIT) was defined as total ischemic time >6 hours and divided into smaller time intervals according to increasing PIT (6-8, 8-10, 10-12, >12 hours). The assessed outcomes were 1- and 4-year survival.

RESULTS

Among the study group, PIT was observed in 98% (n = 137), and its average value was 10.33 hours. The prolonged CIT of 6 to 8 hours occurred in 10% (n = 14), 8 to 10 hours in 34% (n = 47), 10 to 12 hours in 36% (n = 49), and >12 hours in 20% (n = 27). In a comparison of 1-year survival between the PIT 6- to 10-hour group and the >10-hour arm (88% vs 78%), the difference was not statistically significant (P > .05).

CONCLUSION

PIT is a risk factor for reduced long-term survival in LTx recipients. Increasing PIT may be associated with higher mortality at 1 and 4 years. All efforts to reduce the duration of ischemic time can benefit patient survival after LTx.

Controlled Hypothermic Storage for Lung Preservation: Leaving the Ice Age Behind

Controlled hypothermic storage (CHS) is a recent advance in lung transplantation (LTx) allowing preservation at temperatures higher than those achieved with traditional ice storage. The mechanisms explaining the benefits of CHS compared to conventional static ice storage (SIS) remain unclear and clinical data on safety and feasibility of lung CHS are limited. Therefore, we aimed to provide a focus review on animal experiments, molecular mechanisms, CHS devices, current clinical experience, and potential future benefits of CHS. Rabbit, canine and porcine experiments showed superior lung physiology after prolonged storage at 10°C vs. ≤4°C. In recent molecular analyses of lung CHS, better protection of mitochondrial health and higher levels of antioxidative metabolites were observed. The acquired insights into the underlying mechanisms and development of CHS devices allowed clinical application and research using CHS for lung preservation. The initial findings are promising; however, further data collection and analysis are required to draw more robust conclusions. Extended lung preservation with CHS may provide benefits to both recipients and healthcare personnel. Reduced time pressure between procurement and transplantation introduces flexibility allowing better decision-making and overnight bridging by delaying transplantation to daytime without compromising outcome.

Identification of Neutrophil Extracellular Trap-Related Gene Expression Signatures in Ischemia Reperfusion Injury During Lung Transplantation: A Transcriptome Analysis and Clinical Validation

Purpose

Ischemia reperfusion injury (IRI) unavoidably occurs during lung transplantation, further contributing to primary graft dysfunction (PGD). Neutrophils are the end effectors of IRI and activated neutrophils release neutrophil extracellular traps (NETs) to further amplify damage. Nevertheless, potential contributions of NETs in IRI remain incompletely understood. This study aimed to explore NET-related gene biomarkers in IRI during lung transplantation.

Methods

Differential expression analysis was applied to identify differentially expressed genes (DEGs) for IRI during lung transplantation based on matrix data (GSE145989, 127003) downloaded from GEO database. The CIBERSORT and weighted gene co-expression network analysis (WGCNA) algorithms were utilized to identify key modules associated with neutrophil infiltration. Moreover, the least absolute shrinkage and selection operator regression and random forest were applied to identify potential NET-associated hub genes. Subsequently, the screened hub genes underwent further validation of an external dataset (GSE18995) and nomogram model. Based on clinical peripheral blood samples, immunofluorescence staining and dsDNA quantification were used to assess NET formation, and ELISA was applied to validate the expression of hub genes.

Results

Thirty-eight genes resulted from the intersection between 586 DEGs and 75 brown module genes, primarily enriched in leukocyte migration and NETs formation. Subsequently, four candidate hub genes (FCAR, MMP9, PADI4, and S100A12) were screened out via machine learning algorithms. Validation using an external dataset and nomogram model achieved better predictive value. Substantial NETs formation was demonstrated in IRI, with more pronounced NETs observed in patients with PGD ≥ 2. PADI4, S100A12, and MMP9 were all confirmed to be up-regulated after reperfusion through ELISA, with higher levels of S100A12 in PGD ≥ 2 patients compared with non-PGD patients.

Conclusion

We identified three potential NET-related biomarkers for IRI that provide new insights into early detection and potential therapeutic targets of IRI and PGD after lung transplantation.

Safety and efficacy of delaying lung transplant surgery to a morning start

Objective

We aimed to evaluate the safety and efficacy of delaying lung transplantation until morning for donors with cross-clamp times occurring after 1:30 am.

Methods

All consented adult lung transplant recipients between March 2018 and May 2022 with donor cross-clamp times between 1:30 am and 5 am were enrolled prospectively in this study. Skin incision for enrolled recipients was delayed until 6:30 am (Night group). The control group was identified using a 1:2 logistic propensity score method and included recipients of donors with cross-clamp times occurring at any other time of day (Day group). Short- and medium-term outcomes were examined between groups. The primary endpoint was early mortality (30-day and in-hospital).

Results

Thirty-four patients were enrolled in the Night group, along with 68 well-matched patients in the Day group. As expected, donors in the Night group had longer cold ischemia times compared to the Day group (344 minutes vs 285 minutes; P < .01). Thirty-day mortality (3% vs 3%; P = .99), grade 3 primary graft dysfunction at 72 hours (8% vs 4%; P = .40), postoperative complications (26% vs 38%; P = .28), and hospital length of stay (15 days vs 14 days; P = .91) were similar in the 2 groups. No significant differences were noted between groups in 3-year survival (70% vs 77%; P = .30) or freedom from chronic lung allograft dysfunction (91% vs 95%; P = .75) at 3 years post-transplantation. The median follow-up was 752.5 days (interquartile range, 487-1048 days).

Conclusions

Lung transplant recipients with donor cross-clamp times scheduled after 1:30 am may safely have their operations delayed until 6:30 am with acceptable outcomes. Adoption of such a policy in clinically appropriate settings may lead to an alternative workflow and improved team well-being.

Risk of prolonged ischemic time linked to use of cardiopulmonary bypass during implantation for lung transplantation in the United Kingdom

BACKGROUND

Some degree of ischemia is inevitable in organ transplantation, and for most, if not all organs, there is a relationship between ischemic time and transplant outcome. The contribution of ischemic time to lung injury is unclear, with conflicting recent data. In this study, we investigate the impact of ischemia time on survival after lung transplantation in a large national cohort.

METHODS

We studied the outcomes for 1,565 UK adult lung transplants over a 12-year period, for whom donor, transplant, and recipient data were available from the UK Transplant Registry. We examined the effect of ischemia time (defined as donor cross-clamp to recipient reperfusion) and whether standard cardiopulmonary bypass was used using Cox proportional hazards models, adjusting for other risk factors.

RESULTS

The total ischemic time increased from a median under 5 hours in 2003 to over 6.2 hours in 2013. Our findings show that, when the cardiopulmonary bypass was used, there was an increase in the hazard of death (of 13% [95% CI: 5%-21%] for 1-year patient survival) for each hour of total ischemic time. However, if the cardiopulmonary bypass was not used for implantation, this link disappeared-there was no statistically significant change in mortality with increasing ischemic time.

CONCLUSIONS

We document that avoidance of bypass may remove ischemic time, within the limits of our observed range of ischemic times, as a risk factor for poor outcomes. Our data add to the evidence that bypass may be harmful to the donor lung.

Risk factors and prognosis of airway complications in lung transplant recipients: A systematic review and meta-analysis

BACKGROUND

Airway complications (AC) are one of leading causes of morbidity and mortality after lung transplant (LTx), but their predictors and outcomes remain controversial. This study aimed to identify potential risk factors and prognosis of AC.

METHODS

A systematic review was performed by searching PubMed, Embase, and Cochrane Library. All observational studies reporting outcome and potential factors of AC after LTx were included. The incidence, mortality, and estimated effect of each factor for AC were pooled by using the fixed-effects model or random-effects model.

RESULTS

Thirty-eight eligible studies with 52,116 patients undergoing LTx were included for meta-analysis. The pooled incidence of AC was 12.4% (95% confidence interval [CI] 9.5-15.8) and the mean time of occurrence was 95.6 days. AC-related mortality rates at 30-days, 90-days, 6 months, 1 year, and 5 years were 6.7%, 17.9%, 18.2%, 23.6%, and 66.0%, respectively. Airway dehiscence was the most severe type with a high mortality at 30 days (60.9%, 95% CI 20.6-95.2). We found that AC was associated with a higher risk of mortality in LTx recipients (hazard ratio [HR] 1.71, 95% CI 1.04-2.81). Eleven significant predictors for AC were also identified, including male donor, male recipient, diagnosis of COPD, hospitalization, early rejection, postoperative infection, extracorporeal membrane oxygenation, mechanical ventilation, telescopic anastomosis, and bilateral and right-sided LTx.

CONCLUSION

AC was significantly associated with higher mortality after LTx, especially for dehiscence. Targeted prophylaxis for modifiable factors and enhanced early bronchoscopy surveillance after LTx may improve the disease burden of AC.

Extension of Cold Static Donor Lung Preservation at 10°C

BACKGROUND: Lung transplantation is performed on a 24/7 schedule to minimize organ ischemic time. Recent preclinical studies demonstrated superior graft preservation at 10°C compared with storage in an ice cooler (gold standard). METHODS: In this prospective, multicenter, nonrandomized clinical trial, we studied transplants from donors with overnight cross-clamp times (6:00 p.m. to 4:00 a.m.) that had an earliest allowed starting time of 6:00 a.m. Lungs meeting criteria for transplantation were retrieved, transported, and immediately transferred to a 10°C temperature-controlled incubator until implantation; 70 patients and 140 matched controls were included in this study. RESULTS: Total preservation times for lungs in the study group were 12 hours, 28 minutes (interquartile range, 10 hours, 14 minutes to 14 hours, 12 minutes) and 14 hours, 9 minutes (interquartile range, 12 hours, 3 minutes to 15 hours, 45 minutes) for the first and second lung implanted, respectively. Primary graft dysfunction grade 3 at 72 hours (primary outcome) was 5.7% in the study group versus 9.3% in matched controls (difference, −3.6; 95% confidence interval [CI], −10.5 to 5.3). No meaningful differences were observed in the need for postoperative extracorporeal membrane oxygenation (5.7 vs. 9.3%), median intensive care unit stay (5 vs. 5 days), or median hospital stay (25 vs. 30 days) between the two groups. One-year Kaplan–Meier survival was similar between the two groups (94 vs. 87%; hazard ratio, 0.65; 95% CI, 0.26 to 1.6). CONCLUSIONS: Extension of cold static preservation times at 10°C appears to be safe and has the potential to improve transplantation logistics and performance. (Funded by the UHN Foundation; Clinicaltrials.gov number, NCT04616365).

Lung preservation: from perfusion to temperature

PURPOSE OF REVIEW

This article will review the evidence behind elements of the lung preservation process that have remained relatively stable over the past decade as well as summarize recent developments in ex-vivo lung perfusion and new research challenging the standard temperature for static cold storage.

RECENT FINDINGS

Ex-vivo lung perfusion is becoming an increasingly well established means to facilitate greater travel distance and allow for continued reassessment of marginal donor lungs. Preliminary reports of the use of normothermic regional perfusion to allow utilization of lungs after DCD recovery exist, but further research is needed to determine its ability to improve upon the current method of DCD lung recovery. Also, research from the University of Toronto is re-assessing the optimal temperature for static cold storage; pilot studies suggest it is a feasible means to allow for storage of lungs overnight to allow for daytime transplantation, but ongoing research is awaited to determine if outcomes are superior to traditional static cold storage.

SUMMARY

It is crucial to understand the fundamental principles of organ preservation to ensure optimal lung function posttransplant. Recent advances in the past several years have the potential to challenge standards of the past decade and reshape how lung transplantation is performed.

Airway Complications after Lung Transplantation-A Contemporary Series of 400 Bronchial Anastomoses from a Single Center

(1) Objective: To determine whether recent advances in lung transplantation (LT) have reduced the incidence and changed the risk factors for airway complications (AC). (2) Methods: Retrospective analysis of patients receiving a lung transplant between January 2007 and January 2019. An AC was defined as a bronchoscopic abnormality in the airway, either requiring or not requiring an endoscopic or surgical intervention. Both univariable and multivariable analyses were performed to identify risk factors for AC. (3) Results: 285 lung transplants (170 single and 115 bilateral lung transplants) were analysed, comprising 400 anastomoses at risk. A total of 50 anastomoses resulted in AC (12%). There were 14 anastomotic and 11 non-anastomotic stenoses, 4 dehiscences, and 3 malacias. Independent predictors for AC were: gender male (OR: 4.18; p = 0.002), cardiac comorbidities (OR: 2.74; p = 0.009), prolonged postoperative mechanical ventilation (OR: 2.5; p = 0.02), P_aO₂/F_iO₂ < 300 mmHg at 24 h post-LT (OR: 2.48; p = 0.01), graft infection (OR: 2.16; p = 0.05), and post-LT isolation of Aspergillus spp. (OR: 2.63; p = 0.03). (4) Conclusions: In spite of advances in lung transplantation practice, the risk factors, incidence, and lethality of AC after LT remains unchanged. Graft dysfunction, an infected environment, and the need of prolonged mechanical ventilation remain an Achilles heel for AC.

Primary graft dysfunction following lung transplantation: From pathogenesis to future frontiers

Lung transplantation is the treatment of choice for patients with end-stage lung disease. Currently, just under 5000 lung transplants are performed worldwide annually. However, a major scourge leading to 90-d and 1-year mortality remains primary graft dysfunction. It is a spectrum of lung injury ranging from mild to severe depending on the level of hypoxaemia and lung injury post-transplant. This review aims to provide an in-depth analysis of the epidemiology, pathophysiology, risk factors, outcomes, and future frontiers involved in mitigating primary graft dysfunction. The current diagnostic criteria are examined alongside changes from the previous definition. We also highlight the issues surrounding chronic lung allograft dysfunction and identify the novel therapies available for ex-vivo lung perfusion. Although primary graft dysfunction remains a significant contributor to 90-d and 1-year mortality, ongoing research and development abreast with current technological advancements have shed some light on the issue in pursuit of future diagnostic and therapeutic tools.

Analysis of Donor to Recipient Pathogen Transmission in Relation to Cold Ischemic Time and Other Selected Aspects of Lung Transplantation-Single Center Experience

BACKGROUND

Infections are one of the leading causes of death in the early postoperative period after lung transplantation (LuTx).

METHODS

We analyzed 59 transplantations and culture results of the donor bronchial aspirates (DBA), graft endobronchial swabs (GES), and recipient cultures (RC) before and after the procedure (RBA). We correlated the results with a cold ischemic time (CIT), recipient intubation time, and length of stay in the hospital and intensive care unit (ICU), among others.

RESULTS

CIT of the first and second lungs were 403 and 541 min, respectively. Forty-two and eighty-three percent of cultures were positive in DBA and GES, respectively. Furthermore, positive results were obtained in 79.7% of RC and in 33.9% of RBA. Longer donor hospitalization was correlated with Gram-negative bacteria isolation in DBA. Longer CIT was associated with Gram-positive bacteria other than Staphylococcus aureus in GES and it resulted in longer recipient stay in the ICU. Furthermore, longer CIT resulted in the development of the new pathogens in RBA.

CONCLUSION

Results of GES brought more clinically relevant information than DBA. Donor hospitalization was associated with the occurrence of Gram-negative bacteria. Positive cultures of DBA, GES, and RBA were not associated with recipient death.

Favorable, arduous or fatal postoperative pathway within 90 days of lung transplantation

INTRODUCTION

The maximum gain in quality of life after lung transplantation (LT) is expected between six months and one year after LT, as the occurrence of chronic lung allograft dysfunction may mask the beneficial effects beyond one year. Thus, the postoperative period could be the cornerstone of graft success. We sought to describe the factors present before postoperative admission to the ICU and associated with favorable, arduous or fatal pathway within 90 days of LT.

MATERIALS AND METHODS

We conducted a retrospective single-center study between January 2015 and December 2020. Using multinomial regression, we assessed the demographic, preoperative and intraoperative characteristics of patients associated with favorable (duration of postoperative mechanical ventilation < 3 days and alive at Day 90), arduous (duration of postoperative mechanical ventilation ≥ 3 days and alive at Day 90) or fatal (dead at Day 90) pathway within 90 days of LT.

RESULTS

A total of 269 lung transplant patients were analyzed. Maximum graft cold ischemic time ≥ 6 h and intraoperative blood transfusion ≥ 3 packed red blood cells were associated with arduous and fatal pathway at Day 90, whereas intraoperative ECMO was strongly associated with fatal pathway.

CONCLUSION

No patient demographics influenced the postoperative pathway at Day 90. Only extrinsic factors involving graft ischemia time, intraoperative transfusion, and intraoperative ECMO determined early postoperative pathway.

Impact of the donor hepatectomy time on short-term outcomes in liver transplantation using donation after circulatory death: A review of the US national registry

BACKGROUND

During the donor hepatectomy time (dHT), defined as the time from the start of cold perfusion to the end of the hepatectomy, liver grafts have a suboptimal temperature. The aim of this study was to analyze the impact of prolonged dHT on outcomes in donation after circulatory death (DCD) liver transplantation (LT).

METHODS

Using the US national registry data between 2012 and 2020, DCD LT patients were separated into 2 groups based on their dHT: standard dHT (<42 min) and prolonged dHT (≥42 min).

RESULTS

There were 3810 DCD LTs during the study period. Median dHT was 32 min (IQR 25-41 min). Kaplan- Meier graft survival curves demonstrated inferior outcomes in the prolonged dHT group at 1-year after DCD LT compared to those in the standard dHT group (85.3% vs 89.9%; p < 0.01). Multivariate Cox proportional hazards models for 1-year graft survival identified that prolonged dHT [hazard ratio (HR) 1.46, 95% confidence interval (CI) 1.19 - 1.79], recipient age ≥ 64 years (HR 1.40, 95% CI 1.14 - 1.72), and MELD score ≥ 24 (HR 1.43, 95% CI 1.16 - 1.76) were significant predictors of 1-year graft loss. Spline analysis shows that the dHT effects on the risk for 1-year graft loss with an increase in the slope after median dHT of 32 min.

CONCLUSION

Prolonged dHTs significantly reduced graft and patient survival after DCD LT. Because dHT is a modifiable factor, donor surgeons should take on cases with caution by setting the dHT target of < 32 min. This article is protected by copyright. All rights reserved.

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.

Early Postoperative Management of Lung Transplant Recipients

The early postoperative period after lung transplantation is a critical time. Prompt recognition and treatment of primary graft dysfunction can alter long-term allograft function. Cardiovascular, gastrointestinal, renal, and hematologic derangements are common and require close management to limit their negative sequelae.

Airway complications in lung transplantation

Airway complications (ACs) after lung transplantation remain an important source of morbidity and mortality despite significant advances in the surgical technics, leading to increased cost, and decrease quality of life. The incidences of ACs after lung transplantation range from 2% to 33%, even though most transplant centers have reported rates in the range of 7% to 8%. However, the reported rate of ACs has been inconsistent as a result of a lack of standardized airway definitions and grading protocols before the recent 2018 International Society for Heart and Lung Transplantation (ISHLT) proposed consensus guidelines on ACs after lung transplantation. The ACs include stenosis, perioperative and postoperative bronchial infections, bronchial necrosis and dehiscence, excess granulation tissue, and tracheobronchomalacia (TBM). Anastomosis infection, necrosis, or dehiscence typically develops within the first month after lung transplantation. The most frequent AC after lung transplantation is bronchial stenosis. Several risk factors have been proposed to the development of ACs after lung transplantation, including surgical anastomosis techniques, hypoperfusion, infections, donor and recipient factors, immunosuppression agents, and organ preservation. ACs might be prevented by early recognition of the airway pathology, using advance medical management, and interventional bronchoscopy procedures. Balloon bronchoplasty, cryotherapy, laser photo resection, electrocautery, high-dose endobronchial brachytherapy, and bronchial stents placement are the most frequent interventional bronchoscopic procedures utilized for the management of ACs.

Lung transplantation using allografts with more than 8 hours of ischemic time: A single-institution experience

BACKGROUND

Six hours was historically regarded as the limit of acceptable ischemic time for lung allografts. However, broader sharing of donor lungs often necessitates use of allografts with ischemic time >6 hours. We characterized the association between ischemic time ≥8 hours and outcomes after lung transplantation using a contemporary cohort from a high-volume institution.

METHODS

Patients who underwent primary isolated bilateral lung transplantation between 1/2016 and 5/2020 were included. Patients bridged to transplant with extracorporeal membrane oxygenation or mechanical ventilation, and ex-vivo perfusion cases were excluded. Recipients were stratified by total allograft ischemic time <8 hours (standard) vs ≥8 hours (long). Perioperative outcomes and post-transplant survival were compared between groups.

RESULTS

Of 358 patients, 95 (26.5%) received long ischemic time (≥8 hours) lungs. Long ischemic time recipients were more likely to be male and have donation after circulatory death donors than standard ischemic time recipients. On unadjusted analysis, long and standard ischemic time recipients had similar survival, and similar rates of grade 3 primary graft dysfunction at 72 hours, extracorporeal membrane oxygenation post-transplant, acute rejection within 30 days, reintubation, and post-transplant length of stay. After adjustment, long and standard ischemic time recipients had comparable risks of mortality or graft failure.

CONCLUSIONS

In a modern cohort, use of lung allografts with "long" ischemic time ≥8 hours were associated with acceptable perioperative outcomes and post-transplant survival. Further investigation is required to better understand how broader use impacts post-lung transplant outcomes and the implications for smarter sharing under an evolving national allocation policy.

Extracorporeal membrane oxygenation in lung transplantation: Indications, techniques and results

The use of extracorporeal membrane oxygenation (ECMO) in the field of lung transplantation has rapidly expanded over the past 30 years. It has become an important tool in an increasing number of specialized centers as a bridge to transplantation and in the intra-operative and/or post-operative setting. ECMO is an extremely versatile tool in the field of lung transplantation as it can be used and adapted in different configurations with several potential cannulation sites according to the specific need of the recipient. For example, patients who need to be bridged to lung transplantation often have hypercapnic respiratory failure that may preferably benefit from veno-venous (VV) ECMO or peripheral veno-arterial (VA) ECMO in the case of hemodynamic instability. Moreover, in an intra-operative setting, VV ECMO can be maintained or switched to a VA ECMO. The routine use of intra-operative ECMO and its eventual prolongation in the post-operative period has been widely investigated in recent years by several important lung transplantation centers in order to assess the graft function and its potential protective role on primary graft dysfunction and on ischemia-reperfusion injury. This review will assess the current evidence on the role of ECMO in the different phases of lung transplantation, while analyzing different studies on pre, intra- and post-operative utilization of this extracorporeal support.

Primary graft dysfunction

PURPOSE OF REVIEW

Primary graft dysfunction (PGD) is a devastating complication in the acute postoperative lung transplant period, associated with high short-term mortality and chronic rejection. We review its definition, pathophysiology, risk factors, prevention, treatment strategies, and future research directions.

RECENT FINDINGS

New analyses suggest donation after circulatory death and donation after brain death donors have similar PGD rates, whereas donors >55 years are not associated with increased PGD risk. Recipient pretransplant diastolic dysfunction and overweight or obese recipients with predominant abdominal subcutaneous adipose tissue have increased PGD risk. Newly identified recipient biomarkers and donor and recipient genes increase PGD risk, but their clinical utility remains unclear. Mixed data still exists regarding cold ischemic time and PGD risk, and increased PGD risk with cardiopulmonary bypass remains confounded by transfusions. Portable ex vivo lung perfusion (EVLP) may prevent PGD, but its use is limited to a handful of centers. Although updates to current PGD treatment are lacking, future therapies are promising with targeted therapy and the use of EVLP to pharmacologically recondition donor lungs.

SUMMARY

There is significant progress in defining PGD and identifying its several risk factors, but effective prevention and treatment strategies are needed.

The Year in Cardiothoracic Transplantation Anesthesia: Selected Highlights from 2019

The highlights in cardiothoracic transplantation focus on the recent research pertaining to heart and lung transplantation, including expansion of the donor pool, the optimization of donors and recipients, the use of mechanical support, the perioperative and long-term outcomes in these patient populations, and the use of transthoracic echocardiography to diagnose rejection.

Portable normothermic ex-vivo lung perfusion, ventilation, and functional assessment with the Organ Care System on donor lung use for transplantation from extended-criteria donors (EXPAND): a single-arm, pivotal trial

BACKGROUND

Donor lung use for transplantation is the lowest among solid organ tranplants because of several complex and multifactorial reasons; one area that could have a substantial role is the limited capabilities of cold ischaemic storage. The aim of the EXPAND trial was to evaluate the efficacy of normothermic portable Organ Care System (OCS) Lung perfusion and ventilation on donor lung use from extended-criteria donors and donors after circulatory death, which are rarely used.

METHODS

In this single-arm, pivotal trial done in eight institutions across the USA, Germany, and Belgium, lungs from extended-criteria donors were included if fulfilling one or more of the following criteria: a ratio of partial pressure of arterial oxygen (PaO₂) to fractional concentration of oxygen inspired air (FiO₂) in the donor lung of 300 mm Hg or less; expected ischaemic time longer than 6 h; donor age 55 years or older; or lungs from donors after circulatory death that were recruited and assessed using OCS Lung. Lungs were transplanted if they showed stability of OCS Lung variables, PaO₂:FiO₂ was more than 300 mm Hg, and they were accepted by the transplanting surgeon. Patients were adult bilateral lung transplant recipients. The primary efficacy endpoint was a composite of patient survival at day 30 post-transplant and absence of The International Society for Heart & Lung Tranplantation primary-graft dysfunction grade 3 (PGD3) within 72 h post-transplantation, with a prespecified objective performance goal of 65%. The primary analysis population was all transplanted recipients. This trial is registered with ClinicalTrials.gov, number NCT01963780, and is now complete.

FINDINGS

Between Jan 23, 2014, and Oct 23, 2016, 93 lung pairs were perfused, ventilated, and assessed on the OCS Lung. 12 lungs did not meet OCS transplantation criteria so 81 lungs were suitable for transplantation. Two lungs were excluded for logistical reasons, hence 79 (87%) of eligible lungs were transplanted. The primary endpoint was achieved in 43 (54%) of 79 patients and did not meet the objective performance goal. 35 (44%) of 79 patients had PGD3 within the initial 72 h. 78 (99%) of 79 patients had survived at 30 days post-transplant. The mean number of lung graft-related serious adverse events (respiratory failure and major pulmonary-related infection) was 0·3 events per patient (SD 0·5).

INTERPRETATION

Despite missing the objective primary endpoint, the portable OCS Lung resulted in 87% donor lung use for transplantation with excellent clinical outcomes. Many lungs declined by other transplant centres were successfully transplanted using this new technology, which implies its use has the potential to increase the number of lung transplants performed worldwide. Whether similar outcomes could be obtained if these lungs were preserved on ice is unknown and remains an area for future research.

FUNDING

TransMedics Inc.

Incidence and variables associated with 30-day mortality after lung transplantation

BACKGROUND

With the introduction of the lung allocation score (LAS), sicker patients are prioritized for lung transplantation (LT). There is a lack of data regarding variables independently associated with 30-day mortality after LT.

METHODS

We queried the UNOS database for adult patients undergoing LT between 1989 and 2014. Patients with dual organ or previous transplantation and those with missing survival data were excluded. Mortality during the first 30 days after LT was the primary outcome variable.

RESULTS

The yearly trends indicate a statistically significant reduction in the 30-day mortality during the study period (P < 0.001, overall mortality: 5.5%) which has continued in the post-LAS era (P = 0. 014, overall mortality: 3.6%). Among patients with 30-day mortality, "primary non-function" (n = 118, 72.8%) was reported as the most common etiology. Transplant indication of vascular diseases, history of non-transplant cardiac or lung surgery, mean pulmonary pressures >35 mm Hg, disabled functional status, ECMO support, high LAS, ischemic time >6 hours, and blunt injury as the mechanism of donor death are independently associated with 30-day mortality.

CONCLUSION

The incidence of early mortality after LT continues to decline in the post-LAS era. Apart from the mechanism of donor death and ischemic time, early mortality appears to be primarily driven by the recipient characteristics.

Early Graft Dysfunction after Lung Transplantation

PURPOSE OF REVIEW

Primary graft dysfunction is an acute lung injury syndrome occurring immediately following lung transplantation. This review aims to provide an overview of the current understanding of PGD, including epidemiology, immunology, clinical outcomes and management.

RECENT FINDINGS

Identification of donor and recipient factors allowing accurate prediction of PGD has been actively pursued. Improved understanding of the immunology underlying PGD has spurred interest in identifying relevant biomarkers. Work in PGD prediction, severity stratification and targeted therapies continue to make progress. Donor expansion strategies continue to be pursued with ex vivo lung perfusion playing a prominent role. While care of PGD remains supportive, ECMO has established a prominent role in the early aggressive management of severe PGD.

SUMMARY

A consensus definition of PGD has allowed marked advances in research and clinical care of affected patients. Future research will lead to reliable predictive tools, and targeted therapeutics of this important syndrome.

Risk factors for infection after pediatric lung transplantation

Although infection is the leading cause of death in the first year following pediatric lung transplantation, there are limited data on risk factors for early infection. Sepsis remains under-recognized and under-reported in the early post-operative period for lung transplant recipients (LTR). We evaluated the incidence of infection and sepsis, and identified risk factors for infection in the early post-operative period in pediatric LTRs. A retrospective review of medical records of LTRs at a large quaternary-care hospital from January 2009 to March 2016 was conducted. Microbiology results on days 0-7 after transplant were obtained. Sepsis was defined using the 2005 International Pediatric Consensus Conferencecriteria. Risk factors included history of recipient and donor infection, history of multi-drug resistant (MDR) infection, nutritional status, and surgical times. Among the 98 LTRs, there were 22 (22%) with post-operative infection. Prolonged donor ischemic time ≥7 hours, cardiopulmonary bypass(CPB) time ≥340 minutes, history of MDR infection and diagnosis of cystic fibrosis were significantly associated with infection. With multivariable regression analysis, only prolonged donor ischemic time remained significant (OR 4.4, 95% CI: 1.34-14.48). Further research is needed to determine whether processes to reduce donor ischemic time could result in decreased post-transplant morbidity.

Effect of broader geographic sharing of donor lungs on lung transplant waitlist outcomes

BACKGROUND

The United States lung allocation system prioritizes allocation based on medical urgency and benefit but does not address a federal mandate for broader geographic organ sharing. It is unknown whether broader geographic sharing of donor lungs would improve lung transplant waitlist outcomes.

METHODS

A discrete event microsimulation model simulated donor lung allocation according to different geographic lung-sharing policies, including the historic local donor service area (DSA)-based policy and hypothetical policies that prioritize candidates to donors within 500-mile or 1,000-mile geographic radii. Candidate waitlist mortality, number of transplants, and 1-year survival were compared across organ allocation policies. Waitlist mortality rates were further stratified by diagnosis, Lung Allocation Score (LAS) threshold, ABO blood type, and region.

RESULTS

Under broader geographic lung sharing, the proportion of chronic obstructive pulmonary disease transplant recipients decreased, whereas the proportion of pulmonary fibrosis recipients increased. Waitlist mortality decreased with broader geographic lung sharing with a 21.3% decrease in waitlist mortality with 500-mile lung sharing and a 31.8% decrease in waitlist mortality with 1,000-mile lung sharing. The decrease in waitlist deaths occured across all U.S. geographic regions and was greatest in candidates with pulmonary fibrosis and/or high medical urgency.

CONCLUSIONS

Broader geographic sharing of donor lungs could reduce waitlist mortality, particularly among pulmonary fibrosis and high-medical-urgency candidates.

Risks associated with lung transplantation in cystic fibrosis patients

INTRODUCTION

Survival after lung transplantation lags behind outcomes of other solid organ transplants, and complications from lung transplant are the second most common cause of death in cystic fibrosis. Evolving surgical techniques, therapeutics, and perioperative management have improved short-term survival after lung transplantation, yet have not translated into significant improvement in long-term mortality. Areas covered: We review risk factors for poor long-term outcomes among patients with cystic fibrosis undergoing lung transplantation to highlight areas for improvement. This includes reasons for organ dysfunction, complications of immunosuppression, further exacerbation of extrapulmonary complications of cystic fibrosis, and quality of life. A literature search was performed using PubMed-indexed journals. Expert commentary: There are multiple medical and socioeconomic barriers that threaten long-term survival following lung transplant for patients with cystic fibrosis. An understanding of the causes of each could elucidate treatment options. There is a lack of prospective, multicenter, randomized control trials due to cost, complexity, and feasibility. Ongoing prospective studies should be reserved for the most promising interventions identified in retrospective studies in order to improve long-term outcomes.

Machine perfusion of thoracic organs

This article summarizes recent knowledge and clinical advances in machine perfusion (MP) of thoracic organs. MP of thoracic organs has gained much attention during the last decade. Clinical studies are investigating the role of MP to preserve, resuscitate, and assess heart and lungs prior to transplantation. Currently, MP of the cardiac allograft is essential in all type DCD heart transplantation while MP of the pulmonary allograft is mandatory in uncontrolled DCD lung transplantation. MP of thoracic organs also offers an exciting platform to further investigate downregulation of the innate and adaptive immunity prior to reperfusion of the allograft in recipients. MP provides a promising technology that allows pre-transplant preservation, resuscitation, assessment, repair, and conditioning of cardiac and pulmonary allografts outside the body in a near physiologic state prior to planned transplantation. Results of ongoing clinical trials are awaited to estimate the true clinical value of this new technology in advancing the field of heart and lung transplantation by increasing the total number and the quality of available organs and by further improving recipient early and long-term outcome.

ISHLT Consensus Statement on adult and pediatric airway complications after lung transplantation: Definitions, grading system, and therapeutics

Airway complications remain a major cause of morbidity and mortality after cardiothoracic transplantation. The reported incidence of airway ischemic complications varies widely, contributed to by the lack of a universally accepted grading system and standardized definitions. Furthermore, the majority of the existing classification systems fail to integrate the wide range of possible bronchial complications that may develop after lung transplant. Hence, a Working Group was created by the International Society for Heart and Lung Transplantation with the aim of elaborating a universal definition of adult and pediatric airway complications and grading system. One such area of focus is to understand the problem in the context of a more standardized consensus of classifying airway ischemia. This consensus definition will have major clinical, therapeutics, and research implications.

Contemporary Issues in Lung Transplant Allocation Practices

PURPOSE OF REVIEW

To discuss the current state of donor lung allocation in the United States, and future opportunities to increase the efficiency of donor lung allocation.

RECENT FINDINGS

The current donor lung allocation system prioritizes clinical acuity by use of the Lung Allocation Score (LAS) which has reduced waitlist mortality since its implementation in 2005. Access to donor lungs can be further improved through policy changes using broader geographic sharing, and developing new technology such as ex vivo lung perfusion to recover marginal donor lungs.

SUMMARY

The number of lung transplants in the U.S. continues to increase annually. However, the demand for donor lungs continues to be outpaced by an ever growing waitlist. Efficient allocation can be achieved through improved allocation policies and new technology.

Extracorporeal membrane oxygenation following lung transplantation: indications and survival

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is employed to rescue patients with early graft dysfunction after lung transplantation (LTx). Rates of post-LTx ECMO and subsequent outcomes have been limited to single-center reports.

METHODS

UNOS registry was queried for LTx recipients from March 2015 to March 2016; 2,001 recipients were identified and stratified by need for post-LTx ECMO. Logistic regression was used to determine variables associated with post-LTx ECMO. Cox proportional hazards modeling identified factors associated with survival. Kaplan-Meier analysis with log-rank testing was employed for survival analysis.

RESULTS

Of 2,001 recipients identified, 107 required post-LTx ECMO (5.1%). Recipients requiring ECMO were younger (56 vs 60 years, p = 0.007) and had higher body mass index (27.2 vs 25.8, p = 0.012). Recipients requiring post-LTx ECMO were more likely to have required mechanical ventilation before transplant (9.3% vs 4.9%, p = 0.049) and were more likely to have required pre-transplant ECMO (15% vs 3.7%, p < 0.001). On multivariable analysis, pre-transplant ECMO and increasing ischemic time were associated with post-LTx ECMO. Six-month survival for recipients requiring ECMO was 62.2%. On multivariable analysis, need for post-transplant dialysis was associated with mortality. Six-month survival for recipients requiring ECMO with and without dialysis was 25.8% and 86.7% (p < 0.001).

CONCLUSIONS

In a nationally representative database, ischemic time and pre-transplant ECMO and/or ventilator requirement were associated with need for post-LTx ECMO. Need for post-transplant dialysis was associated with mortality in patients requiring post-LTx ECMO. These data may permit improved prediction of graft dysfunction. Strategies to minimize renal toxicity in the perioperative phase may lead to improved early survival post-LTx.

Immune Responses to Tissue-Restricted Nonmajor Histocompatibility Complex Antigens in Allograft Rejection

Chronic diseases that result in end-stage organ damage cause inflammation, which can reveal sequestered self-antigens (SAgs) in that organ and trigger autoimmunity. The thymus gland deletes self-reactive T-cells against ubiquitously expressed SAgs, while regulatory mechanisms in the periphery control immune responses to tissue-restricted SAgs. It is now established that T-cells reactive to SAgs present in certain organs (e.g., lungs, pancreas, and intestine) are incompletely eliminated, and the dysregulation of peripheral immuneregulation can generate immune responses to SAgs. Therefore, chronic diseases can activate self-reactive lymphocytes, inducing tissue-restricted autoimmunity. During organ transplantation, donor lymphocytes are tested against recipient serum (i.e., cross-matching) to detect antibodies (Abs) against donor human leukocyte antigens, which has been shown to reduce Ab-mediated hyperacute rejection. However, primary allograft dysfunction and rejection still occur frequently. Because donor lymphocytes do not express tissue-restricted SAgs, preexisting Abs against SAgs are undetectable during conventional cross-matching. Preexisting and de novo immune responses to tissue-restricted SAgs (i.e., autoimmunity) play a major role in rejection. In this review, we discuss the evidence that supports autoimmunity as a contributor to rejection. Testing for preexisting and de novo immune responses to tissue-restricted SAgs and treatment based on immune responses after organ transplantation may improve short- and long-term outcomes after transplantation.

Lung Transplant Center Volume Ameliorates Adverse Influence of Prolonged Ischemic Time on Mortality

The influence of prolonged ischemic time on outcomes after lung transplant is controversial, but no research has investigated ischemic time in the context of center volume. We used data from the United Network for Organ Sharing to estimate the influence of ischemic time on patient survival conditional on center volume in the post-lung allocation score era (2005-2015). The analytic sample included 14 877 adult lung transplant recipients, of whom 12 447 were included in multivariable survival analysis. Patient survival was improved in high-volume centers compared with low-volume centers (log-rank test p = 0.001), although mean ischemic times were longer at high-volume centers (5.16 ± 1.70 h vs. 4.83 ± 1.63 h, p < 0.001). Multivariable Cox proportional hazards regression stratified by transplant center found an adverse influence of longer ischemic time at low-volume centers but not at high-volume centers. At centers performing 50 transplants in the period 2005-2015, for example, 8 versus 6 h of ischemia were associated with an 18.9% (95% confidence interval 6.5-32.7%; p < 0.001) greater mortality hazard, whereas at centers performing 350 transplants in this period, no differences in survival by ischemic time were predicted. Despite longer mean ischemic time at high-volume transplant centers, these centers had favorable patient outcomes and no adverse survival implications of prolonged ischemia.

Influence of graft ischemic time on survival in children with cystic fibrosis after lung transplantation

BACKGROUND

The influence of graft ischemic time on survival after lung transplantation (LTx) in children with cystic fibrosis (CF) is not well studied.

METHODS

The United Network for Organ Sharing (UNOS) database was queried from May 2005 to September 2013 to examine the impact of ischemic time of <4, 4-6, and >6 hr in pediatric LTx recipients with CF.

RESULTS

One hundred and ninety-nine patients with CF under 18 years of age that were first-time LTx recipients from cadaveric donors were included in the analysis. Compared to 4-6 hr, univariate analysis showed a significant increase in mortality hazard with an ischemic time of <4 hr (HR = 2.407; 95%CI: 1.292, 4.485; P = 0.006) but not >6 hr (HR = 1.350; 95%CI: 0.796, 2.290; P = 0.266). A Kaplan-Meier plot demonstrated the highest survival with 4-6 hr (Log-rank test P = 0.018) of ischemic time. Multivariate Cox model confirmed a significantly higher mortality risk with <4 hr (HR = 2.388; 95%CI: 1.169, 4.764; P = 0.014) and not >6 hr (HR = 1.407; 95%CI: 0.760, 2.605; P = 0.278) in relation to 4-6 hr. Sub-analysis examining ischemic time and the hazard of bronchiolitis obliterans syndrome with death as a competing risk found no significant differences in the hazard of this outcome across the three ischemic time categories.

CONCLUSIONS

Ischemic time of 4-6 hr was associated with the highest long-term survival in first-time pediatric LTx recipients with CF, with ischemic time <4 hr related to diminished survival. Pediatr Pulmonol. 2016; 51:908-913. © 2016 Wiley Periodicals, Inc.

Lung transplantation at Duke

Lung transplantation represents the gold-standard therapy for patients with end-stage lung disease. Utilization of this therapy continues to rise. The Lung Transplant Program at Duke University Medical Center was established in 1992, and since that time has grown to one of the highest volume centers in the world. The program to date has performed over 1,600 lung transplants. This report represents an up-to-date review of the practice and management strategies employed for safe and effective lung transplantation at our center. Specific attention is paid to the evaluation of candidacy for lung transplantation, donor selection, surgical approach, and postoperative management. These evidence-based strategies form the foundation of the clinical transplantation program at Duke.