Contemporary trends in PGD incidence, outcomes, and therapies

Analysis of Perioperative Factors Leading to Postoperative Pulmonary Complications, Graft Injury and Increased Postoperative Mortality in Lung Transplantation

OBJECTIVES

Postoperative complications such as postoperative pulmonary complications (PPCs) and other organ complications are associated with increased morbidity and mortality after successful lung transplantation and have a detrimental effect on patient recovery. The aim of this study was to investigate perioperative risk factors for in-hospital mortality and postoperative complications with a focus on PPC and graft injury in patients undergoing lung transplantation DESIGN: Single-center retrospective cohort study of 173 patients undergoing lung transplantation SETTING: University Hospital, Medical Center Freiburg.

MAIN RESULTS

In the stepwise multivariate regression analysis, donor age >60 years (odds ratio [OR], 1.85; 95% confidence interval [CI], 1.27-2.81), intraoperative extracorporeal membrane oxygenation (OR, 2.4; 95% CI, 1.7-3.3), transfusion of >4 red blood cell concentrates (OR, 3.1; 95% CI, 1.82-5.1), mean pulmonary artery pressure of >30 mmHg at the end of surgery (OR, 3.5; 95% CI, 2-6.3), the occurrence of postoperative graft injury (OR, 4.1; 95% CI, 2.8-5.9), PPCs (OR, 2.1; 95% CI, 1.7-2.6), sepsis (OR, 4.5; 95% CI, 2.8-7.3), and Kidney disease Improving Outcome grading system stage 3 acute renal failure (OR, 4.3; 95% CI, 2.4-7.7) were associated with increased in hospital mortality, whereas patients with chronic obstructive pulmonary disease had a lower in-hospital mortality (OR, 1.6; 95% CI, 1.4-1.9). The frequency and number of PPCs correlated with postoperative mortality.

CONCLUSIONS

Clinical management and risk stratification focusing on the underlying identified factors that could help to improve patient outcomes.

Case Report: Optimal utilization of marginal lung allografts by considering donor-recipient PGD risk compatibility and by mitigating allograft and recipient inflammatory risk

Reducing the risk of high-grade primary graft dysfunction (PGD) is vital to achieve acceptable short- and long-term outcomes for recipients following lung transplantation. However, the utilization of injured lung allografts, which may confer a higher risk of PGD, must be considered due to the disparity between the increasing number of patients requiring lung transplantation and the limited donor pool. We describe a case in which highly marginal lung allografts were utilized with a good post-transplant outcome. Donor-recipient PGD risk compatibility was taken into consideration. Normothermic ex vivo lung perfusion (EVLP) was utilized to functionally assess the allografts. A second cold ischemia time following EVLP was avoided by converting the EVLP mode to a hypothermic oxygenated perfusion setup from which the lungs were transplanted directly. We attempted to mitigate lung ischemia-reperfusion injury in the recipient by employing cytokine adsorption both during the EVLP and intraoperatively during the implant procedure. In this case report, we describe our hypothermic oxygenated perfusion setup on EVLP for the first time. Furthermore, we describe the utilization of cytokine adsorption in two phases of the same transplant process.

Heparanase-induced endothelial glycocalyx degradation exacerbates lung ischemia/reperfusion injury in male mice

The endothelial glycocalyx (eGC) is a carbohydrate-rich layer on the vascular endothelium, and its damage can lead to endothelial and organ dysfunction. Heparanase (HPSE) degrades the eGC in response to cellular stress, but its role in organ dysfunction remains unclear. This study investigates HPSE's role in lung ischemia-reperfusion (I/R) injury. A left lung hilar occlusion model was used in B6 wildtype (WT) and HPSE genetic knockout (-/-) mice to induce I/R injury in vivo. The left lungs were ischemic for 1 h followed by reperfusion for 4 h prior to investigations of lung function and eGC status. Data were compared between uninjured lungs and I/R-injured lungs in WT and HPSE-/- mice. WT lungs showed significant functional impairment after I/R injury, whereas HPSE-/- lungs did not. Inhibition or knockout of HPSE prevented eGC damage, inflammation, and cellular migration after I/R injury by reducing matrix metalloproteinase activities. HPSE-/- mice exhibited compensatory regulation of related gene expressions. HPSE facilitates eGC degradation leading to inflammation and impaired lung function after I/R injury. HPSE may be a therapeutic target to attenuate graft damage in lung transplantation.

Outcomes of single-lung retransplantation after double-lung transplantation

OBJECTIVE

To compare outcomes of single-lung retransplantation (SLRTx) and double-lung retransplantation (DLRTx) after an initial double-lung transplantation.

METHODS

The Organ Procurement and Transplantation Network/United Network for Organ Sharing database between May 2005 and December 2022 was retrospectively analyzed. Multiorgan transplantations, repeated retransplantations, and lung retransplantations when the status of the initial transplantation was unknown were excluded.

RESULTS

A total of 891 patients were included in the analysis, included 698 (78.3%) with DLRTx and 193 (21.7%) with SLRTx. The mean lung allocation score was higher in the DLRTx group (59.6 ± 20.7 vs 55.1 ± 19.3; P = .007). The use of extracorporeal membrane oxygenation (ECMO) bridge to lung transplantation was similar in the 2 groups (P = .125), as was waitlist time (P = .610). The need for mechanical ventilation (54.6% vs 35.8%; P = .005) and ECMO (17.9% vs 9.0%; P = .069) at 72 hours post-transplantation was greater in the DLRTx group. However, median post-transplantation hospital stay (21.5 [interquartile range (IQR), 12-35] days versus 20 [IQR, 12-35] days; P = .119) and in-hospital mortality (10.9% [n = 76/698] vs 12.4% [n = 24/193]; P = .547) were comparable in the 2 groups. Long-term survival was significantly better in the DLRTx group (P < .001, log-rank test). In the propensity score-weighted multivariable model, the DLRTx group had 28% lower risk of mortality at any point during follow-up compared to the SLRTx group (hazard ratio, 0.72; 95% confidence interval, 0.57-0.91; P = .006).

CONCLUSIONS

The less invasiveness of single-lung transplantation in the retransplantation setting has minimal short-term benefit and is associated with significantly worse long-term survival. Double-lung retransplantation should remain the standard for lung retransplantation after initial double-lung transplantation.

Extreme elevations of donor-derived cell-free DNA increases the risk of chronic lung allograft dysfunction and death, even without clinical manifestations of disease

BACKGROUND

Lung transplant recipients are traditionally monitored with pulmonary function testing (PFT) and lung biopsy to detect post-transplant complications and guide treatment. Plasma donor-derived cell free DNA (dd-cfDNA) is a novel molecular approach of assessing allograft injury, including subclinical allograft dysfunction. The aim of this study was to determine if episodes of extreme molecular injury (EMI) in lung transplant recipients increases the risk of chronic lung allograft dysfunction (CLAD) or death.

METHODS

This multicenter prospective cohort study included 238 lung transplant recipients. Serial plasma samples were collected for dd-cfDNA measurement by shotgun sequencing. EMI was defined as a dd-cfDNA above the third quartile of levels observed for acute rejection (dd-cfDNA level of ≥5% occurring after 45 days post-transplant). EMI was categorized as Secondary if associated with co-existing acute rejection, infection or PFT decline; or Primary if not associated with these conditions.

RESULTS

EMI developed in 16% of patients at a median 343.5 (IQR: 177.3-535.5) days post-transplant. Over 50% of EMI episodes were classified as Primary. EMI was associated with an increased risk of severe CLAD or death (HR: 2.78, 95% CI: 1.26-6.22, p = 0.012). The risk remained consistent for the Primary EMI subgroup (HR: 2.34, 95% CI 1.18-4.85, p = 0.015). Time to first EMI episode was a significant predictor of the likelihood of developing CLAD or death (AUC=0.856, 95% CI=0.805-0.908, p < 0.001).

CONCLUSIONS

Episodes of EMI in lung transplant recipients are often isolated and may not be detectable with traditional clinical monitoring approaches. EMI is associated with an increased risk of severe CLAD or death, independent of concomitant transplant complications.

CD94+ natural killer cells potentiate pulmonary ischaemia-reperfusion injury

BACKGROUND

Pulmonary ischaemia-reperfusion injury (IRI) is a major contributor to poor lung transplant outcomes. We recently demonstrated a central role of airway-centred natural killer (NK) cells in mediating IRI; however, there are no existing effective therapies for directly targeting NK cells in humans.

METHODS

We hypothesised that a depleting anti-CD94 monoclonal antibody (mAb) would provide therapeutic benefit in mouse and human models of IRI based on high levels of KLRD1 (CD94) transcripts in bronchoalveolar lavage samples from lung transplant patients.

RESULTS

We found that CD94 is highly expressed on mouse and human NK cells, with increased expression during IRI. Anti-mouse and anti-human mAbs against CD94 showed effective NK cell depletion in mouse and human models and blunted lung damage and airway epithelial killing, respectively. In two different allogeneic orthotopic lung transplant mouse models, anti-CD94 treatment during induction reduced early lung injury and chronic inflammation relative to control therapies. Anti-CD94 did not increase donor antigen-presenting cells that could alter long-term graft acceptance.

CONCLUSIONS

Lung transplant induction regimens incorporating anti-CD94 treatment may safely improve early clinical outcomes.

Mitigating the risk of inflammatory type primary graft dysfunction by applying an integrated approach to assess, modify and match risk factors in lung transplantation

Long-term outcome following lung transplantation remains one of the poorest of all solid organ transplants with a 1- and 5-year survival of 85% and 59% respectively for adult lung transplant recipients and with 50% of patients developing chronic lung allograft dysfunction (CLAD) in the first 5 years following transplant. Reducing the risk of inflammatory type primary graft dysfunction (PGD) is vital for improving both short-term survival following lung transplantation and long-term outcome due to the association of early inflammatory-mediated damage to the allograft and the risk of CLAD. PGD has a multifactorial aetiology and high-grade inflammatory-type PGD is the result of cumulative insults that may be incurred in one or more of the three variables of the transplantation continuum: the donor lungs, the recipient and intraoperative process. We set out a conceptual framework which uses a fully integrated approach to this transplant continuum to attempt to identify and, where possible, modify specific donor, recipient and intraoperative PGD risk with the goal of reducing inflammatory-type PGD risk for an individual recipient. We also consider the concept and risk-benefit of matching lung allografts and recipients on the basis of donor and recipient PGD-risk compatibility. The use of ex vivo lung perfusion (EVLP) and the extended preservation of lung allografts on EVLP will be explored as safe, non-injurious EVLP may enable extensive inflammatory testing of specific donor lungs and has the potential to provide a platform for targeted therapeutic interventions on lung allografts.

Cathepsin C from extracellular histone-induced M1 alveolar macrophages promotes NETosis during lung ischemia-reperfusion injury

Primary graft dysfunction (PGD) is a severe form of acute lung injury resulting from lung ischemia/reperfusion injury (I/R) in lung transplantation (LTx), associated with elevated post-transplant morbidity and mortality rates. Neutrophils infiltrating during reperfusion are identified as pivotal contributors to lung I/R injury by releasing excessive neutrophil extracellular traps (NETs) via NETosis. While alveolar macrophages (AMs) are involved in regulating neutrophil chemotaxis and infiltration, their role in NETosis during lung I/R remains inadequately elucidated. Extracellular histones constitute the main structure of NETs and can activate AMs. In this study, we confirmed the significant involvement of extracellular histone-induced M1 phenotype of AMs (M1-AMs) in driving NETosis during lung I/R. Using secretome analysis, public protein databases, and transwell co-culture models of AMs and neutrophils, we identified Cathepsin C (CTSC) derived from AMs as a major mediator in NETosis. Further elucidating the molecular mechanisms, we found that CTSC induced NETosis through a pathway dependent on NADPH oxidase-mediated production of reactive oxygen species (ROS). CTSC could significantly activate p38 MAPK, resulting in the phosphorylation of the NADPH oxidase subunit p47phox, thereby facilitating the trafficking of cytoplasmic subunits to the cell membrane and activating NADPH oxidase. Moreover, CTSC up-regulated and activated its substrate membrane proteinase 3 (mPR3), resulting in an increased release of NETosis-related inflammatory factors. Inhibiting CTSC revealed great potential in mitigating NETosis-related injury during lung I/R. These findings suggests that CTSC from AMs may be a crucial factor in mediating NETosis during lung I/R, and targeting CTSC inhition may represent a novel intervention for PGD in LTx.

Ex Vivo Lung Perfusion and Primary Graft Dysfunction Following Lung Transplantation: A Contemporary United Network for Organ Sharing Database Analysis

Background: Primary graft dysfunction (PGD) has detrimental effects on recipients following lung transplantation. Here, we determined the contemporary trends of PGD in a national database, factors associated with the development of PGD grade 3 (PGD3) and ex vivo lung perfusion's (EVLP) effect on this harmful postoperative complication. Methods: The United Network for Organ Sharing database was queried from 2015 to 2023, and recipients were stratified into No-PGD, PGD1/2, or PGD3. The groups were analyzed with comparative statistics, and survival was determined with Kaplan-Meier methods. Multivariable Cox regression was used to determine factors associated with increased mortality. PGD3 recipients were then stratified based on EVLP use prior to transplantation, and a 3:1 propensity match was performed to determine outcomes following transplantation. Finally, logistic regression models based on select criteria were used to determine risk factors associated with the development of PGD3 and mortality within 1 year. Results: A total of 21.4% of patients were identified as having PGD3 following lung transplant. Those with PGD3 suffered significantly worse perioperative morbidity, mortality, and had worse long-term survival. PGD3 was also independently associated with increased mortality. Matched EVLP PGD3 recipients had significantly higher use of ECMO postoperatively; however, they did not suffer other significant morbidity or mortality as compared to PGD3 recipients without EVLP use. Importantly, EVLP use prior to transplantation was significantly associated with decreased likelihood of PGD3 development, while having no significant association with early mortality. Conclusions: EVLP is associated with decreased PGD3 development, and further optimization of this technology is necessary to expand the donor pool.

Early Extubation: Who Qualifies Postoperatively in Lung Transplantation?

INTRODUCTION

Early extubation has been adopted in many settings within cardiothoracic surgery, with several advantages for patients. We sought to determine the association of timing of extubation in lung transplant recipients' short- and long-term outcomes.

METHODS

Adult, primary lung transplants were identified from the United Network for Organ Sharing database. Recipients were stratified based on the duration of postoperative ventilation: 1) None (NV); 2) <5 Days (<5D); and 3) 5+ Days (5+D). Comparative statistics were performed, and both unadjusted and adjusted survival were analyzed with Kaplan-Meier Methods and a Cox proportional hazard model. A multivariable model including recipient, donor, and transplant characteristics was created to examine factors associated with NV.

RESULTS

28,575 recipients were identified (NV = 960, <5D = 21,959, 5+D = 5656). The NV group had shorter median length of stay (P < 0.01) and lower incidence of postoperative dialysis (P < 0.01). The NV and <5D groups had similar survival, while 5+D recipients had decreased survival (P < 0.01). The multivariable model demonstrated increased donor BMI, center volume, ischemic time, single lung transplant, and transplantation between 2011 and 2015 were associated with NV (P < 0.01 for all). Use of donation after cardiac death donors and transplantation between 2016 and 2021 was associated with postoperative ventilator use.

CONCLUSIONS

Patients extubated early after lung transplantation have a shorter median length of stay without an associated increase in mortality. While not all patients are appropriate for earlier extubation, it is possible to extubate patients early following lung transplant. Further efforts are necessary to help expand this practice and ensure its' success for recipients.

Driving pressure association with mortality in post-lung transplant patients: A prospective observational study

OBJECTIVE

To investigate the association between driving pressure (ΔP) and 90-day mortality in patients following lung transplantation (LTx) in patients who developed primary graft dysfunction (PGD).

METHODS

This prospective, observational study involved consecutive patients who, following LTx, were admitted to our intensive care unit (ICU) from January 2022 to January 2023. Patients were separated into two groups according to ΔP at time of admission (i.e., low, ≤15 cmH2O or high, >15 cmH2O). Postoperative outcomes were compared between groups.

RESULTS

In total, 104 patients were involved in the study, and of these, 69 were included in the low ΔP group and 35 in the high ΔP group. Kaplan-Meier analysis of 90-day mortality showed a statistically significant difference between groups with survival better in the low ΔP group compared with the high ΔP group. According to Cox proportional regression model, the variables independently associated with 90-day mortality were ΔP and pneumonia. Significantly more patients in the high ΔP group than the low ΔP group had PGD grade 3 (PGD3), pneumonia, required tracheostomy, and had prolonged postoperative extracorporeal membrane oxygenation (ECMO) time, postoperative ventilator time, and ICU stay.

CONCLUSIONS

Driving pressure appears to have the ability to predict PGD3 and 90-day mortality of patients following LTx. Further studies are required to confirm our results.

Proteomic Analysis of Primary Graft Dysfunction in Porcine Lung Transplantation Reveals Alveolar-Capillary Barrier Changes Underlying the High Particle Flow Rate in Exhaled Breath

Primary graft dysfunction (PGD) remains a challenge for lung transplantation (LTx) recipients as a leading cause of poor early outcomes. New methods are needed for more detailed monitoring and understanding of the pathophysiology of PGD. The measurement of particle flow rate (PFR) in exhaled breath is a novel tool to monitor and understand the disease at the proteomic level. In total, 22 recipient pigs underwent orthotopic left LTx and were evaluated for PGD on postoperative day 3. Exhaled breath particles (EBPs) were evaluated by mass spectrometry and the proteome was compared to tissue biopsies and bronchoalveolar lavage fluid (BALF). Findings were confirmed in EBPs from 11 human transplant recipients. Recipients with PGD had significantly higher PFR [686.4 (449.7-8,824.0) particles per minute (ppm)] compared to recipients without PGD [116.6 (79.7-307.4) ppm, p = 0.0005]. Porcine and human EBP proteins recapitulated proteins found in the BAL, demonstrating its utility instead of more invasive techniques. Furthermore, adherens and tight junction proteins were underexpressed in PGD tissue. Histological and proteomic analysis found significant changes to the alveolar-capillary barrier explaining the high PFR in PGD. Exhaled breath measurement is proposed as a rapid and non-invasive bedside measurement of PGD.

Recipient Outcomes With Extended Criteria Donors Using Advanced Heart Preservation: An Analysis of the GUARDIAN-Heart Registry

BACKGROUND

The prevalence of end-stage heart failure and patients who could benefit from heart transplantation requires an expansion of the donor pool, relying on the transplant community to continually re-evaluate and expand the use of extended criteria donor organs. Introduction of new technologies such as the Paragonix SherpaPak Cardiac Transport System aids in this shift. We seek to analyze the impact of the SherpaPak system on recipient outcomes who receive extended criteria organs in the GUARDIAN-Heart Registry.

METHODS

Between October 2015 and December 2022, 1,113 adults from 15 US centers receiving donor hearts utilizing either SherpaPak (n = 560) or conventional ice storage (ice, n = 453) were analyzed from the GUARDIAN-Heart Registry using summary statistics. A previously published set of criteria was used to identify extended criteria donors, which included 193 SherpaPak and 137 ice.

RESULTS

There were a few baseline differences among recipients in the 2 cohorts; most notably, IMPACT scores, distance traveled, and total ischemic time were significantly greater in SherpaPak, and significantly more donor hearts in the SherpaPak cohort had >4 hours total ischemia time. Posttransplant mechanical circulatory support utilization (SherpaPak 22.3% vs ice 35.0%, p = 0.012) and new extracorporeal membrane oxygenation/ventricular assist device (SherpaPak 7.8% vs ice 15.3%, p = 0.033) was significantly reduced, and the rate of severe primary graft dysfunction (SherpaPak 6.2% vs ice 13.9%, p = 0.022) was significantly reduced by over 50% in hearts preserved using SherpaPak. One-year survival between cohorts was similar (SherpaPak 92.9% vs ice 89.6%, p = 0.27).

CONCLUSIONS

This subgroup analysis demonstrates that SherpaPak can be safely used to utilize extended criteria donors with low severe PGD rates.

Temporal correlation between postreperfusion complement deposition and severe primary graft dysfunction in lung allografts

Growing evidence implicates complement in the pathogenesis of primary graft dysfunction (PGD). We hypothesized that early complement activation postreperfusion could predispose to severe PGD grade 3 (PGD-3) at 72 hours, which is associated with worst posttransplant outcomes. Consecutive lung transplant patients (n = 253) from January 2018 through June 2023 underwent timed open allograft biopsies at the end of cold ischemia (internal control) and 30 minutes postreperfusion. PGD-3 at 72 hours occurred in 14% (35/253) of patients; 17% (44/253) revealed positive C4d staining on postreperfusion allograft biopsy, and no biopsy-related complications were encountered. Significantly more patients with PGD-3 at 72 hours had positive C4d staining at 30 minutes postreperfusion compared with those without (51% vs 12%, P < .001). Conversely, patients with positive C4d staining were significantly more likely to develop PGD-3 at 72 hours (41% vs 8%, P < .001) and experienced worse long-term outcomes. In multivariate logistic regression, positive C4d staining remained highly predictive of PGD-3 (odds ratio 7.92, 95% confidence interval 2.97-21.1, P < .001). Hence, early complement deposition in allografts is highly predictive of PGD-3 at 72 hours. Our data support future studies to evaluate the role of complement inhibition in patients with early postreperfusion complement activation to mitigate PGD and improve transplant outcomes.

Development and validation of primary graft dysfunction predictive algorithm for lung transplant candidates

BACKGROUND

Primary graft dysfunction (PGD) is the leading cause of early morbidity and mortality after lung transplantation. Accurate prediction of PGD risk could inform donor approaches and perioperative care planning. We sought to develop a clinically useful, generalizable PGD prediction model to aid in transplant decision-making.

METHODS

We derived a predictive model in a prospective cohort study of subjects from 2012 to 2018, followed by a single-center external validation. We used regularized (lasso) logistic regression to evaluate the predictive ability of clinically available PGD predictors and developed a user interface for clinical application. Using decision curve analysis, we quantified the net benefit of the model across a range of PGD risk thresholds and assessed model calibration and discrimination.

RESULTS

The PGD predictive model included distance from donor hospital to recipient transplant center, recipient age, predicted total lung capacity, lung allocation score (LAS), body mass index, pulmonary artery mean pressure, sex, and indication for transplant; donor age, sex, mechanism of death, and donor smoking status; and interaction terms for LAS and donor distance. The interface allows for real-time assessment of PGD risk for any donor/recipient combination. The model offers decision-making net benefit in the PGD risk range of 10% to 75% in the derivation centers and 2% to 10% in the validation cohort, a range incorporating the incidence in that cohort.

CONCLUSION

We developed a clinically useful PGD predictive algorithm across a range of PGD risk thresholds to support transplant decision-making, posttransplant care, and enrich samples for PGD treatment trials.

Disturbed sleep after lung transplantation is associated with worse patient-reported outcomes and chronic lung allograft dysfunction

Many lung transplant recipients fail to derive the expected improvements in functioning, HRQL, or long-term survival. Sleep may represent an important, albeit rarely examined, factor influencing lung transplant outcomes. Within a larger cohort study, 141 lung transplant recipients completed the Medical Outcomes Study (MOS) Sleep Scale along with a broader survey of patient-reported outcome (PRO) measures and frailty assessment. MOS Sleep yields the Sleep Problems Index (SPI); we also derived an insomnia-specific subscale. Potential perioperative predictors of disturbed sleep and time to chronic lung allograft dysfunction (CLAD) and death were derived from medical records. We investigated associations between perioperative predictors on SPI and Insomnia and associations between SPI and Insomnia on PROs and frailty by linear regressions, adjusting for age, sex, and lung function. We evaluated the associations between SPI and Insomnia on time to CLAD and death using Cox models, adjusting for age, sex, and transplant indication. Post-transplant hospital length of stay >30 days was associated with worse sleep by SPI and insomnia (SPI: p=0.01; Insomnia p=0.02). Worse sleep by SPI and insomnia was associated with worse depression, cognitive function, HRQL, physical disability, health utilities, and Fried Frailty Phenotype frailty (all p<0.01). Those in the worst quartile of SPI and insomnia exhibited increased risk of CLAD (HR 2.18; 95%CI: 1.22-3.89 ; p=0.01 for SPI and HR 1.96; 95%CI 1.09-3.53; p=0.03 for insomnia). Worsening in SPI but not insomnia was also associated with mortality (HR: 1.29; 95%CI: 1.05-1.58; p=0.01). Poor sleep after lung transplant may be a novel predictor of patient reported outcomes, frailty, CLAD, and death with potentially important screening and treatment implications.

The Impact of Donor Smoking on Primary Graft Dysfunction and Mortality after Lung Transplantation

Rationale: Primary graft dysfunction (PGD) is the leading cause of early morbidity and mortality after lung transplantation. Prior studies implicated proxy-defined donor smoking as a risk factor for PGD and mortality. Objectives: We aimed to more accurately assess the impact of donor smoke exposure on PGD and mortality using quantitative smoke exposure biomarkers. Methods: We performed a multicenter prospective cohort study of lung transplant recipients enrolled in the Lung Transplant Outcomes Group cohort between 2012 and 2018. PGD was defined as grade 3 at 48 or 72 hours after lung reperfusion. Donor smoking was defined using accepted thresholds of urinary biomarkers of nicotine exposure (cotinine) and tobacco-specific nitrosamine (4-[methylnitrosamino]-1-[3-pyridyl]-1-butanol [NNAL]) in addition to clinical history. The donor smoking-PGD association was assessed using logistic regression, and survival analysis was performed using inverse probability of exposure weighting according to smoking category. Measurements and Main Results: Active donor smoking prevalence varied by definition, with 34-43% based on urinary cotinine, 28% by urinary NNAL, and 37% by clinical documentation. The standardized risk of PGD associated with active donor smoking was higher across all definitions, with an absolute risk increase of 11.5% (95% confidence interval [CI], 3.8% to 19.2%) by urinary cotinine, 5.7% (95% CI, -3.4% to 14.9%) by urinary NNAL, and 6.5% (95% CI, -2.8% to 15.8%) defined clinically. Donor smoking was not associated with differential post-lung transplant survival using any definition. Conclusions: Donor smoking associates with a modest increase in PGD risk but not with increased recipient mortality. Use of lungs from smokers is likely safe and may increase lung donor availability. Clinical trial registered with www.clinicaltrials.gov (NCT00552357).

Short airway telomeres are associated with primary graft dysfunction and chronic lung allograft dysfunction

Primary graft dysfunction (PGD) is a major risk factor for chronic lung allograft dysfunction (CLAD) following lung transplantation, but the mechanisms linking these pathologies are poorly understood. We hypothesized that the replicative stress induced by PGD would lead to erosion of telomeres, and that this telomere dysfunction could potentiate CLAD. In a longitudinal cohort of 72 lung transplant recipients with >6 years median follow-up time, we assessed tissue telomere length, PGD grade, and freedom from CLAD. Epithelial telomere length and fibrosis-associated gene expression were assessed on endobronchial biopsies taken at 2 to 4 weeks post-transplant by TeloFISH assay and nanoString digital RNA counting. Negative-binomial mixed-effects and Cox-proportional hazards models accounted for TeloFISH staining batch effects and subject characteristics including donor age. Increasing grade of PGD severity was associated with shorter airway epithelial telomere lengths (p = 0.01). Transcriptomic analysis of fibrosis-associated genes showed alteration in fibrotic pathways in airway tissue recovering from PGD, while telomere dysfunction was associated with inflammation and impaired remodeling. Shorter tissue telomere length was in turn associated with increased CLAD risk, with a hazard ratio of 1.89 (95% CI 1.16-3.06) per standard deviation decrease in airway telomere length, after adjusting for subject characteristics. PGD may accelerate telomere dysfunction, potentiating immune responses and dysregulated repair. Epithelial cell telomere dysfunction may represent one of several mechanisms linking PGD to CLAD.

The role of lung-restricted autoantibodies in the development of primary and chronic graft dysfunction

Lung transplantation is a life-saving treatment for both chronic end-stage lung diseases and acute respiratory distress syndrome, including those caused by infectious agents like COVID-19. Despite its increasing utilization, outcomes post-lung transplantation are worse than other solid organ transplants. Primary graft dysfunction (PGD)-a condition affecting more than half of the recipients post-transplantation-is the chief risk factor for post-operative mortality, transplant-associated multi-organ dysfunction, and long-term graft loss due to chronic rejection. While donor-specific antibodies targeting allogenic human leukocyte antigens have been linked to transplant rejection, the role of recipient's pre-existing immunoglobulin G autoantibodies against lung-restricted self-antigens (LRA), like collagen type V and k-alpha1 tubulin, is less understood in the context of lung transplantation. Recent studies have found an increased risk of PGD development in lung transplant recipients with LRA. This review will synthesize past and ongoing research-utilizing both mouse models and human subjects-aimed at unraveling the mechanisms by which LRA heightens the risk of PGD. Furthermore, it will explore prospective approaches designed to mitigate the impact of LRA on lung transplant patients.

Lung transplantation in pulmonary sarcoidosis

Sarcoidosis is a systemic inflammatory disease of unknown etiology and variable clinical course. Pulmonary sarcoidosis is the most common presentation and accounts for most morbidity and mortality related to sarcoidosis. While sarcoidosis generally has good outcomes, few patients experience chronic disease. A minority of patients progress to a specific phenotype of sarcoidosis referred to advanced pulmonary sarcoidosis (APS) which includes advanced fibrosis, pulmonary hypertension and respiratory failure, leading to high morbidity and mortality. In patients with advanced disease despite medical therapy, lung transplantation may be the last viable option for improvement in quality of life. Though post-transplant survival is similar to that of other end-stage lung diseases, it is imperative that patients are evaluated and referred early to transplant centers with experience in APS. A multidisciplinary approach and clinical experience are crucial in detecting the optimal timing of referral, initiating comprehensive transplantation evaluation and listing, discussing surgical approach, and managing perioperative and post-transplant care. This review article seeks to address these aspects of lung transplantation in APS.

Retrospective analysis of factors associated with outcome in veno-venous extra-corporeal membrane oxygenation

BACKGROUND

The outcome of Veno-Venous Extracorporeal Membrane Oxygenation (VV-ECMO) in acute respiratory failure may be influenced by patient-related factors, center expertise and modalities of mechanical ventilation (MV) during ECMO. We determined, in a medium-size ECMO center in Switzerland, possible factors associated with mortality during VV-ECMO for acute respiratory failure of various etiologies.

METHODS

We retrospectively analyzed all patients treated with VV-ECMO in our University Hospital from 2012 to 2019 (pre-COVID era). Demographic variables, severity scores, MV duration before ECMO, pre and on-ECMO arterial blood gases and respiratory variables were collected. The primary outcome was ICU mortality. Data were compared between survivors and non-survivors, and factors associated with mortality were assessed in univariate and multivariate analyses.

RESULTS

Fifty-one patients (33 ARDS, 18 non-ARDS) were included. ICU survival was 49% (ARDS, 39%; non-ARDS 67%). In univariate analyses, a higher driving pressure (DP) at 24h and 48h on ECMO (whole population), longer MV duration before ECMO and higher DP at 24h on ECMO (ARDS patients), were associated with mortality. In multivariate analyses, ECMO indication, higher DP at 24h on ECMO and, in ARDS, longer MV duration before ECMO, were independently associated with mortality.

CONCLUSIONS

DP on ECMO and longer MV duration before ECMO (in ARDS) are major, and potentially modifiable, factors influencing outcome during VV-ECMO.

Primary graft dysfunction after lung transplantation

PURPOSE OF REVIEW

Primary graft dysfunction (PGD) is a clinical syndrome occurring within the first 72 h after lung transplantation and is characterized clinically by progressive hypoxemia and radiographically by patchy alveolar infiltrates. Resulting from ischemia-reperfusion injury, PGD represents a complex interplay between donor and recipient immunologic factors, as well as acute inflammation leading to alveolar cell damage. In the long term, chronic inflammation invoked by PGD can contribute to the development of chronic lung allograft dysfunction, an important cause of late mortality after lung transplant.

RECENT FINDINGS

Recent work has aimed to identify risk factors for PGD, focusing on donor, recipient and technical factors both inherent and potentially modifiable. Although no PGD-specific therapy currently exists, supportive care remains paramount and early initiation of ECMO can improve outcomes in select patients. Initial success with ex-vivo lung perfusion platforms has been observed with respect to decreasing PGD risk and increasing lung transplant volume; however, the impact on survival is not well delineated.

SUMMARY

This review will summarize the pathogenesis and clinical features of PGD, as well as highlight treatment strategies and emerging technologies to mitigate PGD risk in patients undergoing lung transplantation.