Longitudinal Lower Airway Microbial Signatures of Acute Cellular Rejection in Lung Transplantation.

Rationale: Acute cellular rejection (ACR) after lung transplantation is a leading risk factor for chronic lung allograft dysfunction. Prior studies have demonstrated dynamic microbial changes occurring within the allograft and gut that influence local adaptive and innate immune responses. However, the lung microbiome's overall impact on ACR risk remains poorly understood. Objective: To evaluate whether temporal changes in microbial signatures were associated with the development of ACR. Methods: We performed cross-sectional and longitudinal analyses (joint modeling of longitudinal and time-to-event data and trajectory comparisons) of 16S rRNA gene sequencing results derived from lung transplant recipient lower airway samples collected at multiple timepoints. Measurements and Main Results: Among 103 lung transplant recipients, 25 (24.3%) developed ACR. In comparing samples acquired one month after transplant, subjects who never developed ACR demonstrated lower airway enrichment with several oral commensals (e.g., Prevotella and Veillonella spp.) compared to those with current or future (beyond one month) ACR. However, a subgroup analysis of those who developed ACR beyond one month revealed delayed enrichment with oral commensals occurring at the time of ACR diagnosis compared to baseline, when enrichment with more traditionally pathogenic taxa was present. In longitudinal models, dynamic changes in alpha diversity (characterized by an initial decrease and a subsequent increase) and in the taxonomic trajectories of numerous oral commensals were more commonly observed in subjects with ACR. Conclusion: Dynamic changes in the lower airway microbiota are associated with the development of ACR, supporting its potential role as a useful biomarker or in ACR pathogenesis.

Prolonged Ischemia Increases Complications Among High- and Low-Volume Centers in Lung Transplantation.

BACKGROUND: The effect of prolonged allograft ischemic time on lung transplant outcomes remains controversial, with most studies associating it with increased mortality, but this effect is partly mitigated by center volume. This study sought to evaluate the mechanism of these findings and clarify the impact of ischemic time on short-term outcomes in a national sample. METHODS: Data on lung transplants (January 2010-Janary 2017) were extracted from the Scientific Registry of Transplant Recipients database. Ischemic time was dichotomized as prolonged ischemic time (PIT) or no PIT (N-PIT) at 6 hours. High-volume centers were defined as the top quintile. The primary outcome was 30-day, 1-year, and 3-year mortality; secondary outcomes included in-hospital complications and 72-hour oxygenation. RESULTS: Among 11,809 records, there were significant differences between PIT and N-PIT recipients by demographics, lung allocation score, and donor organ metrics. In a 1:1 propensity score-matched cohort (n = 6422), PIT recipients had reduced survival compared with N-PIT at 3 years (66.5% vs 68.8%, P = .031). On multivariable analysis, this effect persisted among low-volume but not high-volume centers. PIT recipients were more likely to require reintubation, prolonged (>5 days) mechanical ventilation, hemodialysis, longer stay, and acute rejection (all P < .01). Except for reintubation, these disparities were present at both high- and low-volume centers independently. Ischemic time had no effect on 72-hour oxygenation. CONCLUSIONS: PIT remains associated with higher rates of postoperative complications and reduced short-term survival. While center volume ameliorated the survival impact, this was not achieved by reducing postoperative complications. Further research is warranted before broadening ischemic time thresholds among low-volume centers.

Future of Lung Transplantation: Xenotransplantation and Bioengineering Lungs.

Xenotransplantation promises to alleviate the issue of donor organ shortages and to decrease waiting times for transplantation. Recent advances in genetic engineering have allowed for the creation of pigs with up to 16 genetic modifications. Several combinations of genetic modifications have been associated with extended graft survival and life-supporting function in experimental heart and kidney xenotransplants. Lung xenotransplantation carries specific challenges related to the large surface area of the lung vascular bed, its innate immune system's intrinsic hyperreactivity to perceived 'danger', and its anatomic vulnerability to airway flooding after even localized loss of alveolocapillary barrier function. This article discusses the current status of lung xenotransplantation, and challenges related to immunology, physiology, anatomy, and infection. Tissue engineering as a feasible alternative to develop a viable lung replacement solution is discussed.

Organ Donation, the Non-Perfect Lung Donor, and Variability in Conversion to Transplant.

Rates of lung donation have increased over the past several years. This has been accomplished through the utilization of donors with extended criteria, the creation of donor hospitals or centers, and the optimization of lungs through the implementation of donor management protocols. These measures have resulted in augmenting the pool of available donors thereby decreasing the wait time for lung transplantation candidates. Although transplant programs vary significantly in their acceptance rates of these organs, studies have not shown any difference in the incidence of primary graft dysfunction or overall mortality for the recipient when higher match-run sequence organs are accepted. Yet, the level of comfort in accepting these donors varies among transplant programs. This deviation in practice results in these organs going to lower-priority candidates thereby increasing the waitlist time of other recipients and ultimately has a deleterious effect on an institution's waitlist mortality.

One-year immunologic outcomes of lung transplantation utilizing hepatitis C-viremic donors.

Little is known about the effects of hepatitis C viremia on immunologic outcomes in the era of direct-acting antivirals. We conducted a prospective, single-arm trial of lung transplantation from hepatitis C-infected donors into hepatitis C-naïve recipients (n = 21). Recipients were initiated on glecaprevir-pibrentasvir immediately post-transplant and were continued on therapy for a total of 8 weeks. A control group of recipients of hepatitis C-negative lungs were matched 1:1 on baseline variables (n = 21). The primary outcome was the frequency of acute cellular rejection over 1-year post-transplant. Treatment with glecaprevir-pibrentasvir was well tolerated and resulted in viremia clearance after a median of 16 days of therapy (IQR 10-24 days). At one year, there was no difference in incidence of acute cellular rejection (71.4% vs. 85.7%, P = .17) or rejection requiring treatment (33.3% vs. 57.1%, P = .12). Mean cumulative acute rejection scores were similar between groups (.46 [SD ± .53] vs. .52 [SD ± .37], P = .67). Receipt of HCV+ organs was not associated with acute rejection on unadjusted Cox regression analysis (HR .55, 95% CI .28-1.11, P = .09), or when adjusted for risk factors known to be associated with acute rejection (HR .57, 95% CI .27-1.21, P = .14). Utilization of hepatitis C infected lungs with immediate treatment leads to equivalent immunologic outcomes at 1 year.

Multimodal opioid-sparing pain management after lung transplantation and the impact of liposomal bupivacaine intercostal nerve block.

Opioid analgesics are commonly used post-lung transplant, but have many side effects and are associated with worse outcomes. We conducted a retrospective review of all lung transplant recipients who were treated with a multimodal opioid-sparing pain protocol. The use of liposomal bupivacaine intercostal nerve block was variable due to hospital restrictions. The primary objective was to describe opioid requirements and patient-reported pain scores early post-lung transplant and to assess the impact of intraoperative liposomal bupivacaine intercostal nerve block. We treated 64 lung transplant recipients with our protocol. Opioid utilization decreased to a mean of 43 milligram oral morphine equivalents by postoperative day 4. Median pain scores peaked at 4 on postoperative day 1 and decreased thereafter. Only three patients were discharged home with opioids, all of whom were taking opioid agonist therapy pre-transplant for opioid use disorder. Patients who received liposomal bupivacaine intercostal nerve block in the operating room had a significant reduction in opioid consumption over postoperative day 1 through 4 (228 mg vs. 517 mg, P= .032). A multimodal opioid-sparing pain management protocol is feasible and resulted in weaning of opioids prior to hospital discharge.

Clinical and Financial Implications of 2 Treatment Strategies for Donor-derived Hepatitis C Infections.

Transplanting hepatitis C viremic donor organs into hepatitis C virus (HCV)-negative recipients is becoming increasingly common; however, practices for posttransplant direct-acting antiviral (DAA) treatment vary widely. Protracted insurance authorization processes for DAA therapy often lead to treatment delays. METHODS: At our institution, 2 strategies for providing DAA therapy to HCV- recipients of HCV+ transplants have been used. For thoracic organ recipients, an institution-subsidized course of initial therapy was provided to ensure an early treatment initiation date. For abdominal organ recipients, insurance approval for DAA coverage was sought once viremia developed, and treatment was initiated only once the insurance-authorized supply of drug was received. To evaluate the clinical impact of these 2 strategies, we retrospectively collected data pertaining to the timing of DAA initiation, duration of recipient viremia, and monetary costs incurred by patients and the institution for patients managed under these 2 DAA coverage strategies. RESULTS: One hundred fifty-two transplants were performed using HCV viremic donor organs. Eighty-nine patients received DAA treatment without subsidy, and 62 received DAA treatment with subsidy. One patient who never developed viremia posttransplant received no treatment. Subsidizing the initial course enabled earlier treatment initiation (median, 4 d [interquartile range (IQR), 2-7] vs 10 [IQR, 8-13]; P < 0.001) and shorter duration of viremia (median, 16 d [IQR, 12-29] vs 36 [IQR, 30-47]; P < 0.001). Institutional costs averaged $9173 per subsidized patient and $168 per nonsubsidized patient. Three needlestick exposures occurred in caregivers of viremic patients. CONCLUSIONS: Recipients and their caregivers stand to benefit from earlier DAA treatment initiation; however, institutional costs to subsidize DAA therapy before insurance authorization are substantial. Insurance authorization processes for DAAs should be revised to accommodate this unique patient group.

Percutaneous Dilational Tracheostomy for Coronavirus Disease 2019 Patients Requiring Mechanical Ventilation.

OBJECTIVES: To assess the impact of percutaneous dilational tracheostomy in coronavirus disease 2019 patients requiring mechanical ventilation and the risk for healthcare providers. DESIGN: Prospective cohort study; patients were enrolled between March 11, and April 29, 2020. The date of final follow-up was July 30, 2020. We used a propensity score matching approach to compare outcomes. Study outcomes were formulated before data collection and analysis. SETTING: Critical care units at two large metropolitan hospitals in New York City. PATIENTS: Five-hundred forty-one patients with confirmed severe coronavirus disease 2019 respiratory failure requiring mechanical ventilation. INTERVENTIONS: Bedside percutaneous dilational tracheostomy with modified visualization and ventilation. MEASUREMENTS AND MAIN RESULTS: Required time for discontinuation off mechanical ventilation, total length of hospitalization, and overall patient survival. Of the 541 patients, 394 patients were eligible for a tracheostomy. One-hundred sixteen were early percutaneous dilational tracheostomies with median time of 9 days after initiation of mechanical ventilation (interquartile range, 7-12 d), whereas 89 were late percutaneous dilational tracheostomies with a median time of 19 days after initiation of mechanical ventilation (interquartile range, 16-24 d). Compared with patients with no tracheostomy, patients with an early percutaneous dilational tracheostomy had a higher probability of discontinuation from mechanical ventilation (absolute difference, 30%; p < 0.001; hazard ratio for successful discontinuation, 2.8; 95% CI, 1.34-5.84; p = 0.006) and a lower mortality (absolute difference, 34%, p < 0.001; hazard ratio for death, 0.11; 95% CI, 0.06-0.22; p < 0.001). Compared with patients with late percutaneous dilational tracheostomy, patients with early percutaneous dilational tracheostomy had higher discontinuation rates from mechanical ventilation (absolute difference 7%; p < 0.35; hazard ratio for successful discontinuation, 1.53; 95% CI, 1.01-2.3; p = 0.04) and had a shorter median duration of mechanical ventilation in survivors (absolute difference, -15 d; p < 0.001). None of the healthcare providers who performed all the percutaneous dilational tracheostomies procedures had clinical symptoms or any positive laboratory test for severe acute respiratory syndrome coronavirus 2 infection. CONCLUSIONS: In coronavirus disease 2019 patients on mechanical ventilation, an early modified percutaneous dilational tracheostomy was safe for patients and healthcare providers and associated with improved clinical outcomes.

High Lung Transplant Center Volume Is Associated With Increased Survival in Hospitalized Patients.

BACKGROUND: The lung allocation score (LAS) was designed to optimize the use of pulmonary allografts based on anticipated pretransplant survival and posttransplant outcome. Hospital admission status, not included in the LAS, has not been comprehensively investigated with regard to organ allocation. The objective of this study was to determine whether pretransplant hospital admission status was independently associated with posttransplant mortality and whether high center volume was associated with improved survival in that cohort. METHODS: All consecutive adult lung transplants provided by the Scientific Registry of Transplant Recipients were retrospectively reviewed (from 2007 to 2017). Group stratification was performed based on admission status at the time of transplantation. A Cox proportional hazard regression was used to determine independent associations with posttransplant mortality. RESULTS: During the study period, 3747 of 18,416 recipients (20%) were admitted to the hospital at the time of transplantation. Compared with nonadmitted recipients, LAS were significantly higher and waitlist times significantly shorter. Admitted recipients had higher rates of prolonged mechanical ventilation, higher rates of posttransplant dialysis, and longer posttransplant lengths of stay. Pretransplant admission to a low-volume center conferred significantly worse survival compared with nonadmitted patients, and high-volume centers were independently associated with improved survival compared with low-volume centers. CONCLUSIONS: Hospital admission status is associated with increased posttransplant mortality independent of the LAS and the factors from which it is calculated. However, adjusted survival analysis demonstrates that admission to a high-volume center appears to be independently associated with improved survival compared with low-volume centers.

Extracorporeal Membrane Oxygenation Support in Severe COVID-19.

BACKGROUND: Coronavirus disease 2019 (COVID-19) remains a worldwide pandemic with a high mortality rate among patients requiring mechanical ventilation. The limited data that exist regarding the utility of extracorporeal membrane oxygenation (ECMO) in these critically ill patients show poor overall outcomes. This report describes our institutional practice regarding the application and management of ECMO support for patients with COVID-19 and reports promising early outcomes. METHODS: All critically ill patients with confirmed COVID-19 evaluated for ECMO support from March 10, 2020, to April 24, 2020, were retrospectively reviewed. Patients were evaluated for ECMO support based on a partial pressure of arterial oxygen/fraction of inspired oxygen ratio of less than 150 mm Hg or pH of less than 7.25 with a partial pressure of arterial carbon dioxide exceeding 60 mm Hg with no life-limiting comorbidities. Patients were cannulated at bedside and were managed with protective lung ventilation, early tracheostomy, bronchoscopies, and proning, as clinically indicated. RESULTS: Among 321 patients intubated for COVID-19, 77 patients (24%) were evaluated for ECMO support, and 27 patients (8.4%) were placed on ECMO. All patients were supported with venovenous ECMO. Current survival is 96.3%, with only 1 death to date in more than 350 days of total ECMO support. Thirteen patients (48.1%) remain on ECMO support, and 13 patients (48.1%) have been successfully decannulated. Seven patients (25.9%) have been discharged from the hospital. Six patients (22.2%) remain in the hospital, of which 4 are on room air. No health care workers who participated in ECMO cannulation developed symptoms of or tested positive for COVID-19. CONCLUSIONS: The early outcomes presented here suggest that the judicious use of ECMO support in severe COVID-19 may be clinically beneficial.

Single and Double Lung Transplantation Have Equivalent Survival for Idiopathic Pulmonary Fibrosis.

BACKGROUND: Several studies have described improved survival with double lung transplant (DLT) compared with single lung transplant (SLT) in pulmonary fibrosis. To avoid the innate selection bias of including patients exclusively listed for SLT or DLT, this study analyzed those deemed appropriate for either procedure at time of listing. METHODS: All consecutive adult lung transplants for idiopathic pulmonary fibrosis provided by the Scientific Registry of Transplant Recipients were retrospectively reviewed (2007-2017). Isolated lobar transplants (n = 11) or patients listed only for SLT (n = 1834) or DLT (n = 2372) were excluded. Group stratification was based on the ultimate procedure (SLT vs DLT). Group propensity matching was performed based on 24 recipient and donor characteristics. Recipient demographics, donor demographics, and outcomes were compared between groups. RESULTS: During the study period 45% (974/2179) and 55% (1205/2179) of patients ultimately received SLT and DLT, respectively. After propensity matching 466 matched patients remained in each group. SLT patients were less likely to require prolonged (>48 hours) ventilator support than DLT patients. There was also a trend toward reduced rates of posttransplant renal failure and hospital length of stay in SLT recipients. Whether analyzed by time of listing or time of transplant, survival was similar between groups. CONCLUSIONS: In recipients concurrently listed for SLT and DLT overall survival was similar regardless of the eventual procedure. These data suggest that the previously purported survival advantage for DLT may purely represent selection bias and should not preclude the use of SLT in appropriately selected idiopathic pulmonary fibrosis patients.

Impact of the Opioid Epidemic on Lung Transplantation: Donor, Recipient, and Discard Characteristics.

BACKGROUND: The national opioid epidemic may have expanded the donor pool for lung transplant, but concerns remain regarding infectious risks and allograft function. This study compared donor and recipient characteristics, outcomes, and reasons for organ discard between overdose death donors (ODDs) and all other mechanism-of-death donors. METHODS: Data on adult lung transplants from 2000 to 2017 were provided by the Scientific Registry of Transplant Recipients. Pulmonary allografts used in multiple organ transplants were excluded. Donor and recipient demographics, outcomes, and organ discard were analyzed with regards to ODDs since 2010. Discard analysis was limited to donors who had at least 1 organ transplanted but their pulmonary allografts discarded. RESULTS: From 2010 to 2017, 7.3% of lung transplants (962/13,196) were from ODDs, over a 3-fold increase from the 2.1% (164/7969) in 2000 to 2007. ODDs were younger but more likely to have a history of smoking and hepatitis C or an abnormal bronchoscopy finding. Overall survival was similar between ODD and non-ODD groups. ODDs of discarded pulmonary allografts were younger and more likely to be hepatitis C positive but were less likely to have a history of smoking than their non-ODD counterparts. CONCLUSIONS: Rates of ODD use in lung transplant have increased in accordance with the opioid epidemic, but there remains a significant pool of ODD pulmonary allografts with favorable characteristics that are discarded. With no significant difference in survival between ODD and non-ODD recipients, further expansion of this donor pool may be appropriate, and pulmonary allografts should not be discarded based solely on ODD status.

Early airway dehiscence: Risk factors and outcomes with the rising incidence of extracorporeal membrane oxygenation as a bridge to lung transplantation.

BACKGROUND: Anastomotic complications occur in 7% to 18% of lung transplant recipients, among which airway dehiscence (AD) is particularly catastrophic. Using multi-institutional registry data, this study compared preoperative recipient/donor risk factors and outcomes in patients with and without AD and analyzed the effect of extracorporeal membrane oxygenation (ECMO) on the incidence of AD. METHODS: Data on adult lung transplants from 2007 to 2017 were provided by the Scientific Registry of Transplant Recipients. Patients receiving isolated lobar transplantation and patients with unknown AD status were excluded. Multivariable logistic regression identified independent risk factors for AD. Kaplan-Meier curves and log-rank tests describe mortality and graft survival. RESULTS: Of 18 122 lung transplants, 275 (1.5%) experienced AD. While the incidence of ECMO steadily increased from 0.7% to 5.9% over the study period, the incidence of AD remained relatively constant. Multivariable analysis revealed recipient male gender and prolonged ( > 48 hours) posttransplant mechanical ventilation as independent predictive factors for AD, while advanced donor age and single left lung transplant were protective factors. Recipient chronic steroid use, recipient diabetes, donor diabetes, and donor smoking history were not predictive of AD. Mortality and graft failure were significantly worse in the AD group. CONCLUSIONS: Despite increased ECMO utilization, the incidence of AD has remained stable. Multiple independent risk factors for AD were identified and poor postoperative outcomes confirmed. However, many known impediments to wound healing such as recipient chronic steroid use, recipient and donor diabetes, and donor smoking were not identified as risk factors for AD, reinforcing the critical role of technical performance.

Immune Checkpoint Ligand PD-L1 Is Upregulated in Pulmonary Lymphangioleiomyomatosis.

Pulmonary lymphangioleiomyomatosis (LAM) is a slow-progressing metastatic disease that is driven by mutations in the tumor suppressor tuberous sclerosis complex 1/2 (TSC1/2). Rapamycin inhibits LAM cell proliferation and is the only approved treatment, but it cannot cause the regression of existing lesions and can only stabilize the disease. However, in other cancers, immunotherapies such as checkpoint blockade against PD-1 and its ligand PD-L1 have shown promise in causing tumor regression and even curing some patients. Thus, we asked whether PD-L1 has a role in LAM progression. In vitro, PD-L1 expression in murine Tsc2-null cells is unaffected by mTOR inhibition with torin but can be upregulated by IFN-γ. Using immunohistochemistry and single-cell flow cytometry, we found increased PD-L1 expression both in human lung tissue from patients with LAM and in Tsc2-null lesions in a murine model of LAM. In this model, PD-L1 is highly expressed in the lung by antigen-presenting and stromal cells, and activated T cells expressing PD-1 infiltrate the affected lung. In vivo treatment with anti-PD-1 antibody significantly prolongs mouse survival in the model of LAM. Together, these data demonstrate that PD-1/PD-L1-mediated immunosuppression may occur in LAM, and suggest new opportunities for therapeutic targeting that may provide benefits beyond those of rapamycin.

Benign pneumatosis intestinalis after bilateral lung transplantation.

This series details two cases of benign pneumatosis intestinalis (PI) in patients post-lung transplant, which were discovered incidentally on routine surveillance chest radiographs during ambulatory clinic visits. Both patients had uneventful post-transplant recovery and were asymptomatic at presentation. The patients were admitted for observation. Contrast-enhanced abdominal CT scans confirmed the plain film findings. Both cases were managed conservatively with bowel rest, intravenous hydration and serial abdominal examinations. The patients had unremarkable hospital courses and were both discharged in good condition. Our current understanding of benign PI in patients post-transplant is limited to a few case series and case reports. Greater awareness of this entity may decrease unnecessary invasive procedures and improve management of these patients.

Understanding the Concept of Health Care-Associated Pneumonia in Lung Transplant Recipients.

BACKGROUND: Limited data are available regarding the etiologic impact of health care-associated pneumonia (HCAP) in lung transplant recipients. Therefore, our aim was to evaluate the microbiologic differences between HCAP and hospital-acquired pneumonia (HAP)/ventilator-associated pneumonia (VAP) in lung transplant recipients with a radiographically confirmed diagnosis of pneumonia. METHODS: We performed a retrospective cohort study of lung transplant recipients with pneumonia at one transplant center over a 7-year period. Eligible patients included lung transplant recipients who developed a first episode of radiographically confirmed pneumonia ≥ 48 h following transplantation. HCAP, HAP, and VAP were classified according to the American Thoracic Society/Infectious Diseases Society of America 2005 guidelines. χ² and Student t tests were used to compare categorical and continuous variables, respectively. RESULTS: Sixty-eight lung transplant recipients developed at least one episode of pneumonia. HCAP (n = 42; 62%) was most common, followed by HAP/VAP (n = 26; 38%) stratified in HAP (n = 20; 77%) and VAP (n = 6; 23%). Pseudomonas aeruginosa was the predominantly isolated organism (n = 22; 32%), whereas invasive aspergillosis was uncommon (< 10%). Multiple-drug resistant (MDR) pathogens were less frequently isolated in patients with HCAP compared with HAP/VAP (5% vs 27%; P = .009). Opportunistic pathogens were less frequently identified in lung transplant recipients with HCAP than in those with HAP/VAP (7% vs 27%; P = .02). Lung transplant recipients with HCAP had a similar mortality at 90 days (n = 9 [21%] vs n = 4 [15%]; P = .3) compared with patients with HAP/VAP. CONCLUSIONS: HCAP was the most frequent infection in lung transplant recipients. MDR pathogens and opportunistic pathogens were more frequently isolated in HAP/VAP. There were no differences in 30- and 90-day mortality between lung transplant recipients with HCAP and those with HAP/VAP.