Extended donor criteria in lung transplantation: Impact on organ allocation

Maximizing organs for donation: the potential for ex situ normothermic machine perfusion

Currently, there is a shortfall in the number of suitable organs available for transplant resulting in a high number of patients on the active transplant waiting lists worldwide. To address this shortfall and increase the utilization of donor organs, the acceptance criteria for donor organs is gradually expanding including increased use of organs from donation after circulatory death. Use of such extended criteria donors and exposure of organs to more prolonged periods of warm or cold ischaemia also increases the risk of primary graft dysfunction occurring. Normothermic machine perfusion (NMP) offers a unique opportunity to objectively assess donor organ function outside the donor body and potentially recondition those deemed unsuitable on initial evaluation prior to implantation in the recipient. Furthermore, NMP provides a platform to support the use of established and novel therapeutics delivered directly to the organ, without the need to worry about potential deleterious 'off-target' side effects typically considered when treating the whole patient. This review will explore some of the novel therapeutics currently being added to perfusion platforms during NMP experimentally in an attempt to improve organ function and post-transplant outcomes.

Evaluation of Donor Lungs for Transplantation: The Efficacy of Screening Bronchoscopy for Detecting Donor Aspiration and Its Relationship to the Resulting Allograft Function in Corresponding Recipients

BACKGROUND

Potential organ donors often have suffered anoxic and/or traumatic brain injury during which they may have experienced aspiration of gastric material (AGM). Evaluation of such donors typically includes a screening bronchoscopic examination during which determinations of aspiration are made. The efficacy of this visual screening and its relationship to post-transplant allograft function are unknown.

METHODS

Before procurement, bronchoscopy was performed on donors in which both bronchoalveolar lavage fluid (BALF) was collected and a visual inspection made. As a marker of AGM, BALF specimens were analyzed for the presence of bile salts. Data collected on the corresponding recipients included primary graft dysfunction (PGD) score, post-transplant spirometry, acute rejection scores (ARS), and overall survival.

RESULTS

Of 31 donors evaluated, bronchoscopies revealed only 2 with visual evidence of AGM, whereas BALF analysis for bile salts indicated AGM in 14. As such, screening bronchoscopy had a sensitivity of only 7.1%. Visual detection of AGM via bronchoscopy was not associated with any resulting grade of PGD (χ2 = 2.96, P = .23); however, AGM defined by detection of bile salts was associated (χ2 = 7.56, P = .02). Over the first post-transplant year, the corresponding recipients experienced a similar improvement in allograft function (χ2 = 1.63, P = .69), ARS (P = .69), and survival (P = .24).

CONCLUSION

Visual inspection during a single bronchoscopic examination of lung donors underestimates the prevalence of AGM. The detection of bile salts in donor BALF is associated with early allograft dysfunction in the corresponding recipients but not with later allograft proficiency, acute rejection responses, or 1-year post-transplant survival.

Application of Mesenchymal Stem Cells During Machine Perfusion: An Emerging Novel Strategy for Organ Preservation

Although solid organ transplantation remains the definitive management for patients with end-stage organ failure, this ultimate treatment has been limited by the number of acceptable donor organs. Therefore, efforts have been made to expand the donor pool by utilizing marginal organs from donation after circulatory death or extended criteria donors. However, marginal organs are susceptible to ischemia-reperfusion injury (IRI) and entail higher requirements for organ preservation. Recently, machine perfusion has emerged as a novel preservation strategy for marginal grafts. This technique continually perfuses the organs to mimic the physiologic condition, allows the evaluation of pretransplant graft function, and more excitingly facilitates organ reconditioning during perfusion with pharmacological, gene, and stem cell therapy. As mesenchymal stem cells (MSCs) have anti-oxidative, immunomodulatory, and regenerative properties, mounting studies have demonstrated the therapeutic effects of MSCs on organ IRI and solid organ transplantation. Therefore, MSCs are promising candidates for organ reconditioning during machine perfusion. This review provides an overview of the application of MSCs combined with machine perfusion for lung, kidney, liver, and heart preservation and reconditioning. Promising preclinical results highlight the potential clinical translation of this innovative strategy to improve the quality of marginal grafts.

Transcriptional analysis identifies potential novel biomarkers associated with successful ex-vivo perfusion of human donor lungs

Background

Transplantation is an effective treatment for end‐stage lung disease, but the donor organ shortage is a major problem. Ex‐vivo lung perfusion (EVLP) of extended criteria organs enables functional assessment to facilitate clinical decision‐making around utilization, but the molecular processes occurring during EVLP, and how they differ between more or less viable lungs, remain to be determined.

Methods

We used RNA sequencing of lung tissue to delineate changes in gene expression occurring in 10 donor lungs undergoing EVLP and compare lungs that were deemed non‐transplantable (n = 4) to those deemed transplantable (n = 6) following perfusion.

Results

We found that lungs deemed unsuitable for transplantation had increased induction of innate immune pathways and lower expression of oxidative phosphorylation related genes. Furthermore, the expression of SCGB1A1, a gene encoding an anti‐inflammatory secretoglobin CC10, and other club cell genes was significantly decreased in non‐transplantable lungs, while CHIT‐1 was increased. Using a larger validation cohort (n = 17), we confirmed that the ratio of CHIT1 and SCGB1A1 protein levels in lung perfusate have potential utility to distinguish transplantable from non‐transplantable lungs (AUC .81).

Conclusions

Together, our data identify novel biomarkers that may assist with pre‐transplant lung assessment, as well as pathways that may be amenable to therapeutic intervention during EVLPAQ6.

Donor Aorta as Conduit for Ex Vivo Lung Perfusion

For ex vivo lung perfusion (EVLP), there is often inadequate pulmonary artery for effective EVLP. Creation of a neopulmonary artery conduit with donor aorta alleviates this shortcoming. This technique will become of more importance and need as there are more donation after circulatory death donor (DCD) heart procurements as this is a common source of EVLP. With the time constraints associated with the DCD recovery approach, there is a high likelihood of having a short native pulmonary artery with the lung block necessitating this approach.

Donor selection for lung transplant in Turkey: Is it necessary to wait for an ideal donor?

Background

The aim of this study was to evaluate the donor criteria used in lung transplantation in our clinic.

Methods

A total of 55 cadaveric donors who were accepted for lung transplantation in our clinic between December 2016 and January 2019 were retrospectively analyzed according to ideal donor criteria. The donors were divided into two groups as ideal and non-ideal ones according to their age, partial pressure of oxygen in arterial blood, history of smoking, and ventilation day. Donor data, recipient characteristics and survival outcomes were evaluated.

Results

Of 55 donors accepted for lung transplantation, 24 (43.7%) were ideal and 31 (56.3%) were non-ideal donors. The 90-day mortality and one-year survival rates were not significantly different between the two groups. The 90-day mortality was 25% in the ideal group and 22.6% in the non-ideal group (p=0.834). The one-year survival rates after lung transplantation were 64.5% versus 70.6% in the ideal and non-ideal groups, respectively (p=0.444).

Conclusion

The whole clinical picture should be evaluated before accepting or rejecting donors for lung transplantation. The use of lung donors that do not meet the ideal criteria does not impair short- and mid-term results, compared to ideal lung donors. Strict implementation of donor criteria may prevent using suitable donors for lung transplantation. Use of non-ideal donors can reduce waiting list mortality.

Ex Vivo Lung Perfusion: A Platform for Donor Lung Assessment, Treatment and Recovery

Lung transplantation offers a lifesaving therapy for patients with end-stage lung disease but its availability is presently limited by low organ utilization rates with donor lungs frequently excluded due to unsuitability at assessment. When transplantation does occur, recipients are then vulnerable to primary graft dysfunction (PGD), multitudinous short-term complications, and chronic lung allograft dysfunction. The decision whether to use donor lungs is made rapidly and subjectively with limited information and means many lungs that might have been suitable are lost to the transplant pathway. Compared to static cold storage (SCS), ex vivo lung perfusion (EVLP) offers clinicians unrivalled opportunity for rigorous objective assessment of donor lungs in conditions replicating normal physiology, thus allowing for better informed decision-making in suitability assessments. EVLP additionally offers a platform for the delivery of intravascular or intrabronchial therapies to metabolically active tissue aiming to treat existing lung injuries. In the future, EVLP may be employed to provide a pre-transplant environment optimized to prevent negative outcomes such as primary graft dysfunction (PGD) or rejection post-transplant.

Donor factors and risk of primary graft dysfunction and mortality post lung transplantation: A proposed conceptual framework

Lung transplantation remains a therapeutic option in end-stage lung disease. However, despite advances in the field, early allograft function can be compromised by the development of primary graft dysfunction (PGD); this being the leading cause of morbidity and mortality immediately following the lung transplant procedure. Several recipient factors have been associated with increased risk of PGD, but less is known about donor factors. Aging, tobacco, and chronic alcohol use are donor factors implicated, but how these factors promote PGD remains unclear. Herein, we discuss the available clinical data that link these donor factors with outcomes after lung transplantation, and how they might render the recipient susceptible to PGD through a two-hit process.

Lung Transplantation, Pulmonary Endothelial Inflammation, and Ex-Situ Lung Perfusion: A Review

Lung transplantation (LTx) is the gold standard treatment for end-stage lung disease; however, waitlist mortality remains high due to a shortage of suitable donor lungs. Organ quality can be compromised by lung ischemic reperfusion injury (LIRI). LIRI causes pulmonary endothelial inflammation and may lead to primary graft dysfunction (PGD). PGD is a significant cause of morbidity and mortality post-LTx. Research into preservation strategies that decrease the risk of LIRI and PGD is needed, and ex-situ lung perfusion (ESLP) is the foremost technological advancement in this field. This review addresses three major topics in the field of LTx: first, we review the clinical manifestation of LIRI post-LTx; second, we discuss the pathophysiology of LIRI that leads to pulmonary endothelial inflammation and PGD; and third, we present the role of ESLP as a therapeutic vehicle to mitigate this physiologic insult, increase the rates of donor organ utilization, and improve patient outcomes.

Comparison of donor scores in bilateral lung transplantation-A large single-center analysis

Objectifying donor lung quality is difficult and currently there is no consensus. Several donor scoring systems have been proposed in recent years. They all lack large-scale external validation and widespread acceptance. A retrospective evaluation of 2201 donor lungs offered to the lung transplant program at the Medical University of Vienna between January 2010 and June 2018 was performed. Five different lung donor scores were calculated for each offer (Oto, ET, MALT, UMN-DLQI, and ODSS). Prediction of organ utilization, 1-year graft survival, and long-term outcome were analyzed for each score. 1049 organs were rejected at the initial offer (group I), 209 lungs declined after procurement (group II), and 841 lungs accepted and transplanted (group III). The Oto score was superior in predicting acceptance of the initial offer (AUC: 0.795; CI: 0.776-0.815) and actual donor utilization (AUC: 0.660; CI: 0.618-0.701). Prediction of 1-year graft survival was best using the MALT score, Oto score, and UMN-DLQI. Stratification of early outcome by MALT was significant for length of mechanical ventilation (LMV), PGD3 rates, ICU stay and hospital stay, and in-hospital-mortality, respectively. To the best of our knowledge, this study is the largest validation analysis comparing currently available donor scores. The Oto score was superior in predicting organ utilization, and MALT score and UMN-DLQI for predicting outcome after lung transplantation.

Short- and Long-Term Impact of Smoking Donors in Lung Transplantation: Clinical and Pathological Analysis

Background: The use of smoking donors (SD) is one strategy to increase the organ pool for lung transplantation (LT), but the benefit-to-risk ratio has not been demonstrated. This study aimed to evaluate the impact of SD history on recipient outcomes and graft alterations. Methods: LTs in 293 patients were retrospectively reviewed and divided into non-SD (n = 225, group I), SD < 20 pack-years (n = 45, group II), and SD ≥ 20 pack-years (n = 23, group III) groups. Moreover, several lung donor biopsies before implantation (equally divided between groups) were evaluated, focusing on smoking-related lesions. Correlations were analyzed between all pathological data and smoking exposure, along with other clinical parameters. Results: Among the three groups, donor and recipient characteristics were comparable, except for higher Oto scores and age in group III. Group III showed a longer intensive care unit (ICU) and hospital stay compared with the other two groups. This finding was confirmed when SD history was considered as a continuous variable. However, survival and other mid- and long-term major outcomes were not affected by smoking history. Finally, morphological lesions did not differ between the three groups. Conclusions: In our study, SDs were associated with a longer post-operative course, without affecting graft aspects or mid- and long-term outcomes. A definition of pack-years cut-off for organ refusal should be balanced with the other extended criteria donor factors.

Trauma and donation after circulatory death: a case series from a major trauma center

Even with encouraging recipient outcomes, transplantation using donation after circulatory death (DCD) is still limited. A major barrier to this type of transplantation is the consequences of warm ischemia on graft survival; however, preservation techniques may reduce the consequences of cardiac arrest and provide better organ conservation. Furthermore, DCD in trauma patients could further expand organ donation. We present five cases in which organs were retrieved and transplanted successfully using normothermic regional perfusion (NRP) in trauma patients. Prompt critical care support and surgical treatment allowed us to overcome the acute phase. Unfortunately, owing to the severity of their injuries, all of the donors died. However, the advanced and continuous organ-specific supportive treatment allowed the maintenance of general clinical stability and organ preservation. Consequently, it was possible to retrieve and transplant the donors’ organs. Death was ascertained in accordance with cardio-circulatory criteria, which was followed by NRP. We consider that DCD in trauma patients may represent an important source of organs.

Bioengineering of Pulmonary Epithelium With Preservation of the Vascular Niche

The shortage of transplantable donor organs directly affects patients with end-stage lung disease, for which transplantation remains the only definitive treatment. With the current acceptance rate of donor lungs of only 20%, rescuing even one half of the rejected donor lungs would increase the number of transplantable lungs threefold, to 60%. We review recent advances in lung bioengineering that have potential to repair the epithelial and vascular compartments of the lung. Our focus is on the long-term support and recovery of the lung ex vivo, and the replacement of defective epithelium with healthy therapeutic cells. To this end, we first review the roles of the lung epithelium and vasculature, with focus on the alveolar-capillary membrane, and then discuss the available and emerging technologies for ex vivo bioengineering of the lung by decellularization and recellularization. While there have been many meritorious advances in these technologies for recovering marginal quality lungs to the levels needed to meet the standards for transplantation – many challenges remain, motivating further studies of the extended ex vivo support and interventions in the lung. We propose that the repair of injured epithelium with preservation of quiescent vasculature will be critical for the immediate blood supply to the lung and the lung survival and function following transplantation.

Mitigation of Primary Graft Dysfunction in Lung Transplantation: Current Understanding and Hopes for the Future

Primary graft dysfunction (PGD) is a form of acute lung injury that develops within the first 72 hours after lung transplantation. The overall incidence of PGD is estimated to be around 30%, and the 30-day mortality for grade 3 PGD around 36%. PGD is also associated with the development of bronchiolitis obliterans syndrome, a specific form of chronic lung allograft dysfunction. In this article, we will discuss perioperative strategies for PGD prevention as well as possible future avenues for prevention and treatment.

A novel concept for evaluation of pulmonary function utilizing PaO2/FiO2 difference at the distinctive FiO2 in cellular ex vivo lung perfusion-an experimental study

For more accurate lung evaluation in ex vivo lung perfusion (EVLP), we have devised a new parameter, PaO₂ /FiO₂ ratio difference (PFD); PFD_1-0.4  = P/F ratio at FiO₂ 1.0 - P/F ratio at FiO₂ 0.4. The aim of this study is to compare PFD and transplant suitability, and physiological parameters utilized in cellular EVLP. Thirty-nine human donor lungs were perfused. At 2 h of EVLP, PFD_1-0.4 was compared with transplant suitability and physiological parameters. In a second study, 10 pig lungs were perfused in same fashion. PFD_1-0.4 was calculated by blood from upper and lower lobe pulmonary veins and compared with lobe wet/dry ratio and pathological findings. In human model, receiver operating characteristic curve analysis showed PFD_1-0.4 had the highest area under curve, 0.90, sensitivity, 0.96, to detect nonsuitable lungs, and significant negative correlation with lung weight ratio (R²  = 0.26, P < 0.001). In pig model, PFD_1-0.4 on lower and upper lobe pulmonary veins were significantly associated with corresponding lobe wet/dry ratios (R²  = 0.51, P = 0.019; R²  = 0.37, P = 0.060), respectively. PFD_1-0.4 in EVLP demonstrated a significant correlation with lung weight ratio and allowed more precise assessment of individual lobes in detecting lung edema. Moreover, it might support decision-making in evaluation with current EVLP criteria.

Cell replacement in human lung bioengineering

BACKGROUND

As the number of patients with end-stage lung disease continues to rise, there is a growing need to increase the limited number of lungs available for transplantation. Unfortunately, attempts at engineering functional lung de novo have been unsuccessful, and artificial mechanical devices have limited utility as a bridge to transplant. This difficulty is largely due to the size and inherent complexity of the lung; however, recent advances in cell-based therapeutics offer a unique opportunity to enhance traditional tissue-engineering approaches with targeted site- and cell-specific strategies.

METHODS

Human lungs considered unsuitable for transplantation were procured and supported using novel cannulation techniques and modified ex-vivo lung perfusion. Targeted lung regions were treated using intratracheal delivery of decellularization solution. Labeled mesenchymal stem cells or airway epithelial cells were then delivered into the lung and incubated for up to 6 hours.

RESULTS

Tissue samples were collected at regular time intervals and detailed histologic and immunohistochemical analyses were performed to evaluate the effectiveness of native cell removal and exogenous cell replacement. Regional decellularization resulted in the removal of airway epithelium with preservation of vascular endothelium and extracellular matrix proteins. After incubation, delivered cells were retained in the lung and showed homogeneous topographic distribution and flattened cellular morphology.

CONCLUSIONS

Our findings suggest that targeted cell replacement in extracorporeal organs is feasible and may ultimately lead to chimeric organs suitable for transplantation or the development of in-situ interventions to treat or reverse disease, ultimately negating the need for transplantation.

ABO-identical matching has no superiority in long-term survival in comparison to ABO-compatible matching in lung transplantation

Background

Even though identical blood group matching between recipient and donor is preferred, it is still not clear by how much this improves the outcome for patients who received a lung transplant (LTx), or whether there is any survival benefit. Earlier studies have yielded ambiguous results and few have investigated long-term survival. The aim of this study is, therefore, to explore the different outcomes of identical and compatible recipient and donor blood group matching to determine whether identical matching is superior (LTx).

Method

Between January 1990 to June 2016, 297 patients underwent primary LTx, 10 patients underwent heart and lung transplantation (HLTx), and 18 patients required re-transplantation (Re-LTx) at Skåne University Hospital in Lund. With a total of 325 transplantations at our center, 262 were ABO-identically matched while 53 were ABO-compatible. For survival analyses, the end-point used was retransplantation-free survival in addition to excluding HLTx (n = 10), assessed by Cox regression and Kaplan-Meier.

Results

ABO-compatible patients had a median of 49 days (2–641), and ABO-identical patients had a median of 89 days (1–1717) (p = 0.048) on the transplant waiting list. Patients with a limited survival up to 1-year showed significant difference in survival rate for ABO-compatible recipients compared to ABO-identical recipients (p < 0.05), however no significant difference was shown in overall survival between the two groups (p > 0.05), with the same pattern shown in patients with a limited survival rate up to ten years, emphysema-patients, when excluding single-LTx and patients transplanted before 2005 and after 2005, respectively (p > 0.05).

Conclusion

Recipients who received ABO-compatible matched grafts showed a similar survival rate to recipients who received ABO-identical matched grafts in the present study. Cytolomegalovirus and Ebstein Barr Virus mismatch were also identified as risk factors particular among emphysema patients. Since ABO-identical transplantations and ABO-compatible transplantations showed similar results, the present selection-bias of preferring ABO-identical lungs could be adjusted to increase organ allocation. It might also be possible to shorten recipient waiting list time, as an identical match showed over 80% higher time on the waiting list than a compatible, non-identical match.

National Heart, Lung, and Blood Institute and American Association for Thoracic Surgery Workshop Report: Identifying collaborative clinical research priorities in lung transplantation

This report summarizes the discussion and recommendations from the June 2017 NHLBI-AATS Workshop on Identifying Collaborative Clinical Research Priorities in Lung Transplantation.

Donor biomarkers as predictors of organ use and recipient survival after neurologically deceased donor organ transplantation

PURPOSE

We sought to build prediction models for organ transplantation and recipient survival using both biomarkers and clinical information.

MATERIALS AND METHODS

We abstracted clinical variables from a previous randomized trial (n = 556) of donor management. In a subset of donors (n = 97), we measured two candidate biomarkers in plasma at enrollment and just prior to explantation.

RESULTS

Secretory leukocyte protease inhibitor (SLPI) was significant for predicting liver transplantation (C-statistic 0.65 (0.53, 0.78)). SLPI also significantly improved the predictive performance of a clinical model for liver transplantation (integrated discrimination improvement (IDI): 0.090 (0.009, 0.210)). For other organs, clinical variables alone had strong predictive ability (C-statistic >0.80). Recipient 3-years survival was 80.0% (71.9%, 87.0%). Donor IL-6 was significantly associated with recipient 3-years survival (adjusted Hazard Ratio (95%CI): 1.26(1.08, 1.48), P = .004). Neither clinical variables nor biomarkers showed strong predictive ability for 3-year recipient survival.

CONCLUSIONS

Plasma biomarkers in neurologically deceased donors were associated with organ use. SLPI enhanced prediction within a liver transplantation model, whereas IL-6 before transplantation was significantly associated with recipient 3-year survival. Clinicaltrials.gov: NCT00987714.

Pharmacological Reconditioning of Marginal Donor Rat Lungs Using Inhibitors of Peroxynitrite and Poly (ADP-ribose) Polymerase During Ex Vivo Lung Perfusion

BACKGROUND

Donor lungs obtained after prolonged warm ischemia (WI) may be unsuitable for transplantation due to the risk of reperfusion injury, but could be reconditioned using ex-vivo lung perfusion (EVLP). Key processes of reperfusion injury include the formation of reactive oxygen species (ROS)/nitrogen species (RNS) and the activation of poly(adenosine diphosphate-ribose) polymerase (PARP). We explored whether rat lungs obtained after WI could be reconditioned during EVLP using the ROS/RNS scavenger Mn(III)-tetrakis (4-benzoic acid) porphyrin chloride (MnTBAP) or the PARP inhibitor 3-aminobenzamide (3-AB).

METHODS

Rat lungs obtained after 3 hours cold ischemia (CI group, control), or 1 hour WI plus 2 hours CI (WI group) were placed in an EVLP circuit for normothermic perfusion for 3 hours. Lungs retrieved after WI were treated or not with 3-AB (1 mg/mL) or MnTBAP (0.3 mg/mL), added to the perfusate. Measurements included physiological variables (lung compliance, vascular resistance, oxygenation capacity), lung weight gain, levels of proteins, lactate dehydrogenase, protein carbonyl (marker of ROS), 3-nitrotyrosine (marker of RNS), poly(adenosine diphosphate-ribose) (PAR, marker of PARP activation) and IL-6, in the bronchoalveolar lavage or the lung tissue, and histology.

RESULTS

In comparison to the CI group, the lungs from the WI group displayed higher protein carbonyls, 3-nitrotyrosine, PAR, lactate dehydrogenase and proteins in bronchoalveolar lavage, lung weight gain, perivascular edema, as well as reduced static compliance, but similar oxygenation. All these alterations were markedly attenuated by 3-AB and MnTBAP.

CONCLUSIONS

After EVLP, lungs obtained after WI exhibit oxidative stress, PARP activation, and tissue injury, which are suppressed by pharmacological inhibitors of ROS/RNS and PARP.

Ex-vivo recruitment and x-ray assessment of donor lungs in a challenging retrieval from a donor supported by lvad using the portable normothermic perfusion system: a case report

Background

Lung transplantation (LTx) is limited by the shortage of suitable donors. To overcome this problem, many programs have begun to use donors with extended criteria (marginal donors). However, brain-dead patients with implanted mechanical circulatory support system have rarely been considered as potential lung donors. This case demonstrates the feasibility of lung transplantations from organ donors supported by a mechanical circulatory support system despite the possible difficulties of lung retrieval.

Case presentation

Our case presents a successful procurement and bilateral lung transplantation from a donor supported by a left ventricular assist device (LVAD) who experienced an intraoperatively haemodynamic complication. The use of portable normothermic perfusion device let us to reduce ischemic injury and assess these marginal donor lungs helping us to determine the clinical suitability for transplantation. Given our extensive experience with the device instrumentation and management, the EVLP process was uneventful with excellent post-transplant course.

Conclusions

This case report demonstrates the feasibility of lung transplantations from organ donors supported by a mechanical circulatory support system using the portable normothermic perfusion platform to assess and preserve these donor lungs.

How to minimise ventilator-induced lung injury in transplanted lungs: The role of protective ventilation and other strategies

Lung transplantation is the treatment of choice for end-stage pulmonary diseases. In order to avoid or reduce pulmonary and systemic complications, mechanical ventilator settings have an important role in each stage of lung transplantation. In this respect, the use of mechanical ventilation with a tidal volume of 6 to 8 ml  kg(-1) predicted body weight, positive end-expiratory pressure of 6 to 8 cmH2O and a plateau pressure lower than 30 cmH2O has been suggested for the donor during surgery, and for the recipient both during and after surgery. For the present review, we systematically searched the PubMed database for articles published from 2000 to 2014 using the following keywords: lung transplantation, protective mechanical ventilation, lung donor, extracorporeal membrane oxygenation, recruitment manoeuvres, extracorporeal CO2 removal and noninvasive ventilation.

Donor lung assessment using selective pulmonary vein gases

OBJECTIVES

Standard donor lung assessment relies on imaging, challenge gases and subjective interpretation of bronchoscopic findings, palpation and visual assessment. Central gases may not accurately represent true quality of the lungs. We report our experience using selective pulmonary vein gases to corroborate the subjective judgement.

METHODS

Starting, January 2012, donor lungs have been assessed by intraoperative bronchoscopy, palpation and visual judgement of lung collapse upon temporary disconnection from ventilator, central gases from the aorta and selective pulmonary vein gases. Partial pressure of oxygen (pO₂) <300 mmHg on FiO₂ of 1.0 was considered low. The results of the chest X-ray and last pO₂ in the intensive care unit were also collected. Post-transplant primary graft dysfunction and survival were monitored.

RESULTS

To date, 259 consecutive brain-dead donors have been assessed and 157 transplants performed. Last pO₂ in the intensive care unit was poorly correlated with intraoperative central pO₂ (Spearman's rank correlation r_s = 0.29). Right inferior pulmonary vein pO₂ was associated (Mann-Whitney, P < 0.001) with findings at bronchoscopy [clean: median pO₂ 443 mmHg (25th-75th percentile range 349-512) and purulent: 264 mmHg (178-408)]; palpation [good: 463 mmHg (401-517) and poor: 264 mmHg (158-434)] and visual assessment of lung collapse [good lung collapse: 429 mmHg (320-501) and poor lung collapse: 205 mmHg (118-348)]. Left inferior pulmonary pO₂ was associated (P < 0.001) with findings at bronchoscopy [clean: 419 mmHg (371-504) and purulent: 254 mmHg (206-367)]; palpation [good: 444 mmHg (400-517) and poor 282 mmHg (211-419)] and visual assessment of lung collapse [good: 420 mmHg (349-496) and poor: 246 mmHg (129-330)]. At 72 h, pulmonary graft dysfunction 2 was in 21/157 (13%) and pulmonary graft dysfunction 3 in 17/157 (11%). Ninety-day and 1-year mortalities were 6/157 (4%) and 13/157 (8%), respectively.

CONCLUSIONS

Selective pulmonary vein gases provide corroborative objective support to the findings at bronchoscopy, palpation and visual assessment. Central gases do not always reflect true function of the lungs, having high false-positive rate towards the individual lower lobe gas exchange. Objective measures of donor lung function may optimize donor surgeon assessment, allowing for low pulmonary graft dysfunction rates and low 90-day and 1-year mortality.

Lung transplantation: overall approach regarding its major aspects

Lung transplantation is a well-established treatment for patients with advanced lung disease. The evaluation of a candidate for transplantation is a complex task and involves a multidisciplinary team that follows the patient beyond the postoperative period. Currently, the mean time on the waiting list for lung transplantation in the state of São Paulo, Brazil, is approximately 18 months. For Brazil as a whole, data from the Brazilian Organ Transplant Association show that, in 2014, there were 67 lung transplants and 204 patients on the waiting list for lung transplantation. Lung transplantation is most often indicated in cases of COPD, cystic fibrosis, interstitial lung disease, non-cystic fibrosis bronchiectasis, and pulmonary hypertension. This comprehensive review aimed to address the major aspects of lung transplantation: indications, contraindications, evaluation of transplant candidates, evaluation of donor candidates, management of transplant recipients, and major complications. To that end, we based our research on the International Society for Heart and Lung Transplantation guidelines and on the protocols used by our Lung Transplant Group in the city of São Paulo, Brazil.

Comparison of open gastrostomy tube to percutaneous endoscopic gastrostomy tube in lung transplant patients

Introduction

Lung transplant patients require a high degree of immunosuppression, which can impair wound healing when surgical procedures are required. We hypothesized that because of impaired healing, lung transplant patients requiring gastrostomy tubes would have better outcomes with open gastrostomy tube (OGT) as compared to percutaneous endoscopic gastrostomy tube (PEG).

Methods

The National Inpatient Sample (NIS) Database (2005–2010) was queried for all lung transplant recipients requiring OGT or PEG.

Results

There were 215 patients requiring gastrostomy tube, with 44 OGT and 171 PEG. The two groups were not different with respect to age (52.0 vs. 56.9 years, p = 0.40) and Charlson Comorbidity Index (3.3 vs. 3.5, p = 0.75). Incidence of acute renal failure was higher in the PEG group (35.2 vs. 11.8%, p = 0.003). Post-operative pneumonia, myocardial infarction, surgical site infection, DVT/PE, and urinary tract infection were not different. Post-operative mortality was higher in the PEG group (11.2 vs. 0.0%, p = 0.02). Using multiple variable analysis, PEG tube was independently associated with mortality (HR: 1.94, 95%C.I: 1.45–2.58). Variables associated with survival included age, female gender, white race, and larger hospital bed capacity.

Discussion

OGT may be the preferred method of gastric access for lung transplant recipients.

Conclusions

In lung transplant recipients, OGT results in decreased morbidity and mortality when compared to PEG.

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In lung transplant patients, open gastrostomy tube may result in less mortality than a percutaneous gastrostomy tube.

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In-hospital complications are less when lung transplant recipients receive open gastrostomy as compared to PEG.

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PEG in lung transplant recipients does not result in decreased length of stay when compared to open gastrostomy.

Ex vivo lung perfusion with adenosine A2A receptor agonist allows prolonged cold preservation of lungs donated after cardiac death

OBJECTIVE

Ex vivo lung perfusion has been successful in the assessment of marginal donor lungs, including donation after cardiac death (DCD) donor lungs. Ex vivo lung perfusion also represents a unique platform for targeted drug delivery. We sought to determine whether ischemia-reperfusion injury would be decreased after transplantation of DCD donor lungs subjected to prolonged cold preservation and treated with an adenosine A2A receptor agonist during ex vivo lung perfusion.

METHODS

Porcine DCD donor lungs were preserved at 4°C for 12 hours and underwent ex vivo lung perfusion for 4 hours. Left lungs were then transplanted and reperfused for 4 hours. Three groups (n = 4/group) were randomized according to treatment with the adenosine A2A receptor agonist ATL-1223 or the dimethyl sulfoxide vehicle: Infusion of dimethyl sulfoxide during ex vivo lung perfusion and reperfusion (DMSO), infusion of ATL-1223 during ex vivo lung perfusion and dimethyl sulfoxide during reperfusion (ATL-E), and infusion of ATL-1223 during ex vivo lung perfusion and reperfusion (ATL-E/R). Final Pao2/Fio2 ratios (arterial oxygen partial pressure/fraction of inspired oxygen) were determined from samples obtained from the left superior and inferior pulmonary veins.

RESULTS

Final Pao2/Fio2 ratios in the ATL-E/R group (430.1 ± 26.4 mm Hg) were similar to final Pao2/Fio2 ratios in the ATL-E group (413.6 ± 18.8 mm Hg), but both treated groups had significantly higher final Pao2/Fio2 ratios compared with the dimethyl sulfoxide group (84.8 ± 17.7 mm Hg). Low oxygenation gradients during ex vivo lung perfusion did not preclude superior oxygenation capacity during reperfusion.

CONCLUSIONS

After prolonged cold preservation, treatment of DCD donor lungs with an adenosine A2A receptor agonist during ex vivo lung perfusion enabled Pao2/Fio2 ratios greater than 400 mm Hg after transplantation in a preclinical porcine model. Pulmonary function during ex vivo lung perfusion was not predictive of outcomes after transplantation.

Expanding the donor pool: donation after cardiac death

Lung transplantation (LTx) is the definitive treatment of patients with end-stage lung disease. Availability of donor lungs remains the primary limitation and leads to substantial wait-list mortality. Efforts to expand the donor pool have included a resurgence of interest in the use of donation after cardiac death (DCD) lungs. Unique in its physiology, lung viability seems more tolerant to the variable durations of ischemia that occur in DCD donors. Initial experience with DCD LTx is promising and, in combination with ex vivo lung perfusion systems, seems a valuable opportunity to expand the lung donor pool.

Interim report of the Japanese original donor evaluation and management system: the medical consultant system

PURPOSE

Lung transplantation (LTx) is an established therapy for end-stage lung failure. However, in Japan, the donor organ shortage is extremely severe compared with other developed countries, because of the strict Japanese Organ Transplantation Law. To maximize LTx opportunities in Japan, we have established a special donor evaluation and management system termed the medical consultant (MC) system.

METHODS

Data from 171 lung donor candidates registered in Japan from May 1998 to May 2012 were obtained and investigated in a retrospective manner. The candidates were separated into the non-MC-intervened and MC-intervened groups, and then data regarding the PaO2/FiO2 ratio, donation rate and organ survival rate were analyzed and compared between the groups.

RESULTS

The PaO2/FiO2 ratio of the MC-intervened group was ameliorated from the time of first brain death diagnosis to organ harvest. Although the base condition of the MC-intervened group was significantly worse than that of the non-MC-intervened group, the donation rates showed no significant difference (0.64 and 0.66, respectively; p = 0.89). There was a difference in the organ survival rate between the non-MC and MC-intervened groups (5-year survival rates of 67.2 and 88.3 %, respectively; p = 0.16).

CONCLUSION

The MC system used for organ donor evaluation and management in Japan has achieved acceptable interim results.

Lung donor selection criteria

The criteria that define acceptable physiologic and social parameters for lung donation have remained constant since their empiric determination in the 1980s. These criteria include a donor age between 25-40, a arterial partial pressure of oxygen (PaO2)/FiO2 ratio greater than 350, no smoking history, a clear chest X-ray, clean bronchoscopy, and a minimal ischemic time. Due to the paucity of organ donors, and the increasing number of patients requiring lung transplant, finding a donor that meets all of these criteria is quite rare. As such, many transplants have been performed where the donor does not meet these stringent criteria. Over the last decade, numerous reports have been published examining the effects of individual acceptance criteria on lung transplant survival and graft function. These studies suggest that there is little impact of the historical criteria on either short or long term outcomes. For age, donors should be within 18 to 64 years old. Gender may relay benefit to all female recipients especially in male to female transplants, although results are mixed in these studies. Race matched donor/recipients have improved outcomes and African American donors convey worse prognosis. Smoking donors may decrease recipient survival post transplant, but provide a life saving opportunity for recipients that may otherwise remain on the transplant waiting list. No specific gram stain or bronchoscopic findings are reflected in recipient outcomes. Chest radiographs are a poor indicator of lung donor function and should not adversely affect organ usage aside for concerns over malignancy. Ischemic time greater than six hours has no documented adverse effects on recipient mortality and should not limit donor retrieval distances. Brain dead donors and deceased donors have equivalent prognosis. Initial PaO2/FiO2 ratios less than 300 should not dissuade donor organ usage, although recruitment techniques should be implemented with intent to transplant.

Ex vivo lung perfusion allows successful transplantation of donor lungs from hanging victims

BACKGROUND

Donor lungs acquired from victims of asphyxiation by hanging are not routinely used for lung transplantation because of the associated lung injury. Ex vivo lung perfusion (EVLP) is a technique to evaluate marginal donor lungs before transplantation. We report here our experience with the use of EVLP in donor lungs procured from victims of asphyxia by hanging.

METHODS

Lungs from 5 donors who became brain dead secondary to hanging were evaluated by EVLP. Donor organs were perfused according to trial protocol. Donor lungs were accepted for transplantation if they maintained a PaO2 greater than or equal to 350 mm Hg, had a clear roentgenogram, and had no significant worsening of physiologic metrics.

RESULTS

Perfused organs included single and double lung blocs, and all were perfused without technical incident. Three of the 5 donor organs evaluated met criteria for transplantation after 3 hours of EVLP and were transplanted. Donor organs rejected for transplantation showed either signs of worsening PaO2 or deterioration of physiologic metrics. There were no intraoperative complications in the patients who underwent transplantation, and all were alive at 30 days.

CONCLUSIONS

We report here the successful use of EVLP to assess donor lungs acquired from victims of asphyxiation by hanging. The use of EVLP in this particular group of donors has the potential to expand the available donor pool. We demonstrate that EVLP is a viable option for evaluating the function of lung allografts before transplantation and would recommend that all donor lungs obtained from hanging victims undergo EVLP to assess their suitability for transplantation.

A standardized model of brain death, donor treatment, and lung transplantation for studies on organ preservation and reconditioning

BACKGROUND

We set a model of brain death, donor management, and lung transplantation for studies on lung preservation and reconditioning before transplantation.

METHODS

Ten pigs (39.7 ± 5.9 Kg) were investigated. Five animals underwent brain death and were treated as organ donors; the lungs were then procured and cold stored (Ischemia). Five recipients underwent left lung transplantation and post-reperfusion follow-up (Graft). Cardiorespiratory and metabolic parameters were collected. Lung gene expression of cytokines (tumor necrosis factor alpha (TNFα), interleukin-1 beta (IL-1β), interleukin-6 (IL-6), interferon gamma (IFNγ), high mobility group box-1 (HMGB-1)), chemokines (chemokine CC motif ligand-2 (CCL2-MCP-1), chemokine CXC motif ligand-10 (CXCL-10), interleukin-8 (IL-8)), and endothelial activation markers (endothelin-1 (EDN-1), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), selectin-E (SELE)) was assessed by real-time polymerase chain reaction (PCR).

RESULTS

Tachycardia and hypertension occurred during brain death induction; cardiac output rose, systemic vascular resistance dropped (P < 0.05), and diabetes insipidus occurred. Lung-protective ventilation strategy was applied: 9 h after brain death induction, PaO2 was 192 ± 12 mmHg at positive end-expiratory pressure (PEEP) 8.0 ± 1.8 cmH2O and FiO2 of 40%; wet-to-dry ratio (W/D) was 5.8 ± 0.5, and extravascular lung water (EVLW) was 359 ± 80 mL. Procured lungs were cold-stored for 471 ± 24 min (Ischemia) at the end of which W/D was 6.1 ± 0.9. Left lungs were transplanted and reperfused (warm ischemia 98 ± 14 min). Six hours after controlled reperfusion, PaO2 was 192 ± 23 mmHg (PEEP 8.7 ± 1.5 cmH2O, FiO2 40%), W/D was 5.6 ± 0.4, and EVLW was 366 ± 117 mL. Levels of IL-8 rose at the end of donor management (BD, P < 0.05); CCL2-MCP-1, IL-8, HMGB-1, and SELE were significantly altered after reperfusion (Graft, P < 0.05).

CONCLUSIONS

We have set a standardized, reproducible pig model resembling the entire process of organ donation that may be used as a platform to test in vivo and ex vivo strategies of donor lung optimization before transplantation.

Ex vivo lung perfusion to improve donor lung function and increase the number of organs available for transplantation

This paper describes the initial clinical experience of ex vivo lung perfusion (EVLP) at the Fondazione Ca’ Granda in Milan between January 2011 and May 2013. EVLP was considered if donor PaO₂/FiO₂ was below 300 mmHg or if lung function was doubtful. Donors with massive lung contusion, aspiration, purulent secretions, pneumonia, or sepsis were excluded. EVLP was run with a low-flow, open atrium and low hematocrit technique. Thirty-five lung transplants from brain death donors were performed, seven of which after EVLP. EVLP donors were older (54 ± 9 years vs. 40 ± 15 years, EVLP versus Standard, P < 0.05), had lower PaO₂/FiO₂ (264 ± 78 mmHg vs. 453 ± 119 mmHg, P < 0.05), and more chest X-ray abnormalities (P < 0.05). EVLP recipients were more often admitted to intensive care unit as urgent cases (57% vs. 18%, P = 0.05); lung allocation score at transplantation was higher (79 [40–84] vs. 39 [36–46], P < 0.05). After transplantation, primary graft dysfunction (PGD₇₂ grade 3, 32% vs. 28%, EVLP versus Standard, P = 1), mortality at 30 days (0% vs. 0%, P = 1), and overall survival (71% vs. 86%, EVLP versus Standard P = 0.27) were not different between groups. EVLP enabled a 20% increase in available donor organs and resulted in successful transplants with lungs that would have otherwise been rejected (ClinicalTrials.gov number: NCT01967953).

Clinical grade allogeneic human mesenchymal stem cells restore alveolar fluid clearance in human lungs rejected for transplantation

The lack of suitable donors for all solid-organ transplant programs is exacerbated in lung transplantation by the low utilization of potential donor lungs, due primarily to donor lung injury and dysfunction, including pulmonary edema. The current studies were designed to determine if intravenous clinical-grade human mesenchymal stem (stromal) cells (hMSCs) would be effective in restoring alveolar fluid clearance (AFC) in the human ex vivo lung perfusion model, using lungs that had been deemed unsuitable for transplantation and had been subjected to prolonged ischemic time. The human lungs were perfused with 5% albumin in a balanced electrolyte solution and oxygenated with continuous positive airway pressure. Baseline AFC was measured in the control lobe and if AFC was impaired (defined as <10%/h), the lungs received either hMSC (5 × 10(6) cells) added to the perfusate or perfusion only as a control. AFC was measured in a different lung lobe at 4 h. Intravenous hMSC restored AFC in the injured lungs to a normal level. In contrast, perfusion only did not increase AFC. This positive effect on AFC was reduced by intrabronchial administration of a neutralizing antibody to keratinocyte growth factor (KGF). Thus, intravenous allogeneic hMSCs are effective in restoring the capacity of the alveolar epithelium to remove alveolar fluid at a normal rate, suggesting that this therapy may be effective in enhancing the resolution of pulmonary edema in human lungs deemed clinically unsuitable for transplantation.

Clinical neurology in lung transplantation

Lung transplantation is the only established therapeutic option for several end-stage respiratory diseases. Limited mostly by lack of suitable allografts, the results have measurably improved over the last decade. Numerous surgical and pharmaceutical improvements have had positive impact on outcomes. The potential for critical care issues and the need for interdisciplinary management remains paramount. Cardiac, renal, and metabolic complications are frequently encountered in the acute postoperative phase. Allograft rejection and infectious diseases as well as problems related to immunosuppressive regimen are seen later after lung transplantation. Neurologic manifestations with a range of etiologies are discussed here in this context.

Extended recipients but not extended donors are associated with poor outcomes following lung transplantation

OBJECTIVES

Extended donors (EDs) are safely used to increase the donor pool in lung transplantation (LT), but their influence in critically ill patients (extended recipients [ERs]) remains controversial. We compared LT outcomes matching optimal donors (ODs) or EDs with optimal recipients (ORs) or ERs.

METHODS

Three hundred and sixty-five LTs were reviewed. ED criteria: age >55, PaO2/FiO2 < 350 mmHg, pulmonary infiltrates/purulent secretions and ischaemic times >6 h (single LT [SLT]) and >9 h (double LT [DLT]). ER criteria: pulmonary fibrosis or pulmonary hypertension, pretransplant intubation, age >60 years and bypass >2 h. Four groups were created: Group 1 (OD/OR), Group 2 (OD/ER), Group 3 (ED/OR) and Group 4 (ED/ER). Thirty-day mortality, primary graft dysfunction (PGD), onset of bronchiolitis obliterans syndrome (BOS), long-term survival and other transplant outcomes were compared between OD and ED, OR and ER and among the four groups of study.

RESULTS

There were 151 SLTs and 214 DLTs. Donors: OD (n = 229) vs ED (n = 136); PGD 8 vs 10% (P = 0.43); 30-day mortality 19 vs 20% (P = 0.53) and survival (1, 5, 10 and 15 years) 67, 47, 34, 26 vs 69, 53, 46 and 29% (P = 0.33). Recipients: OR (n = 182) vs ER (n = 183); PGD 7 vs 10% (P = 0.10); 30-day mortality 15 vs 23% (P = 0.04) and survival (1, 5, 10 and 15 years): 73, 57, 46, 30 vs 61, 42, 29 and 23% (P = 0.002). Four donor/recipient (D/R) groups: Group 1 (n = 122), Group 2 (n = 106), Group 3 (n = 61), Group 4 (n = 76); PGD 10, 6, 3 and 16% (P = 0.05); 30-day mortality 13, 26, 19 and 20%, respectively (P = 0.13); survival (1, 5, 10 and 15 years) 74, 55, 44 and 35% (Group 1), 55, 39, 22 and 16% (Group 2), 70, 59, 48 and 26% (Group 3) and 68, 47, 37 and 22% (Group 4) (P = 0.004). No differences in the onset of BOS were observed among the four study groups.

CONCLUSIONS

LT in critically ill recipients is associated with poor early and long-term outcomes, irrespective of the quality of the donor and length of ischaemic times.

Advances in lung preservation

After a brief review of conventional lung preservation, this article discusses the rationale behind ex vivo lung perfusion and how it has shifted the paradigm of organ preservation from conventional static cold ischemia to the utilization of functional normothermia, restoring the lung's own metabolism and its reparative processes. Technical aspects and previous clinical experience as well as opportunities to address specific donor organ injuries in a personalized medicine approach are also reviewed.