T.N. Machuca

Experience with the first 50 ex vivo lung perfusions in clinical transplantation.

OBJECTIVE Normothermic ex vivo lung perfusion is a novel method to evaluate and improve the function of injured donor lungs. We reviewed our experience with 50 consecutive transplants after ex vivo lung perfusion. METHODS A retrospective study using prospectively collected data was performed. High-risk brain death donor lungs (defined as Pao(2)/Fio(2) <300 mm Hg or lungs with radiographic or clinical findings of pulmonary edema) and lungs from cardiac death donors were subjected to 4 to 6 hours of ex vivo lung perfusion. Lungs that achieved stable airway and vascular pressures and Pao(2)/Fio(2) greater than 400 mm Hg during ex vivo lung perfusion were transplanted. The primary end point was the incidence of primary graft dysfunction grade 3 at 72 hours after transplantation. End points were compared with lung transplants not treated with ex vivo lung perfusion (controls). RESULTS A total of 317 lung transplants were performed during the study period (39 months). Fifty-eight ex vivo lung perfusion procedures were performed, resulting in 50 transplants (86% use). Of these, 22 were from cardiac death donors and 28 were from brain death donors. The mean donor Pao(2)/Fio(2) was 334 mm Hg in the ex vivo lung perfusion group and 452 mm Hg in the control group (P = .0001). The incidence of primary graft dysfunction grade 3 at 72 hours was 2% in the ex vivo lung perfusion group and 8.5% in the control group (P = .14). One patient (2%) in the ex vivo lung perfusion group and 7 patients (2.7%) in the control group required extracorporeal lung support for primary graft dysfunction (P = 1.00). The median time to extubation, intensive care unit stay, and hospital length of stay were 2, 4, and 20 days, respectively, in the ex vivo lung perfusion group and 2, 4, and 23 days, respectively, in the control group (P > .05). Thirty-day mortality (4% in the ex vivo lung perfusion group and 3.5% in the control group, P = 1.00) and 1-year survival (87% in the ex vivo lung perfusion group and 86% in the control group, P = 1.00) were similar in both groups. CONCLUSIONS Transplantation of high-risk donor lungs after 4 to 6 hours of ex vivo lung perfusion is safe, and outcomes are similar to those of conventional transplants. Ex vivo lung perfusion improved our center use of donor lungs, accounting for 20% of our current lung transplant activity.

Physiologic assessment of the ex vivo donor lung for transplantation

BACKGROUND The evaluation of donor lungs by normothermic ex vivo acellular perfusion has improved the safety of organ utilization. However, this strategy requires a critical re-evaluation of the parameters used to assess lungs during ex vivo perfusion compared with those traditionally used to evaluate the donor lung in vivo. Using a porcine model, we studied the physiology of acellular lung perfusion with the aim of improving the accuracy of clinical ex vivo evaluation. METHODS Porcine lungs after 10 hours of brain death and 24 hours of cold ischemia and uninjured control lungs were perfused for 12 hours and then transplanted. PaO2, compliance, airway pressure and pulmonary vascular resistance were measured. Ventilation with 100% nitrogen and addition of red blood cells to the perfusate were used to clarify the physiologic disparities between in vivo blood perfusion and ex vivo acellular perfusion. RESULTS During 12 hours of ex vivo perfusion, injured lungs developed edema with decreased compliance and increased airway pressure, but ex vivo PO2 remained stable. After transplantation, injured lungs demonstrated high vascular resistance and poor PaO2. A reduced effect of shunt on ex vivo lung perfusion PO2 was found to be attributable to the linearization of the relationship between oxygen content and PO2, which occurs with acellular perfusate. CONCLUSIONS Ex vivo PO2 may not be the first indication of lung injury and, taken alone, may be misleading in assessing the ex vivo lung. Thus, evaluation of other physiologic parameters takes on greater importance.

Lung Transplantation With Donation After Circulatory Determination of Death Donors and the Impact of Ex Vivo Lung Perfusion

The growing demand for suitable lungs for transplantation drives the quest for alternative strategies to expand the donor pool. The aim of this study is to evaluate the outcomes of lung transplantation (LTx) with donation after circulatory determination of death (DCDD) and the impact of selective ex vivo lung perfusion (EVLP). From 2007 to 2013, 673 LTx were performed, with 62 (9.2%) of them using DCDDs (seven bridged cases). Cases bridged with mechanical ventilation/extracorporeal life support were excluded. From 55 DCDDs, 28 (51%) underwent EVLP. Outcomes for LTx using DCDDs and donation after neurological determination of death (DNDD) donors were similar, with 1 and 5‐year survivals of 85% and 54% versus 86% and 62%, respectively (p = 0.43). Although comparison of survival curves between DCDD + EVLP versus DCDD‐no EVLP showed no significant difference, DCDD + EVLP cases presented shorter hospital stay (median 18 vs. 23 days, p = 0.047) and a trend toward shorter length of mechanical ventilation (2 vs. 3 days, p = 0.059). DCDDs represent a valuable source of lungs for transplantation, providing similar results to DNDDs. EVLP seems an important technique in the armamentarium to safely increase lung utilization from DCDDs; however, further studies are necessary to better define the role of EVLP in this context.

Metabolomic Heterogeneity of Pulmonary Arterial Hypertension

Although multiple gene and protein expression have been extensively profiled in human pulmonary arterial hypertension (PAH), the mechanism for the development and progression of pulmonary hypertension remains elusive. Analysis of the global metabolomic heterogeneity within the pulmonary vascular system leads to a better understanding of disease progression. Using a combination of high-throughput liquid-and-gas-chromatography-based mass spectrometry, we showed unbiased metabolomic profiles of disrupted glycolysis, increased TCA cycle, and fatty acid metabolites with altered oxidation pathways in the human PAH lung. The results suggest that PAH has specific metabolic pathways contributing to increased ATP synthesis for the vascular remodeling process in severe pulmonary hypertension. These identified metabolites may serve as potential biomarkers for the diagnosis of PAH. By profiling metabolomic alterations of the PAH lung, we reveal new pathogenic mechanisms of PAH, opening an avenue of exploration for therapeutics that target metabolic pathway alterations in the progression of PAH.

Protein expression profiling predicts graft performance in clinical ex vivo lung perfusion.

OBJECTIVES To study the impact of ex vivo lung perfusion (EVLP) on cytokines, chemokines, and growth factors and their correlation with graft performance either during perfusion or after transplantation. BACKGROUND EVLP is a modern technique that preserves lungs on normothermia in a metabolically active state. The identification of biomarkers during clinical EVLP can contribute to the safe expansion of the donor pool. METHODS High-risk brain death donors and donors after cardiac death underwent 4 to 6 hours EVLP. Using a multiplex magnetic bead array assay, we evaluated analytes in perfusate samples collected at 1 hour and 4 hours of EVLP. Donor lungs were divided into 3 groups: (I) Control: bilateral transplantation with good early outcome [absence of primary graft dysfunction- (PGD) grade 3]; (II) PGD3: bilateral transplantation with PGD grade 3 anytime within 72 hours; (III) Declined: lungs unsuitable for transplantation after EVLP. RESULTS Of 50 cases included in this study, 27 were in Control group, 7 in PGD3, and 16 in Declined. From a total of 51 analytes, 34 were measurable in perfusates. The best marker to differentiate declined lungs from control lungs was stem cell growth factor -β [P < 0.001, AUC (area under the curve) = 0.86] at 1 hour. The best markers to differentiate PGD3 cases from controls were interleukin-8 (P < 0.001, AUC = 0.93) and growth-regulated oncogene-α (P = 0.001, AUC = 0.89) at 4 hours of EVLP. CONCLUSIONS Perfusate protein expression during EVLP can differentiate lungs with good outcome from lungs PGD3 after transplantation. These perfusate biomarkers can be potentially used for more precise donor lung selection improving the outcomes of transplantation.

Functional outcomes and quality of life after normothermic ex vivo lung perfusion lung transplantation

BACKGROUND Ex vivo lung perfusion (EVLP) is an effective method to assess and improve the function of otherwise unacceptable lungs, alleviating the shortage of donor lungs. The early results with EVLP have been encouraging, but longer-term results, including functional and patient-reported outcomes, are not well characterized. METHODS This retrospective single-center study included all lung transplants performed between September 2008 and December 2012. We investigated whether survival or rate of chronic lung allograft dysfunction (CLAD) differed in recipients of EVLP-treated lungs compared with contemporaneous recipients of conventional donor lungs. We also studied functional (highest forced expiratory volume in 1 second predicted, change in 6-minute walk distance, number of acute rejection episodes) and quality of life outcomes. RESULTS Of 403 lung transplants that were performed, 63 patients (15.6%) received EVLP-treated allografts. Allograft survival for EVLP and conventional donor lung recipients was 79% vs 85%, 71% vs 73%, and 58% vs 57% at 1, 3, and 5 years after transplant, respectively (log-rank p = not significant). Freedom from CLAD was also similar (log-rank p = 0.53). There were no significant differences in functional outcomes such as highest forced expiratory volume in 1 second predicted (76.5% ± 23.8% vs 75.8% ± 22.8%, p = 0.85), change in 6-minute walk distance (194 ± 108 meters vs 183 ± 126 meters, p = 0.57), or the number of acute rejection episodes (1.5 ± 1.4 vs 1.3 ± 1.3, p = 0.36). The EVLP and conventional donor groups both reported a significantly improved quality of life after transplantation, but there was no intergroup difference. CONCLUSION EVLP is a safe and effective method of assessing and using high-risk donor lungs before transplantation and leads to acceptable long-term survival, graft function, and improvements of quality of life that are comparable with conventionally selected donor lungs.

Injury-Specific Ex Vivo Treatment of the Donor Lung: Pulmonary Thrombolysis Followed by Successful Lung Transplantation

Ex vivo lung perfusion (EVLP) is a technique that allows detailed assessment and treatment of high-risk donor lungs (1). It enables a period of normothermic functional preservation to restore lung metabolism and provides a window for more accurate diagnosis and therapy. Pulmonary embolism (PE) is a frequent finding in organ donors (2). The simple recovery of macroscopic thrombi during retrograde preservation flush is associated with worse outcomes after lung transplantation (3). Although there have been anecdotal cases of pulmonary embolectomy after organ procurement or thrombolytic therapy performed in donors with massive PE, we report, for the first time, therapeutic ex vivo thrombolysis followed by clinical transplantation (4–7).

Distinct expression patterns of alveolar "alarmins" in subtypes of chronic lung allograft dysfunction.

The long‐term success of lung transplantation is limited by chronic lung allograft dysfunction (CLAD). The purpose of this study was to investigate the alveolar alarmin profiles in CLAD subtypes, restrictive allograft syndrome (RAS) and bronchiolitis obliterans syndrome (BOS). Bronchoalveolar lavage (BAL) samples were collected from 53 recipients who underwent double lung or heart‐lung transplantation, including patients with RAS (n = 10), BOS (n = 18) and No CLAD (n = 25). Protein levels of alarmins such as S100A8, S100A9, S100A8/A9, S100A12, S100P, high‐mobility group box 1 (HMGB1) and soluble receptor for advanced glycation end products (sRAGE) in BAL fluid were measured. RAS and BOS showed higher expressions of S100A8, S100A8/A9 and S100A12 compared with No CLAD (p < 0.0001, p < 0.0001, p < 0.0001 in RAS vs. No CLAD, p = 0.0006, p = 0.0044, p = 0.0086 in BOS vs. No CLAD, respectively). Moreover, RAS showed greater up‐regulation of S100A9, S100A8/A9, S100A12, S100P and HMGB1 compared with BOS (p = 0.0094, p = 0.038, p = 0.041, p = 0.035 and p = 0.010, respectively). sRAGE did not show significant difference among the three groups (p = 0.174). Our results demonstrate distinct expression patterns of alveolar alarmins in RAS and BOS, suggesting that RAS and BOS may represent biologically different subtypes. Further refinements in biologic profiling will lead to a better understanding of CLAD.

Solid phase microextraction fills the gap in tissue sampling protocols.

Metabolomics and biomarkers discovery are an integral part of bioanalysis. However, untargeted tissue analysis remains as the bottleneck of such studies due to the invasiveness of sample collection, as well as the laborious and time-consuming sample preparation protocols. In the current study, technology integrating in vivo sampling, sample preparation and global extraction of metabolites--solid phase microextraction was presented and evaluated during liver and lung transplantation in pig model. Sampling approaches, including selection of the probe, transportation, storage conditions and analyte coverage were discussed. The applicability of the method for metabolomics studies was demonstrated during lung transplantation experiments.

Ex vivo lung perfusion.

Lung transplantation (LTx) is an established treatment option for eligible patients with end-stage lung disease. Nevertheless, the imbalance between suitable donor lungs available and the increasing number of patients considered for LTx reflects in considerable waitlist mortality. Among potential alternatives to address this issue, ex vivo lung perfusion (EVLP) has emerged as a modern preservation technique that allows for more accurate lung assessment and also improvement of lung function. Its application in high-risk donor lungs has been successful and resulted in safe expansion of the donor pool. This article will: (I) review the technical details of EVLP; (II) the rationale behind the method; (III) report the worldwide clinical experience with the EVLP, including the Toronto technique and others; (IV) finally, discuss the growing literature on EVLP application for donation after cardiac death (DCD) lungs.