Prolonged EVLP Using OCS Lung: Cellular and Acellular Perfusates

Outcomes of donation after circulatory death (DCD) and ex-vivo lung perfusion (EVLP) lung transplantation

BACKGROUND

Donation after circulatory death (DCD) and ex-vivo lung perfusion (EVLP) have been adopted to expand the donor pool in lung transplantation, but outcomes data have been conflicting. This study explores outcomes of DCD and EVLP lung transplantation in the modern era.

METHODS

The United Network for Organ Sharing database was queried for adult lung transplants from January 1, 2015 to March 1, 2023. Loss to follow-up, multiorgan, and prior lung transplants were excluded. DCD versus donation after brain death (DBD) lung transplants were compared with subgroup analysis +/- EVLP. Outcomes were survival and postoperative complications.

RESULTS

The study included 1,103 DCD (221 with EVLP and 882 without) and 17,973 DBD lung transplants (524 with EVLP and 17,449 without). Median follow-up was 3 years. DCD donors were less likely to be CDC high risk (19.3% vs 24.1%, p < 0.001), have purulence on bronchoscopy (13.3% vs 18.3%, p < 0.001), or infiltrates on chest X-ray (66.7% vs 67.8%, p = 0.013). EVLP was more likely to be used for DCD transplants (20.0% vs 2.9%, p < 0.001). After transplant, DCD recipients were more likely to be reintubated (24.3% vs 18.5%, p < 0.001) and require ECMO within 72 hours (14.9% vs 7.8%, p < 0.001), and DCD donation was an independent risk factor for these complications on multivariable logistic regression. Overall survival did not differ significantly between DCD and DBD transplants on adjusted survival analysis in the early or modern era (p = 0.774 and p = 0.468, respectively). On subgroup analysis, the DCD+EVLP cohort had significantly worse survival in the modern era, which remained significant after adjusting for donor and recipient factors (p = 0.005). EVLP was an independent risk factor for graft failure in the DCD cohort (hazard ratio [HR] 1.33, 95% confidence interval [CI] 1.00-1.77, p = 0.047) but did not significantly affect DBD graft survival (p = 0.870). Risk factors for graft failure and mortality in the DCD+EVLP cohort included pulmonary hypertension (HR 77.5, 95% CI 6.15-979, p < 0.001), transfusion before transplant (HR 2.60, 95% CI 1.07-6.31, p = 0.035), elevated creatinine (HR 2.82, 95% CI 1.34-5.90, p = 0.006), and higher allocation score (HR 1.02, 95% CI 1.00-1.04, p = 0.017) CONCLUSIONS: Study findings suggest increased risks of mortality and perioperative complications following transplantation with DCD lungs that have undergone EVLP. DCD lung transplantation without EVLP confers equivalent survival but with some increase in perioperative complications. Further investigation and careful recipient selection are warranted to optimize the use of these extended criteria donors in the modern era.

Organ preservation: current limitations and optimization approaches

Despite the annual rise in patients with end-stage diseases necessitating organ transplantation, the scarcity of high-quality grafts constrains the further development of transplantation. The primary causes of the graft shortage are the scarcity of standard criteria donors, unsatisfactory organ preservation strategies, and mismatching issues. Organ preservation strategies are intimately related to pre-transplant graft viability and the incidence of adverse clinical outcomes. Static cold storage (SCS) is the current standard practice of organ preservation, characterized by its cost-effectiveness, ease of transport, and excellent clinical outcomes. However, cold-induced injury during static cold preservation, toxicity of organ preservation solution components, and post-transplantation reperfusion injury could further exacerbate graft damage. Long-term ex vivo dynamic machine perfusion (MP) preserves grafts in a near-physiological condition, evaluates graft viability, and cures damage to grafts, hence enhancing the usage and survival rates of marginal organs. With the increased use of extended criteria donors (ECD) and advancements in machine perfusion technology, static cold storage is being gradually replaced by machine perfusion. This review encapsulates the latest developments in cryopreservation, subzero non-freezing storage, static cold storage, and machine perfusion. The emphasis is on the injury mechanisms linked to static cold storage and optimization strategies, which may serve as references for the optimization of machine perfusion techniques.

Negative Pressure Ventilation Ex-Situ Lung Perfusion Preserves Porcine and Human Lungs for 36-Hours

INTRODUCTION

Preclinically, 24-hour continuous Ex-Situ Lung Perfusion (ESLP) is the longest duration achieved in large animal models and rejected human lungs. Here, we present our 36-hour Negative Pressure Ventilation (NPV)-ESLP protocol applied to porcine and rejected human lungs.

METHODS

Five sets of donor domestic pig lungs (45-55 kg) underwent 36-hour NPV-ESLP. Two sets of clinically rejected human lungs were preserved on 36-hour NPV-ESLP. Graft function was assessed via physiologic parameters, edema formation, and cytokine profiles.

RESULTS

Porcine and human lung function was stable with mean partial pressure of oxygen divided by the fraction of inspired oxygen (PaO2/FiO2; PF) ratios throughout preservation of 473±11.79 and 554.7±13.26, respectively (mean±standard error of the mean). In porcine lungs, mean compliance (Cdyn) during ESLP was 33.96±2.18, pulmonary artery pressure (PAP) 13.03±0.53, and pulmonary vascular resistance (PVR) 481.20 ±21.86. In human lungs, mean Cdyn was 82.68±3.54, PAP 6.00±0.33, and PVR 184.00±9.71. Average percentage weight-gain was 34.47±13.22 in porcine lungs and 116.3±6.65 in rejected human lungs.

CONCLUSION

NPV-ESLP can preserve porcine lungs and human lungs for 36-hours with acceptable physiologic function. Greater weight-gain in the human lungs is likely due to prolonged ischemic time prior to ESLP and use of an acellular perfusate. Continuous 36-hour NPV-ESLP could support therapies for endothelial protection and mitigate fluid accumulation.

Short-term and long-term outcomes of lung transplantation from marginal donors: a single-center retrospective study

Background

To expand the donor pool, medical centers worldwide are applying marginal donor lungs in clinical settings. We carried out this research to reveal the short-term and long-term outcomes of marginal lung donor transplantation.

Methods

We performed retrospective research using data from patients who underwent lung transplantation (LT) in The Affiliated Wuxi People's Hospital of Nanjing Medical University, Jiangsu Province, China, between 2018 and 2022 to compare the short-term and long-term outcomes of standard donors and marginal donors.

Results

A total of 553 cases were incorporated in this study. The perioperative mortality of recipients who received marginal donor lungs was around 20.8%, compared with 13.4% in the standard donor recipients (P=0.03). There were no significant differences between the two groups in terms of mechanical ventilation or extracorporeal membrane oxygenation (ECMO), length of intensive care unit and hospital stay, occurrence of primary graft dysfunction, and prevalence of acute rejection. The 1-year survival rate for recipients in the standard group and marginal group was 71.7% and 54.2% (P<0.001), respectively. There was a worse survival rate in the subgroups of age >55 years, smoking ≥20 pack-years, and abnormal chest radiographs; however, the 1-year survival rate in the subgroup analysis of donors with ratio of arterial oxygen partial pressure to fraction of inspired oxygen (PaO2/FiO2) <300 mmHg and purulent secretions on bronchoscopy was not significantly different.

Conclusions

Our findings suggest that marginal donor recipients can expect to have a lower survival rate than standard donor recipients. However, marginal lung transplant recipients could also gain benefit equivalent to that provided by standard donor LTs in both the short- and long-term when proper assessment and management strategies are implemented.

Mild Permissive Alkalosis Improves Outcomes in Porcine Negative Pressure Ventilation Ex-Situ Lung Perfusion

BACKGROUND

Ex-Situ Lung Perfusion (ESLP) employs a membrane deoxygenator and mixed (N2/O2/CO2) or pure sweep gas (CO2) to target venous blood gas composition with physiologic pCO2 and pH. Clinically, mild permissive alkalosis counteracts elevated pulmonary vascular resistance (PVR) to improve perfusion. Increased PVR and pulmonary artery pressure (PAP) during ESLP mirrors rising pro-inflammatory cytokines. Increased hydrostatic pressure worsens edema and lung function. We report improved ESLP outcomes using mild permissive alkalosis.

METHODS

Twelve juvenile pig lungs underwent 12-hour Negative Pressure Ventilation (NPV)-ESLP with a physiologic pH (Control: pH 7.35-7.45, n=6) or mild permissive alkalosis (pH+: pH 7.45-7.55, n=6) by varying sweep CO2 delivery. Three left lungs per group were transplanted and assessed over 4-hours.

RESULTS

Five Control lungs failed on ESLP due to high PAPs, low compliance, and poor oxygenation. Repeat Controls (n=6) were performed to attain 12-hours of ESLP. There were no failures in the pH+ group. Results are pH+ vs Control. Oxygenation (PaO2/FiO2 454.2 vs 438.2; P = .37) and dynamic compliance (21.38 vs 22.22 mL/cmH2O; P = .41) were stable over 12-hour NPV-ESLP. Mean evaluation pH/pCO2/HCO3- was 7.50/15.6/14.5 vs 7.41/38.7/24.7. Control lungs required repeat THAM and milrinone boluses on ESLP to prevent acidosis and treat elevated PVR; this was not necessary in the pH+ group. Weight-gain/hour was similar (1.23% vs 1.38%; P = .37). Mean left lung PF ratios 4-hours post-transplantation were 301 mmHg vs 196 mmHg (P = .11). Control TNF-⍺ and IL-6 perfusate concentrations were significantly greater.

CONCLUSIONS

Mild permissive alkalosis porcine NPV-ESLP demonstrated more reliable preservation with reduced inflammation compared to a physiologic pH strategy.

Comparison of Ex Vivo Lung Perfusion, With or Without Albumin, With Static Cold Storage in a Rat Ex Vivo Lung Perfusion Model

Ex vivo lung perfusion is an alternative to static cold storage for lung preservation in clinical lung transplantation. This study aimed to compare ex vivo lung perfusion with an acellular solution versus static cold storage and to assess the role of albumin as an additive to the acellular perfusion solution. Rat heart-lung blocks from Sprague-Dawley rats, after 1 hour of warm ischemia, were immersed in a low-potassium dextran solution for another hour. Blocks were then placed on ex vivo lung perfusion for 3 hours, with or without the addition of 70 g/L of albumin. Parameters such as gas exchange, dynamic lung compliance, and pulmonary vascular resistance were evaluated every 30 minutes. Control lungs were preserved in low-potassium dextran solution at 4 °C for 4 hours (static cold storage group). Lung injury was assessed using wet-to-dry ratio, histology, immunohistochemistry, and TUNEL assay. Pulmonary vascular resistance significantly decreased between 30 and 60 minutes of ex vivo lung perfusion, whereas other lung function parameters remained stable throughout the 3 hours. No significant differences were observed between the ex vivo lung perfusion and ex vivo lung perfusion + albumin groups in terms of lung function or pathology assessment. Pathological findings indicated that ex vivo lung perfusion, with or without albumin, resulted in increased edema and apoptotic activity compared with lungs preserved by static cold storage. The addition of albumin to the ex vivo lung perfusion solution did not result in significant improvements in functional parameters or pathological findings.

Current Basic Research in Normothermic Machine Perfusion

BACKGROUND

Normothermic machine perfusion (NMP) is gradually being introduced into clinical transplantation to improve the quality of organs and increase utilisation. This review details current understanding of the underlying mechanistic effects of NMP in the heart, lung, liver, and kidney. It also considers recent advancements to extend the perfusion interval in these organs and the use of NMP to introduce novel therapeutic interventions, with a focus on organ modulation.

SUMMARY

The re-establishment of circulation during NMP leads to the upregulation of inflammatory and immune mediators, similar to an ischaemia-reperfusion injury response. The level of injury is determined by the condition of the organ, but inflammation may also be exacerbated by the passenger leucocytes that emerge from the organ during perfusion. There is evidence that damaged organs can recover and that prolonged NMP may be advantageous. In the liver, successful 7-day NMP has been achieved. The delivery of therapeutic agents to an organ can aid repair and be used to modify the organ to reduce immunogenicity or change the structure of the blood group antigens to create a universal donor blood group organ.

KEY MESSAGES

The application of NMP in organ transplantation is a growing area of research and is increasingly being used in the clinic. In the future, NMP may offer the opportunity to change practice. If organs can be preserved for days on an NMP system, transplantation may become an elective rather than an emergency procedure. The ability to introduce therapies during NMP is an effective way to treat an organ and avoid the complexity of treating the recipient.

Perfusate Exchange Does Not Improve Outcomes in 24-hour Ex Situ Lung Perfusion

BACKGROUND

Reliable 24-hour preservation is required to optimize the rehabilitation potential of Ex Situ Lung Perfusion (ESLP). Other ESLP protocols include fresh perfusate replacement to counteract an accumulation of deleterious by-products. We describe the results of our reliable 24-hour negative pressure ventilation (NPV)-ESLP protocol with satisfactory acute post-transplant outcomes and investigate perfusate exchange (PE) as a modification to enhance prolonged ESLP.

METHODS

Twelve pig lungs underwent 24 hours of NPV-ESLP using 1.5L of cellular perfusate (500 mL packed red blood cells and 1 L buffered perfusate). The Control (n = 6) had no PE; the PE (n = 6) had 500 mL replaced after 12 hours of NPV-ESLP with 1000 mL fresh perfusate. Three left lungs per group were transplanted.

RESULTS

Results are reported as Control vs PE (mean ± SEM). Both groups demonstrated stable and acceptable oxygenation during 24 hours of ESLP with final PF ratios of 527.5 ± 42.19 and 488.4 ± 35.38 (P = .25). Final compliance measurements were 20.52 ± 3.59 and 18.55 ± 2.91 (P = .34). There were no significant differences in pulmonary artery pressure after 24 hours of ESLP (10.02 ± 2.69 vs 14.34 ± 1.64, P = .10), and pulmonary vascular resistance only differed significantly at T12 (417.6 ± 53.06 vs 685.4 ± 81.19, P = .02). Percentage weight gain between groups was similar (24.32 ± 8.4 and 45.33 ± 7.76, P = .07). Post-transplant left lung oxygenation was excellent (327.3 ± 14.62 and 313.3 ± 15.38, P = .28). There was no significant difference in % weight gain of lungs post-transplant (22.20 ± 7.22 vs 14.36 ± 9.96, P = .28).

CONCLUSION

Acceptable lung function was maintained during 24-hour NPV-ESLP and post-transplant regardless of PE.

Impact of Hemoglobin Level in Ex Vivo Heart Perfusion on Donation After Circulatory Death Hearts: A Juvenile Porcine Experimental Model

BACKGROUND

Ex vivo heart perfusion (EVHP) of donation after circulatory death (DCD) hearts has become an effective strategy in adults; however, the small circulating volume in pediatrics poses the challenge of a low-hemoglobin (Hb) perfusate. We aimed to determine the impact of perfusate Hb levels during EVHP on DCD hearts using a juvenile porcine model.

METHODS

Sixteen DCD piglet hearts (11-14 kg) were reperfused for 4 h in unloaded mode followed by working mode. Metabolism, cardiac function, and cell damage were compared between the low-Hb (Hb, 5.0-5.9 g/dL; n = 8) and control (Hb, 7.5-8.4 g/dL; n = 8) groups. Between-group differences were evaluated using 2-sample t -tests or Fisher's Exact tests.

RESULTS

During unloaded mode, the low-Hb group showed lower myocardial oxygen consumption ( P  < 0.001), a higher arterial lactate level ( P  = 0.001), and worse systolic ventricular function ( P  < 0.001). During working mode, the low-Hb group had a lower cardiac output (mean, 71% versus 106% of normal cardiac output, P  = 0.010) and a higher arterial lactate level ( P  = 0.031). Adjusted cardiac troponin-I ( P  = 0.112) did not differ between the groups. Morphological myocyte injury in the left ventricle was more severe in the low-Hb group ( P  = 0.028).

CONCLUSIONS

Low-Hb perfusate with inadequate oxygen delivery induced anaerobic metabolism, resulting in suboptimal DCD heart recovery and declined cardiac function. Arranging an optimal perfusate is crucial to organ protection, and further endeavors to refine the priming volume of EVHP or the transfusion strategy are required.

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

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

Development of a Novel Optimized BioEnvironment for proLonged (NOBEL) ex vivo lung preservation

Current Ex Vivo Lung Perfusion (EVLP) systems are designed to support lungs outside of the body for up to 12 hours, allowing clinicians limited opportunity to assess organ function and viability prior to transplant. However, prolonged EVLP would allow for advanced time-dependent therapies such as immunomodulation, cell-based therapies and gene editing for donor lung repair and reconditioning. Therefore, we have developed a novel optimized bioenvironment for prolonged (NOBEL) EVLP to preserve a donor lung up to 30 hours. Three healthy swine donor lungs were used to optimize our NOBEL EVLP system. Several improvements over conventional blood-based EVLP protocols were used to prolong preservation including the following: (a) hypothermia to reduce metabolic waste and hemolysis, (b) dialysis to maintain pH, glucose and electrolyte levels at normal values, (c) proning using a biocompatible soft net lung support with axial lung rotation to reduce positional lung tissue damage, and (d) total parenteral nutrition to provide vital nutrients for cellular recovery. Our preliminary results show that these interventions were associated with improved lung oxygenation and gross morphology over that seen with a conventional EVLP protocol.

Porcine lungs perfused with three different flows using the 8-h open-atrium cellular ex vivo lung perfusion technique

The number of lung transplantations is limited due to the shortage of donor lungs fulfilling the standard criteria. The ex vivo lung perfusion (EVLP) technique provides the ability of re-evaluating and potentially improving and treating marginal donor lungs. Accordingly, the technique has emerged as an essential tool to increase the much-needed donor lung pool. One of the major EVLP protocols, the Lund protocol, characterized by high pulmonary artery flow (100% of cardiac output [CO]), an open atrium, and a cellular perfusate, has demonstrated encouraging short-EVLP duration results. However, the potential of the longer EVLP duration of the protocol is yet to be investigated, a duration which is considered necessary to rescue more marginal donor lungs in future. This study aimed to achieve stable 8-h EVLP using an open-atrium cellular model with three different pulmonary artery flows in addition to determining the most optimal flow in terms of best lung performance, including lung electrolytes and least lung edema formation, perfusate and tissue inflammation, and histopathological changes, using the porcine model. EVLP was performed using a flow of either 40% (n = 6), 80% (n = 6), or 100% (n = 6) of CO. No flow rate demonstrated stable 8-h EVLP. Stable 2-h EVLP was observed in all three groups. Insignificant deterioration was observed in dynamic compliance, peak airway pressure, and oxygenation between the groups. Pulmonary vascular resistance increased significantly in the 40% group (p < .05). Electrolytes demonstrated an insignificant worsening trend with longer EVLP. Interleukin-8 (IL-8) in perfusate and tissue, wet-to-dry weight ratio, and histopathological changes after EVLP were insignificantly time dependent between the groups. This study demonstrated that stable 8-h EVLP was not feasible in an open-atrium cellular model regardless of the flow of 40%, 80%, or 100% of CO. No flow was superior in terms of lung performance, lung electrolytes changes, least lung edema formation, minimal IL-8 expression in perfusate and tissue, and histopathological changes.

Technical Advances Targeting Multiday Preservation of Isolated Ex Vivo Lung Perfusion

Indications for ex vivo lung perfusion (EVLP) have evolved from assessment of questionable donor lungs to treatment of some pathologies and the logistics. Yet up to 3 quarters of donor lungs remain discarded across the globe. Multiday preservation of discarded human lungs on EVLP platforms would improve donor lung utilization rates via application of sophisticated treatment modalities, which could eventually result in zero waitlist mortality. The purpose of this article is to summarize advances made on the technical aspects of the protocols in achieving a stable multiday preservation of isolated EVLP. Based on the evidence derived from large animal and/or human studies, the following advances have been considered important in achieving this goal: ability to reposition donor lungs during EVLP; perfusate adsorption/filtration modalities; perfusate enrichment with plasma and/or donor whole blood, nutrients, vitamins, and amino acids; low-flow, pulsatile, and subnormothermic perfusion; positive outflow pressure; injury specific personalized ventilation strategies; and negative pressure ventilation. Combination of some of these advances in an automatized EVLP device capable of managing perfusate biochemistry and ventilation would likely speed up the processes of achieving multiday preservation of isolated EVLP.

Is timing everything? Examining operative time in lung transplants from 2006 to 2023

Background

Several studies have tried to find a link between timing of lung transplant surgery and patient outcomes. However, there has been conflicting results. This study sought to evaluate the association of operative times and recipient outcomes.

Methods

Primary adults lung transplants were identified from the United Network for Organ Sharing Database. Patients were stratified based on time of lung transplant: T1 (12 AM-6 AM); T2 (6 AM-12 PM); T3 (12 PM-6 PM); T4 (6 PM-12 AM). Groups were assessed with comparative statistics. Long-term survival was evaluated using Kaplan-Meier methods and a multivariate Cox proportional hazard model.

Results

Within the T4 group, there was a significant increase in length of stay and incidence of primary graft dysfunction, though minor. Unadjusted survival analysis with Kaplan-Meier methods demonstrated that there was no significant difference in long-term survival among the 4 groups (p = 0.55). Following adjustment, no operative time was independently associated with decreased long-term mortality. Variables that were significantly associated with increased long-term mortality included recipient diabetes, creatinine, hospitalization status, intensive care unit status, cigarette use, and donation after circulatory death donor status.

Conclusions

Though operative times during the T4 period were associated with increased peri-operative complications, this had no effect on long-term survival. While thoracic transplantation can safely occur no matter what time of day, transplantation should preferentially be performed during normal surgical work hours for the longevity and work life balance of transplant providers and surgeons.

The impact and relevance of techniques and fluids on lung injury in machine perfusion of lungs

Primary graft dysfunction (PGD) is a common complication after lung transplantation. A plethora of contributing factors are known and assessment of donor lung function prior to organ retrieval is mandatory for determination of lung quality. Specialized centers increasingly perform ex vivo lung perfusion (EVLP) to further assess lung functionality and improve and extend lung preservation with the aim to increase lung utilization. EVLP can be performed following different protocols. The impact of the individual EVLP parameters on PGD development, organ function and postoperative outcome remains to be fully investigated. The variables relate to the engineering and function of the respective perfusion devices, such as the type of pump used, functional, like ventilation modes or physiological (e.g. perfusion solutions). This review reflects on the individual technical and fluid components relevant to EVLP and their respective impact on inflammatory response and outcome. We discuss key components of EVLP protocols and options for further improvement of EVLP in regard to PGD. This review offers an overview of available options for centers establishing an EVLP program and for researchers looking for ways to adapt existing protocols.

Intermittent Ex Vivo Lung Perfusion in a Porcine Model for Prolonged Lung Preservation

BACKGROUND

Ex vivo lung perfusion expands the lung transplant donor pool and extends preservation time beyond cold static preservation. We hypothesized that repeated regular ex vivo lung perfusion would better maintain lung grafts.

METHODS

Ten pig lungs were randomized into 2 groups. The control underwent 16 h of cold ischemic time and 2 h of cellular ex vivo lung perfusion. The intermittent ex vivo lung perfusion group underwent cold ischemic time for 4 h, ex vivo lung perfusion (first) for 2 h, cold ischemic time for 10 h, and 2 h of ex vivo lung perfusion (second). Lungs were assessed, and transplant suitability was determined after 2 h of ex vivo lung perfusion.

RESULTS

The second ex vivo lung perfusion was significantly associated with better oxygenation, limited extravascular water, higher adenosine triphosphate, reduced intraalveolar edema, and well-preserved mitochondria compared with the control, despite proinflammatory cytokine elevation. No significant difference was observed in the first and second perfusion regarding oxygenation and adenosine triphosphate, whereas the second was associated with lower dynamic compliance and higher extravascular lung water than the first. Transplant suitability was 100% for the first and 60% for the second ex vivo lung perfusion, and 0% for the control.

CONCLUSIONS

The second ex vivo lung perfusion had a slight deterioration in graft function compared to the first. Intermittent ex vivo lung perfusion created a better condition for lung grafts than cold static preservation, despite cytokine elevation. These results suggested that intermittent ex vivo lung perfusion may help prolong lung preservation.

Normothermic Machine Perfusion Systems: Where Do We Go From Here?

Normothermic machine perfusion (NMP) aims to preserve organs ex vivo by simulating physiological conditions such as body temperature. Recent advancements in NMP system design have prompted the development of clinically effective devices for liver, heart, lung, and kidney transplantation that preserve organs for several hours/up to 1 d. In preclinical studies, adjustments to circuit structure, perfusate composition, and automatic supervision have extended perfusion times up to 1 wk of preservation. Emerging NMP platforms for ex vivo preservation of the pancreas, intestine, uterus, ovary, and vascularized composite allografts represent exciting prospects. Thus, NMP may become a valuable tool in transplantation and provide significant advantages to biomedical research. This review recaps recent NMP research, including discussions of devices in clinical trials, innovative preclinical systems for extended preservation, and platforms developed for other organs. We will also discuss NMP strategies using a global approach while focusing on technical specifications and preservation times.

Crystal ribcage: a platform for probing real-time lung function at cellular resolution

Understanding the dynamic pathogenesis and treatment response in pulmonary diseases requires probing the lung at cellular resolution in real time. Despite advances in intravital imaging, optical imaging of the lung during active respiration and circulation has remained challenging. Here, we introduce the crystal ribcage: a transparent ribcage that allows multiscale optical imaging of the functioning lung from whole-organ to single-cell level. It enables the modulation of lung biophysics and immunity through intravascular, intrapulmonary, intraparenchymal and optogenetic interventions, and it preserves the three-dimensional architecture, air-liquid interface, cellular diversity and respiratory-circulatory functions of the lung. Utilizing these capabilities on murine models of pulmonary pathologies we probed remodeling of respiratory-circulatory functions at the single-alveolus and capillary levels during disease progression. The crystal ribcage and its broad applications presented here will facilitate further studies of nearly any pulmonary disease as well as lead to the identification of new targets for treatment strategies.

Pushing the boundaries of innovation: the potential of ex vivo organ perfusion from an interdisciplinary point of view

Ex vivo machine perfusion (EVMP) is an emerging technique for preserving explanted solid organs with primary application in allogeneic organ transplantation. EVMP has been established as an alternative to the standard of care static-cold preservation, allowing for prolonged preservation and real-time monitoring of organ quality while reducing/preventing ischemia-reperfusion injury. Moreover, it has paved the way to involve expanded criteria donors, e.g., after circulatory death, thus expanding the donor organ pool. Ongoing improvements in EVMP protocols, especially expanding the duration of preservation, paved the way for its broader application, in particular for reconditioning and modification of diseased organs and tumor and infection therapies and regenerative approaches. Moreover, implementing EVMP for in vivo-like preclinical studies improving disease modeling raises significant interest, while providing an ideal interface for bioengineering and genetic manipulation. These approaches can be applied not only in an allogeneic and xenogeneic transplant setting but also in an autologous setting, where patients can be on temporary organ support while the diseased organs are treated ex vivo, followed by reimplantation of the cured organ. This review provides a comprehensive overview of the differences and similarities in abdominal (kidney and liver) and thoracic (lung and heart) EVMP, focusing on the organ-specific components and preservation techniques, specifically on the composition of perfusion solutions and their supplements and perfusion temperatures and flow conditions. Novel treatment opportunities beyond organ transplantation and limitations of abdominal and thoracic EVMP are delineated to identify complementary interdisciplinary approaches for the application and development of this technique.

Expanding Donor Options for Lung Transplant: Extended Criteria, Donation After Circulatory Death, ABO Incompatibility, and Evolution of Ex Vivo Lung Perfusion

Only using brain-dead donors with standard criteria, the existing donor shortage has never improved in lung transplantation. Currently, clinical efforts have sought the means to use cohorts of untapped donors, such as extended criteria donors, donation after circulatory death, and donors that are ABO blood group incompatible, and establish the evidence for their potential contribution to the lung transplant needs. Also, technical maturation for using those lungs may eliminate immediate concerns about the early posttransplant course, such as primary graft dysfunction or hyperacute rejection. In addition, recent clinical and preclinical advances in ex vivo lung perfusion techniques have allowed the safer use of lungs from high-risk donors and graft modification to match grafts to recipients and may improve posttransplant outcomes. This review summarizes recent trends and accomplishments and future applications for expanding the donor pool in lung transplantation.

Immune characterization of a xenogeneic human lung cross-circulation support system

Improved approaches to expanding the pool of donor lungs suitable for transplantation are critically needed for the growing population with end-stage lung disease. Cross-circulation (XC) of whole blood between swine and explanted human lungs has previously been reported to enable the extracorporeal recovery of donor lungs that declined for transplantation due to acute, reversible injuries. However, immunologic interactions of this xenogeneic platform have not been characterized, thus limiting potential translational applications. Using flow cytometry and immunohistochemistry, we demonstrate that porcine immune cell and immunoglobulin infiltration occurs in this xenogeneic XC system, in the context of calcineurin-based immunosuppression and complement depletion. Despite this, xenogeneic XC supported the viability, tissue integrity, and physiologic improvement of human donor lungs over 24 hours of xeno-support. These findings provide targets for future immunomodulatory strategies to minimize immunologic interactions on this organ support biotechnology.

L-alanyl-L-glutamine modified perfusate improves human lung cell functions and extend porcine ex vivo lung perfusion

BACKGROUND

The clinical application of normothermic ex vivo lung perfusion (EVLP) has increased donor lung utilization for transplantation through functional assessment. To develop it as a platform for donor lung repair, reconditioning and regeneration, the perfusate should be modified to support the lung during extended EVLP.

METHODS

Human lung epithelial cells and pulmonary microvascular endothelial cells were cultured, and the effects of Steen solution (commonly used EVLP perfusate) on basic cellular function were tested. Steen solution was modified based on screening tests in cell culture, and further tested with an EVLP cell culture model, on apoptosis, GSH, HSP70, and IL-8 expression. Finally, a modified formula was tested on porcine EVLP. Physiological parameters of lung function, histology of lung tissue, and amino acid concentrations in EVLP perfusate were measured.

RESULTS

Steen solution reduced cell confluence, induced apoptosis, and inhibited cell migration, compared to regular cell culture media. Adding L-alanyl-L-glutamine to Steen solution improved cell migration and decreased apoptosis. It also reduced cold preservation and warm perfusion-induced apoptosis, enhanced GSH and HSP70 production, and inhibited IL-8 expression on an EVLP cell culture model. L-alanyl-L-glutamine modified Steen solution supported porcine lungs on EVLP with significantly improved lung function, well-preserved histological structure, and significantly higher levels of multiple amino acids in EVLP perfusate.

CONCLUSIONS

Adding L-alanyl-L-glutamine to perfusate may provide additional energy support, antioxidant, and cytoprotective effects to lung tissue. The pipeline developed herein, with cell culture, cell EVLP, and porcine EVLP models, can be used to further optimize perfusates to improve EVLP outcomes.

Decreasing blood wastage during ex vivo lung perfusion recovery through utilization of thermal control technology

BACKGROUND

The Organ Care System (OCS) is a revolutionary ex vivo organ perfusion technology that can potentially expand the organ retrieval range. The OCS Lung device uses packed red blood cells (pRBC) with a proprietary solution. We report the ability to reduce blood waste during this procedure by using a thermal packaging solution in conjunction with the OCS platform.

METHODS

We retrospectively reviewed all OCS Lung recoveries performed by our recovery team, using pRBCfrom May 2019 to January 2021. Initially, units were stored using passive refrigeration with the Performance cooler at a temperature range of 1-6°C for 4 h. Subsequently, thermal control technology with the ProMed cooler was utilized to maintain the same temperature range for 72 h.

RESULTS

Twenty-three recoveries were initiated with 63 pRBC. The Performance cooler was used for 8, while the ProMed cooler for 13. 37.5% of pRBC transported with the Performance cooler was used within the validated time range, while 25.0% were used beyond the validated time range based on clinical judgment. In addition, 37.5% of pRBC transported with the Performance cooler were returned to the institution after canceled recoveries with an estimated loss of $1800; the ProMed cooler had no wastage.

CONCLUSIONS

This study showed that using an advanced thermal packaging solution facilitates proper storage of pRBC and represents an advancement for extended donor lung preservation. The elimination of blood wastage in this initial study portends ongoing benefits for the limited blood supply and reduced cost.

Devices for donor lung preservation

INTRODUCTION

Lung transplantation is the gold standard for the treatment of end stage lung disease but is limited by donor availability. Recently, the donor pool has seen significant expansion with liberalization of donor criteria. However, extended criteria donors can require additional time to prepare for implantation, necessitating additional preservation time of donor lungs.

AREAS COVERED

We present a review of current lung transplant storage strategies including new methodologies and technological advancements. The current standard, static cold storage, is a simple and cost-effective method of preserving grafts, but offers little flexibility with limited ability to mitigate ischemic-reperfusion injury, inflammation, and hypothermic tissue damage. Novel ex vivo lung perfusion (EVLP) devices, TransMedics OCS and XVIVO perfusion systems, extend preservation time by perfusing, and ventilating donor lungs while simultaneously allowing for evaluation of lung viability. Perfusate, preservation solutions, additives, temperature regulation, and assessment of organ damage are all critical components when evaluating the success and outcomes of these devices.

EXPERT OPINION

EVLP devices are more costly and often require additional resources and personnel support compared to static cold storage, but may provide the opportunity to extend preservation time, perform functional assessment, mitigate ischemic injury, and optimize extended criteria donors.

Successful 3-day lung preservation using a cyclic normothermic ex vivo lung perfusion strategy

Background

Methods

Findings

Interpretation

Funding

Trends in marginal lung allograft survival: advanced-age donors improve

INTRODUCTION

Although lung demand continues to outpace supply, 75% of potential donor lungs are discarded without being transplanted in the United States. To identify the discarded cohorts best suited to alleviate the lung shortage and reduce waitlist mortality, we explored changes in survival over time for five marginal donor definitions: age >60 years, smoking history >20 pack-years, PaO2/FiO2 <300mmHg, purulent bronchoscopic secretions, and chest radiograph infiltrates.

METHODS

Our retrospective cohort study separated 27,803 lung recipients in the UNOS Database into three 5-year eras by transplant date: 2005-2009, 2010-2014, and 2015-2019. Multivariable Cox proportional hazards regression and Kaplan-Meier analysis with log-rank test were used to compare survival across the eras.

RESULTS

Three definitions-low PaO 2/FiO 2, purulent bronchoscopic secretions, and abnormal chest radiographs-did not bear out as truly marginal, demonstrating lack of significantly elevated risk. Advanced donor age demonstrated considerable survival improvement (HR (95% CI): 1.47 (1.26-1.72) in 2005-2009 down to 1.14 (0.97-1.35) for 2015-2019), with protective factors being recipients <60 years, moderate recipient BMI, and low Lung Allocation Score. Donors with smoking history failed to demonstrate any significant improvement (HR (95% CI): 1.09 (1.01-1.17) in 2005-2009 increasing to 1.22 (1.08-1.38) in 2015-2019).

CONCLUSIONS

Advanced donor age, previously the most significant risk factor, has improved to near- benchmark levels, demonstrating the possibility for matching older donors to healthier non-elderly recipients in selected circumstances. Low PaO 2/FiO 2, bronchoscopic secretions, and abnormal radiographs demonstrated survival on par with standard donors. Significant donor smoking history, a moderate risk factor, has failed to improve. This article is protected by copyright. All rights reserved.

Experimental Models of Ischemic Lung Damage for the Study of Therapeutic Reconditioning During Ex Vivo Lung Perfusion

Background.

Ex vivo lung perfusion (EVLP) may allow therapeutic reconditioning of damaged lung grafts before transplantation. This study aimed to develop relevant rat models of lung damage to study EVLP therapeutic reconditioning for possible translational applications.

Methods.

Lungs from 31 rats were exposed to cold ischemia (CI) or warm ischemia (WI), inflated at various oxygen fractions (FiO₂), followed by 3 h EVLP. Five groups were studied as follow: (1) C21 (control): 3 h CI (FiO₂ 0.21); (2) C50: 3 h CI (FiO₂ 0.5); (3) W21: 1 h WI, followed by 2 h CI (FiO₂ 0.21); (4) W50: 1 h WI, followed by 2 h CI (FiO₂ 0.5); and (5) W2h: 2 h WI, followed by 1 h CI (FiO₂ 0.21). Following 3 h EVLP, we measured static pulmonary compliance (SPC), pulmonary vascular resistance, lung weight gain (edema), oxygenation capacity (differential partial pressure of oxygen), and protein carbonyls in lung tissue (oxidative stress), as well as lactate dehydrogenase (LDH, lung injury), nitrotyrosine (nitro-oxidative stress), interleukin-6 (IL-6, inflammation), and proteins (permeability edema) in bronchoalveolar lavage (BAL). Perivascular edema was quantified by histology.

Results.

No significant alterations were noted in C21 and C50 groups. W21 and W50 groups had reduced SPC and disclosed increased weight gain, BAL proteins, nitrotyrosine, and LDH. These changes were more severe in the W50 group, which also displayed greater oxidative stress. In contrast, both W21 and W50 showed comparable perivascular edema and BAL IL-6. In comparison with the other WI groups, W2h showed major weight gain, perivascular edema, SPC reduction, drop of differential partial pressure of oxygen, and massive increases of BAL LDH and proteins but comparable increase of IL-6 and biomarkers of oxidative stress.

Conclusions.

These models of lung damage of increasing severity might be helpful to evaluate new strategies for EVLP therapeutic reconditioning. A model combining 1 h WI and inflation at FiO₂ of 0.5 seems best suited for this purpose by reproducing major alterations of clinical lung ischemia-reperfusion injury.

Taking a Deep Breath: an Examination of Current Controversies in Surgical Procedures in Lung Transplantation

Purpose of Review

This article reviews controversial questions within the field of lung transplantation, with a focus on data generated within the last 3 years. We aim to summarize differing opinions on a selection of topics, including bridge-to-transplantation, intraoperative machine circulatory support, bronchial anastomosis, size mismatch, delayed chest closure, and ex vivo lung perfusion.

Recent Findings

With the growing rate of lung transplantations worldwide and increasing numbers of patients placed on waiting lists, the importance of determining best practices has only increased in recent years. Factors which promote successful outcomes have been identified across all the topics, with certain approaches promoted, such as ambulation in bridge-to-transplant and widespread intraoperative ECMO as machine support.

Summary

While great strides have been made in the operative procedures involved in lung transplantation, there are still key questions to be answered. The consensus which can be reached will be instrumental in further improving outcomes in recipients.

Custodiol-MP for ex vivo lung perfusion - A comparison in a porcine model of donation after circulatory determination of death

INTRODUCTION

Ex vivo lung perfusion (EVLP) is an established technique to evaluate and eventually recondition lungs prior to transplantation. Custodiol-MP (C-MP) solution is a new solution, designed for clinical machine perfusion, that has been used for kidneys. The aim of this study was to compare the effects of EVLP with Custodiol-MP on lung functional outcomes to the gold standard of EVLP with Steen Solution™.

MATERIAL AND METHODS

In a porcine EVLP model of DCDD (Donation after Circulatory Determination of Death), lungs were perfused with Steen Solution™ (SS, n = 7) or Custodiol-MP solution supplemented with 55 g/l albumin (C-MP, n = 8). Lungs were stored cold for 4 h in low potassium dextran solution and subsequently perfused ex vivo for 4 h. During EVLP pulmonary gas exchange, activities of lactate dehydrogenase (LDH) and alkaline phosphatase (AP) as well as levels of lactate in the perfusate were recorded hourly.

RESULTS

Oxygenation capacity differed significantly between groups (averaged over 4 h: SS 274 ± 178 mmHg; C-MP 284 ± 151 mmHg p = 0.025). Lactate dehydrogenase activities and lactate concentrations were significantly lower in Custodiol-MP perfused lungs.In a porcine model of DCDD with 4 h of EVLP the use of modified Custodiol-MP as perfusion solution was feasible. The use of C-MP showed at least comparable lung functional outcomes to the use of Steen SolutionTM. Furthermore C-MP perfusion resulted in significantly lower lactate dehydrogenase activity and lactate levels in the perfusate and higher oxygenation capacity.

Overcoming the Limits of Reconditioning: Seventeen Hours of EVLP With Successful Transplantation From Uncontrolled Circulatory Death Donor

BACKGROUND

Uncontrolled donation after circulatory death (DCD) donors are an extraordinary resource to increase the number of lungs available for transplantation. However, the risk of the warm ischemia resulting from cardiac arrest to irreversibly damage the organs is considerable. Moreover, graft preservation issues and organizational problems often worsen the dangerous effects of warm ischemia. Ex vivo lung perfusion (EVLP) enables us to evaluate and recondition lungs whose functionality is doubtful, as well as to overcome the difficulties related to time and logistics.

METHODS

We report the case of uncontrolled DCD lungs successfully treated with an exceptionally prolonged EVLP. Because the donor's blood count and liver biopsy showed signs of possible leukemia, EVLP was protracted up to 17 h while waiting for immunohistochemical analyses to rule out this diagnosis; eventually, the results came back negative, and the lungs were judged suitable for transplantation.

RESULTS

The recipient was a 32-y-old male individual with cystic fibrosis, colonized by Pandoraea pnomenusa. Bilateral transplantation required central extracorporeal membrane oxygenation. The patient was extubated after 36 h and was discharged 21 d after the operation. Despite early recolonization by Pandoraea pnomenusa and airway complications requiring pneumatic dilatation, he is alive and has a satisfactory respiratory function 15 mo after transplantation.

CONCLUSIONS

Uncontrolled DCD represents a challenge due to both logistical issues and the complexity of graft evaluation before procurement. EVLP with cellular perfusate could be a valuable tool to overcome these limits. Nonetheless, caution should be exercised when interpreting the effects of this technique on airway healing.

Ex Vivo Lung Perfusion: Current Achievements and Future Directions

There is a severe shortage in the availability of donor organs for lung transplantation. Novel strategies are needed to optimize usage of available organs to address the growing global needs. Ex vivo lung perfusion has emerged as a powerful tool for the assessment, rehabilitation, and optimization of donor lungs before transplantation. In this review, we discuss the history of ex vivo lung perfusion, current evidence on its use for standard and extended criteria donors, and consider the exciting future opportunities that this technology provides for lung transplantation.

Prolonged (≥24 Hours) Normothermic (≥32 °C) Ex Vivo Organ Perfusion: Lessons From the Literature

For 2 centuries, researchers have studied ex vivo perfusion intending to preserve the physiologic function of isolated organs. If it were indeed possible to maintain ex vivo organ viability for days, transplantation could become an elective operation with clinicians methodically surveilling and reconditioning allografts before surgery. To this day, experimental reports of successfully prolonged (≥24 hours) organ perfusion are rare and have not translated into clinical practice. To identify the crucial factors necessary for successful perfusion, this review summarizes the history of prolonged normothermic ex vivo organ perfusion. By examining successful techniques and protocols used, this review outlines the essential elements of successful perfusion, limitations of current perfusion systems, and areas where further research in preservation science is required.

A Low-Cost Perfusate Alternative for Ex Vivo Lung Perfusion

BACKGROUND

Normothermic ex vivo lung perfusion (EVLP) has been used successfully to evaluate and recondition marginal donor lungs; however, multiple barriers continue to prevent its widespread adoption. We sought to develop a common hospital ingredient-derived perfusate (CHIP) with equivalent functional and inflammatory characteristics to a standard Krebs-Henseleit buffer with 8% serum albumin-derived perfusate (KHB-Alb) to improve access and reduce costs of ex vivo organ perfusion.

METHODS

Sixteen porcine lungs were perfused using negative pressure ventilation (NPV) EVLP for 12 hours in a normothermic state and were allocated equally to 2 groups: KHB-Alb vs CHIP. Physiological parameters, cytokine profiles, and edema formation were compared between treatment groups.

RESULTS

Perfused lungs in both groups demonstrated equivalent oxygenation (partial pressure of arterial oxygen/fraction of inspired oxygen ratio >350 mm Hg) and physiological parameters. There was equivalent generation of tumor necrosis factor-α and IL-6, irrespective of perfusate solution used, when comparing CHIP vs KHB-Alb. Pig lungs developed equivalent edema formation between groups (CHIP: 15.8 ± 4.8%, KHB-Alb 19.5 ± 4.4%, P > .05).

CONCLUSION

A perfusate derived of common hospital ingredients provides equivalent results to a standard Krebs-Henseleit buffer with 8% serum albumin-based perfusate in NPV-EVLP.

Xenogeneic cross-circulation for extracorporeal recovery of injured human lungs

Patients awaiting lung transplantation face high wait-list mortality, as injury precludes the use of most donor lungs. Although ex vivo lung perfusion (EVLP) is able to recover marginal quality donor lungs, extension of normothermic support beyond 6 h has been challenging. Here we demonstrate that acutely injured human lungs declined for transplantation, including a lung that failed to recover on EVLP, can be recovered by cross-circulation of whole blood between explanted human lungs and a Yorkshire swine. This xenogeneic platform provided explanted human lungs a supportive, physiologic milieu and systemic regulation that resulted in functional and histological recovery after 24 h of normothermic support. Our findings suggest that cross-circulation can serve as a complementary approach to clinical EVLP to recover injured donor lungs that could not otherwise be utilized for transplantation, as well as a translational research platform for immunomodulation and advanced organ bioengineering.

Leukoreduction in ex vivo perfusion circuits: comparison of leukocyte depletion efficiency with leukocyte filters

BACKGROUND

Leukodepletion of whole blood-based perfusates remains a challenge in experimental models of ex vivo perfusion. This study investigated the leukoreduction efficacy of the commonly used LeukoGuard LG Arterial and BC2 Cardioplegia filters.

METHODS

Eleven liters of washed porcine blood was used to evaluate the filtration efficiency of LG (n = 6) and BC2 (n = 5) filters. Filter efficacy was tested by passing 1 L of washed blood through each filter. Complete blood count was performed to detect a reduction of white blood cells, red blood cells, and hemoglobin concentration.

RESULTS

The BC2 Cardioplegia filter showed a significant reduction in white blood cell count (13.16 ± 4.2 × 10³ cells/μL pre-filtration, 0.62 ± 0.61 cells/μL post-filtration, p = 0.005), red blood cell count (9.18 ± 0.16 × 10⁶ cells/μL pre-filtration, 9.02 ± 0.16 × 10⁶ cells/μL post-filtration, p = 0.012) and hemoglobin concentration (15.89 ± 0.66 g/dL pre-filtration, 15.67 ± 0.83 g/dL post-filtration, p = 0.017). Platelet reduction in the LG filter group was statistically significant (13.23 ± 13.98 × 10³ cells/μL pre-filtration, 7.15 ± 3.31 × 10³ cells/μL post-filtration, p = 0.029), but no difference was seen in the BC2 group. There was no significant difference in white blood cell count in the LG filter group (10.12 ± 3.0 × 10³ cells/μL pre-filtration, 10.32 ± 2.44 × 10³ cells/μL post-filtration, p = 0.861).

CONCLUSION

Our results suggest that the LG filter should not be used in ex vivo perfusion circuits for the purpose of leukodepletion. The BC2 filter can be used in EVP circuits with flow rates of less than 350 mL/min. Alternatively, perfusate may be leukodepleted before perfusion.

Perfusate adsorption during ex vivo lung perfusion improves early post-transplant lung function

OBJECTIVE

Improvement in ex vivo lung perfusion protocols could increase the number of donors available for transplantation and protect the lungs from primary graft dysfunction. We hypothesize that perfusate adsorption during ex vivo lung perfusion reconditions the allograft to ischemia-reperfusion injury after lung transplantation.

METHODS

Donor pig lungs were preserved for 24 hours at 4°C, followed by 6 hours of ex vivo lung perfusion according to the Toronto protocol. The perfusate was additionally adsorbed through a CytoSorb adsorber (CytoSorbents, Berlin, Germany) in the treatment group, whereas control lungs were perfused according to the standard protocol (n = 5, each). Ex vivo lung perfusion physiology and biochemistry were monitored. Upon completion of ex vivo lung perfusion, a left single lung transplantation was performed. Oxygenation function and lung mechanics were assessed during a 4-hour reperfusion period. The inflammatory response was determined during ex vivo lung perfusion and reperfusion.

RESULTS

The cytokine concentrations in the perfusate were markedly lower with the adsorber, resulting in improved ex vivo lung perfusion physiology and biochemistry during the 6-hour perfusion period. Post-transplant dynamic lung compliance was markedly better during the 4-hour reperfusion period in the treatment group. Isolated allograft oxygenation function and dynamic compliance continued to be superior in the adsorber group at the end of reperfusion, accompanied by a markedly decreased local inflammatory response.

CONCLUSIONS

Implementation of an additional cytokine adsorber has refined the standard ex vivo lung perfusion protocol. Furthermore, cytokine removal during ex vivo lung perfusion improved immediate post-transplant graft function together with a less intense inflammatory response to reperfusion in pigs. Further studies are warranted to understand the beneficial effects of perfusate adsorption during ex vivo lung perfusion in the clinical setting.

Use of modified Custodiol-N as perfusion solution in ex vivo lung perfusion

OBJECTIVES

Ex vivo Lung Perfusion (EVLP) is a promising tool to increase the donor pool for lung transplantation. Custodiol-N solution was originally designed for organ preservation during cold static preservation (CSP) and was successfully used for machine perfusion in kidneys. It was the aim of this study to compare the lung functional outcomes after 4 hours of EVLP using modified Custodiol-N or STEEN Solution^TM as perfusion solution.

METHODS

In a porcine DCD model, lungs were perfused either with STEEN Solution^TM (Standard SS, n=8) or modified Custodiol-N with added 1.1 g/l glucose monohydrate and 50 g/l dextran 40 (CD, n=8). For a third group 7 g/l albumin was supplemented to modified Custodiol-N (CDA, n=8). During four hours of EVLP pulmonary gas exchange and activities of lactate dehydrogenase (LDH) and alkaline phosphatase (AP) in perfusate were recorded.

RESULTS

Lungs that underwent EVLP with modified Custodiol-N showed significantly higher oxygen capacity (ΔpO₂ averaged over four hours of EVLP: SS: 236.28 ± 47.26 mmHg, CD: 402.79 ± 30.33 mmHg, CDA: 414.86 ± 9.77 mmHg) than lungs perfused with STEEN Solution^TM. The addition of albumin did not have a significant effect on lung function but these lungs showed lower wet/dry ratio.

CONCLUSION

In a porcine DCD model of 9 hours CSP followed by four hours of EVLP the use of modified Custodiol-N as perfusion solution was feasible and associated with higher oxygen capacity than STEEN Solution^TM. The addition of albumin seems to further stabilize lung function.

Effects of immediate versus delayed ex-vivo lung perfusion in a porcine cardiac arrest donation model

OBJECTIVE

Ex-vivo lung perfusion is a promising tool to evaluate and recondition marginal donor lungs usually after a cold static preservation. The concept of continuous organ perfusion is supposed to reduce ischemic damage; however, the optimal perfusion protocol has not been established yet. The aim of this study was to compare immediate ex-vivo lung perfusion (I-EVLP) to delayed ex-vivo lung perfusion (D-EVLP) after a certain cold static preservation period on lung function in a large animal model.

METHODS

In a porcine model, lungs were procured after circulatory death and 60 min of no-touch warm ischemia. Lungs were preserved with single-flush cold low potassium dextran solution and prepared either for I-EVLP (n = 8) or stored cold for 9 h with subsequent D-EVLP (n = 8). Functional outcomes and morphology were compared during 4 h of ex-vivo lung perfusion, using STEEN Solution^TM as perfusion solution.

RESULTS

Pulmonary functional data, perfusate activities of lactate dehydrogenase, alkaline phosphatase, and products of lipid peroxidation did not differ significantly. There was a trend toward lower wet-dry ratio (I-EVLP: 13.4 ± 2.9; D-EVLP: 9.1 ± 2.5) and higher ΔpO₂ in D-EVLP group (I-EVLP: 209 ± 51.6 mmHg; D-EVLP: 236.3 ± 47.3 mmHg).

CONCLUSION

In this donation-after-circulatory-death model, 9 h of cold static preservation followed by ex-vivo lung perfusion results in comparable pulmonary function to I-EVLP as indicated by oxygenation capacities and wet-dry ratio. Our findings indicate that prolonged cold static preservation prior to ex-vivo lung perfusion is as safe and effective as I-EVLP in the procurement of donor lungs.

Breathing lung transplantation with the Organ Care System (OCS) Lung: lessons learned and future implications

Ex vivo lung perfusion (EVLP) represents a potentially important advancement in the preservation of donor lungs prior to transplantation. Portable EVLP or "Breathing Lung Transplantation" with the Organ Care System (OCS) Lung combines the fundamental components of EVLP with portability, thus reducing the total ischemic burden. The Food and Drug Administration (FDA) approved OCS for perfusion of standard donor lungs prior to transplant in 2018. The current review discusses the available literature on the clinical outcomes of OCS Lung as well as translational data.

Continuous Hemodialysis Does Not Improve Graft Function During Ex Vivo Lung Perfusion Over 24 Hours

BACKGROUND

Extended periods of ex vivo lung perfusion (EVLP) lead to several inadvertent consequences including accumulation of lactate and increasing electrolyte concentrations in the perfusate. We sought to determine whether continuous hemodialysis (CHD) of the perfusate would be a suitable modality for improving ionic homeostasis in extended EVLP without compromising functional outcomes.

METHODS

Twelve porcine lungs were perfused using EVLP for 24 hours. All lungs were ventilated with negative pressure ventilation. Lungs in the treatment group (n = 6) underwent continuous hemodialysis of the perfusate. Functional parameters, edema formation, and histopathologic analysis were used to assess graft function. Electrolyte and lactate profiles were also followed to assess the efficiency of hemodialysis.

RESULTS

Lungs in both treatment and control groups demonstrated stable and acceptable oxygenation to 24 hours. Lungs demonstrated a decrease in compliance over time. There was no difference in oxygenation and compliance between groups. CHD-EVLP lungs had higher pulmonary vascular resistance and pulmonary artery pressures. Despite increased perfusion pressures, weight gain at both 11 and 23 hours was not different between groups. Perfusate sodium and lactate concentrations were significantly lower in the CHD-EVLP group.

CONCLUSION

The addition of continuous hemodialysis to EVLP did not improve graft function up to 24 hours despite improved maintenance of perfusate composition.

Emerging technologies in organ preservation, tissue engineering and regenerative medicine: a blessing or curse for transplantation?

Since the beginning of transplant medicine in the 1950s, advances in surgical technique and immunosuppressive therapy have created the success story of modern organ transplantation. However, today more than ever, we are facing a huge discrepancy between organ supply and demand, limiting the potential for transplantation to save and improve the lives of millions. To address the current limitations and shortcomings, a variety of emerging new technologies focusing on either maximizing the availability of organs or on generating new organs and organ sources hold great potential to eventully overcoming these hurdles. These advances are mainly in the field of regenerative medicine and tissue engineering. This review gives an overview of this emerging field and its multiple sub-disciplines and highlights recent advances and existing limitations for widespread clinical application and potential impact on the future of transplantation.