ECMO as Bridge to Lung Transplant

Diaphragm and Lung Transplantation

Mutual interactions between the diaphragm and lung transplantation (LTx) are known to exist. Before LTx, many factors can exert notable impact on the diaphragmatic function, such as the underlying respiratory disease, the comorbidities, and the chronic treatments of the patient. In the post-LTx setting, even the surgical procedure itself can cause a stressful trauma to the diaphragm, potentially leading to morphological and functional alterations. Conversely, the diaphragm can significantly influence various aspects of the LTx process, ranging from graft-to-chest cavity size matching to the long-term postoperative respiratory performance of the recipient. Despite this, there are still no standard criteria for evaluating, defining, and managing diaphragmatic dysfunction in the context of LTx to date. This deficiency hampers the accurate assessment of those factors which affect the diaphragm and its reciprocal influence on LTx outcomes. The objective of this narrative review is to delve into the complex role the diaphragm plays in the different stages of LTx and into the modifications of this muscle following surgery.

Outcomes of Lung Transplantation in Patients With Right Ventricular Dysfunction: A Single-Center Retrospective Analysis Comparing ECMO Configurations in a Bridge-to-Transplant Setting

This study aimed to assess the lung transplantation (LT) outcomes of patients with right ventricular dysfunction (RVD), focusing on the impact of various extracorporeal membrane oxygenation (ECMO) configurations. We included adult patients who underwent LT with ECMO as a bridge-to-transplant from 2011 to 2021 at a single center. Among patients with RVD (n = 67), veno-venous (V-V) ECMO was initially applied in 79% (53/67) and maintained until LT in 52% (35/67). Due to the worsening of RVD, the configuration was changed from V-V ECMO to veno-arterial (V-A) ECMO or a right ventricular assist device with an oxygenator (Oxy-RVAD) in 34% (18/67). They showed that lactic acid levels (2-6.1 mmol/L) and vasoactive inotropic score (6.6-22.6) increased. V-A ECMO or Oxy-RVAD was initiated and maintained until LT in 21% (14/67) of cases. There was no significant difference in the survival rates among the three configuration groups (V-V ECMO vs. configuration changed vs. V-A ECMO/Oxy-RVAD). Our findings suggest that the choice of ECMO configuration for LT candidates with RVD should be determined by the patient's current hemodynamic status. Vital sign stability supports the use of V-V ECMO, while increasing lactic acid levels and vasopressor needs may require a switch to V-A ECMO or Oxy-RVAD.

Outcomes of Recipients Aged 65 Years and Older Bridged to Lung Transplant With Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) as a bridge to lung transplant (BTT) has been used for critically ill candidates with excellent outcomes, but data on this strategy in older recipients remain limited. We compared outcomes of no BTT, mechanical ventilation (MV)-only BTT, and ECMO BTT in recipients of greater than or equal to 65 years. Lung-only recipients of greater than or equal to 65 years in the United Network for Organ Sharing database between 2008 and 2022 were included and stratified by bridging strategy. Of the 9,936 transplants included, 226 (2.3%) were MV-only BTT and 159 (1.6%) were ECMO BTT. Extracorporeal membrane oxygenation BTT recipients were more likely to have restrictive disease pathology, had higher median lung allocation score, and spent fewer days on the waitlist (all p < 0.001). Compared to no-BTT recipients, ECMO BTT recipients were more likely to be intubated or on ECMO at 72 hours posttransplant and had longer hospital lengths of stay (all p < 0.001). Extracorporeal membrane oxygenation BTT recipients had increased risk of 3 years mortality compared to both no-BTT (adjusted hazard ratio [aHR] = 1.48 [95% confidence interval {CI}: 1.14-1.91], p = 0.003) and MV-only recipients (aHR = 1.50 [95% CI: 1.08-2.07], p = 0.02). Overall, we found that ECMO BTT in older recipients is associated with inferior posttransplant outcomes compared to MV-only or no BTT, but over half of recipients remained alive at 3 years posttransplant.

Extracorporeal membrane oxygenation bridge to pediatric lung transplantation: Modern era analysis

BACKGROUND

Survival outcomes of children on extracorporeal membrane oxygenation (ECMO) at time of lung transplant (LTx) remain unclear.

METHODS

Pediatric first-time LTx recipients transplanted between January 2000 and December 2020 were identified in the United Network for Organ Sharing Registry to compare post-transplant survival according to ECMO support at time of transplant. For a comprehensive analysis of the data, univariate analysis, multivariable Cox regression, and propensity score matching were performed.

RESULTS

During the study period, 954 children under 18 years of age underwent LTx with 40 patients on ECMO. We did not identify a post-LTx survival difference between patients receiving ECMO when compared to those that did not. A multivariable Cox regression model (Hazard ratio = 0.83; 95% confidence interval: 0.47, 1.45; p = .51) did not demonstrate an increased risk for death post-LTx. Lastly, a propensity score matching analysis, retaining 33 ECMO and 33 non-ECMO patients, further confirmed no post-LTx survival difference comparing ECMO to no ECMO cohorts (Hazard ratio = 0.98; 95% confidence interval: 0.48, 2.00; p = .96).

CONCLUSIONS

In this contemporary cohort of children, the use of ECMO at the time of LTx did not negatively impact post-transplant survival.

Predictors associated with mortality of veno-venous extracorporeal membrane oxygenation therapy

BACKGROUND

The use of veno-venous extracorporeal membrane oxygenation (V-V ECMO) has rapidly increased in recent years. Today, applications of V-V ECMO include a variety of clinical conditions such as acute respiratory distress syndrome (ARDS), bridge to lung transplantation and primary graft dysfunction after lung transplantation. The purpose of the present study was to investigate in-hospital mortality of adult patients undergoing V-V ECMO therapy and to determine independent predictors associated with mortality.

METHODS

This retrospective study was conducted at the University Hospital Zurich, a designated ECMO center in Switzerland. Data was analyzed of all adult V-V ECMO cases from 2007 to 2019.

RESULTS

In total, 221 patients required V-V ECMO support (median age 50 years, 38.9% female). In-hospital mortality was 37.6% and did not statistically vary significantly between indications (P=0.61): 25.0% (1/4) for primary graft dysfunction after lung transplantation, 29.4% (5/17) for bridge to lung transplantation, 36.2% (50/138) for ARDS and 43.5% (27/62) for other pulmonary disease indications. Cubic spline interpolation showed no effect of time on mortality over the study period of 13 years. Multiple logistic regression modelling identified significant predictor variables associated with mortality: age [odds ratio (OR), 1.05; 95% confidence interval (CI): 1.02-1.07; P=0.001], newly detected liver failure (OR, 4.83; 95% CI: 1.27-20.3; P=0.02), red blood cell transfusion (OR, 1.91; 95% CI: 1.39-2.74; P<0.001) and platelet concentrate transfusion (OR, 1.93; 95% CI: 1.28-3.15; P=0.004).

CONCLUSIONS

In-hospital mortality of patients receiving V-V ECMO therapy remains relatively high. Patients' outcomes have not improved significantly in the observed period. We identified age, newly detected liver failure, red blood cell transfusion and platelet concentrate transfusion as independent predictors associated with in-hospital mortality. Incorporating such mortality predictors into decision making with regards to V-V ECMO use may increase its effectiveness and safety and may translate into better outcomes.

State of the art - Extracorporeal membrane oxygenation as a bridge to thoracic transplantation

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) has revolutionized the treatment of refractory cardiac and respiratory failure, and its use continues to increase, particularly in adults. However, ECMO-related morbidity and mortality remain high.

MAIN TEXT

In this review, we investigate and expand upon the current state of the art in thoracic transplant and extracorporeal life support (ELS). In particular, we examine recent increase in incidence of heart transplant in patients supported by ECMO; the potential changes in patient care and selection for transplant in the years prior to updated United Network for Organ Sharing (UNOS) organ allocation guidelines versus those in the years following, particularly where these guidelines pertain to ECMO; and the newly revived practice of heart-lung block transplants (HLT) and the prevalence and utility of ECMO support in patients listed for HLT.

CONCLUSIONS

Our findings highlight encouraging outcomes in patients bridged to transplant with ECMO, considerable changes in treatment surrounding the updated UNOS guidelines, and complex, diverse outcomes among different centers in their care for increasingly ill patients listed for thoracic transplant.

The American Association for Thoracic Surgery (AATS) 2022 Expert Consensus Document: The use of mechanical circulatory support in lung transplantation

OBJECTIVE

The use of mechanical circulatory support (MCS) in lung transplantation has been steadily increasing over the prior decade, with evolving strategies for incorporating support in the preoperative, intraoperative, and postoperative settings. There is significant practice variability in the use of these techniques, however, and relatively limited data to help establish institutional protocols. The objective of the AATS Clinical Practice Standards Committee (CPSC) expert panel was to review the existing literature and establish recommendations about the use of MCS before, during, and after lung transplantation.

METHODS

The AATS CPSC assembled an expert panel of 16 lung transplantation physicians who developed a consensus document of recommendations. The panel was broken into subgroups focused on preoperative, intraoperative, and postoperative support, and each subgroup performed a focused literature review. These subgroups formulated recommendation statements for each subtopic, which were evaluated by the entire group. The statements were then developed via discussion among the panel and refined until consensus was achieved on each statement.

RESULTS

The expert panel achieved consensus on 36 recommendations for how and when to use MCS in lung transplantation. These recommendations included the use of veno-venous extracorporeal membrane oxygenation (ECMO) as a bridging strategy in the preoperative setting, a preference for central veno-arterial ECMO over traditional cardiopulmonary bypass during the transplantation procedure, and the benefit of supporting selected patients with MCS postoperatively.

CONCLUSIONS

Achieving optimal results in lung transplantation requires the use of a wide range of strategies. MCS provides an important mechanism for helping these critically ill patients through the peritransplantation period. Despite the complex nature of the decision making process in the treatment of these patients, the expert panel was able to achieve consensus on 36 recommendations. These recommendations should provide guidance for professionals involved in the care of end-stage lung disease patients considered for transplantation.

Time From Infiltrate on Chest Radiograph to Venovenous Extracorporeal Membrane Oxygenation in COVID-19 Affects Mortality

Venovenous extracorporeal membrane oxygenation (VV ECMO) has been used to treat severe coronavirus disease 2019 (COVID-19) acute respiratory distress syndrome; however, patient selection criteria have evolved throughout the pandemic. In this study, we sought to determine the association of patient mortality with time from positive COVID-19 test and infiltrate on chest radiograph (x-ray) to VV ECMO cannulation. We hypothesized that an increasing duration between a positive COVID-19 test or infiltrates on chest x-ray and cannulation would be associated with increased mortality. This is a single-center retrospective chart review of COVID-19 VV ECMO patients from March 1, 2020 to July 28, 2021. Unadjusted and adjusted multivariate analyses were performed to assess for mortality differences. A total of 93 patients were included in our study. Increased time, in days, from infiltrate on chest x-ray to cannulation was associated with increased mortality in both unadjusted (5-9, P = 0.002) and adjusted regression analyses (odds ratio [OR]: 1.49, 95% CI: 1.22-1.81, P < 0.01). Time from positive test to cannulation was not found to be significant between survivors and nonsurvivors (7.5-11, P = 0.06). Time from infiltrate on chest x-ray to cannulation for VV ECMO should be considered when assessing patient candidacy. Further larger cohort and prospective studies are required.

Extracorporeal membrane oxygenation as a bridge to transplant in neonates with fatal pulmonary conditions: A review

Neonates with progressive respiratory failure should be referred early for subspecialty evaluation and lung transplantation consideration. ECMO should be considered for patients with severe cardiopulmonary dysfunction and a high likelihood of death while on maximal medical therapy, either in the setting of reversible medical conditions or while awaiting lung transplantation. While ECMO offers hope to neonates that experience clinical deterioration while awaiting transplant, the risks and benefits of this intervention should be considered on an individual basis. Owing to the small number of infant lung transplants performed yearly, large studies examining the outcomes of various bridging techniques in this age group do not exist. Multiple single-centre experiences of transplanted neonates have been described and currently serve as guidance for transplant teams. Future investigation of outcomes specific to neonatal transplant recipients bridged with advanced devices is needed.

Critical Care of the Lung Transplant Patient

Lung transplantation is a therapeutic option for end-stage lung disease that improves survival and quality of life. Prelung transplant admission to the intensive care unit (ICU) for bridge to transplant with mechanical ventilation and extracorporeal membrane oxygenation (ECMO) is common. Primary graft dysfunction is an important immediate complication of lung transplantation with short- and long-term morbidity and mortality. Later transplant-related causes of respiratory failure necessitating ICU admission include acute cellular rejection, atypical infections, and chronic lung allograft dysfunction. Lung transplantation for COVID-19-related ARDS is increasingly common..

Lung Transplantation for Patients with COVID-19 Acute Respiratory Distress Syndrome

Patients with severe coronavirus disease 2019 (COVID-19) acute respiratory distress syndrome (ARDS) may exhibit pulmonary fibrosis after the viral illness resolves. Some of these patients may experience severe functional lung impairment, and thus require transplants to prevent death or maintain a tolerable quality of life. Considering the reversibility of COVID-19 ARDS, lung transplant candidates are observed for 1–2 months and must be selected very carefully before transplantation. As the short-term outcomes of such patients are comparable to those of patients with other indications for transplantation, lung transplantation should be actively considered.

Improving hemocompatibility of artificial lungs by click conjugation of glycoengineered endothelial cells onto blood-contacting surfaces

Artificial lungs, also known as oxygenators, allow adequate oxygenation of the blood in patients with severe respiratory failure and enable patient survival. However, the insufficient hemocompatibility of the current of artificial lungs hampers their long-term use. Therefore, in this study, a novel strategy was developed to efficiently endothelialize blood-contacting surfaces to improve their hemocompatibility. Hollow fiber membranes (HFMs) were functionalized with dibenzylcyclooctyne (DBCO), and endothelial cells were glycoengineered for covalent conjugation to DBCO by a copper-free click reaction. Metabolic glycoengineering using azidoacetylmannosamine-tetraacylated (Ac₄ManNAz) resulted in highly efficient functionalization of endothelial cells with azide (N₃) molecules on the cell surface without negative impact on cell viability. After 48 h, significantly improved endothelialization was detected on the HFM surfaces functionalized with DBCO compared to unmodified HFMs. Endothelial cells were responsive to inflammatory stimulus and expressed adhesion-promoting molecules (E-selectin, VCAM-1, and ICAM-1). Furthermore, the hemocompatibility of HFMs was analyzed by dynamic incubation with fresh human blood. DBCO-coated and uncoated HFMs showed a comparable hemocompatibility, but the endothelialization of HFMs significantly reduced the activation of blood coagulation and platelets. Interestingly, the incubation of endothelialized HFMs with human blood further reduced the expression of E-selectin and VCAM-1 in endothelial cells. In this study, a highly efficient, cell-compatible method for endothelialization of artificial lungs was established. This click chemistry-based method can be also applied for the endothelialization of other artificial surfaces for tissue engineering and regenerative medicine applications.

Venoarterial Versus Venovenous Extracorporeal Membrane Oxygenation as Bridge to Lung Transplantation

BACKGROUND

Veno-venous (VV) extracorporeal membrane oxygenation (ECMO) has been used as a bridge to lung transplantation with acceptable outcomes. We hypothesized that VA ECMO, as part of a multidisciplinary ECMO program, yields similar outcomes as VV ECMO as a bridge in lung transplantation.

METHODS

Records of all patients who had undergone ECMO with the intention to bridge to lung transplantation at University of California Los Angeles from January 1, 2012 to March 31, 2020 were reviewed. Baseline characteristics, in-hospital outcomes, long-term survival, and freedom from bronchiolitis obliterans syndrome (BOS) were assessed.

RESULTS

During this interval, 58 patients were placed on ECMO with the intention to bridge to lung transplantation: 27 on VV ECMO, and 31 on VA ECMO with a median duration of 7 and 17 days of support, respectively(p=0.01). Successful bridge to lung transplantation occurred in 21(78%) VV and 26(84%) VA patients. Incidence of primary graft dysfunction III(PGD III) at 72 hours in the VV and the VA cohorts were 0% and 4%, respectively(p=0.99). In-hospital and 90-day survival of the VV and VA groups were 100% and 96%, respectively(p=0.99). Three-year survival of the two groups were not significantly different from a contemporary cohort of lung transplant recipients not bridged with ECMO.

CONCLUSIONS

VA and VV ECMO can both be used as a bridge to lung transplantation with high success, with short and medium-term survival similar to non-bridged lung transplant recipients. Both modes should be considered effective at bridging select candidates to lung transplantation.

Extracorporeal Membrane Oxygenation as a Bridge to Lung Transplant: Considerations for Critical Care Nursing Practice

TOPIC

Candidates waiting for lung transplant are sicker now than ever before. Extracorporeal membrane oxygenation has become useful as a bridge to lung transplant for these critically ill patients.

CLINICAL RELEVANCE

Critical care nurses must be prepared to care for the increasing number of lung transplant patients who require this advanced support method.

PURPOSE OF PAPER

To provide critical care nurses with the foundational knowledge essential for delivering quality care to this high-acuity transplant patient population.

CONTENT COVERED

This review describes the types of extracorporeal membrane oxygenation (venovenous and venoarterial), provides an overview of the indications and contraindications for extracorporeal membrane oxygenation, and discusses the role of clinical bedside nurses in the treatment of patients requiring extracorporeal membrane oxygenation as a bridge to lung transplant.

Extracorporeal Membrane Oxygenation as a Bridge to Lung Transplant

Extracorporeal membrane oxygenation (ECMO) is a cardiopulmonary technology capable of supporting cardiac and respiratory function in the presence of end-stage lung disease. Initial experiences using ECMO as a bridge to lung transplant (ECMO-BTLT) were characterized by high rates of ECMO-associated complications and poor posttransplant outcomes. More recently, ECMO-BTLT has garnered success in preserving patients' physiologic condition and candidacy prior to lung transplant due to technological advances and improved management. Despite recent growth, clinical practice surrounding use of ECMO-BTLT remains variable, with little data to inform optimal patient selection and management. Although many questions remain, the use of ECMO-BTLT has shown promising outcomes suggesting that ECMO-BTLT can be an effective strategy to ensure that complex and rapidly decompensating patients with end-stage lung disease can be safely transplanted with good outcomes. Further studies are needed to refine and inform practice patterns, management, and lung allocation in this high-risk and fragile patient population.

Lung Transplant from ECMO: Current Results and Predictors of Post-transplant Mortality

Purpose of Review

We examined data from the last 5 years describing extracorporeal life support (ECLS) as a bridge to lung transplantation. We assessed predictors of survival to transplantation and post-transplant mortality.

Recent Findings

The number of lung transplants performed worldwide is increasing. This is accompanied by an increase in the type of patients being transplanted, including sicker patients with more advanced disease. Consequently, there is an increase in the need for bridging strategies, with varying success. Several predictors of failure have been identified. Major risk factors include retransplantation, other organ dysfunction, and deconditioning.

Summary

ECLS is a risky strategy but necessary for patients who would otherwise die if not bridged to transplantation. The presence of predictors for failure is not a contraindication for bridging. However, major risk factors should be approached cautiously. Other, more minor risk factors may be considered acceptable. More importantly, the strategy should be individualized for each patient to achieve the best possible outcomes.

Extracorporeal Membrane Oxygenation for Respiratory Failure

This review focuses on the use of veno-venous extracorporeal membrane oxygenation for respiratory failure across all blood flow ranges. Starting with a short overview of historical development, aspects of the physiology of gas exchange (i.e., oxygenation and decarboxylation) during extracorporeal circulation are discussed. The mechanisms of phenomena such as recirculation and shunt playing an important role in daily clinical practice are explained.Treatment of refractory and symptomatic hypoxemic respiratory failure (e.g., acute respiratory distress syndrome [ARDS]) currently represents the main indication for high-flow veno-venous-extracorporeal membrane oxygenation. On the other hand, lower-flow extracorporeal carbon dioxide removal might potentially help to avoid or attenuate ventilator-induced lung injury by allowing reduction of the energy load (i.e., driving pressure, mechanical power) transmitted to the lungs during mechanical ventilation or spontaneous ventilation. In the latter context, extracorporeal carbon dioxide removal plays an emerging role in the treatment of chronic obstructive pulmonary disease patients during acute exacerbations. Both applications of extracorporeal lung support raise important ethical considerations, such as likelihood of ultimate futility and end-of-life decision-making. The review concludes with a brief overview of potential technical developments and persistent challenges.

The impact of obesity on outcomes in patients receiving extracorporeal life support

Extracorporeal life support (ECLS) has been increasingly utilized to manage cardiac and pulmonary dysfunction. The impact of obesity on outcomes of ECLS is poorly defined. The purpose of the study was to compare in-hospital mortality, resource use, complications, and readmissions in obese versus non-obese patients receiving ECLS. We performed a retrospective cohort study of all adult ECLS patients with and without an obesity diagnosis using the 2010-2016 Nationwide Readmissions Database (NRD). Mortality, length of stay (LOS), hospital charges, complications, and readmissions were evaluated using multivariable logistic and linear regression. Of 23 876, patients who received ECLS, 1924 (8.1%) were obese. Obese patients received ECLS more frequently for respiratory failure (29.5% vs. 23.7%, P = .001). After adjustment for patient and hospital factors, obesity was not associated with increased odds of mortality (AOR = 1.06, P = .44) and was associated with decreased LOS (13.7 vs. 21.2 days, P < .001), hospital charges ($171 866 vs. $211 445, P < .001), and 30-day readmission (AOR = 0.71, P = .03). Obesity was also associated with reduced odds of hemorrhage (AOR = 0.43, P < .001), neurologic complications (AOR = 0.55, P = .004), and acute kidney injury (AOR=0.83, P = .04). After stratification by ECLS indication, obesity remained predictive of shorter LOS (AOR range: 0.53-0.78, all P < .05 ) and did not impact mortality (all P > .05). Respiratory support remains the most common indication for ECLS among obese patients. Among all patients, as well as by individual ECLS indication, obesity was not associated with increased odds of mortality. These findings suggest that obesity should not be considered a high-risk contraindication to ECLS.

Long-Term Venovenous Connection for Extracorporeal Carbon Dioxide Removal (ECCO2R)-Numerical Investigation of the Connection to the Common Iliac Veins

Purpose

Currently used cannulae for extracorporeal carbon dioxide removal (ECCO₂R) are associated with complications such as thrombosis and distal limb ischemia, especially for long-term use. We hypothesize that the risk of these complications is reducible by attaching hemodynamically optimized grafts to the patient’s vessels. In this study, as a first step towards a long-term stable ECCO₂R connection, we investigated the feasibility of a venovenous connection to the common iliac veins. To ensure its applicability, the drainage of reinfused blood (recirculation) and high wall shear stress (WSS) must be avoided.

Methods

A reference model was selected for computational fluid dynamics, on the basis of the analysis of imaging data. Initially, a sensitivity analysis regarding recirculation was conducted using as variables: blood flow, the distance of drainage and return to the iliocaval junction, as well as the diameter and position of the grafts. Subsequently, the connection was optimized regarding recirculation and the WSS was evaluated. We validated the simulations in a silicone model traversed by dyed fluid.

Results

The simulations were in good agreement with the validation measurements (mean deviation 1.64%). The recirculation ranged from 32.1 to 0%. The maximum WSS did not exceed 5.57 Pa. The position and diameter of the return graft show the highest influence on recirculation. A correlation was ascertained between recirculation and WSS. Overall, an inflow jet directed at a vessel wall entails not only high WSS, but also a flow separation and thereby an increased recirculation. Therefore, return grafts aligned to the vena cava are crucial.

Conclusion

In conclusion, a connection without recirculation could be feasible and therefore provides a promising option for a long-term ECCO₂R connection.

Extracorporeal Membrane Oxygenation as a Bridge to Lung Transplantation: First Polish Experience

BACKGROUND

Lung transplantation remains the only viable option for patients with end-stage lung diseases. However, due to an insufficient number of lung donors, many potential candidates die without undergoing the procedure. In the cases of some patients, bridges to transplantation can be implemented. One such method is extracorporeal membrane oxygenation (ECMO), which, depending on the type, has the ability to replace patients' circulatory and respiratory function.

CASE PRESENTATION

This case study describes 4 cases of patients, who were successfully bridged to lung transplantation. The first patient developed respiratory failure as a result of acute pulmonary embolisms. His respiratory function was insufficient and he had ECMO implanted for 84 days until he was transplanted. Another patient presented respiratory failure due to massive bleeding, which occurred during transbronchial lung biopsy. Such event led to extensive exacerbation, which resulted in using ECMO as a bridge to recovery at first, but later a bridge to lung transplantation. The patient became a lung graft recipient after 14 days on ECMO. The third patient was a woman who developed severe respiratory failure during the course of the progression of her underlying disease. She was treated with ECMO for 14 days as well, and she also underwent lung transplantation. The fourth patient was qualified for retransplantation. She was bridged to retransplantation via veno-venous ECMO.

CONCLUSION

ECMO can be used a bridge to lung transplantation for suitable patients even for a long period of time, given that it is maintained in accordance with the guidelines.

In Vivo 5 Day Animal Studies of a Compact, Wearable Pumping Artificial Lung

Recent studies show improved outcomes in ambulated lung failure patients. Ambulation still remains a challenge in these patients. This necessitates development of more compact and less cumbersome respiratory support specifically designed to be wearable. The Paracorporeal Ambulatory Assist Lung (PAAL) is being designed for providing ambulatory support in lung failure patients during bridge to transplant or recovery. We previously published in vitro and acute in vivo results of the PAAL. This study further evaluates the PAAL for 5 days. Five-day in vivo studies with the PAAL were conducted in 50-60 kg sheep after heparinization (activated clotting time range: 190-250 s) and cannulation with a 27 Fr. Avalon Elite dual-lumen cannula. The animals were able to move freely in a stanchion while device flow, resistance, and hemodynamics were recorded hourly. Oxygenation and hemolysis were measured daily. Platelet activation, blood chemistry, and comprehensive blood counts are reported for preoperatively, on POD 0, and POD 5. Three animals survived for 5 days. No study termination resulted from device failure. One animal was terminated on POD 0 and one animal was terminated at POD 3. The device was operated between 1.93 and 2.15 L/min. Blood left the device 100% oxygenated. Plasma-free hemoglobin ranged 10.8-14.5 mg/dl. CD62-P expression was under 10%. Minimal thrombus was seen in devices at explant. Chronic use of the PAAL in awake sheep is promising based on our study. There were no device-related complications over the study course. This study represents the next step in our pathway to eventual clinical translation.

Venoarterial extracorporeal membrane oxygenation use in staged combined heart-kidney transplant

Outside of heart and lung transplantation, only few cases have been reported describing venoarterial extracorporeal membrane oxygenation (VA-ECMO) use in solid organ transplantation. We present a case of a staged combined heart-kidney transplant in which VA-ECMO was utilized after a complicated orthotopic heart transplantation to successfully complete the subsequent renal transplantation.

Outcomes of Extracorporeal Membrane Oxygenation as a Bridge to Lung Transplantation

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) as a bridge to lung transplantation (BTT) has become a critical component of caring for patients with end-stage lung disease. This study examined outcomes of patients who received ECMO as a BTT.

METHODS

Statistical analysis was performed on data gathered retrospectively from the electronic medical records of adult patients who received ECMO as BTT at Columbia University Medical Center from April 2009 through July 2018.

RESULTS

A total of 121 adult patients were placed on ECMO as BTT, and 70 patients (59%) were successfully bridged to lung transplantation. Simplified Acute Physiology Score II, unplanned endotracheal intubation, renal replacement therapy, and cerebrovascular accident were identified as independent predictors of unsuccessful BTT. Ambulation was the only independent predictor of successful BTT (odds ratio, 7.579; 95% confidence interval, 2.158 to 26.615; p = 0.002). Among the 64 patients (91%) who survived to hospital discharge, survival was 88% at 1 year and 83% at 3 years. Propensity matching between BTT and non-BTT lung transplant recipients did not show a significant difference in survival (log-rank = 0.53) despite significant differences in the lung allocation score (median, 92.2 [interquartile range, 89.0 to 94.2] vs 49.6 [interquartile range, 40.6 to 72.3], p < 0.01).

CONCLUSIONS

ECMO can be used successfully to bridge patients with end-stage lung disease to lung transplantation. When implemented by an experienced team with adherence to stringent protocols and patient selection, outcomes in BTT patients were comparable to patients who did not receive pretransplant support.

Critical Care before Lung Transplantation

Lung transplantation is widely accepted as the only viable treatment option for patients with end-stage lung disease. However, the imbalance between the number of suitable donor lungs available and the number of possible candidates often results in intensive care unit (ICU) admission for the latter. In the ICU setting, critical care is essential to keep these patients alive and to successfully bridge to lung transplantation. Proper management in the ICU is also one of the key factors supporting long-term success following transplantation. Critical care includes the provision of respiratory support such as mechanical ventilation (MV) and extracorporeal life support (ECLS). Accordingly, a working knowledge of the common critical care issues related to these unique patients and the early recognition and management of problems that arise before and after transplantation in the ICU setting are crucial for long-term success. In this review, we discuss the management and selection of candidates for lung transplantation as well as existing respiratory support strategies that involve MV and ECLS in the ICU setting.

When the momentum has gone: what will be the role of extracorporeal lung support in the future?

PURPOSE OF REVIEW

There has been expanding interest in and use of extracorporeal support in respiratory failure concurrent with technological advances and predominantly observational data demonstrating improved outcomes. However, until there is more available data from rigorous, high-quality randomized studies, the future of extracorporeal support remains uncertain.

RECENT FINDINGS

Outcomes for patients supported with extracorporeal devices continue to show favorable trends. There are several large randomized controlled trials that are in various stages of planning or completion for extracorporeal membrane oxygenation (ECMO) and extracorporeal carbon dioxide removal (ECCO2R) in the acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease (COPD), which may help clarify the role of this technology for these disease processes, and which stand to have a significant impact on a large proportion of patients with acute respiratory failure. Novel applications of extracorporeal lung support include optimization of donor organ quality through ex-vivo perfusion and extracorporeal cross-circulation, allowing for multimodal therapeutic interventions.

SUMMARY

Despite the ongoing rise in ECMO use for acute respiratory failure, its true value will not be known until more information is gleaned from prospective randomized controlled trials. Additionally, there are modalities beyond the current considerations for extracorporeal support that have the potential to revolutionize respiratory failure, particularly in the realm of chronic lung disease and lung transplantation.

Extracorporeal lung support

PURPOSE OF REVIEW

The applications for extracorporeal membrane oxygenation for lung support are constantly evolving. This review highlights fundamental concepts in extracorporeal lung support and describes directions for future research.

RECENT FINDINGS

Since the 1950s, extracorporeal lung support has experienced continuous advancements in circuit design and safety in acute respiratory distress syndrome, chronic obstructive pulmonary disease exacerbations, as a bridge to transplantation, intraoperative cardiopulmonary support, and for transportation to referral centers. Patients on extracorporeal membrane oxygenation are now capable of being awake, extubated, and ambulatory for accelerated recovery or optimization for transplantation.

SUMMARY

Extracorporeal lung support is a safe and an easily implemented intervention for refractory respiratory failure. Recent advances have extended its use beyond acute illnesses and the developments for chronic support will facilitate the development of durable devices and possible artificial lung development.

National trends in volume-outcome relationships for extracorporeal membrane oxygenation

BACKGROUND

The use of extracorporeal membrane oxygenation (ECMO) has emerged as a common therapy for severe cardiopulmonary dysfunction. We aimed to describe the relationship of institutional volume with patient outcomes and examine transfer status to tertiary ECMO centers.

MATERIALS AND METHODS

Using the National Inpatient Sample, we identified adult patients who received ECMO from 2008 to 2014. Individual hospital volume was calculated as tertiles of total institutional discharges for each year independently.

RESULTS

Of the total 18,684 adult patients placed on ECMO, 2548 (13.6%), 5278 (28.2%), and 10,858 (58.1%) patients were admitted to low-, medium-, and high-volume centers, respectively. Unadjusted mortality at low-volume hospitals was less than that of medium- (43.7% versus 50.3%, P = 0.03) and high-volume hospitals (43.7% versus 55.6%, P < 0.001). Length of stay and cost were reduced at low-volume hospitals compared to both medium- and large-volume institutions (all P < 0.001). In high-volume institutions, transferred patients had greater postpropensity-matched mortality (58.5% versus 53.7%, P = 0.05) and cost ($190,299 versus $168,970, P = 0.009) compared to direct admissions. On exclusion of transferred patients from propensity analysis, mortality remained greater in high-volume compared to low-volume centers (50.2% versus 42.8%, P = 0.04). Predictors of mortality included treatment at high-volume centers, respiratory failure, and cardiogenic shock (all P < 0.001).

CONCLUSIONS

Our findings show increased in-hospital mortality in high-volume institutions and in patients transferred to tertiary centers. Whether this phenomenon represents selection bias or transfer from another facility deserves further investigation and will aid with the identification of surrogate markers for quality of high-risk interventions.

Historical perspectives of lung transplantation: connecting the dots

Lung transplantation is now a treatment option for many patients with end-stage lung disease. Now 55 years since the first human lung transplant, this is a good time to reflect upon the history of lung transplantation, to recognize major milestones in the field, and to learn from others' unsuccessful transplant experiences. James Hardy was instrumental in developing experimental thoracic transplantation, performing the first human lung transplant in 1963. George Magovern and Adolph Yates carried out the second human lung transplant a few days later. With a combined survival of only 26 days for these first 2 lung transplant recipients, the specialty of lung transplantation clearly had a long way to go. The first "successful" lung transplant, in which the recipient survived for 10.5 months, was reported by Fritz Derom in 1971. Ten years later, Bruce Reitz and colleagues performed the first successful en bloc transplantation of the heart and one lung with a single distal tracheal anastomosis. In 1988, Alexander Patterson performed the first successful double lung transplant. The modern technique of sequential double lung transplantation and anastomosis performed at the mainstem bronchus level was originally described by Henri Metras in 1950, but was not reintroduced into the field until Pasque reported it again in 1990. Since then, lung transplantation has seen landmark changes: evolving immunosuppression regimens, clarifying the definition of primary graft dysfunction (PGD), establishing the lung allocation score (LAS), introducing extracorporeal membrane oxygenation (ECMO) as a bridge to transplant, allowing donation after cardiac death, and implementing ex vivo perfusion, to name a few. This article attempts to connect the historical dots in this field of research, with the hope that our effort helps summarize what has been achieved, and identifies opportunities for future generations of transplant pulmonologists and surgeons alike.

Increasing Opportunity for Lung Transplant in Interstitial Lung Disease With Pulmonary Hypertension

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) as a bridge to lung transplantation for end-stage interstitial lung disease (ILD) and pulmonary hypertension (PH) has varying results based on ECMO configuration. We compare our experience using venovenous (VV) and venoarterial (VA) ECMO bridge to transplantation for ILD with PH on survival to successful transplantation.

METHODS

A single-center retrospective review was done of patients with ILD and secondary PH who were placed on either VV or VA ECMO as bridge to transplantation from 2010 to 2016. Comparisons for factors associated with survival to transplantation between VV and VA ECMO strategies were made using Cox proportional hazards model. Subgroup analysis included comparisons of VV ECMO patients who remained on VV or were converted to VA ECMO.

RESULTS

A total of 50 patients with ILD and PH were treated initially with either VV (n = 19) or VA (n = 31) ECMO as bridge to lung transplantation. Initial VA ECMO had a significantly higher survival to transplantation compared with initial VV ECMO (p = 0.03). Cox proportional hazards modeling showed a 59% reduction in risk of death for VA compared with VV ECMO (hazard reduction 0.41, 95% confidence interval: 0.18 to 0.92, p = 0.03). Patients converted from VV to VA ECMO had significantly longer survival awaiting transplant than patients who remained on VV ECMO (p = 0.03). Ambulation on ECMO before transplantation was associated with an 80% reduction in the risk of death (hazard reduction 0.20, 95% confidence interval: 0.08 to 0.48, p < 0.01).

CONCLUSIONS

Venoarterial ECMO upper body configuration for patients with end stage ILD and PH significantly improves overall survival to transplantation.

Fiber Bundle Design for an Integrated Wearable Artificial Lung

Mechanical ventilation (MV) and extracorporeal membrane oxygenation (ECMO) are the only viable treatment options for lung failure patients at the end-stage, including acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease (COPD). These treatments, however, are associated with high morbidity and mortality because of long wait times for lung transplant. Contemporary clinical literature has shown ambulation improves post-transplant outcomes in lung failure patients. Given this, we are developing the Pittsburgh Ambulatory Assist Lung (PAAL), a truly wearable artificial lung that allows for ambulation. In this study, we targeted 180 ml/min oxygenation and determined the form factor for a hollow fiber membrane (HFM) bundle for the PAAL. Based on a previously published mass transfer correlation, we modeled oxygenation efficiency as a function of fiber bundle diameter. Three benchmark fiber bundles were fabricated to validate the model through in vitro blood gas exchange at blood flow rates from 1 to 4 L/min according to ASTM standards. We used the model to determine a final design, which was characterized in vitro through a gas exchange as well as a hemolysis study at 3.5 L/min. The percent difference between model predictions and experiment for the benchmark bundles ranged from 3% to 17.5% at the flow rates tested. Using the model, we predicted a 1.75 in diameter bundle with 0.65 m surface area would produce 180 ml/min at 3.5 L/min blood flow rate. The oxygenation efficiency was 278 ml/min/m and the Normalized Index of Hemolysis (NIH) was less than 0.05 g/100 L. Future work involves integrating this bundle into the PAAL for which an experimental prototype is under development in our laboratory.

Extracorporeal Life Support in Lung Transplantation

Extracorporeal life support in lung transplantation has been associated with poor posttransplant outcomes. However, recent advances have resulted in more favorable posttransplant outcomes. The increased use of this technology must be weighed against the risks inherent in its use, especially when complications arising in extracorporeal membrane oxygenation (ECMO)-dependent patients result in loss of transplant candidacy, leaving them with no viable alternative for long-term support. Existing and emerging data support the judicious use of this technology in carefully selected patients at high-volume transplant and ECMO centers that prioritize minimization of sedation, avoidance of endotracheal intubation, and early mobilization.

Bridging to lung transplantation with extracorporeal circulatory support: when or when not?

Patients with end-stage lung disease who are candidates for lung transplantation may acutely decompensate before a donor organ becomes available. In this scenario, extracorporeal life support (ECLS) may be considered as a bridge to transplant or as a bridge to decision. In the current chapter, we review the indications, techniques, and outcomes for bridging to lung transplantation with ECLS.

Psychiatric Aspects of Organ Transplantation in Critical Care: An Update

Transplant patients face challenging medical journeys, with many detours to the intensive care unit. Before and after transplantation, they have significant psychological and cognitive comorbidities, which decrease their quality of life and potentially compromise their medical outcomes. Critical care staff are essential in these journeys. Being cognizant of relevant psychosocial and mental health aspects of transplant patients' experiences can help critical care personnel take comprehensive care of these patients. This knowledge can empower them to understand their patients' psychological journeys, recognize patients' mental health needs, provide initial interventions, and recognize need for expert consultations.

In vitro and in vivo evaluation of a novel integrated wearable artificial lung

BACKGROUND

Conventional extracorporeal membrane oxygenation (ECMO) is cumbersome and is associated with high morbidity and mortality. We are currently developing the Pittsburgh Ambulatory Assist Lung (PAAL), which is designed to allow for ambulation of lung failure patients during bridge to transplant or recovery. In this study, we investigated the in vitro and acute in vivo performance of the PAAL.

METHODS

The PAAL features a 1.75-inch-diameter, cylindrical, hollow-fiber membrane (HFM) bundle of stacked sheets, with a surface area of 0.65 m² integrated with a centrifugal pump. The PAAL was tested on the bench for hydrodynamic performance, gas exchange and hemolysis. It was then tested in 40- to 60-kg adult sheep (n = 4) for 6 hours. The animals were cannulated with an Avalon Elite 27Fr dual-lumen catheter (DLC) inserted through the right external jugular into the superior vena cava (SVC), right atrium (RA) and inferior vena cava (IVC).

RESULTS

The PAAL pumped >250 mm Hg at 3.5 liters/min at a rotation speed of 2,100 rpm. Oxygenation performance met the target of 180 ml/min at 3.5 liters/min of blood flow in vitro, resulting in a gas-exchange efficiency of 278 ml/min/m². The normalized index of hemolysis (NIH) for the PAAL and cannula was 0.054 g per 100 liters (n = 2) at 3.5 liters/min, as compared with 0.020 g per 100 liters (n = 2) for controls (DLC cannula and a Centrimag pump). Plasma-free hemoglobin (pfHb) was <20 mg/dl for all animals. Blood left the device 100% oxygenated in vivo and oxygenation reached 181 ml/min at 3.8 liters/min.

CONCLUSION

The PAAL met in vitro and acute in vivo performance targets. Five-day chronic sheep studies are planned for the near future.

Awake Extracorporeal Membrane Oxygenation as Bridge to Lung Transplantation: A 9-Year Experience

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is used as a bridge to lung transplantation, but characteristics that influence its success are poorly understood. This large, single-center experience evaluated the implementation and outcomes of ECMO in this setting.

METHODS

Data were collected for patients at our institution (New York-Presbyterian Hospital/Columbia University Medical Center in New York) who received ECMO as a bridge to lung transplantation from January 1, 2007 through July 10, 2016. Data were analyzed for demographics, baseline characteristics, survival, and ECMO configuration.

RESULTS

Seventy-two patients received ECMO as a bridge to lung transplantation. Of the 72 patients, 40 (55.6%) underwent the transplantation procedure, 37 (92.5%) survived to discharge, and 21 (84.0%) survived for 2 years. Inotropy or vasopressor support (70% vs 93.8%; p = 0.011), Simplified Acute Physiology Score (26.8 vs 30.5; p = 0.048), and ambulation (80% vs 56.2%; p = 0.030) were significantly different between the patients who underwent lung transplantation and those who did not. Patients with cystic fibrosis were more likely to have a bridge to transplantation than patients with other lung diseases (47.5% vs 25%; p = 0.050). Daily participation in physical therapy was achieved in 50 patients (69.4%).

CONCLUSIONS

This study demonstrated favorable survival in patients receiving ECMO as a bridge to lung transplantation and achieved high rates of physical therapy and avoidance of mechanical ventilation while ECMO was used in patients awaiting lung transplantation. With more than half of these patients successfully bridged to lung transplantation, we gained insight into the factors influencing patients' outcomes, including patient selection, timing of ECMO, and patient management.

"Awake" Extracorporeal Membrane Oxygenation as a Bridge to Lung Transplant

Mortality of patients awaiting lung transplant remains a significant problem as the number of patients on the waiting list far surpasses the number of donor organs available. Interest in the use of "awake" extracorporeal membrane oxygenation (ECMO) as a bridge to lung transplant has emerged because this strategy offers several benefits over mechanical ventilation. This article provides a review of relevant literature and discusses indications and complications of awake ECMO therapy, cannulation strategies, and nursing considerations for this patient population.

A global perspective of lung transplantation: Part 1 - Recipient selection and choice of procedure

Lung transplantation has grown considerably in recent years and its availability has spread to an expanding number of countries worldwide. Importantly, survival has also steadily improved, making this an increasingly viable procedure for patients with end-stage lung disease and limited life expectancy. In this first of a series of articles, recipient selection and type of transplant operation are reviewed. Pulmonary fibrotic disorders are now the most indication in the U.S., followed by chronic obstructive pulmonary disease and cystic fibrosis. Transplant centers have liberalized criteria to include older and more critically ill candidates. A careful, systematic, multi-disciplinary selection process is critical in identifying potential barriers that may increase risk and optimize long-term outcomes.

Veno-veno-arterial ECMO support for acute myocarditis combined with ARDS: a case report

BACKGROUND

In patients who developed a combined situation of severe acute respiratory distress syndrome with refractory hypoxemia and acute cardiac failure with circulatory collapse, traditional veno-venous or veno-arterial extracorporeal membrane oxygenation approach alone may not be sufficient enough to maintain both an acceptable range of gas exchange and a hemodynamic stability.

CASE REPORT

A 27-year-old male patient was suffering from severe acute respiratory distress syndrome caused by community-acquired pneumonia and acute myocarditis with circulatory shock. After mechanical ventilation for respiratory support, he was in a persistently refractory shock state. Veno-veno-arterial mode of extracorporeal membrane oxygenation was thus applied to provide both respiratory and circulatory support simultaneously, with good success.

DISCUSSION

Modifying to a veno-veno-arterial mode can be another alternative strategy in a combined situation of refractory respiratory and cardiac failure, thus providing not only respiratory support but also circulatory support. In veno-veno-arterial mode, the returning circuit from the pump was divided with a Y connector into 2 reinfusion circuits; each reinfusion circuit was connected to the contralateral side femoral vein and artery, respectively. The distribution of reinfusion flow was adjusted depending on the patient's cardiopulmonary status.

CONCLUSIONS

Although there is no consensus about the veno-veno-arterial mode of extracorporeal membrane oxygenation, this combined mode can be helpful in patients with acute refractory respiratory and cardiac failure, as shown in the present case. We need further experience and improvements in the circuit system used in the veno-veno-arterial mode of ECMO.