Growing Experience with Extracorporeal Membrane Oxygenation as a Bridge to Lung Transplantation

Clinical Outcomes With Extracorporeal Membrane Oxygenation for Interstitial Lung Disease: Systematic Review and Meta-Analysis

The evidence on indications, outcomes, and complications with the use of extracorporeal membrane oxygenation (ECMO) in the setting of interstitial lung disease (ILD) is limited in the existing literature. We performed a systematic review and meta-analysis for the use of ECMO in the setting of ILD to study the prognostic factors associated with in-hospital mortality. Eighteen unique studies with a total of 1,356 patients on ECMO for ILD were identified out of which 76.5% were on ECMO as a bridge to transplant (BTT) and the rest as a bridge to recovery (BTR). The overall in-hospital mortality was 45.76%, with 71.3% and 37.8% for BTR and BTT, respectively. Among the various prognostic factors, mortality was lower with younger age (mean difference = 3.15, 95% confidence interval [CI] = 0.82-5.49), use of awake veno-arterial (VA)-ECMO compared to veno-venous (VV)-ECMO (unadjusted odds ratio [OR] = 0.22, 95% CI = 0.13-0.37) in the overall cohort. In the setting of BTT, the use of VA-ECMO had a decreased hazard ratio (HR) compared to VV-ECMO (adjusted HR = 0.34, 95% CI = 0.15-0.81, p = 0.015). The findings of our meta-analysis are critical but are derived from retrospective studies with small sample sizes and thus are of low to very low-GRADE certainty.

Primary graft dysfunction following lung transplantation: From pathogenesis to future frontiers

Lung transplantation is the treatment of choice for patients with end-stage lung disease. Currently, just under 5000 lung transplants are performed worldwide annually. However, a major scourge leading to 90-d and 1-year mortality remains primary graft dysfunction. It is a spectrum of lung injury ranging from mild to severe depending on the level of hypoxaemia and lung injury post-transplant. This review aims to provide an in-depth analysis of the epidemiology, pathophysiology, risk factors, outcomes, and future frontiers involved in mitigating primary graft dysfunction. The current diagnostic criteria are examined alongside changes from the previous definition. We also highlight the issues surrounding chronic lung allograft dysfunction and identify the novel therapies available for ex-vivo lung perfusion. Although primary graft dysfunction remains a significant contributor to 90-d and 1-year mortality, ongoing research and development abreast with current technological advancements have shed some light on the issue in pursuit of future diagnostic and therapeutic tools.

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.

Contemporary trends in PGD incidence, outcomes, and therapies

BACKGROUND

We sought to describe trends in extracorporeal membrane oxygenation (ECMO) use, and define the impact on PGD incidence and early mortality in lung transplantation.

METHODS

Patients were enrolled from August 2011 to June 2018 at 10 transplant centers in the multi-center Lung Transplant Outcomes Group prospective cohort study. PGD was defined as Grade 3 at 48 or 72 hours, based on the 2016 PGD ISHLT guidelines. Logistic regression and survival models were used to contrast between group effects for event (i.e., PGD and Death) and time-to-event (i.e., death, extubation, discharge) outcomes respectively. Both modeling frameworks accommodate the inclusion of potential confounders.

RESULTS

A total of 1,528 subjects were enrolled with a 25.7% incidence of PGD. Annual PGD incidence (14.3%-38.2%, p = .0002), median LAS (38.0-47.7 p = .009) and the use of ECMO salvage for PGD (5.7%-20.9%, p = .007) increased over the course of the study. PGD was associated with increased 1 year mortality (OR 1.7 [95% C.I. 1.2, 2.3], p = .0001). Bridging strategies were not associated with increased mortality compared to non-bridged patients (p = .66); however, salvage ECMO for PGD was significantly associated with increased mortality (OR 1.9 [1.3, 2.7], p = .0007). Restricted mean survival time comparison at 1-year demonstrated 84.1 days lost in venoarterial salvaged recipients with PGD when compared to those without PGD (ratio 1.3 [1.1, 1.5]) and 27.2 days for venovenous with PGD (ratio 1.1 [1.0, 1.4]).

CONCLUSIONS

PGD incidence continues to rise in modern transplant practice paralleled by significant increases in recipient severity of illness. Bridging strategies have increased but did not affect PGD incidence or mortality. PGD remains highly associated with mortality and is increasingly treated with salvage ECMO.

Lung transplantation for the treatment of irreversible acute respiratory distress syndrome

BACKGROUND

Despite advances in critical care for acute respiratory distress syndrome (ARDS), some survivors in the acute phase are unable to wean from extracorporeal membrane oxygenation (ECMO) or mechanical ventilation. To date, little is known regarding whether lung transplantation confers a survival benefit for irreversible ARDS.

METHODS

This retrospective study was conducted using the United Network for Organ Sharing database (May 2005-December 2018). Patients with restrictive lung disease were divided into two groups: patients with and without ARDS. Propensity score matching identified recipients without ARDS for the control group.

RESULTS

A total of 63 patients with ARDS were waitlisted for lung transplantation, while 39 received a lung transplant after a median waitlist duration of 8 days. Seventy-eight patients were matched as controls. In the ARDS group, the median age was 30 years, and the median lung allocation score was 88.4. Among the 39 recipients, 30 (76.9%) received ECMO support prior to transplantation. Lung transplantation for ARDS and restrictive lung disease showed similar 90-day (87.2% vs. 88.5%, p = .80), 1-year (82.1% vs. 85.9%, p = .52), and 3-year (69.2% vs. 65.4%, p = .94) survival rates.

CONCLUSIONS

Lung transplantation provides acceptable outcomes in selected patients with irreversible ARDS.

Extracorporeal membrane oxygenation as a bridge vs. non-bridging for lung transplantation: A systematic review and meta-analysis

Whether extracorporeal membrane oxygenation (ECMO) as a bridge to lung transplantation (BTT) can achieve a similar survival to non-BTT remains controversial. We conducted this meta-analysis to compare the outcomes between ECMO BTT and non-BTT to facilitate better clinical decision-making. Seven databases were searched for eligible studies comparing ECMO BTT and non-BTT. The primary endpoints included survival, intraoperative indicators, postoperative hospitalization indicators, and postoperative complications. Nineteen studies (involving 7061 participants) were included in the final analysis. The outcomes of overall survival, overall survival rate, graft survival rate, in-hospital mortality, postoperative hospital days, postoperative intensive care unit days, postoperative ventilation time, blood transfusion volume, and postoperative complications were all better in the non-BTT group. The total mortality in ECMO bridging was 23.03%, in which the top five causes of death were right heart failure (8.03%), multiple organ failure (7.03%), bleeding (not cranial) (4.67%), cranial bleeding (3.15%), and sepsis (2.90%). In summary, Non-BTT is associated with better survival and fewer complications compared to BTT. When ECMO may be the only option, the patient and medical team need to realize the increased risk of ECMO by complications and survival.

Peripheral femoral venoarterial extracorporeal membrane oxygenation as bridge to heart-lung transplant omne iter incipit primus

Heart-lung transplant (HLT) is a widely accepted modality for certain patients with advanced and refractory cardiopulmonary disease. Some of these patients are critically ill on the transplant waiting list, and venoarterial extracorporeal membrane oxygenation (VA-ECMO) can be used as a bridge to transplantation. Although the experience with ECMO as a bridge to lung transplant is promising, there is limited evidence to use ECMO as a bridge to HLT. Femoral cannulation remains a concern for ambulation given the risk of bleeding and cannula complications despite studies reporting its safety. We present a case of a 56-year-old male with interstitial lung disease and severe secondary pulmonary hypertension, who was successfully bridged to HLT with ambulatory femoral VA-ECMO.

Bridging to lung transplantation with double-lumen venovenous extracorporeal membrane oxygenation

BACKGROUND

Double-lumen venovenous extracorporeal membrane oxygenation may be used as a bridge to lung transplantation. Predictors of outcome with this strategy have not been well described.

METHODS

All patients with irreversible lung disease who developed acute pulmonary failure and required double-lumen venovenous extracorporeal membrane oxygenation as a bridge to decision or lung transplant at our institution were included in this study. Survival of the extracorporeal membrane oxygenation patients was compared with listed patients who did not require extracorporeal membrane oxygenation with lung allocation score in the highest 10% for the same period.

RESULTS

Fifteen patients (46 ± 17 years old) received double-lumen venovenous extracorporeal membrane oxygenation cannula. Mean length of extracorporeal membrane oxygenation support was 18.2 (1-60) days. Of these, seven patients were bridged to lung transplant, six died on extracorporeal membrane oxygenation, and two weaned to recovery. Amount of red blood cell transfusion was significantly higher (3.3 vs 18.5 U, p = 0.003) and lowest oxygen saturation was significantly lower in non-survivors (84.5% vs 66.3%, p = 0.002). Of the seven patients who were already listed for lung transplant at the onset of extracorporeal membrane oxygenation, five were transplanted. Overall survival to hospital discharge was 60%. Survival of patients with lung allocation score in the highest 10% (average lung allocation score 83.4) in the same period was 80%.

CONCLUSION

Double-lumen venovenous extracorporeal membrane oxygenation cannula is a feasible option to bridge patients to decision or lung transplantation. Blood transfusion requirement and low oxygen saturation are markers of poor prognosis. Listing status at the time of cannulation and ambulation during extracorporeal membrane oxygenation support may be important indicators of good outcome.

Twenty-year experience with extracorporeal life support as bridge to lung transplantation

OBJECTIVES

Extracorporeal life support is increasingly used to bridge deteriorating candidates to lung transplantation. Nevertheless, only few systematic reports with a limited number of patients exist describing this practice and its changes over time.

METHODS

We retrospectively reviewed our institutional database and performed an era analysis to identify trends over time and risk factors for mortality. After applying propensity score matching, outcomes of bridged patients were compared with those of standard lung transplantation recipients.

RESULTS

Extracorporeal life support was used in 120 patients as an intention to bridge to lung transplantation. Eleven patients (9.2%) were bridged between 1998 and 2004, 39 patients (32.5%) were bridged between 2005 and 2010, and 70 patients were bridged (58.3%) between 2010 and 2017. In the first era, the main bridging modality was venoarterial-extracorporeal membrane oxygenation (n = 10, 90.9%), whereas venovenous devices were primarily used in later eras (second era: n = 18, 46.2%; third era: n = 39, 55.8%). In the second and third eras, 9 patients (23.1%) and 24 patients (34.3%) could be bridged awake. Short-term outcome was poor in the first era, with only 36.4% of patients discharged alive but improved in later eras (53.8% and 77.1%; P = .002). Extracorporeal life support-bridged patients showed an impaired short-term outcome compared with standard recipients. However, survival conditional on 90 days did not differ among the groups (P = .178). In univariate and multivariate analyses, awake extracorporeal life support was protective for survival, whereas acute retransplantation was a risk factor for mortality.

CONCLUSIONS

Over the past 2 decades, the role of extracorporeal life support bridging evolved from an acute rescue therapy to a semi-elective procedure. Stratified outcome analysis revealed that extracorporeal life support bridging yielded similar long-term survival compared with nonbridged patients.

Intensive care, right ventricular support and lung transplantation in patients with pulmonary hypertension

Intensive care of patients with pulmonary hypertension (PH) and right-sided heart failure includes treatment of factors causing or contributing to heart failure, careful fluid management, and strategies to reduce ventricular afterload and improve cardiac function. Extracorporeal membrane oxygenation (ECMO) should be considered in distinct situations, especially in candidates for lung transplantation (bridge to transplant) or, occasionally, in patients with a reversible cause of right-sided heart failure (bridge to recovery). ECMO should not be used in patients with end-stage disease without a realistic chance for recovery or for transplantation. For patients with refractory disease, lung transplantation remains an important treatment option. Patients should be referred to a transplant centre when they remain in an intermediate- or high-risk category despite receiving optimised pulmonary arterial hypertension therapy. Meticulous peri-operative management including the intra-operative and post-operative use of ECMO effectively prevents graft failure. In experienced centres, the 1-year survival rates after lung transplantation for PH now exceed 90%.

Recent advances in lung transplantation

Lung transplantation can improve quality of life and prolong survival for individuals with end-stage lung disease, and many advances in the realms of both basic science and clinical research aspects of lung transplantation have emerged over the past few decades. However, many challenges must yet be overcome to increase post-transplant survival. These include successfully bridging patients to transplant, expanding the lung donor pool, inducing tolerance, and preventing a myriad of post-transplant complications that include primary graft dysfunction, forms of cellular and antibody-mediated rejection, chronic lung allograft dysfunction, and infections. The goal of this manuscript is to review salient recent and evolving advances in the field of lung transplantation.

Lung transplantation: indications and contraindications

The selection of appropriate recipients for lung transplantation is an evolving discipline. As experience with the procedure has developed over the last decades, the identification of transplant candidates has also changed as transplant centers strive to safely provide the therapy to as many patients possible. The International Society for Heart and Lung Transplantation (ISHLT) has developed three editions of recipient selection guidelines. Published in 1998, 2006, and 2015, these guidelines represented the best information relevant to the appropriate selection of lung transplant candidates. A discussion of areas supported by the most robust scientific data will be undertaken, but in many aspects of recipient selection, there is a paucity of data upon which to rely. Therefore, it is ultimately the prerogative and responsibility of individual centers to determine, after carefully weighing the best evidence available, whether a patient is deemed a suitable candidate at a specific program. All possible indications and contraindications for transplantation will be reviewed with attention also given to the appropriate timing of referral and listing of patients with advanced lung disease to a transplant center.

Fourteen Day In Vivo Testing of a Compliant Thoracic Artificial Lung

The compliant thoracic artificial lung (cTAL) has been studied in acute in vivo and in vitro experiments. The cTAL's long-term function and potential use as a bridge to lung transplantation are assessed presently. The cTAL without anticoagulant coatings was attached to sheep (n = 5) via the pulmonary artery and left atrium for 14 days. Systemic heparin anticoagulation was used. Compliant thoracic artificial lung resistance, cTAL gas exchange, hematologic parameters, and organ function were recorded. Two sheep were euthanized for nondevice-related issues. The cTAL's resistance averaged 1.04 ± 0.05 mmHg/(L/min) with no statistically significant increases. The cTAL transferred 180 ± 8 ml/min of oxygen with 3.18 ± 0.05 L/min of blood flow. Except for transient surgical effects, organ function markers were largely unchanged. Necropsies revealed pulmonary edema and atelectasis but no other derangements. Hemoglobin levels dropped with device attachment but remained steady at 9.0 ± 0.1 g/dl thereafter. In a 14 day experiment, the cTAL without anticoagulant coatings exhibited minimal clot formation. Sheep physiology was largely unchanged except for device attachment-related hemodilution. This suggests that patients treated with the cTAL should not require multiple blood transfusions. Once tested with anticoagulant coatings and plasma resistant gas exchange fiber, the cTAL could serve as a bridge to transplantation.

Contemporary Outcomes of Extracorporeal Membrane Oxygenation Used as Bridge to Lung Transplantation

BACKGROUND

Extracorporeal membrane oxygenation (ECMO), when used as bridge to lung transplantation, (BTT) identifies high-risk candidates. Recent advances in cannula design and patient selection fosters "awake ambulatory ECMO" as a viable option for critically ill candidates in an attempt to retard deconditioning while awaiting allografts.

METHODS

From 2012 to 2015, 30 patients underwent ECMO as BTT. Candidacy for ECMO was determined before listing for transplant. A dual-lumen single cannula was used first in 13 of 30 patients (43%). Of the remaining 30 patients, 6 (20%) were supported with venoarterial ECMO and 11 (37%) with venovenous ECMO, with double-site cannulation in 11 (37%), and 6 of 11 converted to a dual-lumen single cannula. All ECMO patients were managed in a dedicated heart/lung failure intensive care unit, and early aggressive physical therapy, ambulation, and spontaneous breathing trials were emphasized.

RESULTS

BTT was successful in 26 patients (87%). In the 19 patients with dual-lumen single cannula, 5 (26%) were successfully ambulated, and 6 (32%) achieved spontaneous ventilation. Median (25th, 75th percentile) lengths of stay in the intensive care unit and hospital were 33 days (20, 46 days) and 56 days (28, 78 days), respectively, and were 20 and 31 days, respectively, in patients successfully ambulated (intensive care unit: p = 0.5; hospital: p = 0.4). Among all patients who received a transplant, 30-day, 1-year, and 3-year survival were 92%, 85%, and 80%, respectively. Among patients undergoing primary transplants, 3-year survival was 91%.

CONCLUSIONS

ECMO as BTT has led to encouraging perioperative outcomes and early survival. Careful patient selection and early use of ECMO seems to allow for preservation of vitality while these critically ill candidates await donor organs, which may improve outcomes.

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.

Extracorporeal membrane oxygenation as a bridge to lung transplantation: A single-center experience in the present era

OBJECTIVE

Extracorporeal membrane oxygenation has been used as a bridge to lung transplantation in patients with rapid pulmonary function deterioration. The reported success of this modality and perioperative and functional outcomes are varied.

METHODS

We retrospectively reviewed all patients who underwent lung transplantation at our institution over 1 year (January 1, 2015, to December 31, 2015). Patients were divided into 2 groups depending on whether they required extracorporeal membrane oxygenation support as a bridge to transplant; preoperative characteristics, lung transplantation outcomes, and survival were compared between groups.

RESULTS

Of the 93 patients, 12 (13%) received bridge to transplant, and 81 (87%) did not. Patients receiving bridge to transplant were younger, had higher lung allocation scores, had lower functional status, and were more often on mechanical ventilation at listing. Most patients who received bridge to transplant (n = 10, 83.3%) had pulmonary fibrosis. Mean pretransplant extracorporeal membrane oxygenation support was 103.6 hours in duration (range, 16-395 hours). All patients who received bridge to transplant were decannulated immediately after lung transplantation but were more likely to return to the operating room for secondary chest closure or rethoracotomy. Grade 3 primary graft dysfunction within 72 hours was similar between groups. Lung transplantation success and hospital discharge were 100% in the bridge to transplant group; however, these patients experienced longer hospital stays and higher rates of discharge to acute rehabilitation. The 1-year survival was 100% in the bridge to transplant group and 91% in the non-bridge to transplant group (log-rank, P = .24). The 1-year functional status was excellent in both groups.

CONCLUSIONS

Extracorporeal membrane oxygenation can be used to safely bridge high-acuity patients with end-stage lung disease to lung transplantation with good 30-day, 90-day, and 1-year survival and excellent 1-year functional status. Long-term outcomes are being studied.

Extracorporeal membrane oxygenation in the pre and post lung transplant period

Evolution in technology has resulted in rapid increase in utilization of extracorporeal membrane oxygenation (ECMO) as a bridge to recovery and/or transplantation. Although there is limited evidence for the use of ECMO, recent improvements in ECMO technology, personnel training, ambulatory practices on ECMO and lung protective strategies have resulted in improved outcomes in patients bridged to lung transplantation. This review provides an insight into the current outcomes and best practices for utilization of ECMO in the pre- and post-lung transplantation period.

"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.

State of the Art: Bridging to lung transplantation using artificial organ support technologies

Lung transplantation increasingly is being performed in recipients of higher risk and acuity. A subset of these patients has severely abnormal gas exchange and/or right ventricular dysfunction, such that artificial organ support strategies are required to bridge patients to lung transplantation. We review the rationales and currently used and potential strategies for bridging to lung transplantation and characterize bridging outcomes. Based on physiologic reasoning and a study of the existing literature, we provide a working strategy for bridging to lung transplantation.

Lung Transplantation

The therapeutic options for patients with advanced pulmonary parenchymal or vascular disorders are currently limited. Lung transplantation remains one of the few viable interventions, but on account of the insufficient donor pool only a minority of these patients actually undergo the procedure each year. Following transplantation there are a number of early and late allograft complications such as primary graft dysfunction, allograft rejection, infection, post-transplant lymphoproliferative disorder and late injury that is now classified as chronic lung allograft dysfunction. The pathologist plays an essential role in the diagnosis and classification of these myriad complications. Although the transplant procedures are performed in selected centers patients typically return to their local centers. When complications arise it is often the responsibility of the local pathologist to evaluate specimens. Therefore familiarity with the pathology of lung transplantation is important.

Canada's longest experience with extracorporeal membrane oxygenation as a bridge to lung transplantation: a case report

INTRODUCTION

Extracorporeal membrane oxygenation (ECMO) is a method of enabling gas exchange through an external membrane used to treat respiratory failure in critically ill patients. ECMO as a bridge to lung transplantation has been investigated as a potential method of reducing lung transplantation waitlist mortality. Herein we describe a case of ECMO as a bridge-to-lung transplantation for the duration of 35 days, which is the longest documented length of ECMO support before successful transplantation in Canada.

CASE DESCRIPTION

The prospective recipient was a 28-year-old female suffering from stage 4 pulmonary sarcoidosis. Given an acute exacerbation of her chronic respiratory failure, ECMO had to be initiated. She remained on ECMO for 35 days until a suitable set of donor lungs became available. The recipient had a prolonged course in hospital but was successfully discharged home where she continues to have good lung function. She remains alive and well at home 5 months post-transplantation and continues to improve and gain strength.

CONCLUSION

Our case provides hope that in the future we may be able to expand the population of recipients who may be candidates for lung transplantation. This case adds to the growing literature on the role of ECMO as a bridge-to-lung transplantation with the potential to reduce patient deaths while wait-listed for lung transplantation as well as increase the number of transplantations being performed.

Extracorporeal Membrane Oxygenation Applications in Cardiac Critical Care

The use of extracorporeal membrane oxygenation therapy (ECMO) in cardiac critical care has steadily increased over the past decade. Significant improvements in the technology associated with ECMO have propagated this recent resurgence and contributed to improved patient outcomes in the fields of cardiac and transplant (heart and lung) surgery. Specifically, ECMO is being increasingly utilized as a bridge to heart and lung transplantation, as well as to ventricular assist device placement. ECMO is also employed during the administration of cardiopulmonary resuscitation, known as extracorporeal life support. In this review, we examine the recent literature regarding the applications of ECMO and also describe emerging topics involving current ECMO management strategies.

Recipient risk factors and lung transplant outcomes

PURPOSE OF REVIEW

Scientific and technical developments in the field of lung transplantation have allowed it to become a successful treatment option for various end-stage lung diseases. As the demand for lung allografts increases and waitlists expand, it is vital that lung transplant centers optimize use of this limited resource by selecting recipients who have the best prospects of positive long-term outcomes. Recipient selection criteria vary across transplant selection committees. We review the most recent body of literature for recipient consideration and describe potential effects on morbidity and mortality posttransplantation.

RECENT FINDINGS

Although prior guidelines for contraindications to lung transplantation have been described, the benchmarks for recipient selection are constantly being challenged. Age, weight, and psychologic condition of recipients pretransplant have more recently been shown to have significant influence on posttransplant outcomes. Advancements in human leukocyte antigen antibody testing and use of extracorporeal membrane oxygenation as a bridge to lung transplantation have additionally impacted recipient selection standards.

SUMMARY

Recipient selection criteria continue to evolve because of advances in mechanical bridging to transplant and postoperative management. This review will cover some of the new concepts in lung transplant recipient selection and their potential effect on posttransplant outcomes.

Current State of Pediatric Lung Transplantation

Cardiothoracic transplantation has significantly impacted the lives of pediatric patients with advanced cardiopulmonary failure. The current state of lung transplantation in children as well as its ongoing and future challenges are discussed.

Extracorporeal life support as bridge to lung transplantation: a systematic review

INTRODUCTION

Patients with acute respiratory failure requiring respiratory support with invasive mechanical ventilation while awaiting lung transplantation are at a high risk of death. Extracorporeal membrane oxygenation (ECMO) has been proposed as an alternative bridging strategy to mechanical ventilation. The aim of this study was to assess the current evidence regarding how the ECMO bridge influences patients' survival and length of hospital stay.

METHODS

We performed a systematic review by searching PubMed, EMBASE and the bibliographies of retrieved articles. Three reviewers independently screened citation titles and abstracts and agreement was reached by consensus. We selected studies enrolling patients who received ECMO with the intention to bridge lung transplant. We included randomized controlled trials (RCTs), case-control studies and case series with ten or more patients. Outcomes of interest included survival and length of hospital stay. Quantitative data summaries were made when feasible.

RESULTS

We identified 82 studies, of which 14 were included in the final analysis. All 14 were retrospective studies which enrolled 441 patients in total. Because of the broad heterogeneity among the studies we did not perform a meta-analysis. The mortality rate of patients on ECMO before lung transplant and the one-year survival ranged from 10% to 50% and 50% to 90%, respectively. The intensive care and hospital length of stay ranged between a median of 15 to 47 days and 22 to 47 days, respectively. There was a general paucity of high-quality data and significant heterogeneity among studies in the enrolled patients and technology used, which confounded analysis.

CONCLUSIONS

In most of the studies, patients on ECMO while awaiting lung transplantation also received invasive mechanical ventilation. Therefore, whether ECMO as an alternative, rather than an adjunction, to invasive mechanical ventilation is a better bridging strategy to lung transplantation still remains an unresolved issue. ECMO support as a bridge for these patients could provide acceptable one-year survival. Future studies are needed to investigate ECMO as part of an algorithm of care for patients with end-stage lung disease.

Awake extracorporeal membrane oxygenation bridging for pulmonary retransplantation provides comparable results to elective retransplantation

BACKGROUND

Lung retransplantation became an accepted treatment for bronchiolitis obliterans syndrome (BOS). However, the value of different bridging modalities for these patients is controversial.

METHODS

We analyzed outcomes of 39 patients listed for retransplantation between 2008 and 2012. Patients were divided in 3 groups: 23 patients without any bridge modality (elective, Group 1), 11 patients on ventilation and full sedation with or without extracorporeal membrane oxygenation (ECMO) support (sedated bridging, Group 2), and 5 patients awake on ECMO support (awake bridging, Group 3).

RESULTS

Waiting list mortality was 13% in Group 1, 39% in Group 2, and 0% in Group 3. Perioperative mortality was 20% in Group 1, 29% in Group 2, and 0% in Group 3. Significant differences between Groups 1 and 2 were calculated for time on post-operative ventilation (17.4 vs 27.3 days, p = 0.022), intensive care unit stay (22.0 vs 32.9 days, p = 0.026), and hospital stay (34.7 vs 54.1 days, p = 0.013). However, there were no significant differences between Groups 1 and 3 for post-operative ventilation time (17.4 vs 13.4 days, p = 0.192), for intensive care unit stay (22.0 vs 26.4 days, p = 0.169), or for hospital stay (34.7 vs 34.8 days, p = 0.367). Survival rates at 90 days, 1 year, and 2 years were 80%, 70%, and 53% in Group 1; 71%, 43%, and 29% in Group 2; and 100%, 60%, and 60% in Group 3, respectively.

CONCLUSION

Awake ECMO bridging for retransplantation provides comparable results to elective retransplantation.

A consensus document for the selection of lung transplant candidates: 2014--an update from the Pulmonary Transplantation Council of the International Society for Heart and Lung Transplantation

The appropriate selection of lung transplant recipients is an important determinant of outcomes. This consensus document is an update of the recipient selection guidelines published in 2006. The Pulmonary Council of the International Society for Heart and Lung Transplantation (ISHLT) organized a Writing Committee of international experts to provide consensus opinion regarding the appropriate timing of referral and listing of candidates for lung transplantation. A comprehensive search of the medical literature was conducted with the assistance of a medical librarian. Writing Committee members were assigned specific topics to research and discuss. The Chairs of the Writing Committee were responsible for evaluating the completeness of the literature search, providing editorial support for the manuscript, and organizing group discussions regarding its content. The consensus document makes specific recommendations regarding the timing of referral and of listing for lung transplantation. These recommendations include discussions not present in previous ISHLT guidelines, including lung allocation scores, bridging to transplant with mechanical circulatory and ventilator support, and expanded indications for lung transplantation. In the absence of high-grade evidence to support decision making, these consensus guidelines remain part of a continuum of expert opinion based on available studies and personal experience. Some positions are immutable. Although transplant is rightly a treatment of last resort for end-stage lung disease, early referral allows proper evaluation and thorough patient education. Subsequent waiting list activation implies a tacit agreement that transplant offers a significant individual survival advantage. It is both the challenge and the responsibility of the transplant community globally to ensure organ allocation maximizes the potential benefits of a scarce resource, thereby achieving that advantage.

Prolonged duration ECMO for ARDS: futility, native lung recovery, or transplantation?

Extracorporeal membrane oxygenation (ECMO) is recommended as a treatment modality for severe acute respiratory distress syndrome (PaO2/FiO2 ≤ 100 mm Hg with positive end-expiratory pressure ≥ 5 cm H2O) as defined by the Berlin definition. The reported usual duration of ECMO in these patients is 7-10 days. However, increasing reports of prolonged duration ECMO (>14 days) for respiratory failure document survival rates of 50-70% with native lung recovery, and ECMO bridge to lung transplantation has been performed at many centers. At present, there are no established national criteria for when to consider futility or lung transplantation in adult patients requiring ECMO for acute respiratory failure. We report a case of prolonged duration venovenous-ECMO (1,347 hours, 56.13 days), with native lung recovery and discuss treatment strategies to optimize native lung recovery in ECMO patients. The lung may have unexpected regenerative capacity with native lung recovery after prolonged mechanical support, similar to acute kidney injury and native renal recovery. We recommend redefining irreversible lung injury and futility in ECMO.

Extracorporeal carbon dioxide removal through ventilation of acidified dialysate: an experimental study

BACKGROUND

Extracorporeal (EC) carbon dioxide (CO(2)) removal (ECCO(2)R) may be a powerful alternative to ventilation, possibly avoiding the need for mechanical ventilation and endotracheal intubation. We previously reported how an infusion of lactic acid before a membrane lung (ML) effectively enhances ECCO(2)R. We evaluated an innovative ECCO(2)R technique based on ventilation of acidified dialysate.

METHODS

Four swine were sedated, mechanically ventilated, and connected to a venovenous dialysis circuit (blood flow, 250 ml/min). The dialysate was recirculated in a closed loop circuit including a ML (gas flow, 10 liters/min) and then returned to the dialyzer. In each animal, 4 different dialysis flows (DF) of 200, 400, 600, and 800 ml/min were evaluated with and without lactic acid infusion (2.5 mEq/min); the sequence was completed 3 times. At the end of each step, we measured the volume of CO(2)R by the ML (V(co2)ML) and collected blood and dialysate samples for gas analyses.

RESULTS

Acid infusion substantially increased V(co2)ML, from 33 ± 6 ml/min to 86 ± 7 ml/min. Different DFs had little effect on V(co2)ML, which was only slightly reduced at DF 200 ml/min. The partial pressure of CO(2) of blood passing through the dialysis filter changed from 60.9 ± 3.6 to 37.1 ± 4.8 mm Hg without acidification and to 32.5 ± 5.3 mm Hg with acidification, corresponding to a pH increase of 0.18 ± 0.03 and 0.03 ± 0.04 units, respectively.

CONCLUSIONS

Ventilation of acidified dialysate efficiently increased ECCO(2)R of an amount corresponding to 35% to 45% of the total CO(2) production of an adult man from a blood flow as low as 250 ml/min.

Resource use trends in extracorporeal membrane oxygenation in adults: an analysis of the Nationwide Inpatient Sample 1998-2009

OBJECTIVE

The study objective was to determine whether significant trends over time have occurred in resource use associated with the use of extracorporeal membrane oxygenation in critically ill adults.

METHODS

All adult admissions involving extracorporeal membrane oxygenation were examined by using the Nationwide Inpatient Sample database (years 1998-2009). Trends in volume, outcome, and resource use (including hospital charges, length of stay, and charges per day) were analyzed.

RESULTS

An estimated total of 8753 admissions involved extracorporeal membrane oxygenation over the study period. Overall length of stay was 18.3 ± 1.3 days. Total hospital charges averaged $344,009 ± $30,707 per admission, with average charges per day of $40,588 ± $3099. Cumulative national charges for extracorporeal membrane oxygenation admissions increased significantly from $109.0 million in 1998 to $764.7 million in 2009 (P = .0016). Charges per patient and length of stay also increased significantly (P = .0032 and .0321, respectively). The increasing trend in the number of extracorporeal membrane oxygenation admissions during the study period was not statistically significant (P = .19). The post-cardiotomy group had more favorable outcomes and lower resource use. A shift was observed in the relative case-mix of extracorporeal membrane oxygenation admissions over the study period, with a relative decrease in the post-cardiotomy group and increases in the cardiogenic shock, respiratory failure, and lung transplant groups.

CONCLUSIONS

These results suggest that dramatic increases in resource use associated with extracorporeal membrane oxygenation are not solely the result of increased volume, but in part are due to a shift toward extracorporeal membrane oxygenation use in patient groups (other than in the post-cardiotomy setting) with greater resource use and worse outcomes.

Parameters associated with short- and midterm survival in bridging to lung transplantation with extracorporeal membrane oxygenation

Patients with terminal lung failure may be bridged to lung transplantation (LTX) by extracorporeal membrane oxygenation (ECMO). With the present shortage of donor organs and the high level of invasiveness of ECMO treatment, appropriate selection criteria for bridge to transplant need to be defined. We report retrospective data from 26 patients on ECMO listed for LTX. Seven patients were successfully transplanted (LTX-s). Six patients survived until transplantation, but died intra- or post-operatively (LTX-ns). Thirteen patients died before transplantation (Fail). There was no difference between LTX-s and the 19 overall non-survivors (NS) prior to ECMO initiation with regard to demographic data or ventilator parameters except for higher PaO2 /FiO2 in the LTX-s. Time on ECMO pre-LTX did not differ in the LTX-s and LTX-ns groups. SOFA score was lower in LTX-s when compared to LTX-ns before ECMO (p = 0.0155), during bridging (p = 0.028), and right before transplantation (p = 0.0038). Maximal bilirubin during bridging and bilirubin prior to transplantation was markedly elevated in the LTX-ns group [4.2 (2.4-4.7) vs. 1.1 (0.8-2.0) mg/dL; p = 0.0266 and 1.6 (1.2-3.0) vs. 0.5 (0.5-0.5) mg/dL; p = 0.0047). Bridging to LTX is a challenging but viable option for selected patients. Special consideration should be given to hepatic function.

Lung transplantation

Lung transplantation may be the only intervention that can prolong survival and improve quality of life for those individuals with advanced lung disease who are acceptable candidates for the procedure. However, these candidates may be extremely ill and require ventilator and/or circulatory support as a bridge to transplantation, and lung transplantation recipients are at risk of numerous post-transplant complications that include surgical complications, primary graft dysfunction, acute rejection, opportunistic infection, and chronic lung allograft dysfunction (CLAD), which may be caused by chronic rejection. Many advances in pre- and post-transplant management have led to improved outcomes over the past decade. These include the creation of sound guidelines for candidate selection, improved surgical techniques, advances in donor lung preservation, an improving ability to suppress and treat allograft rejection, the development of prophylaxis protocols to decrease the incidence of opportunistic infection, more effective therapies for treating infectious complications, and the development of novel therapies to treat and manage CLAD. A major obstacle to prolonged survival beyond the early post-operative time period is the development of bronchiolitis obliterans syndrome (BOS), which is the most common form of CLAD. This manuscript discusses recent and evolving advances in the field of lung transplantation.