Bridge to lung transplantation with extracorporeal membrane oxygenation support:

A Descriptive Analysis of Hybrid Cannulated Extracorporeal Life Support

BACKGROUND

Extracorporeal life support (ECLS) is pivotal for sustaining the function of failing hearts and lungs, and its utilization has risen. In cases where conventional cannulation strategies prove ineffective for providing adequate ECLS support, the implementation of an enhanced system with a third cannula may become necessary. Hybrid ECLS may be warranted in situations characterized by severe hypoxemia of the upper extremity, left ventricular congestion, and dilatation. Additionally, it may also be considered for patients requiring respiratory support or experiencing hemodynamic instability.

METHOD

All hybrid ECLS cases of adults at the University Hospital Zurich, Switzerland, between January 2007 and December 2019 with initial triple cannulation were included. Data were collected via a retrospective review of patient records and direct export of the clinical information system.

RESULTS

28 out of 903 ECLS cases were initially hybrid cannulated (3.1%). The median age was 57 (48.2 to 60.8) years, and the sex was equally distributed. The in-hospital mortality of hybrid ECLS was high (67.9%). In-hospital mortality rates differ depending on the indication (ARDS: 36.4%, refractory cardiogenic shock: 88.9%, cardiopulmonary resuscitation: 100%, post-cardiotomy: 100%, others: 75%). Survivors exhibited a lower SAPS II level compared with non-survivors (20.0 (12.0 to 65.0) vs. 55.0 (45.0 to 73.0)), and the allogenic transfusion of platelet concentrate was observed to be less frequent for survivors (0.0 (0.0) vs. 1.8 (2.5) units).

CONCLUSION

The in-hospital mortality rate for hybrid ECLS was high. Different indications showed varying mortality rates, with survivors having lower SAPS II scores and requiring fewer platelet concentrate transfusions. These findings highlight the complexities of hybrid ECLS outcomes in different clinical scenarios and underline the importance of rigorous patient selection.

Enhanced extracorporeal carbon dioxide removal by acidification and metabolic control

BACKGROUND

Extracorporeal carbon dioxide removal (ECCO2R) promotes protective ventilation in patients with acute respiratory failure, but devices with high CO2 extraction capacity are required for clinically relevant impact. This study evaluates three novel low-flow techniques based on dialysate acidification, also combined with renal replacement therapy, and metabolic control.

METHODS

Eight swine were connected to a low-flow (350 mL/min) extracorporeal circuit including a dialyzer with a closed-loop dialysate circuit, and two membrane lungs on blood (MLb) and dialysate (MLd), respectively. The following 2-hour steps were performed: 1) MLb-start (MLb ventilated); 2) MLbd-start (MLb and MLd ventilated); 3) HLac (lactic acid infusion before MLd); 4) HCl-NaLac (hydrochloric acid infusion before MLd combined with renal replacement therapy and reinfusion of sodium lactate); 5) HCl-βHB-NaLac (hydrochloric acid infusion before MLd combined with renal replacement therapy and reinfusion of sodium lactate and sodium 3-hydroxybutyrate). Caloric and fluid inputs, temperature, blood glucose and arterial carbon dioxide pressure were kept constant.

RESULTS

The total MLs CO2 removal in HLac (130±25 mL/min), HCl-NaLac (130±21 mL/min) and HCl-βHB-NaLac (124±18 mL/min) were higher compared with MLbd-start (81±15 mL/min, P<0.05) and MLb-start (55±7 mL/min, P<0.05). Minute ventilation in HLac (4.3±0.9 L/min), HCl-NaLac (3.6±0.8 L/min) and HCl-βHB-NaLac (3.6±0.8 L/min) were lower compared to MLb-start (6.2±1.1 L/min, P<0.05) and MLbd-start (5.8±2.1 L/min, P<0.05). Arterial pH was 7.40±0.03 at MLb-start and decreased only during HCl-βHB-NaLac (7.35±0.03, P<0.05). No relevant changes in electrolyte concentrations, hemodynamics and significant adverse events were detected.

CONCLUSIONS

The three techniques achieved a significant extracorporeal CO2 removal allowing a relevant reduction in minute ventilation with a sufficient safety profile.

Complications related to extracorporeal membrane oxygenation support as a bridge to lung transplantation and their clinical significance

BACKGROUND

Incidence of complications related extracorporeal membrane oxygenation (ECMO) support as a bridge to lung transplantation (BTT) and its association with the patient outcome in lung transplantation (LT) has not been well documented in previous studies.

OBJECTIVES

We evaluated the incidence of complications related to the use of ECMO support as a BTT, and the association between the occurrence of the complications and patient outcomes in LTs.

METHODS

This retrospective cohort study investigated 100 consecutive patients who started ECMO support as a BTT between April 2013 and March 2020. Data for the analyses were retrieved from electronic medical records.

RESULTS

Fifty-six percent of the patients experienced at least one complication during the BTT with ECMO. Major bleeding was the most common complication. In multivariate logistic regression analysis, occurrence of oxygenator thromboses (OR 16.438, P = 0.008) and the use of renal replacement therapy (RRT) (OR 32.288, P < 0.001) were associated with a failed BTT. In the subgroup analysis of the LT recipients, intracranial hemorrhages, (OR 13.825, P = 0.021), RRT use, (OR 11.395, P = 0.038), and bloodstream infection occurrence (OR 6.210; P = 0.034) were identified as risk factors for in-hospital mortality.

CONCLUSIONS

The occurrence of complications during the use of ECMO support as a BTT was associated with unfavorable outcomes in LTs. Close monitoring and the proper management of these complications may be important to achieve better outcomes in patients using ECMO support as a BTT.

Case report: atrial septostomy as a bridge to lung transplantation in a patient with venovenous extracorporeal membrane oxygenation

INTRODUCTION

Advances in critical care management have led to the recent increase in the use of extracorporeal membrane oxygenation (ECMO) as a bridge to lung transplantation (LT). Patients with respiratory failure requiring venovenous ECMO usually experience progressive right ventricular (RV) failure. Diagnosis and treatment of RV failure during ECMO are essential for improving the prognosis of patients.

PATIENT CONCERNS

A 28-year-old female patient underwent allogeneic hematopoietic stem cell transplantation (HSCT) from a matched unrelated donor for acute myeloid leukemia presenting with progressive dyspnea.

DIAGNOSES

Computed tomography revealed multifocal patchy peribronchial and subpleural ground-glass opacities in both lungs, and the patient was clinically diagnosed with cryptogenic organizing pneumonia.

INTERVENTIONS AND OUTCOMES

Despite intensifying systemic corticosteroid therapy, her symptoms deteriorated, and mechanical ventilation and ECMO were applied. During treatment, her respiratory failure continued to progress, and systemic hypotension developed. An echocardiogram showed evidence of RV failure, and percutaneous atrial septostomy was performed for RV decompression. After a balloon atrial septostomy was performed, RV failure of the patient improved, and LT was successfully performed.

LESSONS

We report the first case of atrial septostomy as a successful bridge to LT in a HSCT recipient with venovenous ECMO. Atrial septostomy could be an option for management of RV failure during ECMO. Further studies need to be conducted to validate the effect of atrial septostomy in patients with RV failure during ECMO.

Transesophageal Echocardiography Compared to Fluoroscopy for Avalon Bicaval Dual-Lumen Cannula Positioning for Venovenous ECMO

The Avalon elite bicaval dual-lumen cannula for single site VenoVenous Extracorporeal Membrane Oxygenation (VV ECMO) offers several advantages. Correct placement of the Avalon cannula is safe using image guidance and needs either fluoroscopy or Transesophageal echocardiography (TEE). We assessed our institutional ECMO performance, cannulation related complications, instances of cannula malposition among patients cannulated using the two imaging modalities. We reviewed all patients who had Avalon cannula placement for VV ECMO at our institute. Ten patients were included in the study. Patients were cannulated using either fluoroscopy (Group A, n = 5) or TEE (Group B, n = 5). Data included patient demographics, diagnosis, evidence of cannula malposition, ECMO performance, cannulation related complications. The primary outcomes ease of cannulation; cannula malposition and the need for repositioning were compared between the two groups. Visualisation of guidewire, Avalon cannula and the average number of attempts to cannulate were similar (P > 0.05) between the two groups. Four patients cannulated using fluoroscopy had low flows whereas none of the patients cannulated using TEE had flow problems which was statistically significant (P = 0.024). Four cannulas (80%) placed under fluoroscopy required repositioning whereas one cannula (20%) placed under TEE needed repositioning. This difference was not statistically significant though (P = 0.099). TEE is the ideal imaging modality to guide Avalon elite cannula placement for VV ECMO.

The Cellular and Physiological Basis for Lung Repair and Regeneration: Past, Present, and Future

The respiratory system, which includes the trachea, airways, and distal alveoli, is a complex multi-cellular organ that intimately links with the cardiovascular system to accomplish gas exchange. In this review and as members of the NIH/NHLBI-supported Progenitor Cell Translational Consortium, we discuss key aspects of lung repair and regeneration. We focus on the cellular compositions within functional niches, cell-cell signaling in homeostatic health, the responses to injury, and new methods to study lung repair and regeneration. We also provide future directions for an improved understanding of the cell biology of the respiratory system, as well as new therapeutic avenues.

Practices in Triage and Transfer of Critically Ill Patients: A Qualitative Systematic Review of Selection Criteria

OBJECTIVES

To identify and appraise articles describing criteria used to prioritize or withhold a critical care admission.

DATA SOURCES

PubMed, Embase, Medline, EBM Reviews, and CINAHL Complete databases. Gray literature searches and a manual review of references were also performed. Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines were followed.

STUDY SELECTION

We sought all articles and abstracts of original research as well as local, provincial, or national policies on the topic of ICU resource allocation. We excluded studies whose population of interest was neonatal, pediatric, trauma, or noncritically ill. Screening of 6,633 citations was conducted.

DATA EXTRACTION

Triage and/or transport criteria were extracted, based on type of article, methodology, publication year, and country. An appraisal scale was developed to assess the quality of identified articles. We also developed a robustness score to further appraise the robustness of the evidence supporting each criterion. Finally, all criteria were extracted, evaluated, and grouped by theme.

DATA SYNTHESIS

One-hundred twenty-nine articles were included. These were mainly original research (34%), guidelines (26%), and reviews (21%). Among them, we identified 200 unique triage and transport criteria. Most articles highlighted an exclusion (71%) rather than a prioritization mechanism (17%). Very few articles pertained to transport of critically ill patients (4%). Criteria were classified in one of four emerging themes: patient, condition, physician, and context. The majority of criteria used were nonspecific. No study prospectively evaluated the implementation of its cited criteria.

CONCLUSIONS

This systematic review identified 200 criteria classified within four themes that may be included when devising triage programs including the coronavirus disease 2019 pandemic. We identified significant knowledge gaps where research would assist in improving existing triage criteria and guidelines, aiming to decrease arbitrary decisions and variability.

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.

Extracorporeal membrane oxygenation as a bridge to lung transplantation: analysis of Korean organ transplantation registry (KOTRY) data

BACKGROUND

The use of extracorporeal membrane oxygenation (ECMO) as a bridge to lung transplantation has greatly increased. However, data regarding the clinical outcomes of this approach are lacking. The objective of this multicenter prospective observational cohort study was to evaluate lung transplantation outcomes in Korean Organ Transplantation Registry (KOTRY) patients for whom ECMO was used as a bridge to transplantation.

METHODS

Between March 2015 and December 2017, a total of 112 patients received lung transplantation and were registered in the KOTRY, which is a prospective, multicenter cohort registry. The entire cohort was divided into two groups: the control group (n = 85, 75.9%) and bridge-ECMO group (n = 27, 24.1%).

RESULTS

There were no significant differences in pre-transplant and intraoperative characteristics except for poorer oxygenation, more ventilator use, and longer operation time in the bridge-ECMO group. The prevalence of primary graft dysfunction at 0, 24, 48, and 72 h after transplantation did not differ between the two groups. Although postoperative hospital stays were longer in the bridge-ECMO group than in the control group, hospital mortality did not differ between the two groups (25.9% vs. 13.3%, P = 0.212). The majority of patients (70.4% of the bridge-ECMO group and 77.6% of the control group) were discharged directly to their homes. Finally, the use of ECMO as a bridge to lung transplantation did not significantly affect overall survival and graft function.

CONCLUSIONS

Short- and long-term post-transplant outcomes of bridge-ECMO patients were comparable to recipients who did not receive ECMO.

Extracorporeal Life Support in Adult Patients: A Global Perspective of the Last Decade

Extracorporeal life support (ECLS) is an external medical device to treat critically ill patients with cardiovascular and respiratory failure. In a nutshell, ECLS is only a "bridging" mechanism that provides life support while the heart and/or the lungs is recovering either by therapeutic medical interventions, transplantation, or spontaneously. Extracorporeal life support has been developed since 1950s, and many studies were conducted to improve ECLS techniques, but unfortunately, the survival rate was not improved. Because of Dr Bartlett's success in using ECLS to treat neonates with severe respiratory distress in 1975, ECLS is made as a standard lifesaving therapy for neonates with severe respiratory distress. However, its use for adult patients remains debatable. The objectives of this study are to outline and provide a general overview of the use of ECLS especially for adult patients for the past 10 years and to elaborate on the challenges encountered by each stakeholder involved in ECLS. The data used for this study were extracted from the ELSO Registry Report of January 2018. Results of this study revealed that the number of ECLS centers and the use of ECLS are increasing over the year for the past decade. There was also a shift of the patient's age category from neonatal to adult patients. However, the survival rates for adult patients are relatively low especially for cardiac and extracorporeal cardiopulmonary resuscitation cases. To date, the complications are still the major challenge of ECLS. Other challenges encountered by the stakeholders in ECLS are the limited amount of well-trained and experienced ECLS teams and centers, the limited government expenditure on health, and the lack of improvement and development of ECLS techniques and devices. Further studies are needed to evaluate the value of ECLS for adult patients.

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.

Bridging to Lung Transplantation

Lung transplantation is the gold standard for treating patients with end-stage lung disease. Such patients can present with severe illness on the waitlist and may deteriorate before a lung donor is available. Bridging strategies with extracorporeal membrane oxygenation (ECMO) are valuable for getting patients to transplant and provide a chance at survival. The current article describes the indications, contraindications, and techniques involved in bridging to lung transplantation with ECMO.

Pressure ulcers in paediatric patients on extracorporeal membrane oxygenation

It has been shown that pressure ulcer formation in critically ill paediatric patients increases morbidity and mortality. We sought to identify factors associated with pressure ulcer formation in paediatric patients on extracorporeal membrane oxygenation (ECMO). From December 2014 to 2015, we identified patients at our institution who developed a pressure ulcer to create two cohorts: ulcer and no ulcer. Variables of interest included: type of ECMO, ECMO indication, hours on ECMO, location of cannulas, volume of crystalloid and blood products received during the first 7 days or during the length of the ECMO run, albumin and lactate levels on the day of cannulation, and presence of vasopressor support or steroid therapy. Of 43 patients studied, 11 (25.5%) developed a pressure ulcer. Patients that developed ulcers were older (P = 0.001) and weighed more (P = 0.006). Femoral cannulation was more frequent in the ulcer group (36.4% vs 6.3%, P = 0.029), and duration of ECMO was longer (P = 0.007). Age, weight, duration of ECMO, and femoral cannulation may contribute to the development of pressure ulcers in children who require ECMO support. Further analysis is imperative to identify specific techniques and protocols that will prevent pressure ulcers in this critically ill population.

Early initiation of venovenous extracorporeal membrane oxygenation in a mechanically ventilated patient with severe acute respiratory distress syndrome

A 49-year-old man presented to the emergency department with acute-onset dyspnoea and hypoxaemia 1 day following nasal surgery for obstructive sleep apnoea. A chest X-ray showed diffuse bilateral pulmonary infiltrates. Supplemental 100% fractional inspired oxygen (FiO2) via non-rebreather mask was delivered with resulting arterial oxygen tension:FiO2 ratio of 67. Transthoracic echocardiogram demonstrated normal heart function. A clinical diagnosis of severe acute respiratory distress syndrome (ARDS) was promptly made. Based on patient preference to avoid intubation and following a multidisciplinary approach, we decided to initiate venovenous extracorporeal membrane oxygenation (VV-ECMO) as an alternative strategy to mechanical ventilation. Though he ultimately required brief mechanical ventilation during ECMO cannulation, the patient spent a total of 5 days on VV-ECMO and a total of 8 days in the intensive care unit. Six days after discharge, his pulmonary function test demonstrated no significant abnormalities. We present a rare case of early initiation of VV-ECMO in a patient with severe ARDS that served as a bridge to recovery.

Mechanical ventilation and respiratory monitoring during extracorporeal membrane oxygenation for respiratory support

Over the past decade, the use of veno-venous extracorporeal membrane oxygenation (VV-ECMO) for respiratory support has widely expanded as a treatment strategy for patients with acute respiratory distress syndrome (ARDS). Despite considerable attention has been given to the indications, the timing and the management of patients undergoing ECMO for refractory respiratory hypoxemic failure, little is known regarding the management of mechanical ventilation (MV) in this group of patients. ECMO enables to minimize ventilatory induced lung injury (VILI) and it has been successfully used as rescue therapy in patients with ARDS when conventional ventilator strategies have failed. However, literature is lacking regarding the best strategies and MV settings, including positive end expiratory pressure (PEEP), tidal volume (VT), respiratory rate (RR) and plateau pressure (PPLAT). The aim of this review is to summarize current evidence, the rationale and provide recommendations about the best ventilator strategy to adopt in patients with ARDS undergoing VV-ECMO support.

Echocardiography in extracorporeal life support: A key player in procedural guidance, tailoring and monitoring

Extracorporeal life support (ECLS) is a mainstay of current practice in severe respiratory, circulatory or cardiac failure refractory to conventional management. The inherent complexity of different ECLS modes and their influence on the native pulmonary and cardiovascular system require patient-specific tailoring to optimize outcome. Echocardiography plays a key role throughout the ECLS care, including patient selection, adequate placement of cannulas, monitoring, weaning and follow-up after decannulation. For this purpose, echocardiographers require specific ECLS-related knowledge and skills, which are outlined here.

Extracorporeal Circulation During Lung Transplantation Procedures: A Meta-Analysis

Extracorporeal circulation (ECC) is an invaluable tool in lung transplantation (lutx). More than the past years, an increasing number of centers changed their standard for intraoperative ECC from cardiopulmonary bypass (CPB) to extracorporeal membrane oxygenation (ECMO) - with differing results. This meta-analysis reviews the existing evidence. An online literature research on Medline, Embase, and PubMed has been performed. Two persons independently judged the papers using the ACROBAT-NRSI tool of the Cochrane collaboration. Meta-analyses and meta-regressions were used to determine whether veno-arterial ECMO (VA-ECMO) resulted in better outcomes compared with CPB. Six papers - all observational studies without randomization - were included in the analysis. All were considered to have serious bias caused by heparinization as co-intervention. Forest plots showed a beneficial trend of ECMO regarding blood transfusions (packed red blood cells (RBCs) with an average mean difference of -0.46 units [95% CI = -3.72, 2.80], fresh-frozen plasma with an average mean difference of -0.65 units [95% CI = -1.56, 0.25], platelets with an average mean difference of -1.72 units [95% CI = -3.67, 0.23]). Duration of ventilator support with an average mean difference of -2.86 days [95% CI = -11.43, 5.71] and intensive care unit (ICU) length of stay with an average mean difference of -4.79 days [95% CI = -8.17, -1.41] were shorter in ECMO patients. Extracorporeal membrane oxygenation treatment tended to be superior regarding 3 month mortality (odds ratio = 0.46, 95% CI = 0.21-1.02) and 1 year mortality (odds ratio = 0.65, 95% CI = 0.37-1.13). However, only the ICU length of stay reached statistical significance. Meta-regression analyses showed that heterogeneity across studies (sex, year of ECMO implementation, and underlying disease) influenced differences. These data indicate a benefit of the intraoperative use of ECMO as compared with CPB during lung transplant procedures regarding short-term outcome (ICU stay). There was no statistically significant effect regarding blood transfusion needs or long-term outcome. The superiority of ECMO in lutx patients remains to be determined in larger multi-center randomized trials.

Principi e indicazioni dell’assistenza circolatoria e respiratoria extracorporea in chirurgia toracica

In origine, l’extracorporeal membrane oxygenation (ECMO) era una tecnica di assistenza respiratoria che utilizzava uno scambiatore gassoso a membrana. Per estensione, l’ECMO è diventata una tecnica respiratoria e cardiopolmonare utilizzata in caso di deficit respiratorio e/o cardiaco nell’attesa della restaurazione della funzione deficitaria o di un eventuale trapianto. Il supporto emodinamico può essere parziale o totale. Gli accessi vascolari possono essere periferici o centrali. Questo tipo di assistenza utilizza il concetto di circolazione extracorporea (CEC) sanguigna che in epoca moderna si è estesa con l’utilizzo di polmoni artificiali a membrana. Il circuito di base è semplice e comprende una pompa, un ossigenatore (che permette al sangue di caricarsi di O₂ e di eliminare CO₂) e delle vie d’accesso (una di drenaggio e una di reinfusione). La sua attuazione è facile, veloce e può essere avviata al letto del malato. Il miglioramento delle attrezzature, una migliore conoscenza delle tecniche e delle indicazioni, e le politiche di salute pubblica hanno reso popolare questa tecnica. Alcuni centri di chirurgia toracica la utilizzano di routine come assistenza alla realizzazione di un intervento terapeutico (soprattutto trapianto) assieme a team di rianimazione per il trattamento della sindrome da distress respiratorio acuto. Nel quadro della malattia polmonare dell’adulto, l’idea principale è quella di sviluppare il concetto di strategia minimalista con l’uso di una CEC adiuvante parziale – più che sostitutiva totale – che permetterebbe il recupero metabolico ad integrum del paziente. Nei prossimi anni, i progressi della tecnologia e dell’ingegneria così come le conoscenze approfondite permetteranno il miglioramento della prognosi dei pazienti colpiti da deficit respiratorio sotto assistenza meccanica.

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.

Back to the roots? Dual cannulation strategy for ambulatory ECMO in adolescent lung transplant candidates: An alternative?

Bridging critically ill pediatric patients to lung transplantation still remains a major challenge. Although still controversial, within the last 5 years, ECMO has been increasingly used as a bridge to lung transplantation concept in adult and pediatric patients with acceptable outcomes. The outstanding developments in the field of extracorporeal devices and the introduction of awake ECMO concepts with the avoidance of mechanical ventilation have led to a real paradigm shift in the ICU management of pretransplant candidates with severe respiratory failure. Therefore, ECMO is no longer seen as a contraindication for lung transplantation at least at our center. Nevertheless, how to bridge these patients on ECMO still remains controversial. Thus, we introduced an ambulatory ECMO approach in adolescent lung transplant candidates with acute respiratory failure using a dual cannulation strategy and hereby present first results from this procedure.

[Extracorporeal life support in thoracic surgery: What are the indications and the pertinence?]

INTRODUCTION

In thoracic surgery, extracorporeal life support (ECLS) technologies are used in cases of severe and refractory respiratory failure or as intraoperative cardiorespiratory support. The objectives of this review are to describe the rationale of ECLS techniques, to review the pulmonary diseases potentially treated by ECLS, and finally to demonstrate the efficacy of ECLS, using recently published data from the literature, in order to practice evidence based medicine.

STATE OF THE ART

ECLS technologies should only be undertaken in expert centers. ECLS allows a protective ventilatory strategy in severe ARDS. In the field of lung transplantation, ECLS may be used successfully as a bridge to transplantation, as intraoperative cardiorespiratory support or as a bridge to recovery in cases of severe primary graft dysfunction. In general thoracic surgery, ECLS technology seems to be safe and efficient as intraoperative respiratory support for tracheobronchial surgery or for severe respiratory insufficiency, without significant increase in perioperative risk.

PERSPECTIVE

The indications for ECLS are going to increase. Future improvements both in scientific knowledge and bioengineering will improve the prognosis of patients treated with ECLS for respiratory failure. Multicenter randomized controlled trials will refine the indications for ECLS and improve the global care strategies for these patients.

CONCLUSION

ECLS is an efficient therapeutic strategy that will improve the prognosis of patients suffering from, or exposed to, the risks of severe respiratory failure.

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.

Principi e indicazioni dell’assistenza circolatoria e respiratoria extracorporea in chirurgia toracica

In origine, l’extracorporeal membrane oxygenation (ECMO) era una tecnica di assistenza respiratoria che utilizzava uno scambiatore gassoso a membrana. Per estensione, l’ECMO è diventata una tecnica respiratoria e cardiopolmonare utilizzata in caso di deficit respiratorio e/o cardiaco nell’attesa della restaurazione della funzione deficitaria o di un eventuale trapianto. Il supporto emodinamico può essere parziale o totale. Gli accessi vascolari possono essere periferici o centrali. Questo tipo di assistenza utilizza il concetto di circolazione extracorporea (CEC) sanguigna che in epoca moderna si è estesa con l’utilizzo di polmoni artificiali a membrana. Il circuito di base è semplice e comprende una pompa, un ossigenatore (che permette al sangue di caricarsi di O₂ e di eliminare CO₂) e delle vie d’accesso (una di drenaggio e una di reinfusione). La sua attuazione è facile, veloce e può essere avviata al letto del malato. Il miglioramento delle attrezzature, una migliore conoscenza delle tecniche e delle indicazioni, e le politiche di salute pubblica hanno reso popolare questa tecnica. Alcuni centri di chirurgia toracica la utilizzano di routine come assistenza alla realizzazione di un intervento terapeutico (soprattutto trapianto) assieme a team di rianimazione per il trattamento della sindrome da distress respiratorio acuto. Nel quadro della malattia polmonare dell’adulto, l’idea principale è quella di sviluppare il concetto di strategia minimalista con l’uso di una CEC adiuvante parziale – più che sostitutiva totale – che permetterebbe il recupero metabolico ad integrum del paziente. Nei prossimi anni, i progressi della tecnologia e dell’ingegneria così come le conoscenze approfondite permetteranno il miglioramento della prognosi dei pazienti colpiti da deficit respiratorio sotto assistenza meccanica.

Successful Lung Transplant After Prolonged Extracorporeal Membrane Oxygenation (ECMO) in a Child With Pulmonary Hypertension: A Case Report

INTRODUCTION

The use of extracorporeal membrane oxygenation (ECMO) is considered a risk factor for, or even a potential contraindication to, lung transplantation. However, only a few pediatric cases have been described thus far.

CASE PRESENTATION

A 9-year-old boy with idiopathic pulmonary arterial hypertension developed cardiac arrest after the insertion of a central catheter. ECMO was used as a bridge to lung transplantation. However, after prolonged resuscitation, he developed medullary ischemia and medullary syndrome. After 6 weeks of ECMO and triple combination therapy for pulmonary hypertension, including continuous intravenous prostacyclin, he was weaned off support, and after 2 weeks, bilateral lung transplantation was performed. At 4 years post-transplant, he has minimal problems. The medullary syndrome has also alleviated. He is now back to school and can walk with aids.

CONCLUSIONS

Increasing evidence supports the use of ECMO as a bridge to LT, reporting good outcomes. In the modern era of PAH therapy, it is feasible to use prolonged ECMO support as a bridge to lung transplant, with the aim of weaning off this support; however, its use requires more experience and knowledge of long-term outcomes.

Prolonged Use of the Hemolung Respiratory Assist System as a Bridge to Redo Lung Transplantation

Although extracorporeal membrane oxygenation (ECMO) has been used frequently as a bridge to primary lung transplantation, active centers are conservative with this approach in patients requiring redo lung transplantation. We report the use of extracorporeal carbon dioxide removal, using the Hemolung respiratory assist system, as a prolonged bridge to lung transplantation, and the first use of the Hemolung as a bridge to redo lung transplantation. Hemolung support improved the patient's clinical status and allowed redo lung transplantation.

Extracorporeal membrane oxygenation: a breakthrough for respiratory failure

Extracorporeal membrane oxygenation (ECMO) is a method for providing long-term treatment of a patient in a modified heart-lung machine. Desaturated blood is drained from the patient, oxygenated and pumped back to a major vein or artery. ECMO supports heart and lung function and may be used in severe heart and/or lung failure when conventional intensive care fails. The Stockholm programme started in 1987 with treatment of neonates. In 1995, the first adult patient was accepted onto the programme. Interhospital transportation during ECMO was started in 1996, which enabled retrieval of extremely unstable patients during ECMO. Today, the programme has an annual volume of about 80 patients. It has been characterized by, amongst other things, minimal patient sedation. By 31 December 2014, over 900 patients had been treated, the vast majority for respiratory failure, and over 650 patients had been transported during ECMO. The median ECMO duration was 5.3, 5.7 and 7.1 days for neonatal, paediatric and adult patients, respectively. The survival to hospital discharge rate for respiratory ECMO was 81%, 70% and 63% in the different age groups, respectively, which is significantly higher than the overall international experience as reported to the Extracorporeal Life Support Organization (ELSO) Registry (74%, 57% and 57%, respectively). The survival rate was significantly higher in the Stockholm programme compared to ELSO for meconium aspiration syndrome, congenital diaphragmatic hernia in neonates and pneumocystis pneumonia in paediatric patients.

Severe pulmonary arterial hypertension: treatment options and the bridge to transplantation

Pulmonary arterial hypertension (PAH) is a rare disease leading to right heart failure and death. Prognosis remains poor, particularly for patients with severe disease, i.e. World Health Organization functional class IV. There have been significant improvements in treatment options. Several agents are available that target the three main established PAH disease pathways, and can be combined sequentially or upfront. Strong scientific evidence supports the use of intravenous epoprostenol in severe PAH; however, despite recommendations, many patients do not receive parenteral prostanoids and there is a lack of evidence from randomised clinical trials supporting the value of other PAH medications alone in severe PAH. Lung transplantation is an important option in patients with severe PAH who have not responded sufficiently to therapy, or who have worsened despite maximal treatment. Bridging techniques are available for patients who worsen while awaiting transplantation. The type of bridging technique used depends on various factors including patient illness severity, physician experience and the anticipated waiting time for transplantation. With the aim to facilitate the treatment decision-making process, herein we review the medical treatment options available for patients with severe PAH, and the bridging techniques that may be used to sustain patients awaiting transplantation.

Extracorporeal life support for adult cardiopulmonary failure

The use of extracorporeal life support (ECLS) or extracorporeal membrane oxygenation (ECMO), as it is also known, has rapidly expanded over the past decade. The increase in ECMO use is a consequence of multiple factors including significant advancements in extracorporeal technology, the emergence of data supporting its use, and a growing number of potential clinical applications. This review focuses on the various modes of ECLS as well as the clinical indications and available evidence for the use of extracorporeal support.

Extracorporeal life support: updates and controversies

The use of Extracorporeal Life Support (ECLS) in children and adults has markedly increased during the past few years with over 4000 patients placed on ECLS every year in over 200 centers. This article focuses on updates to the physiology and mechanics of ECLS with use of magnetically levitated centrifugal pumps, hollow-fiber gas-exchange devices, and bi-caval dual-lumen catheters. We also explore controversies in management including indications, cannulation approaches, renal replacement, monitoring of anticoagulation, early ambulation, and termination of ECLS. Finally, we present changes in the systems that provide ECLS including the single-provider model and regionalization of care.

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.

Modular extracorporeal life support: effects of ultrafiltrate recirculation on the performance of an extracorporeal carbon dioxide removal device

The combination of extracorporeal carbon dioxide removal (ECCO2R) and hemofiltration is a possible therapeutic strategy for patients needing both lung and renal support. We tested the effects of the recirculation of ultrafiltrate on membrane lung (ML) CO2 removal (VCO2ML). Three conscious, spontaneously breathing sheep were connected to a commercially produced ECCO2R device (Hemolung; Alung Technologies, Pittsburgh, PA) with a blood flow of 250 ml/min and a gas flow of 10 L/min. A hemofilter (NxStage, NxStage Medical, Lawrence, MA) was interposed in series after the ML. Ultrafiltrate flow was generated and recirculated before the ML. We tested four ultrafiltrate flows (0, 50, 100, and 150 ml/min) for 25 min each, eight times per animal, resulting in 24 randomized test repetitions. We recorded VCO2ML, hemodynamics and ventilatory variables, and natural lung CO2 transfer (VCO2NL) and collected arterial and circuitry blood samples. VCO2ML was unchanged by application of ultrafiltrate recirculation (40.5 ± 4.0, 39.7 ± 4.2, 39.8 ± 4.2, and 39.2 ± 4.1 ml/min, respectively, at ultrafiltrate flow of 0, 50, 100, and 150 ml/min). Minute ventilation, respiratory rate, VCO2NL, and arterial blood analyses were not affected by ultrafiltrate recirculation. In the tested configuration, ultrafiltrate recirculation did not affect VCO2ML. This modular technology may provide a suitable platform for coupling CO2 removal with various forms of blood purification.

Emerging indications for extracorporeal membrane oxygenation in adults with respiratory failure

Recent advances in technology have spurred the increasing use of extracorporeal membrane oxygenation (ECMO) in patients with severe hypoxemic respiratory failure. However, this accounts for only a small percentage of patients with respiratory failure. We envision the application of ECMO in many other forms of respiratory failure in the coming years. Patients with less severe forms of acute respiratory distress syndrome, for instance, may benefit from enhanced lung-protective ventilation with the very low tidal volumes made possible by direct carbon dioxide removal from the blood. For those in whom hypercapnia predominates, extracorporeal support will allow for the elimination of invasive mechanical ventilation in some cases. The potential benefits of ECMO may be further enhanced by improved techniques, which facilitate active mobilization. Although ECMO for these and other expanded applications is under active investigation, it has yet to be proven beneficial in these settings in rigorous controlled trials. Ultimately, with upcoming and future technological advances, there is the promise of true destination therapy, which could lead to a major paradigm shift in the management of respiratory failure.

Regional blood acidification enhances extracorporeal carbon dioxide removal: a 48-hour animal study

BACKGROUND

Extracorporeal carbon dioxide removal has been proposed to achieve protective ventilation in patients at risk for ventilator-induced lung injury. In an acute study, the authors previously described an extracorporeal carbon dioxide removal technique enhanced by regional extracorporeal blood acidification. The current study evaluates efficacy and feasibility of such technology applied for 48 h.

METHODS

Ten pigs were connected to a low-flow veno-venous extracorporeal circuit (blood flow rate, 0.25 l/min) including a membrane lung. Blood acidification was achieved in eight pigs by continuous infusion of 2.5 mEq/min of lactic acid at the membrane lung inlet. The acid infusion was interrupted for 1 h at the 24 and 48 h. Two control pigs did not receive acidification. At baseline and every 8 h thereafter, the authors measured blood lactate, gases, chemistry, and the amount of carbon dioxide removed by the membrane lung (VCO2ML). The authors also measured erythrocyte metabolites and selected cytokines. Histological and metalloproteinases analyses were performed on selected organs.

RESULTS

Blood acidification consistently increased VCO2ML by 62 to 78%, from 79 ± 13 to 128 ± 22 ml/min at baseline, from 60 ± 8 to 101 ± 16 ml/min at 24 h, and from 54 ± 6 to 96 ± 16 ml/min at 48 h. During regional acidification, arterial pH decreased slightly (average reduction, 0.04), whereas arterial lactate remained lower than 4 mEq/l. No sign of organ and erythrocyte damage was recorded.

CONCLUSION

Infusion of lactic acid at the membrane lung inlet consistently increased VCO2ML providing a safe removal of carbon dioxide from only 250 ml/min extracorporeal blood flow in amounts equivalent to 50% production of an adult man.

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.

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.