Extracorporeal life support in the management of severe respiratory failure

Extracorporeal membrane oxygenation for critically ill adults

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) may provide benefit in certain populations of adults, including those with severe cardiac failure, severe respiratory failure, and cardiac arrest. However, it is also associated with serious short- and long-term complications, and there remains a lack of high-quality evidence to guide practice. Recently several large randomized controlled trials (RCTs) have been published, therefore, we undertook an update of our previous systematic review published in 2014.

OBJECTIVES

To evaluate whether venovenous (VV), venoarterial (VA), or ECMO cardiopulmonary resuscitation (ECPR) improve mortality compared to conventional cardiopulmonary support in critically ill adults.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was March 2022. The search was limited to English language only.

SELECTION CRITERIA

We included RCTs, quasi-RCTs, and cluster-RCTs that compared VV ECMO, VA ECMO or ECPR to conventional support in critically ill adults.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcome was 1. all-cause mortality at day 90 to one year. Our secondary outcomes were 2. length of hospital stay, 3. survival to discharge, 4. disability, 5. adverse outcomes/safety events, 6. health-related quality of life, 7. longer-term health status, and 8. cost-effectiveness. We used GRADE to assess certainty of evidence.

MAIN RESULTS

Five RCTs met our inclusion criteria, with four new studies being added to the original review (total 757 participants). Two studies were of VV ECMO (429 participants), one VA ECMO (41 participants), and two ECPR (285 participants). Four RCTs had a low risk of bias and one was unclear, and the overall certainty of the results (GRADE score) was moderate, reduced primarily due to indirectness of the study populations and interventions. ECMO was associated with a reduction in 90-day to one-year mortality compared to conventional treatment (risk ratio [RR] 0.80, 95% confidence interval [CI] 0.70 to 0.92; P = 0.002, I2 = 11%). This finding remained stable after performing a sensitivity analysis by removing the single trial with an uncertain risk of bias. Subgroup analyses did not reveal a significant subgroup effect across VV, VA, or ECPR modes (P = 0.73). Four studies reported an increased risk of major hemorrhage with ECMO (RR 3.32, 95% CI 1.90 to 5.82; P < 0.001), while two studies reported no difference in favorable neurologic outcome (RR 2.83, 95% CI 0.36 to 22.42; P = 0.32). Other secondary outcomes were not consistently reported across the studies.

AUTHORS' CONCLUSIONS

In this updated systematic review, which included four additional RCTs, we found that ECMO was associated with a reduction in day-90 to one-year all-cause mortality, as well as three times increased risk of bleeding. However, the certainty of this result was only low to moderate, limited by a low number of small trials, clinical heterogeneity, and indirectness across studies.

Developing a new pediatric extracorporeal membrane oxygenation (ECMO) program

OBJECTIVES

We aimed to critically evaluate the effectiveness of a designated ECMO team in our ECMO selection process and patient outcomes in the first 3 years of our low-volume pediatric ECMO program.

METHODS

We conducted a retrospective chart review of patients who received an ECMO consultation between the start of our program in March 2015 and May 2018. We gathered clinical and demographic information on patients who did and did not receive ECMO, and described our selection process. We reflected on the processes used to initiate our program and our outcomes in the first 3 years.

RESULTS

69 patients received consultations, and of those, 50 patients were potential candidates. 19 (38%) of the candidates were ultimately placed on ECMO. There were statistically significant differences in oxygen saturation, paO₂, oxygenation index, A-aDO₂, lactate, and pH between the patients who went on ECMO and who did not. We improved our outcomes from 0% survival to discharge in 2015, to 60% in 2018, with an average of 63% survival to discharge over the first 3 years of our program.

CONCLUSIONS

In a low-volume pediatric ECMO center, having a designated team to assist in the patient selection process and management can help provide safe and efficient care to these patients, and improve patient outcomes. Having a strict management protocol and simulation sessions involving all members of the medical team yields comfort for the providers and optimal care for patients. This study describes our novel structure, processes, and outcomes, which we hope will be helpful to others seeking to develop a new pediatric ECMO program.

Percutaneous Vascular Cannulation for Extracorporeal Life Support (ECLS): A Modified Technique

Purpose

Vascular access and cannulation are crucial issues to maximize the efficiency of extracorporeal circulation techniques and to preserve patients' safety. Techniques of cannulation have changed over the years, from surgical cutdown to percutaneous approaches, which are now considered standard practice. We describe an original modified percutaneous cannulation technique developed in our Department and we report our clinical experience and complications observed.

Methods

A Seldinger technique utilizing 3 guidewires with passage of a dilator over each guidewire was used. Two concentric pursestring sutures, prepared before cannulation, minimize procedure-associated bleeding. Cannulation is performed under direct fluoroscopic control.

Results

From 1997 to 2009, 38 patients (31 VV-ECLS, 7 VA-ECLS) have been cannulated using our technique, resulting in a total of 69 venous cannulations. Average external caliber of venous cannulae was 23 Fr (15–29 Fr). Mean duration of the entire cannulation procedure was 40 minutes (20–60 min). Adverse events occurred in 3 patients.

Conclusions

The technique described is safe and feasible and the incidence of procedure-related complications is very low, but it may require longer time to be performed.

An international survey: the role of specialist nurses in adult respiratory extracorporeal membrane oxygenation

BACKGROUND

The last decade has seen an increase in the number of centres able to provide venovenous extracorporeal membrane oxygenation (VV-ECMO) internationally across different health care systems. To support this growth, a variety of staffing arrangements have been adopted depending on local need and availability of resources, both in terms of manpower and finances to safely meet the complex needs of the patient and circuit management.

AIM

The aim of the survey was to describe current staffing arrangements of care provision for adult patients on VV-ECMO, with a focus on understanding the professional roles and responsibilities of staff managing the circuit in order to inform further discussion around different approaches to staffing.

METHODS

We conducted a cross-sectional international survey using an electronic questionnaire emailed to 177 worldwide ECMO centres treating adult patients with acute respiratory failure. The survey questions were generated through an internal and external iterative process and assessed for clarity, content and face validity.

RESULTS

The response rate was 82%. Respondents managed extracorporeal oxygenation for adult respiratory alone (75%) or in combination with adult cardiac (67%), paediatric respiratory (62%) and paediatric cardiac (58%). The specialist nurse to patient ratio was 1:1 in 59% of centres, with 24-h/day presence in 74%. Overall, the specialist nurse provided the 24-h/day management of the circuit, including interventions. Perfusionists were responsible for the technical aspects of circuit management.

CONCLUSIONS

A specialist nurse with perfusion backup is the staffing arrangement implemented by most centres and likely reflects the most efficient use of the professional competences available.

RELEVANCE TO CLINICAL PRACTICE

Staffing for adult respiratory extracorporeal support has important implications for the planning of workforce, training and education, quality of service and the number of ECMO beds available.

Extracorporeal Life Support in Pediatric and Neonatal Critical Care: A Review

Extracorporeal life support (ECLS) is a modified form of cardiopulmonary bypass used to provide prolonged tissue oxygen delivery in patients with respiratory and/or cardiac failure. The first large-scale success of ECLS was achieved in the management of term newborns with respiratory failure. ECLS has become an accepted therapeutic modality for neonates, children, and adults who have failed conventional therapy and in whom cardiac and/or respiratory insufficiency is potentially reversible. The use of ECLS allows one to reduce other cardiopulmonary supports and apply a gentle ventilation strategy in a population of severely compromised critical care patients. ECLS has now been employed in more than 26,000 neonatal and pediatric patients with an overall survival rate of 68%. ECLS has evolved significantly over 25 years of clinical practice; patient selection for this complex and highly invasive therapy, as well as how ECLS is employed in different patient groups, is constantly changing. Generally, ECLS is used more liberally now than in the past. The number of patients requiring this support, however, is declining yearly, and those patients who receive ECLS compose a more severe subset of an intensive care population. This review provides an overview of the development of ECLS and the equipment and techniques employed. The use of ECLS for neonatal respiratory failure, pediatric respiratory failure, and cardiac support are outlined. Management of the ECLS patient is discussed in detail, and outcome of these patients is reviewed. Finally, current trends and future implications of ECLS in neonatal and pediatric critical care are addressed.

Extracorporeal membrane oxygenation for critically ill adults

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is a form of life support that targets the heart and lungs. Extracorporeal membrane oxygenation for severe respiratory failure accesses and returns blood from the venous system and provides non-pulmonary gas exchange. Extracorporeal membrane oxygenation for severe cardiac failure or for refractory cardiac arrest (extracorporeal cardiopulmonary resuscitation (ECPR)) provides gas exchange and systemic circulation. The configuration of ECMO is variable, and several pump-driven and pump-free systems are in use. Use of ECMO is associated with several risks. Patient-related adverse events include haemorrhage or extremity ischaemia; circuit-related adverse effects may include pump failure, oxygenator failure and thrombus formation. Use of ECMO in newborns and infants is well established, yet its clinical effectiveness in adults remains uncertain.

OBJECTIVES

The primary objective of this systematic review was to determine whether use of veno-venous (VV) or venous-arterial (VA) ECMO in adults is more effective in improving survival compared with conventional respiratory and cardiac support.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid) and EMBASE (Ovid) on 18 August 2014. We searched conference proceedings, meeting abstracts, reference lists of retrieved articles and databases of ongoing trials and contacted experts in the field. We imposed no restrictions on language or location of publications.

SELECTION CRITERIA

We included randomized controlled trials (RCTs), quasi-RCTs and cluster-RCTs that compared adult ECMO versus conventional support.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of all retrieved citations against the inclusion criteria. We independently reviewed full-text copies of studies that met the inclusion criteria. We entered all data extracted from the included studies into Review Manager. Two review authors independently performed risk of bias assessment. All included studies were appraised with respect to random sequence generation, concealment of allocation, blinding of outcome assessment, incomplete outcome data, selective reporting and other bias.

MAIN RESULTS

We included four RCTs that randomly assigned 389 participants with acute respiratory failure. Risk of bias was low in three RCTs and high in one RCT. We found no statistically significant differences in all-cause mortality at six months (two RCTs) or before six months (during 30 days of randomization in one trial and during hospital stay in another RCT). The quality of the evidence was low to moderate, and further research is very likely to impact our confidence in the estimate of effects because significant changes have been noted in ECMO applications and treatment modalities over study periods to the present.Two RCTs supplied data on disability. In one RCT survival was low in both groups but none of the survivors had limitations in their daily activities six months after discharge. The other RCT reported improved survival without severe disability in the intervention group (transfer to an ECMO centre ± ECMO) six months after study randomization but no statistically significant differences in health-related quality of life.In three RCTs, participants in the ECMO group received greater numbers of blood transfusions. One RCT recorded significantly more non-brain haemorrhage in the ECMO group. Another RCT reported two serious adverse events in the ECMO group, and another reported three adverse events in the ECMO group.Clinical heterogeneity between studies prevented meta-analyses across outcomes. We found no completed RCT that had investigated ECMO in the context of cardiac failure or arrest. We found one ongoing RCT that examined patients with acute respiratory failure and two ongoing RCTs that included patients with acute cardiac failure (arrest).

AUTHORS' CONCLUSIONS

Extracorporeal membrane oxygenation remains a rescue therapy. Since the year 2000, patient treatment and practice with ECMO have considerably changed as the result of research findings and technological advancements over time. Over the past four decades, only four RCTs have been published that compared the intervention versus conventional treatment at the time of the study. Clinical heterogeneity across these published studies prevented pooling of data for a meta-analysis.We recommend combining results of ongoing RCTs with results of trials conducted after the year 2000 if no significant shifts in technology or treatment occur. Until these new results become available, data on use of ECMO in patients with acute respiratory failure remain inconclusive. For patients with acute cardiac failure or arrest, outcomes of ongoing RCTs will assist clinicians in determining what role ECMO and ECPR can play in patient care.

Implementation of quality management in early stages of research and development projects at a university

The ultimate objective of university research and development projects is usually to create knowledge, but also to successfully transfer results to industry for subsequent marketing. We hypothesized that the university technology transfer requires efficient measures to improve this important step. Besides good scientific practice, foresighted and industry-specific adapted documentation of research processes in terms of a quality management system might improve the technology transfer. In order to bridge the gap between research institute and cooperating industry, a model project has been accompanied by a project specific amount of quality management. However, such a system had to remain manageable and must not constrain the researchers' creativity. Moreover, topics and research team are strongly interdisciplinary, which entails difficulties regarding communication because of different perspectives and terminology. In parallel to the technical work of the model project, an adaptable quality management system with a quality manual, defined procedures, and forms and documents accompanying the research, development and validation was implemented. After process acquisition and analysis the appropriate amount of management for the model project was identified by a self-developed rating system considering project characteristics like size, innovation, stakeholders, interdisciplinarity, etc. Employees were trained according to their needs. The management was supported and the technical documentation was optimized. Finally, the quality management system has been transferred successfully to further projects.

Early biomarker activity in severe sepsis and septic shock and a contemporary review of immunotherapy trials: not a time to give up, but to give it earlier

Improving time to diagnosis and intervention has positively impacted outcomes in acute myocardial infarction, stroke, and trauma through elucidating the early pathogenesis of those diseases. This insight may partly explain the futility of time-insensitive immunotherapy trials for severe sepsis and septic shock. The aim of this study was to examine the early natural history of circulatory biomarker activity in sepsis, relative to previous animal and human outcome trials. We conducted a literature search using PubMed, MEDLINE, and Google Scholar to identify outcome trials targeting biomarkers with emphasis on the timing of therapy. These findings were compared with the biomarker activity observed over the first 72 h of hospital presentation in a cohort of severe sepsis and septic shock patients. Biomarker levels in animal and human research models are elevated within 30 min after exposure to an inflammatory septic stimulus. Consistent with these findings, the biomarker cascade is activated at the most proximal point of hospital presentation in our patient cohort. These circulatory biomarkers overlap; some have bimodal patterns and generally peak between 3 and 36 h while diminishing over the subsequent 72 h of observation. When this is taken into account, prior outcome immunotherapy trials have generally enrolled patients after peak circulatory biomarker concentrations. In previous immunotherapy sepsis trials, intervention was delayed after the optimal window of peak biomarker activity. As a result, future studies need to recalibrate the timing of enrollment and administration of immunotherapy agents that still may hold great promise for this deadly disease.

Bivalirudin versus heparin as an anticoagulant during extracorporeal membrane oxygenation: a case-control study

OBJECTIVE

Heparin-based anticoagulation for patients undergoing extracorporeal membrane oxygenation has many limitations, including a high risk of heparin-induced thrombocytopenia. However, little experience with other anticoagulants in these patients has been described. The aim of this study was to compare bivalirudin-based anticoagulation with heparin-based protocols in a population of patients treated with venovenous or venoarterial extracorporeal membrane oxygenation.

DESIGN

In this case-control study, 10 patients received bivalirudin (cases) and 10 heparin (controls). The target activated partial thromboplastin time (aPTT) was 45 to 60 seconds.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

aPTT variations >20% of the previous value were much more frequent in patients treated with heparin than in patients receiving bivalirudin (52 v 24, p < 0.001). The number of corrections of the anticoagulant dose was higher in the heparin group compared with the bivalirudin group (58 v 51), although it did not reach statistical significance. Bleeding, thromboembolic complications, extracorporeal membrane oxygenation (ECMO) support duration, mortality, and the number of episodes of aPTT >80 seconds were not different between the 2 groups. A further analysis was performed in the bivalirudin group according to the presence of acute renal failure requiring continuous venovenous hemofiltration. The median bivalirudin dose in patients with or without hemofiltration was 0.041 (0.028-0.05) mg/kg/h and 0.028 (0-0.041) mg/kg/h, respectively (p = 0.2).

CONCLUSIONS

Bivalirudin-based anticoagulation may represent a new method of anticoagulation for reducing thromboembolic and bleeding complications, which still jeopardize the application of extracorporeal membrane oxygenation. Moreover, bivalirudin is free from the risk of heparin-induced thrombocytopenia. Higher doses of bivalirudin may be needed in patients undergoing hemofiltration.

A review of the fundamental principles and evidence base in the use of extracorporeal membrane oxygenation (ECMO) in critically ill adult patients

Extracorporeal membrane oxygenation (ECMO) comprises a commonly used method of extracorporeal life support. It has proven efficacy and is an accepted modality of care for isolated respiratory or cardiopulmonary failure in neonatal and pediatric populations. In adults, there are conflicting studies regarding its benefit, but it is possible that ECMO may be beneficial in certain adult populations beyond postcardiotomy heart failure. As such, all intensivists should be familiar with the evidence-base and principles of ECMO in adult population. The purpose of this article is to review the evidence and to describe the fundamental steps in initiating, adjusting, troubleshooting, and terminating ECMO so as to familiarize the intensivist with this modality.

Use of extracorporeal life support in adults with severe acute respiratory failure

Extracorporeal membrane oxygenation (ECMO) is a recognized and accepted therapeutic option in the treatment of neonatal and pediatric respiratory failure. However, early studies in adults did not demonstrate a survival benefit associated with the utilization of ECMO for severe acute respiratory failure. Despite this historical lack of benefit, use of ECMO in adult patients has seen a recent resurgence. Local successes and a recently published randomized trial have both demonstrated promising results in an adult population with high baseline mortality and limited therapeutic options. This article will review the history of ECMO use for respiratory failure; investigate the driving forces behind the latest surge in interest in ECMO for adults with refractory severe acute respiratory failure; and describe potential applications of ECMO that will likely increase in the near future.

Extracorporeal lung support for patients who had severe respiratory failure secondary to influenza A (H1N1) 2009 infection in Canada

Background

From March to July 2009, influenza A (H1N1) 2009 (H1N1-2009) virus emerged as a major cause of respiratory failure that required mechanical ventilation. A small proportion of patients who had this condition developed severe respiratory failure that was unresponsive to conventional therapeutic interventions. In this report, we describe characteristics, treatment, and outcomes of critically ill patients in Canada who had H1N1-2009 infection and were treated with extracorporeal lung support (ECLS).

Methods

We report the findings of a case series of six patients supported with ECLS who were included in a cohort study of critically ill patients with confirmed H1N1-2009 infection. The patients were treated in Canadian adult and pediatric intensive care units (ICUs) from April 16, 2009 to August 12, 2009. We describe the nested sample treated with ECLS and compare it with the larger sample.

Results

During the study period, 168 patients in Canada were admitted to ICUs for severe respiratory failure due to confirmed H1N1-2009 infection. Due to profound hypoxemia unresponsive to conventional therapeutic interventions, six (3.6%) of these patients were treated with ECLS in four ICUs. Four patients were treated with veno-venous pump-driven extracorporeal membrane oxygenation (vv-ECMO), and two patients were treated with pumpless lung assist (NovaLung iLA). The mean duration of support was 15 days. Four of the six patients survived (66.6%), one of the surviving patients was supported with iLA and the other three surviving patients were supported with ECMO. The two deaths were due to multiorgan failure, which occurred while the patients were on ECLS.

Interpretation

Extracorporeal lung support may be an effective treatment for patients who have H1N1-2009 infection and refractory hypoxemia. Survival of these patients treated with ECLS is similar to that reported for patients who have acute respiratory distress syndrome of other etiologies and are treated with ECMO.

Peritoneal perfusion with oxygenated perfluorocarbon augments systemic oxygenation

Background

Despite maximal ventilatory support, many patients die from hypoxia in the setting of potentially reversible pulmonary failure. There remains a pressing need for additional pulmonary supportive care measures, especially techniques that do not require systemic anticoagulation. The objective of our experiments was to determine whether systemic oxygenation could be increased in a large animal, with induced hypoxia, by perfusing the abdominal cavity with oxygenated perfluorocarbons.

Methods

Fifteen pigs with a mean (± SD) weight of 45 ± 5 kg were intubated and rendered hypoxic by ventilating them with a blend of nitrogen and oxygen to achieve subatmospheric concentrations of inspired oxygen ranging from 18 to 10%, resulting in baseline mean Pao₂ range of 65.9 ± 9.7 to 26.6 ± 2.8 mm Hg, respectively. Peritoneal perfusion was performed in eight animals with oxygenated perfluorocarbon and in seven control animals with oxygenated saline solution.

Results

The average increase in Pao₂ with oxygenated perfluorocarbon perfusion, compared to oxygenated saline solution perfusion, ranged from 8.1 to 18.2 mm Hg. A common treatment effect was estimated across all fraction of inspired oxygen (Fio₂) values, representing the average mean difference in oxygen uptake between oxygenated perfluorocarbon and saline solution, irrespective of the level of Fio₂. This average was 12.8 mm Hg (95% confidence interval, 7.4 to 18.2; p < 0.001). The most clinically relevant results occurred at an Fio₂ of 14%, resulting in a baseline mean Pao₂ of 39.4 ± 5.0 mm Hg with oxygenated saline solution perfusion, and a mean Pao₂ of 55.3 ± 7.6 mm Hg with oxygenated perfluorocarbon perfusion. This corresponded to an increase in arterial oxygen saturation from 73 to 89%.

Conclusion

These results of our principle experiments demonstrate that the peritoneal cavity can be used for gas exchange and, in our model, yielded clinically relevant increases in systemic arterial oxygen levels. This technique may have the potential for the supportive care of patients dying from hypoxia in the setting of reversible lung injury.

Ventilatory strategies and adjunctive therapy in ARDS

Acute respiratory distress syndrome, a diagnosis based on physiologic and radiological criteria, occurs commonly in critical care setting. A major challenge in evaluating therapies that may improve survival in ARDS is that it is not a single disease entity but, rather, numerous different diseases that result in endothelial injury, where the most obvious manifestation is within the lung resulting in pulmonary oedema. It has been shown that poor ventilatory technique that is injurious to the lungs can propagate systemic inflammatory response and adversely affect the mortality. The current data suggest that high tidal volumes with high plateau pressures are deleterious and a strategy of ventilation with lower tidal volumes and lower plateau pressure is associated with lower mortality. There may be a role for recruitment manoeuvres as well. Other forms of respiratory support still require further research. The present understanding of optimal ventilatory management and other adjunctive therapies are reviewed.

The development and use of extracorporeal membrane oxygenation in neonates

Extracorporeal membrane oxygenation (ECMO) is the utilization of a modified heart-lung machine to provide temporary support for patients with severe respiratory or cardiac failure. In contrast to patients managed with traditional cardiopulmonary bypass, patients on ECMO undergo cannulation of relatively accessible blood vessels, are maintained at normal body temperature, and only require partial anticoagulation with heparin. Although first developed for use in adults, ECMO has been most successful in the treatment of newborn infants with life-threatening pulmonary failure. Since 1974, over 17,000 infants have received ECMO with a 78% survival rate. There is a 15%-20% incidence of neurodevelopmental disabilities among ECMO survivors.

Development of a Photolytic Artificial Lung: Preliminary Concept Validation

There is an established need for pulmonary technology capable of facilitated gas exchange in the blood, thereby bypassing the alveolar-capillary interface. To address this need, we emulated one of the best-known photolytic reactions in nature, photosynthesis, in which green plants use sunlight to drive the exchange of oxygen for carbon dioxide. Our goal in the current study was to demonstrate the feasibility of direct photolytic conversion of water to liquid phase oxygen (dissolved oxygen [DO]) in synthetic serum. To this end, we constructed a test flow cell consisting of a conductive coating of vacuum-deposited titanium (Ti) metal, adherent TiO2 (anatase), and MnO2, applied as a laminate to a glass substrate, and then immersed the device in Locke's-Ringer solution (synthetic blood serum). Long wavelength (low energy) ultraviolet A laser light, directed to the transparent glass slide, reproducibly resulted in the generation of an active form of oxygen (AO), which was subsequently converted directly by the catalytic action of MnO2 to DO. The absence of light activation provided an entirely null response. We conclude that the photolytic production of DO from water in a blood serum surrogate, with commensurate CO2 clearance, is feasible. A prototype photolytic module is proposed, which uses multiple parallel photolytic surfaces to improve system production capacity and CO2 clearance through selective gas-liquid separation from the oxygen-enriched fluid.