Extracorporeal life support for adults with severe acute respiratory failure

Effects of adding the second drainage cannula in severely hypoxemic patients supported with VV ECMO due to COVID-19-associated ARDS

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is a recognized method of support in patients with severe and refractory acute respiratory distress syndrome (ARDS) caused by SARS-CoV-2 infection. While veno-venous (VV) ECMO is the most common type, some patients with severe hypoxemia may require modifications to the ECMO circuit. In this study, we aimed to investigate the effects of adding a second drainage cannula to the circuit in patients with refractory hypoxemia, on their gas exchange, mechanical ventilation, ECMO settings, and clinical outcomes.

METHODS

We conducted an observational retrospective study based on a single-center institutional registry including all consecutive cases of COVID-19 patients requiring ECMO admitted to the Centre of Extracorporeal Therapies in Warsaw between March 1, 2020 and March 1, 2022. We selected patients who had an additional drainage cannula inserted. Changes in ECMO and ventilator settings, blood oxygenation, and hemodynamic parameters, as well as clinical outcomes were assessed.

RESULTS

Of 138 VV ECMO patients, 12 (9%) patients met the inclusion criteria. Ten patients (83%) were men, and mean age was 42.2 ± 6.8. An addition of drainage cannula resulted in a significant raise in ECMO blood flow (4.77 ± 0.44 to 5.94 ± 0.81 [L/min]; p = 0.001), and the ratio of ECMO blood flow to ECMO pump rotations per minute (RPM), whereas the raise in ECMO RPM alone was not statistically significant (3432 ± 258 to 3673 ± 340 [1/min]; p = 0.064). We observed a significant drop in ventilator FiO2 and a raise in PaO2 to FiO2 ratio, while blood lactates did not change significantly. Nine patients died in hospital, one was referred to lung transplantation center, two were discharged uneventfully.

CONCLUSIONS

The use of an additional drainage cannula in severe ARDS associated with COVID-19 allows for an increased ECMO blood flow and improved oxygenation. However, we observed no further improvement in lung-protective ventilation and poor survival.

Challenges in ARDS Definition, Management, and Identification of Effective Personalized Therapies

Over the last decade, the management of acute respiratory distress syndrome (ARDS) has made considerable progress both regarding supportive and pharmacologic therapies. Lung protective mechanical ventilation is the cornerstone of ARDS management. Current recommendations on mechanical ventilation in ARDS include the use of low tidal volume (V_T) 4-6 mL/kg of predicted body weight, plateau pressure (P_PLAT) < 30 cmH₂O, and driving pressure (∆P) < 14 cmH₂O. Moreover, positive end-expiratory pressure should be individualized. Recently, variables such as mechanical power and transpulmonary pressure seem promising for limiting ventilator-induced lung injury and optimizing ventilator settings. Rescue therapies such as recruitment maneuvers, vasodilators, prone positioning, extracorporeal membrane oxygenation, and extracorporeal carbon dioxide removal have been considered for patients with severe ARDS. Regarding pharmacotherapies, despite more than 50 years of research, no effective treatment has yet been found. However, the identification of ARDS sub-phenotypes has revealed that some pharmacologic therapies that have failed to provide benefits when considering all patients with ARDS can show beneficial effects when these patients were stratified into specific sub-populations; for example, those with hyperinflammation/hypoinflammation. The aim of this narrative review is to provide an overview on current advances in the management of ARDS from mechanical ventilation to pharmacological treatments, including personalized therapy.

Extracorporeal Carbon Dioxide Removal: From Pathophysiology to Clinical Applications; Focus on Combined Continuous Renal Replacement Therapy

Lung-protective ventilation (LPV) with low tidal volumes can significantly increase the survival of patients with acute respiratory distress syndrome (ARDS) by limiting ventilator-induced lung injuries. However, one of the main concerns regarding the use of LPV is the risk of developing hypercapnia and respiratory acidosis, which may limit the clinical application of this strategy. This is the reason why different extracorporeal CO₂ removal (ECCO₂R) techniques and devices have been developed. They include low-flow or high-flow systems that may be performed with dedicated platforms or, alternatively, combined with continuous renal replacement therapy (CRRT). ECCO₂R has demonstrated effectiveness in controlling PaCO₂ levels, thus allowing LPV in patients with ARDS from different causes, including those affected by Coronavirus disease 2019 (COVID-19). Similarly, the suitability and safety of combined ECCO₂R and CRRT (ECCO₂R-CRRT), which provides CO₂ removal and kidney support simultaneously, have been reported in both retrospective and prospective studies. However, due to the complexity of ARDS patients and the limitations of current evidence, the actual impact of ECCO₂R on patient outcome still remains to be defined. In this review, we discuss the main principles of ECCO₂R and its clinical application in ARDS patients, in particular looking at clinical experiences of combined ECCO₂R-CRRT treatments.

Optimal Settings at Initiation of Veno-Venous Extracorporeal Membrane Oxygenation: An Exploratory In-Silico Study

The Extracorporeal Life Support Organisation (ELSO) recommends initiating veno-venous extracorporeal membrane oxygenation (ECMO) with sweep gas flow rate () of 2 L/min and extracorporeal circuit blood flow () of 2 L/min. We used an in-silico model to examine the effect on gas exchange of initiating ECMO with different and , and the effect of including 5% in sweep gas. This was done using a set of patient examples, each with different physiological derangements at baseline (before ECMO). When ECMO was initiated following ELSO recommendations in the patient examples with significant hypercapnia at baseline, sometimes fell to < 50% of the baseline , a magnitude of fall associated with adverse neurological outcomes. In patient examples with very low baseline arterial oxygen saturation (), initiation of ECMO did not always increase to > 80%. Initiating ECMO with of 1 L/min and of 4 L/min, or with sweep gas containing 5% , of 2 L/min, and of 4 L/min, reduced the fall in and increased the rise in compared to the ELSO strategy. While ELSO recommendations may suit most patients, they may not suit patients with severe physiological derangements at baseline.

A Narrative Review of Nutrition Therapy in Patients Receiving Extracorporeal Membrane Oxygenation

The use of extracorporeal membrane oxygenation (ECMO) in patients with severe cardiorespiratory failure has seen significant growth in the last decade. Despite this, there is paucity of data surrounding the optimum nutritional management for ECMO patients. This review aimed to describe current nutrition practices in patients receiving ECMO, critically appraise available studies and identify areas for future research. A literature search was conducted in PubMed, MEDLINE, and CINAHL Plus to identify all randomized trials and observational studies published between July 2000 and July 2020 investigating nutrition practices in critically ill adults receiving ECMO. The primary outcomes were nutritional adequacy, gastrointestinal complications, and physical function. Secondary outcomes included mortality, length of stay, and duration on ECMO support. From a total of 31 studies identified, 12 met the inclusion criteria. Nine observational studies were reviewed following eligibility assessment. Early enteral nutrition was deemed safe and feasible for ECMO patients; however, meeting nutritional targets was challenging. Utilizing alternative nutrition routes is an option, although risks and benefits should be taken into consideration. Data on gastrointestinal complications and other clinical outcomes were inconsistent, and no data were identified investigating the effects of nutrition on the physical and functional recovery of ECMO patients. Nutrition therapy in ECMO patients should be provided in line with current guidelines for nutrition in critical illness until further data are available. Further prospective, randomized studies investigating optimum nutrition practices and effects on clinical and functional outcomes are urgently required.

Mechanical Ventilation during ECMO: Lessons from Clinical Trials and Future Prospects

Acute Respiratory Distress Syndrome (ARDS) accounts for 10% of ICU admissions and affects 3 million patients each year. Despite decades of research, it is still associated with one of the highest mortality rates in the critically ill. Advances in supportive care, innovations in technologies and insights from recent clinical trials have contributed to improved outcomes and a renewed interest in the scope and use of Extracorporeal life support (ECLS) as a treatment for severe ARDS, including high flow veno-venous Extracorporeal Membrane Oxygenation (VV-ECMO) and low flow Extracorporeal Carbon Dioxide Removal (ECCO2R). The rationale being that extracorporeal gas exchange allows the use of lung protective ventilator settings, thereby minimizing ventilator-induced lung injury (VILI). Ventilation strategies are adapted to the patient's condition during the different stages of ECMO support. Several areas in the management of mechanical ventilation in patients on ECMO, such as the best ventilator mode, extubation-decannulation sequence and tracheostomy timing, are tailored to the patients' recovery. Reduction in sedation allowing mobilization, nutrition and early rehabilitation are subsequent therapeutic goals after lung rest has been achieved.

Intraoperative support during lung transplantation

The role of intraoperative mechanical support during lung transplantation (LTx) is essential to provide a safe hemodynamic and ventilatory status during critical intraoperative events. This hemodynamic and ventilatory stability is vital to minimize the odds of suboptimal outcomes, especially considering that, due to the scarcity of donors and the fact that more and more patients with significant comorbidities are being considered for this therapy, a more aggressive approach is often needed by the transplant centers. Hence, the attenuation of any potential injury that can happen during this complex event is paramount. While a thorough assessment of the donor and optimization of postoperative care is pursued, certainly protective intraoperative management would also contribute to better outcomes. Understanding each patient’s underlying anatomy and cardiopulmonary physiology, associated with awareness of critical events during a complicated procedure like LTx, is essential for a precise indication and safe use of support. Cardiopulmonary bypass (CPB) and veno-arterial extracorporeal membrane oxygenation (VA ECMO) have been the most common approaches used, with the latter gaining popularity more recently and we have used VA ECMO exclusively for the last decade. New technologies certainly contributed to more liberal use of VA ECMO intraoperatively, enabling a protecting and physiologic environment for the newly implanted grafts. In this setting, potential prophylactic use for lung protection during a critical period is also considered.

Hypercapnia from Physiology to Practice

Acute hypercapnic ventilatory failure is becoming more frequent in critically ill patients. Hypercapnia is the elevation in the partial pressure of carbon dioxide (PaCO₂) above 45 mmHg in the bloodstream. The pathophysiological mechanisms of hypercapnia include the decrease in minute volume, an increase in dead space, or an increase in carbon dioxide (CO₂) production per sec. They generate a compromise at the cardiovascular, cerebral, metabolic, and respiratory levels with a high burden of morbidity and mortality. It is essential to know the triggers to provide therapy directed at the primary cause and avoid possible complications.

[Extracorporeal membrane oxygenation and hemodynamics : Therapy is not only a friend of the heart]

Extracorporeal support systems for the heart and lungs are employed for cardiac, pulmonary and also cardiopulmonary failure; however, neither the pure lung support by venovenous extracorporeal membrane oxygenation (vvECMO) nor the venoarterial (va) ECMO behave in a hemodynamically inert manner with respect to the patient's own cardiovascular system. The success of ECMO treatment is decisively dependent on monitoring before and during the execution and the pathophysiological understanding of the hemodynamic changes that occur during treatment. This article explicitly elucidates these "concomitant phenomena" and discusses fundamental aspects of cardiovascular physiology and the specific interplay with ECMO treatment.

Ten golden rules for individualized mechanical ventilation in acute respiratory distress syndrome

Considerable progress has been made over the last decades in the management of acute respiratory distress syndrome (ARDS). Mechanical ventilation(MV) remains the cornerstone of supportive therapy for ARDS. Lung-protective MV minimizes the risk of ventilator-induced lung injury (VILI) and improves survival. Several parameters contribute to the risk of VILI and require careful setting including tidal volume (V_T), plateau pressure (P_plat), driving pressure (ΔP), positive end-expiratory pressure (PEEP), and respiratory rate. Measurement of energy and mechanical power allows quantification of the relative contributions of various parameters (V_T, P_plat, ΔP, PEEP, respiratory rate, and airflow) for the individualization of MV settings. The use of neuromuscular blocking agents mainly in cases of severe ARDS can improve oxygenation and reduce asynchrony, although they are not known to confer a survival benefit. Rescue respiratory therapies such as prone positioning, inhaled nitric oxide, and extracorporeal support techniques may be adopted in specific situations. Furthermore, respiratory weaning protocols should also be considered. Based on a review of recent clinical trials, we present 10 golden rules for individualized MV in ARDS management.

Achieving Safe Liberation During Weaning from VV-ECMO in Patients with Severe ARDS: The role of Tidal Volume and Inspiratory Effort

BACKGROUND

Weaning from venovenous extracorporeal membrane oxygenation (VV-ECMO) is not well studied. VV-ECMO can be discontinued when patients tolerate non-injurious mechanical ventilation (MV) during a sweep gas off trial (SGOT). However, predictors of safe liberation are unknown.

RESEARCH QUESTION

Can safe liberation from VV-ECMO be predicted at the bedside?

STUDY DESIGN AND METHODS

We conducted 2 observational studies of adults weaned from VV-ECMO for severe ARDS at Toronto General Hospital. We analyzed MV settings, respiratory mechanics and clinical variables to predict safe liberation from VV-ECMO, defined a priori as avoidance of ECMO recannulation, increase MV support, need for rescue therapy or hemodynamic instability developed within 48 hours after decannulation.

RESULTS

During both studies, 83 patients were weaned from VV-ECMO, of whom 21 (25%) did not meet criteria for safe liberation. In the retrospective study, higher tidal volume per predicted body weight (V_Tpbw, OR 1.58, 95%CI 1.05-2.40, P=0.03) and heart rate (HR, OR 1.07, 95%CI 1.01-1.13, P=0.02) at the end of SGOT were significantly associated with increased odds of unsafe liberation when adjusted for age (OR 1.02, 95%CI 0.95-1.09, P=0.63) and SOFA (OR 1.16, 95%CI 0.86-1.56, P=0.34). Change in ventilatory ratio (VR) had an imprecise association (OR 2.71, 95%CI 0.93-7.92, P=0.06) with unsafe liberation when adjusted for age (OR 1.03, 95%CI 0.96-1.10, P=0.42), SOFA (OR 1.11, 95%CI 0.81-1.51, P=0.52) and heart rate (OR 1.07, 95%CI 1.01-1.13, P=0.02). In the prospective study, patients who had unsafe liberation from VV-ECMO also had significantly higher inspiratory efforts (esophageal pressure swings 9 [7-13] vs 18 [7-25] cmH₂O, p=0.03), and worse outcomes (longer MV duration, ICU and hospital length of stay).

INTERPRETATION

Patients with higher tidal volume, heart rate, ventilatory ratio, and esophageal pressures swings during SGOT were less likely to achieve safe liberation from VV-ECMO.

Management of Adult Patients Supported with Venovenous Extracorporeal Membrane Oxygenation (VV ECMO): Guideline from the Extracorporeal Life Support Organization (ELSO)

Disclaimer: The use of venovenous extracorporeal membrane oxygenation (VV ECMO) in adults has rapidly increased worldwide. This ELSO guideline is intended to be a practical guide to patient selection, initiation, cannulation, management, and weaning of VV ECMO for adult respiratory failure. This is a consensus document which has been updated from the previous version to provide guidance to the clinician.

Effect of Driving Pressure Change During Extracorporeal Membrane Oxygenation in Adults With Acute Respiratory Distress Syndrome: A Randomized Crossover Physiologic Study

OBJECTIVES

Venovenous extracorporeal membrane oxygenation is an effective intervention to improve gas exchange in patients with severe acute respiratory distress syndrome. However, the mortality of patients with severe acute respiratory distress syndrome supported with venovenous extracorporeal membrane oxygenation remains high, and this may be due in part to a lack of standardized mechanical ventilation strategies aimed at further minimizing ventilator-induced lung injury. We tested whether a continuous positive airway pressure ventilation strategy mitigates ventilator-induced lung injury in patients with severe acute respiratory distress syndrome on venovenous extracorporeal membrane oxygenation, compared with current ventilation practice that employs tidal ventilation with limited driving pressure. We used plasma biomarkers as a surrogate outcome for ventilator-induced lung injury.

DESIGN

Randomized crossover physiologic study.

SETTING

Single-center ICU.

PATIENTS

Ten patients with severe acute respiratory distress syndrome supported on venovenous extracorporeal membrane oxygenation.

INTERVENTIONS

The study included four phases. After receiving pressure-controlled ventilation with driving pressure of 10 cm H2O for 1 hour (phase 1), patients were randomly assigned to receive first either pressure-controlled ventilation 20 cm H2O for 2 hours (phase 2) or continuous positive airway pressure for 2 hours (phase 3), and then crossover to the other phase for 2 hours; during phase 4 ventilation settings returned to baseline (pressure-controlled ventilation 10 cm H2O) for 4 hours.

MEASUREMENTS AND MAIN RESULTS

There was a linear relationship between the change in driving pressure and the plasma concentration of interleukin-6, soluble receptor for advanced glycation end products, interleukin-1ra, tumor necrosis factor alpha, surfactant protein D, and interleukin-10.

CONCLUSIONS

Ventilator-induced lung injury may occur in acute respiratory distress syndrome patients on venovenous extracorporeal membrane oxygenation despite the delivery of volume- and pressure-limited mechanical ventilation. Reducing driving pressure to zero may provide more protective mechanical ventilation in acute respiratory distress syndrome patients supported with venovenous extracorporeal membrane oxygenation. However, the risks versus benefits of such an approach need to be confirmed in studies that are designed to test patient centered outcomes.

Perioperative, protective use of extracorporeal membrane oxygenation in complex thoracic surgery

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is increasingly used in patients undergoing complex thoracic surgical procedures. However, studies reporting the clinical outcomes of these patients are limited to case reports, without real consensus. Our aim was to evaluate the perioperative use of ECMO as respiratory and/or circulatory support in thoracic surgery: indications, benefits, and perioperative management.

METHODS

Between May 2013 and December 2018, we reviewed the clinical data of 15 patients (11 males and 4 females; mean age: 47 years old; range, 25-73 years) undergoing ECMO-assisted thoracic surgery in our hospital.

RESULTS

Of the 15 patients, 10 cases received peripheral veno-arterial (VA) ECMO and five cases received veno-venous (VV) ECMO. Indications for ECMO were pulmonary transplantation with hard-to-maintain oxygenation (n = 5), traumatic main bronchial rupture (n = 2), traumatic lung injury (n = 1), airway tumor leading to severe airway stenosis (n = 2), huge thoracic mass infiltrated vena cava (n = 5). The ECMO duration was 1-51 hours. All patients were successfully extubated and weaned from ECMO postoperatively. The main complications were hemorrhage (26.7%), infection (33.3%), acute hepatic dysfunction (33.3%), and venous thrombosis (26.7%). There was only one hospital death and postoperative one-year survival rate was 86%.

CONCLUSION

Our experience indicates that ECMO is a feasible method for complex trachea-bronchial surgery, huge thoracic mass excision and lung transplantation, and the ECMO-related risks may be justified. With further accumulation of experience with ECMO, a more sophisticated protocol for management of critical airway or heart failure problems in thoracic surgeries can be derived.

Veno-venous ECMO as a platform to evaluate lung lavage and surfactant replacement therapy in an animal model of severe ARDS

BACKGROUND

There are limited therapeutic options directed at the underlying pathological processes in acute respiratory distress syndrome (ARDS). Experimental therapeutic strategies have targeted the protective systems that become deranged in ARDS such as surfactant. Although results of surfactant replacement therapy (SRT) in ARDS have been mixed, questions remain incompletely answered regarding timing and dosing strategies of surfactant. Furthermore, there are only few truly clinically relevant ARDS models in the literature. The primary aim of our study was to create a clinically relevant, reproducible model of severe ARDS requiring extracorporeal membrane oxygenation (ECMO). Secondly, we sought to use this model as a platform to evaluate a bronchoscopic intervention that involved saline lavage and SRT.

METHODS

Yorkshire pigs were tracheostomized and cannulated for veno-venous ECMO support, then subsequently given lung injury using gastric juice via bronchoscopy. Animals were randomized post-injury to either receive bronchoscopic saline lavage combined with SRT and recruitment maneuvers (treatment, n = 5) or recruitment maneuvers alone (control, n = 5) during ECMO.

RESULTS

PaO₂/FiO₂ after aspiration injury was 62.6 ± 8 mmHg and 60.9 ± 9.6 mmHg in the control and treatment group, respectively (p = 0.95) satisfying criteria for severe ARDS. ECMO reversed the severe hypoxemia. After treatment with saline lavage and SRT during ECMO, lung physiologic and hemodynamic parameters were not significantly different between treatment and controls.

CONCLUSIONS

A clinically relevant severe ARDS pig model requiring ECMO was established. Bronchoscopic saline lavage and SRT during ECMO did not provide a significant physiologic benefit compared to controls.

Duration of sweep gas off trial for weaning from venovenous extracorporeal membrane oxygenation

Background:

No data are available on the duration of time needed to assess the adequacy of lung function after stopping sweep gas for weaning of venovenous extracorporeal membrane oxygenation (ECMO). The objective of this study was to investigate changes in arterial blood gases (ABGs) during sweep gas off trials in patients receiving venovenous ECMO.

Methods:

Data on patients receiving venovenous ECMO, with a weaning trial at least once, were collected prospectively from January 2012 through December 2017. Serial changes in ABGs during sweep gas off trial and clinical outcomes after weaning from venovenous ECMO were evaluated.

Results:

Over the study period, 192 sweep gas off trials occurred in 93 patients: 115 (60%) failed and 77 (40%) were successful. During the trial, significant changes in blood gases were observed within 1 h in all patients. When serial ABGs were compared according to trial off results, there were no significant differences in the pH, PaCO₂, and HCO₃⁻ trends across time points between successful and failed trials. However, PaO₂ (70.6 versus 93.4 mmHg), SaO₂ (91.9 versus 95.2%), and PaO₂/FiO₂ ratio (164.0 versus 233.4) were significantly lower in failed trials than successful trials within 1 h after stopping sweep gas. After 2 h of trial off, no significant change in blood gases was observed until the end of the trial.

Conclusions:

No change in blood gases was observed 2 h after stopping sweep gas in patients receiving venovenous ECMO. Based on our institutional experience, however, we suggest monitoring for 2 h or more after stopping sweep gas flow to assess if patients are ready for decannulation.

The reviews of this paper are available via the supplemental material section.

Successful COVID-19 rescue therapy by extra-corporeal membrane oxygenation (ECMO) for respiratory failure: a case report

BACKGROUND

The value of extracorporeal membrane oxygenation (ECMO) for patients suffering from novel coronavirus disease 2019 (COVID-19) as a rescue therapy for respiratory failure remains controversial and associated with high mortality rates of 50 to 82% in early reports from Wuhan, China. We hypothesized that patient outcomes would be improved at our tertiary cardiothoracic surgery referral center with a protocolized team-approach for ECMO treatment of patients with severe COVID-19 disease.

CASE PRESENTATION

A 51-year-old healthy female developed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) bilateral pneumonia while vacationing in Colorado with her family. She was transferred to our facility for a higher level of care. Her respiratory status continued to deteriorate despite maximized critical care, including prone positioning ventilation and nitric oxide inhalation therapy. Veno-venous ECMO was initiated on hospital day 7 in conjunction with a 10-day course of compassionate use antiviral treatment with remdesivir. The patient's condition improved significantly and she was decannulated from ECMO on hospital day 17 (ECMO day 11). She was successfully extubated and eventually discharged to rehabilitation on hospital day 28.

CONCLUSION

This case report demonstrates a positive outcome in a young patient with COVID-19 treated by the judicious application of ECMO in conjunction with compassionate use antiviral treatment (remdesivir). Future prospective multi-center studies are needed to validate these findings in a larger cohort of patients.

Acute respiratory distress syndrome in acute pancreatitis

Development of organ failure is one of the major determinants of mortality in patients with acute pancreatitis (AP). Acute respiratory distress syndrome (ARDS) is an important cause of respiratory failure in AP and is associated with high mortality. Pathogenesis of ARDS in AP is incompletely understood. Release of various cytokines plays an important role in development of ARDS in AP. Increased gut permeability due to various toxins, inflammatory mediators, and pancreatic enzymes potentiates lung injury by gut-lymph-lung axis leading on to increased translocation of bacterial endotoxins. Various scoring systems, serum levels of various cytokines and lung ultrasound have been evaluated for prediction of development of ARDS in AP with varying results. Various drugs have shown encouraging results in prevention of ARDS in animal models but these encouraging results in animal models are yet to be confirmed in clinical studies. There is no specific effective treatment for ARDS. Treatment of sepsis and local complications of AP should be done according to the standard management strategies. Lung protective ventilatory strategies are of paramount importance to improve outcome of patients of AP with ARDS and therefore effective coordination between gastroenterologists and intensivists is needed for effective management of these patients.

Extracorporeal membrane oxygenation support in adult patients with acute respiratory distress syndrome

Introduction: The global number of patients receiving extracorporeal membrane oxygenation (ECMO) support has been growing after several studies highlighted the favorable results attained in cases of severe respiratory failure. However, evidence-based guidelines for optimal use of ECMO are lacking.Areas covered: This review covers optimal candidates, timing of initiation, strategies for patient management including mechanical ventilation, and decision-making regarding discontinuation of ECMO based on its potential role in treatment of patients with acute respiratory distress syndrome.Expert opinion: Early initiation of ECMO should be considered if hypoxemia and uncompensated hypercapnia do not respond to optimal conventional treatment. Use of a comprehensive management approach for preventing additional lung injury and extrapulmonary organ failure is critical during ECMO support to ensure the best outcome. The possibility of weaning from ECMO should be fully assessed by a multidisciplinary team during ECMO support. Futility should not be determined solely by duration of ECMO, and use of prolonged ECMO for lung recovery may be worthwhile.

Successful Resuscitation Using Extracorporeal Membrane Oxygenation of 2 Patients With Severe Liver Rupture: A Case Report

Extracorporeal membrane oxygenation is a rescue treatment for respiratory or cardiac failure. Its use is limited in patients predisposed to bleeding due to heparin administration. We present 2 patients with deranged coagulation after liver rupture successfully treated by extracorporeal membrane oxygenation. One patient with cardiac arrest developed a liver laceration during resuscitation. Liver suture was performed, but acute respiratory distress syndrome (PaO2/fraction of inspired oxygen, 50) necessitated venovenous extracorporeal membrane oxygenation. The other patient suffered hemothorax, thoracic aorta dissection, and liver rupture. Liver segments VI and VII were resected. Endovascular aneurysm repair of aortic dissection and venoarterial extracorporeal membrane oxygenation were performed. Both patients survived without neurological sequelae.

ERS International Congress, Madrid, 2019: highlights from the Respiratory Intensive Care Assembly

The Respiratory Intensive Care Assembly of the European Respiratory Society is delighted to present the highlights from the 2019 International Congress in Madrid, Spain. We have selected four sessions that discussed recent advances in a wide range of topics: from acute respiratory failure to cough augmentation in neuromuscular disorders and from extra-corporeal life support to difficult ventilator weaning. The subjects are summarised by early career members in close collaboration with the Assembly leadership. We aim to give the reader an update on the most important developments discussed at the conference. Each session is further summarised into a short list of take-home messages.

Blood clot removal by cryoextraction in critically ill patients with pulmonary hemorrhage

Background

Severe pulmonary hemorrhage is a life-threatening complication in critically ill patients. Due to tracheobronchial obstruction, ventilation is often impaired. Traditionally, rigid bronchoscopy is an option for recanalization. However, in comparison to flexible bronchoscopy, the application of rigid bronchoscopy is more complex. Against this background we evaluated the use of flexible cryo-probes for blood clot removal in critically ill patients.

Methods

Retrospectively, we identified 16 patients (median age: 60 years, 69% male patients), who suffered from severe airway obstruction due to blood clots. All patients required invasive ventilation and 11 patients depended on extracorporeal membrane oxygenation (ECMO). To remove blood clots, flexible bronchoscopic cryoextraction was performed in n=27 cases, whereas rigid bronchoscopy was only needed in two cases.

Results

Whereas in 9 cases single flexible cryoextraction was successful immediately, the procedure had to be repeated again in 7 patients. In all cases, tracheobronchial obstruction was treated with success and conditions of invasive ventilation were improved. In no case severe complications were observed.

Conclusions

In consideration of the underlying evaluation, we highly recommend flexible cryoextraction as both a safe and less complex technique for blood clot removal in critically ill patients.

Reclassifying Acute Respiratory Distress Syndrome

RATIONALE

The ratio of Pa_O2 to Fi_O2 (P/F) defines acute respiratory distress syndrome (ARDS) severity and suggests appropriate therapies.

OBJECTIVES

We investigated 1) whether a 150-mm-Hg P/F threshold within the range of moderate ARDS (100-200 mm Hg) would define two subgroups that were more homogeneous; and 2) which criteria led the clinicians to apply extracorporeal membrane oxygenation (ECMO) in severe ARDS.

METHODS

At the 150-mm-Hg P/F threshold, moderate patients were split into mild-moderate (n = 50) and moderate-severe (n = 55) groups. Patients with severe ARDS (Fi_O2 not available in three patients) were split into higher (n = 63) and lower (n = 18) Fi_O2 groups at an 80% Fi_O2 threshold.

MEASUREMENTS AND MAIN RESULTS

Compared with mild-moderate ARDS, patients with moderate-severe ARDS had higher peak pressures, Pa_CO2, and pH. They also had heavier lungs, greater inhomogeneity, more noninflated tissue, and greater lung recruitability. Within 84 patients with severe ARDS (P/F < 100 mm Hg), 75% belonged to the higher Fi_O2 subgroup. They differed from the patients with severe ARDS with lower Fi_O2 only in Pa_CO2 and lung weight. Forty-one of 46 patients treated with ECMO belonged to the higher Fi_O2 group. Within this group, the patients receiving ECMO had higher Pa_CO2 than the 22 non-ECMO patients. The inhomogeneity ratio, total lung weight, and noninflated tissue were also significantly higher.

CONCLUSIONS

Using the 150-mm-Hg P/F threshold gave a more homogeneous distribution of patients with ARDS across the severity subgroups and identified two populations that differed in their anatomical and physiological characteristics. The patients treated with ECMO belonged to the severe ARDS group, and almost 90% of them belonged to the higher Fi_O2 subgroup.

Extracorporeal carbon dioxide removal for acute hypercapnic respiratory failure

In the past, the only treatment of acute exacerbations of obstructive diseases with hypercapnic respiratory failure refractory to medical treatment was invasive mechanical ventilation (IMV). Considerable technical improvements transformed extracorporeal techniques for carbon dioxide removal in an attractive option to avoid worsening respiratory failure and respiratory acidosis, and to potentially prevent or shorten the duration of IMV in patients with exacerbation of COPD and asthma. In this review, we will present a summary of the pathophysiological rationale and evidence of ECCO₂R in patients with severe exacerbations of these pathologies.

Veno-venous extracorporeal life support for blastomycosis-associated acute respiratory distress syndrome

BACKGROUND

Blastomyces is a dimorphic fungus endemic to regions of North America, which can lead to pneumonia and fatal severe acute respiratory diseases syndrome in up to 89% of patients. Extracorporeal life support can provide adequate oxygenation while allowing the lungs to rest and heal, which might be an ideal therapy in this patient group, although long-term clinical and radiological outcomes are not known.

CLINICAL FEATURES

We report on five consecutive patients admitted to Toronto General Hospital intensive care unit between January 2012 and September 2016, with progressive respiratory failure requiring veno-venous extracorporeal life support within 24-96 hours following mechanical ventilation. Ultra-lung protective mechanical ventilation was achieved within 24 hours. Recovery was the initial goal in all patients. Extracorporeal life support was provided for a prolonged period (up to 49 days), and four patients were successfully discharged from the intensive care unit. Long-term radiological assessment in three patients showed major improvement within 2 years of follow-up with some persistent disease-related changes (bronchiectasis, fibrosis, and cystic changes). In two patients, long-term functional and neuropsychological outcomes showed similar limitations to what is seen in acute respiratory distress syndrome patients who are not supported with extracorporeal life support and in acute respiratory distress syndrome patients without blastomycosis, but worse pulmonary function outcomes in the form of obstructive and restrictive changes that correlated with the radiological imaging.

CONCLUSION

Veno-venous extracorporeal life support can effectively provide prolonged support for patients with blastomycosis-associated acute respiratory distress syndrome that is safe and associated with favorable long-term outcomes.

Bacterial Biofilms on Extracorporeal Membrane Oxygenation Catheters

Despite the advantages of extracorporeal membrane oxygenation (ECMO), secondary catheter infection remains a major concern during ECMO support. In this study, to clarify the mechanism of ECMO catheter-related infection, we evaluated the impact of infection on biofilm formation on the surfaces of ECMO catheters, and we investigated clinical factors associated with biofilm formation. Catheters used for ECMO were prospectively collected aseptically from the femoral vein, internal jugular vein, and femoral artery of 81 patients with acute cardiorespiratory failure between January 2015 and October 2016. Prepared catheter sections were investigated by fluorescence microscopy, confocal scanning laser microscopy, transmission electron microscopy, and using semiquantitative culture methods. Of the 81 patients, 51 were assigned to the infection group and 30 to a control group. Biofilms were identified in 43.1% patients in the infection group, and in 20% controls (p = 0.034). Extracorporeal membrane oxygenation flow, systemic infection, and carbapenem-resistant Acinetobacter baumannii (CRAB) infection were associated with biofilm formation in a univariate analysis (odds ratio [OR]: 1.00, 95% confidence interval [CI]: 1.00-1.00, p = 0.007; OR: 3.03, 95% CI: 1.06-8.69, p = 0.039; OR: 9.60, 95% CI: 2.94-31.30, p < 0.001, respectively). However, of these factors, only CRAB infection was found to independently predict the presence of a biofilm by a multivariate logistic regression analysis (OR: 9.60, 95% CI: 2.94-31.30; p < 0.001). Biofilms were more prevalent in patients with an infection than in uninfected controls. Carbapenem-resistant A. baumannii infection was identified as an independent risk factor for biofilm formation on ECMO catheters.

Long-Term Outcomes After Extracorporeal Life Support for Acute Respiratory Failure

OBJECTIVE

This study aims to determine the prevalence of functional and psychological impairment in survivors of extracorporeal life support (ECLS) and assess the needs of survivors to guide development of an effective follow-up program.

DESIGN

This mixed-methods outcomes study used quantitative assessment via standardized instruments (Katz Index of Independence of Activities of Daily Living [Katz ADL], the Lawton Instrumental Activities of Daily Living [Lawton IADL], Hospital Anxiety and Depression Scale, and the Post Traumatic Growth Inventory) and qualitative interview to identify challenges experienced by survivors.

SETTING

A single institutional experience in an academic medical center in the United States.

PATIENTS

Patient selection targeted patients who underwent veno-venous ECLS for acute respiratory failure between January 1, 2015, and April 1, 2017. Forty-two patients (21 male, 21 female; median age of 49 years; interquartile range 36-57 years) completed the interview a median of 14.6 (interquartile range 7.7-21.1) months after ECLS decannulation.

INTERVENTIONS

This was an observational follow-up study for which no intervention was made.

MEASUREMENTS AND MAIN RESULTS

The Katz ADL and Lawton IADL revealed high independence and functionality in 62% of patients (26 of 42). Clinically significant anxiety was present in 48% (20 of 42) of patients and depression in 26% (11 of 42). There was a correlation between the number of ADL and IADL deficiencies and depression (rho 0.61, p < 0.001) and anxiety (rho 0.29, p = 0.033) subscales of the Hospital Anxiety and Depression Scale. High levels of posttraumatic growth were noted in 50% (21 of 42) of patients. Nearly all survivors noted that a clinic designed for post-ECLS follow-up would be beneficial. Patients desired access to education, improved coordination of care, and additional mental health resources.

CONCLUSIONS

This study demonstrated persistent physical and psychological impairments in survivors of ECLS. Patients consistently expressed a desire to debrief on their hospital course and receive education on possible long-term effects. Study findings suggest that structured follow-up may allow for early identification of psychological and physical impairments to improve outcomes. Future studies should focus on investigating the effect of rehabilitation and follow-up clinics in preventing these issues.

Extracellular vesicles: biomarkers and regulators of vascular function during extracorporeal circulation

Extracellular vesicles (EVs) are generated at increased rates from parenchymal and circulating blood cells during exposure of the circulation to abnormal flow conditions and foreign materials associated with extracorporeal circuits (ExCors). This review describes types of EVs produced in different ExCors and extracorporeal life support (ECLS) systems including cardiopulmonary bypass circuits, extracorporeal membrane oxygenation (ECMO), extracorporeal carbon dioxide removal (ECCO₂R), apheresis, dialysis and ventricular assist devices. Roles of EVs not only as biomarkers of adverse events during ExCor/ECLS use, but also as mediators of vascular dysfunction are explored. Manipulation of the number or subtypes of circulating EVs may prove a means of improving vascular function for individuals requiring ExCor/ECLS support. Strategies for therapeutic manipulation of EVs during ExCor/ECLS use are discussed such as accelerating their clearance, preventing their genesis or pharmacologic options to reduce or select which and how many EVs circulate. Strategies to reduce or select for specific types of EVs may prove beneficial in preventing or treating other EV-related diseases such as cancer.

The use of ECMO in ICU. Recommendations of the Spanish Society of Critical Care Medicine and Coronary Units

The use of extracorporeal membrane oxygenation systems has increased significantly in recent years; given this reality, the Spanish Society of Critical Intensive Care Medicine and Coronary Units (SEMICYUC) has decided to draw up a series of recommendations that serve as a framework for the use of this technique in intensive care units. The three most frequent areas of extracorporeal membrane oxygenation systems use in our setting are: as a cardiocirculatory support, as a respiratory support and for the maintenance of the abdominal organs in donors. The SEMICYUC appointed a series of experts belonging to the three working groups involved (Cardiological Intensive Care and CPR, Acute Respiratory Failure and Transplant work group) that, after reviewing the existing literature until March 2018, developed a series of recommendations. These recommendations were posted on the SEMICYUC website to receive suggestions from the intensivists and finally approved by the Scientific Committee of the Society. The recommendations, based on current knowledge, are about which patients may be candidates for the technique, when to start it and the necessary infrastructure conditions of the hospital centers or, the conditions for transfer to centers with experience. Although from a physiopathological point of view, there are clear arguments for the use of extracorporeal membrane oxygenation systems, the current scientific evidence is weak, so studies are needed that define more precisely which patients benefit most from the technique and when they should start.

Outcomes of extracorporeal membrane oxygenation in adult patients with hypoxemic respiratory failure refractory to mechanical ventilation

Introduction

Extracorporeal membrane oxygenation (ECMO) is a mode of extracorporeal life support that has been used to support cardiopulmonary disease refractory to conventional therapy. The experience with the use of ECMO in acute hypoxemic respiratory failure is still limited. The aim of this study was to report clinical outcomes in adult patients with acute hypoxemic respiratory failure refractory to mechanical ventilation treated with ECMO.

Methods

Between July 2011 and October 2017, 18 adult patients with hypoxemic respiratory failure refractory to mechanical ventilation were admitted to the Intensive Care Unit of an acute care tertiary hospital in Barcelona, Spain. These patients were treated with ECMO as salvage respiratory therapy. Outcomes included clinical data, ventilatory and blood gas characteristics, survival, and complications.

Results

Fifteen patients (83.3%) were previously treated in prone position. The indication of VV-ECMO was established at an early stage after a mean (SD) of 3.8 (2.5) days on mechanical ventilation. The mean duration of ECMO was 10.4 days, and 16 patients (88.9%) required venous cannulation, mostly femoral-internal jugular. The mean length of ICU stay was 27 days and the mean hospital stay was 42.1 days. The ICU survival rate was 55.5% (n = 10) and the hospital survival rate was 50% (n = 9).

Conclusions

This clinical study in a small series of ICU patients treated with ECMO confirms the usefulness of this technique as a ventilatory support in patients with refractory hypoxemic respiratory failure. However, the indication of this procedure is also committed to an ethical reflection considering the possible futility of the measure on a case-by-case basis and associated complications.

Acute life-threatening hypoxemia during mechanical ventilation

PURPOSE OF REVIEW

To describe current evidence-based practice in the management of acute life-threatening hypoxemia in mechanically ventilated patients and some of the methods used to individualize the care of the patient.

RECENT FINDINGS

Patients with acute life-threatening hypoxemia will often meet criteria for severe ARDS, for which there are only a few treatment strategies that have been shown to improve survival outcomes. Recent findings have increased our knowledge of the physiological effects of spontaneous breathing and the application of PEEP. Additionally, the use of advanced bedside monitoring has a promising future in the management of hypoxemic patients to fine-tune the ventilator and to evaluate the individual patient response to therapy.

SUMMARY

Treating the patient with acute life-threatening hypoxemia during mechanical ventilation should begin with an evidence-based approach, with the goal of improving oxygenation and minimizing the harmful effects of mechanical ventilation. The use of advanced monitoring and the application of simple maneuvers at the bedside may assist clinicians to better individualize treatment and improve clinical outcomes.

Mechanical Ventilation in Adults with Acute Respiratory Distress Syndrome. Summary of the Experimental Evidence for the Clinical Practice Guideline

RATIONALE

The American Thoracic Society/European Society for Intensive Care Medicine/Society of Critical Care Medicine guidelines on mechanical ventilation in adult patients with acute respiratory distress syndrome (ARDS) provide treatment recommendations derived from a thorough analysis of the clinical evidence on six clinical interventions. However, each of the recommendations contains areas of uncertainty and controversy, which may affect their appropriate clinical application.

OBJECTIVES

To provide a critical review of the experimental evidence surrounding the pathophysiology of ventilator-induced lung injury and to help clinicians apply the clinical recommendations to individual patients.

METHODS

We conducted a literature search and narrative review.

RESULTS

A large number of experimental studies have been performed with the aim of improving understanding of the pathophysiological effects of mechanical ventilation. These studies have formed the basis for the design of many clinical trials. Translational research has fundamentally advanced understanding of the mechanisms of ventilator-induced lung injury, thus informing the design of interventions that improve survival in patients with ARDS.

CONCLUSIONS

Because daily management of patients with ARDS presents the challenge of competing considerations, clinicians should consider the mechanism of ventilator-induced lung injury, as well as the rationale for interventions designed to mitigate it, when applying evidence-based recommendations at the bedside.

Adequacy of nutrition support during extracorporeal membrane oxygenation

BACKGROUND

The use of veno-venous extracorporeal membrane oxygenation (vv-ECMO) is increasing in adults with severe respiratory failure. Observational data suggest that there are significant challenges to providing adequate nutrition support for patients on vv-ECMO. We aimed to describe firstly the nutrition support practices in a large single-centre providing vv-ECMO to adults and secondly any association with clinical outcome.

METHODS

We conducted a retrospective review of patients receiving vv-ECMO on the Intensive Care Unit (ICU) of a large London teaching hospital. Adult patients admitted to the ICU with severe respiratory failure between December 2010 and December 2015 were included. Daily energy and protein delivery were compared with estimated targets and reasons for feeding interruptions were collected from electronic medical records. Adequate feeding was defined as 80-110% of estimated targets.

RESULTS

We analysed 203 eligible patients. Median duration of ICU stay was 21.0 (IQR, 15.0-33.0) days and vv-ECMO 10.0 (IQR, 7.0-16.0) days. Although median energy (89.8% (IQR, 80.5-96.0%)) and protein (84.7% (IQR, 74.0-96.7%)) delivery was adequate, underfeeding of either energy or protein occurred on nearly one third (28.3%) of nutrition support days. A higher admission severity of illness score was associated with inadequate protein delivery (p = 0.040). Patients with more severe organ dysfunction on the first day of vv-ECMO received inadequate energy (p = 0.026). The most common reasons for interrupted feeding were medical procedures (39.1%) followed by poor gastric motility (22.8%).

CONCLUSION

Adequate energy and protein delivery during vv-ECMO is possible but underfeeding is still common, especially in those who are more severely ill or who have more severe organ dysfunction. Patients with inadequate energy or protein delivery did not differ in ICU and 6-month survival. Prospective studies investigating optimal feeding in this patient cohort are required.

Management of Acute Respiratory Failure in the Patient with Sepsis or Septic Shock

Sepsis and septic shock are each commonly accompanied by acute respiratory failure and the need for invasive as well as non-invasive ventilation throughout a patient's intensive care unit course. We explore the underpinnings of acute respiratory failure of pulmonary as well as non-pulmonary origin in the context of invasive and non-invasive management approaches. Both pharmacologic and non-pharmacologic adjuncts to ventilatory and oxygenation support are highlighted as well. Finally, rescue modalities are positioned within the intensivist's armamentarium for global care of support of the critically ill or injured patient with sepsis or septic shock.

Intensive Care Physiotherapy during Extracorporeal Membrane Oxygenation for Acute Respiratory Distress Syndrome

RATIONALE

There are limited data on physiotherapy during extracorporeal membrane oxygenation (ECMO) for acute respiratory distress syndrome (ARDS).

OBJECTIVES

We sought to characterize physiotherapy delivered to patients with ARDS supported with ECMO, as well as to evaluate the association of this therapeutic modality with mortality.

METHODS

We conducted a retrospective cohort study of all adult patients with ARDS supported with ECMO at our institution between 2010 and 2015. The highest level of daily activity while on ECMO was coded using the ICU Mobility Scale. Through multivariable logistic regression, we evaluated the association between intensive care unit (ICU) physiotherapy and ICU mortality. In an exploratory univariate analysis, we also evaluated factors associated with a higher intensity of ICU rehabilitation while on ECMO.

MEASUREMENTS AND MAIN RESULTS

Of 107 patients who underwent ECMO, 61 (57%) had ARDS requiring venovenous ECMO. The ICU physiotherapy team was consulted for 82% (n = 50) of patients. Thirty-nine percent (n = 18) of these patients achieved an activity level of 2 or higher (active exercises in bed), and 17% (n = 8) achieved an activity level 4 or higher (actively sitting over the side of the bed). In an exploratory analysis, consultation with the ICU physiotherapy team was associated with decreased ICU mortality (odds ratio, 0.19; 95% confidence interval, 0.04-0.98). In univariate analysis, severity-of-illness factors differentiated higher-intensity and lower-intensity physiotherapy.

CONCLUSIONS

Physiotherapy during ECMO is feasible and safe when performed by an experienced team and executed in stages. Although our study suggests an association with improved ICU mortality, future research is needed to identify potential barriers, optimal timing, dosage, and safety profile.

Extracorporeal Membrane Oxygenation for Refractory Severe Respiratory Failure in Acute Interstitial Pneumonia

Acute interstitial pneumonia (AIP) is a rare idiopathic interstitial lung disease with rapid progressive respiratory failure and high mortality. In the present report, three cases of AIP complicated by refractory respiratory failure supported with extracorporeal membrane oxygenation (ECMO) are presented. One male and two female patients (ages 27-59) were included. Venovenous ECMO support was provided using miniaturized systems, with two-site femoro-jugular circuit configuration. Despite lung protective ventilation, prone position and neuromuscular blockade, refractory respiratory failure of unknown etiology supervened (ratio of arterial oxygen partial pressure to fractional inspired oxygen 46-130) and ECMO was initiated after 3-7 days of mechanical ventilation. AIP diagnosis was established after exclusion of infectious and noninfectious acute respiratory distress syndrome on the basis of clinical and analytical data, bronchoalveolar lavage analysis and lung imaging, with a confirmatory surgical lung biopsy revealing diffuse alveolar damage of unknown etiology. Immunosuppressive treatment consisted in high-dose corticosteroids and cyclophosphamide in one case. Two patients survived to hospital discharge. ECMO allowed AIP diagnosis and treatment in the presence of refractory respiratory failure, therefore reducing ventilator-induced lung injury and bridging lung recovery in two patients. ECMO referral should be considered in refractory respiratory failure if AIP is suspected.

Safety and Feasibility of Early Physical Therapy for Patients on Extracorporeal Membrane Oxygenator: University of Maryland Medical Center Experience

OBJECTIVES

To examine the feasibility and safety of mobilizing patients while on extracorporeal membranous oxygenation support.

DESIGN

Retrospective cohort study.

SETTING

Medical and Surgical ICUs in a large tertiary care hospital in the United States.

PATIENTS

Adults supported on extracorporeal membranous oxygenation from January 2014 to December 2015.

MEASUREMENTS AND MAIN RESULTS

We reviewed the medical records from physical therapy, perfusion, and intensivists to obtain the number and type of physical therapy interventions and discharge status; extracorporeal membranous oxygenation type and description of support, cannulation sites; and risk management details of adverse effects, if any. Of 254 patients supported on extracorporeal membranous oxygenation, 167 patients (66.7%) received a total of 607 physical therapy sessions while on extracorporeal membranous oxygenation support. In this cohort, 134 patients (80.2%) had at least one femoral cannula during physical therapy intervention. Sixty-six of the 167 patients (39.5%) were supported on extracorporeal membranous oxygenation with bifemoral cannulas, and 44 (26.3%) were on veno-arterial extracorporeal membranous oxygenation. A dual lumen catheter was only used in five cases. Twenty-five patients (15%) (13 bifemoral cases) participated in standing or ambulation activities. Seventy-five patients (68.8%) who were successfully weaned from extracorporeal membranous oxygenation were discharged to a rehabilitation facility; 26 patients (23.8%) went home. Three minor events (< 0.5%) involving two episodes of arrhythmias and a hypotension event interrupted the therapy sessions, but mobility activities and exercises resumed that day. No major events were reported.

CONCLUSIONS

With a highly trained multidisciplinary team and a focus on restoring function, it is feasible and safe to deliver early rehabilitation including standing and ambulation to patients on extracorporeal membranous oxygenation support even those with femoral cannulation sites with veno-arterial extracorporeal membranous oxygenation and veno-venous extracorporeal membranous oxygenation.

Oxygen Thresholds and Mortality During Extracorporeal Life Support in Adult Patients

OBJECTIVES

Extracorporeal life support can lead to rapid reversal of hypoxemia and shock; however, it can also result in varying degrees of hyperoxia. Recent data have suggested an association between hyperoxia and mortality; however, this conclusion has not been consistent across the literature. We evaluated the association between oxygenation thresholds and mortality in three cohorts of extracorporeal life support patients.

DESIGN

We performed a retrospective cohort study using the Extracorporeal Life Support Organization Registry.

SETTING

We evaluated the relationship between oxygenation measured 24 hours after extracorporeal membrane oxygenation onset and mortality (2010-2015).

PATIENTS

The extracorporeal life support cohorts were as follows: 1) veno-venous extracorporeal membrane oxygenation for respiratory failure, 2) veno-arterial extracorporeal membrane oxygenation for cardiogenic shock, and 3) extracorporeal cardiopulmonary resuscitation.

INTERVENTIONS

The relationships between hypoxemia (PaO2 < 60mm Hg), normoxia (PaO2 60-100mm Hg), moderate hyperoxia (PaO2 101-300mm Hg), extreme hyperoxia (PaO2 > 300 mm Hg), and mortality were evaluated across three extracorporeal life support cohorts.

MEASUREMENTS AND MAIN RESULTS

Seven hundred sixty-five patients underwent veno-venous extracorporeal membrane oxygenation, 775 patients underwent veno-arterial extracorporeal membrane oxygenation, and 412 underwent extracorporeal cardiopulmonary resuscitation. During veno-venous extracorporeal membrane oxygenation, hypoxemia (odds ratio, 1.68; 95% CI, 1.09-2.57) and moderate hyperoxia (odds ratio, 1.66; 95% CI, 1.11-2.50) were associated with increased mortality compared with normoxia. There was no association between oxygenation and mortality for veno-arterial extracorporeal membrane oxygenation. Moderate hyperoxia was associated with increased mortality during extracorporeal cardiopulmonary resuscitation compared with normoxia (odds ratio, 1.77; 95% CI, 1.03-3.30). An exploratory analysis did not find more specific PaO2 thresholds associated with mortality within moderate hyperoxia.

CONCLUSIONS

Moderate hyperoxia was associated with increased mortality in patients undergoing veno-venous extracorporeal membrane oxygenation for respiratory failure and extracorporeal cardiopulmonary resuscitation. Hypoxemia was associated with an increased mortality in veno-venous extracorporeal membrane oxygenation. No association was seen between oxygenation and mortality in veno-arterial extracorporeal membrane oxygenation which may be due to early death driven by the underlying disease.

A United Kingdom Register study of in-hospital outcomes of patients receiving extracorporeal carbon dioxide removal

Introduction

Extracorporeal membrane carbon dioxide removal may have a role in treatment of patients with hypercapnic respiratory failure and refractory hypoxaemia and/or hypercapnia.

Methods

We report on the use, outcomes and complications in United Kingdom intensive care units reporting patients on the Extracorporal Life Support Organisation register.

Results

Of 60 patients, 42 (70%) had primarily hypoxic respiratory failure and 18 (30%) primarily hypercapnic respiratory failure. Use of veno-venous procedures increased compared to arterio-venous procedures. Following extracorporeal membrane carbon dioxide removal, ventilatory and blood gas parameters improved at 24 h. Twenty-seven (45%) of patients died before ICU discharge, while 27 (45%) of patients were discharged alive. The most common complications related to thrombosis or haemorrhage.

Discussion

There is limited use of extracorporeal membrane carbon dioxide removal in UK clinical practice and outcomes reflect variability in indications and the technology used. Usage is likely to increase with the availability of new, simpler, technology. Further high quality evidence is needed.

Applying Precision Medicine to Trial Design Using Physiology. Extracorporeal CO2 Removal for Acute Respiratory Distress Syndrome

In clinical trials of therapies for acute respiratory distress syndrome (ARDS), the average treatment effect in the study population may be attenuated because individual patient responses vary widely. This inflates sample size requirements and increases the cost and difficulty of conducting successful clinical trials. One solution is to enrich the study population with patients most likely to benefit, based on predicted patient response to treatment (predictive enrichment). In this perspective, we apply the precision medicine paradigm to the emerging use of extracorporeal CO₂ removal (ECCO₂R) for ultraprotective ventilation in ARDS. ECCO₂R enables reductions in tidal volume and driving pressure, key determinants of ventilator-induced lung injury. Using basic physiological concepts, we demonstrate that dead space and static compliance determine the effect of ECCO₂R on driving pressure and mechanical power. This framework might enable prediction of individual treatment responses to ECCO₂R. Enriching clinical trials by selectively enrolling patients with a significant predicted treatment response can increase treatment effect size and statistical power more efficiently than conventional enrichment strategies that restrict enrollment according to the baseline risk of death. To support this claim, we simulated the predicted effect of ECCO₂R on driving pressure and mortality in a preexisting cohort of patients with ARDS. Our computations suggest that restricting enrollment to patients in whom ECCO₂R allows driving pressure to be decreased by 5 cm H₂O or more can reduce sample size requirement by more than 50% without increasing the total number of patients to be screened. We discuss potential implications for trial design based on this framework.

Fifty Years of Research in ARDS. Is Extracorporeal Circulation the Future of Acute Respiratory Distress Syndrome Management?

Mechanical ventilation (MV) remains the cornerstone of acute respiratory distress syndrome (ARDS) management. It guarantees sufficient alveolar ventilation, high Fi_O2 concentration, and high positive end-expiratory pressure levels. However, experimental and clinical studies have accumulated, demonstrating that MV also contributes to the high mortality observed in patients with ARDS by creating ventilator-induced lung injury. Under these circumstances, extracorporeal lung support (ECLS) may be beneficial in two distinct clinical settings: to rescue patients from the high risk for death associated with severe hypoxemia, hypercapnia, or both not responding to maximized conventional MV, and to replace MV and minimize/abolish the harmful effects of ventilator-induced lung injury. High extracorporeal blood flow venovenous extracorporeal membrane oxygenation (ECMO) may therefore rescue the sickest patients with ARDS from the high risk for death associated with severe hypoxemia, hypercapnia, or both not responding to maximized conventional MV. Successful venovenous ECMO treatment in patients with extremely severe H1N1-associated ARDS and positive results of the CESAR trial have led to an exponential use of the technology in recent years. Alternatively, lower-flow extracorporeal CO₂ removal devices may be used to reduce the intensity of MV (by reducing Vt from 6 to 3-4 ml/kg) and to minimize or even abolish the harmful effects of ventilator-induced lung injury if used as an alternative to conventional MV in nonintubated, nonsedated, and spontaneously breathing patients. Although conceptually very attractive, the use of ECLS in patients with ARDS remains controversial, and high-quality research is needed to further advance our knowledge in the field.

Systematic review and meta-analysis of complications and mortality of veno-venous extracorporeal membrane oxygenation for refractory acute respiratory distress syndrome

Veno-venous extracorporeal membrane oxygenation (ECMO) for refractory acute respiratory distress syndrome (ARDS) is a rapidly expanding technique. We performed a systematic review and meta-analysis of the most recent literature to analyse complications and hospital mortality associated with this technique. Using the PRISMA guidelines for systematic reviews and meta-analysis, MEDLINE and EMBASE were systematically searched for studies reporting complications and hospital mortality of adult patients receiving veno-venous ECMO for severe and refractory ARDS. Studies were screened for low bias risk and assessed for study size effect. Meta-analytic pooled estimation of study variables was performed using a weighted random effects model for study size. Models with potential moderators were explored using random effects meta-regression. Twelve studies fulfilled inclusion criteria, representing a population of 1042 patients with refractory ARDS. Pooled mortality at hospital discharge was 37.7% (CI 95% = 31.8–44.1; I² = 74.2%). Adjusted mortality including one imputable missing study was 39.3% (CI 95% = 33.1–45.9). Meta-regression model combining patient age, year of study realization, mechanical ventilation (MV) days and prone positioning before veno-venous ECMO was associated with hospital mortality (p < 0.001; R² = 0.80). Patient age (b = 0.053; p = 0.01) and maximum cannula size during treatment (b = −0.075; p = 0.008) were also independently associated with mortality. Studies reporting H1N1 patients presented inferior hospital mortality (24.8 vs 40.6%; p = 0.027). Complication rate was 40.2% (CI 95% = 25.8–56.5), being bleeding the most frequent 29.3% (CI 95% = 20.8–39.6). Mortality due to complications was 6.9% (CI 95% = 4.1–11.2). Mechanical complications were present in 10.9% of cases (CI 95% = 4.7–23.5), being oxygenator failure the most prevalent (12.8%; CI 95% = 7.1–21.7). Despite initial severity, significant portion of patients treated with veno-venous ECMO survive hospital discharge. Patient age, H1N1-ARDS and cannula size are independently associated with hospital mortality. Combined effect of patient age, year of study realization, MV days and prone positioning before veno-venous ECMO influence patient outcome, and although medical complications are frequent, their impact on mortality is limited.