Leukocyte and endothelial activation in a laboratory model of extracorporeal membrane oxygenation (ECMO)

Extracorporeal membrane oxygenation aggravates platelet glycoprotein V shedding and δ-granule deficiency in COVID-19-associated acute respiratory distress syndrome

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is a lifesaving therapy in patients with acute respiratory distress syndrome (ARDS). Hemostatic complications are frequently observed in patients on ECMO and limit the success of this therapy. Platelets are key mediators of hemostasis enabling activation, aggregation, and thrombus formation by coming in contact with exposed matrix proteins via their surface receptors such as glycoprotein (GP) VI or GPIb/V/IX. Recent research has elucidated a regulatory role of the GPV subunit. The cleaved soluble GPV (sGPV) ectodomain was identified to spatiotemporally control fibrin formation through complex formation with thrombin.

OBJECTIVES

We aimed to decipher the impact of ECMO on platelet phenotype and function, including the role of GPV and plasmatic sGPV.

METHODS

We recruited 36 patients with ARDS in the wake of COVID-19 pneumonia and performed a longitudinal comparison of platelet phenotype and function in non-ECMO (n = 23) vs ECMO (n = 13) compared with those of healthy controls. Patients were assessed at up to 3 time points (t1 = days 1-3; t2 = days 4-6; and t3 = days 7-14 after cannulation/study inclusion).

RESULTS

Agonist-induced platelet activation was assessed by flow cytometry and revealed decreased GPIIb/IIIa activation and α-granule release in all ARDS patients. During ECMO treatment, agonist-induced δ-granule release continuously decreased, which was independently confirmed by electron microscopy and was associated with a prolonged in vitro bleeding time. GPV expression on the platelet surface markedly decreased in ECMO patients compared with that in non-ECMO patients. Plasma sGPV levels were increased in ECMO patients and were associated with poor outcome.

CONCLUSION

Our data demonstrate an ECMO-intrinsic platelet δ-granule deficiency and hemostatic dysfunction beyond the underlying ARDS.

Subtypes and Mechanistic Advances of Extracorporeal Membrane Oxygenation-Related Acute Brain Injury

Extracorporeal membrane oxygenation (ECMO) is a frequently used mechanical cardiopulmonary support for rescuing critically ill patients for whom conventional medical therapies have failed. However, ECMO is associated with several complications, such as acute kidney injury, hemorrhage, thromboembolism, and acute brain injury (ABI). Among these, ABI, particularly intracranial hemorrhage (ICH) and infarction, is recognized as the primary cause of mortality during ECMO support. Furthermore, survivors often suffer significant long-term morbidities, including neurocognitive impairments, motor disturbances, and behavioral problems. This review provides a comprehensive overview of the different subtypes of ECMO-related ABI and the updated advance mechanisms, which could be helpful for the early diagnosis and potential neuromonitoring of ECMO-related ABI.

Initial Tumor Necrosis Factor-Alpha and Endothelial Activation Are Associated with Hemorrhagic Complications during Extracorporeal Membrane Oxygenation

Studies on inflammatory markers, endothelial activation, and bleeding during extracorporeal membrane oxygenation (ECMO) are lacking. Blood samples were prospectively collected after ECMO initiation from 150 adult patients who underwent ECMO for respiratory failure between 2018 and 2021. After excluding patients who died early (within 48 h), 132 patients were finally included. Their tumor necrosis factor-alpha (TNF-α), tissue factor (TF), soluble thrombomodulin (sTM), and E-selectin levels were measured. A Cox proportional hazards regression model was used to estimate the hazard ratio for hemorrhagic complications during ECMO. The 132 patients were divided into hemorrhagic (n = 23, H group) and non-complication (n = 109, N group) groups. The sequential organ failure assessment score, hemoglobin level, and ECMO type were included as covariates in all Cox models to exclude the effects of clinical factors. After adjusting for these factors, initial TNF-α, TF, sTM, E-selectin, and activated protein C levels were significantly associated with hemorrhagic complications (all p < 0.001). TNF-α, TF, and E-selectin better predicted hemorrhagic complications than the model that included only the aforementioned clinical factors (clinical factors only (area under the curve [AUC]: 0.804), reference; TNF-α (AUC: 0.914); TF (AUC: 0.915); E-selectin (AUC: 0.869)). Conclusions: TNF-α levels were significantly predictive of hemorrhagic complications during ECMO.

A Clinical-Scale Microfluidic Respiratory Assist Device with 3D Branching Vascular Networks

Recent global events such as COVID-19 pandemic amid rising rates of chronic lung diseases highlight the need for safer, simpler, and more available treatments for respiratory failure, with increasing interest in extracorporeal membrane oxygenation (ECMO). A key factor limiting use of this technology is the complexity of the blood circuit, resulting in clotting and bleeding and necessitating treatment in specialized care centers. Microfluidic oxygenators represent a promising potential solution, but have not reached the scale or performance required for comparison with conventional hollow fiber membrane oxygenators (HFMOs). Here the development and demonstration of the first microfluidic respiratory assist device at a clinical scale is reported, demonstrating efficient oxygen transfer at blood flow rates of 750 mL min⁻1 , the highest ever reported for a microfluidic device. The central innovation of this technology is a fully 3D branching network of blood channels mimicking key features of the physiological microcirculation by avoiding anomalous blood flows that lead to thrombus formation and blood damage in conventional oxygenators. Low, stable blood pressure drop, low hemolysis, and consistent oxygen transfer, in 24-hour pilot large animal experiments are demonstrated - a key step toward translation of this technology to the clinic for treatment of a range of lung diseases.

The serum proteome of VA-ECMO patients changes over time and allows differentiation of survivors and non-survivors: an observational study

BACKGROUND

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is applied in patients with refractory hemodynamic failure. Exposure of blood components to high shear stress and the large extracorporeal surfaces in the ECMO circuit trigger a complex inflammatory response syndrome and coagulopathy which are believed to worsen the already poor prognosis of these patients. Mass spectrometry-based proteomics allow a detailed characterization of the serum proteome as it provides the identity and concentration of large numbers of individual proteins at the same time. In this study, we aimed to characterize the serum proteome of patients receiving VA-ECMO.

METHODS

Serum samples were collected on day 1 and day 3 after initiation of VA-ECMO. Samples underwent immunoaffinity based depletion for the 14 most abundant serum proteins, in-solution digestion and PreOmics clean-up. A spectral library was built with multiple measurements of a master-mix sample using variable mass windows. Individual samples were measured in data independent acquisition (DIA) mode. Raw files were analyzed by DIA-neural network. Unique proteins were log transformed and quantile normalized. Differential expression analysis was conducted with the LIMMA-R package. ROAST was applied to generate gene ontology enrichment analyses.

RESULTS

Fourteen VA-ECMO patients and six healthy controls were recruited. Seven patients survived. Three hundred and fifty-one unique proteins were identified. One hundred and thirty-seven proteins were differentially expressed between VA-ECMO patients and controls. One hundred and forty-five proteins were differentially expressed on day 3 compared to day 1. Many of the differentially expressed proteins were involved in coagulation and the inflammatory response. The serum proteomes of survivors and non-survivors on day 3 differed from each other according to partial least-squares discriminant analysis (PLS-DA) and 48 proteins were differentially expressed. Many of these proteins have also been ascribed to processes in coagulation and inflammation (e.g., Factor IX, Protein-C, Kallikrein, SERPINA10, SEMA4B, Complement C3, Complement Factor D and MASP-1).

CONCLUSION

The serum proteome of VA-ECMO patients displays major changes compared to controls and changes from day 1 until day 3. Many changes in the serum proteome are related to inflammation and coagulation. Survivors and non-survivors can be differentiated according to their serum proteomes using PLS-DA analysis on day 3. Our results build the basis for future studies using mass-spectrometry based serum proteomics as a tool to identify novel prognostic biomarkers.

TRIAL REGISTRATION

DRKS00011106.

Systemic Inflammatory Response Syndrome After Extracorporeal Membrane Oxygenation Decannulation in COVID-19 Patients

INTRODUCTION

Systemic inflammatory response syndrome (SIRS) is frequently observed following decannulation from extracorporeal membrane oxygenation (ECMO). Differentiating cytokine release due to infection from endothelial injury from cannula removal and/or discontinuation from the ECMO circuit has been shown to impact treatment and outcomes. This response, however, may be complicated in COVID-19 patients due to prevalent glucocorticoid and immune modulator use. It remains unclear whether COVID-19 infection and/or associated immune modulator use impact the incidence of SIRS following decannulation.

OBJECTIVES

The aim of this study is to investigate the incidence of the SIRS phenomenon and associated outcomes in patients with COVID-19 after ECMO decannulation.

METHODS

An IRB-approved retrospective chart review of all patients who survived ECMO between June 31, 2010 and July 7, 2021 was done to identify patients who experienced SIRS within 48 hours of decannulation from ECMO support. Patients with COVID-19 were confirmed by a positive reverse transcription polymerase chain reaction (RT-PCR) assay for SARS-CoV2. SIRS was confirmed when two out of three of the following criteria were met: fever, leukocytosis, and/or initiation/escalation of vasopressors. Patients who developed post-ECMO SIRS were then distinguished based on the presence of infection. Infection was defined by the presence of either a new or positive culture following decannulation. We compared the incidence of SIRS and infection within 48 hours of decannulation in patients with and without COVID-19.

RESULTS

We identified 227 eligible patients who survived ECMO. Twenty-eight patients (12%) had COVID-19. Of these patients, ten patients with COVID-19 (36%) experienced post-ECMO SIRS, including those with true SIRS (n=3) and associated infections (n=7). Five of the ten patients with COVID-19 who experienced post-ECMO SIRS were exposed to immune modulators within two weeks of decannulation. Ninety-five (42%) patients without COVID-19 developed post-ECMO SIRS. Thirty-day survival in COVID patients who experienced post-ECMO SIRS compared to COVID patients who did not experience post-ECMO SIRS was 73% vs. 94%. (p=0.11).

CONCLUSION

Post-ECMO SIRS is common. The incidence of SIRS following decannulation was similar when historically compared to non-COVID patients who survived ECMO in a previously reported cohort from our institution. Immune-modulation exposure within two weeks of decannulation did not affect the incidence of SIRS in patients with COVID-19.

Thrombus formation during ECMO: Insights from a detailed histological analysis of thrombus composition

OBJECTIVES

Intra-device thrombosis remains one of the most common complications during extracorporeal membrane oxygenation (ECMO). Despite anticoagulation, approximately 35% of patients develop thrombi in the membrane oxygenator, pump heads, or tubing. The aim of this study was to describe the molecular and cellular features of ECMO thrombi and to study the main drivers of thrombus formation at different sites in the ECMO circuits.

APPROACH AND RESULTS

Thrombi (n = 85) were collected immediately after veno-arterial-(VA)-ECMO circuit removal from 25 patients: 23 thrombi from the pump, 25 from the oxygenator, and 37 from the tubing. Quantitative histological analysis was performed for the amount of red blood cells (RBCs), platelets, fibrin, von Willebrand factor (VWF), leukocytes, and citrullinated histone H3 (H3Cit). ECMO thrombi consist of a heterogenous composition with fibrin and VWF being the major thrombus components. A clustering analysis of the four major histological parameters identified two typical thrombus types: RBC-rich and RBC-poor/fibrin-rich thrombi with no significant differences in VWF and platelet content. Thrombus composition was not associated with the thrombus location, except for higher amounts of H3Cit that were found in pump and oxygenator thrombi compared to tubing samples. We observed higher blood leukocyte count and lactate dehydrogenase levels in patients with fibrin-rich thrombi.

CONCLUSION

We found that thrombus composition is heterogenous, independent of their location, consisting of two types: RBC-rich and a fibrin-rich types. We also found that NETs play a minor role. These findings are important to improve current anticoagulation strategies in ECMO.

The relationship between antithrombin administration and inflammation during veno-venous ECMO

Veno-venous Extracorporeal Membrane Oxygenation (ECMO) is used in the most severe cases of respiratory failure and further exacerbates the patients’ inflammatory status. Antithrombin is supplemented during ECMO for its anticoagulant effects, but it also deploys anti-inflammatory properties. In this pre-specified ancillary study of the GATRA trial [NCT03208270] we aimed to evaluate the relationship between antithrombin and inflammation during ECMO. Forty-six patients were included in the study, 23 were randomized to receive antithrombin to maintain a level of 80–120% (study group) and 23 were randomized not to be supplemented (control group). Anticoagulation was provided in both groups with heparin infusion. Six cytokines were measured at 5 timepoints from prior to ECMO start to 7 days after ECMO removal. Cytokines decreased during the study but overall were not very different in the two groups. Testing the interaction between the study group and timepoints suggests that the administration of antithrombin led to a more rapid decrease over time of IL-6, IL-1β, TNF-⍺ and Pro-ADM. Plasma levels of antithrombin (either endogenous or exogenous) were negatively associated with all cytokines. Inflammation decreases during ECMO but a causal effect of antithrombin administration on the reduction of inflammation (and its clinical relevance) must be confirmed by appropriately powered studies.

Endothelitis profile in acute heart failure and cardiogenic shock patients: Endocan as a potential novel biomarker and putative therapeutic target

Aims: Inflammation-driven endothelitis seems to be a hallmark of acute heart failure (AHF) and cardiogenic shock (CS). Endocan, a soluble proteoglycan secreted by the activated endothelium, contributes to inflammation and endothelial dysfunction, but has been scarcely explored in human AHF. We aimed to evaluate serum (S-Endocan) and urinary endocan (U-Endocan) profiles in AHF and CS patients and to correlate them with biomarkers/parameters of inflammation, endothelial activation, cardiovascular dysfunction and prognosis.

Methods: Blood and spot urine were collected from patients with AHF (n = 23) or CS (n = 25) at days 1–2 (admission), 3-4 and 5-8 and from controls (blood donors, n = 22) at a single time point. S-Endocan, U-Endocan, serum IL-1β, IL-6, tumour necrosis factor-α (S-TNF-α), intercellular adhesion molecule-1 (S-ICAM-1), vascular cell adhesion molecule-1 (S-VCAM-1) and E-selectin were determined by ELISA or multiplex immunoassays. Serum C-reactive protein (S-CRP), plasma B-type natriuretic peptide (P-BNP) and high-sensitivity troponin I (P-hs-trop I), lactate, urea, creatinine and urinary proteins, as well as prognostic scores (APACHE II, SAPS II) and echocardiographic left ventricular ejection fraction (LVEF) were also evaluated.

Results: Admission S-Endocan was higher in both patient groups, with CS presenting greater values than AHF (AHF and CS vs. Controls, p < 0.001; CS vs. AHF, p < 0.01). Admission U-Endocan was only higher in CS patients (p < 0.01 vs. Controls). At admission, S-VCAM-1, S-IL-6 and S-TNF-α were also higher in both patient groups but there were no differences in S-E-selectin and S-IL-1β among the groups, nor in P-BNP, S-CRP or renal function between AHF and CS. Neither endocan nor other endothelial and inflammatory markers were reduced during hospitalization (p > 0.05). S-Endocan positively correlated with S-VCAM-1, S-IL-6, S-CRP, APACHE II and SAPS II scores and was positively associated with P-BNP in multivariate analyses. Admission S-Endocan raised in line with LVEF impairment (p = 0.008 for linear trend).

Conclusion: Admission endocan significantly increases across AHF spectrum. The lack of reduction in endothelial and inflammatory markers throughout hospitalization suggests a perpetuation of endothelial dysfunction and inflammation. S-Endocan appears to be a biomarker of endothelitis and a putative therapeutic target in AHF and CS, given its association with LVEF impairment and P-BNP and its positive correlation with prognostic scores.

The microfluidic artificial lung: Mimicking nature's blood path design to solve the biocompatibility paradox

The increasing prevalence of chronic lung disease worldwide, combined with the emergence of multiple pandemics arising from respiratory viruses over the past century, highlights the need for safer and efficacious means for providing artificial lung support. Mechanical ventilation is currently used for the vast majority of patients suffering from acute and chronic lung failure, but risks further injury or infection to the patient's already compromised lung function. Extracorporeal membrane oxygenation (ECMO) has emerged as a means of providing direct gas exchange with the blood, but limited access to the technology and the complexity of the blood circuit have prevented the broader expansion of its use. A promising avenue toward simplifying and minimizing complications arising from the blood circuit, microfluidics-based artificial organ support, has emerged over the past decade as an opportunity to overcome many of the fundamental limitations of the current standard for ECMO cartridges, hollow fiber membrane oxygenators. The power of microfluidics technology for this application stems from its ability to recapitulate key aspects of physiological microcirculation, including the small dimensions of blood vessel structures and gas transfer membranes. An even greater advantage of microfluidics, the ability to configure blood flow patterns that mimic the smooth, branching nature of vascular networks, holds the potential to reduce the incidence of clotting and bleeding and to minimize reliance on anticoagulants. Here, we summarize recent progress and address future directions and goals for this potentially transformative approach to artificial lung support.

Inflammation and Oxidative Stress in the Context of Extracorporeal Cardiac and Pulmonary Support

Extracorporeal circulation (ECC) systems, including cardiopulmonary bypass, and extracorporeal membrane oxygenation have been an irreplaceable part of the cardiothoracic surgeries, and treatment of critically ill patients with respiratory and/or cardiac failure for more than half a century. During the recent decades, the concept of extracorporeal circulation has been extended to isolated machine perfusion of the donor organ including thoracic organs (ex-situ organ perfusion, ESOP) as a method for dynamic, semi-physiologic preservation, and potential improvement of the donor organs. The extracorporeal life support systems (ECLS) have been lifesaving and facilitating complex cardiothoracic surgeries, and the ESOP technology has the potential to increase the number of the transplantable donor organs, and to improve the outcomes of transplantation. However, these artificial circulation systems in general have been associated with activation of the inflammatory and oxidative stress responses in patients and/or in the exposed tissues and organs. The activation of these responses can negatively affect patient outcomes in ECLS, and may as well jeopardize the reliability of the organ viability assessment, and the outcomes of thoracic organ preservation and transplantation in ESOP. Both ECLS and ESOP consist of artificial circuit materials and components, which play a key role in the induction of these responses. However, while ECLS can lead to systemic inflammatory and oxidative stress responses negatively affecting various organs/systems of the body, in ESOP, the absence of the organs that play an important role in oxidant scavenging/antioxidative replenishment of the body, such as liver, may make the perfused organ more susceptible to inflammation and oxidative stress during extracorporeal circulation. In the present manuscript, we will review the activation of the inflammatory and oxidative stress responses during ECLP and ESOP, mechanisms involved, clinical implications, and the interventions for attenuating these responses in ECC.

Extracellular Vesicles Are Associated With Outcome in Veno-Arterial Extracorporeal Membrane Oxygenation and Myocardial Infarction

Background: Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is being increasingly applied in patients with circulatory failure, but mortality remains high. An inflammatory response syndrome initiated by activation of blood components in the extracorporeal circuit may be an important contributing factor. Patients with ST-elevation myocardial infarction (STEMI) may also experience a systemic inflammatory response syndrome and are at risk of developing cardiogenic shock and cardiac arrest, both indications for VA-ECMO. Extracellular vesicles (EV) are released by activated cells as mediators of intercellular communication and may serve as prognostic biomarkers. Cardiomyocyte EV, released upon myocardial ischemia, hold strong potential for this purpose. The aim of this study was to assess the EV-profile in VA-ECMO and STEMI patients and the association with outcome.

Methods: In this prospective observational study, blood was sampled on day 1 after VA-ECMO initiation or myocardial reperfusion (STEMI patients). EV were isolated by differential centrifugation. Leukocyte, platelet, endothelial, erythrocyte and cardiomyocyte (caveolin-3⁺) Annexin V⁺ EV were identified by flow cytometry. EV were assessed in survivors vs. non-survivors of VA-ECMO and in STEMI patients with normal-lightly vs. moderately-severely reduced left ventricular function. Logistic regression was conducted to determine the predictive accuracy of EV. Pearson correlation analysis of EV with clinical parameters was performed.

Results: Eighteen VA-ECMO and 19 STEMI patients were recruited. Total Annexin V⁺, cardiomyocyte and erythrocyte EV concentrations were lower (p ≤ 0.005) while the percentage of platelet EV was increased in VA-ECMO compared to STEMI patients (p = 0.002). Total Annexin V⁺ EV were increased in non-survivors of VA-ECMO (p = 0.01), and higher levels were predictive of mortality (AUC = 0.79, p = 0.05). Cardiomyocyte EV were increased in STEMI patients with moderately-severely reduced left ventricular function (p = 0.03), correlated with CK-MB_max (r = 0.57, p = 0.02) and time from reperfusion to blood sampling (r = 0.58, p = 0.01). Leukocyte EV correlated with the number of coronary stents placed (r = 0.60, p = 0.02).

Conclusions: Elevated total Annexin V⁺ EV on day 1 of VA-ECMO are predictive of mortality. Increased cardiomyocyte EV on day 1 after STEMI correlate with infarct size and are associated with poor outcome. These EV may aid in the early identification of patients at risk of poor outcome, helping to guide clinical management.

Effects of Extracorporeal Membrane Oxygenation Initiation on Oxygenation and Pulmonary Opacities

Introduction

There is limited data on the impact of extracorporeal membrane oxygenation (ECMO) on pulmonary physiology and imaging in adult patients. The current study sought to evaluate the serial changes in oxygenation and pulmonary opacities after ECMO initiation.

Methods

Records of patients started on veno-venous, or veno-arterial ECMO were reviewed (n=33; mean (SD): age 50(16) years; Male: Female 20:13). Clinical and laboratory variables before and after ECMO, including daily PaO₂ to FiO₂ ratio (PFR), were recorded. Daily chest radiographs (CXR) were prospectively appraised in a blinded fashion and scored for the extent and severity of opacities using an objective scoring system.

Results

ECMO was associated with impaired oxygenation as reflected by the drop in median PFR from 101 (interquartile range, IQR: 63-151) at the initiation of ECMO to a post-ECMO trough of 74 (IQR: 56-98) on post-ECMO day 5. However, the difference was not statistically significant. The appraisal of daily CXR revealed progressively worsening opacities, as reflected by a significant increase in the opacity score (Wilk’s Lambda statistic 7.59, p=0.001). During the post-ECMO period, a >10% increase in the opacity score was recorded in 93.9% of patients. There was a negative association between PFR and opacity scores, with an average one-unit decrease in the PFR corresponding to a +0.010 increase in the opacity score (95% confidence interval: 0.002 to 0.019, p-value=0.0162). The median opacity score on each day after ECMO initiation remained significantly higher than the pre-ECMO score. The most significant increase in the opacity score (9, IQR: -8 to 16) was noted on radiographs between pre-ECMO and forty-eight hours post-ECMO. The severity of deteriorating oxygenation or pulmonary opacities was not associated with hospital survival.

Conclusions

The use of ECMO is associated with an increase in bilateral opacities and a deterioration in oxygenation that starts early and peaks around 48 hours after ECMO initiation.

Acute Immune Response in Venoarterial and Venovenous Extracorporeal Membrane Oxygenation Models of Rats

Although experimental extracorporeal membrane oxygenation (ECMO) animal models have been reported, there are few studies on the immune response to ECMO. We developed the venoarterial (VA) and venovenous (VV) model in rats and serially investigated the changes in the distribution of immune cells. Forty rats underwent both VA and VV modes of ECMO, and blood samples were collected at 1 day before ECMO (D-1), at the end of ECMO run (D+0), and 3 days after the ECMO (D+3). Flow cytometry was used to characterize surface marker expression (CD3, CD4, CD8, CD43, CD45, CD45R, CD161, and His48) on immune cells. Granulocytes were initially activated in both ECMO types and were further reduced but not normalized until 3 days of decannulation. Monocyte and natural killer cells were decreased initially in VA mode. B lymphocytes, helper T lymphocytes, and cytotoxic T lymphocytes also significantly decreased in VA modes after ECMO, but this phenomenon was not prominent in the VV modes. Overall immune cells proportion changed after ECMO run in both modes, and the immunologic balance altered significantly in the VA than in VV mode. Our ECMO model is feasible for the hemodynamic and immunologic research, and further long-term evaluation is needed.

A DARPin targeting activated Mac-1 is a novel diagnostic tool and potential anti-inflammatory agent in myocarditis, sepsis and myocardial infarction

The monocyte β₂-integrin Mac-1 is crucial for leukocyte–endothelium interaction, rendering it an attractive therapeutic target for acute and chronic inflammation. Using phage display, a Designed-Ankyrin-Repeat-Protein (DARPin) was selected as a novel binding protein targeting and blocking the α_M I-domain, an activation-specific epitope of Mac-1. This DARPin, named F7, specifically binds to activated Mac-1 on mouse and human monocytes as determined by flow cytometry. Homology modelling and docking studies defined distinct interaction sites which were verified by mutagenesis. Intravital microscopy showed reduced leukocyte–endothelium adhesion in mice treated with this DARPin. Using mouse models of sepsis, myocarditis and ischaemia/reperfusion injury, we demonstrate therapeutic anti-inflammatory effects. Finally, the activated Mac-1-specific DARPin is established as a tool to detect monocyte activation in patients receiving extra-corporeal membrane oxygenation, as well as suffering from sepsis and ST-elevation myocardial infarction. The activated Mac-1-specific DARPin F7 binds preferentially to activated monocytes, detects inflammation in critically ill patients, and inhibits monocyte and neutrophil function as an efficient new anti-inflammatory agent.

Current Understanding of Leukocyte Phenotypic and Functional Modulation During Extracorporeal Membrane Oxygenation: A Narrative Review

A plethora of leukocyte modulations have been reported in critically ill patients. Critical illnesses such as acute respiratory distress syndrome and cardiogenic shock, which potentially require extracorporeal membrane oxygenation (ECMO) support, are associated with changes in leukocyte numbers, phenotype, and functions. The changes observed in these illnesses could be compounded by exposure of blood to the non-endothelialized surfaces and non-physiological conditions of ECMO. This can result in further leukocyte activation, increased platelet-leukocyte interplay, pro-inflammatory and pro-coagulant state, alongside features of immunosuppression. However, the effects of ECMO on leukocytes, in particular their phenotypic and functional signatures, remain largely overlooked, including whether these changes have attributable mortality and morbidity. The aim of our narrative review is to highlight the importance of studying leukocyte signatures to better understand the development of complications associated with ECMO. Increased knowledge and appreciation of their probable role in ECMO-related adverse events may assist in guiding the design and establishment of targeted preventative actions.

Influence of venovenous extracorporeal membrane oxygenation on pharmacokinetics of vancomycin in lung transplant recipients

WHAT IS KNOWN AND OBJECTIVE

The influence of venovenous extracorporeal membrane oxygenation (VV-ECMO) on the population pharmacokinetics (PPK) of vancomycin in recipients after lung transplantation (LTx) is unknown. We investigated whether VV-ECMO influences vancomycin PPK and determined optimal recommended dosage for patients after LTx.

METHODS

We tested vancomycin serum concentration and calculated PPK parameters using NONMEM. To check for any potential influence of ECMO on vancomycin PK, we compared ECMO patients with a non-ECMO patient control group, and patients before and after ECMO weaning as self-control to analysed changes in vancomycin PK. Monte Carlo dosing simulation was conducted to explore vancomycin dosing regimens.

RESULTS

Nineteen ECMO and 6 non-ECMO lung transplant recipients were enrolled. Vancomycin serum concentrations did not significantly differ between patients with and without ECMO support. Comparison of separate vancomycin population pharmacokinetic models showed that ECMO patients had smaller peripheral compartment volume of distribution (V₂ ) [Estimate (relative standard error, RSE, %) 19.7 (12) vs. 22 (17) L, P = .003] than non-ECMO patients. For treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections with MIC ≤ 0.5 µg/mL, venous infusion of 400 mg vancomycin every 8 hours was recommended. For MRSA infection with MIC ≤ 1 µg/mL, the proposed dosage was 600 mg every 8 hours.

WHAT IS NEW AND CONCLUSION

Venovenous extracorporeal membrane oxygenation slightly alters vancomycin PK but does not significantly impact vancomycin serum concentration in patients after LTx. Dose adjustment is not necessary for VV-ECMO support. Specific vancomycin dosing regimens with lower nephrotoxicity may benefit LTx recipients with VV-ECMO.

Pulmonary complications associated with veno-arterial extra-corporeal membrane oxygenation: a comprehensive review

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is a life-saving technology that provides transient respiratory and circulatory support for patients with profound cardiogenic shock or refractory cardiac arrest. Among its potential complications, VA-ECMO may adversely affect lung function through various pathophysiological mechanisms. The interaction of blood components with the biomaterials of the extracorporeal membrane elicits a systemic inflammatory response which may increase pulmonary vascular permeability and promote the sequestration of polymorphonuclear neutrophils within the lung parenchyma. Also, VA-ECMO increases the afterload of the left ventricle (LV) through reverse flow within the thoracic aorta, resulting in increased LV filling pressure and pulmonary congestion. Furthermore, VA-ECMO may result in long-standing pulmonary hypoxia, due to partial shunting of the pulmonary circulation and to reduced pulsatile blood flow within the bronchial circulation. Ultimately, these different abnormalities may result in a state of persisting lung inflammation and fibrotic changes with concomitant functional impairment, which may compromise weaning from VA-ECMO and could possibly result in long-term lung dysfunction. This review presents the mechanisms of lung damage and dysfunction under VA-ECMO and discusses potential strategies to prevent and treat such alterations.

Biomarkers of Inflammation and Lung Recovery in Extracorporeal Membrane Oxygenation Patients With Persistent Pulmonary Hypertension of the Newborn: A Feasibility Study

OBJECTIVES

Extracorporeal membrane oxygenation is a treatment for Persistent Pulmonary Hypertension of the Newborn with high mortality.

HYPOTHESIS

the extracorporeal membrane oxygenation circuit results in inflammatory responses that mitigate against successful weaning.

DESIGN

Single-center prospective observational feasibility study.

SETTING

PICU.

PATIENTS

Twenty-four neonates requiring extracorporeal membrane oxygenation support for Persistent Pulmonary Hypertension of the Newborn.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The reference outcome was death or more than 7 days of extracorporeal membrane oxygenation support. Other outcomes included serial measures of plasma-free hemoglobin and markers of its metabolism, leucocyte, platelet and endothelial activation, and biomarkers of inflammation. Of 24 participants recruited between February 2016 and June 2017, 10 died or required prolonged extracorporeal membrane oxygenation support. These patients were sicker at baseline with higher levels of plasma-free hemoglobin within 12 hours of cannulation (geometric mean ratio, 1.92; 95% CIs, 1.00-3.67; p = 0.050) but not thereafter, versus those requiring less than 7 days extracorporeal membrane oxygenation. Serum haptoglobin concentrations were significantly elevated in both groups. Patients who died or required prolonged extracorporeal membrane oxygenation support demonstrated elevated levels of platelet-leucocyte aggregation, but decreased concentrations of mediators of the inflammatory response: interleukin-8, C-reactive protein, and tumor necrosis factor α.

CONCLUSIONS

Clinical status at baseline and not levels of plasma-free hemoglobin or the systemic inflammatory response may determine the requirement for prolonged extracorporeal membrane oxygenation support in neonates.

Effect of ex vivo extracorporeal membrane oxygenation flow dynamics on immune response

BACKGROUND

Extracorporeal membrane oxygenation is a life-saving support for heart and/or lung failure patients. Despite technological advancement, abnormal physiology persists and has been associated with subsequent adverse events. These include thrombosis, bleeding, systemic inflammatory response syndrome and infection. However, the underlying mechanisms are yet to be elucidated. We aimed to investigate whether the different flow dynamics of extracorporeal membrane oxygenation would alter immune responses, specifically the overall inflammatory response, leukocyte numbers and activation/adhesion surface antigen expression.

METHODS

An ex vivo model was used with human whole blood circulating at 37°C for 6 hours at high (4 L/minute) or low (1.5 L/minute) flow dynamics, with serial blood samples taken for analysis.

RESULTS

During high flow, production of interleukin-1β (p < 0.0001), interleukin-6 (p = 0.0075), tumour necrosis factor-α (p = 0.0013), myeloperoxidase (p < 0.0001) and neutrophil elastase (p < 0.0001) were significantly elevated over time compared to low flow, in particular at 6 hours. While the remaining assessments exhibited minute changes between flow dynamics, a consistent trend of modulation in leukocyte subset numbers and phenotype was observed at 6 hours.

CONCLUSION

We conclude that prolonged circulation at high flow triggers a prominent pro-inflammatory cytokine response and activates neutrophil granule release, but further research is needed to better characterize the effect of flow during extracorporeal membrane oxygenation.

A Pilot Study Identifying Brain-Targeting Adaptive Immunity in Pediatric Extracorporeal Membrane Oxygenation Patients With Acquired Brain Injury

Supplemental Digital Content is available in the text.

Objectives:

Extracorporeal membrane oxygenation provides short-term cardiopulmonary life support, but is associated with peripheral innate inflammation, disruptions in cerebral autoregulation, and acquired brain injury. We tested the hypothesis that extracorporeal membrane oxygenation also induces CNS-directed adaptive immune responses which may exacerbate extracorporeal membrane oxygenation-associated brain injury.

Design:

A single center prospective observational study.

Setting:

Pediatric and cardiac ICUs at a single tertiary care, academic center.

Patients:

Twenty pediatric extracorporeal membrane oxygenation patients (0–14 yr; 13 females, 7 males) and five nonextracorporeal membrane oxygenation Pediatric Logistic Organ Dysfunction score matched patients

Interventions:

None.

Measurements and Main Results:

Venous blood samples were collected from the extracorporeal membrane oxygenation circuit at day 1 (10–23 hr), day 3, and day 7 of extracorporeal membrane oxygenation. Flow cytometry quantified circulating innate and adaptive immune cells, and CNS-directed autoreactivity was detected using an in vitro recall response assay. Disruption of cerebral autoregulation was determined using continuous bedside near-infrared spectroscopy and acquired brain injury confirmed by MRI. Extracorporeal membrane oxygenation patients with acquired brain injury (n = 9) presented with a 10-fold increase in interleukin-8 over extracorporeal membrane oxygenation patients without brain injury (p < 0.01). Furthermore, brain injury within extracorporeal membrane oxygenation patients potentiated an inflammatory phenotype in adaptive immune cells and selective autoreactivity to brain peptides in circulating B cell and cytotoxic T cell populations. Correlation analysis revealed a significant relationship between adaptive immune responses of extracorporeal membrane oxygenation patients with acquired brain injury and loss of cerebral autoregulation.

Conclusions:

We show that pediatric extracorporeal membrane oxygenation patients with acquired brain injury exhibit an induction of pro-inflammatory cell signaling, a robust activation of adaptive immune cells, and CNS-targeting adaptive immune responses. As these patients experience developmental delays for years after extracorporeal membrane oxygenation, it is critical to identify and characterize adaptive immune cell mechanisms that target the developing CNS.

Anticoagulation in Neonatal ECMO: An Enigma Despite a Lot of Effort!

Extracorporeal membrane oxygenation (ECMO) is a valuable modality used to support neonates, children, and adults with cardiorespiratory failure refractory to conventional therapy. It requires use of anticoagulation to prevent clotting in the extracorporeal circuit. Balancing bleeding from excessive anticoagulation with thrombotic risk remains a difficult aspect of ECMO care. Despite many advances in ECMO technology, better understanding of the coagulation cascade and new monitoring schemes to adjust anticoagulation, bleeding and thrombosis remain the most frequent complications in ECMO and are associated with morbidity and mortality. In neonates, ECMO is also complicated by the immature hemostatic system, laboratory testing norms which are not specific for neonates, lack of uniformity in management, and paucity of high-quality evidence to determine best practices. Traditional anticoagulation focuses on the use of unfractionated heparin. Direct thrombin inhibitors are also used but have not been well-studied in the neonatal ECMO population. Anticoagulation monitoring is complex and currently available assays do not take into account thrombin generation or platelet contribution to clot formation. Global assays may add valuable information to guide therapy. This review provides an overview of hemostatic alterations, anticoagulation, monitoring and management, novel anticoagulant use, and circuit modifications for neonatal ECMO. Future considerations are also presented.

Extracorporeal life support and systemic inflammation

Extracorporeal life support (ECLS) encompasses a wide range of extracorporeal modalities that offer short- and intermediate-term mechanical support to the failing heart or lung. Apart from the daily use of cardiopulmonary bypass (CPB) in the operating room, there has been a resurgence of interest and utilization of veno-arterial and veno-venous extracorporeal membrane oxygenation (VA- and VV-ECMO, respectively) and extracorporeal carbon dioxide removal (ECCO₂R) in recent years. This might be attributed to the advancement in technology, nonetheless the morbidity and mortality associated with the clinical application of this technology is still significant. The initiation of ECLS triggers a systemic inflammatory response, which involves the activation of the coagulation cascade, complement systems, endothelial cells, leukocytes, and platelets, thus potentially contributing to morbidity and mortality. This is due to the release of cytokines and other biomarkers of inflammation, which have been associated with multiorgan dysfunction. On the other hand, ECLS can be utilized as a therapy to halt the inflammatory response associated with critical illness and ICU therapeutic intervention, such as facilitating ultra-protective mechanical ventilation. In addition to addressing the impact on outcome of the relationship between inflammation and ECLS, two different but complementary pathophysiological perspectives will be developed in this review: ECLS as the cause of inflammation and ECLS as the treatment of inflammation. This framework may be useful in guiding the development of novel therapeutic strategies to improve the outcome of critical illness.

Risk factors for mortality in paediatric cardiac ICU patients managed with extracorporeal membrane oxygenation

BACKGROUND

Veno-arterial extracorporeal membrane oxygenation is frequently used in patients with cardiac disease. We evaluated short-term outcomes and identified factors associated with hospital mortality in cardiac patients supported with veno-arterial extracorporeal membrane oxygenation.

METHODS

A retrospective review of patients supported with veno-arterial extracorporeal membrane oxygenation at a university-affiliated children's hospital was performed.

RESULTS

A total of 253 patients with cardiac disease managed with extracorporeal membrane oxygenation were identified; survival to discharge was 48%, which significantly improved from 39% in an earlier era (1995-2001) (p=0.01). Patients were categorised into surgical versus non-surgical groups on the basis of whether they had undergone cardiac surgery before or not, respectively. The most common indication for extracorporeal membrane oxygenation was extracorporeal cardiopulmonary resuscitation: 96 (51%) in the surgical group and 45 (68%) in the non-surgical group. In a multiple covariate analysis, single-ventricle physiology (p=0.01), duration of extracorporeal membrane oxygenation (p&lt;0.01), and length of hospital stay (p=0.03) were associated with hospital mortality. Weekend or night shift cannulation was associated with mortality in non-surgical patients (p=0.05).

CONCLUSION

We report improvement in survival compared with an earlier era in cardiac patients supported with extracorporeal membrane oxygenation. Single-ventricle physiology continues to negatively impact survival, along with evidence of organ dysfunction during extracorporeal membrane oxygenation, duration of extracorporeal membrane oxygenation, and length of stay.

Current Understanding of How Extracorporeal Membrane Oxygenators Activate Haemostasis and Other Blood Components

Extracorporeal membrane oxygenators are used in critical care for the management of severe respiratory and cardiac failure. Activation of the coagulation system is initiated by the exposure of blood to synthetic surfaces and the shear stresses of the circuit, especially from device pumps. Initial fibrinogen deposition and subsequent activation of coagulation factors and complement allow platelets and leucocytes to adhere to oxygenator surfaces and enhance thrombin generation. These changes and others contribute to higher rates of thrombosis seen in these patients. In addition, bleeding rates are also high. Primary haemostasis is impaired by platelet dysfunction and loss of their key adhesive molecules and shear stress causes an acquired von Willebrand defect. In addition, there is also altered fibrinolysis and lastly, administration of systemic anticoagulation is required to maintain circuit patency. Further research is required to fulyl establish the complexities of the haemostatic changes with these devices, and to elucidate the mechanistic changes that are mainly responsible so that plans can be made to reduce their complications and improve management.

Effects of pumpless extracorporeal lung assist on hemodynamics, gas exchange and inflammatory cascade response during experimental lung injury

Pumpless extracorporeal lung assist (pECLA) has been reported to efficiently remove the systemic CO₂ production and provide mild to moderate oxygenation, thereby allowing for ventilator settings and modes prioritizing oxygenation and lung protection. However, an adequate bypass flow, the capacity to provide respiratory support and the effect on the inflammatory cascade response and tissue perfusion require further study to be determined. After induction of acute lung injury (ALI) by oleic acid injection, pECLA was implemented in 12 anaesthetized and mechanically ventilated dogs for 48 h. Improved oxygenation [partial oxygen pressure (PaO₂) and oxygen saturation (SaO₂) was measured by arterial blood gas analysis, and increased by 29 and 18%, respectively] and CO₂ elimination (partial CO₂ pressure decreased by 43.35%) were obtained after pECLA implementation. A maximum arterio-venous shunt flow of up to 25% of the foundational CO resulted in stable hemodynamics. The pECLA procedure did not elicit any further increase in the concentration of tumor necrosis factor-α, interleukin (IL)-6, IL-8 and endothelin-1 compared with that in the group subjected to oleic acid injection only. In addition, the pECLA procedure had no effect on lactate levels and urine production. In conclusion, pECLA is an efficient and promising strategy for providing a mild to moderate oxygenation and adequate decarboxylation, while avoiding excessive inflammatory cascade response and tissue hypoperfusion in an experimental ALI model.

Septic porcine blood does not further activate coagulation during in vitro membrane oxygenation

Objectives

For patients with a severe acute respiratory distress syndrome (ARDS), extracorporeal membrane oxygenation (ECMO) represents a life-saving measure. Frequently, patients with severe ARDS also show signs of severe sepsis. As blood contact with the membrane oxygenator surface leads to adverse effects due to insufficient biocompatibility partly caused by activation of platelets, coagulation factors and leucocytes, we hypothesized that these adverse effects would be amplified if septic blood in a preactivated state came into contact with the membrane oxygenator.

Methods

In a previously established in vitro 12-h ECMO test system (mock loop), we used septic or healthy domestic pig blood to analyse coagulation and inflammatory parameters. Sepsis was induced by a caecal ligation and puncture model in pigs.

Results

At the beginning of the mock loop experiments, the septic blood showed significantly increased thrombin-antithrombin complexes (76.9 vs 27.7 µg/l), D-dimers (1.2 vs 0.3 mg/l) and fibrinogen concentration (1.8 vs 1.5 g/l), as well as elevated extrinsic coagulation activity (shorter EXTEM-CT: 44.2 vs 57 s) and higher lactate (3.4 vs 1.5 mmol/l) and cytokine levels (interleukin-6: 827 vs 31 pg/ml) when compared with the blood from healthy animals. Despite the preactivated status of the septic blood, no further increase of coagulation activity, inflammatory response or increased oxygenator resistance was observed in comparison to the control experiments.

Conclusion

Septic porcine blood was not further activated due to the contact with an oxygenator, and no increased clot formation or biocompatibility problems were observed.

The inflammatory response to extracorporeal membrane oxygenation (ECMO): a review of the pathophysiology

Extracorporeal membrane oxygenation (ECMO) is a technology capable of providing short-term mechanical support to the heart, lungs or both. Over the last decade, the number of centres offering ECMO has grown rapidly. At the same time, the indications for its use have also been broadened. In part, this trend has been supported by advances in circuit design and in cannulation techniques. Despite the widespread adoption of extracorporeal life support techniques, the use of ECMO remains associated with significant morbidity and mortality. A complication witnessed during ECMO is the inflammatory response to extracorporeal circulation. This reaction shares similarities with the systemic inflammatory response syndrome (SIRS) and has been well-documented in relation to cardiopulmonary bypass. The exposure of a patient’s blood to the non-endothelialised surface of the ECMO circuit results in the widespread activation of the innate immune system; if unchecked this may result in inflammation and organ injury. Here, we review the pathophysiology of the inflammatory response to ECMO, highlighting the complex interactions between arms of the innate immune response, the endothelium and coagulation. An understanding of the processes involved may guide the design of therapies and strategies aimed at ameliorating inflammation during ECMO. Likewise, an appreciation of the potentially deleterious inflammatory effects of ECMO may assist those weighing the risks and benefits of therapy.

Predicting Transfusion Requirements During Extracorporeal Membrane Oxygenation

OBJECTIVE

Patients requiring extracorporeal membrane oxygenation (ECMO) have a well-known bleeding risk and the potential for experiencing possibly fatal thromboembolic complications. Risk factors and predictors of transfusion requirements during ECMO support remain uncertain. The authors hypothesized that compromised organ function immediately before ECMO support will influence transfusion requirements.

DESIGN

A prospective observational study.

SETTING

A tertiary, single-institutional university hospital.

PARTICIPANTS

The study included 40 adult patients requiring ECMO for intractable cardiac and respiratory failure between July 2010 and December 2012. Blood samples were taken before initiation of ECMO (baseline), after 24 and 48 hours on ECMO, and 24 hours after termination of ECMO.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Independent of veno-arterial or veno-venous support, 26% of patients required≥2 packed red blood cells per day (PRBC/d) and 74% of patients required<2 PRBC/d during ECMO. Requirements of≥2 PRBC/d during ECMO support were associated with higher creatinine levels and lower prothrombin times (PT, %) at baseline and with impaired platelet function after 24 hours on ECMO. Platelet function, activated by thrombin receptor-activating peptide stimulation, decreased by 30% to 40% over time on ECMO. Receiver operating characteristic curve analysis showed cut-off values for creatinine of 1.49 mg/dL (sensitivity 70%, specificity 70%; area under the curve [AUC] 0.76, 95% confidence interval [CI] 0.58-0.94), for PT of 48% (sensitivity 80%, specificity 59%; AUC 0.69, 95% CI 0.50-0.87), and for thrombin receptor-activating peptide (TRAP) 32 U (sensitivity 90%, specificity 68%; AUC 0.76, 95% CI 0.59-0.93).

CONCLUSIONS

The results of this study demonstrated that increased creatinine levels and lower PT before ECMO and secondary impaired platelet function significantly increased transfusion requirement.

Extracorporeal Membrane Oxygenation and the Kidney

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is an effective therapy for patients with reversible cardiac and/or respiratory failure. Acute kidney injury (AKI) often occurs in patients supported with ECMO; it frequently evolves into chronic kidney damage or end-stage renal disease and is associated with a reported 4-fold increase in mortality rate. Although AKI is generally due to the hemodynamic alterations associated with the baseline disease, ECMO itself may contribute to maintaining kidney dysfunction through several mechanisms.

SUMMARY

AKI may be related to conditions derived from or associated with extracorporeal therapy, leading to a reduction in renal oxygen delivery and/or to inflammatory damage. In particular, during pathological conditions requiring ECMO, the biological defense mechanisms maintaining central perfusion by a reduction of perfusion to peripheral organs (such as the kidney) have been identified as pretreatment and patient-related risk factors for AKI. Hormonal pathways are also impaired in patients supported with ECMO, leading to failures in mechanisms of renal homeostasis and worsening fluid overload. Finally, inflammatory damage, due to the primary disease, heart and lung crosstalk with the kidney or associated with extracorporeal therapy itself, may further increase the susceptibility to AKI. Renal replacement therapy can be integrated into the main extracorporeal circuit during ECMO to provide for optimal fluid management and removal of inflammatory mediators.

KEY MESSAGES

AKI is frequently observed in patients supported with ECMO. The pathophysiology of the associated AKI is chiefly related to a reduction in renal oxygen delivery and/or to inflammatory damage. Risk factors for AKI are associated with a patient's underlying disease and ECMO-related conditions.

Vancomycin population pharmacokinetics during extracorporeal membrane oxygenation therapy: a matched cohort study

Introduction

The aim of this study was to describe the population pharmacokinetics of vancomycin in critically ill patients treated with and without extracorporeal membrane oxygenation (ECMO).

Methods

We retrospectively reviewed data from critically ill patients treated with ECMO and matched controls who received a continuous infusion of vancomycin (35 mg/kg loading dose over 4 hours followed by a daily infusion adapted to creatinine clearance, CrCl)). The pharmacokinetics of vancomycin were described using non-linear mixed effects modeling.

Results

We compared 11 patients treated with ECMO with 11 well-matched controls. Drug dosing was similar between groups. The median interquartile range (IQR) vancomycin concentrations in ECMO and non-ECMO patients were 51 (28 to 71) versus 45 (37 to 71) mg/L at 4 hours; 23 (16 to 38) versus 29 (21 to 35) mg/L at 12 hours; 20 (12 to 36) versus 23 (17–28) mg/L at 24 hours (ANOVA, P =0.53). Median (ranges) volume of distribution (Vd) was 99.3 (49.1 to 212.3) and 92.3 (22.4 to 149.4) L in ECMO and non-ECMO patients, respectively, and clearance 2.4 (1.7 to 4.9) versus 2.3 (1.8 to 3.6) L/h (not significant). Insufficient drug concentrations (that is drug levels <20 mg/dL) were more common in the ECMO group. The pharmacokinetic model (non-linear mixed effects modeling) was prospectively validated in five additional ECMO-treated patients over a 6-month period. Linear regression analysis comparing the observed concentrations and those predicted using the model showed good correlation (r² of 0.67; P <0.001).

Conclusions

Vancomycin concentrations were similar between ECMO and non-ECMO patients in the early phase of therapy. ECMO treatment was not associated with significant changes in Vd and drug clearance compared with the control patients.

In-line hemofiltration minimized extracorporeal membrane oxygenation-related inflammation in a porcine model

We evaluated a pattern for connecting a hemofiltration apparatus after the ECMO oxygenator and observed the effects on the levels of inflammatory cytokines. All animals were anesthetized and ventilated, were randomly divided into 3 groups and observed for 24 h: S group (n = 6) received cannulation and heparin infusion; E group (n = 6) received venovenous (VV)-ECMO and heparin infusion; E+H group (n = 6) received hemofiltration with VV-ECMO placed after the oxygenator and heparin infusion. Hemodynamics, gas exchange parameters and plasma cytokine levels were measured simultaneously. After VV-ECMO, oxygenation was maintained in the E and E+H groups. In the E group, the levels of TNF-α, IL-1β, IL-6 and IL-8 increased markedly in the first 2-6 h and then remained stable from 12-24 h. Concentrations of TNF-α, IL-1β, IL-6 and IL-8 in the E+H group were lower than those in the E group. We concluded that the manner of connecting the hemofiltration apparatus after the oxygenator helped maintain adequate oxygenation and was easy to perform. Connecting hemofiltration to ECMO minimized the ECMO-associated effects of pro-inflammatory cytokines.

Continuous renal replacement therapy reduces the systemic and pulmonary inflammation induced by venovenous extracorporeal membrane oxygenation in a porcine model

Pulmonary changes in veno-venous extracorporeal membrane oxygenation (VV-ECMO) are rarely determined. We compared the contribution of VV-ECMO and cannulation based on the observation of pulmonary inflammatory reaction and parenchymal construction in a porcine model of low tidal volume (VT ) ventilation. We also evaluated the effect of adding continuous renal replacement therapy (CRRT) to the ECMO circuit, because CRRT is known to reduce systemic cytokine release induced by VV-ECMO. A total of 18 pigs undergoing low-VT ventilation were randomly divided into three groups (group 1, cannulation; group 2, VV-ECMO; group 3, VV-ECMO + CRRT) and studied for 24 h. Hemodynamic and ventilation parameters were recorded. We assessed plasma and alveolar cytokines, expression of pulmonary inflammatory genes, histopathological grading, and ultrastructural changes of the lungs. During the process, inspiratory volume increased and PaO2 decreased in group 1. Systemic tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6) levels increased at 2 h in group 2 and partly decreased in group 3. At 24 h, the levels of bronchoalveolar lavage fluid, TNF-α, and IL-6 in group 2 were remarkably higher than those in groups 1 and 3. Pulmonary mRNA expression of cytokines did not differ between the groups. We observed an increased score of pulmonary pathological findings in pro-inflammatory cell infiltration and interstitial thickening of the lungs in group 2. The epithelium of the blood-air barrier after VV-ECMO was swollen. In group 3, the pulmonary parenchyma and blood-air barrier were well preserved. We concluded that in a porcine model of low-VT ventilation, both VV-ECMO and VV-ECMO in combination with CRRT provided adequate oxygenation and carbon dioxide removal. Compared with VV-ECMO alone, VV-ECMO in combination with CRRT better preserved the lung parenchyma by eliminating systemic cytokines.

[Particularities of ECMO in acute respiratory distress syndrome in pediatrics]

Les techniques de circulation extracorporelle sont utilisées en pédiatrie dans les syndromes de détresse respiratoire aiguë (SDRA) les plus graves depuis les années 1980. Les données du registre international de l’Extracorporeal Life Support Organization révèlent plus 5 000 enfants placés en extracorporeal membrane oxygenation (ECMO) en 2012 avec une augmentation du nombre de cas annuels depuis l’épidémie de 2009. La survie, de 56 %, est stable alors que le nombre d’enfants avec des comorbidités augmente grâce aux améliorations apportées au matériel. Bien que nous ne disposions pas d’études randomisées, ces résultats encouragent à proposer l’ECMO dans l’arsenal thérapeutique du SDRA de l’enfant. Si les techniques veinoveineuses doivent être privilégiées dans les affections respiratoires, l’ECMO veinoartérielle peut être nécessaire et reste d’une utilisation fréquente chez l’enfant (50 % des cas). En pédiatrie, les particularités techniques sont liées d’une part aux particularités physiologiques de l’enfant et d’autre part aux contraintes dues au matériel proposé selon les différentes catégories d’âge. L’ECMO est une technique de recours lourde qui nécessite une expertise à la fois technique et pédiatrique spécialisée en raison de ce terrain particulier.

Establishment of an animal model of extracorporeal membrane oxygenation in rabbits

OBJECTIVE

This study was undertaken to establish an animal model of extracorporeal membrane oxygenation in rabbits.

METHODS

Ten New Zealand white rabbits weighing 2573±330 g were used in this study. Extracorporeal membrane oxygenation was established in these animals through cannulation of the right carotid artery and jugular vein for arterial perfusion and venous return. The components of the perfusion circuit were specially designed. Arterial blood pressure was measured with a blood pressure meter through cannulation of the right femoral artery. The heart rate and blood gas parameters were also monitored by electrocardiography and a blood gas analyzer (Radiometer ABL800, Bronshøj, Denmark), respectively.

RESULTS

The rabbit model of extracorporeal membrane oxygenation was established successfully. The hemodynamic and blood gas parameters were changed within an acceptable range during the extracorporeal membrane oxygenation process. The specially designed miniature membrane oxygenator was sufficient to meet the extracorporeal membrane oxygenation needs in this animal model.

CONCLUSION

The rabbit model of extracorporeal membrane oxygenation established through right carotid artery and jugular vein cannulation is feasible, easily operated and economical. It is an ideal model for further research of the pathophysiology and organ protection offered through the application of extracorporeal membrane oxygenation.

Usefulness of routine laboratory parameters in the decision to treat refractory cardiac arrest with extracorporeal life support

AIM

To evaluate the usefulness of routine laboratory parameters in the decision to treat refractory cardiac arrest patients with extracorporeal life support (ECLS).

METHODS

Sixty-six adults with witnessed cardiac arrest of cardiac origin unrelated to poisoning or hypothermia undergoing cardiopulmonary resuscitation without return of spontaneous circulation (duration: 155 min [120-180], median, [25-75%-percentiles]) were included in a prospective cohort-study. ECLS was implemented under cardiac massage, using a centrifugal pump connected to a hollow-fiber membrane-oxygenator, aiming to maintain ECLS flow ≥ 2.5 l/min and mean arterial pressure ≥ 60 mm Hg.

RESULTS

Forty-seven of 66 patients died within 24 h from multiorgan failure and massive capillary leak. Of 19/66 patients who survived ≥ 24 h with stable circulatory conditions permitting neurological evaluation, four became conscious and were transferred for further cardiac assistance, while three became organ donors. Ultimately, one patient survived without neurologic sequelae after cardiac transplantation. Using multivariate analysis, only pre-cannulation peripheral venous oxygen saturation (SpvO₂, 28% [15-52]) independently predicted inability to maintain targeted ECLS conditions ≥ 24 h (odds ratio for each 10%-decrease [95%-confidence interval]: 1.65 [1.21; 2.25], p=0.002). The area under the receiver-operating-characteristics curve was 0.78 [0.63; 0.93]. SpvO₂ cut-off value of 33% was associated with a sensitivity of 0.68 [0.50; 0.83] and specificity of 0.81 [0.54; 0.96]. SpvO₂ ≤ 8%, lactate concentration ≥ 21 mmol/l, fibrinogen ≤ 0.8 g/l, and prothrombin index ≤ 11% predicted premature ECLS discontinuation with a specificity of 1.

CONCLUSION

SpvO₂ is useful to predict the inability of maintaining refractory cardiac arrest victims on ECLS without detrimental capillary leak and multiorgan failure until neurological evaluation.

Plasma concentrations of inflammatory cytokines rise rapidly during ECMO-related SIRS due to the release of preformed stores in the intestine

Extracorporeal membrane oxygenation (ECMO) is a life-saving support system used in neonates and young children with severe cardiorespiratory failure. Although ECMO has reduced mortality in these critically ill patients, almost all patients treated with ECMO develop a systemic inflammatory response syndrome (SIRS) characterized by a 'cytokine storm', leukocyte activation, and multisystem organ dysfunction. We used a neonatal porcine model of ECMO to investigate whether rising plasma concentrations of inflammatory cytokines during ECMO reflect de novo synthesis of these mediators in inflamed tissues, and therefore, can be used to assess the severity of ECMO-related SIRS. Previously healthy piglets (3-week-old) were subjected to venoarterial ECMO for up to 8 h. SIRS was assessed by histopathological analysis, measurement of neutrophil activation (flow cytometry), plasma cytokine concentrations (enzyme immunoassays), and tissue expression of inflammatory genes (PCR/western blots). Mast cell degranulation was investigated by measurement of plasma tryptase activity. Porcine neonatal ECMO was associated with systemic inflammatory changes similar to those seen in human neonates. Tumor necrosis factor-alpha (TNF-alpha) and interleukin-8 (IL-8) concentrations rose rapidly during the first 2 h of ECMO, faster than the tissue expression of these cytokines. ECMO was associated with increased plasma mast cell tryptase activity, indicating that increased plasma concentrations of inflammatory cytokines during ECMO may result from mast cell degranulation and associated release of preformed cytokines stored in mast cells. TNF-alpha and IL-8 concentrations rose faster in plasma than in the peripheral tissues during ECMO, indicating that rising plasma levels of these cytokines immediately after the initiation of ECMO may not reflect increasing tissue synthesis of these cytokines. Mobilization of preformed cellular stores of inflammatory cytokines such as in mucosal mast cells may have an important pathophysiological role in ECMO-related SIRS.

Extracorporeal Therapies in the Treatment of Sepsis: Experience and Promise

Desire to restore the balance of body elements has enamored physicians since the ancient practice of bloodletting. More recently, extracorporeal techniques have been employed in both adults and children in treating sepsis. Extracorporeal therapies include continuous renal replacement (CRRT), plasma-based removal techniques, and extracorporeal membrane oxygenation (ECMO). These treatments could theoretically 1) provide immunohomeostasis of pro- and anti-inflammatory cytokines and other sepsis mediators, 2) decrease organ microthrombosis through removal of pro-coagulant factors and modulating the impaired septic coagulation response in sepsis, and 3) provide mechanical support of organ perfusion during the acute septic episode to allow time for response to traditional sepsis therapies and antimicrobials. CRRT is beneficial in managing fluid overload and acute renal failure in sepsis. Removal of sepsis mediators through the technique is variable, and the outcome impact of CRRT on sepsis has not been definitively determined. High-flow CRRT has demonstrated benefit in septic adults. Intriguing early results suggest that plasma exchange could improve outcomes in both adults and children. Based on experience, ECMO is recommended for refractory septic shock in neonates and should be considered for use in children. Ongoing trials may help determine whether the promise of extracorporeal therapies translates into outcome improvement in septic children.

Influence of Volume Replacement with Colloids versus Crystalloids in Neonates on Venoarterial Extracorporeal Membrane Oxygenation on Fluid Retention, Fluid Balance, and ECMO Runtime

In this retrospective study, we compared the effects of colloid versus crystalloid fluid replacement on the clinical signs of capillary leakage syndrome in 30 neonates with pulmonary hypertension due to meconium aspiration syndrome on venoarterial membrane oxygenation (VA-ECMO). Before 2000, 15 neonates received volume replacement with a pasteurized plasma protein solution (3.8% albumin); after 2000, 15 neonates received normal saline. Patient characteristics and pre-ECMO values did not differ between the two groups. Total fluid balance was also equal. Diuretic use was significantly higher in the colloid group (p < 0.001). The chest wall soft-tissue index was significantly higher in the crystalloid group (p < 0.005), as were the ventilator settings at the end of the ECMO runtime (p < 0.05). Serum colloid osmotic pressure, albumin, urea nitrogen, and creatinine were significantly higher in the colloid group (p < 0.0001, < 0.0001, < 0.001, and < 0.05, respectively). Duration of VA-ECMO, of artificial ventilation after ECMO treatment, and the mortality rate did not differ between the two groups. We conclude that volume replacement with crystalloids in neonates on VA-ECMO aggravated the edema in a preexisting situation of capillary leakage syndrome, whereas volume replacement with colloids could impair the kidney function.

Impact of extracorporeal membrane oxygenation modality on cytokine release during rescue from infant hypoxia

The treatment of acute respiratory failure in infants by means of extracorporeal membrane oxygenation (ECMO) is thought to be associated with a treatment-related inflammatory reaction, which may deteriorate the underlying disease process. The aim of this study was to compare the venoarterial (VA) and venovenous (VV) modality of ECMO with regard to their pulmonary and serological cytokine release during rescue from acute hypoxia. The inflammatory response was measured in piglets undergoing hypoxic ventilation with a gas mixture of 92% N2 and 8% O2, which were then rescued through VA- (n = 5) or VV-ECMO (n = 5). The effect of cannulation and anesthesia on the inflammatory response was deducted from regularly ventilated control animals (n = 5). The concentrations of the proinflammatory interleukins (IL)-1beta and IL-8 increased in the bronchoalveolar lavage fluid of all groups over a study period of 5 h but were significantly higher (P < 0.05) during VA-ECMO treatment, whereas the anti-inflammatory IL-10 concentrations were significantly higher in the bronchoalveolar lavage fluid of VV-treated animals (P < 0.001). No statistical difference between groups was found in the serum concentrations of cytokines. We conclude that in this animal model rescue from hypoxia by means of the VA modality of ECMO leads to a more pronounced inflammatory reaction of the lung than when applying the VV modality.

Complement activation by in vivo neonatal and in vitro extracorporeal membrane oxygenation

Complment activation during extracorporeal membrane oxygenation (ECMO) in newborns can be caused by both the underlying disease processes and by blood contact with the ECMO circuit. We investigated the relative importance of these mechanisms by measuring C3a, C5a and sC5b-9 before, during and after neonatal ECMO in six consecutive newborn patients using enzyme-linked immunoassay. In addition complement activation during in vitro ECMO with repeated flow of the same blood volume was measured using blood from healthy adult donors. C3a increased significantly in vivo after 1 h (from 1035+/-193 to 1865+/-419 microg/l) and in vitro ECMO (from 314+/-75 to 1962+/-1062 microg/l). C5a increased during ECMO without significant differences between in vivo and in vitro activation. In neonatal patients, sC5b-9 rose faster than in vitro, but the rapid increase was also significant for in vitro experiments (in vivo: from 328+/-63 to 1623+/-387 microg/l after 2 h; and in vitro: from 78+/-32 to 453+/-179 microg/l after 8 h). After this initial peak at 1-2 h, complement activation decreased gradually until 2-3 days after the initiation of ECMO. We conclude that in newborns the rapid activation of the complement system after the start of ECMO is predominantly caused by contact with artificial surfaces rather than the patient's underlying disease.