Oxygenator Is the Main Responsible for Leukocyte Activation in Experimental Model of Extracorporeal Circulation: A Cautionary Tale

COMPREHENSIVE CHARACTERIZATION OF CYTOKINES IN PATIENTS UNDER EXTRACORPOREAL MEMBRANE OXYGENATION: EVIDENCE FROM INTEGRATED BULK AND SINGLE-CELL RNA SEQUENCING DATA USING MULTIPLE MACHINE LEARNING APPROACHES

ABSTRACT

Background : Extracorporeal membrane oxygenation (ECMO) is an effective technique for providing short-term mechanical support to the heart, lungs, or both. During ECMO treatment, the inflammatory response, particularly involving cytokines, plays a crucial role in pathophysiology. However, the potential effects of cytokines on patients receiving ECMO are not comprehensively understood. Methods : We acquired three ECMO support datasets, namely two bulk and one single-cell RNA sequencing (RNA-seq), from the Gene Expression Omnibus (GEO) combined with hospital cohorts to investigate the expression pattern and potential biological processes of cytokine-related genes (CRGs) in patients under ECMO. Subsequently, machine learning approaches, including support vector machine (SVM), random forest (RF), modified Lasso penalized regression, extreme gradient boosting (XGBoost), and artificial neural network (ANN), were applied to identify hub CRGs, thus developing a prediction model called CRG classifier. The predictive and prognostic performance of the model was comprehensively evaluated in GEO and hospital cohorts. Finally, we mechanistically analyzed the relationship between hub cytokines, immune cells, and pivotal molecular pathways. Results : Analyzing bulk and single-cell RNA-seq data revealed that most CRGs were significantly differentially expressed; the enrichment scores of cytokine and cytokine-cytokine receptor (CCR) interaction were significantly higher during ECMO. Based on multiple machine learning algorithms, nine key CRGs (CCL2, CCL4, IFNG, IL1R2, IL20RB, IL31RA, IL4, IL7, and IL7R) were used to develop the CRG classifier. The CRG classifier exhibited excellent prognostic values (AUC > 0.85), serving as an independent risk factor. It performed better in predicting mortality and yielded a larger net benefit than other clinical features in GEO and hospital cohorts. Additionally, IL1R2, CCL4, and IL7R were predominantly expressed in monocytes, NK cells, and T cells, respectively. Their expression was significantly positively correlated with the relative abundance of corresponding immune cells. Gene set variation analysis (GSVA) revealed that para-inflammation, complement and coagulation cascades, and IL6/JAK/STAT3 signaling were significantly enriched in the subgroup that died after receiving ECMO. Spearman correlation analyses and Mantel tests revealed that the expression of hub cytokines (IL1R2, CCL4, and IL7R) and pivotal molecular pathways scores (complement and coagulation cascades, IL6/JAK/STAT3 signaling, and para-inflammation) were closely related. Conclusion : A predictive model (CRG classifier) comprising nine CRGs based on multiple machine learning algorithms was constructed, potentially assisting clinicians in guiding individualized ECMO treatment. Additionally, elucidating the underlying mechanistic pathways of cytokines during ECMO will provide new insights into its treatment.

Hemadsorption with CytoSorb®: focus on the latest experiences in cardiac surgery patients

Cardiac surgery patients are potentially exposed to an acute inflammatory host response with a huge release of both pro- and anti-inflammatory cytokines both through intrinsic (e.g., tissue damage, endothelial injury) and extrinsic (e.g., anesthesia, extracorporeal circuits) mechanisms. Current standard of care therapy includes several invasive supportive treatments such as mechanical ventilation, continuous renal replacement therapy, ECMO, and/or cardiopulmonary bypass which may be responsible for an important inflammatory response. The inflammatory cytokine levels and hemodynamic status following these artificial treatments along with the current standard therapy are not always well controlled and may lead to worsened acute clinical conditions with prolonged in-hospital length of stay and increased mortality. In these settings, the administration of hemadsorption therapy with CytoSorb® has been supported by the successful results in several clinical studies as it has shown improvement of both the inflammatory profile and the hemodynamic vascular status of the patients. Therefore, in this narrative review, we summarized and discussed the current scientific literature on the role of CytoSorb® treatment in case of cardiac surgery. According to the current evidences, the raised inflammatory levels and both inotropic and vasopressor requests in cardiac surgery patients need more tailored therapies and, in this contest, the hemadsorption with CytoSorb® could play a pivotal role, especially on heart transplant patients. Furthermore, CytoSorb is currently the only hemadsorption sorbent authorized and efficiently applied for removing anticoagulant agents such as ticagrelor or rivaroxaban in patients undergoing cardiac surgery, to reduce perioperative bleeding complications and should be considered in high-risk patients.

Validation of a new model of selective antegrade cerebral perfusion with circulatory arrest in rats

BACKGROUND

Selective antegrade cerebral perfusion (SACP) is adopted as an alternative to deep hypothermic circulatory arrest (DHCA) during aortic arch surgery. However, there is still no preclinical evidence to support the use of SACP associated with moderate hypothermia (28-30°C) instead of DHCA (18-20°C). The present study aims to develop a reliable and reproducible preclinical model of cardiopulmonary bypass (CPB) with SACP applicable for assessing the best temperature management.

MATERIALS AND METHODS

A central cannulation through the right jugular vein and the left carotid artery was performed, and CPB was instituted.Animals were randomized into two groups: normothermic circulatory arrest without or with cerebral perfusion (NCA vs SACP). EEG monitoring was maintained during CPB. After 10 min of circulatory arrest, rats underwent 60 min of reperfusion. After that, animals were sacrificed, and brains were collected for histology and molecular biology analysis.

RESULTS

Power spectral analysis of the EEG signal showed decreased activity in both cortical regions and lateral thalamus in all rats during the circulatory arrest. Only SACP determined complete recovery of brain activity and higher power spectral signal compared to NCA (p < 0.05). Histological damage scores and western blot analysis of inflammatory and apoptotic proteins like caspase-3 and Poly-ADP ribose polymerase (PARP) were significantly lower in SACP compared to NCA. Vascular endothelial growth factor (VEGF) and RNA binding protein 3 (RBM3) involved in cell-protection mechanisms were higher in SACP, showing better neuroprotection (p < 0.05).

CONCLUSIONS

SACP by cannulation of the left carotid artery guarantees good perfusion of the whole brain in this rat model of CPB with circulatory arrest. The present model of SACP is reliable, repeatable, and not expensive, and it could be used in the future to achieve preclinical evidence for the best temperature management and to define the best cerebral protection strategy during circulatory arrest.

Perioperative Changes in Plasma Nitrite and IL-6 Levels Predict Postoperative Atrial Fibrillation (POAF) and Acute Kidney Injury (AKI) after Cardiac Surgery

Background: Postoperative atrial fibrillation (POAF) and acute kidney injury (AKI) are common yet significant complications after cardiac surgery, with incidences of up to 40% for each. Here, we assessed plasma nitrite and serum interleukin-6 (IL-6) levels before and after cardiac surgery to quantify the extent to which oxidative stress and inflammation contribute to POAF and AKI occurrence. Methods: We prospectively enrolled 206 cardiac surgical patients. Plasma nitrite and serum IL-6 levels were determined preoperatively and at 24 h, 48 h and 72 h postoperatively. The patients had continuous EKG monitoring for occurrence of POAF, while daily serum creatinine was measured for determination of stage 1 + AKI. Results: Postoperatively, 78 (38%) patients experienced AF, and 47 (23%) patients experienced stage 1 + AKI. POAF analysis: Age, ACE-inhibitor use, valve surgery and percent change in baseline plasma nitrite at 24 h postoperatively were associated with POAF in multiple logistic regression analysis. The inclusion of this new biomarker significantly improved the POAF prediction model (AUC 0.77 for clinical risk factors alone, to AUC 0.81). AKI analysis: A history of diabetes mellitus was associated with AKI in multiple logistic regression analysis, and the addition of preoperative IL-6 levels improved the prediction model for AKI occurrence (AUC 0.69 to AUC 0.74). Conclusions: We previously observed selective upregulation of NADPH oxidase isoform 4 (NOX4) in patients with AF, a critical causal role of NOX4 for AF in zebrafish and a robust inhibitory effect of nitric oxide (NO) on NOX4. Our data innovatively demonstrate that a reduction in circulating nitrite levels, likely implicative of elevated NOX4-mediated oxidative stress, independently associates with POAF and improves POAF prediction, whereas the inclusion of circulating IL-6 levels improves the prediction model for AKI. Therefore, therapeutic strategies to mitigate these pathophysiological sequalae of surgical stress may reduce the incidence of severe postoperative complications of POAF and AKI.

The addition of Cytosorb in patients on VA-ECMO improves urinary output and ICU survival

INTRODUCTION

The aim of this study was to analyze the efficiency of CytoSorb adsorber in patients presenting with cardiogenic shock and treated with venoarterial extracorporeal membrane oxygenation (VA-ECMO).

METHODS

Sixteen patients put on VA ECMO due to cardiogenic shock were included, stratified according to the use of Cytosorb adsorber in the first 24 h and compared across different clinical outcomes.

RESULTS

Significantly lower vasopressor doses were required among patients treated with Cytosorb at the initiation and before weaning from ECMO. Furthermore, these patients showed significantly higher urine output before weaning and lower lactate levels during the extracorporeal support. Finally, the mortality rate was lower among the Cytosorb therapy group (22.2% vs 57.1%).

CONCLUSION

While a decrease in vasopressor doses was already associated with CytoSorb use, this is the first study showing an increase in urinary output and a trend towards better survival among patients on VA ECMO treated with CytoSorb.

Inflammatory Progression in Patients Undergoing Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is identified as a novel therapeutic strategy that offers short-term support to the metabolism of the heart and lungs in humans. Recently, the clinical centers, which provide ECMO has increased rapidly worldwide. The indications for the use of ECMO in daily clinical practice were broadened dynamically. However, even with the widespread adoption of ECMO, it still remains significant morbidity and mortality, and the underlying mechanisms are still not elucidated. Notably, one of the vital complications during ECMO was proposed as the inflammatory progression within the extracorporeal circulation. via the development of inflammatory response, patients with ECMO may further suffer from systemic inflammatory response syndrome (SIRS), posing serious risks to human health. Recently, growing evidence confirmed that through exposure of blood into the ECMO circuit could lead to the stimulation of the immune system which also facilitated the inflammatory response and systemic impaired. In the current review, the pathological development of inflammatory progression in patients with ECMO is well-listed. Furthermore, the relationship between immune-related activation and the development of inflammation is also summarized, which may further help us to decide the therapeutic strategies in daily clinical practice.

Development of an in-vitro model for extracorporeal blood pumps to study the effects of artificial pulsatility on human blood

Introduction

The application of extracorporeal circulation (ECC) systems is known to be associated with several implications regarding hemolysis, inflammation, and coagulation. In the last years, systems with pulsatile blood flow are increasingly used with the intention to improve hemodynamics in reperfusion. However, their implications on the aforementioned aspects remain largely unknown. To investigate the effects of pulsatility, this ex-vivo study was initiated.

Methods

Test circuits (primed with human whole blood) were set up in accordance with the recommendations of international standards for in-vitro evaluation of new components and systems of ECC. Diagonal pumps were either set up with non-pulsatile (n = 5, NPG) or pulsatile (n = 5, PG) pump settings and evaluated for 6 h. All analyses were conducted with human whole blood. Blood samples were repeatedly drawn from the test circuits and analyzed regarding free hemoglobin, interleukin 8 (IL-8), platelet aggregation and acquired von Willebrand syndrome (AVWS).

Results

After 1 h of circulation, a significant coagulation impairment (impaired platelet function and AVWS) was observed in both groups. After 6 h of circulation, increased IL-8 concentrations were measured in both groups (NPG: 0.05 ± 0.03 pg./mL, PG: 0.03 ± 0.01 pg./mL, p = 0.48). Pulsatile pump flow resulted in significantly increased hemolysis after 6 h of circulation (NPG: 37.3 ± 12.4 mg/100 L; PG: 59.6 ± 14.5 mg/100 L; p < 0.05).

Conclusion

Our results indicate that the coagulative impairment takes place in the early phase of ECC. Pulsatility did not affect the occurrence of AVWS ex-vivo. Prolonged durations of pulsatile pump flow led to increased hemolysis and therefore, its prolonged use should be employed cautiously in clinical practice with appropriate monitoring.

Novel Size-Variable Dedicated Rodent Oxygenator for ECLS Animal Models-Introduction of the "RatOx" Oxygenator and Preliminary In Vitro Results

The overall survival rate of extracorporeal life support (ECLS) remains at 60%. Research and development has been slow, in part due to the lack of sophisticated experimental models. This publication introduces a dedicated rodent oxygenator ("RatOx") and presents preliminary in vitro classification tests. The RatOx has an adaptable fiber module size for various rodent models. Gas transfer performances over the fiber module for different blood flows and fiber module sizes were tested according to DIN EN ISO 7199. At the maximum possible amount of effective fiber surface area and a blood flow of 100 mL/min, the oxygenator performance was tested to a maximum of 6.27 mL O₂/min and 8.2 mL CO₂/min, respectively. The priming volume for the largest fiber module is 5.4 mL, while the smallest possible configuration with a single fiber mat layer has a priming volume of 1.1 mL. The novel RatOx ECLS system has been evaluated in vitro and has demonstrated a high degree of compliance with all pre-defined functional criteria for rodent-sized animal models. We intend for the RatOx to become a standard testing platform for scientific studies on ECLS therapy and technology.

Extracorporeal Membrane Oxygenation: Set-up, Indications, and Complications

Extracorporeal membrane oxygenation (ECMO) occupies an increasingly important position in the clinic for the management of cardiac and/or pulmonary failure. As a rescue therapy, ECMO can support patients following respiratory or cardiac compromise to act as a bridge to recovery, to decision, or to transplant. This chapter reviews briefly the history of ECMO implementation as well as device modes, from veno-arterial, veno-venous, veno-arterial-venous, and veno-venous-arterial set-ups. The importance of acknowledging complications that can arise in each of these modes cannot be overlooked. Both bleeding and thrombosis are inherent risks to the use of ECMO and the existing strategies for management are reviewed. The device also elicits an inflammatory response, and the use of extracorporeal approaches can lead to infection, both of which are important to examine when reflecting how ECMO can be successfully implemented in patients. This chapter both discusses the understanding of these various complications and highlights the need for future research.

Utility of D-dimers in COVID-19 Patients Requiring Extracorporeal Membrane Oxygenation

A retrospective study was performed examining the trend of inflammatory markers, including D-dimers, in 29 COVID-19 patients requiring veno-venous (VV) extracorporeal membrane oxygenation (ECMO) support. We observed that COVID-19 patients with pre-cannulation D-dimer levels &gt;3,000 ng/mL had a significantly shorter time from admission to cannulation (4.78 vs . 8.44 days, p = 0.049) compared to those with D-dimer &lt;3,000 ng/mL. Furthermore, patients with D-dimer &gt;3,000 ng/mL had a trend of lower pH (7.24 vs . 7.33), higher pCO 2 (61.33 vs . 50.69), and higher vasoactive inotropic score (7.23 vs . 3.97) at time of cannulation, however, these were not statistically significant. This cohort of patients also required a longer duration of ECMO support (51.44 vs . 31.25 days). However, 13 patients required at least one ECMO-circuit exchange and 16 patients did not require any exchanges. There was a consistent drop in D-dimer values after every circuit exchange, which was not observed in any of the other examined inflammatory markers, including ferritin, lactate dehydrogenase, or C-reactive protein. We propose that elevated D-dimer levels (&gt;3,000 ng/mL) reflect increased disease severity in COVID-19, and predict a longer ECMO course. Once on ECMO, however, the D-Dimer level consistently decreased with every circuit exchange, which may reflect thrombus within the oxygenator rather than just disease severity.

Weighted gene co-expression identification of CDKN1A as a hub inflammation gene following cardiopulmonary bypass in children with congenital heart disease

Background

Congenital heart disease (CHD) is the most common type of birth defect. Most patients with CHD require surgery, and cardiopulmonary bypass (CPB) is the most common surgery performed.

Methods

The present study utilized weighted gene co-expression network analysis (WGCNA) to identify key inflammation genes after CPB for CHD. The GSE132176 dataset was downloaded from the Gene Expression Omnibus(GEO) database for WGCNA to identify the modules closely related to clinical traits. Disease enrichment, functional annotation and pathway enrichment were performed on genes in the module closely related to clinical traits using Enrichr and Metascape. Immune infiltration analysis was also performed on the training dataset using CIBERSORT. Finally, we identified hub genes using high gene significance (GS), high module members (MMs) and Cytoscape, and we verified the hub genes using an independent dataset and Western blot analysis.

Results

WGCNA showed that the brown module with 461 genes had the highest correlation to CHD after CPB. Functional annotation and pathway enrichment analysis were performed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, which showed that genes in the brown module were enriched in inflammation-related pathways. In the disease enrichment analysis, genes in the brown module were enriched for inflammatory diseases. After the 30 most highly associated brown intramodular genes were screened, a protein-protein interaction network was constructed using the STRING online analysis website. The protein-protein interaction results were then calculated using 12 algorithms in the cytoHubba plugin of Cytoscape software. The final result showed that CDKN1A was the fundamental gene of post-CPB for CHD. Using another independent validation dataset (GSE12486), we confirmed that CDKN1A was significantly differentially expressed between preoperative and postoperative CPB (Wilcoxon, P = 0.0079; T-test, P = 0.006). In addition, CDKN1A expression was elevated in eosinophils, neutrophils, memory CD4 T cells and activated mast cells. Western blot analysis showed that the expression of CDKN1A protein was significantly higher postoperative CPB than preoperative CPB. Moreover, CDKN1A was mainly related to inflammation.

Conclusion

In summary, we found a relationship between CDKN1A and inflammation after CPB for congenital heart disease by WGCNA, experiments and various bioinformatics methods. Thus, CDKN1A maybe serve as a biomarker or therapeutic target for accurate diagnosis and treatment of inflammation after CPB in the future.

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.

Systemic inflammatory response during cardiopulmonary bypass: Axial flow versus radial flow oxygenators

BACKGROUND

The objective of this study was to investigate the inflammatory effects of different oxygenator flow pattern types in patients undergoing coronary artery bypass graft surgery with cardiopulmonary bypass.

METHODS

We designed this randomized, single-blind, prospective study of patients with coronary artery disease. We compared the systemic inflammatory effects of oxygenators with two types of flow: axial flow and radial flow. Therefore, we divided the patients into two groups: 24 patients in the axial group and 28 patients in the radial group. IL-1, IL-6, IL-10, and TNF-α were examined for cytokine activation leading to a systemic inflammatory reaction. The samples were collected at three different time intervals: T1, T2, and T3 (T1 was taken before cardiopulmonary bypass, T2 just 1 h after CPB onset, and T3 was taken 24 h after the surgery).

RESULTS

There were no significant differences in demographic characteristics between the two groups. We observed that there were notably lower levels of humoral inflammatory response parameters (IL-1, IL-6, and TNF-α) in the radial flow oxygenator group than in the axial flow group at the specific sampling times. For IL-10, there was no significant difference for any time period.

CONCLUSION

It might be advantageous to use a radial-flow-patterned oxygenator to limit the inflammatory response triggered by the oxygenators in cardiopulmonary bypass.

Nitric Oxide in Selective Cerebral Perfusion Could Enhance Neuroprotection During Aortic Arch Surgery

Background

Hypothermic circulatory arrest (HCA) in aortic arch surgery has a significant risk of neurological injury despite the newest protective techniques and strategies. Nitric oxide (NO) could exert a protective role, reduce infarct area and increase cerebral perfusion. This study aims to investigate the possible neuroprotective effects of NO administered in the oxygenator of selective antegrade cerebral perfusion (SCP) during HCA.

Methods

Thirty male SD adult rats (450–550 g) underwent cardiopulmonary bypass (CPB), cooling to 22°C body core temperature followed by 30 min of HCA. Rats were randomized to receive SCP or SCP added with NO (20 ppm) administered through the oxygenator (SCP-NO). All animals underwent CPB-assisted rewarming to a target temperature of 35°C in 60 min. At the end of the experiment, rats were sacrificed, and brain collected. Immunofluorescence analysis was performed in blind conditions.

Results

Neuroinflammation assessed by allograft inflammatory factor 1 or ionized calcium-binding adapter molecule 1 expression, a microglia activation marker was lower in SCP-NO compared to SCP (4.11 ± 0.59 vs. 6.02 ± 0.18%; p < 0.05). Oxidative stress measured by 8oxodG, was reduced in SCP-NO (0.37 ± 0.01 vs. 1.03 ± 0.16%; p < 0.05). Brain hypoxic area extent, analyzed by thiols oxidation was attenuated in SCP-NO (1.85 ± 0.10 vs. 2.74 ± 0.19%; p < 0.05). Furthermore, the apoptotic marker caspases 3 was significantly reduced in SCP-NO (10.64 ± 0.37 vs. 12.61 ± 0.88%; p < 0.05).

Conclusions

Nitric oxide administration in the oxygenator during SCP and HCA improves neuroprotection by decreasing neuroinflammation, optimizing oxygen delivery by reducing oxidative stress and hypoxic areas, finally decreasing apoptosis.

A Review of Pulmonary Arterial Hypertension Treatment in Extracorporeal Membrane Oxygenation: A Case Series of Adult Patients

BACKGROUND

Little data is published describing the use of medications prescribed for pulmonary arterial hypertension (PAH) in patients receiving extracorporeal membrane oxygenation (ECMO). Even though many patients with PAH may require ECMO as a bridge to transplant or recovery, little is reported regarding the use of PAH medications in this setting.

METHODS

This retrospective case series summarizes the clinical experience of 8 patients with PAH receiving ECMO and reviews medication management in the setting of ECMO.

RESULTS

Eight PAH patients, 5 of whom were female, ranging in age from 21 to 61 years old, were initiated on ECMO. Veno-arterial (VA) ECMO was used in 4 patients, veno-venous (VV) ECMO and hybrid ECMO configurations in 2 patients respectively. Common indications for ECMO included cardiogenic shock, bridge to transplant, and cardiac arrest. All patients were on intravenous (IV) prostacyclin therapy at baseline. Refractory hypotension was noted in 7 patients of whom 5 patients required downtitration or discontinuation of baseline PAH therapies. Three patients had continuous inhaled epoprostenol added during their time on ECMO. In patients who were decannulated from ECMO, PAH therapies were typically resumed or titrated back to baseline dosages. One patient required no adjustment in PAH therapy while on ECMO. Two patients were not able to be decannulated from ECMO.

CONCLUSION

The treatment of critically ill PAH patients is challenging given a variety of factors that could affect PAH drug concentrations. In particular, PAH patients on prostacyclin analogues placed on VA ECMO appear to have pronounced systemic vasodilation requiring vasopressors which is alleviated by temporarily reducing the intravenous prostacyclin dose. Patients should be closely monitored for potential need for rapid titrations in prostacyclin therapy to maintain hemodynamic stability.

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.

Increased Intracranial Hemorrhage Amid Elevated Inflammatory Markers in Those With COVID-19 Supported With Extracorporeal Membrane Oxygenation

ABSTRACT

COVID-19-related coagulopathy is a known complication of SARS-CoV-2 infection and can lead to intracranial hemorrhage (ICH), one of the most feared complications of extracorporeal membrane oxygenation (ECMO). We sought to evaluate the incidence and etiology of ICH in patients with COVID-19 requiring ECMO. Patients at two academic medical centers with COVID-19 who required venovenous-ECMO support for acute respiratory distress syndrome (ARDS) were evaluated retrospectively. During the study period, 33 patients required ECMO support; 16 (48.5%) were discharged alive, 13 died (39.4%), and 4 (12.1%) had ongoing care. Eleven patients had ICH (33.3%). All ICH events occurred in patients who received intravenous anticoagulation. The ICH group had higher C-reactive protein (P = 0.04), procalcitonin levels (P = 0.02), and IL-6 levels (P = 0.05), lower blood pH before and after ECMO (P < 0.01), and higher activated partial thromboplastin times throughout the hospital stay (P < 0.0001). ICH-free survival was lower in COVID-19 patients than in patients on ECMO for ARDS caused by other viruses (49% vs. 79%, P = 0.02). In conclusion, patients with COVID-19 can be successfully bridged to recovery using ECMO but may suffer higher rates of ICH compared to those with other viral respiratory infections.

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.

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.

Mechanical circulatory support in paediatric population

Extra-corporeal membrane oxygenation is a life-saving modality to support the cardiac and/or pulmonary system as a form of life support in resuscitation, post-cardiotomy, as a bridge to cardiac transplantation and in respiratory failure. Its use in the paediatric and neonatal population has proven incredibly useful. However, extra-corporeal membrane oxygenation is also associated with a greater rate of mortality and complications, particularly in those with co-morbidities. As a result, interventions such as ventricular assist devices have been trialled in these patients. In this review, we provide a comprehensive analysis of the current literature on extra-corporeal membrane oxygenation for cardiac support in the paediatric and neonatal population. We evaluate its effectiveness in comparison to other forms of mechanical circulatory support and focus on areas for future development.

The effect of hyperoxia on inflammation and platelet responses in an ex vivo extracorporeal membrane oxygenation circuit

Use of extracorporeal membrane oxygenation (ECMO) is expanding, however, it is still associated with significant morbidity and mortality. Activation of inflammatory and innate immune responses and hemostatic alterations contribute to complications. Hyperoxia may play a role in exacerbating these responses. Nine ex vivo ECMO circuits were tested using fresh healthy human whole blood, with two oxygen levels: 21% inspired fraction of oxygen (FiO₂ ; mild hyperoxia; n = 5) and 100% FiO₂ (severe hyperoxia; n = 4). Serial blood samples were taken for analysis of platelet aggregometry, leukocyte activation, inflammatory, and oxidative stress markers. ECMO resulted in reduced adenosine diphosphate- (P < .05) and thrombin receptor activating peptide-induced (P < .05) platelet aggregation, as well as increasing levels of the neutrophil activation marker, neutrophil elastase (P = .013). Additionally, levels of the inflammatory chemokine interleukin-8 were elevated (P < .05) and the activity of superoxide dismutase, a marker of oxidative stress, was increased (P = .002). Hyperoxia did not augment these responses, with no significant differences detected between mild and severe hyperoxia. Our ex vivo model of ECMO revealed that the circuit itself triggers a pro-inflammatory and oxidative stress response, however, exposure to supra-physiologic oxygen does not amplify that response. Extended-duration studies and inclusion of an endothelial component could be beneficial in characterizing longer term changes.

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.

Cardioprotective Effects of Sphingosine-1-Phosphate Receptor Immunomodulator FTY720 in a Clinically Relevant Model of Cardioplegic Arrest and Cardiopulmonary Bypass

Objective: FTY720, an immunomodulator derived from sphingosine-1-phosphate, has recently demonstrated its immunomodulatory, anti-inflammatory, anti-oxidant, anti-apoptotic and anti-inflammatory properties. Furthermore, FTY720 might be a key pharmacological target for preconditioning. In this preclinical model, we have investigated the effects of FTY720 on myocardium during reperfusion in an experimental model of cardioplegic arrest (CPA) and cardiopulmonary bypass.

Methods: 30 Sprague–Dawley rats (300–350 g) were randomized into two groups: Group-A, treated with FTY720 1 mg/kg via intravenous cannulation, and Group-B, as control. After 15 min of treatment, rats underwent CPA for 30 min followed by initiation of extracorporeal life support for 2 h. Support weaning was done, and blood and myocardial tissues were collected for analysis. Hemodynamic parameters, inflammatory mediators, nitro-oxidative stress, neutrophil infiltration, immunoblotting analysis, and immunohistochemical staining were analyzed and compared between groups.

Results: FTY720 treatment activated the Akt/Erk1/2 signaling pathways, reduced the level of inflammatory mediators, activated antiapoptotic proteins, and inhibited proapoptotic proteins, leading to reduced nitro-oxidative stress and cardiomyocyte apoptosis. Moreover, significant preservation of high-energy phosphates were observed in the FTY720-treated group. This resulted in improved recovery of left ventricular systolic and diastolic functions.

Conclusion: The cardioprotective mechanism in CPA is associated with activation of prosurvival cell signaling pathways that prevents myocardial damage. FTY720 preserves high-energy phosphates attenuates myocardial inflammation and oxidative stress, and improves cardiac function.

Oxidative Stress and Neonatal Respiratory Extracorporeal Membrane Oxygenation

Oxidative stress is a frequent condition in critically ill patients, especially if exposed to extracorporeal circulation, and it is associated with worse outcomes and increased mortality. The inflammation triggered by the contact of blood with a non-endogenous surface, the use of high volumes of packed red blood cells and platelets transfusion, the risk of hyperoxia and the impairment of antioxidation systems contribute to the increase of reactive oxygen species and the imbalance of the redox system. This is responsible for the increased production of superoxide anion, hydrogen peroxide, hydroxyl radicals, and peroxynitrite resulting in increased lipid peroxidation, protein oxidation, and DNA damage. The understanding of the pathophysiologic mechanisms leading to redox imbalance would pave the way for the future development of preventive approaches. This review provides an overview of the clinical impact of the oxidative stress during neonatal extracorporeal support and concludes with a brief perspective on the current antioxidant strategies, with the aim to focus on the potential oxidative stress-mediated cell damage that has been implicated in both short and long-term outcomes.

The neutrophil to lymphocyte ratio in patients supported with extracorporeal membrane oxygenation

INTRODUCTION

The neutrophil to lymphocyte ratio (NLR) has proven to be a robust predictor of mortality in a wide range of cardiovascular diseases. This study investigated the predictive value of the NLR in patients supported by extracorporeal membrane oxygenation (ECMO) systems.

METHODS

This study included 107 patients who underwent ECMO implantation for cardiogenic shock. Median preoperative NLR was used to divide the cohort, with Group 1 NLR <14.2 and Group 2 with NLR ≥14.2. Survival, the primary outcome, was compared between groups.

RESULTS

The study cohort was composed of 64 (60%) males with an average age 53.1 ± 14.9 years. Patients in Group 1 had an average NLR of 7.5 ± 3.5 compared to 27.1 ± 19.9 in Group 2. Additionally, those in Group 2 had significantly higher preoperative blood urea nitrogen (BUN) and age. Survival analysis indicated a thirty-day survival of 56.2%, with significantly worsened mortality in patients with NLR greater than 14.2, p=0.047.

DISCUSSION

Our study shows the NLR has prognostic value in patients undergoing ECMO implantation. Leukocytes are known contributors to myocardial damage and neutrophil infiltration is associated with damage caused by myocardial ischemia.

Towards a Biohybrid Lung Assist Device: N-Acetylcysteine Reduces Oxygen Toxicity and Changes Endothelial Cells' Morphology

The development of an endothelialized membrane oxygenator requires solution strategies combining the knowledge of oxygenators with endothelial cells' biology. Since it is well known that exposing cells towards pure oxygen causes oxidative stress, this aspect has to be taken into account in the development of a biohybrid oxygenator system. N-Acetylcysteine (NAC) is known for its antioxidant properties in cells. We tested its applicability for the development of an endothelialized oxygenator model. Cultivating human umbilical vein derived endothelial cells (HUVEC) up to 6 days with increasing concentrations of NAC from 1 to 30 mM revealed NAC toxicity at concentrations from 20 mM. Cell density clearly decreased after radical oxygen species exposure in non-NAC pretreated cells compared to 20 mM NAC precultured HUVEC after 3 and 6 days. Also the survival rate after ROS treatment could be restored by incubation with NAC from 15 to 25 mM for all time points. NAC treated cells changed their morphology from typical endothelial cells' cobblestone pattern to a fusiform, elongated configuration. Transformed cells were still positive for typical endothelial cell markers. Our present results show the potential of NAC for the protection of an endothelial cell layer in an endothelialized membrane oxygenator due to its antioxidative properties. Moreover, NAC induces a morphological change in HUVEC similar to dynamic cultivation procedures.

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.

Significantly reduced adsorption and activation of blood components in a membrane oxygenator system coated with crosslinkable zwitterionic copolymer

A crosslinkable zwitterionic copolymer PMBT was coated onto the surfaces of polypropylene hollow fiber membrane (PP-HFM) oxygenator and its connecting tubes. The PMBT copolymer coating on the oxygenator circuit formed a cell outer membrane mimetic surface with excellent stability. The hemocompatibility of the PMBT copolymer coated PP-HFM oxygenator circuit was evaluated by animal extracorporeal circulation. The concentrations of clotting components fibrinogen and platelet in the blood were almost unchanged during the circulation through the PMBT copolymer coated oxygenator circuits. By contrast, the concentrations of fibrinogen and platelet were significantly reduced to 52% and 56% respectively in the uncoated oxygenator group due to adsorption and thrombogenesis of the blood during 2h circulation. Moreover, concentration of activation marker beta-thromboglobulin for platelet in the blood was remarkably lower in the PMBT group than the uncoated control group (p<0.01). All the results strongly supported that the hemocompatibility of the PP-HFM oxygenator circuit could be improved significantly by coating a stable and densely assembled zwitterionic polymer film. This simple, stable and highly effective cell membrane mimetic coating strategy may be applicable in developing advanced oxygenator systems and other artificial organs.

STATEMENT OF SIGNIFICANCE

Although a number of studies have reported the fabrication of zwitterionic phosphorylcholine coated oxygenators to resist the adsorption and activation of blood components and eliminate heparin-induced thrombocytopenia, none of them have fabricated stable and densely assembled film, especially with crosslinkable amphiphilic random copolymer described in our manuscript. The novel features of our work include.