The mechanisms of platelet dysfunction during extracorporeal membrane oxygenation in critically ill neonates

Extracorporal Membrane Oxygenation in Massive Pulmonary Embolism

BACKGROUND

Massive pulmonary embolism (MPE) carries significant 30-day mortality risk, and a change in societal guidelines has promoted the increasing use of extracorporeal membrane oxygenation (ECMO) in the immediate management of MPE-associated cardiovascular shock. This narrative review examines the current status of ECMO in MPE.

METHODS

A literature review was performed from 1982 to 2022 searching for the terms "Pulmonary embolism" and "ECMO," and the search was refined by examining those publications that covered MPE.

RESULTS

In the patient with MPE, veno-arterial ECMO is now recommended as a bridge to interventional therapy. It can reliably decrease right ventricular overload, improve RV function, and allow hemodynamic stability and restoration of tissue oxygenation. The use of ECMO in MPE has been associated with lower mortality in registry reviews, but there has been no significant difference in outcomes between patients treated with and without ECMO in meta-analyses. Applying ECMO is also associated with substantial multisystem morbidity due to systemic inflammatory response, bleeding with coagulopathy, hemorrhagic stroke, renal dysfunction, and acute limb ischemia, which must be factored into the outcomes.

CONCLUSIONS

The application of ECMO in MPE should be combined with an aggressive interventional pulmonary interventional program and should strictly adhere to the current selection criteria.

Patient-tailored platelet transfusion practices for children supported by extracorporeal membrane oxygenation

BACKGROUND AND OBJECTIVES

Extracorporeal membrane oxygenation (ECMO) serves as cardiopulmonary therapy in critically ill patients with respiratory/heart failure and often necessitates multiple blood product transfusions. The administration of platelet transfusions during ECMO is triggered by the presence or risk of significant bleeding. Most paediatric ECMO programmes follow guidelines that recommend a platelet transfusion threshold of 80-100 × 109/L. To reduce exposure to platelets, we developed a practice to dynamically lower the threshold to ~20 × 109/L. We describe our experience with patient-tailored platelet thresholds and related bleeding outcomes.

MATERIALS AND METHODS

We retrospectively evaluated our platelet transfusion policy, bleeding complications and patient outcome in 229 ECMO-supported paediatric patients in our unit.

RESULTS

We found that more than 97.4% of patients had a platelet count <100 × 109/L at some point during their ECMO course. Platelets were transfused only on 28.5% of ECMO days; and 19.2% of patients never required a platelet transfusion. The median lowest platelet count in children who had bleeding events was 25 × 109/L as compared to 33 × 109/L in children who did not bleed (p < 0.001). Our patients received fewer platelet transfusions and did not require more red blood cell transfusions, nor did they experience more haemorrhagic complications.

CONCLUSION

We have shown that a restrictive, 'patient-tailored' rather than 'goal-directed' platelet transfusion policy is feasible and safe, which can greatly reduce the use of platelet products. Although there was a difference in the lowest platelet counts in children who bled versus those who did not, the median counts were much lower than current recommendations.

Impact of thrombocytopenia on short-term outcomes in patients undergoing mobile extracorporeal membrane oxygenation support

INTRODUCTION

The prolonged use of extracorporeal membrane oxygenation (ECMO) support is associated with increased consumption of platelets and hemolysis. The prognostic impact of thrombocytopenia prior to and during ECMO support on patient's short-, mid- and long-term outcomes has been critically evaluated and discussed over the last years. However, only few data have been published on thrombocytopenia caused by mobile ECMO support. The aim of this study was to evaluate the impact of thrombocytopenia on short-term outcomes and predictors of in-hospital mortality in patients supported by mobile ECMO for transportation and subsequent weaning in a tertiary centre.

METHODS

This retrospective single-centre study analyzed a total of 117 patients requiring mobile veno-arterial (va) ECMO support and subsequent transportation from referral hospitals to our department from January 2015 until December 2021. A total of 15 patients had to be excluded from the analysis for missing data regarding baseline platelet count. Patients were divided into two groups: thrombocytopenia group (<130 × 109/L, n = 44) and non-thrombocytopenia group (≥130 × 109/L, n = 58). The primary outcome was in-hospital mortality. Secondary outcomes were successful ECMO-weaning, and the incidence of associated complications (bleeding, acute hepatic failure, acute renal failure, dialysis, and septic shock).

RESULTS

The dialysis rate before ECMO initiation was significantly higher (p = .041) in the thrombocytopenia group compared to the non-thrombocytopenia group. The rates of bleeding complications (p = .032) and limb ischemia (p = .003) were significantly higher in patients with low platelet count. Moreover, complication rates of acute hepatic failure (p < .001), acute renal failure (p < .001) and dialysis (p = .033) were significantly higher in the thrombocytopenia group. Also, in-hospital mortality was significantly higher (p = .002) in patients with low platelet count before initiation of ECMO support.

CONCLUSION

Based on the results of the present study, patients with thrombocytopenia prior to mobile vaECMO support may be at significantly higher risk for associated complications and short-term mortality.

The Ways of the Virus: Interactions of Platelets and Red Blood Cells with SARS-CoV-2, and Their Potential Pathophysiological Significance in COVID-19

The hematological effects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are important in COVID-19 pathophysiology. However, the interactions of SARS-CoV-2 with platelets and red blood cells are still poorly understood. There are conflicting data regarding the mechanisms and significance of these interactions. The aim of this review is to put together available data and discuss hypotheses, the known and suspected effects of the virus on these blood cells, their pathophysiological and diagnostic significance, and the potential role of platelets and red blood cells in the virus's transport, propagation, and clearance by the immune system. We pay particular attention to the mutual activation of platelets, the immune system, the endothelium, and blood coagulation and how this changes with the evolution of SARS-CoV-2. There is now convincing evidence that platelets, along with platelet and erythroid precursors (but not mature erythrocytes), are frequently infected by SARS-CoV-2 and functionally changed. The mechanisms of infection of these cells and their role are not yet entirely clear. Still, the changes in platelets and red blood cells in COVID-19 are significantly associated with disease severity and are likely to have prognostic and pathophysiological significance in the development of thrombotic and pulmonary complications.

Transfusion in Neonatal Extracorporeal Membrane Oxygenation: A Best Practice Review

Extracorporeal Membrane Oxygenation (ECMO) is an important tool for managing critically ill neonates. Bleeding and thrombotic complications are common and significant. An understanding of ECMO physiology, its interactions with the unique neonatal hemostatic pathways, and appreciation for the distinctive risks and benefits of neonatal transfusion as it applies to ECMO are required. Currently, there is variability regarding transfusion practices, related to changing norms and a lack of high-quality literature and trials. This review provides an analysis of the neonatal ECMO transfusion literature and summarizes available best practice guidelines.

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.

Role of Matrix Metalloproteinase-2 in the Development of Atherosclerosis among Patients with Coronary Artery Disease

Coronary artery disease (CAD) is a caused by atherosclerotic plaque buildup in the coronary arteries that supply blood and oxygen to the heart. Matrix metalloproteinase (MMP) is a family of zinc-dependent endopeptidase that is involved in various stages of atherosclerosis as demonstrated in in vitro and in vivo studies. MMP-2 is associated with both stable and unstable atherosclerotic plaque formation. The current review aimed to identify the role of MMP-2 in atherosclerosis development among CAD patients. Literature search was conducted through four online databases and only studies that were published from 2018 until February 2023 were included. The risk of bias was assessed by using the Newcastle-Ottawa Scale. A total of 10,622 articles were initially identified, and only eight studies that fulfilled the selection criteria were included in this review. The results showed that MMP-2 levels and activity were higher in patients with unstable CAD than those with stable CAD and healthy subjects. There was a significant association between MMP-2 levels and cardiovascular disease with MMP-14 levels, which is a pro-MMP-2 activator. In addition, two single nucleotide polymorphisms of the MMP-2 gene (rs243865 and rs243866) were significantly associated with the development of atherosclerosis. In conclusion, MMP-2 plays a crucial role in the development of atherosclerosis among patients with CAD and could be a potential target for CAD therapy.

Causes of platelet loss during extracorporeal life support

BACKGROUND

Most pediatric patients show a decline in platelet counts while on extracorporeal life support (ECLS) and require multiple platelet transfusions. To better understand platelet loss during ECLS, this study estimated platelet loss rates due to diagnostic phlebotomy, platelet activation, bleeding and other causes.

METHODS

We collected data on 91 patients (1d-20y, 50 M, 41F). Platelet losses were estimated based on changes in platelet count, patient+circuit blood volume, and transfused platelet volumes. Platelet extracellular vesicles were measured by flow cytometry.

RESULTS

Median platelet loss was 2.8 × 10⁹ /L/hr, more than twice the normal rate of platelet removal and equivalent to a 67 000/μl decrease in platelet count per day. While platelet loss was correlated with platelet transfusion (r²  = 0.51), transfusion underestimated platelet loss in patients with large decreases in platelet count and over-estimated platelet loss in neonates where the circuit volume > patient blood volume. Patients with disseminated intravascular coagulation before or significant bleeding during ECLS have double the rate of platelet loss. Platelet activation accounted for ~32% of total platelet loss, bleeding ~36% and phlebotomy 4%, with the remaining one-third due to other causes. Annexin-negative platelet extracellular vesicle release, a measure of platelet damage, was increased 9-fold during ECLS.

CONCLUSION

Our study is the first to quantitate total, phlebotomy and activation related platelet loss during ECLS. Platelet activation accounts for ~32% of total platelet loss, while bleeding doubles the platelet loss rate. The etiology of the remaining platelet loss is unknown.

Hemocompatibility challenge of membrane oxygenator for artificial lung technology

The artificial lung (AL) technology is one of the membrane-based artificial organs that partly augments lung functions, i.e. blood oxygenation and CO₂ removal. It is generally employed as an extracorporeal membrane oxygenation (ECMO) device to treat acute and chronic lung-failure patients, and the recent outbreak of the COVID-19 pandemic has re-emphasized the importance of this technology. The principal component in AL is the polymeric membrane oxygenator that facilitates the O₂/CO₂ exchange with the blood. Despite the considerable improvement in anti-thrombogenic biomaterials in other applications (e.g., stents), AL research has not advanced at the same rate. This is partly because AL research requires interdisciplinary knowledge in biomaterials and membrane technology. Some of the promising biomaterials with reasonable hemocompatibility - such as emerging fluoropolymers of extremely low surface energy - must first be fabricated into membranes to exhibit effective gas exchange performance. As AL membranes must also demonstrate high hemocompatibility in tandem, it is essential to test the membranes using in-vitro hemocompatibility experiments before in-vivo test. Hence, it is vital to have a reliable in-vitro experimental protocol that can be reasonably correlated with the in-vivo results. However, current in-vitro AL studies are unsystematic to allow a consistent comparison with in-vivo results. More specifically, current literature on AL biomaterial in-vitro hemocompatibility data are not quantitatively comparable due to the use of unstandardized and unreliable protocols. Such a wide gap has been the main bottleneck in the improvement of AL research, preventing promising biomaterials from reaching clinical trials. This review summarizes the current state-of-the-art and status of AL technology from membrane researcher perspectives. Particularly, most of the reported in-vitro experiments to assess AL membrane hemocompatibility are compiled and critically compared to suggest the most reliable method suitable for AL biomaterial research. Also, a brief review of current approaches to improve AL hemocompatibility is summarized. STATEMENT OF SIGNIFICANCE: The importance of Artificial Lung (AL) technology has been re-emphasized in the time of the COVID-19 pandemic. The utmost bottleneck in the current AL technology is the poor hemocompatibility of the polymer membrane used for O₂/CO₂ gas exchange, limiting its use in the long-term. Unfortunately, most of the in-vitro AL experiments are unsystematic, irreproducible, and unreliable. There are no standardized in-vitro hemocompatibility characterization protocols for quantitative comparison between AL biomaterials. In this review, we tackled this bottleneck by compiling the scattered in-vitro data and suggesting the most suitable experimental protocol to obtain reliable and comparable hemocompatibility results. To the best of our knowledge, this is the first review paper focusing on the hemocompatibility challenge of AL technology.

Anticoagulation Strategies during Extracorporeal Membrane Oxygenation: A Narrative Review

The development of extracorporeal life support technology has added a new dimension to the care of critically ill patients who fail conventional treatment options. Extracorporeal membrane oxygenation (ECMO)—specialized temporary life support for patients with severe cardiac or pulmonary failure—plays a role in bridging the time for organ recovery, transplant, or permanent assistance. The overall patient outcome is dependent on the underlying disease, comorbidities, patient reaction to critical illness, and potential adverse events during ECMO. Moreover, the contact of the blood with the large artificial surface of an extracorporeal system circuit triggers complex inflammatory and coagulation responses. These processes may further lead to endothelial injury and disrupted microcirculation with consequent end-organ dysfunction and the development of adverse events like thromboembolism. Therefore, systemic anticoagulation is considered crucial to alleviate the risk of thrombosis and failure of ECMO circuit components. The gold standard and most used anticoagulant during extracorporeal life support is unfractionated heparin, with all its benefits and disadvantages. However, therapeutic anticoagulation of a critically ill patient carries the risk of clinically relevant bleeding with the potential for permanent injury or death. Similarly, thrombotic events may occur. Therefore, different anticoagulation strategies are employed, while the monitoring and the balance of procoagulant and anticoagulatory factors is of immense importance. This narrative review summarizes the most recent considerations on anticoagulation during ECMO support, with a special focus on anticoagulation monitoring and future directions.

Hemostasis in Pediatric Extracorporeal Life Support: Overview and Challenges

Extracorporeal membrane oxygenation (ECMO) and ventricular assist devices (VADs) are increasingly used in critically ill children. Despite improvements in mechanical design and clinical management, thromboembolic and hemorrhagic events remain significant causes of morbidity and mortality related to the use of both devices. Choice of anticoagulant agents and assays for monitoring continue to present challenges in management. In this review, we describe the incidence and risk factors for thrombosis and hemorrhage, the different types of anticoagulants currently in use, the assays available for monitoring anticoagulation, and management of thromboembolic and bleeding complications in children on mechanical circulatory support (MCS). We conclude by emphasizing the areas that need further study to minimize the risk for thrombosis and hemorrhage in the use of ECMO and VAD in children.

A novel poly (4-methyl-1-pentene)/polypropylene (PMP/PP) thin film composite (TFC) artificial lung membrane for enhanced gas transport and excellent hemo-compatibility

Extracorporeal membrane oxygenation is a technique that provides short-term supports to the heart and lungs. It removes CO₂ from the blood and provides enough oxygen, which is a huge help in the fight against COVID-19. As the key component, the artificial lung membranes have evolved in three generations including silicon, polypropylene and poly (4-methyl-1-pentene). Herein, we for the first time design and fabricate a novel poly (4-methyl-1-pentene)/polypropylene (PMP/PP) thin film composite (TFC) membrane with the anticoagulant coating composed of poly (sodium 4-styrenesulfonate) and cross-linked poly (vinyl alcohol). Poly (sodium 4-styrenesulfonate) provides sulfonic acid groups to inhibit the coagulant factors (FVIII and FXII), and cross-linked poly (vinyl alcohol) increase the stability of the anticoagulant coating and further improve the hydrophilicity via abundant hydroxyl groups to depress the protein adsorption. Long-term anticoagulant property was demonstrated by whole human blood for 28 days. Blood compatibility was evaluated by hemolysis rate, anticoagulation activity (APTT, TT and PT), complement activation, platelet activation and contact activation. Pure CO₂, O₂ and N₂ permeation rates were determined to evaluate the mass transfer properties of PMP/PP TFC membranes. Gas permeation results revealed that gas permeation flux increased in the TFC membranes because of the decrease of crystallinity. Overall, the so prepared PMP/PP membrane shows good CO₂/O₂ selectivity and blood compatibility as novel TFC artificial lung membrane.

Human erythrocyte fragmentation during ex-vivo pig organ perfusion

Platelet sequestration is a common process during organ reperfusion after transplantation. However, instead of lower platelet counts, when using traditional hemocytometers and light microscopy, we observed physiologically implausible platelet counts in the course of ex-vivo lung and liver xenograft organ perfusion studies. We employed conventional flow cytometry (FC) and imaging FC (AMINS ImageStream X) to investigate the findings and found platelet-sized fragments in the circulation that are mainly derived from red blood cell membranes. We speculate that this erythrocyte fragmentation contributes to anemia during in-vivo organ xenotransplant.

Effect of Platelet Transfusions on Extracorporeal Life Support Oxygenator's Function

OBJECTIVE

Bleeding is a common complication of extracorporeal membrane oxygenation (ECMO), leading to increased mortality. Since one of its main complications is bleeding, platelet transfusions are frequently prescribed for children on ECMO. However, there is currently very little information on the effect of platelet transfusions on the function of the ECMO oxygenator. Our objective was to describe the effect of platelet transfusions on oxygenator function.

METHODS

In this retrospective study, we included all children (<18 years) who received ECMO support in our pediatric intensive care unit (PICU) between January 2017 and December 2019. Oxygenator function, measured before and after platelet transfusion, was assessed by post-oxygenator P _ECMO O₂ and the gradient in pre- post-oxygenator pressures (Delta Pressure).

RESULTS

Over 3 years, we analyzed 235 platelet transfusions from 55 children who received ECMO support. Thirty-two (80%) of children were on veno-arterial ECMO and majority of them were peripherally cannulated. When looking at all transfusions, the post-transfusion change in delta-pressure was 0.1 mmHg (p = 0.69) and post-membrane P _ECMO O₂ was 6 mmHg (p = 0.49). However, in the subgroup with the lowest quartile of pre-transfusion oxygenator function, the post-transfusion change in delta-pressure was -5.2 ± 2.7 mmHg (p < 0.001) and the post-transfusion change in P _ECMO O₂ was -118 ± 49 (p < 0.001). The area under the ROC curve for the pre-transfusion delta-pressure and P _ECMO O₂ to predict a worsening of the oxygenator function were 0.72 (95%CI 0.63-0.81) and 0.71 (95%CI 0.64-0.78), respectively. Using regression models, pre-transfusion delta-pressure and P _ECMO O₂ were the only independent factors associated with oxygenator function worsening (p < 0.001).

CONCLUSION

Our study suggests that overall, platelet transfusions do not seem to impact the ECMO oxygenator's function. However, in the subgroup of patients with the lowest pre-transfusion oxygenator function, platelet transfusions were independently associated with a worsening function. Future studies should investigate if this warrants adjustments of the anticoagulation strategy around the platelet transfusion, especially among patients with lower oxygenator function.

Hemostasis in neonatal ECMO

Extracorporeal membrane oxygenation (ECMO) is a life-saving support for cardio-respiratory function. Over the last 50 years, the extracorporeal field has faced huge technological progress. However, despite the improvements in technique and materials, coagulation problems are still the main contributor to morbidity and mortality of ECMO patients. Indeed, the incidence and survival rates of the main hemorrhagic and thrombotic complications in neonatal respiratory ECMO are relevant. The main culprit is related to the intrinsic nature of ECMO: the contact phase activation. The exposure of the human blood to the non-endothelial surface triggers a systemic inflammatory response syndrome, which chronically activates the thrombin generation and ultimately leads to coagulative derangements. Pre-existing illness-related hemostatic dysfunction and the peculiarity of the neonatal clotting balance further complicate the picture. Systemic anticoagulation is the management's mainstay, aiming to prevent thrombosis within the circuit and bleeding complications in the patient. Although other agents (i.e., direct thrombin inhibitors) have been recently introduced, unfractionated heparin (UFH) is the standard of care worldwide. Currently, there are multiple tests exploring ECMO-induced coagulopathy. A combination of the parameters mentioned above and the evaluation of the patient's underlying clinical context should be used to provide a goal-directed antithrombotic strategy. However, the ideal algorithm for monitoring anticoagulation is currently unknown, resulting in a large inter-institutional diagnostic variability. In this review, we face the features of the available monitoring tests and approaches, mainly focusing on the role of point-of-care (POC) viscoelastic assays in neonatal ECMO. Current gaps in knowledge and areas that warrant further study will also be addressed.

Plasma and Platelet Transfusions Strategies in Neonates and Children Undergoing Cardiac Surgery With Cardiopulmonary Bypass or Neonates and Children Supported by Extracorporeal Membrane Oxygenation: From the Transfusion and Anemia EXpertise Initiative-Control/Avoidance of Bleeding

OBJECTIVES

To present the recommendations and consensus statements with supporting literature for plasma and platelet transfusions in critically ill neonates and children undergoing cardiac surgery with cardiopulmonary bypass or supported by extracorporeal membrane oxygenation from the Transfusion and Anemia EXpertise Initiative-Control/Avoidance of Bleeding.

DESIGN

Systematic review and consensus conference of international, multidisciplinary experts in platelet and plasma transfusion management of critically ill children.

SETTING

Not applicable.

PATIENTS

Critically ill neonates and children following cardiopulmonary bypass or supported by extracorporeal membrane oxygenation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A panel of nine experts developed evidence-based and, when evidence was insufficient, expert-based statements for plasma and platelet transfusions in critically ill neonates and children following cardiopulmonary bypass or supported by extracorporeal membrane oxygenation. These statements were reviewed and ratified by the 29 Transfusion and Anemia EXpertise Initiative-Control/Avoidance of Bleeding experts. A systematic review was conducted using MEDLINE, EMBASE, and Cochrane Library databases, from inception to December 2020. Consensus was obtained using the Research and Development/University of California, Los Angeles Appropriateness Method. Results were summarized using the Grading of Recommendations Assessment, Development, and Evaluation method. We developed one good practice statement, two recommendations, and three expert consensus statements.

CONCLUSIONS

Whereas viscoelastic testing and transfusion algorithms may be considered, in general, evidence informing indications for plasma and platelet transfusions in neonatal and pediatric patients undergoing cardiac surgery with cardiopulmonary bypass or those requiring extracorporeal membrane oxygenation support is lacking.

The Relative Early Decrease in Platelet Count Is Associated With Mortality in Post-cardiotomy Patients Undergoing Venoarterial Extracorporeal Membrane Oxygenation

Background: The relationship between the magnitude of platelet count decrease and mortality in post-cardiotomy cardiogenic shock (PCS) patients undergoing venoarterial extracorporeal membrane oxygenation (VA-ECMO) has not been well-reported. This study was designed to evaluate the association between the relative decrease in platelet count (RelΔplatelet) at day 1 from VA-ECMO initiation and in-hospital mortality in PCS patients.

Methods: Patients (n = 178) who received VA-ECMO for refractory PCS between January 2016 and December 2018 at the Beijing Anzhen Hospital were reviewed retrospectively. Multivariable logistic regression analyses were performed to assess the association between RelΔplatelet and in-hospital mortality.

Results: One hundred and sixteen patients (65%) were weaned from VA-ECMO, and 84 patients (47%) survived to hospital discharge. The median [interquartile range (IQR)] time on VA-ECMO support was 5 (3–6) days. The median (IQR) RelΔ platelet was 41% (26–59%). Patients with a RelΔ platelet ≥ 50% had an increased mortality compared to those with a RelΔ platelet < 50% (57 vs. 37%; p < 0.001). A large RelΔplatelet (≥50%) was independently associated with in-hospital mortality after controlling for potential confounders (OR 8.93; 95% CI 4.22–18.89; p < 0.001). The area under the receiver operating characteristic curve for RelΔ platelet was 0.78 (95% CI, 0.71–0.85), which was better than that of platelet count at day 1 (0.69; 95% CI, 0.61–0.77).

Conclusions: In patients receiving VA-ECMO for post-cardiotomy cardiogenic shock, a large relative decrease in platelet count in the first day after ECMO initiation is independently associated with an increased in-hospital mortality.

The Association of Platelet Decrease Following Continuous Renal Replacement Therapy Initiation and Increased Rates of Secondary Infections

OBJECTIVES

Thrombocytopenia is common in critically ill patients treated with continuous renal replacement therapy and decreases in platelets following continuous renal replacement therapy initiation have been associated with increased mortality. Platelets play a role in innate and adaptive immunity, making it plausible that decreases in platelets following continuous renal replacement therapy initiation predispose patients to development of infection. Our objective was to determine if greater decreases in platelets following continuous renal replacement therapy correlate with increased rates of secondary infection.

DESIGN

Retrospectivecohort analysis.

SETTING

This study uses a continuous renal replacement therapy database from Mayo Clinic (Rochester, MN), a tertiary academic center.

PARTICIPANTS

Adult patients who survived until ICU discharge and were on continuous renal replacement therapy for less than 30 days were included. A subgroup analysis was also performed in patients with thrombocytopenia (platelets < 100 × 103/µL) at continuous renal replacement therapy initiation.

MEASUREMENTS AND MAIN RESULTS

The primary predictor variable was a decrease in platelets from precontinuous renal replacement therapy levels of greater than 40% or less than or equal to 40%, although multiple cut points were analyzed. The primary outcome was infection after ICU discharge, and secondary endpoints included post-ICU septic shock and post-ICU mortality. Univariable, multivariable, and propensity-adjusted analyses were used to determine associations between the predictor variable and the outcomes.

RESULTS

Among 797 eligible patients, 253 had thrombocytopenia at continuous renal replacement therapy initiation. A greater than 40% decrease in platelets after continuous renal replacement therapy initiation was associated in the multivariable-adjusted models with increased odds of post-ICU infection in the full cohort (odds ratio, 1.49; CI, 1.02-2.16) and in the thrombocytopenia cohort (odds ratio, 2.63; CI, 1.35-5.15) cohorts.

CONCLUSIONS

Platelet count drop by greater than 40% following continuous renal replacement therapy initiation is associated with an increased risk of secondary infection, particularly in patients with thrombocytopenia at the time of continuous renal replacement therapy initiation. Further research is needed to evaluate the impact of both continuous renal replacement therapy and platelet loss on subsequent infection risk.

Analysis of the 2020 EACTS/ELSO/STS/AATS Expert Guidelines on the Management of Adult Postcardiotomy Extracorporeal Life Support

Extracorporeal life support (ECLS), also known as extracorporeal membrane oxygenation (ECMO), increasingly is used in postcardiotomy (PC) shock to facilitate a bridge to sustained recovery, long-term mechanical support, or heart transplantation. Given increasing prevalence and complexity of PC-ECLS, a joint expert consensus guideline was created in 2020 for management of adult PC-ECLS by the European Association for Cardio-Thoracic Surgery (EACTS), the Extracorporeal Life Support Organization (ELSO), the Society of Thoracic Surgeons (STS), and the American Association of Thoracic Surgery (AATS). The aim of this analysis was to comprehensively review the expert consensus guidelines, with particular emphasis on PC-ECLS candidacy, timing, cannula configuration, left ventricular distention, anticoagulation, ECLS weaning, and intensive care unit complications. This analysis finds the expert consensus guideline to be timely, pertinent, and clinically valuable, although there remains the need for larger clinical trials to codify best practices.

Neonatal respiratory and cardiac ECMO in Europe

Neonatal extracorporeal membrane oxygenation (ECMO) is a life-saving procedure for critically ill neonates suffering from a potentially reversible disease, causing severe cardiac and/or respiratory failure and refractory to maximal conventional management. Since the 1970s, technology, management, and clinical applications of neonatal ECMO have changed. Pulmonary diseases still represent the principal neonatal diagnosis, with an overall 74% survival rate, and up to one-third of cases are due to congenital diaphragmatic hernia. The overall survival rate in cardiac ECMO is lower, with congenital heart defect representing the main indication. This review provides an overview of the available evidence in the field of neonatal ECMO. We will address the changing epidemiology, basic principles, technologic advances in circuitry, and monitoring, and deliver a current multidisciplinary management framework, focusing on ECMO applications, complications, and long-term morbidities. Lastly, areas for further research will be highlighted.Conclusions: ECMO is a life support with a potential impact on long-term patients' outcomes. In the next years, advances in knowledge, technology, and expertise may push neonatal ECMO boundaries towards more premature and increasingly complex infants, with the final aim to reduce the burden of ECMO-related complications and improve overall patients' outcomes. What is Known: • ECMO is a life-saving option in newborns with refractory respiratory and/or cardiac failure. • The multidisciplinary ECMO management is challenging and may expose neonates to complications with an impact on long-term outcomes. What is New: • Advances in technology and biomaterials will improve neonatal ECMO management and, eventually, the long-term outcome of these complex patients. • Experimental models of artificial placenta and womb technology are under investigation and may provide clinical translation and future research opportunities.

Hemostasis, coagulation and thrombin in venoarterial and venovenous extracorporeal membrane oxygenation: the HECTIC study

Extracorporeal membrane oxygenation (ECMO) support has a high incidence of both bleeding and thrombotic complications. Despite clear differences in patient characteristics and pathologies between veno-venous (VV) and veno-arterial (VA) ECMO support, anticoagulation practices are often the same across modalities. Moreover, there is very little data on their respective coagulation profiles and comparisons of thrombin generation in these patients. This study compares the coagulation profile and thrombin generation between patients supported with either VV and VA ECMO. A prospective cohort study of patients undergoing VA and VV ECMO at an Intensive care department of a university hospital and ECMO referral centre. In addition to routine coagulation testing and heparin monitoring per unit protocol, thromboelastography (TEG), multiplate aggregometry (MEA), calibrated automated thrombinography (CAT) and von-Willebrand’s activity (antigen and activity ratio) were sampled second-daily for 1 week, then weekly thereafter. VA patients had significantly lower platelets counts, fibrinogen, anti-thrombin and clot strength with higher d-dimer levels than VV patients, consistent with a more pronounced consumptive coagulopathy. Thrombin generation was higher in VA than VV patients, and the heparin dose required to suppress thrombin generation was lower in VA patients. There were no significant differences in total bleeding or thrombotic event rates between VV and VA patients when adjusted for days on extracorporeal support. VA patients received a lower median daily heparin dose 8500 IU [IQR 2500–24000] versus VV 28,800 IU [IQR 17,300–40,800.00]; < 0.001. Twenty-eight patients (72%) survived to hospital discharge; comprising 53% of VA patients and 77% of VV patients. Significant differences between the coagulation profiles of VA and VV patients exist, and anticoagulation strategies for patients of these modalities should be different. Further research into the development of tailored anticoagulation strategies that include the mode of ECMO support need to be completed.

Myocardial Injury Promotes Matrix Metalloproteinase-9 Activity in the Renal Cortex in Preclinical Models of Acute Myocardial Infarction

New mechanistic insight into how the kidney responds to cardiac injury during acute myocardial infarction (AMI) is required. We hypothesized that AMI promotes inflammation and matrix metalloproteinase-9 (MMP9) activity in the kidney and studied the effect of initiating an Impella CP or veno-arterial extracorporeal membrane oxygenation (VA-ECMO) before coronary reperfusion during AMI. Adult male swine were subjected to coronary occlusion and either reperfusion (ischemia-reperfusion; IR) or support with either Impella or VA-ECMO before reperfusion. IR and ECMO increased while Impella reduced levels of MMP-9 in the myocardial infarct zone, circulation, and renal cortex. Compared to IR, Impella reduced myocardial infarct size and urinary KIM-1 levels, but VA-ECMO did not. IR and VA-ECMO increased pro-fibrogenic signaling via transforming growth factor-beta and endoglin in the renal cortex, but Impella did not. These findings identify that AMI increases inflammatory activity in the kidney, which may be attenuated by Impella support.

The Roles of Membrane Technology in Artificial Organs: Current Challenges and Perspectives

The recent outbreak of the COVID-19 pandemic in 2020 reasserted the necessity of artificial lung membrane technology to treat patients with acute lung failure. In addition, the aging world population inevitably leads to higher demand for better artificial organ (AO) devices. Membrane technology is the central component in many of the AO devices including lung, kidney, liver and pancreas. Although AO technology has improved significantly in the past few decades, the quality of life of organ failure patients is still poor and the technology must be improved further. Most of the current AO literature focuses on the treatment and the clinical use of AO, while the research on the membrane development aspect of AO is relatively scarce. One of the speculated reasons is the wide interdisciplinary spectrum of AO technology, ranging from biotechnology to polymer chemistry and process engineering. In this review, in order to facilitate the membrane aspects of the AO research, the roles of membrane technology in the AO devices, along with the current challenges, are summarized. This review shows that there is a clear need for better membranes in terms of biocompatibility, permselectivity, module design, and process configuration.

Different mechanisms of oxygenator failure and high plasma von Willebrand factor antigen influence success and survival of venovenous extracorporeal membrane oxygenation

OBJECTIVE

Failure of membrane oxygenator (MO) function of venovenous extracorporeal membrane oxygenators (VV ECMO) remains problematic. The development of device-induced coagulation disorder (COD) or worsened gas transfer (WGT) necessitates a system exchange. The aim was to correlate von Willebrand factor antigen (vWF:Ag) with the predisposition to MO failure and mortality.

METHODS

Laboratory parameters (inflammation, coagulation) and ECMO-related data from 31 VV ECMO patients were analyzed before and after the first MO exchange. Study groups were identified according to the exchange reasons (COD, WGT) and the extent of vWF:Ag (low, ≤425%; high, >425%).

RESULTS

vWF:Ag remained unchanged after system exchange. High vWF:Ag was associated with systemic endothelial activation of older and obese patients with elevated SOFA score, increased norepinephrine and higher requirement of continuous renal replacement therapy without an effect on MO runtime and mortality. Including the mechanism of MO failure (COD, WGT), various patient group emerged. COD/low vWF:Ag summarized younger and less critically ill patients that benefit mainly from ECMO by a significant improvement of their inflammatory and coagulation status (CRP, D-dimers, fibrinogen) and highest survival rate (91%). Instead, WGT/high vWF:Ag presented older and more obese patients with a two-digit SOFA score, highest norepinephrine, and aggravated gas transfer. They benefited temporarily from system exchange but with worst survival (33%).

CONCLUSIONS

vWF:Ag levels alone cannot predict early MO failure and outcome in VV ECMO patients. Probably, the mechanism of clotting disorder in combination with the vWF:Ag level seems to be essential for clot formation within the MO. In addition, vWF:Ag levels allows the identification different patient populations In particular, WGT/high vWF:Ag represented a critically ill population with higher ECMO-associated mortality.

Device-Induced Hemostatic Disorders in Mechanically Assisted Circulation

Mechanically assisted circulation (MAC) sustains the blood circulation in the body of a patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) or on ventricular assistance with a ventricular assist device (VAD) or on extracorporeal membrane oxygenation (ECMO) with a pump-oxygenator system. While MAC provides short-term (days to weeks) support and long-term (months to years) for the heart and/or lungs, the blood is inevitably exposed to non-physiological shear stress (NPSS) due to mechanical pumping action and in contact with artificial surfaces. NPSS is well known to cause blood damage and functional alterations of blood cells. In this review, we discussed shear-induced platelet adhesion, platelet aggregation, platelet receptor shedding, and platelet apoptosis, shear-induced acquired von Willebrand syndrome (AVWS), shear-induced hemolysis and microparticle formation during MAC. These alterations are associated with perioperative bleeding and thrombotic events, morbidity and mortality, and quality of life in MCS patients. Understanding the mechanism of shear-induce hemostatic disorders will help us develop low-shear-stress devices and select more effective treatments for better clinical outcomes.

Transfusion management for children supported by extracorporeal membrane oxygenation

Due to the patients' underlying illness, in combination with circuit-induced coagulopathy, as well as PLT dysfunction, children supported by ECMO are a risk of receiving large volumes of blood components. Given the increasing use of modified blood products and newer biologics, it is unknown whether these products have equal efficacy and safety, in ECMO. The majority of guidance for transfusion therapy is based on expert opinion alone, and research on indications for RBC, plasma, and PLT transfusions for children on ECMO should be a priority.

Epidemiology of the Use of Hemostatic Agents in Children Supported by Extracorporeal Membrane Oxygenation: A Pediatric Health Information System Database Study

Objectives: Children supported by extracorporeal membrane oxygenation (ECMO) are at high risk of bleeding. Though practitioners often prescribe blood components and/or medications to prevent or treat bleeding, the utilization of these hemostatic measures in children is not well-understood. We sought to evaluate the use of hemostatic blood products (platelet, plasma and cryoprecipitate transfusions) and medications [aminocaproic acid, tranexamic acid (TXA) and Factor VIIa] in children supported by ECMO. Design: Retrospective observational study using the Pediatric Health Information System (PHIS) database from 2011-2017. Setting: Fifty-one U.S. children's hospitals. Patients: Children (aged 0-18 years) supported by ECMO. Interventions: None. Measurements and Main Results: ECMO was employed in the care of 7,910 children for a total of 56,079 ECMO days. Fifty-five percent of the patients were male with a median (IQR) age of 0 (0-2) years. The median (IQR) length of ECMO was 5 (2-9) days with a hospital mortality rate of 34%. Platelets were transfused on 49% of ECMO days, plasma on 33% of ECMO days and cryoprecipitate on 17% of ECMO days. Twenty-two percent of children received TXA with the majority receiving it on the first day of ECMO and the use of TXA increased during the 6-year period studied (p < 0.001). Seven percent of children received aminocaproic acid and 3% received Factor VIIa. Conclusions: Children supported by ECMO are exposed to a significant number of hemostatic blood products. Antifibrinolytics, in particular TXA, are being used more frequently. Given the known morbidity and mortality associated with hemostatic blood products, studies are warranted to evaluate the effectiveness of hemostatic strategies.

Intracranial hemorrhage on extracorporeal membrane oxygenation: an international survey

INTRODUCTION

Intracranial hemorrhage is one of the most dreaded complications associated with extracorporeal membrane oxygenation. However, robust data to guide clinical practice are lacking. We aimed to describe the current perceptions and practices surrounding the risk, prevention, diagnosis, management, and prognosis of intracranial hemorrhage in patients on extracorporeal membrane oxygenation.

METHODS

We conducted an international, cross-sectional survey of adult extracorporeal membrane oxygenation centers using a self-administered electronic questionnaire sent to medical directors and program coordinators of all 290 adult centers member of the Extracorporeal Life Support Organization.

RESULTS

There were 143 respondents (49%). The median proportion of patients having neuroimaging performed was only 1-25% in venovenous-extracorporeal membrane oxygenation patients and 26-50% in venoarterial-extracorporeal membrane oxygenation and extracorporeal cardiopulmonary resuscitation. The majority of participants (58%) tolerated a PaO₂ < 60 mm Hg on venovenous-extracorporeal membrane oxygenation. Lower PaO₂ targets were inversely correlated with the reported incidence of intracranial hemorrhage (r =-0.247; p = 0.024). In patients with intracranial hemorrhage, most participants reported stopping anticoagulation, and median targets for blood product administration were 70,000-99,000 platelets/µL, 1.5-1.9 of international normalized ratio, and 1.6-2.0 g/L of fibrinogen.

CONCLUSION

We found significant heterogeneity in the perceptions and practices. This underlines the need for more research to appropriately guide patient management. Importantly, neuroimaging was performed only in a minority of patients. Considering the important management implications reported by most centers when intracranial hemorrhage is diagnosed, perhaps clinicians should consider widening their indications for early neuroimaging.

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.

Mitral valve bio-prosthesis and annuloplasty thrombosis during extracorporeal membrane oxygenation: case series

Background

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is a well-recognized form of haemodynamic support for patients with refractory cardiogenic shock, who are unable to be weaned off cardiopulmonary bypass. Thrombosis or bleeding from cannula sites or surgical wounds are the leading cause of morbidity and mortality in these patients, and presents a delicate balance of anticoagulation during management of patients undergoing circulatory support.

Case summary

In this case series, we discuss three cases of patients undergoing mitral valve replacements or repair with thrombosis of their new bio-prosthesis in the immediate post-operative setting. All three patients were supported with VA-ECMO post-operatively, and thrombosis occurred despite anticoagulation.

Discussion

During extracorporeal membrane oxygenation, the reduced flow throughout the heart increases the risk of intra-cardiac thrombosis. This is of particular importance in the context of mitral valve replacements and repairs, where the bio-prosthesis is an additional risk factor for thrombosis. Our cases demonstrate the morbidity and mortality of such complications, with the likely aetiology being low transvalvular flow in a newly inserted valve combined with the pro-thrombotic state created by the VA-ECMO circuit.

Pediatric Plasma and Platelet Transfusions on Extracorporeal Membrane Oxygenation: A Subgroup Analysis of Two Large International Point-Prevalence Studies and the Role of Local Guidelines

OBJECTIVES

To describe the indications and thresholds for plasma and platelet transfusions for pediatric extracorporeal membrane oxygenation, to compare responses to these transfusions and to describe institutional protocols directing their administration.

DESIGN

Subgroup analysis of two prospective, observational studies paired with survey of sites who enrolled subjects into this cohort.

SETTING

Fifty-one PICUs in 13 countries.

PATIENTS

Children (3 d to 16 yr old) were enrolled if they received a plasma or platelet transfusion while on extracorporeal membrane oxygenation during one of the predefined screening weeks.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Forty-eight children on extracorporeal membrane oxygenation received plasma transfusions and 90 received platelet transfusions. Sixty percent of plasma transfusions (29/48) and 79% of the platelet transfusions (71/90) were given for prophylaxis of bleeding. The median (interquartile range) international normalized ratio prior to transfusion, known in 75% of the patients (36/48), was 1.45 (1.20-1.85). The median (interquartile range) total platelet count prior to transfusion, known in all of the patients, was 70 × 10/L (52-90 × 10/L). The international normalized ratio and total platelet count values prior to transfusion did not vary based on bleeding versus nonbleeding indications. The median (interquartile range) reduction in international normalized ratio for mild coagulopathies (international normalized ratio ≤ 2.0) was 0.1 (0.4-0), median (interquartile range) increase in fibrinogen was 0.2 g/L (0.1-0.4 g/L) and median increase in total platelet count was 34 × 10/L (10-74 × 10/L). Through the course of their admission, children supported by extracorporeal membrane oxygenation received a total median (interquartile range) dose of 75 mL/kg (36-159 mL/kg) of plasma transfusions and 92 mL/kg (42-239 mL/kg) of platelet transfusions. Institutional protocols varied but provided guidance for platelet transfusions more commonly.

CONCLUSIONS

Children supported by extracorporeal membrane oxygenation receive large volumes of plasma and platelet transfusions with some institutional guidance in the form of protocols, but significant variation in practice. Interventional studies are necessary to provide evidence to direct the transfusion of hemostatic products in children supported by extracorporeal membrane oxygenation.

Pressure and flow properties of cannulae for extracorporeal membrane oxygenation I: return (arterial) cannulae

Adequate extracorporeal membrane oxygenation support in the adult requires cannulae permitting blood flows up to 6-8 L/minute. In accordance with Poiseuille's law, flow is proportional to the fourth power of cannula inner diameter and inversely proportional to its length. Poiseuille's law can be applied to obtain the pressure drop of an incompressible, Newtonian fluid (such as water) flowing in a cylindrical tube. However, as blood is a pseudoplastic non-Newtonian fluid, the validity of Poiseuille's law is questionable for prediction of cannula properties in clinical practice. Pressure-flow charts with non-Newtonian fluids, such as blood, are typically not provided by the manufacturers. A standardized laboratory test of return (arterial) cannulae for extracorporeal membrane oxygenation was performed. The aim was to determine pressure-flow data with human whole blood in addition to manufacturers' water tests to facilitate an appropriate choice of cannula for the desired flow range. In total, 14 cannulae from three manufacturers were tested. Data concerning design, characteristics, and performance were graphically presented for each tested cannula. Measured blood flows were in most cases 3-21% lower than those provided by manufacturers. This was most pronounced in the narrow cannulae (15-17 Fr) where the reduction ranged from 27% to 40% at low flows and 5-15% in the upper flow range. These differences were less apparent with increasing cannula diameter. There was a marked disparity between manufacturers. Based on the measured results, testing of cannulae including whole blood flows in a standardized bench test would be recommended.

Platelet Transfusion Practice and Related Outcomes in Pediatric Extracorporeal Membrane Oxygenation

OBJECTIVE

To describe factors associated with platelet transfusion during pediatric extracorporeal membrane oxygenation and the relationships among platelet transfusion, complications, and mortality.

DESIGN

Secondary analysis of data collected prospectively by the Collaborative Pediatric Critical Care Research Network between December 2012 and September 2014.

SETTING

Eight Collaborative Pediatric Critical Care Research Network-affiliated hospitals.

PATIENTS

Age less than 19 years old and treated with extracorporeal membrane oxygenation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 511 children, 496 (97.1%) received at least one platelet transfusion during extracorporeal membrane oxygenation. Neonatal age, venoarterial extracorporeal membrane oxygenation, and various acute and chronic diagnoses were associated with increased average daily platelet transfusion volume (milliliters per kilogram body weight). On multivariable analysis, average daily platelet transfusion volume was independently associated with mortality (per 1 mL/kg; odds ratio, 1.05; CI, 1.03-1.08; p < 0.001), whereas average daily platelet count was not (per 1 × 10/L up to 115 × 10/L; odds ratio, 1.00; CI, 0.98-1.01; p = 0.49). Variables independently associated with increased daily bleeding risk included increased platelet transfusion volume on the previous extracorporeal membrane oxygenation day, a primary cardiac indication for extracorporeal membrane oxygenation, adolescent age, and an acute diagnosis of congenital cardiovascular disease. Variables independently associated with increased daily thrombotic risk included increased platelet transfusion volume on the previous extracorporeal membrane oxygenation day and venoarterial extracorporeal membrane oxygenation. Variables independently associated with decreased daily thrombotic risk included full-term neonatal age and an acute diagnosis of airway abnormality.

CONCLUSIONS

Platelet transfusion was common in this multisite pediatric extracorporeal membrane oxygenation cohort. Platelet transfusion volume was associated with increased risk of mortality, bleeding, and thrombosis.

ECMO for Neonatal Sepsis in 2019

Sepsis and septic shock in newborns causes mortality and morbidity depending on the organism and primary site. ECMO provides cardiorespiratory support to allow adequate organ perfusion during the time for antibiotics and source control surgery (if needed) to occur. ECMO mode and cannulation site vary depending on support required and local preference. Earlier and more aggressive use of ECMO can improve survival.

Emergency Abdominal Surgery Outcomes of Critically Ill Patients on Extracorporeal Membrane Oxygenation: A Case-Matched Study with a Propensity Score Analysis

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) induces coagulation disorders increasing the risk of bleeding during invasive procedures. We aimed to describe the outcomes of critically ill ECMO patients undergoing emergency abdominal surgery compared to non-ECMO patients.

STUDY DESIGN

This is a retrospective case-matched single-center study with propensity score analysis in a tertiary ICU. All patients who underwent abdominal surgery were included.

RESULTS

From 2006 to 2014, 77 patients admitted in our ICU underwent emergency abdominal surgery, 35 were on ECMO. Surgery indications were comparable for ECMO and non-ECMO patients: mostly intestinal ischemia (42%) and cholecystectomy (25%). Postoperative bleeding was significantly more frequent in ECMO group versus non-ECMO: 77% versus 40% transfused, with medians of 13 (6-22) versus 3 (0-5) packed red blood cell; 9 (3-17) versus 0 (0-4) fresh frozen plasma and 12 (3-22) versus 0 (0-8) platelet units (p < 0.001 for all items). Reintervention for hemorrhage was required in 20% versus 2%, respectively, p = 0.02. At multivariable analysis, ECMO was strongly associated with bleeding (OR, 5.6 [95% CI, 2.0-15.4]; p = 0.001). ICU mortality was higher for ECMO-treated patients (69% vs. 33%; p = 0.003), but perioperative mortality remained comparable between groups (11% vs. 12%, NS). Propensity score-matched analysis confirmed more frequent and severe bleeding in ECMO patients.

CONCLUSIONS

Abdominal surgery procedures on ECMO-treated patients are associated with a higher risk of hemorrhage compared to non-ECMO ICU patients. Further studies are needed to optimize ECMO patient management during such interventions.

Platelet Phenotype and Function in the Setting of Pediatric Extracorporeal Membrane Oxygenation (ECMO): A Systematic Review

Background: Despite increasing technical improvement and extracorporeal membrane oxygenation (ECMO)-related knowledge over the past three decades, morbidity and mortality associated with bleeding and clotting complications remain high in pediatric patients undergoing ECMO. Platelets, a key element of the coagulation system, have been proposed to be the main cause of coagulopathy in the setting of ECMO. This systematic review aims to summarize and discuss the existing knowledge of platelet phenotype and function in the pediatric ECMO population. Methods: A systematic review was conducted for the Embase, Medline, and PubMed databases following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Results: The detailed study selection process yielded a total of 765 studies and only 3 studies that fulfilled the selection criteria were included in this review. Techniques used to assess platelet function in the three existing studies included platelet aggregometry, flow cytometry, and thromboelastography-platelet mapping. The finding that is common to the three studies is reduced platelet function in pediatric patients during ECMO either compared to before the initiation of ECMO or in non-survivors compared to survivors. Two studies demonstrated reduced platelet aggregation that are irreversible by platelet transfusion during ECMO. Two studies reported bleeding events and mortality in children on ECMO and none of the studies investigated thrombotic events. Conclusions: This systematic review demonstrates the extremely limited information available for platelet phenotype and function in the pediatric ECMO population. Evidence from the existing literature suggests reduced platelet aggregation and increased platelet activation in children during ECMO. However, this needs to be interpreted with care due to the limitations associated with the techniques used for platelet function testing. Furthermore, the association between platelet dysfunction and clinical outcomes in the pediatric ECMO population remains elusive. Multiple research gaps have been identified when it comes to the knowledge of platelet phenotype and function of children on ECMO, highlighting the need for robust, well-designed studies in this setting.

Coagulation Factor Levels and Underlying Thrombin Generation Patterns in Adult Extracorporeal Membrane Oxygenation Patients

BACKGROUND

There is a paucity of data on the underlying procoagulant-anticoagulant balance during extracorporeal membrane oxygenation (ECMO). We hypothesized that adult ECMO patients would have an imbalance between procoagulant and anticoagulant factors, leading to an abnormal underlying thrombin generation (TG) pattern.

METHODS

Twenty adult venoarterial (VA) ECMO patients had procoagulant and anticoagulant factor levels measured temporally on ECMO day 1 or 2, day 3, and day 5. In heparin-neutralized plasma, underlying TG patterns, and sensitivity to activated protein C were assessed using calibrated automated thrombogram. TG parameters including lag time, peak TG, and endogenous thrombin potential (ETP) were compared against 5 normal plasma controls (3 males and 2 females) obtained from a commercial supplier. Thrombomodulin (TM) was added to some samples to evaluate for activated protein C resistance.

RESULTS

Procoagulant factors (factor [F] II, FV, and FX) were mostly in normal reference ranges and gradually increased during the first 5 ECMO days (P = .022, <.001, <.001). FVIII levels were elevated at all time points and did not change (P = .766). In contrast, FXI was in the low-normal range but did not increase during ECMO (P = .093). Antithrombin (AT) and protein C levels were below normal but increased during the first 5 ECMO days (P = .002 and P = .014). Heparinase-treated samples showed prolonged lag time, increased peak TG, and increased ETP compared to controls; mean difference in lag time on ECMO day 1 or 2 = 6.0 minutes (99% confidence interval [CI], 2.8-9.2), peak TG = 193.4 (99% CI, 122.5-264.3), and ETP = 1170.4 (99% CI, 723.2-1617.6). After in vitro TM treatment, differences in TG parameters were accentuated and ECMO samples appeared insensitive to TM treatment; mean difference in lag time on ECMO day 1 or 2 = 9.3 minutes (99% CI, 6.2-12.4), peak TG = 233.0 (99% CI, 140.9-325.1), and ETP = 1322.5 (99% CI, 764.8-1880.2). Similar differences in TG parameters were observed on ECMO days 3 and 5.

CONCLUSIONS

Contact activation occurs during ECMO, but procoagulant factor levels are generally preserved. Although heparin-neutralized TG is delayed, peak TG and ETP are supranormal in the setting of high FVIII and low AT and protein C levels. Resistance to TM is also apparent. These changes demonstrate a possible mechanism for hypercoagulability during adult VA ECMO.

Low flow rate alters haemostatic parameters in an ex-vivo extracorporeal membrane oxygenation circuit

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is a life-saving modality used to manage cardiopulmonary failure refractory to conventional medical and surgical therapies. Despite advances in ECMO equipment, bleeding and thrombosis remain significant complications. While the flow rate for ECMO support is well recognized, less is known about the minimum-rate requirements and haemostasis. We investigated the relationship between different ECMO flow rates, and their effect on haemolysis and coagulation.

METHODS

Ten ex-vivo ECMO circuits were tested using donated, < 24-h-old human whole blood, with two flow rates: high-flow at 4 L/min (normal adult cardiac output; n = 5) and low-flow at 1.5 L/min (weaning; n = 5). Serial blood samples were taken for analysis of haemolysis, von Willebrand factor (vWF) multimers by immunoblotting, rotational thromboelastometry, platelet aggregometry, flow cytometry and routine coagulation laboratory tests.

RESULTS

Low-flow rates increased haemolysis after 2 h (p = 0.02), 4 h (p = 0.02) and 6 h (p = 0.02) and the loss of high-molecular-weight vWF multimers (p = 0.01), while reducing ristocetin-induced platelet aggregation (p = 0.0002). Additionally, clot formation times were prolonged (p = 0.006), with a corresponding decrease in maximum clot firmness (p = 0.006).

CONCLUSIONS

In an ex-vivo model of ECMO, low-flow rate (1.5 L/min) altered haemostatic parameters compared to high-flow (4 L/min). Observed differences in haemolysis, ristocetin-induced platelet aggregation, high-molecular-weight vWF multimers and clot formation time suggest an increased risk of bleeding complications. Since patients are often on ECMO for protracted periods, extended-duration studies are required to characterise long-term ECMO-induced haemostatic changes.

Platelet Function During Extracorporeal Membrane Oxygenation in Adult Patients

Objective: Hemorrhagic and thromboembolic complications are common during support with extracorporeal membrane oxygenation (ECMO). As platelets play a pivotal role in hemostasis, we aimed to clarify how ECMO support affects platelet function.

Methods: We included 33 adult patients undergoing ECMO support at a tertiary ECMO referral center at Aarhus University Hospital, Denmark. Blood samples were collected on the first morning following ECMO initiation, and subsequently every morning until the 7th (±1) day. Platelet aggregation was evaluated by whole blood impedance aggregometry (Multiplate^® Analyzer) using adenosine diphosphate (ADPtest), arachidonic acid (ASPItest), and thrombin-receptor-agonist-peptide-6 (TRAPtest) as agonists. A new model was applied, taking platelet count into consideration in interpretation of impedance aggregometry analyses. On the 1st and 3rd day, platelet activation was assessed by flow cytometry (Navios) using collagen-related peptide, ADP, TRAP, and arachidonic acid as agonists.

Results: Blood samples from all 33 patients were analyzed on day 1 of ECMO support; 24 patients were still receiving ECMO and analyzed on day 3; 12 patients were analyzed on day 7 (±1). After ECMO initiation, platelet counts decreased significantly (p < 0.002) and remained low during ECMO support. ECMO patients demonstrated significantly reduced platelet aggregation on day 1 compared with healthy controls (all p < 0.001). However, when taking platelet count into consideration, platelet aggregation relative to platelet count did not differ from healthy controls. Flow cytometry analyses demonstrated impaired platelet activation in ECMO patients on day 1 compared with healthy controls (all p < 0.03). No substantial difference was found in platelet activation from day 1 to day 3 on ECMO support.

Conclusions: Employing impedance aggregometry and flow cytometry, we found both impaired platelet aggregation and decreased platelet activation on day 1 of ECMO support compared with healthy controls. However, platelet aggregation was not impaired, when interpreted relative to the low platelet counts. Furthermore, levels of bound fibrinogen, on the surface of activated platelets in ECMO patients, were higher than in healthy controls. Together, these findings suggestively oppose that platelets are universally impaired during ECMO support. No marked difference in activation from day 1 to day 3 was seen during ECMO support.

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.

Recombinant Activated Factor VII for Exsanguinating Haemorrhage Post Bilateral Lung Transplantation for Extra-corporeal Lung Support-dependent Respiratory Failure

Following three weeks of extracorporeal lung support for acute respiratory distress syndrome, a 15-year-old male underwent bilateral lung transplantation. This procedure was complicated by massive postoperative haemorrhage. The administration of recombinant activated Factor VII was associated with improved haemostasis. However, development of cardiac tamponade soon after injection required emergency exploration and evacuation of a large mediastinal clot.

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.