Coagulation factor activity during neonatal extra-corporeal membrane oxygenation

Evaluation of acquired antithrombin deficiency in paediatric patients supported on extracorporeal membrane oxygenation

AIMS

There remains a paucity of literature regarding best practice for antithrombin (AT) monitoring, dosing and dose-response in paediatric extracorporeal membrane oxygenation (ECMO) patients.

METHODS

We conducted a retrospective cohort study at a quaternary care paediatric intensive care unit in all patients <18 years of age supported on ECMO from 1 June 2011 to 30 April 2020. Adverse events and outcomes were characterized for all ECMO runs. AT activity and replacement were characterized and compared between two clinical protocols. AT activities measured post- vs. pre-AT replacement were compared in order to characterize a dose-response relationship.

RESULTS

The final cohort included 191 patients with 201 ECMO runs and 2028 AT activity measurements. The median AT activity was 65% (interquartile range [IQR], 51-82) and 879 (43.3%) measurements met the criteria of deficient. The overall median AT dose and increase in AT activity were 50.6 units/kg/dose (IQR, 39.5-67.2) and 23.5% (IQR, 9.8-36.0), respectively. In the protocol that restricted AT activity measurements to clinical scenarios concerning for heparin resistance, there was significantly higher dosing in conjunction with significantly fewer overall administrations. Approximately one third of AT activity remained deficient after repletion. There was no difference in mechanical complications, reasons for discontinuation of ECMO support, time on ECMO or survival between protocols.

CONCLUSIONS

There was a high prevalence of AT deficiency in paediatric ECMO patients. An AT replacement protocol based on evaluating heparin resistance is associated with fewer AT administrations, with similar circuit and patient outcomes. Further data are needed to identify optimal dosing strategies.

Transfusion Strategies for Hemostatic Blood Products in Critically Ill Children: A Narrative Review and Update on Expert Consensus Guidelines

Critically ill children commonly receive coagulant products (plasma and/or platelet transfusions) to prevent or treat hemorrhage or correct coagulopathy. Unique aspects of pediatric developmental physiology, and the complex pathophysiology of critical illness must be considered and balanced against known transfusion risks. Transfusion practices vary greatly within and across institutions, and high-quality evidence is needed to support transfusion decision-making. We present recent recommendations and expert consensus statements to direct clinicians in the decision to transfuse or not to transfuse hemostatic blood products, including plasma, platelets, cryoprecipitate, and recombinant products to critically ill children.

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

OBJECTIVES

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

APPROACH AND RESULTS

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

CONCLUSION

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

Risk Factors and Outcomes for Patients with Bleeding Complications Receiving Extracorporeal Membrane Oxygenation: An Analysis of the Chinese Extracorporeal Life Support Registry

OBJECTIVE

Bleeding is a severe complication of patients supported with extracorporeal membrane oxygenation (ECMO). This study aimed to analyze the occurrence, risk factors, and clinical outcomes of patients on ECMO with bleeding complications.

METHODS

ECMO cases reported to the multicenter ECMO registry database of the Chinese Society of Extracorporeal Life Support (CSECLS) from January 2017 to December 2020 were enrolled. General information, ECMO indications, application, complications, and patient outcomes were collected and analyzed.

RESULTS

A total of 6541 ECMO patients from 112 centers were enrolled. Overall, 1185 patients (18.1%) presented with one of the following bleeding complications, including 82 cases (1.3%) with severe bleeding during ECMO catheterization, 462 cases (7.1%) with bleeding at the ECMO cannulation site, 200 cases (3.5%) with bleeding at the surgical site, 180 cases (2.8%) with cerebral hemorrhage, 99 cases (1.5%) with pulmonary hemorrhage, 200 cases (3.5%) with gastrointestinal hemorrhage, 82 cases (1.3%) with ECMO withdrawal, and 118 (1.8%) deaths due to severe bleeding. Extracorporeal cardiopulmonary resuscitation (ECPR) patients had the highest incidence of bleeding complications (22.4%), followed by those on circulatory support (18.7%) and respiratory support (15.4%) (p<0.001). Multivariate analysis showed that pediatric patients (odds ratio [OR] 1.509, p<0.001), patients receiving renal replacement therapy (OR 1.932, p<0.001), and patients receiving central ECMO cannulation (OR 3.023, p<0.001) were independent risk factors for all bleeding complications, while peripheral cannulation (OR 0.712, p<0.001) was an independent protective factor. Patients with any bleeding complication had significantly higher in-hospital mortality than patients without (61.9% vs. 46.3%, p<0.001).

CONCLUSION

Up to 18.1% of ECMO patients in the CSECLS registry experienced bleeding complications, which was associated with higher in-hospital mortality, especially in patients who received ECPR, patients on circulatory support, and pediatric patients, which should arouse the attention of clinicians.

Premature and Extracorporeal Life Support: Is it Time? A Systematic Review

Early preterm birth < 34 gestational weeks (GA) and birth weight (BW) <2 kg are relative contraindications for extracorporeal membrane oxygenation (ECMO). However, with improved technology, ECMO is presently managed more safely and with decreasing complications. Thus, these relative contraindications may no longer apply. We performed a systematic review to evaluate the existing literature on ECMO in early and late (34-37 GA) prematurity focusing on survival to hospital discharge and the complication intracranial hemorrhage (ICH). Data sources: MEDLINE, PubMed, Web of Science, Embase, and the Cochrane Database. Only publications in the English language were evaluated. Of the 36 included studies, 23 were related to ECMO support for respiratory failure, 10 for cardiac causes, and four for congenital diaphragmatic hernia (CDH). Over the past decades, the frequency of ICH has declined (89-21%); survival has increased in both early prematurity (25-76%), and in CDH (33-75%), with outcome similar to late prematurity (48%). The study was limited by an inherent risk of bias from overlapping single-center and registry data. Both the risk of ICH and death have decreased in prematurely born treated with ECMO. We challenge the 34 week GA time limit for ECMO and propose an international task force to revise current guidelines. At present, gestational age < 34 weeks might no longer be considered a contraindication for ECMO in premature neonates.

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.

Extracorporeal membrane oxygenation in critically ill neonatal and pediatric patients with acute respiratory failure: a guide for the clinician

Intro: Extracorporeal membrane oxygenation for neonatal and pediatric respiratory failure continues to demonstrate improving outcomes, largely due to advances in technology along with refined management strategies despite mounting patient acuity and complexity. Successful use of ECMO requires thoughtful initiation and candidacy strategies, along with reducing the risk of ventilator induced lung injury and the progression to multiorgan failure.Areas Covered: This review describes current ECMO management strategies for neonatal and pediatric patients with acute refractory respiratory failure and summarizes relevant published literature. ECMO initiation and candidacy, along with ventilator and sedation management, are highlighted. Additionally, rapidly expanding areas of interest such as anticoagulation strategies, transfusion thresholds, rehabilitation on ECMO, and drug pharmacokinetics are described.Expert Opinion: Over the last few decades, published studies supporting ECMO use for acute refractory respiratory failure, along with institutional experience, have resulted in increased utilization although more randomized-controlled trials are needed. Future research should focus on filling the knowledge gaps that remain regarding anticoagulation, transfusion thresholds, ventilator strategies, sedation, and approaches to rehabilitation to subsequently implement into clinical practice. Additionally, efforts should focus on well-designed trials, including population pharmacokinetic studies, to develop dosing recommendations.

Anticoagulation and Transfusion Management During Neonatal and Pediatric Extracorporeal Membrane Oxygenation: A Survey of Medical Directors in the United States

OBJECTIVES

To compare current practices within the United States of anticoagulation management and blood transfusion in neonatal and pediatric extracorporeal membrane oxygenation patients with a 2013 international report.

DESIGN

Cross-sectional survey distributed between August and December 2019.

SETTING

Extracorporeal Life Support Organization-registered neonatal and pediatric extracorporeal membrane oxygenation centers in the United States.

PARTICIPANTS

Extracorporeal membrane oxygenation medical directors.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Eighty-three medical directors at 108 centers responded. After removing four duplicate responses, 79 surveys were analyzed. Seventy-nine percent (n = 62) report a written extracorporeal membrane oxygenation protocol for both anticoagulation and blood product management. Ninety-four percent (n = 74) report unfractionated heparin as their primary anticoagulant; the remaining use the direct thrombin inhibitor, bivalirudin. Ninety percent (n = 71) report measuring antifactor Xa levels. Most centers report using a combination of assays to monitor heparin therapy, either antifactor Xa and activated partial thromboplastin time (54%) or more commonly antifactor Xa and activated clotting time (68%). Forty-one percent use viscoelastic tests to aid management. Goal monitoring levels and interventions generated by out of range values are variable. Fifty-one percent will replace antithrombin. Platelet transfusion thresholds vary by age and center with ranges from 50,000 to 100,000 cells/µL. Eighty-two percent of respondents are willing to participate in a randomized controlled trial comparing anticoagulation strategies for patients receiving extracorporeal membrane oxygenation.

CONCLUSIONS

Compared with the 2013 pediatric population, extracorporeal membrane oxygenation center anticoagulation and blood transfusion approaches continue to vary widely. Most report continued use of heparin as their primary anticoagulant and follow a combination of monitoring assays with the majority using the antifactor Xa assay in their practices, a significant shift from prior results. Antithrombin activity levels and viscoelastic tests are followed by a growing number of centers. Platelet transfusion thresholds continue to vary widely. Future research is needed to establish optimal anticoagulation and blood transfusion management.

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.

Venoarterial extra corporeal membrane oxygenation and blood component usage in pediatric patients undergoing cardiac surgery: Single centre experience

Background

Extra Corporeal Membrane Oxygenation (ECMO) is a well-known tool for providing life-saving support in patients developing post cardiotomy cardiogenic shock in post cardiac surgeries. The current study was designed to evaluate blood transfusion requirements and its relation to mortality in neonate and pediatric cardiac patients requiring venoarterial cardiac ECMO during post-operative period following cardiac surgery.

Materials and Methods

Overall 24 pediatric patients (including neonates) who underwent VA ECMO in post cardiac surgery at our institute from January 2016 to October 2017 were included in the study. The details of demographics, blood transfusion, ECMO, and morbidity and mortality were collected for all the patients.

Objective of the Study

The primary objective of our study was to assess the outcome of patients on ECMO in post pediatric cardiac surgery. The secondary objective of the study was to assess the effect of blood transfusion on the outcome of the patients.

Results

Overall mortality rate was 50% (n = 12). The overall transfusion rate of packed red blood cells was higher in patients who did not survive even after institution of VA ECMO. The transfusion of other blood products like platelets, cryoprecipitate, and fresh frozen plasma were also higher in this group of patients though it was statistically non-significant except for packed red cell transfusion. Though statistically non-significant, the patients who didn't survive even after institution of VA ECMO post-surgery had relatively higher mean age (703.88 ± 998.94 days) as compared to their counterparts (510.63 ± 384.36 days).

Conclusion

The use of ECMO is associated with considerable morbidity and mortality. Packed red cell transfusion is definitely higher in expired patients, indicative of deteriorated status of the patient. However, considering non-significant association of other blood components, except packed red cell it is recommended that patients' overall clinical condition should be taken into consideration for transfusion of blood products and not only targeting the transfusion triggers.

Evaluation of effect of scheduled fresh frozen plasma on ECMO circuit life: A randomized pilot trial

BACKGROUND

Factor consumption is common during ECMO complicating the balance of pro and anticoagulation factors. This study sought to determine whether transfusion of coagulation factors using fresh frozen plasma (FFP) increased ECMO circuit life and decreased blood product transfusion. Secondly, it analyzed the association between FFP transfusion and hemorrhagic and thrombotic complications.

STUDY DESIGN AND METHODS

Thirty-one pediatric ECMO patients between October 2013 and January 2016 at a quaternary care institution were included. Patients were randomized to FFP every 48 hours or usual care. The primary outcome was ECMO circuit change. Secondary outcomes included blood product transfusion, survival to decannulation, hemorrhagic and thrombotic complications, and ECMO costs.

RESULTS

Median (interquartile range [IQR]) number of circuit changes was 0 (0, 1). No difference was seen in percent days without a circuit change between intervention and control group, P = .53. Intervention group patients received median platelets of 15.5 mL/kg/d IQR (3.7, 26.8) vs 24.8 mL/kg/d (12.2, 30.8) for the control group (P = .16), and median packed red blood cells (pRBC) of 7.7 mL/kg/d (3.3, 16.3) vs 5.9 mL/kg/d (3.4, 18.7) for the control group, P = .60. FFP transfusions were similar with 10.2 mL/kg/d (5.0, 13.9) in the intervention group vs 8.8 (2.5, 17.7) for the control group, P = .98.

CONCLUSION

In this pilot randomized study, scheduled FFP did not increase circuit life. There was no difference in blood product transfusion of platelets, pRBCs, and FFP between groups. Further studies are needed to examine the association of scheduled FFP with blood product transfusion.

Hematologic concerns in extracorporeal membrane oxygenation

This ISTH "State of the Art" review aims to critically evaluate the hematologic considerations and complications in extracorporeal membrane oxygenation (ECMO). ECMO is experiencing a rapid increase in clinical use, but many questions remain unanswered. The existing literature does not address or explicitly state many pertinent details that may influence hematologic complications and, ultimately, patient outcomes. This review aims to broadly introduce modern ECMO practices, circuit designs, circuit materials, hematologic complications, transfusion-related considerations, age- and size-related differences, and considerations for choosing outcome measures. Relevant studies from the 2019 ISTH Congress in Melbourne, which further advanced our understanding of these processes, will also be highlighted.

Impact of delayed systemic heparinization on postoperative bleeding and thromboembolism during post-cardiotomy extracorporeal membrane oxygenation in neonates

INTRODUCTION

Veno-arterial extracorporeal membrane oxygenation is well-established for pediatric patients with post-cardiotomy heart failure. However, extracorporeal membrane oxygenation support is associated with major complications, that is, hemorrhage and thromboembolism. We seek to report our experience with delayed systemic heparinization during neonatal cardiac extracorporeal membrane oxygenation and its impact on bleeding and thromboembolism.

METHODS

We retrospectively identified 15 consecutive neonates who were placed on extracorporeal membrane oxygenation after congenital heart surgery during a period of 3 years (2015-2017). Our anticoagulation protocol consisted of full heparin reversal by protamine after switching from cardiopulmonary bypass to extracorporeal membrane oxygenation (target activated clotting time: 120 ± 20 seconds). Administration of systemic heparinization was delayed until postoperative drainage volume declined to <1 mL/kg/h. Primary study endpoints were thromboembolism, bleeding, and requirement of blood products on extracorporeal membrane oxygenation.

RESULTS

Our cohort (mean age: 13 ± 2.6 days; mean weight: 3.1 ± 0.3 kg; 66.7% male) required post-cardiotomy extracorporeal membrane oxygenation with a mean support time of 4.5 ± 2.2 days. Systemic heparinization was delayed averagely for 18.1 ± 9.3 hours. No thromboembolic events were observed on extracorporeal membrane oxygenation or after weaning. Relevant surgical site bleeding occurred in two patients (13.3%) requiring re-thoracotomy on the first postoperative day. Analysis of transfusion volumes revealed 24.5 ± 21.9 mL/kg/d mean packed red blood cells, 9.6 ± 7.1 mL/kg/d mean fresh frozen plasma, and 7.5 ± 5.7 mL/kg/d mean platelets. In-hospital survival was 86.6% (n = 13).

CONCLUSION

In this retrospective analysis, the results of delayed systemic heparinization in neonatal post-cardiotomy extracorporeal membrane oxygenation could lead one to conclude that this routine is safe and favorable with low risk for thromboembolic events, reduced postoperative hemorrhage, and reduced blood product utilization.

Updates in Pediatric Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation is an increasingly used mode of life support for patients with cardiac and/or respiratory failure refractory to conventional therapy. This review provides a synopsis of the evolution of extracorporeal life support in neonates, infants, and children and offers a framework for areas in need of research. Specific aspects addressed are the changing epidemiology; technologic advancements in extracorporeal membrane oxygenation circuitry; the current status and future direction of anticoagulation management; sedative and analgesic strategies; and outcomes, with special attention to the lessons learned from neonatal survivors.

Anticoagulation in neonatal ECMO

Despite advances made in technology and neonatal intensive care, the rate of hemorrhagic and thrombotic complications remains unacceptably high in patients undergoing extracorporeal membrane oxygenation (ECMO) and these complications negatively impact morbidity and mortality. Management of anticoagulation in neonates who have a developing hemostatic system is vastly different from adults and poses unique challenges. Variation in practice among ECMO centers regarding anticoagulation monitoring and titration reflects the lack of high-quality evidence. Novel anticoagulants may offer alternative options, though their impact on outcomes is yet to be demonstrated. In this chapter, we review the hemostatic alterations that occur during ECMO with a focus on current approaches and limitations to anticoagulation titration in neonates on ECMO.

Soluble fibrin is a useful marker for predicting extracorporeal membrane oxygenation circuit exchange because of circuit clots

A circuit clot is one of the most frequent complications during extracorporeal membrane oxygenation (ECMO) support. We identify coagulation/fibrinolysis markers for predicting ECMO circuit exchange because of circuit clots during ECMO support. Ten patients with acute pulmonary failure who underwent veno-venous ECMO were enrolled between January 2014 and December 2016. ECMO support lasted 106 days. The 6 days on which the ECMO circuits were exchanged were considered as circuit clot (+) group, while the remaining 100 days were considered as circuit clot (-) group. The predictors of ECMO circuit exchange because of circuit clots were identified. The mean duration of ECMO support was 10 ± 13 days, and the mean number of ECMO circuit exchange was 0.6 ± 1.1 times per patient. Thrombin-antithrombin complex (TAT) and soluble fibrin (SF) were higher in the circuit clot (+) group than in the circuit clot (-) group (both P < 0.01). According to a multivariate analysis, SF was the only independent predictor of ECMO circuit exchange (P < 0.01). The odds ratio (confidence intervals) for SF (10 µg/ml) was 1.20 (1.06-1.36). The area under the curve and optimal cut-off value were 0.95 and 101 ng/ml for SF (sensitivity, 100%; specificity, 89%). SF may be useful in predicting ECMO circuit exchange because of circuit clots.

Anticoagulation with VADs and ECMO: walking the tightrope

The evolution of devices for mechanical circulatory support (MCS), including ventricular assist devices (VADs) for patients with heart failure and extracorporeal membrane oxygenation (ECMO) for patients with acute cardiac or respiratory failure, has improved survival for subsets of critically ill children and adults. The devices are intricate and complex, allowing blood to bypass the heart or lungs (or both). As blood flows through these artificial devices, normal hemostasis is disrupted, coagulation is promoted, and in the absence of anticoagulation, a thrombus may form in the device, resulting in device failure or embolic stroke. Therefore, anticoagulation is necessary to prevent thrombus formation and maintain device function. However, patients on MCS also have very high bleeding rates. Titrating anticoagulation to prevent hemorrhagic complications and thrombotic events can be a challenge, and hematologists may be consulted in complex cases. Substantial variability remains in the approach to anticoagulant and antiplatelet therapy for patients on MCS, largely because of the lack of high-quality data. Improvements in the design and manufacture of these devices, as well as in the individualized titration of antithrombotic intensity, are expected to enhance outcomes. Several factors pertaining to both the device and the patient (adult and children) should be considered when attempting to optimize this delicate balance.

Coagulation monitoring correlation with heparin dose in pediatric extracorporeal life support

Objectives:

Extracorporeal Life Support (ECLS) risks thrombotic and hemorrhagic complications. Optimal anti-coagulation monitoring is controversial. We compared coagulation tests evaluating the heparin effect in pediatric ECLS.

Methods:

A retrospective study of children (<18yrs) undergoing ECLS over 12 months in a tertiary pediatric intensive care unit (PICU). Variables included anti-Factor Xa activity (anti-Xa), activated partial thromboplastin time (aPTT), activated clotting time (ACT) and thromboelastogram (TEG®6s) parameters: ratio and delta reaction (R) times (the ratio and difference, respectively, between R times in kaolin assays with and without heparinase). Test results were correlated with unfractionated heparin infusion rate (IU/kg/hr) at the time of sampling. Mean test results of each ECLS run were evaluated according to the presence/absence of complications.

Results:

Thirty-two ECLS runs (31 patients) generated 695 data-points for correlation. PICU mortality was 22% and the thrombotic complication rate was 66%. The proportion of variation in coagulation test results explained by heparin dose was 13.3% for anti-Xa, 11.9% for ratio R time, and 9.9% for delta R time, compared with <1% for ACT and aPTT. Incorporating individual variation, age and antithrombin activity in a model with heparin dose explained less than 50% of the variation in test results. Correlation varied according to age, day of ECLS run and between individuals, with parallel dose-response lines noted between patients. Significantly lower mean anti-Xa was observed in PICU non-survivors and runs with thrombosis.

Conclusion:

Lower anti-Xa was observed in ECLS runs with complications. Although absolute results from anti-Xa and TEG6®s showed the best correlation with heparin dose, a large proportion of variation in results was unexplained by heparin, while dose response was similar between individuals. Population pharmacokinetic/pharmacodynamic modelling is required, as well as prospective trials to delineate the superior means of adjusting heparin therapy to prevent adverse clinical outcomes.

Continuous Antithrombin III Administration in Pediatric Veno-Arterial Extracorporeal Membrane Oxygenation

The purpose of this retrospective case-control study is to determine the effect of continuous antithrombin III (ATIII) infusion on extracorporeal membrane oxygenation (ECMO) coagulation. All ECMO patients within the pediatric intensive care unit from January 2012 to July 2014 were included. Comparison was made between those who received continuous infusion ATIII through a standardized replacement protocol with historic controls receiving intermittent ATIII doses. Patients receiving the continuous infusion ATIII protocol spent more time in goal ACT range (71.9% vs 52.2%, p < 0.0001). Mean daily ATIII activity was also increased in study group (77.3% versus 68.6%, p = 0.04). No statistical differences in number of heparin dose changes per day (3 versus 3.22, p = 0.90) were present between the 2 groups. Only 28% of the historic controls receiving intermittent ATIII doses achieved normal ATIII activity as compared with 80% of study patients (p = 0.24). Maximum heparin dose was also lower in continuous infusion protocol group (p < 0.01). Compared with nonprotocolized intermittent dosing, the use of a continuous infusion ATIII protocol demonstrated increased time within goal ACT range at a lower heparin dose, no increase in hemostatic complications, and trends toward fewer heparin changes and lower blood product usage.

Outcomes following routine antithrombin III replacement during neonatal extracorporeal membrane oxygenation

BACKGROUND

We sought to examine the effect of routine antithrombin III (AT3) infusion on hemorrhagic and thrombotic complications, blood product utilization, and circuit lifespan in neonatal extracorporeal membrane oxygenation (ECMO).

METHODS

We performed a retrospective cohort study of 162 infants placed on ECMO for hypoxic respiratory failure. Infants requiring ECMO for primary cardiac support were excluded. Demographic data, time on ECMO, blood product usage, coagulation profile, and complications were compared between 90 control patients and 72 patients treated with AT3.

RESULTS

Infants receiving AT3 during ECMO had less thrombotic and similar bleeding complications as compared to infants receiving standard anticoagulation therapy. Total blood product infusion during ECMO was decreased (54.7±20.1 vs. 67.4±34.9mL/kg per day, p=0.001) in infants receiving AT3 during ECMO. Tighter control of activated clotting time and higher serum heparin anti-Xa levels were observed in the AT3 cohort during the first days of ECMO support. 1st ECMO circuit lifespan did not differ between groups.

CONCLUSIONS

Routine administration of AT3 in neonates receiving ECMO therapy was associated with tighter control of anticoagulation and a reduction in thrombotic events without increasing unwanted bleeding. However, circuit lifespan was unaffected.

LEVEL OF EVIDENCE

Level III.

Blood Transfusion Strategies in Patients Undergoing Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is frequently associated with bleeding and coagulopathy complications, which may lead to the need for transfusion of multiple blood products. However, blood transfusions are known to increase morbidity and mortality, as well as hospital cost, in critically ill patients. In current practice, patients on ECMO receive a transfusion, on average, of 1-5 packed red blood cells (RBCs)/day, with platelet transfusion accounting for the largest portion of transfusion volume. Generally, adult patients require more transfusions than neonates or children, and patients receiving venovenous ECMO for respiratory failure tend to need smaller transfusion volumes compared to those receiving venoarterial ECMO for cardiac failure. Observation studies have reported that a higher transfusion volume was associated with increased mortality. To date, the evidence for transfusion in patients undergoing ECMO is limited; most knowledge on transfusion strategies was extrapolated from studies in critically ill patients. However, current data support a restrictive blood transfusion strategy for ECMO patients, and a low transfusion trigger seems to be safe and reasonable.

Challenges with Navigating the Precarious Hemostatic Balance during Extracorporeal Life Support: Implications for Coagulation and Transfusion Management

For the past four decades, extracorporeal life support (ECLS) has been used to treat critically ill adult and pediatric patients with cardiac and/or respiratory failure, and there are increasingly numbers of centers worldwide performing ECLS for numerous indications. Despite the progress with advancing the technology, hemorrhagic and thrombotic complications are frequently reported and associated with worse outcomes, but the exact cause is often elusive or multifactorial. As a result of the interaction between blood and an artificial circuit, anticoagulation is necessary and there is resultant activation of coagulation, fibrinolysis, as well as, an increased inflammatory response. While unfractionated heparin (UFH) remains the mainstay anticoagulant used during ECLS, there is a paucity of published data to develop a universal anticoagulation guideline and centers are forced to create individualized protocols to guide anticoagulation management while lacking expertise. From an international survey, centers often use a combination of tests, which in turn result in discordant results and confused management. Studies are urgently needed to investigate optimization of current anticoagulation strategies with UFH, as well as, use of alternative anticoagulants and non-thrombogenic biomaterials. Blood transfusion during extracorporeal support typically occurs for several reasons, which includes circuit priming, restoration of oxygen carrying capacity, maintenance of a hemostatic balance, and treatment of hemorrhagic complications. As a result, the majority of patients will have been exposed to at least one blood product during extracorporeal support and transfusion utilization is high. ECLS Centers have adopted transfusion thresholds based upon practice rather than evidence as there have been no prospective studies investigating the efficacy of red cell (RBC) transfusion in patients receiving extracorporeal support. In addition, RBC transfusion has been associated with increased mortality in ECLS in several retrospective studies. Additional studies are needed to establish evidence based thresholds for transfusion support and diagnostics to guide transfusion therapy to assess efficacy of transfusion in this population, as well as, exploration of alternatives to transfusion.

Argatroban as an alternative to heparin in extracorporeal membrane oxygenation circuits

We investigated the anticoagulant effects of argatroban, a direct thrombin inhibitor, versus heparin in extracorporeal membrane oxygenation (ECMO) circuits. Three sham circuits were prepared according to our hospital’s standard practice and run for six hours simultaneously. Two circuits were anticoagulated with argatroban (one with heparin in the wet prime and one without). One circuit had heparin in the initial prime and was then anticoagulated with heparin. We measured thrombin generation (prothrombin fragment 1+2, D-dimer and thrombin-antithrombin complexes), activated clotting times (ACTs) and partial thromboplastin times (aPTTs), and monitored thrombus formation using thromboelastography. ACTs were >1000 s in each circuit throughout assessment. No clot initiation was detected by thromboelastography. Thrombin generation was decreased in circuits anticoagulated with argatroban versus heparin, despite aPTTs being less prolonged. These results suggest that argatroban may be more efficacious than heparin for anticoagulation in ECMO. Additional studies are warranted to further evaluate argatroban in this setting.

Extracorporeal membrane oxygenation-hemostatic complications

The use of extracorporeal membrane oxygenation (ECMO) support for cardiac and respiratory failure has increased in recent years. Improvements in ECMO oxygenator and pump technologies have aided this increase in utilization. Additionally, reports of successful outcomes in supporting patients with respiratory failure during the 2009 H1N1 pandemic and reports of ECMO during cardiopulmonary resuscitation have led to increased uptake of ECMO. Patients requiring ECMO are a heterogenous group of critically ill patients with cardiac and respiratory failure. Bleeding and thrombotic complications remain a leading cause of morbidity and mortality in patients on ECMO. In this review, we describe the mechanisms and management of hemostatic, thrombotic and hemolytic complications during ECMO support.

Antithrombin III supplementation on extracorporeal membrane oxygenation: impact on heparin dose and circuit life

Antithrombin III (ATIII) is used during extracorporeal membrane oxygenation (ECMO) based on physiologic rationale and studies during cardiopulmonary bypass. In February 2008, our institution began using ATIII as replacement for low ATIII activity (<70%) in patients supported with ECMO. We hypothesized that ATIII supplementation would reduce heparin infusion rates, increase unfractionated heparin anti-Xa levels, and prolong ECMO circuit life. Data from 40 consecutive patients (45 deployments) requiring ECMO support for >72 hours with venoarterial ECMO from January 1, 2007, through December 31, 2008, were collected. Antithrombin III concentrate was administered for ATIII activity <70% at the discretion of the attending physician. The primary outcome was whether the heparin infusion rate was reduced by 10% or more as a result of ATIII administration. No difference in heparin infusion rate (p = 0.245) as a result of ATIII administration was observed. Anti-Xa levels were lower before ATIII administration (p< 0.001) and were increased after ATIII administration (p < 0.001). There was an increased frequency of circuit failure in ATIII treatment group compared with nontreatment group (p = 0.018). Neither heparin responsiveness nor circuit life was enhanced by daily ATIII supplementation for activity <70%. Future studies are warranted to evaluate the effectiveness of antithrombin replacement.

Blood Component Usage during Extracorporeal Membrane Oxygenation: Experience in 98 Patients at a Latin-American Tertiary Hospital

Background/Aims

Hemorrhagic complications during ECMO may affect a large proportion of the patients depending on the clinical setting. To guarantee optimal delivery of blood products to these patients, blood banks require updated information on the transfusion requirements. Few studies to date provide this information. This work assesses transfusion requirements in neonates and children during ECMO during the past 9 years.

Methods

We reviewed blood bank and hospital records of patients who underwent ECMO at our institution between May 2003 and May 2012. Data obtained included age, weight, diagnosis, type, length of ECMO, and daily transfusion requirements during ECMO. Descriptive and non-parametric inferential statistic analyses were performed. Our series included 98 patients.

Results

Mean time of patients on ECMO was 9.2 days, with the longest treatment spanning 22 days. Mean daily transfusion requirements were 39.5 ml/kg of RBC, 12.9 ml/kg of plasma, 34.3 ml/kg of platelets and 1.4 ml/kg of cryoprecipitate. Patients who underwent ECMO due to cardiac disease or congenital diaphragmatic hernia (CDH) required significantly higher transfusion volumes of plasma (p<0.05), platelets (p< 0.05) and cryoprecipitate (p<0.05) when compared to patients underwent ECMO due to respiratory disease. Concomitant with the aging of ECMO circuits, patients showed increased requirements of RBC, plasma, and CRYO around the seventh day of the ECMO run. This effect was not observed for platelets, which remained nearly consistent around 2.2 transfusions/day.

Conclusions

ECMO patients required significant transfusion support, which was particularly higher among patients who underwent ECMO due to cardiac disease or congenital diaphragmatic hernia.

Anticoagulation monitoring during pediatric extracorporeal membrane oxygenation

The best method of monitoring anticoagulation during extracorporeal membrane oxygenation (ECMO) is unknown. We conducted a prospective observational study in a tertiary pediatric intensive care unit. Antifactor Xa, antithrombin (AT), and factor VIII activity (FVIII) were measured in blood samples collected at 6, 12, and every 24 hours, respectively, of ECMO. We enrolled 34 children who underwent 35 ECMO runs from April 2008 to September 2010. Activated clotting time (ACT) and heparin doses were higher, whereas antifactor Xa levels were lower in neonates compared to infants/children. Median antifactor Xa was 0.4 IU/ml, median AT was 60%, and median FVIII was 67%. Heparin infusion rate, antifactor Xa, and antithrombin (AT) increased, FVIII was stable, and ACT decreased with each day on ECMO. ACT had poor agreement with antifactor Xa (42%). AT was inversely correlated with ACT (r = -0.33), even after adjusting for heparin dose, and positively correlated with antifactor Xa (r = 0.57). This study emphasizes the age differences as well as the variability over days of coagulation monitoring assays during ECMO. ACT is poorly correlated with antifactor Xa and AT modifies the relationship between ACT and the heparin dose, indicating that results should be interpreted with caution when managing anticoagulation on ECMO. Additional studies are warranted to determine optimal ECMO anticoagulation monitoring.

Anticoagulation for pediatric mechanical circulatory support

Extracorporeal life support applications have evolved considerably in recent years. However, the blood-biomaterial interface remains incompletely understood, and management of the acute inflammatory response and coagulation pathways continues to be challenging. At present, the gold standard for anticoagulation is unfractionated heparin. Since the inception of extracorporeal life support, the mainstay for anticoagulation monitoring has been activated clotting time. However, alongside the technological evolution in extracorporeal life support, the methods for monitoring heparin have also become more sophisticated, adding additional layers of complexity to creating an ideal safe protocol for anticoagulation during extracorporeal life support. To address this, the Extracorporeal Life Support Organization has formed an Anticoagulation Task Force to help direct both a consensus statement and potential guidelines within which the multiple monitoring methods can be customized for extracorporeal life support. One key question that remains in the use of these monitoring methods is whether the objective during extracorporeal life support is to anticoagulate the circuit to prevent thrombus formation within the extracorporeal device or whether it is to systemically anticoagulate the patient. This review details all current monitoring methods and highlights how they can be used during pediatric mechanical circulatory support.

Variability in anticoagulation management of patients on extracorporeal membrane oxygenation: an international survey

OBJECTIVE

The objective of this study was to determine current practices of anticoagulation in patients on extracorporeal membrane oxygenation.

DESIGN

Internet-based cross-sectional survey distributed between November 2010 and May 2011.

SETTING

Extracorporeal Life Support Organization-registered extracorporeal membrane oxygenation centers internationally.

PARTICIPANTS

: Extracorporeal membrane oxy genation medical directors and coordinators.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

There were 121 responses from extracorporeal membrane oxy genation medical directors and coordinators at 187 Extracorporeal Life Support Organization centers with access to the survey. Eighty-four of 117 (72%) respondents reported having a written institutional extracorporeal membrane oxy genation protocol for both anticoagulation and blood product management at their institutions. Sixty-nine of 117 (59%) respondents reported use of tip-to-tip or partially heparin-bonded circuits. Unfractionated heparin was used at all centers; only 8% of respondents indicated use of alternative anticoagulation medications in the six months prior to the survey. The preferred method of anticoagulation monitoring was the serial measurement of activated clotting time, as reported by 97% of respondents. In this survey, 82% of respondents reported antithrombin III testing, 65% reported anti-factor Xa testing, and 43% reported use of thromboelastography during extracorporeal membrane oxy genation. Goal ranges for these three tests and interventions triggered by out-of-range values were found to be variable.

CONCLUSIONS

Extracorporeal membrane oxy genation anticoagulation management policies vary widely by center. The majority of extracorporeal membrane oxy genation programs employ activated clotting time as the preferred anticoagulation monitoring tool. The coagulation system is also monitored using more specific markers such as antithrombin III, anti-factor Xa, and thromboelastography by a large number of centers. Future research is needed to elucidate optimal anticoagulation management and improve outcomes.

Anticoagulation and coagulation management for ECMO

Advances in extracorporeal membrane oxygenation (ECMO) management have helped to reduce complications compared with its inception but they remain high. The principal causes of mortality and morbidity are bleeding and thrombosis. The nonbiologic surface of an extracorporeal circuit provokes a massive inflammatory response leading to consumption and activation of procoagulant and anticoagulant components. The vast differences in neonatal and adult anticoagulation and transfusion requirements demands tremendous clinical knowledge to provide the best care. Increased use of thrombelastogram will complement other methods currently being used to improved care. Methods to recognize the level of thrombin formation at the bedside could help reduce neurologic complications. ECMO requires a multidisciplinary team approach to achieve the best outcomes.

Mechanical component failures in 28,171 neonatal and pediatric extracorporeal membrane oxygenation courses from 1987 to 2006

OBJECTIVE

To provide a descriptive summary of mechanical component failure associated with extracorporeal membrane oxygenation (ECMO), and to examine patient and ECMO variables that may be associated with mechanical component failure and guide further study. We hypothesized that duration of ECMO, era of ECMO, indication for ECMO, age of patient, and center ECMO volume would be associated with mechanical component failure.

DESIGN

Retrospective cohort study.

PATIENTS AND METHODS

Extracorporeal Life Support Organization registry was queried for all neonatal and pediatric ECMO courses recorded. Each ECMO course was treated as an independent event, and was included if duration was > or =25 hrs with occurrence between 1987 and 2007. Courses with a duration >458 hrs or with an indication for ECMO during cardiopulmonary resuscitation were excluded from analysis. Mechanical component failure data were extracted from the Extracorporeal Life Support Organization registry for the oxygenator, raceway, other tubing, pigtail connectors, heat exchanger, and air in the circuit.

RESULTS

A total of 28,171 independent ECMO courses were included for analysis, of which 14.9% were associated with a mechanical component failure. Duration of ECMO, age group of patient, era of ECMO, and indication for ECMO were all associated with mechanical component failure. From our predictive model, we observed a continuous nonlinear relation suggesting increasing probability of mechanical component failure with increasing duration of ECMO support.

CONCLUSIONS

Mechanical component failure over the course of this study was infrequent during neonatal and pediatric ECMO, and declined across eras as experience with the therapy grew. Increasing duration of ECMO was associated with an increasing probability of mechanical component failure. Indication for ECMO and patient age were also statistically associated with mechanical component failure probability, but ECMO center volume was not.

Factors influencing the outcome of paediatric cardiac surgical patients during extracorporeal circulatory support

BACKGROUND

Veno-arterial extracorporeal membrane oxygenation (ECMO) is a common modality of circulatory assist device used in children. We assessed the outcome of children who had ECMO following repair of congenital cardiac defects (CCD) and identified the risk factors associated with hospital mortality.

METHODS

From April 1990 to December 2003, 53 patients required ECMO following surgical correction of CCD. Retrospectively collected data was analyzed with univariate and multivariate logistic regression analysis.

RESULTS

Median age and weight of the patients were 150 days and 5.4 kgs respectively. The indications for ECMO were low cardiac output in 16, failure to wean cardiopulmonary bypass in 13, cardiac arrest in 10 and cardio-respiratory failure in 14 patients. The mean duration of ECMO was 143 hours. Weaning off from ECMO was successful in 66% and of these 83% were survival to hospital-discharge. 37.7% of patients were alive for the mean follow-up period of 75 months. On univariate analysis, arrhythmias, ECMO duration >168 hours, bleeding complications, renal replacement therapy on ECMO, arrhythmias and cardiac arrest after ECMO were associated with hospital mortality.On multivariate analysis, abnormal neurology, bleeding complications and arrhythmias after ECMO were associated with hospital mortality. Extra and intra-thoracic cannulations were used in 79% and 21% of patients respectively and extra-thoracic cannulation had significantly less bleeding complications (p = 0.031).

CONCLUSION

ECMO provides an effective circulatory support following surgical repair of CCD in children. Extra-thoracic cannulation is associated with less bleeding complications. Abnormal neurology, bleeding complications on ECMO and arrhythmias after ECMO are poor prognostic indicators for hospital survival.

Epidural hemorrhage complicating extracorporeal life support in a neonate with respiratory failure

Whereas bleeding represents the most common complication of a patient on extracorporeal life support, intracranial hemorrhage represents the most common bleeding complication. We report the first known case in the English literature of an epidural hemorrhage complicating extracorporeal life support in a neonate with respiratory failure. Ultrasound findings closely mimic those of a posterior fossa hemorrhage. We speculate that the coagulopathy associated with the use of ECLS may have contributed to the formation of the epidural hemorrhage.

Comparison of Methods for Intravenous Infusion of Fat Emulsion During Extracorporeal Membrane Oxygenation

STUDY OBJECTIVES

To characterize the effects of infusing fat emulsion during neonatal extracorporeal membrane oxygenation (ECMO) by comparing results from patients receiving fat emulsion through the ECMO circuit with those receiving fat emulsion through separate intravenous access. A second goal was to identify the optimal route for administration.

DESIGN

Prospective, randomized, open-label trial.

SETTING

Neonatal intensive care unit in a 106-bed quaternary care pediatric hospital.

SUBJECTS

Nine neonates receiving ECMO who required intravenous nutrition. Intervention. Patients received 1-3 g/kg/day of fat emulsion into either the ecmo circuit or separate intravenous access.

MEASUREMENTS AND MAIN RESULTS

The ECMO circuit and samples of blood were evaluated hourly for phase separation, layering out of the emulsion from blood, agglutination, and blood clots. After completion, the oxygenators were dissected and examined. Data were compared with an unpaired t test. The characteristics of the groups were similar, except for a higher mean weight in the ECMO circuit group (3.6 +/- 0.3 kg vs 2.8 +/- 0.4 kg, p=0.03). The mean +/- SD triglyceride level during the study was 87 +/- 79 mg/dl, with no significant difference between the two groups. Two patients in each group had elevated triglyceride levels. No cases of phase separation occurred. In the five patients who received fat emulsion into the ECMO circuit, three had layering out of the emulsion and agglutination, and all developed clots in the circuit despite adequate anticoagulation. Of the four patients in the intravenous-access group, one had layering and agglutination, and two had blood clots.

CONCLUSIONS

Although both methods were associated with layering out, agglutination, and clot formation, these effects occurred more frequently with administration into the ECMO circuit, particularly in areas of stasis. This may result in disruption of normal ECMO blood flow and impaired delivery of calories. Fat emulsion should therefore be administered through separate intravenous access during ECMO whenever possible.

Craniotomy during ECMO in a severely traumatized patient

Extracorporeal membrane oxygenation (ECMO) can be a last resort treatment in acute respiratory distress syndrome after thoracic trauma. However, co-existent brain trauma is considered to be a contra-indication for ECMO. This is the first report on successful craniotomy under ECMO treatment in a multiply traumatized patient with severe thoracic and brain injuries. This successful treatment with beneficial neurological outcome suggests that ECMO therapy should not be withheld from severely injured patients with combined brain and thoracic trauma presenting with life-threatening hypoxemia. Moreover, even craniotomy may be performed during ECMO therapy without major bleeding and adverse effects on neurological function.

ECMO for neonatal respiratory failure

Extracorporeal membrane oxygenation (ECMO) has been offered as a life-saving technology to newborns with respiratory and cardiac failure refractory to maximal medical therapy. ECMO has been used in treatment of neonates with a variety of cardio-respiratory problems, including meconium aspiration syndrome (MAS), persistent pulmonary hypertension of the neonate (PPHN), congenital diaphragmatic hernia (CDH), sepsis/pneumonia, respiratory distress syndrome (RDS), air leak syndrome, and cardiac anomalies. For this group of high-risk neonates with an anticipated mortality rate of 80% to 85%, ECMO has an overall survival rate of 84%, with recent data showing nearly 100% survival in many diagnostic groups. This article reviews the current selection criteria for ECMO and the clinical management of neonates on ECMO, and discusses the long-term outcome of neonates treated with ECMO.