Bleeding and Thrombosis With Pediatric Extracorporeal Life Support: A Roadmap for Management, Research, and the Future From the Pediatric Cardiac Intensive Care Society: Part 1

Antifibrinolytic and Adjunct Hemostatic Agents: The Pediatric Extracorporeal Membrane Oxygenation Anticoagulation CollaborativE Consensus Conference

OBJECTIVES

To derive systematic-review informed, modified Delphi consensus regarding antifibrinolytic and adjunct hemostatic agents in neonates and children supported with extracorporeal membrane oxygenation (ECMO) for the Pediatric ECMO Anticoagulation CollaborativE consensus conference.

DATA SOURCES

A structured literature search was performed using PubMed, EMBASE, and Cochrane Library (CENTRAL) databases from January 1988 to May 2021.

STUDY SELECTION

Use of antifibrinolytics (epsilon-aminocaproic acid [EACA] or tranexamic acid), recombinant factor VII activated (rFVIIa), or topical hemostatic agents (THAs).

DATA EXTRACTION

Two authors reviewed all citations independently, with a third independent reviewer resolving conflicts. Eleven references were used for data extraction and informed recommendations. Evidence tables were constructed using a standardized data extraction form.

MEASUREMENTS AND MAIN RESULTS

Risk of bias was assessed using the Quality in Prognosis Studies tool. The evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation system. Forty-eight experts met over 2 years to develop evidence-based recommendations and, when evidence was lacking, expert-based consensus statements for the management of bleeding and thrombotic complications in pediatric ECMO patients. A web-based modified Delphi process was used to build consensus via the Research And Development/University of California Appropriateness Method. Consensus was defined as greater than 80% agreement. One weak recommendation and three consensus statements are presented.

CONCLUSIONS

Evidence supporting recommendations for administration of antifibrinolytics (EACA or tranexamic acid), rFVIIa, and THAs were sparse and inconclusive. Much work remains to determine effective and safe usage strategies.

Executive Summary: The Pediatric Extracorporeal Membrane Oxygenation Anticoagulation CollaborativE (PEACE) Consensus Conference

OBJECTIVES

To present recommendations and consensus statements with supporting literature for the clinical management of neonates and children supported with extracorporeal membrane oxygenation (ECMO) from the Pediatric ECMO Anticoagulation CollaborativE (PEACE) consensus conference.

DATA SOURCES

Systematic review was performed using PubMed, Embase, and Cochrane Library (CENTRAL) databases from January 1988 to May 2021, followed by serial meetings of international, interprofessional experts in the management ECMO for critically ill children.

STUDY SELECTION

The management of ECMO anticoagulation for critically ill children.

DATA EXTRACTION

Within each of eight subgroup, two authors reviewed all citations independently, with a third independent reviewer resolving any conflicts.

DATA SYNTHESIS

A systematic review was conducted using MEDLINE, Embase, and Cochrane Library databases, from January 1988 to May 2021. Each panel developed evidence-based and, when evidence was insufficient, expert-based statements for the clinical management of anticoagulation for children supported with ECMO. These statements were reviewed and ratified by 48 PEACE experts. Consensus was obtained using the Research and Development/UCLA Appropriateness Method. Results were summarized using the Grading of Recommendations Assessment, Development, and Evaluation method. We developed 23 recommendations, 52 expert consensus statements, and 16 good practice statements covering the management of ECMO anticoagulation in three broad categories: general care and monitoring; perioperative care; and nonprocedural bleeding or thrombosis. Gaps in knowledge and research priorities were identified, along with three research focused good practice statements.

CONCLUSIONS

The 91 statements focused on clinical care will form the basis for standardization and future clinical trials.

Concurrent use of continuous kidney replacement therapy during extracorporeal membrane oxygenation: what pediatric nephrologists need to know-PCRRT-ICONIC practice points

Extracorporeal membrane oxygenation (ECMO) provides temporary cardiorespiratory support for neonatal, pediatric, and adult patients when traditional management has failed. This lifesaving therapy has intrinsic risks, including the development of a robust inflammatory response, acute kidney injury (AKI), fluid overload (FO), and blood loss via consumption and coagulopathy. Continuous kidney replacement therapy (CKRT) has been proposed to reduce these side effects by mitigating the host inflammatory response and controlling FO, improving outcomes in patients requiring ECMO. The Pediatric Continuous Renal Replacement Therapy (PCRRT) Workgroup and the International Collaboration of Nephrologists and Intensivists for Critical Care Children (ICONIC) met to highlight current practice standards for ECMO use within the pediatric population. This review discusses ECMO modalities, the pathophysiology of inflammation during an ECMO run, its adverse effects, various anticoagulation strategies, and the technical aspects and outcomes of implementing CKRT during ECMO in neonatal and pediatric populations. Consensus practice points and guidelines are summarized. ECMO should be utilized in patients with severe acute respiratory failure despite the use of conventional treatment modalities. The Extracorporeal Life Support Organization (ELSO) offers guidelines for ECMO initiation and management while maintaining a clinical registry of over 195,000 patients to assess outcomes and complications. Monitoring and preventing fluid overload during ECMO and CKRT are imperative to reduce mortality risk. Clinical evidence, resources, and experience of the nephrologist and healthcare team should guide the selection of ECMO circuit.

A proposed objective scale for extracorporeal membrane oxygenation circuit thrombosis

Patients undergoing extracorporeal membrane oxygenation (ECMO) are susceptible to thrombosis, which is a major cause of death and morbidity. However, there is no objective ECMO thrombosis grading scale to standardize evaluation, guide treatment, and facilitate further research. In this letter, we propose an objective grading scale for ECMO circuit thrombosis based on physical characteristics and location within the circuit. This ECMO thrombosis scale will allow for protocolized escalation of ECMO thrombosis treatment, ranging from watchful observation, intensified anticoagulation, and circuit exchange.

Hemostatic complications and systemic heparinization in pediatric post-cardiotomy veno-arterial extracorporeal membrane oxygenation failed to wean from cardiopulmonary bypass

BACKGROUND

Hemostatic complications and the need for large amounts of blood products are major obstacles during veno-arterial extracorporeal membrane oxygenation (VA-ECMO). Additionally, the occurrence of coagulopathy after cardiopulmonary bypass (CPB) affects systemic heparinization in pediatric post-cardiotomy patients. This study compares hemostatic complications in pediatric post-cardiotomy VA-ECMO patients for failure to wean from CPB with those who received post-cardiotomy VA-ECMO for other indications, while also exploring the relationship between different stages-hemostatic complications and the timing of systemic heparinization.

METHODS

We retrospectively analyzed 146 pediatric patients who received post-cardiotomy VA-ECMO support (CPB-ECMO, n=96 vs. non-CPB-ECMO, n=50) from January 2005 to June 2020. Patients were divided into survivors (n=46) and non-survivors (n=50) according to in-hospital mortality in the CPB-ECMO group. We compared clinical outcomes between the groups, then examined the associations between the timing of systemic heparinization after ECMO implantation and different stages-hemostatic complications, in the CPB-ECMO group.

RESULTS

We found that the risk of early bleeding was significantly increased in patients who failed to wean from CPB. The presence of early bleeding was accompanied by the higher demand for blood products transfusion in the CPB-ECMO group, and for treatment the patients received a longer delayed continuous heparin infusion. As a result of using delayed systemic heparinization to avoid early bleeding, early hemolysis increased in the CPB-ECMO group. A delayed systemic heparinization of 9.5 hours showed the best Youden index results and the overall greatest accuracy in predicting early hemolysis.

CONCLUSIONS

A direct transition from CPB to ECMO in pediatric post-cardiotomy patients significantly increases early bleeding. Delayed systemic heparinization to reduce early bleeding has good discrimination for predicting early hemolysis in the CPB-ECMO group. Coagulopathy is complex in pediatric post-cardiotomy VA-ECMO patients who failed to wean from CPB, and, as such, it is extremely important to monitor coagulation-related indicators in multiple dimensions to determine the timing of systemic heparinization.

Management of Anticoagulation during Extracorporeal Membrane Oxygenation in Children

Extracorporeal Membrane Oxygenation (ECMO) is often used in critically ill children with severe cardiopulmonary failure. Worldwide, about 3600 children are supported by ECMO each year, with an increase of 10% in cases per year. Although anticoagulation is necessary to prevent circuit thrombosis during ECMO support, bleeding and thrombosis are associated with significantly increased mortality risk. In addition, maintaining balanced hemostasis is a challenging task during ECMO support. While heparin is a standard anticoagulation therapy in ECMO, recently, newer anticoagulant agents are also in use. Currently, there is a wide variation in anticoagulation management and diagnostic monitoring in children receiving ECMO. This review intends to describe the pathophysiology of coagulation during ECMO support, review of literature on current and newer anticoagulant agents, and outline various diagnostic tests used for anticoagulation monitoring. We will also discuss knowledge gaps and future areas of research.

Activated clotting time in inpatient diagnostic and interventional settings

Monitoring for the anticoagulant effect of unfractionated (UFH) at the point of care using activated clotting time in real time is vital where risk of thrombosis is high. Although monitoring UFH effect is a routine and important task, changing from one ACT instrument type or technology to another must be preceded by a clinical and statistical evaluation to determine the suitability and repeatability and establish normal and treatable ranges of this newer instrument. In this multi-center prospective evaluation we tested 1236 paired ACT+ samples, and 463 paired ACT-LR samples (1699 total) from enrolled study subjects. Clinical settings included CVOR cardiopulmonary bypass, at the beside in extracorporeal life support (ELS), the Cardiac Catheterization Lab (CCL) during diagnostic studies and percutaneous coronary interventions (PCI), interventional radiology procedures and EP interventions. This study found more consistent clinical performance from the GEM Hemochron 100 as compared to the current clinical model, the Hemochron Signature Elite. The bias of GEM Hemochron 100 for ACT+ and ACT-LR was greatest in the setting of the CVOR where ACT levels were high. ACT-LR measurements by the GEM Hemochron 100 were comparable to the SE when performed in settings of CCL, ECM, EP and ICU. Results obtained for both ACT-LR and ACT+ in all clinical settings in this study using the GEM Hemochron 100 are as accurate and more repeatable as those with the current clinically available Signature Elite.

Poor Reliability of Common Measures of Anticoagulation in Pediatric Extracorporeal Membrane Oxygenation

Anticoagulation management in pediatric extracorporeal membrane oxygenation (ECMO) is challenging with multiple laboratory measures utilized across institutions without consensus guidelines. These include partial thromboplastin time (PTT), thromboelastography (TEG), and antifactor Xa (aXa). We aimed to evaluate the consistency of TEG R-time, PTT, and aXa correlation to bivalirudin and heparin dosing. We conducted a single-center restrospective review of pediatric ECMO cases from 2018 to 2020 anticoagulated with bivalirudin or heparin. We collected up to 14 serial simultaneous TEG R-time, PTT, and aXa measurements over a 7 day ECMO course with corresponding bivalirudin or heparin dosing. We analyzed the correlation between bivalirudin, heparin, and the three measurements of anticoagulation. A total of 67 ECMO runs, 32 bivalirudin, and 35 heparin, and more than 1,500 laboratory values, of which >80% simultaneous, were analyzed. When assessing correlations at the individual patient level, there was no consistent correlation between dosing and at least one laboratory parameter in the majority of patients. Furthermore, 44% of the bivalirudin cohort and 37% of the heparin cohort exhibited no correlation with any parameters. There were statistically significant correlations only between bivalirudin and heparin dosing and the sum total of the different laboratory tests. These inconsistencies highlight the importance of multimodality testing of anticoagulation in the management of pediatric ECMO anticoagulation and cannot be relied on in isolation from bedside clinical judgment.

Antithrombin Dose Optimization in Extracorporeal Membrane Oxygenation in Infants

Anticoagulation in extracorporeal membrane oxygenation (ECMO) is challenging, with significant morbidity and mortality associated with thrombotic complications. Unfractionated heparin (UFH) is commonly used, which depends on native antithrombin (AT) function to exert anticoagulant effects. Antithrombin deficiency is common in infants on ECMO and replacement with AT concentrate may be warranted. However, dosing recommendations in this population are limited. We conducted a retrospective review of patients <1 year of age who received recombinant AT (ATryn) while on UFH and ECMO between January 1, 2010 and December 31, 2017. Commonly used dosing equations were assessed to determine their ability to predict postdose AT levels. Patient AT levels were compared with equation-predicted postdose AT levels to determine a correlation. A total of 102 doses in 41 patients were used for analysis. Baseline mean AT level was 43% (±13%) and mean AT doses were 134 units (±58.1 units) or 40.5 units/kg (±18.7 units/kg). Median increase in the AT level was 8% (interquartile range 2-17%) with a mean postdose level of 52.6% (±14.2%). Weight-based dosing poorly correlated with postdose AT levels (r2 = 0.082). Postdose levels were best predicted when using an equation that included desired change in the AT level from baseline, the patient's weight, and added weight from the volume of the ECMO circuit (r2 = 0.427). Prospective studies are needed to evaluate optimal dosing strategies, safety, and efficacy of AT in this population.

Bivalirudin May Reduce the Need for Red Blood Cell Transfusion in Pediatric Cardiac Patients on Extracorporeal Membrane Oxygenation

We retrospectively compared anticoagulation with heparin and bivalirudin for 32 consecutive children under 18 years old during extracorporeal membrane oxygenation (ECMO) in our pediatric cardiac intensive care unit (PCICU). Between September 2015 and January 2018, 14 patients received heparin, 13 venoarterial (VA), and 1 venovenous (VV). From February 2018 to September 2019, 18 received bivalirudin (all VA). The mean (standard deviation [SD]) percentage of time with therapeutic activated partial thromboplastin time and activated clotting time was bivalirudin 54 (14%) and heparin 57 (11%), p = 0.4647, and percentage of time supratherapeutic was bivalirudin 18 (10%) and heparin 27 (12%), p = 0.0238. Phlebotomy-associated blood loss per hour of ECMO was double in the heparin compared with bivalirudin group 1.08 ml/h (0.20 ml/h), compared with 0.51 ml/h (0.07 ml/h), p = 0.0003, as well as interventions to control bleeding. Packed red blood cell (PRBC) transfusions significantly correlated with higher blood loss in the heparin group (Pearson correlation coefficient = 0.49, p = 0.0047). Overall amount of blood product utilization was not different between the groups. Survival to ECMO decannulation was 89% for bivalirudin and 57% for heparin, p = 0.0396, although 6 month survival was not significantly different (67% versus 57%, p = 0.5809). Heparin may increase the need for PRBC transfusions and strategies to attenuate bleeding when compared with bivalirudin for children receiving ECMO in PCICU.

Bivalirudin and Alteplase for Pulmonary Embolism Requiring Veno-Arterial Extracorporeal Membrane Oxygenation in an Adolescent

Saddle pulmonary embolism (PE) remains a challenge to diagnose and manage in pediatric patients. Current literature encourages early consideration of veno-arterial extracorporeal membrane oxygenation (VA-ECMO) in high-risk PE patients with impending right ventricular failure. We present a 17-year-old patient who was admitted to a pediatric cardiac intensive care unit with saddle PE requiring emergent VA-ECMO support because of cardiovascular collapse. Despite anticoagulation with bivalirudin and receiving systemic thrombolysis with alteplase, the clot burden was persistent with minimal improvement in right ventricular function. We proceeded to catheter thrombolysis while on VA-ECMO. This ultimately led to a successful resolution of the PE and allowed for weaning off VA-ECMO. PE is rare in children compared with adults, and pediatricians may be unaware of therapies becoming increasingly used in adults such as the use of VA-ECMO, with systemic and local thrombolysis. The concurrent use of a direct thrombin inhibitor for ECMO anticoagulation alongside the thrombolysis is a novel combination in this condition and age-group.

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.

Bleeding and Thrombosis With Pediatric Extracorporeal Life Support: A Roadmap for Management, Research, and the Future From the Pediatric Cardiac Intensive Care Society: Part 2

OBJECTIVES

To make recommendations on improving understanding of bleeding and thrombosis with pediatric extracorporeal life support including future research directions.

DATA SOURCES

Evaluation of literature and consensus conferences of pediatric critical care and extracorporeal life support experts.

STUDY SELECTION

A team of 10 experts with pediatric cardiac and extracorporeal membrane oxygenation experience and expertise met through the Pediatric Cardiac Intensive Care Society to review current knowledge and make recommendations for future research to establish "best practice" for anticoagulation management related to extracorporeal life support.

DATA EXTRACTION/DATA SYNTHESIS

This white paper focuses on clinical understanding and limitations of current strategies to monitor anticoagulation. For each test of anticoagulation, limitations of current knowledge are addressed and future research directions suggested.

CONCLUSIONS

No consensus on best practice for anticoagulation monitoring exists. Structured scientific evaluation to answer questions regarding anticoagulation monitoring and bleeding and thrombotic events should occur in multicenter studies using standardized approaches and well-defined endpoints. Outcomes related to need for component change, blood product administration, healthcare outcome, and economic assessment should be incorporated into studies. All centers should report data on patient receiving extracorporeal life support to a registry.