Activation of the clotting system during extracorporeal membrane oxygenation in term newborn infants

Effect of Unfractionated Heparin Dose on Complement Activation and Selected Extracellular Vesicle Populations during Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) provides critical support for patients with severe cardiopulmonary dysfunction. Unfractionated heparin (UFH) is used for anticoagulation to maintain circuit patency and avoid thrombotic complications, but it increases the risk of bleeding. Extracellular vesicles (EVs), nano-sized subcellular spheres with potential pro-coagulant properties, are released during cellular stress and may serve as potential targets for monitoring anticoagulation, particularly in thromboinflammation. We investigated the impact of UFH dose during ECMO therapy at the coagulation-inflammation interface level, focusing on complement activation and changes in circulating large EV (lEV) subsets. In a post hoc analysis of a multicenter randomized controlled trial comparing two anticoagulation management algorithms, we examined lEV levels and complement activation in 23 veno-venous-ECMO patients stratified by UFH dose. Blood samples were collected at different time points and grouped into three phases of ECMO therapy: initiation (day 1), mid (days 3-4), and late (days 6-7). Immunoassays detected complement activation, and flow cytometry analyzed lEV populations with an emphasis on mitochondria-carrying subsets. Patients receiving <15 IU/kg/h UFH exhibited higher levels of the complement activation product C5a and soluble terminal complement complex (sC5b-9). Lower UFH doses were linked to increased endothelial-derived lEVs, while higher doses were associated with elevated RBC-derived and mitochondria-positive lEVs. Our findings suggest the potential theranostic relevance of EV detection at the coagulation-inflammation interface. Further research is needed to standardize EV detection methods and validate these findings in larger ECMO patient cohorts.

Circuit change in neonatal and pediatric extracorporeal membrane oxygenation is associated with adverse outcomes

INTRODUCTION

Extracorporeal membrane oxygenation (ECMO) circuits may be changed during the run for multiple reasons; however, these circuit changes may be associated with adverse events. Predictors for undergoing a circuit change (CC) and their outcomes remain unclear. We hypothesized that neonatal and pediatric CC correlates with increased morbidity and mortality.

METHODS

Pediatric and neonatal patients who underwent one ECMO run lasting <30 days at a tertiary children's hospital from 2011 through 2017 were retrospectively reviewed. Bivariate regression analysis evaluated factors associated with ECMO mortality and morbidity. LASSO logistic regression models identified independent risk factors for undergoing a CC. p < .05 was significant.

RESULTS

One hundred 85 patients were included; 137 (74%) underwent no CC, while 48 (26%) underwent one or more. Undergoing a CC was associated with longer ECMO duration (p < .001), higher blood transfusion volumes (p < .001), increased hemorrhagic complications (p < .001) and increased mortality (p = .002). Increased platelet (p = .001) and FFP (p = .016) transfusion volumes at any time while on ECMO were independent factors associated with undergoing a CC.

CONCLUSIONS

Changing the circuit during the ECMO run occurs frequently and may be associated with poorer outcomes. Understanding the outcomes and predictors for CC may guide management protocols for more efficient circuit changes given its important association with overall outcomes.

Epidemiology of anticoagulation for children supported by extracorporeal membrane oxygenation in the United States: A Pediatric Hospital Information System database study

INTRODUCTION

Due to the risk of thrombosis, nearly all children supported by extracorporeal membrane oxygenation (ECMO) receive systemic anticoagulation. While heparin has traditionally been used, there are reports of increased use of direct thrombin inhibitors. We sought to describe the use of anticoagulation in children supported by ECMO in the United States using a large administrative database.

METHODS

We performed a retrospective cohort study of children supported by ECMO within the Pediatric Health Information System (PHIS) database. Pediatric encounters involving ECMO from 2012 to 2020 were identified. Data regarding demographics, diagnoses, anticoagulation, complications, and outcomes were extracted for eligible encounters.

RESULTS

Eleven thousand five hundred ninety-five encounters that involved ECMO were identified. Fifty-four percent were male with an age range of 0-17 years and a median (IQR) age of 0 (0-2) years. Unfractionated heparin (UFH) only was used in 94% (95% CI: 93.6-94.5%) of encounters and UFH followed by bivalirudin in 5% (95% CI: 4.3-5.1%) of cases. There was a significant difference in the use of bivalirudin from 2012 to 2020 (p < 0.001). Differences in anticoagulation regimens were observed between infants and children (p = 0.004) and between those with and without cardiac indications for ECMO (p < 0.001). Four percent (95% CI: 4.1-4.8%) of encounters were associated with diagnostic coding for thrombosis and differences in occurrence of thrombosis were observed between different anticoagulant regimens (p < 0.001).

CONCLUSIONS

Though the majority of children on ECMO in the United States receive heparin anticoagulation, there is an increase in use of direct thrombin inhibitors. Prospective studies must evaluate the efficacy of different anticoagulants in this patient population.

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.

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.

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.

Platelet, Red Cell, and Endothelial Activation and Injury During Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) can be lifesaving but suffers from high rates of bleeding and repeated transfusions. Current monitoring of blood cell damage during ECMO is limited to platelet counts, hematocrit, and plasma hemoglobin levels. Extracelluar vesicles (EV) are small cell fragments released when cells are activated/injured. The objective was to evaluate flow cytometric measurements of EV during ECMO as an indication of platelet, red cell, and endothelial activation/injury. Samples were collected from 55 patients (1 day to 19 years) during 58 ECMO runs. ECMO activated or injured blood cells, but the extent was highly variable and patient dependent. On average platelet activation was increased sevenfold during ECMO with up to 60-fold increased activation during the first 24 hours in some patients. EV associated with platelet and red-cell injury were increased eightfold on average but up to 200-fold in patients with disseminated intravascular coagulation, severe hemolysis, or massive transfusion. Approximately 9% of ECMO patients showed a red-cell and endothelial activation pattern that was associated with poor prognosis. Extracellular vesicles with autofluorescence similar to bilirubin appeared to come from monocytes processing hemoglobin. ECMO is associated with a highly variable, sustained increase in platelet, red-cell, and endothelial activation and injury that is a combination of circuit and transfusion related events, the patients underlying condition and possibly genetic influences on blood cell activation and injury. Extracellular vesicle measurements may improve our understanding of cellular activation and injury during ECMO as we work to improve the biocompatibility of these systems.

Anticoagulation in Critically Ill Adults during Extracorporeal Circulation

Extracorporeal circuits including renal replacement therapy, extracorporeal membrane oxygenation, and ventricular assist devices are increasingly used in critically ill patients. The need for anticoagulation to provide circuit patency and avoid thrombosis remains a challenging task for treating physicians. In the presence of overall low scientific evidence concerning the optimal anticoagulants, monitoring tests, and therapeutic target ranges, recommendations are largely expert opinions and most centers use individual "in-house" anticoagulation protocols. This review gives a practical view on current concepts of anticoagulation strategies in patients with extracorporeal assist devices.

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.

Impact of CRRT in Patients with PARDS Treated with VV-ECMO

The high mortality of pediatric acute respiratory distress syndrome (PARDS) is partly related to fluid overload. Extracorporeal membrane oxygenation (ECMO) is used to treat pediatric patients with severe PARDS, but can result in acute kidney injury (AKI) and worsening fluid overload. The objective of this study was to determine whether the addition of CRRT to ECMO in patients with PARDS is associated with increased mortality. Methods: We conducted a retrospective 7-year study of patients with PARDS requiring ECMO and divided them into those requiring CRRT and those not requiring CRRT. We calculated severity of illness scores, the amount of blood products administered to both groups, and determined the impact of CRRT on mortality and morbidity. Results: We found no significant difference in severity of illness scores except the vasoactive inotropic score (VIS, 45 ± 71 vs. 139 ± 251, p = 0.042), which was significantly elevated during the initiation and the first three days of ECMO. CRRT was associated with an increase in the use of blood products and noradrenaline (p < 0.01) without changing ECMO duration, length of PICU stay or mortality. Conclusion: The addition of CRRT to ECMO is associated with a greater consumption of blood products but no increase in mortality.

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.

Extracorporeal Membrane Oxygenation for Respiratory Failure

This review focuses on the use of veno-venous extracorporeal membrane oxygenation for respiratory failure across all blood flow ranges. Starting with a short overview of historical development, aspects of the physiology of gas exchange (i.e., oxygenation and decarboxylation) during extracorporeal circulation are discussed. The mechanisms of phenomena such as recirculation and shunt playing an important role in daily clinical practice are explained.Treatment of refractory and symptomatic hypoxemic respiratory failure (e.g., acute respiratory distress syndrome [ARDS]) currently represents the main indication for high-flow veno-venous-extracorporeal membrane oxygenation. On the other hand, lower-flow extracorporeal carbon dioxide removal might potentially help to avoid or attenuate ventilator-induced lung injury by allowing reduction of the energy load (i.e., driving pressure, mechanical power) transmitted to the lungs during mechanical ventilation or spontaneous ventilation. In the latter context, extracorporeal carbon dioxide removal plays an emerging role in the treatment of chronic obstructive pulmonary disease patients during acute exacerbations. Both applications of extracorporeal lung support raise important ethical considerations, such as likelihood of ultimate futility and end-of-life decision-making. The review concludes with a brief overview of potential technical developments and persistent challenges.

Exogenous supplementation of antithrombin III in adult and pediatric patients receiving extracorporeal membrane oxygenation

Background:

Antithrombin III deficiency can occur with heparin anticoagulation during extracorporeal membrane oxygenation leading to heparin resistance. Antithrombin III supplementation has been shown to improve anticoagulation; however, there is no consensus on appropriate administration. We described the effect of antithrombin III supplementation on coagulation parameters in adult and pediatric extracorporeal membrane oxygenation patients.

Methods:

We conducted a retrospective cohort study using electronic medical records of patients who received ⩾1 dose of antithrombin III during extracorporeal membrane oxygenation while on continuous heparin. Endpoints included the change in anti-Xa levels and antithrombin III activity at −6 versus 6 h relative to antithrombin III supplementation, and heparin infusion rates at 6 versus 12 h after antithrombin III supplementation.

Results:

Eighteen patients receiving 36 antithrombin III administrations were analyzed. Mean (standard deviation) anti-Xa values at −6 versus 6 h were 0.15 (0.07) versus 0.24 (0.15) IU/mL ( p-value: 0.250) for pediatrics and 0.19 (0.22) versus 0.31 (0.27) IU/mL ( p-value: 0.052) for adults. Mean (standard deviation) plasma antithrombin III activity at the same intervals were 32% (14.2%) versus 66.8% (25.1%; p-value: 0.062) for pediatrics and 30.3% (14%) versus 52.8% (8.1%; p-value: 0.094) for adults. Mean (standard deviation) heparin rates at 6 versus 12 h after antithrombin III for pediatrics were 23.6 (6) versus 23.5 (6.5) units/kg/h ( p-value: 0.728), and 15.3 (6.6) versus 13.5 (8) units/kg/h ( p-value: 0.188) for adults.

Conclusion:

Administration of antithrombin III improved anti-Xa levels in both populations, however, did not significantly reduce heparin rates. Our findings suggest that the use of antithrombin III restores heparin responsiveness in patients with low antithrombin III activity and low anti-Xa activity.

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.

Impact of an inline extracorporeal membrane oxygenation hemofilter system in neonatal acute kidney injury

Extracorporeal membrane oxygenation (ECMO) is considered a recognized lifesaving support for patients with cardiorespiratory failure. Acute kidney injury (AKI) and fluid overload are significant morbidity factors resulting in serious complications. The inline hemofilter system (IHS) and the continuous renal replacement therapy (CRRT) machine are different methods of renal replacement therapy for patients with ECMO. IHS is the alternate, safe dialysis modality of choice because it is user-friendly, inexpensive, and efficiently removes fluid overload and renal diffusive clearance. We report on a 20-day-old male neonate with multiple congenital cardiac defects who needed venoarterial ECMO and had AKI necessitating renal replacement therapy using IHS. The patient had stable electrolyte parameters, good ultrafiltration, and efficient diffusive clearance. He was decannulated from ECMO therapy after 9 days without any related complications. Therefore, neonatal IHS is a safe and efficient alternative approach to AKI.

Activation of the Clotting System: Heparin-Coated versus Non Coated Systems for Extracorporeal Circulation

The purpose of this experimental study was to compare heparin-coated versus non-coated systems for extracorporeal membrane oxygenation (ECMO), to investigate the dynamic course of clotting activation in both groups.

Methods.

Eight pigs weighing 19.7 (± 1.3) kg, each underwent ECMO for 24 hours. Two groups were formed: in group 1, heparin-coated circuits were used with low dose heparinization (10 IU/kg/hr), whereas in group 2 non-coated circuits with high dose heparinization (60 IU/kg/hr) were used. Coagulation was monitored by measuring prothrombin time, partial thromboplastin time, fibrinogen, antithrombin III (AT III) and specific markers of clotting activation (thrombin-antithrombin III complexes (TAT) and D-dimer). Furthermore, platelet count, hematocrit, activated clotting time (ACT), and plasma heparin concentration were determined regularly.

Results.

The dynamic course of the specific coagulation activation markers showed some differences: whereas TAT and D-dimer increased quickly in group 2, the increase in group 1 was delayed. Activation marker values tended to be lower in group 1 during the first six hours, after which no more differences between the groups were seen. After 24 hours of ECMO, TAT and D-dimer had nearly returned to baseline values. Platelets showed a continuous decrease throughout the experiment, which was very similar in both groups.

Conclusions.

The heparin coated system showed a distinct delay in clotting activation during the first six hours of ECMO. After six hours there were no more differences between the groups.

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.

Thromboelastography-based anticoagulation management during extracorporeal membrane oxygenation: a safety and feasibility pilot study

Background

There is no consensus on the management of anticoagulation during extracorporeal membrane oxygenation (ECMO). ECMO is currently burdened by a high rate of hemostatic complications, possibly associated with inadequate monitoring of heparin anticoagulation. This study aims to assess the safety and feasibility of an anticoagulation protocol for patients undergoing ECMO based on thromboelastography (TEG) as opposed to an activated partial thromboplastin time (aPTT)-based protocol.

Methods

We performed a multicenter, randomized, controlled trial in two academic tertiary care centers. Adult patients with acute respiratory failure treated with veno-venous ECMO were randomized to manage heparin anticoagulation using a TEG-based protocol (target 16–24 min of the R parameter, TEG group) or a standard of care aPTT-based protocol (target 1.5–2 of aPTT ratio, aPTT group). Primary outcomes were safety and feasibility of the study protocol.

Results

Forty-two patients were enrolled: 21 were randomized to the TEG group and 21 to the aPTT group. Duration of ECMO was similar in the two groups (9 (7–16) days in the TEG group and 11 (4–17) days in the aPTT group, p = 0.74). Heparin dosing was lower in the TEG group compared to the aPTT group (11.7 (9.5–15.3) IU/kg/h vs. 15.7 (10.9–21.3) IU/kg/h, respectively, p = 0.03). Safety parameters, assessed as number of hemorrhagic or thrombotic events and transfusions given, were not different between the two study groups. As for the feasibility, the TEG-based protocol triggered heparin infusion rate adjustments more frequently (p < 0.01) and results were less frequently in the target range compared to the aPTT-based protocol (p < 0.001). Number of prescribed TEG or aPTT controls (according to study groups) and protocol violations were not different between the study groups.

Conclusions

TEG seems to be safely used to guide anticoagulation management during ECMO. Its use was associated with the administration of lower heparin doses compared to a standard of care aPTT-based protocol.

Trial registration ClinicalTrials.gov, October 22,2014. Identifier: NCT02271126.

Electronic supplementary material

The online version of this article (10.1186/s13613-017-0352-8) contains supplementary material, which is available to authorized users.

Neonatal Extracorporeal Membrane Oxygenation Due to Respiratory Failure: A Single Center Experience Over 28 Years

Background: ECMO therapy is worldwide declining in the neonatal population; hence, its therapeutic value is sometimes questioned. Objectives: To report our experience with neonatal ECMO due to respiratory failure over a 28 year time period. Methods: Retrospective single center observational study including all neonates admitted to ECMO due to respiratory failure between 1989 and 2016 at Graz, Austria. Data were collected regarding survival rate, duration of ECMO, complications, length of hospital stay, changes over time, and follow-up. Results: Sixty-seven neonates were admitted and 43 (64%) needed ECMO-median birth weight 3390 grams (range 1810-4150) and gestational age 39 weeks (32-43). Survival rate was 65% (28/43); with higher rates in meconium aspiration syndrome (MAS) 89% vs. congenital diaphragmatic hernia (CDH) 46% and septic shock 44% (p = 0.005 and p = 0.006, respectively). ECMO duration was median 5 days (1-30) and veno-arterial ECMO (52%) dominated. Need for ECMO therapy decreased over time (p < 0.001). Complications occurred in 31 (72%) neonates. Five neonates had cerebral hemorrhages (11.4%) and four had cerebral infarction (9.1%). Of 26 survivors 17 (65%) showed normal neurodevelopmental outcome at median follow-up of 73 months. Motor deficits were present in one case, cognitive deficits in 9 (35%). Median length of hospital stay was 78 days in those with deficits and 29 in those with normal neurodevelopmental outcome (p < 0.001). Conclusions: Survival rate did not change over the study time but indications for ECMO did. Cognitive impairment was the major long-term deficit following neonatal ECMO being associated with longer hospital stay.

Anticoagulation Therapy during Extracorporeal Membrane Oxygenator Support in Pediatric Patients

Extracorporeal membrane oxygenation (ECMO) is a salvage therapy for critically ill patients. Although ECMO is becoming more common, hemorrhagic and thromboembolic complications remain the major causes of death in patients undergoing ECMO treatments. These complications commence upon blood contact with artificial surfaces of the circuit, blood pump, and oxygenator system. Therefore, anticoagulation therapy is required in most cases to prevent these problems. Anticoagulation is more complicated in pediatric patients than in adults, and the foreign surface of ECMO only increases the complexity of systemic anticoagulation. In this review, we discuss the pathophysiology of coagulation, anticoagulants, and monitoring tools in pediatric patients receiving ECMO.

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.

Laboratory and clinical predictors of 30-day survival for patients on Extracorporeal Membrane Oxygenation (ECMO): 8-Year experience at Albert Einstein College of Medicine, Montefiore Medical Center

PURPOSE

Survival of patients on ECMO has remained stable in every population. Laboratory values predictors of survival are required to improve patient care.

MATERIALS AND METHODS

Clinical Looking Glass software was used to assess Electronic Medical Records (EMRs) of patients at Albert Einstein College of Medicine, Montefiore Medical Center (2007-2014).

RESULTS

Our population comprises of 166 adults and was divided in survivors and non-survivors, within 30days. Indications for ECMO were cardiac (65%), respiratory (25%) and infectious diseases (<10%). Eighty six patients (51.8%) survived the procedure. Gender, body weight, ejection fraction, diastolic blood pressure, and socio-economic status did not differ among survivors and non-survivors. In contrast, younger patients (45yo vs 55yo, p=0.0001) and higher systolic blood pressure (115mmHg vs 103mmHg, p=0.025) have favorable outcome. Univariate analysis shows that pre-cannulation values for creatinine (p=0.0003), chloride (p=0.009), bicarbonate (p=0.015) and pH (p=0.03) have prognostic value. Post-cannulation aPTT, pH, platelet and lymphocyte counts also have discriminative power. Notably, multiple logistic regressions for Multivariate Analysis identified chloride (OR 1.07; 95% CI 1.02-1.13; p=0.004), pH (OR 3.35; 95% CI 1.89-5.9; p<0.0001) and aPTT (OR 0.98; 95% CI 0.976-0.998; p=0.024) as independent risk factors for 30-day mortality. These results imply that pre-existing renal conditions and hemostatic dysregulation contribute to poor outcome. Finally, patients on VV-ECMO have increase odds of survival (OR 1.88; 95% CI 1.06-3.34; p=0.029).

CONCLUSIONS

Laboratory markers identified herein may guide the management of patients on ECMO.

Evaluation of a pharmacy managed heparin protocol for extracorporeal membrane oxygenation patients

INTRODUCTION

Unfractionated heparin is the preferred anticoagulant in extracorporeal membrane oxygenation (ECMO) patients. However, there is a lack of consensus on its titration and monitoring. The objective of this study was to describe the efficacy and safety of a pharmacy managed heparin protocol utilizing activated partial thromboplastin time (aPTT) in comparison to our standard physician-managed activated clotting time (ACT)-based anticoagulation in ECMO patients.

METHODS

Patients administered a heparin drip while on ECMO were included in the study. The primary endpoints were the incidence of hemorrhagic and thrombotic complications.

RESULTS

A total of 122 adult patients were identified who were on ECMO with heparin anticoagulation; sixty-one patients were managed with each of the physician-managed ACT and pharmacy managed aPTT protocols. No statistically significant difference was observed between the physician ACT and the pharmacy aPTT groups in overall hemorrhagic (69% vs 80%, p=0.145) or thrombotic complications (41% vs 39%, p=0.853).

CONCLUSION

There was a similar rate of thrombotic and bleeding events between the two study groups. A pharmacy managed heparin protocol utilizing aPTT monitoring appears to be a safe and effective method of providing anticoagulation in adult ECMO patients.

Current Limitations of the Assessment of Haemostasis in Adult Extracorporeal Membrane Oxygenation Patients and the Role of Point-of-Care Testing

Haemostatic perturbations are commonly seen in extracorporeal membrane oxygenation (ECMO) patients and remain a clinical challenge, contributing significantly to morbidity and mortality. The approach to anticoagulation monitoring and the management of bleeding varies considerably across ECMO centres. Routine laboratory tests have their limitations in terms of turnaround time and specificity of information provided. Newer point-of-care testing (POCT) for coagulation may overcome these issues, as it provides information about the entire coagulation pathway from clot initiation to lysis. It is also possible to obtain qualitative information on platelet function from these tests. Furthermore, the ability to incorporate these results into a goal-directed algorithm to manage bleeding with targeted transfusion strategies appears particularly attractive and cost effective. Further studies are required to evaluate the utility of POCT to optimise bleeding and anticoagulation management in these complex patients.

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.

Use and Future Investigations of Recombinant and Plasma-Derived Coagulation and Anticoagulant Products in the Neonate

Although congenital bleeding disorders can manifest in the newborn period, the most common causes of bleeding and thrombosis in neonates are acquired conditions. Factor concentrates are used for specific diagnoses (hemophilia with inhibitors, specific factor deficiency, von Willebrand disease) and approved indications, and increasingly for off-label indications (bleeding in surgery cardiopulmonary bypass, extracorporeal membrane oxygenation). We will review the approved indications for factor products in the neonate and discuss the evidence and rationale for off-label use of factor products in management of bleeding and thrombosis in the neonate.

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.

The Impact of Renal Failure and Renal Replacement Therapy on Outcome During Extracorporeal Membrane Oxygenation Therapy

Acute kidney injury (AKI) is common in patients treated with veno-arterial (VA-) or veno-venous (VV-) extracorporeal membrane oxygenation (ECMO). In this setting, the use of continuous renal replacement therapy (CRRT) can help to optimize fluid status but may also negatively impact on patients' outcome. In contrast, the relationship between AKI, CRRT, and survival in critically ill adult patients receiving ECMO is not well defined. The institutional ECMO database (n = 162) from November 2008 to December 2013, excluding patients with ICU survival <24 hours was reviewed. Demographics, co-morbidities, and concomitant therapies for all patients were collected. AKI was defined according to the Acute Kidney Injury Network (AKIN) criteria. ICU mortality was noted. Data were retrieved for 135 patients (79 with VA-ECMO and 56 with VV-ECMO). Of these, 95 developed AKI, 63 (47%) of whom required CRRT; thus three groups of patients were identified: (a) no AKI; (b) AKI without CRRT (AKINOCRRT ); and (c) CRRT with AKI (AKICRRT ). AKINOCCRT patients were more likely to have preexisting heart disease, to be more severely ill, and to be treated with VA-ECMO than those without AKI. AKICRRT patients were also more likely to be treated with VA-ECMO, had more organ dysfunction at the time of ECMO insertion, and needed more transfusions and inotropic agents than patients without AKI. ICU mortality was 53% (72/135) and was similar in the three groups, even when different AKI stages or VA/VV-ECMO were analyzed separately. In this study, the use of CRRT was not associated with an increased mortality in an adult population of patients treated with ECMO, even after adjustment for confounders.

Anticoagulation Management and Monitoring during Pediatric Extracorporeal Life Support: A Review of Current Issues

Anticoagulation is an imperfect science and is even more complicated in neonates and young children. The addition of the extracorporeal life support (ECLS) foreign circuit adds an additional layer of complexity. Anticoagulation goals during ECLS are to maintain a clot-free circuit and a hemostatically balanced patient. Unfractionated heparin (UFH) is the default gold standard anticoagulant as no large studies have been performed on any other anticoagulants. This review will focus on the advantages and disadvantages of the various methods to monitor UFH anticoagulation, discuss alternative anticoagulants, and examine bleeding and thrombotic complications during ECLS.

Antithrombotic therapy for ventricular assist devices in children: do we really know what to do?

The use of ventricular assist devices (VADs) in children is increasing. Stroke and device-related thromboembolism remain the most feared complications associated with VAD therapy in children. The presence of a VAD causes dysregulation of hemostasis due to the presence of foreign materials and sheer forces intrinsic to the device resulting in hypercoagulability and potentially life-threatening thrombosis. The use of antithrombotic therapy in adults with VADs modulates this disruption in hemostasis, decreasing the risk of thrombosis. Yet, differences in hemostasis in children (developmental hemostasis) may result in variances in dysregulation by these devices and preclude the use of adult guidelines. Consequently, pediatric device studies must include safety and efficacy estimates of device-specific antithrombotic therapy guidelines. This review will discuss mechanisms of hemostatic dysregulation as it pertains to VADs, goals of VAD antithrombotic therapy for children and adults, and emerging antithrombotic strategies for VAD use in children.

Extracorporeal life support: the precarious balance of hemostasis

Extracorporeal life support is by far the most extraordinary and complex form of extracorporeal technology used in the practice of critical care medicine. It is used to support critically ill patient who suffer acute respiratory or cardiac failure unresponsive to conventional support. As extracorporeal technologies have refined the pathophysiologic reaction that occurs at the blood/biomaterial interface has not been conquered; a new set of physiologic responses/derangements occur with the patient's exposure to the artificial circuit. Without this support mortality is near certain and with support if management is not precise and judicious the complications can be catastrophic. The management of a patient on ECLS is the same as for any critically ill patient with the added need for anticoagulation to maintain patency of the extracorporeal circuit without causing bleeding within the patient and thrombosis within the circuitry or the patient. This is the precarious balance of hemostasis during ECLS.

Antithrombin concentrate in pediatric patients requiring unfractionated heparin anticoagulation: a retrospective cohort study

OBJECTIVE

To describe antithrombin levels, altered unfractionated heparin effect (anti-factor Xa activity and activated partial thromboplastin time), and adverse effects post administration of a single high dose of antithrombin concentrate.

DESIGN

Retrospective review.

PATIENTS

Infants and children with antithrombin levels less than 50% and a subtherapeutic unfractionated heparin effect.

SETTING

Quaternary care children's hospital with a dedicated anticoagulation program.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A single high dose of antithrombin concentrate was administered. Antithrombin level, anti-factor Xa, and activated partial thromboplastin times were measured post antithrombin concentrate infusion and daily until stable. One hundred twenty-one patients received 246 doses of antithrombin. Patients were described using two cohorts based on the ability to obtain exact heparin doses. Cohort 1 included all patients between January 2004 and May 2008 when complete heparin dosing was unavailable. Cohort 2 included patients from May 2008 to May 2011 when heparin dose was available. Median age and weight were 3.7 months and 4.1 kg. Mean antithrombin concentrate dose was 222 IU/kg. Mean antithrombin level increased from 0.39 to 1.20 U/mL following antithrombin concentrate administration. In cohort 2, unfractionated heparin doses to achieve a target anti-factor Xa activity pre-post antithrombin concentrate were 28 and 19 U/kg/hr, respectively, for children 12 months old or younger and 25 and 19 U/kg/hr, respectively, for children older than 12 months. There were no hemorrhagic, thrombotic, or allergic events within 1 week of antithrombin concentrate administration.

CONCLUSIONS

This is the largest study of antithrombin concentrate evaluation in children. Administration of antithrombin concentrate increases anti-factor Xa activity with lower administered unfractionated heparin doses.

Age-based difference in activation markers of coagulation and fibrinolysis in extracorporeal membrane oxygenation

OBJECTIVE

Coagulation system activation in extracorporeal membrane oxygenation results in hemostatic derangements. Thrombin generation markers like prothrombin fragment 1+2 and thrombin-antithrombin complex are sensitive markers of hypercoagulability. Plasmin-antiplasmin complex is a sensitive marker for fibrinolysis. D-dimers reflect thrombin generation and fibrinolysis. The aim was to identify the extent of hemostasis activation during extracorporeal membrane oxygenation by measuring thrombin-antithrombin complex, prothrombin fragment 1+2, plasmin-antiplasmin complex, and D-dimer.

DESIGN

Prospective cohort study.

SETTING

Tertiary care academic center.

PATIENTS

Children placed on extracorporeal membrane oxygenation from April 2011 to January 2013.

INTERVENTIONS

Prothrombin fragment 1+2, thrombin-antithrombin complex, plasmin-antiplasmin complex, and D-dimer were measured on days 1 and 5 of extracorporeal membrane oxygenation.

MEASUREMENTS AND MAIN RESULTS

Data presented as median (interquartile range); nonparametric tests were done using SPSS. Twenty-nine children (52% < 30 d old [neonates], median extracorporeal membrane oxygenation length 151 hr) were studied. Complications included thrombosis in 14%, bleeding in 45%, and thrombosis and bleeding together in 10%. Thrombin-antithrombin complex, prothrombin fragment 1+2, plasmin-antiplasmin complex, and D-dimer levels were high on day 1 and remained increased on extracorporeal membrane oxygenation. In neonates, all levels were higher on day 5 compared with day 1: thrombin-antithrombin complex (55.6 μg/L [30.7-76.0] vs 18.7 μg/L [10.9-34.6]; p = 0.03), prothrombin fragment 1+2 (2,038 pmol/L [1,093-4,018.5] vs 377.5 pmol/L [334.3-1,103.0]; p = 0.00), plasmin-antiplasmin complex (2,160 μg/L [786-3,090] vs 398 μg/L [296.8-990.8]; p = 0.00), and D-dimer (3.0 μg/mL [1.9-11.5] vs 1.5 μg/mL [0.6-2.9]; p = 0.01). Thrombin-antithrombin complex, prothrombin fragment 1+2, plasmin-antiplasmin complex, and D-dimer levels did not correlate with anti-Xa activity or heparin dose. In bleeders older than 30 days, plasmin-antiplasmin complex stayed elevated on day 5, but in patients with no bleeding complications, plasmin-antiplasmin level showed a declining trend. In neonates, plasmin-antiplasmin levels increased over the course of extracorporeal membrane oxygenation irrespective of bleeding.

CONCLUSION

Despite our best efforts at adequate anticoagulation with unfractionated heparin, neonates showed persistent increase in coagulation activation on extracorporeal membrane oxygenation. Fibrinolysis activation may contribute to bleeding in patients older than 30 days. Different anticoagulation protocols should be individualized based on age.

Unfractionated heparin activity measured by anti-factor Xa levels is associated with the need for extracorporeal membrane oxygenation circuit/membrane oxygenator change: a retrospective pediatric study

OBJECTIVE

Investigate whether anti-Factor Xa levels are associated with the need for change of circuit/membrane oxygenator secondary to thrombus formation in pediatric patients.

DESIGN AND SETTINGS

Retrospective single institution study.

PATIENTS

Retrospective record review of 62 pediatric patients supported with extracorporeal membrane oxygenation from 2009 to 2011.

INTERVENTIONS

Data on standard demographic characteristics, indications for extracorporeal membrane oxygenation, duration of extracorporeal membrane oxygenation, activated clotting time measurements, anti-Factor Xa measurements, and heparin infusion rate were collected. Generalized linear models were used to associate anti-Factor Xa concentrations and need for change of either entire circuit/membrane oxygenator secondary to thrombus formation.

MEASUREMENTS AND MAIN RESULTS

Sixty-two patients met study inclusion criteria. No-circuit change was required in 45 of 62 patients. Of 62 patients, 17 required change of circuit/membrane oxygenator due to thrombus formation. Multivariate analysis of daily anti-Factor Xa measurements throughout duration of extracorporeal membrane oxygenation support estimated a mean anti-Factor Xa concentration of 0.20 IU/mL (95% CI, 0.16, 0.24) in no-complete-circuit group that was significantly higher than the estimated concentration of 0.13 IU/mL (95% CI, 0.12, 0.14) in complete-circuit group (p = 0.001). A 0.01 IU/mL decrease in anti-Factor Xa increased odds of need for circuit/membrane oxygenator change by 5% (odds ratio = 1.105; 95% CI, 1.00, 1.10; p = 0.044). Based on the observed anti-Factor Xa concentrations, complete-circuit group had 41% increased odds for requiring circuit/membrane oxygenator change compared with no-complete-circuit group (odds ratio = 1.41; 95% CI, 1.01, 1.96; p = 0.044). Mean daily activated clotting time measurement (p = 0.192) was not different between groups, but mean daily heparin infusion rate (p < 0.001) was significantly different between the two groups.

CONCLUSIONS

Higher anti-Factor Xa concentrations were associated with freedom from circuit/membrane oxygenator change due to thrombus formation in pediatric patients during extracorporeal membrane oxygenation support. Activated clotting time measurements did not differ significantly between groups with or without circuit/membrane oxygenator change. This is the first study to link anti-Factor Xa concentrations with a clinically relevant measure of thrombosis in pediatric patients during extracorporeal membrane oxygenation support. Further prospective study is warranted.

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.