Extracorporeal Membrane Oxygenation Complications in Heparin- and Bivalirudin-Treated Patients

Heparin-induced thrombocytopenia in extracorporeal membrane oxygenation-supported patients: a systematic review and meta-analysis

BACKGROUND

In recent years, extracorporeal membrane oxygenation (ECMO) has been increasingly used in critically ill patients with respiratory or cardiac failure. Heparin is usually used as anticoagulation therapy during ECMO support. However, heparin-induced thrombocytopenia (HIT) in ECMO-supported patients, which results in considerable morbidity and mortality, has not yet been well described. This meta-analysis and systematic review aimed to thoroughly report the incidence of HIT on ECMO, as well as the characteristics and outcomes of HIT patients.

METHODS

We searched the PubMed, Embase, Cochrane Library, and Scopus databases for studies investigating HIT in adult patients supported by ECMO. All studies conforming to the inclusion criteria were screened from 1975 to August 2023. Nineteen studies from a total of 1,625 abstracts were selected. The primary outcomes were the incidence of HIT and suspected HIT.

RESULTS

The pooled incidence of HIT in ECMO-supported patients was 4.2% (95% CI: 2.7-5.6; 18 studies). A total of 15.9% (95% CI: 9.0-22.8; 12 studies) of patients on ECMO were suspected of having HIT. Enzyme-linked immunosorbent assay (ELISA) is the most commonly used immunoassay. The median optical density (OD) of the ELISA in HIT-confirmed patients ranged from 1.08 to 2.10. In most studies, the serotonin release assay (SRA) was performed as a HIT-confirming test. According to the subgroup analysis, the pooled incidence of HIT in ECMO patients was 2.7% in studies whose diagnostic mode was functional assays, which is significantly lower than the incidence in studies in which the patients were diagnosed by immunoassay (14.5%). Argatroban was most commonly used as an alternative anticoagulation agent after the withdrawal of heparin. Among confirmed HIT patients, 45.5% (95% CI: 28.8-62.6) experienced thrombotic events, while 50.1% (95% CI: 24.9-75.4) experienced bleeding events. Overall, 46.6% (95% CI: 30.4-63.1) of patients on ECMO with HIT died.

CONCLUSION

According to our study, the pooled incidence of HIT in ECMO-supported patients is 4.2%, and it contributes to adverse outcomes. Inappropriate diagnostic methods can easily lead to misdiagnosis of HIT. Further research and development of diagnostic algorithms and laboratory assays are warranted.

Meta-Analysis Comparing Bivalirudin Versus. Unfractionated Heparin in Adult Patients With Extracorporeal Membrane Oxygenation

Introduction: Unfractionated heparin (UFH) has traditionally been the agent of choice in patients on extracorporeal membrane oxygenation (ECMO). However, direct thrombin inhibitors (DTI) have recently garnered more attention in ECMO because of their advantages over UFH. Given the heterogeneous results of multiple recent published studies, we performed a meta-analysis to describe pooled outcomes between bivalirudin and UFH anticoagulation in patients on ECMO. Methods: Relevant studies were identified from MEDLINE and Google Scholar database searches through April 23, 2022. The primary efficacy outcome was thromboembolism (TE), and secondary efficacy outcomes included all-cause mortality and circuit thrombosis. The primary safety outcome was major bleeding. Results: A total of 6 studies were included in the meta-analysis. Bivalirudin use was associated with significantly lower risk of TE (OR 0.61; 95% CI 0.38-.99; P = .05; I2 = 0%) and circuit thrombosis (OR 0.51; 95% CI .32-.80; P = .004; I2 = 0%) compared with UFH. There was no significant difference in all-cause mortality risk (OR 0.75; 95% CI .52-1.09; P = .13; I2 = 30%) between the bivalirudin and UFH groups. No significant difference in the risk of major bleeding between 2 groups was found (OR 0.67; 95% CI 0.25-1.81; P = .43; I2 = 80%). Conclusion: These data support that bivalirudin is a reasonable alternative to UFH in patients on ECMO. Randomized controlled trials are needed to confirm bivalirudin's efficacy and safety results compared with UFH.

Use of bivalirudin after initial heparin management among adult patients on long-term venovenous extracorporeal support as a bridge to lung transplant: A case series

A growing body of evidence supports the use of bivalirudin as an alternative to unfractionated heparin (UFH) for the prevention of thrombotic events in patients on venovenous (VV) extracorporeal membrane oxygenation (ECMO). However, data in patients bridged to lung transplantation are limited. In this case series, we describe the outcomes of six patients who were transitioned from UFH to bivalirudin during their course of VV ECMO support as a bridge to lung transplantation. All six patients were on VV ECMO support until transplant, with a median duration of 73 days. Bivalirudin demonstrated a shorter time to first therapeutic activated thromboplastin time (aPTT) level. Additionally, time in therapeutic range was longer while patients were receiving bivalirudin compared to UFH (median 92.9% vs. 74.6%). However, major bleeding and thrombotic events occurred while patients were receiving either anticoagulant. Based on our experience, bivalirudin appears to be a viable option for anticoagulation in VV ECMO patients bridged to lung transplantation. Larger studies evaluating the optimal anticoagulation strategy in patients bridged to transplant are needed.

Anticoagulation strategies in patients with extracorporeal membrane oxygenation: A network meta-analysis and systematic review

OBJECTIVES

Extracorporeal membrane oxygenation (ECMO) plays an important role in providing temporary life support for patients with severe cardiac or pulmonary failure, but requires strict anticoagulation and monitoring. This network meta-analysis systematically explored the most effective anticoagulation and monitoring strategies for patients receiving ECMO.

METHODS

MEDLINE, Embase, Web of Science, and the Cochrane Central Register of Controlled Trials were searched up to January 31, 2023, for studies comparing unfractionated heparin (UFH), argatroban (Arg), bivalirudin (Biv), and/or nafamostat mesylate (NM) in patients receiving ECMO. The primary outcomes included device-related thrombosis, patient-related thrombosis, and major bleeding events. The secondary outcomes included ECMO survival, ECMO duration, and in-hospital mortality.

RESULTS

A total of 2522 patients from 23 trials were included in the study. Biv was associated with a decreased risk of device-related thrombosis (odd ratio [OR] 0.51, 95% confidence interval [CI]: 0.33-0.84) compared with UFH, whereas NM (OR 2.2, 95% CI: 0.24-65.0) and Arg (OR 0.92, 95% CI: 0.43-2.0) did not reduce the risk of device-related thrombosis compared with UFH. Biv was superior to Arg in decreasing the risk of device-related thrombosis (OR 0.14, 95% CI: 0.03-0.51). Biv reduced the risk of patient-related thrombosis compared with UFH (OR 0.44, 95% CI: 0.18-0.85); NM (OR 0.65, 95% CI: 0.14-3.3) and Arg (OR 3.1, 95% CI: 0.94-12.0) did not decrease risk of patient-related thrombosis compared with UFH. No significant difference was observed in the risk of major bleeding between three alternatives and UFH: Biv (OR 0.54, 95% CI: 0.23-1.3), Arg (OR 1.3, 95% CI: 0.34-5.8), and NM (OR 0.60, 95% CI: 0.13-2.6). NM showed a reduced risk of in-hospital mortality compared with UFH (OR 0.27, 95% CI: 0.091-0.77), whereas Arg (OR 0.43, 95% CI: 0.15-1.2) and Biv (OR 0.75, 95% CI: 0.52-1.1) did not decrease risk of in-hospital mortality.

CONCLUSIONS

Compared with UFH and Arg, Biv reduces the risk of thrombosis and appears to be a better choice for patients requiring ECMO. NM was associated with a reduced risk of in-hospital mortality.

Bivalirudin versus heparin anticoagulation in patients receiving extracorporeal membrane oxygenation

OBJECTIVE

Bivalirudin has been suggested as an alternative to heparin for anticoagulation in patients receiving extracorporeal membrane oxygenation (ECMO). Nevertheless, there is limited evidence about the benefit of bivalirudin in ECMO patients compared with heparin. Hence, we conducted a meta-analysis to assess the effect of bivalirudin versus heparin on clinical outcomes in patients receiving ECMO.

METHODS

PubMed, Embase, and the Cochrane Library were systematically searched from inception up to 1 April 2022 for cohort studies and randomized controlled trials comparing bivalirudin versus heparin in patients who received ECMO. The primary outcome was short-term death. Secondary outcomes included thrombotic events and bleeding events.

RESULTS

We selected 12 retrospective cohort studies with 1232 ECMO patients focusing on bivalirudin anticoagulation (n = 497) versus heparin anticoagulation (n = 735). Two hundred and one of 497 patients (40.4%) in the bivalirudin group versus 350 of 735 patients (47.6%) in the heparin group did not survive to hospital discharge. Compared with the heparin group, bivalirudin anticoagulation did not significantly decrease in-hospital mortality in patients receiving ECMO (RR, 0.95; 95% CI, 0.79-1.13; p = 0.546). Fifty-seven of 374 patients (15.2%) in the bivalirudin versus 99 of 381 patients (26.0%) in the heparin group suffered from thrombotic events. Compared with the heparin group, bivalirudin anticoagulation did not significantly decrease the rate of thrombotic events for patients receiving ECMO (RR, 0.78; 95% CI, 0.45-1.35; p = 0.378). However, bivalirudin anticoagulation significantly decreased the incidence of bleeding events compared to the heparin group (RR, 0.48; 95% CI, 0.25-0.95; p = 0.035).

CONCLUSIONS

Compared with heparin anticoagulation, bivalirudin did not decrease the rates of short-term mortality and thrombotic events, but reduced the incidence of bleeding events in patients receiving ECMO.

Is it time to switch to bivalirudin for ECMO anticoagulation?

For decades, unfractionated heparin (hereafter, heparin) has been the primary anticoagulant used for extracorporeal membrane oxygenation (ECMO) support. More recently, however, bivalirudin, a direct thrombin inhibitor, has emerged as an alternative. This systematic review based on PRISMA guidelines, aims to summarize 16 comparative studies and 8 meta-analysis and review articles published from January, 2011 till May, 2023 which directly compares ECMO courses using heparin versus bivalirudin as the anticoagulant. While this comparison is complicated by the lack of a standardized definition of major bleeding or thrombosis, our overall findings suggest there is no statistical difference between heparin and bivalirudin in incidence of bleeding and thrombosis. That said, some studies found a statistical significance favoring bivalirudin in reducing major bleeding, thrombosis, and the need for transfusions. We also offer essential guidance for appropriately selecting an anticoagulant and monitoring its effect in ECMO settings.

Commercial and novel anticoagulant ECMO coatings: a review

Extracorporeal membrane oxygenation (ECMO) is an invasive and last-resort treatment for circulatory and respiratory failure. Prolonged ECMO support can disrupt the coagulation and anticoagulation systems in a patient, leading to adverse consequences, such as bleeding and thrombosis. To address this problem, anticoagulation coatings have been developed for use in ECMO circuits. This article reviews commonly used commercial and novel anticoagulant coatings developed in recent years and proposes a new classification of coatings based on the current state. While commercial coatings have been used clinically for decades, this review focuses on comparing the effectiveness and stability of coatings to support clinical selections. Furthermore, novel anticoagulation coatings often involve complex mechanisms and elaborate design strategies, and this review summarises representative studies on mainstream anticoagulation coatings to provide a point of reference for future studies.

Surface Modification of Oxygenator Fibers with a Catalytically Active Metal-Organic Framework to Generate Nitric Oxide: An Ex Vivo Pilot Study

Coating all portions of an extracorporeal membrane oxygenation (ECMO) circuit with materials exhibiting inherent, permanent antithrombotic properties is an essential step to prevent thrombus-induced complications. However, developing antithrombotic coatings for oxygenator fibers within membrane oxygenators of ECMO systems has proven challenging. We have used polydopamine (PDA) to coat oxygenator fibers and immobilize a Cu-based metal-organic framework (MOF) on the surface to act as a nitric oxide (NO) catalyst. Importantly, the PDA/MOF coating will produce NO indefinitely from endogenous S-nitrosothiols and it has not previously been applied to ECMO oxygenator fibers.

Comparison of bivalirudin versus heparin in adult extracorporeal membrane oxygenation anticoagulant therapy: A retrospective case-control study

INTRODUCTION

There were controversial opinions on the use of bivalirudin versus heparin for anticoagulant therapy in extracorporeal membrane oxygenation. The aim of our present study is to evaluate the efficacy and safety of bivalirudin versus heparin for the maintenance of systemic anticoagulation during adult veno-venous extracorporeal membrane oxygenation (V-V ECMO).

METHODS

Adult patients who received V-V ECMO support in our center between February 2018and February 2022 were retrospectively recruited. We analyzed their ECMO support time, platelet count, coagulation indicators, blood product infusion volume, the incidence of thrombosis and bleeding, probability of successful weaning of ECMO, and in-hospital mortality.

RESULTS

A total of 58 patients received V-V ECMO support. Thirty-four patients were finally included according to the exclusion and inclusion criteria, 14 and 20 accepted bivalirudin and heparin for anticoagulant therapy, respectively. The Minimum platelet value (98.50 × 10⁹/L (85.50, 123.75) vs 49.50 × 10⁹/L (31.25, 83.00), p = 0.002) and mean platelet value (149.90 × 10⁹/L (127.40, 164.80) vs 74.55 × 10⁹/L (62.45, 131.60), p = 0.03) and the ratio of successful weaning of ECMO (92.8% vs 60.0%, p = 0.033) in bivalirudin group were significantly higher than those in heparin group. The red blood cell infusion volume (7.00 U (3.00, 13.25) vs 13.75 U (7.25, 22.63), p = 0.039), platelet infusion volume (0.00 mL (0.00, 75.00) vs 300 mL (0.00, 825.00), p = 0.027), and the incidence of major bleeding (0.00% vs 30%, p = 0.024) in bivalirudin group were significantly lower than those in heparin group.

CONCLUSIONS

In V-V ECMO-supported adult patients, systemic anticoagulation with bivalirudin has achieved the same anticoagulation targets as heparin with less frequency of major bleeding events and lower requirement for blood products without significantly increased risk of thrombosis. Bivalirudin most likely is a safe and effective anticoagulation method for adult patients supported by V-V ECMO.

Anticoagulation Management during Extracorporeal Membrane Oxygenation-A Mini-Review

Extracorporeal membrane oxygenation (ECMO) has been established as a life-saving technique for patients with the most severe forms of respiratory or cardiac failure. It can, however, be associated with severe complications. Anticoagulation therapy is required to prevent ECMO circuit thrombosis. It is, however, associated with an increased risk of hemocoagulation disorders. Thus, safe anticoagulation is a cornerstone of ECMO therapy. The most frequently used anticoagulant is unfractionated heparin, which can, however, cause significant adverse effects. Novel drugs (e.g., argatroban and bivalirudin) may be superior to heparin in the better predictability of their effects, functioning independently of antithrombin, inhibiting thrombin bound to fibrin, and eliminating heparin-induced thrombocytopenia. It is also necessary to keep in mind that hemocoagulation tests are not specific, and their results, used for setting up the dosage, can be biased by many factors. The knowledge of the advantages and disadvantages of particular drugs, limitations of particular tests, and individualization are cornerstones of prevention against critical events, such as life-threatening bleeding or acute oxygenator failure followed by life-threatening hypoxemia and hemodynamic deterioration. This paper describes the effects of anticoagulant drugs used in ECMO and their monitoring, highlighting specific conditions and factors that might influence coagulation and anticoagulation measurements.

Outcomes With Direct and Indirect Thrombin Inhibition During Extracorporeal Membrane Oxygenation for COVID-19

Anticoagulation during extracorporeal membrane oxygenation (ECMO) for Coronovirus Disease 2019 (COVID-19) can be performed by direct or indirect thrombin inhibitors but differences in outcomes with these agents are uncertain. A retrospective, multicenter study was conducted. All consecutive adult patients with COVID-19 placed on ECMO between March 1, 2020 and April 30, 2021 in participating centers, were included. Patients were divided in groups receiving either a direct thrombin inhibitor (DTI) or an indirect thrombin inhibitor such as unfractionated heparin (UFH). Overall, 455 patients with COVID-19 from 17 centers were placed on ECMO during the study period. Forty-four patients did not receive anticoagulation. Of the remaining 411 patients, DTI was used in 160 (39%) whereas 251 (61%) received UFH. At 90-days, in-hospital mortality was 50% (DTI) and 61% (UFH), adjusted hazard ratio: 0.81, 95% confidence interval (CI): 0.49-1.32. Deep vein thrombosis [adjusted odds ratio (aOR): 2.60, 95% CI: 0.90-6.65], ischemic (aOR: 1.58, 95% CI: 0.18-14.0), and hemorrhagic (aOR:1.22, 95% CI: 0.39-3.87) stroke were similar with DTI in comparison to UFH. Bleeding requiring transfusion was lower in patients receiving DTI (aOR: 0.40, 95% CI: 0.18-0.87). Anticoagulants that directly inhibit thrombin are associated with similar in-hospital mortality, stroke, and venous thrombosis and do not confer a higher risk of clinical bleeding in comparison to conventional heparin during ECMO for COVID-19.

Knowledge gaps and research priorities in adult veno-arterial extracorporeal membrane oxygenation: a scoping review

PURPOSE

This scoping review aims to identify and describe knowledge gaps and research priorities in veno-arterial extracorporeal membrane oxygenation (VA-ECMO).

METHODS

An expert panel was recruited consisting of eight international experts from different backgrounds. First, a list of priority topics was made. Second, the panel developed structured questions using population, intervention, comparison and outcomes (PICO) format. All PICOs were scored and prioritized. For every selected PICO, a structured literature search was performed.

RESULTS

After an initial list of 49 topics, eight were scored as high-priority. For most of these selected topics, current literature is limited to observational studies, mainly consisting of retrospective cohorts. Only for ECPR and anticoagulation, randomized controlled trials (RCTs) have been performed or are ongoing. Per topic, a summary of the literature is stated including recommendations for further research.

CONCLUSIONS

This scoping review identifies and presents an overview of knowledge gaps and research priorities in VA-ECMO. Current literature is mostly limited to observational studies, although with increasing attention for this patient population, more RCTs are finishing or ongoing. Translational research, from preclinical trials to high-quality or randomized controlled trials, is important to improve the standard practices in this critically ill patient population. Take-home message This scoping review identifies and presents an overview of research gaps and priorities in VA-ECMO. Translational research, from preclinical trials to high-quality or randomized controlled trials, is important to improve the standard practices in this critically ill patient population.

Comparison of Bivalirudin Versus Heparin for Anticoagulation During Extracorporeal Membrane Oxygenation

The effect and safety of bivalirudin compared with heparin in patients undergoing extracorporeal membrane oxygenation (ECMO) remains unclear. Therefore, we conducted a systematic review and meta-analysis to compare the effectiveness and safety of heparin and bivalirudin in patients who underwent ECMO. We searched Embase, the Cochrane Central Register of Controlled Trials, and MEDLINE. Inclusion criteria included patients (1) undergoing ECMO and (2) receiving bivalirudin or heparin. We excluded studies where the majority of patients switched heparin to bivalirudin or vice versa during the clinical course. The primary outcome was short-term mortality. We presented the results of all analyses with the use of random-effects models. Eleven studies reported short-term mortality. The use of bivalirudin was associated with significantly lower short-term mortality, compared with heparin (odds ratio: 0.71, 95% confidence interval, 0.55-0.92; p = 0.01, I2 = 7%). In this meta-analysis of observational studies, the use of bivalirudin was associated with significantly lower short-term mortality, compared with heparin. Further prospective studies are warranted to clarify this finding.

Evaluation of clinical outcomes in patients treated with heparin or direct thrombin inhibitors during extracorporeal membrane oxygenation: a systematic review and meta-analysis

BACKGROUND

The number of patients treated with extracorporeal membrane oxygenation (ECMO) devices is increasing. Anticoagulation therapy is crucial to prevent thrombosis during ECMO therapy. Predominantly, heparin has been used as primary anticoagulant but direct thrombin inhibitors (DTI) have been established as alternatives. The aim of this systematic review and meta-analysis was to evaluate clinical outcomes in patients treated with heparin compared to different DTI during ECMO.

METHODS

A systematic search was conducted. Full scientific articles were sought for inclusion if heparin anticoagulation was compared to DTI (argatroban/bivalirudin) in ECMO patients. Risk of bias was assessed by Newcastle Ottawa scale. Primary endpoint was in-hospital mortality. Bleeding events, thrombotic events, hours of ECMO support, days of hospital stay, percentage of time within therapeutic range and time to therapeutic range were extracted from full texts as secondary endpoints. Results were presented as Forrest-plots. GRADE was used for confidence assessment in outcomes.

RESULTS

Systematic search identified 4.385 records, thereof 18 retrospective studies for a total of 1942 patients, complied with the predefined eligibility criteria:15 studies investigated bivalirudin and 3 studies investigated argatroban versus heparin. Risk of bias was high for most studies. In-hospital mortality, major bleeding events and pump-related thrombosis were less frequent in DTI group as compared to heparin [mortality-OR 0.69, 95% CI 0.54-0.86; major bleeding-OR 0.48, 95% CI 0.29-0.81; pump thrombosis-OR 0.55, 95% CI 0.40-0.76]. Additionally, percentage of time within therapeutic range was higher for DTI [SMD 0.54, 95% CI 0.14-0.94]. GRADE approach revealed a very low level of certainty for each outcome.

CONCLUSION

In this meta-analysis, DTI and especially bivalirudin showed beneficial effects on clinical outcomes in ECMO patients as compared to heparin. However, due to the lack of randomized trials, certainty of evidence is low.

TRIAL REGISTRATION

This systematic review and meta-analysis was prospectively registered at PROSPERO data base (reference number CRD42021237252 ).

Evaluation of anticoagulation with bivalirudin for heparin-induced thrombocytopenia during extracorporeal membrane oxygenation

INTRODUCTION

Unfractionated heparin is the most commonly utilized anticoagulant in extracorporeal membrane oxygenation (ECMO) due to clinician familiarity, ease of reversal, and low cost compared to alternative agents. However, heparin's anticoagulant effect can be unpredictable and its use accompanies a risk of heparin induced thrombocytopenia (HIT). Successful use of bivalirudin as an alternative to heparin in non-HIT ECMO patients has previously been described. However, there is a paucity of data regarding its utilization in patients with confirmed HIT on ECMO.

METHODS

This single-center retrospective chart review at Cleveland Clinic Main Campus included 12 ECMO patients who were managed with bivalirudin for a new diagnosis of HIT. Descriptive statistical analyses were performed utilizing median with interquartile range and number with percent as appropriate.

RESULTS

Of the 12 patients included, median ECMO duration was 328.5 (218.8-502.1) h and venoarterial ECMO was the most common configuration. No patients experienced the primary outcome of in-circuit thrombosis while on bivalirudin. One patient developed a deep vein thrombosis 22.5 h after switching from heparin to bivalirudin. Major bleeding occurred during bivalirudin therapy in 8 (66.7%) patients.

CONCLUSIONS

Overall, our study results suggest that bivalirudin is effective for the management of HIT and did not show evidence of in-circuit thrombosis. A high incidence of major bleeding was observed with bivalirudin use within this study. Clinicians should view bivalirudin as an acceptable agent for the treatment of HIT in the ECMO population, but must consider bleeding risk given the lack of effective reversal agents.

Bivalirudin versus heparin in adult and pediatric patients with extracorporeal membrane oxygenation therapy: a systematic review and meta-analysis

BACKGROUND

Our study sought to investigate the efficacy and safety of bivalirudin versus those of unfractionated heparin (UFH) in patients undergoing extracorporeal membrane oxygenation (ECMO).

METHODS

PubMed, EMBASE and Cochrane Library were searched for studies enrolling ECMO patients on bivalirudin and UFH (from inception till July 2021). Meta-analysis was conducted. The I² statistic and p value were used in measuring heterogeneity, and random effects or fixed-effect model was adopted. The Newcastle-Ottawa Scale was used for the risk of bias assessment. Sensitivity and subgroup analyses were undertaken. We performed Egger's test to evaluate publication bias.

RESULTS

Fourteen eligible retrospective observational studies with 1501 subjects were identified. Compared with UFH, bivalirudin significantly reduced the risk of in-circuit thrombosis (OR = 0.44, 95% CI [0.31-0.61], p = 0.000), thrombosis (OR = 0.61, 95% CI [0.45-0.83], p = 0.002) and hospital mortality (OR = 0.78, 95% CI [0.61-0.99], p = 0.04) and had a positive impact on survival ECMO (OR = 1.50, 95% CI [1.04-2.16], p = 0.032). Decrease in risk of bleeding (OR = 0.36, 95% CI [0.14-0.91], p = 0.031) associated with bivalirudin was observed. Sources of heterogeneity were identified, and sensitivity analysis revealed similar results.

CONCLUSION

Our meta-analysis suggested that bivalirudin was associated with the decreased risk of in-circuit thrombosis, thrombosis, hospital mortality and bleeding in patients on ECMO and improved survival ECMO, indicating the superiority of bivalirudin to UFH in terms of efficacy and safety.