Platelet Function During Extracorporeal Membrane Oxygenation in Adult Patients

Platelet Adhesion and Activation in an ECMO Thrombosis-on-a-Chip Model

Use of extracorporeal membrane oxygenation (ECMO) for cardiorespiratory failure remains complicated by blood clot formation (thrombosis), triggered by biomaterial surfaces and flow conditions. Thrombosis may result in ECMO circuit changes, cause red blood cell hemolysis, and thromboembolic events. Medical device thrombosis is potentiated by the interplay between biomaterial properties, hemodynamic flow conditions and patient pathology, however, the contribution and importance of these factors are poorly understood because many in vitro models lack the capability to customize material and flow conditions to investigate thrombosis under clinically relevant medical device conditions. Therefore, an ECMO thrombosis-on-a-chip model is developed that enables highly customizable biomaterial and flow combinations to evaluate ECMO thrombosis in real-time with low blood volume. It is observed that low flow rates, decelerating conditions, and flow stasis significantly increased platelet adhesion, correlating with clinical thrombus formation. For the first time, it is found that tubing material, polyvinyl chloride, caused increased platelet P-selectin activation compared to connector material, polycarbonate. This ECMO thrombosis-on-a-chip model can be used to guide ECMO operation, inform medical device design, investigate embolism, occlusion and platelet activation mechanisms, and develop anti-thrombotic biomaterials to ultimately reduce medical device thrombosis, anti-thrombotic drug use and therefore bleeding complications, leading to safer blood-contacting medical devices.

Extracorporal Membrane Oxygenation in Massive Pulmonary Embolism

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Improving ECMO therapy: Monitoring oxygenator functionality and identifying key indicators, factors, and considerations for changeout

INTRODUCTION

The optimal timing for extracorporeal membrane oxygenation (ECMO) circuit change-out is crucial for the successful management of patients with severe cardiopulmonary failure. This comprehensive review examines the various factors that influence the timing of oxygenator replacement in the ECMO circuit. By considering these factors, clinicians can make informed decisions to ensure timely and effective change-out, enhancing patient outcomes and optimizing the delivery of ECMO therapy.

METHODOLOGY

A thorough search of relevant studies on ECMO circuits and oxygenator change-out was conducted using multiple scholarly databases and relevant keywords. Studies published between 2017 and 2023 were included, resulting in 40 studies that met the inclusion criteria.

DISCUSSION

Thrombosis within the membrane oxygenator and its impact on dysfunction were identified as significant contributors, highlighting the importance of monitoring coagulation parameters and gas exchange. Several factors, including fibrinogen levels, pre and post-membrane blood gases, plasma-free hemoglobin, D-dimers, platelet function, flows and pressures, and anticoagulation strategy, were found to be important considerations when determining the need for an oxygenator or circuit change-out. The involvement of a multidisciplinary team and thorough preparation were also highlighted as crucial aspects of this process.

CONCLUSION

In conclusion, managing circuit change-outs in ECMO therapy requires considering factors such as fibrinogen levels, blood gases, plasma-free hemoglobin, D-dimers, platelet function, flows, pressures, and anticoagulation strategy. Monitoring these parameters allows for early detection of issues, timely interventions, and optimized ECMO therapy. Standardized protocols, personalized anticoagulation approaches, and non-invasive monitoring techniques can improve the safety and effectiveness of circuit change-outs. Further research and collaboration are needed to advance ECMO management and enhance patient outcomes.

Interest in the new thromboelastometry device, Clot Pro®, for predicting thrombocytopenia and hypofibrinogenemia during lung transplantation

INTRODUCTION

Lung transplantation is associated with high proportion of transfusion. Monitoring of coagulopathy using viscoelastic tests could aid in the perioperative management of bleeding. The aim of the study was to assess the predictive cut-off values for thrombocytopenia and hypofibrinogenemia using the new thromboelastography analyzer, ClotPro.

METHODS

We retrospectively enrolled 65 patients who underwent lung transplantation and were sampled for both viscoelastic assays and conventional coagulation assays simultaneously during the procedure. We characterized the correlation between the EX-test (extrinsic pathway) and platelet count as well as between the FIB-test (extrinsic pathway after platelet inhibition) and fibrinogen concentration. Then, we used ROC curve analysis to determine the optimal EX-test and FIB-test values for predicting thrombocytopenia and hypofibrinogenemia.

RESULTS

All the amplitude values of the EX-test (A5, A10, A20, MCF) showed correlation with platelets count (Spearman's rank correlation coefficient ranging from 0.75 to 0.77, all p < 0.0001). We also observed a strong correlation between the amplitude values of the FIB-test (A5, A10, A20 and MCF) and the fibrinogen concentration (Spearman's rank correlation coefficient ranging from 0.68 to 0.71, all p < 0.0001). The AUCs of the EX-test values for thrombocytopenia <100 G/L and <80 G/L ranged from 0.80 to 0.93. Similarly, the AUCs of the FIB-test values for hypofibrinogenemia <1.5 g/L and <2 g/L ranged from 0.74 to 0.83. These results indicate that only the five-minute parameter of thromboelastometry is sufficient for detecting thrombocytopenia and hypofibrinogenemia in patients undergoing lung transplantation. The proposed cut off values for the EX-test to predict thrombocytopenia <80 G/L showed high sensitivity (>86 %), high specificity (>89 %) and high negative predictive value (>95 %). FIB-test cut off values predictive of fibrinogen below 1.5 g/L showed sensitivity (>78 %), specificity (>55 %) and negative predictive value (>88 %).

CONCLUSIONS

Our study provided preliminary results that are useful for developing a ClotPro-based algorithm to guide transfusion in lung transplantation. Future interventional studies will be necessary to validate these cut-off values of ClotPro for guiding transfusion.

Intracranial hemorrhage in a large cohort of patients supported with veno-venous ECMO. A retrospective single-center analysis

BACKGROUND

Intracranial bleeding (ICB) is a serious complication during veno-venous extracorporeal membrane oxygenation (V-V ECMO), with potentially fatal consequences.

PURPOSE

This study aimed to evaluate the incidence, time of detection of ICB among patients treated with V-V ECMO and potential risk factors for developing ICB during V-V ECMO.

METHODS

Five hundred fifty six patients were included in this retrospective single center analysis.

RESULTS

Median time on V-V ECMO was 9 (IQR 6-15) days. Intracranial bleeding during V-V ECMO was detected in 10.9% of all patients (61 patients with ICB). Only 17 patients with ICB presented obvious clinical symptoms. Intracranial bleeding was detected on cerebral imaging in median after 5 days (IQR 1-14) after starting V-V ECMO. Overall survival to hospital discharge was 63.7% (ICB: 29.5%). Risk factors of ICB before starting V-V ECMO in univariable analysis were platelets <100/nl (OR: 3.82), creatinine >1.5mg/dl (OR: 1.98), norepinephrine >2.5mg/h (OR: 2.5), ASAT >80U/L (OR: 1.86), blood-urea >100mg/dl (OR: 1.81) and LDH >550u/L (OR: 2.07). Factors associated with cannulation were rapid decrease in paCO2 >35mmHg (OR: 2.56) and rapid decrease in norepinephrine >1mg/h (OR: 2.53). Multivariable analysis revealed low platelets, high paCO2 before ECMO, and rapid drop in paCO2 after V-V ECMO initiation as significant risk factors for ICB.

CONCLUSION

The results emphasize that ICB is a frequent complication during V-V ECMO. Many bleedings were incidental findings, therefore screening for ICB is advisable. The univariate risk factors reflect the underlying disease severity, coagulation disorders and peri-cannulation factors, and may help to identify patients at risk.

Bleeding patients on extracorporeal membrane oxygenation have reduced platelet aggregation and plasma fibrinogen: a longitudinal observational study

This study investigated changes in coagulation and associations with occurrence of bleeding and thrombosis during extracorporeal membrane oxygenation (ECMO) therapy. The study included 100 adult ECMO-patients. Standard coagulation parameters, platelet aggregation and thromboelastometry (ROTEM®) were compared with healthy controls. Data on bleeding and thrombosis were collected until recovery or death. Mortality data were collected 30 days after weaning from ECMO. During ECMO therapy, 53 patients experienced at least one moderate or major bleed. Among these, 42 (79%) patients experienced the first bleeding on day 1 or 2. Platelet aggregation and ROTEM® revealed a hypocoagulable state in ECMO patients when compared with healthy controls. Patients bleeding on day 1 or 2, had lower platelet count (p = 0.04), poorer platelet aggregation and lower levels of fibrinogen (p < 0.01) than patients not bleeding on day 1 or 2. Further, ROTEM® clot propagation was reduced in bleeding patients (p < 0.001). Mortality was higher among bleeding patients than patients not bleeding on day 1 or 2 (67% versus 34%, p < 0.01). Congruity existed between ROTEM® measurements and standard coagulation assays, but plasma fibrinogen had a stronger association with bleeding than ROTEM® measurements. The present study does not support ROTEM® analysis as a routine part of coagulation monitoring during ECMO therapy.

The serum proteome of VA-ECMO patients changes over time and allows differentiation of survivors and non-survivors: an observational study

BACKGROUND

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is applied in patients with refractory hemodynamic failure. Exposure of blood components to high shear stress and the large extracorporeal surfaces in the ECMO circuit trigger a complex inflammatory response syndrome and coagulopathy which are believed to worsen the already poor prognosis of these patients. Mass spectrometry-based proteomics allow a detailed characterization of the serum proteome as it provides the identity and concentration of large numbers of individual proteins at the same time. In this study, we aimed to characterize the serum proteome of patients receiving VA-ECMO.

METHODS

Serum samples were collected on day 1 and day 3 after initiation of VA-ECMO. Samples underwent immunoaffinity based depletion for the 14 most abundant serum proteins, in-solution digestion and PreOmics clean-up. A spectral library was built with multiple measurements of a master-mix sample using variable mass windows. Individual samples were measured in data independent acquisition (DIA) mode. Raw files were analyzed by DIA-neural network. Unique proteins were log transformed and quantile normalized. Differential expression analysis was conducted with the LIMMA-R package. ROAST was applied to generate gene ontology enrichment analyses.

RESULTS

Fourteen VA-ECMO patients and six healthy controls were recruited. Seven patients survived. Three hundred and fifty-one unique proteins were identified. One hundred and thirty-seven proteins were differentially expressed between VA-ECMO patients and controls. One hundred and forty-five proteins were differentially expressed on day 3 compared to day 1. Many of the differentially expressed proteins were involved in coagulation and the inflammatory response. The serum proteomes of survivors and non-survivors on day 3 differed from each other according to partial least-squares discriminant analysis (PLS-DA) and 48 proteins were differentially expressed. Many of these proteins have also been ascribed to processes in coagulation and inflammation (e.g., Factor IX, Protein-C, Kallikrein, SERPINA10, SEMA4B, Complement C3, Complement Factor D and MASP-1).

CONCLUSION

The serum proteome of VA-ECMO patients displays major changes compared to controls and changes from day 1 until day 3. Many changes in the serum proteome are related to inflammation and coagulation. Survivors and non-survivors can be differentiated according to their serum proteomes using PLS-DA analysis on day 3. Our results build the basis for future studies using mass-spectrometry based serum proteomics as a tool to identify novel prognostic biomarkers.

TRIAL REGISTRATION

DRKS00011106.

In Vitro Treatment of Extracorporeal Membrane Oxygenation Coagulopathy with Recombinant von Willebrand Factor or Lyophilized Platelets

OBJECTIVES

The objective was to compare primary hemostasis between adult ECMO patients and cardiac surgical patients before heparinization and cardiopulmonary bypass. Furthermore, the authors explored whether in vitro treatment of ECMO patient blood samples with recombinant von Willebrand Factor (vWF) or lyophilized platelets improved primary hemostasis in vitro.

DESIGN

Prospective cohort study.

SETTING

Single academic medical center.

PARTICIPANTS

Ten cardiac surgical patients and 8 adult ECMO patients.

INTERVENTIONS

Cardiac surgical patients and ECMO patients had blood samples collected, and in vitro platelet thrombus formation was assessed using the ATLAS PST device. The ECMO patients had platelet thrombus formation evaluated at baseline and after in vitro treatment with recombinant vWF or lyophilized platelets, whereas cardiac surgical patients had a single blood sample obtained before heparinization and cardiopulmonary bypass run.

MEASUREMENTS AND MAIN RESULTS

Median maximum force (39.7 v 260.2 nN) and thrombus area (0.05 v 0.11) at 5 minutes were lower in untreated ECMO patient samples compared with cardiac surgical patients (p = 0.008 and p < 0.001, respectively). The ECMO patient samples treated with recombinant vWF demonstrated an increase in both platelet maximum force (median value of 222.1 v 39.7 nN) (p = 0.01) and platelet thrombus area (median value of 0.16 v 0.05; p = 0.001). The ECMO patient samples treated with lyophilized platelets demonstrated no increase in platelet maximum force (median value of 193.3 v 39.7 nN; p = 0.18); however, there was a significant increase in platelet thrombus area (median value of 0.13 v 0.05; p = 0.04).

CONCLUSIONS

Recombinant vWF and lyophilized platelets may help to restore primary hemostasis in ECMO patients. Future studies should further evaluate the safety and efficacy of these potential therapeutics in ECMO patients.

Platelet Function is Preserved After Moderate Cardiopulmonary Bypass Times But Transiently Impaired After Protamine

OBJECTIVES

Previous studies have described impaired platelet function after cardiopulmonary bypass (CPB). Whether this is still valid in contemporary cardiac surgery is unclear. This study aimed to quantify changes in function and number of platelets during CPB in a present-day cardiac surgery cohort.

DESIGN

Prospective, controlled clinical study.

SETTING

A single-center university hospital.

PARTICIPANTS

Thirty-nine patients scheduled for coronary artery bypass graft surgery with CPB.

INTERVENTIONS

Platelet function and numbers were measured at 6 timepoints in 39 patients during and after coronary artery bypass graft surgery; at baseline before anesthesia, at the end of CPB, after protamine administration, at intensive care unit (ICU) arrival, 3 hours after ICU arrival, and on the morning after surgery.

MEASUREMENTS AND MAIN RESULTS

Platelet function was assessed with impedance aggregometry and flow cytometry. Platelet numbers are expressed as actual concentration and as numbers corrected for dilution using hemoglobin as a reference marker. There was no consistent impairment of platelet function during CPB with either impedance aggregometry or flow cytometry. After protamine administration, a decrease in platelet function was seen with impedance aggregometry and for some markers of activation with flow cytometry. Platelet function was restored 3 hours after arrival in the ICU. During CPB (85.0 ± 21 min), the number of circulating platelets corrected for dilution increased from 1.73 ± 0.42 × 10⁹/g to 1.91 ± 0.51 × 10⁹/g (p < 0.001).

CONCLUSIONS

During cardiac surgery with moderate CPB times, platelet function was not impaired, and no consumption of circulating platelets could be detected. Administration of protamine transiently affected platelet function.

Impact of surface coating and systemic anticoagulants on hemostasis and inflammation in a human whole blood model

BACKGROUND

Surface compatibility with blood is critical both for scientific investigations on hemostasis and clinical applications. Regarding in vitro and ex vivo investigations, minimal alteration in physiological hemostasis is of particular importance to draw reliable conclusions on the human coagulation system. At the same time, artificial coagulation activation must be avoided, which is relevant for the patient, for example to prevent stent graft occlusion. The aim was to evaluate the advantages and disadvantages of antithrombotic and antifouling surface coatings in the context of their suitability for ex vivo incubation and the study of coagulation properties.

METHODS

We investigated the impact of different protocols for surface coating of synthetic material and different anticoagulants on hemostasis and platelet activation in ex vivo human whole blood. Blood samples from healthy donors were incubated in coated microtubes on a rotating wheel at 37°C. Two protocols for surface coating were analyzed for hemostatic parameters and metabolic status, a heparin-based coating (CHC, Corline Heparin Conjugate) without further anticoagulation and a passivating coating (MPC, 2-methacryloyloxethyl phosphorylcholine) with added anticoagulants (enoxaparin, ENOX; or fondaparinux, FPX). Employing the MPC-based coating, the anticoagulants enoxaparin and fondaparinux were compared regarding their differential effects on plasmatic coagulation by thrombelastometry and on platelet activation by flowcytometry and platelet function assays.

RESULTS

Using the CHC coating, significant coagulation cascade activation was observed, whereas parameters remained mostly unchanged with MPC-based protocols. Extended incubation caused significantly elevated levels of the soluble membrane attack complex. Neither ENOX nor FPX caused a relevant impairment of platelet function or activation capacity and thrombelastometric parameters remained unchanged with both protocols. For translational purposes, we additionally modeled endotoxemia with the MPC-based protocols by incubating with lipopolysaccharide plus/minus thrombin. While coagulation parameters remained unchanged, elevated Interleukin 8 and Matrix Metalloproteinase 9 demonstrated preserved immune cell responsiveness.

CONCLUSIONS

The MPC-based protocols demonstrated better hemocompatibility compared to CHC, and ENOX and FPX proved useful for additional anticoagulation. Furthermore, this simple-to-use whole blood model may be useful for experimental analyses of the early coagulatory and immunological response without decalcification.

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

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

Optimal Tests to Minimise Bleeding and Ischaemic Complications in Patients on Extracorporeal Membrane Oxygenation

Patients supported with extracorporeal membrane oxygenation (ECMO) experience a very high frequency of bleeding and ischaemic complications, including stroke and systemic embolism. These patients require systemic anticoagulation, mainly with unfractionated heparin (UFH) to prevent clotting of the circuit and reduce the risk of arterial or venous thrombosis. Monitoring of UFH can be very challenging. While most centres routinely monitor the activated clotting time and activated partial thromboplastin time (aPTT) to assess UFH, measurement of anti-factor Xa (anti-Xa) level best correlates with heparin dose, and appears to be predictive of circuit thrombosis, although aPTT may be a better predictor of bleeding. Although monitoring of prothrombin time, platelet count and fibrinogen is routinely undertaken to assess haemostasis, there is no clear guidance available regarding the optimal test.Additional tests, including antithrombin level and thromboelastography, can be used for risk stratification of patients to try and predict the risks of thrombosis and bleeding. Each has their specific role, strengths and limitations. Increased thrombin generation may have a role in predicting thrombosis. Acquired von Willebrand syndrome is frequent with ECMO, contributing to bleeding risk and can be detected by assessing the von Willebrand factor activity-to-antigen ratio, while the platelet function analyser can be used in urgent situations to detect this, with a high negative predictive value. Tests of platelet aggregation can aid in the prediction of bleeding.To personalise management, a selection of complementary tests to collectively assess heparin-effect, coagulation, platelet function and platelet aggregation is proposed, to optimise clinical outcomes in these high-risk patients.

Extracorporeal Membrane Oxygenation for Pregnant and Postpartum Patients

Extracorporeal membrane oxygenation (ECMO) has seen increasing use for critically ill pregnant and postpartum patients over the past decade. Growing experience continues to demonstrate the feasibility of ECMO in obstetric patients and attest to its favorable outcomes. However, the interaction of pregnancy physiology with ECMO life support requires careful planning and adaptation for success. Additionally, the maintenance of fetal oxygenation and perfusion is essential for safely continuing pregnancy during ECMO support. This review summarizes the considerations for use of ECMO in obstetric patients and how to address these concerns.

Early platelet dysfunction in patients receiving extracorporeal membrane oxygenation is associated with mortality

Extracorporeal membrane oxygenation (ECMO) is used for patients with cardiopulmonary failure and is associated with severe bleeding and poor outcome. Platelet dysfunction may be a contributing factor. The aim of this prospective observational study was to characterize platelet dysfunction and its relation to outcome in ECMO patients. Blood was sampled from thirty ECMO patients at three timepoints. Expression of CD62P, CD63, activated GPIIb/IIIa, GPVI, GPIbα and formation platelet-leukocyte aggregates (PLA) were analyzed at rest and in response to stimulation. Delta granule storage-pool deficiency and secretion defects were also investigated. Fifteen healthy volunteers and ten patients with coronary artery disease served as controls. Results were also compared between survivors and non-survivors. Compared to controls, expression of platelet surface markers, delta granule secretion and formation of PLA was reduced, particularly in response to stimulation. Baseline CD63 expression was higher and activated GPIIb/IIIa expression in response to stimulation was lower in non-survivors on day 1 of ECMO. Logistic regression analysis revealed that these markers were associated with mortality. In conclusion, platelets from ECMO patients are severely dysfunctional predisposing patients to bleeding complications and poor outcome. Platelet dysfunction on day 1 of ECMO detected by the platelet surface markers CD63 and activated GPIIb/IIIa is associated with mortality. CD63 and activated GPIIb/IIIa may therefore serve as novel prognostic biomarkers, but future studies are required to determine their true potential.

Delayed retroperitoneal hemorrhage during extracorporeal membrane oxygenation in COVID-19 patients: A case report and literature review

BACKGROUND

Retroperitoneal hemorrhage (RPH) is a rare and severe complication in patients undergoing extracorporeal membrane oxygenation (ECMO). Clinical diagnosis is difficult.

CASE SUMMARY

Three cases of RPH patients with corona virus disease-19 (COVID-19) were included in this study. All three suffered from respiratory failure, were treated with veno-venous or veno-arterial-venous ECMO, and experienced RPH during ECMO treatment. Two of the COVID-19 cases were diagnosed after the patients experienced abdominal pain. The other patient exhibited decreases in the ECMO circuit flow rate and hemoglobin level. Two cases were treated by transcatheter arterial embolization, and one was treated conservatively. The hemorrhage in each of the three cases did not deteriorate. Satisfactory treatment results were achieved for the three patients because of prompt diagnosis and treatment.

CONCLUSION

Although the incidence of RPH during ECMO treatment is low, the risk is increased by anticoagulant use and local mechanical injury. If declines in blood flow velocity and hemoglobin are detected, RPH should be considered, and prompt aggressive therapy should be started.

Point of care diagnostic of hypercoagulability and platelet function in COVID-19 induced acute respiratory distress syndrome: a retrospective observational study

Background

Coronavirus disease 2019 (COVID-19) associated coagulopathy (CAC) leads to thromboembolic events in a high number of critically ill COVID-19 patients. However, specific diagnostic or therapeutic algorithms for CAC have not been established. In the current study, we analyzed coagulation abnormalities with point-of-care testing (POCT) and their relation to hemostatic complications in patients suffering from COVID-19 induced Acute Respiratory Distress Syndrome (ARDS). Our hypothesis was that specific diagnostic patterns can be identified in patients with COVID-19 induced ARDS at risk of thromboembolic complications utilizing POCT.

Methods

This is a single-center, retrospective observational study. Longitudinal data from 247 rotational thromboelastometries (Rotem®) and 165 impedance aggregometries (Multiplate®) were analysed in 18 patients consecutively admitted to the ICU with a COVID-19 induced ARDS between March 12th to June 30th, 2020.

Results

Median age was 61 years (IQR: 51–69). Median PaO₂/FiO₂ on admission was 122 mmHg (IQR: 87–189), indicating moderate to severe ARDS. Any form of hemostatic complication occurred in 78 % of the patients with deep vein/arm thrombosis in 39 %, pulmonary embolism in 22 %, and major bleeding in 17 %. In Rotem® elevated A10 and maximum clot firmness (MCF) indicated higher clot strength. The delta between EXTEM A10 minus FIBTEM A10 (ΔA10) > 30 mm, depicting the sole platelet-part of clot firmness, was associated with a higher risk of thromboembolic events (OD: 3.7; 95 %CI 1.3–10.3; p = 0.02). Multiplate® aggregometry showed hypoactive platelet function. There was no correlation between single Rotem® and Multiplate® parameters at intensive care unit (ICU) admission and thromboembolic or bleeding complications.

Conclusions

Rotem® and Multiplate® results indicate hypercoagulability and hypoactive platelet dysfunction in COVID-19 induced ARDS but were all in all poorly related to hemostatic complications..

Evaluation of Anti-Activated Factor X Activity and Activated Partial Thromboplastin Time Relations and Their Association with Bleeding and Thrombosis during Veno-Arterial ECMO Support: A Retrospective Study

BACKGROUND

We aimed to investigate the relationship between anti-activated Factor X (anti-FXa) and activated Partial Thromboplastin Time (aPTT), and its modulation by other haemostasis co-variables during veno-arterial extracorporeal membrane oxygenation (VA-ECMO) support. We further investigated their association with serious bleeding and thrombotic complications.

METHODS

This retrospective single-center study included 265 adults supported by VA-ECMO for refractory cardiogenic shock from January 2015 to June 2019. The concordance of anti-FXa and aPTT and their correlations were assessed in 1699 paired samples. Their independent associations with serious bleeding or thrombotic complications were also analysed in multivariate analysis.

RESULTS

The concordance rate of aPTT with anti-FXa values was 50.7%, with 39.3% subtherapeutic aPTT values. However, anti-FXa and aPTT remained associated (β = 0.43 (95% CI 0.4-0.45) 10^-2 IU/mL, p < 0.001), with a significant modulation by several biological co-variables. There was no association between anti-FXa nor aPTT values with serious bleeding or with thrombotic complications.

CONCLUSION

During VA-ECMO, although anti-FXa and aPTT were significantly associated, their values were highly discordant with marked sub-therapeutic aPTT values. These results should favour the use of anti-FXa. The effect of biological co-variables and the failure of anti-FXa and aPTT to predict bleeding and thrombotic complications underline the complexity of VA-ECMO-related coagulopathy.

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.

Association of D-dimer and Fibrinogen With Hypercoagulability in COVID-19 Requiring Extracorporeal Membrane Oxygenation

BACKGROUND

D-dimer concentration has been used by institutions to identify candidates for intensified anticoagulant treatment for venous thromboembolism prevention and for the mitigation of the microthrombotic complications associated with COVID-19. Thromboelastography (TEG) maximum amplitude (MA) has been validated as a marker of hypercoagulability and MA ≥68 mm has been utilized as a marker of hypercoagulability in other conditions.

METHODS

The goal of this study was to evaluate the relationship between coagulation, inflammatory, and TEG parameters in patients with COVID-19 on extracorporeal membrane oxygenation (ECMO). We performed a single-center retrospective analysis of consecutive patients that received ECMO for the treatment of COVID-19. TEG, inflammatory, and coagulation markers were compared in patients with and without a thrombotic complication. Correlation tests were performed to identify the coagulation and inflammatory markers that best predict hypercoagulability as defined by an elevated TEG MA.

RESULTS

A total of 168 TEGs were available in 24 patients. C-reactive protein and fibrinogen were significantly higher in patients that developed a thrombotic event versus those that did not (P = 0.04 and P = 0.04 respectively). D-dimer was negatively correlated with TEG MA (P < 0.01), while fibrinogen was positively correlated (P < 0.01). A fibrinogen >441 mg/dL was found to have a sensitivity of 91.2% and specificity of 85.7% for the detection of MA ≥68 mm.

CONCLUSIONS

In critically ill patients with COVID-19 treated with ECMO, D-dimer concentration had an inverse relationship with degree of hypercoagulability as measured by TEG MA. D-dimer elevation may potentially reflect hemostatic perturbation in patients on ECMO or the severity of COVID-19 related sepsis rather than designate patients likely to benefit from anticoagulation. Fibrinogen concentration may represent a more useful marker of hypercoagulability in this population.

Clinical management and outcome of adult patients with extracorporeal life support device-associated intracerebral hemorrhage-a neurocritical perspective and grading

Intracerebral hemorrhage (ICH) is a devastating complication in patients treated with extracorporeal membrane oxygenation (ECMO) due to respiratory or cardiac issues. Neurosurgical evaluation and management of such cases has only insufficiently been studied. We conducted a retrospective, cohort study of adult patients treated with ECMO between January 2007 and January 2017 in a tertiary healthcare center. Demographics, clinical data, coagulation status, ICH characteristics, and treatment modalities were analyzed. The primary outcome parameter was defined as mortality caused by ICH during ECMO. 525 patients with ECMO therapy were eligible for analysis. An overall incidence for any type of intracranial bleeding of 12.3% was found. Small hemorrhages accounted for 6.4% and acute subdural and epidural hematoma for 1.2%. Twenty-four (4.6%) patients developed ICH, and 11 patients (46%) died due to the ICH. Mortality was significantly higher in patients with larger ICH volumes (86.8 ± 34.8 ml vs 9.9 ± 20.3 ml, p < 0.001), intraventricular hemorrhage (83% vs 8%, p = 0.01), and a fluid level inside the ICH (75% vs 31%, p = 0.04). All patients were classified according to the bleeding pattern on the initial CT scan into 3 types. Patients with type 1 bleeding were statistically more likely to die (p < 0.001). In 15 out of 24 patients (63%), correction of the coagulation status was possible within 12 h after ICH onset. Seven out of 9 patients (78%) without early coagulation correction died compared to 2 out of 15 patients (13%), in whom early coagulation correction was successful (p = 0.01). This is the first study evaluating the course and management of patients experiencing an ICH under ECMO therapy and establishing an ICH classification based on the bleeding patterns. Early correction of the coagulation is of paramount importance in the treatment of these patients.

Veno-Arterial Extracorporeal Membrane Oxygenation for Patients Undergoing Acute Type A Aortic Dissection Surgery: A Six-Year Experience

Objectives: Acute type A aortic dissection (aTAAD) is usually lethal without emergency surgery. Although veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is widely used in patients with cardiogenic shock following cardiac surgery, VA-ECMO support following aTAAD surgery has not been well-described. Based on our 6-year experience, we aimed to retrospectively analyze risk factors, application and timing of VA-ECMO, and outcomes in aTAAD patients. Methods: In this retrospective, single-center study, we enrolled adult patients who underwent aTAAD surgery from January 2014 to December 2019 and were supported with VA-ECMO. Patients were divided into two groups according to whether or not they were successfully weaned from VA-ECMO. Preoperative, intraoperative and postoperative variables were assessed and analyzed. Outcomes of the patients were followed up until discharge. Results: Twenty-seven patients who received aTAAD surgery with VA-ECMO support were included in the study. Nine patients (33.3%) were successfully weaned from VA-ECMO. The median VA-ECMO support time and length of hospital stay in the successfully weaned group were significantly longer than in the group could not be successfully weaned (192 [111-327] vs. 55 [23-95] h, p < 0.01; 29 [18-40] vs. 4 [3-8] days, p < 0.01). Overall in-hospital mortality was 81.5%. The main causes of death were bleeding (37%), neurological complications (15%), and multiple organ dysfunction syndrome (15%). Preoperative levels of creatine kinase-MB (CK-MB) were lower in patients who were successfully weaned from VA-ECMO than in the failed group (14 [6-30] vs. 55 [28-138] U/L, p < 0.01). Postoperative peak levels of CK-MB, cardiac troponin T, lactate dehydrogenase, and lactate were significantly lower in the successful group than in the failed group. Conclusion: Postoperative VA-ECMO support was rarely used in aTAAD patients. Our study showed that VA-ECMO can be considered as a salvage treatment in aTAAD patients, despite the high rate of complications and mortality.

Clinical and pathophysiologic aspects of ECMO-associated hemorrhagic complications

Extracorporeal membrane oxygenation (ECMO) is increasingly used to treat severe cases of acute respiratory or cardiac failure. Hemorrhagic complications represent one of the most common complications during ECMO, and can be life threatening. The purpose of this study was to elucidate pathophysiological mechanisms of ECMO-associated hemorrhagic complications and their impact on standard and viscoelastic coagulation tests. The study cohort included 27 patients treated with VV-ECMO or VA-ECMO. Hemostasis was evaluated using standard coagulation tests and viscoelastic parameters investigated with rotational thromboelastometry. Anticoagulation and hemorrhagic complications were analyzed for up to seven days depending on ECMO duration. Hemorrhagic complications developed in 16 (59%) patients. There were 102 discrete hemorrhagic episodes among 116 24-hour-intervals, of which 27% were considered to be clinically significant. The highest number of ECMO-associated hemorrhages occurred on the 2^nd and 3^rd day of treatment. Respiratory tract bleeding was the most common hemorrhagic complication, occurring in 62% of the 24-hour intervals. All 24-hours-intervals were divided into two groups: “with bleeding” and “without bleeding”. The probability of hemorrhage was significantly associated with abnormalities of four parameters: increased international normalized ratio (INR, sensitivity 71%, specificity 94%), increased prothrombin time (PT, sensitivity 90%, specificity 72%), decreased intrinsic pathway maximal clot firmness (MCFin, sensitivity 76%, specificity 89%), and increased extrinsic pathway clot formation time (CFTex, sensitivity 77%, specificity 87%). In conclusions, early ECMO-associated hemorrhagic complications are related to one traditional and two novel viscoelastic coagulation abnormalities: PT/INR elevation, reduced maximum clot firmness due to intrinsic pathway dysfunction (MCFin), and prolonged clot formation time due to extrinsic pathway dysfunction (CFTex). When managing hemostasis during ECMO, derangements in PT/INR, MCFin and CFT_ex should be focused on.

Platelet Functions During Extracorporeal Membrane Oxygenation. Platelet-Leukocyte Aggregates Analyzed by Flow Cytometry as a Promising Tool to Monitor Platelet Activation

Extracorporeal membrane oxygenation (ECMO) is an extracorporeal circulation used to manage patients with severe circulatory or respiratory failure. It is associated with both high bleeding and thrombosis risks, mainly as a result of biomaterial/blood interface phenomena, high shear stress, and complex inflammatory response involving the activation of coagulation and complement systems, endothelial cells, leukocytes, and platelets. Besides their critical role in hemostasis, platelets are important players in inflammatory reactions, especially due to their ability to bind and activate leukocytes. Hence, we reviewed studies on platelet function of ECMO patients. Moreover, we addressed the issue of platelet–leukocyte aggregates (PLAs), which is a key step in both platelet and leukocyte activation, and deserves to be investigated in these patients. A reduced expression of GPIb and GPVI was found under ECMO therapy, due to the shedding processes. However, defective platelet aggregation is inconsistently reported and is still not clearly defined. Due to the high susceptibility of PLAs to pre-analytical conditions, defining and strictly adhering to a rigorous laboratory methodology is essential for reliable and reproducible results, especially in the setting of complex inflammatory situations like ECMO. We provide results on sample preparation and flow cytometric whole blood evaluation of circulating PLAs.

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.

Changes in Red Blood Cell Properties and Platelet Function during Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is associated with frequent hemorrhagic and thromboembolic complications. The multiple effects of ECMO include inflammatory response on contact with the circuit; hemolysis acquired von Willebrand syndrome likely affects the function of red blood cells (RBC) and platelets. The aim of this prospective observational study was to analyze RBC aggregation and elongation (deformability) and platelet aggregation in the first week of ECMO. Sixteen patients were included. Blood samples were taken prior to initiation of ECMO and on days 1, 2, 3, 5, and 7. RBC aggregation and elongation were analyzed using the laser-assisted optical rotational red cell analyzer (Lorrca). Upstroke, top, and amplitude as indices of aggregation showed significant time effects. RBC elongation was not affected at low shear stress. At high shear stress there was an increase in the elongation index at day 2 (p = 0.004), followed by a decrease. Platelet function was analyzed using multiple electrode aggregometry (Multiplate^®). In pairwise comparison in the days 1–7 to the value prior to ECMO there was no significant difference in platelet aggregation by any of the three agonists (ADP p = 0.61; TRAP p = 0.77; Ristocetin p = 0.25). This implies that the rheology of RBCs seemed to be more affected by ECMO than platelets. Especially the red blood cell deformability continues to decline at higher shear stress.