Hemostasis, coagulation and thrombin in venoarterial and venovenous extracorporeal membrane oxygenation: the HECTIC study

ECMO produces very rapid changes in primary hemostasis detected by PFA-200 during lung transplantation: An observational study

BACKGROUND

The pathology of primary hemostasis is a common complication of extracorporeal membrane oxygenation (ECMO) support. Scientific data describing its changes in patients on short-term ECMO support and the ability and speed of the restoration of its functions are limited.

AIMS

The aim of this study was to describe the pathology of primary hemostasis induced by short-term ECMO support and its development over time using PFA-200, ROTEM platelet, and von Willebrand factor (vWF) analyses.

METHODS

In patients undergoing lung transplantation surgery using intraoperative veno-arterial ECMO support, blood samples were analyzed using the following tests: PFA-200, ROTEM platelet tests, vWF antigen, ristocetin cofactor (RCo), and collagen-binding protein (CB) before, during, and after ECMO support.

RESULTS

Blood samples from 32 patients were analyzed. All 3 PFA-200 tests (COL/EPI, COL/ADP, and COL/P2Y) showed significant deterioration during ECMO support with rapid restoration after ECMO cessation (p < 0.05), suggesting an ECMO-induced primary hemostasis disorder. A significant increase of vWF antigen after ECMO cessation (p < 0.05) was found with an increase of RCo and CB levels, although it was not significant (p > 0.05).

CONCLUSIONS

Short-term ECMO support induces primary hemostasis pathology. It occurs immediately after initiation but is rapidly restored after ECMO cessation, which is detectable by PFA-200. Despite there being persistent platelet dysfunction after ECMO cessation, as seen with the ROTEM platelet results, the increased levels of vWF antigen might explain the normal results of primary hemostasis detected by PFA-200.

Surface Engineering for Endothelium-Mimicking Functions to Combat Infection and Thrombosis in Extracorporeal Life Support Technologies

Blood-contacting medical devices routinely fail from the cascading effects of biofouling toward infection and thrombosis. Nitric oxide (NO) is an integral part of endothelial homeostasis, maintaining platelet quiescence and facilitating oxidative/nitrosative stress against pathogens. Recently, it is shown that the surface evolution of NO can mediate cell-surface interactions. However, this technique alone cannot prevent the biofouling inherent in device failure with dynamic blood-contacting applications. This work proposes an endothelium-mimicking surface design pairing controlled NO release with an inherently antifouling polyethylene glycol interface (NO+PEG). This simple, robust, and scalable platform develops surface-localized NO availability with surface hydration, leading to a significant reduction in protein adsorption as well as bacteria/platelet adhesion. Further in vivo thrombogenicity studies show a decrease in thrombus formation on NO+PEG interfaces, with preservation of circulating platelet and white blood cell counts, maintenance of activated clotting time, and reduced coagulation cascade activation. It is anticipated that this bio-inspired surface design will enable a facile alternative to existing surface technologies to address clinical manifestations of infection and thrombosis in dynamic blood-contacting environments.

Acquired von Willebrand syndrome during extracorporeal membrane oxygenation support: a comprehensive review of current evidence: communication from the ISTH SSC on perioperative and critical care thrombosis and hemostasis

During extracorporeal membrane oxygenation (ECMO) support, the high shear stress in the ECMO circuit results in increased proteolysis of von Willebrand factor (VWF), loss of VWF high-molecular-weight multimers, and impaired ability to bind to platelets and collagen. These structural changes in VWF are consistent with acquired von Willebrand syndrome (AVWS) type 2A and may contribute to the bleeding diathesis frequently observed in ECMO patients. We performed a systematic review of all clinical studies evaluating the prevalence and associated outcomes of AVWS in ECMO patients. Our findings suggest that almost all ECMO patients develop partial or complete loss of VWF high-molecular-weight multimers within a few hours of device implantation. The AVWS persists as long as the patient is supported by ECMO. Weaning from ECMO rapidly and completely resolves the AVWS. Nevertheless, few studies have reported bleeding outcomes in ECMO patients with AVWS, and the extent to which AVWS contributes to the bleeding diathesis during ECMO support cannot be determined by current evidence. Data supporting the use of VWF concentrates to prevent bleeding complications in ECMO patients remain limited.

Antithrombin Levels and Heparin Responsiveness during Venoarterial Extracorporeal Membrane Oxygenation: A Prospective Single-center Cohort Study

BACKGROUND

Unfractionated heparin, administered during venoarterial extracorporeal membrane oxygenation to prevent thromboembolic events, largely depends on plasma antithrombin for its antithrombotic effects. Decreased heparin responsiveness seems frequent on extracorporeal membrane oxygenation; however, its association with acquired antithrombin deficiency is poorly understood. The objective of this study was to describe longitudinal changes in plasma antithrombin levels during extracorporeal membrane oxygenation support and evaluate the association between antithrombin levels and heparin responsiveness. The hypothesis was that extracorporeal membrane oxygenation support would be associated with acquired antithrombin deficiency and related decreased heparin responsiveness.

METHODS

Adults receiving venoarterial extracorporeal membrane oxygenation were prospectively included. All patients received continuous intravenous unfractionated heparin using a standardized protocol (target anti-Xa 0.3 to 0.5 IU/ml). For each patient, arterial blood was withdrawn into citrate-containing tubes at 11 time points (from hour 0 up to day 7). Anti-Xa (without dextran or antithrombin added) and antithrombin levels were measured. The primary outcome was the antithrombin plasma level. In the absence of consensus, antithrombin deficiency was defined as a time-weighted average of antithrombin less than or equal to 70%. Data regarding clinical management and heparin dosage were collected.

RESULTS

Fifty patients, including 42% postcardiotomy, were included between April 2020 and May 2021, with a total of 447 samples. Median extracorporeal membrane oxygenation duration was 7 (interquartile range, 4 to 12) days. Median antithrombin level was 48% (37 to 60%) at baseline. Antithrombin levels significantly increased throughout the follow-up. Time-weighted average of antithrombin levels was 63% (57 to 73%) and was less than or equal to 70% in 32 (64%) of patients. Overall, 45 (90%) patients had at least one antithrombin value less than 70%, and 35 (70%) had at least one antithrombin value less than 50%. Antithrombin levels were not significantly associated with heparin responsiveness evaluated by anti-Xa assay or heparin dosage.

CONCLUSIONS

Venoarterial extracorporeal membrane oxygenation support was associated with a moderate acquired antithrombin deficiency, mainly during the first 72 h, that did not correlate with heparin responsiveness.

EDITOR’S PERSPECTIVE

Safety and Effectiveness of an Anti-Xa-based Unfractionated Heparin Protocol for Impella Percutaneous Ventricular Assist Devices

Background: Impella devices are used for mechanical circulatory support in patients with cardiogenic shock or those undergoing high-risk percutaneous coronary intervention (PCI). Anticoagulation protocols in this population are not well established and are complicated by concomitant use of purge solutions containing unfractionated heparin (UFH) and intravenous UFH continuous infusion (CI) for systemic anticoagulation. Objectives: To evaluate thrombotic and bleeding complications when using a novel UFH protocol with a reduced initial UFH CI dose of 6 units/kg/hour targeting an anti-Xa goal of 0.3 to 0.5 units/mL in patients receiving Impella support. Methods: This single-center, retrospective study included 41 patients on Impella support who received an UFH purge solution and/or an IV UFH infusion. The primary outcome was overall composite bleeding. Secondary outcomes included thrombotic events and systemic UFH exposure. An exploratory analysis was performed to identify risk factors for bleeding. Results: Anti-Xa values were in therapeutic range 46% of the time while on support (interquartile range 16.6%-75%), with a median IV UFH dose of 6 units/kg/hour. The overall bleeding rate was 29.2%, with 6 minor bleeds and 2 major bleeds with no fatal bleeding or intracranial hemorrhage. Rate of overall thrombosis was 4.9%, including 1 ischemic stroke and 1 occurrence of limb ischemia. Conclusion: Use of a modified UFH protocol to target an anti-Xa goal of 0.3 to 0.5 units/mL resulted in bleeding and thrombotic event rates similar to previous literature. This protocol utilizing an initial rate of 6 units/kg/hour may be a useful approach to achieve therapeutic anticoagulation while accounting for UFH exposure from the purge solution and minimizing need for frequent calculations.

Refractory ventricular fibrillation secondary to hyperkalemia resuscitated with extracorporeal membrane oxygenation: A case report

The routine use of extracorporeal cardiopulmonary resuscitation (ECPR) is not recommended for patients with cardiac arrest. However, ECPR is considered for selected patients with cardiac arrest of reversible cause. Extracorporeal membrane oxygenation (ECMO) provides temporary cardiopulmonary support and adequate perfusion to the end organs, thereby shortening ischemic organ time and minimizing complications. One indication for ECPR therapy is prolonged ventricular fibrillation despite optimal conventional CPR. Here, we report a successful recovery case from ECPR, in which the patient suffered from refractory ventricular fibrillation and was predisposed to severe hyperkalemia. Ventricular fibrillation failed to respond despite prolonged conventional CPR and defibrillation management for 32 min. After successfully initiating ECPR 54 min after cardiac arrest, spontaneous circulation returned sooner. He demonstrated clear consciousness after treatment and was discharged without any neurological disability on day 11.

Factors Influencing Successful Weaning From Venoarterial Extracorporeal Membrane Oxygenation: A Systematic Review

With advancements in extracorporeal life support (ECLS) technologies, venoarterial extracorporeal membrane oxygenation (VA-ECMO) has emerged as a crucial cardiopulmonary support mechanism. This review explores the significance of VA-ECMO system configuration, cannulation strategies, and timing of initiation. Through an analysis of medication management strategies, complication management, and comprehensive preweaning assessments, it aims to establish a multidimensional evaluation framework to assist clinicians in making informed decisions regarding weaning from VA-ECMO, thereby ensuring the safe and effective transition of 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.

Outcomes of heparinized adult veno-arterial extracorporeal membrane oxygenation patients managed with low and high activated partial thromboplastin time targets: A systematic review and meta-analysis

INTRODUCTION

There are no randomized controlled trials comparing low and high activated partial thromboplastin time (aPTT) targets in heparinized adult veno-arterial (VA) extracorporeal membrane oxygenation (ECMO) patients. Our systematic review and meta-analysis summarized complication rates in adult VA ECMO patients treated with low and high aPTT targets.

METHODS

Studies published from January 2000 to May 2022 were identified using Pubmed, Embase, Cochrane Library, and LILACS (Latin American and Caribbean Health Sciences Literature). Studies were included if aPTT was primarily used to guide heparin anticoagulation. For the low aPTT group, we included studies where aPTT goal was ≤60 seconds and for the high aPTT group, we included studies where aPTT goal was ≥60 seconds. Proportional meta-analysis with a random effects model was used to calculate pooled complication rates for patients in the two aPTT groups.

RESULTS

Twelve studies met inclusion criteria (5 in the low aPTT group and 7 in the high aPTT group). The pooled bleeding complication incidence for low aPTT studies was 53.6% (95% CI = 37.4%-69.4%, I2 = 60.8%) and for high aPTT studies was 43.8% (95% CI = 21.7%-67.1%, I2 = 91.8%). No studies in the low aPTT group reported overall thrombosis incidence, while three studies in the high aPTT group reported overall thrombosis incidence. The pooled thrombosis incidence for high aPTT studies was 16.1% (95% CI = 9.0%-24.5%, I2 = 13.1%).

CONCLUSIONS

Adult ECMO patients managed with low and high aPTT goals appeared to have similar bleeding and other complication rates further highlighting the need for a randomized controlled trial.

Detecting Oxygenator Thrombosis in ECMO: A Review of Current Techniques and an Exploration of Future Directions

Extracorporeal membrane oxygenation (ECMO) is a life-support technique used to treat cardiac and pulmonary failure, including severe cases of COVID-19 (coronavirus disease 2019) involving acute respiratory distress syndrome. Blood clot formation in the circuit is one of the most common complications in ECMO, having potentially harmful and even fatal consequences. It is therefore essential to regularly monitor for clots within the circuit and take appropriate measures to prevent or treat them. A review of the various methods used by hospital units for detecting blood clots is presented. The benefits and limitations of each method are discussed, specifically concerning detecting blood clots in the oxygenator, as it is concluded that this is the most critical and challenging ECMO component to assess. We investigate the feasibility of solutions proposed in the surrounding literature and explore two areas that hold promise for future research: the analysis of small-scale pressure fluctuations in the circuit, and real-time imaging of the oxygenator. It is concluded that the current methods of detecting blood clots cannot reliably predict clot volume, and their inability to predict clot location puts patients at risk of thromboembolism. It is posited that a more in-depth analysis of pressure readings using machine learning could better provide this information, and that purpose-built imaging could allow for accurate, real-time clotting analysis in ECMO components.

Anticoagulation and Bleeding during Veno-Venous Extracorporeal Membrane Oxygenation: Insights from the PROTECMO Study

Rationale: Definitive guidelines for anticoagulation management during veno-venous extracorporeal membrane oxygenation (VV ECMO) are lacking, whereas bleeding complications continue to pose major challenges. Objectives: To describe anticoagulation modalities and bleeding events in adults receiving VV ECMO. Methods: This was an international prospective observational study in 41 centers, from December 2018 to February 2021. Anticoagulation was recorded daily in terms of type, dosage, and monitoring strategy. Bleeding events were reported according to site, severity, and impact on mortality. Measurements and Main Results: The study cohort included 652 patients, and 8,471 days on ECMO were analyzed. Unfractionated heparin was the initial anticoagulant in 77% of patients, and the most frequently used anticoagulant during the ECMO course (6,221 d; 73%). Activated partial thromboplastin time (aPTT) was the most common test for monitoring coagulation (86% of days): the median value was 52 seconds (interquartile range, 39 to 61 s) but dropped by 5.3 seconds after the first bleeding event (95% confidence interval, -7.4 to -3.2; P < 0.01). Bleeding occurred on 1,202 days (16.5%). Overall, 342 patients (52.5%) experienced at least one bleeding event (one episode every 215 h on ECMO), of which 10 (1.6%) were fatal. In a multiple penalized Cox proportional hazard model, higher aPTT was a potentially modifiable risk factor for the first episode of bleeding (for 20-s increase; hazard ratio, 1.07). Conclusions: Anticoagulation during VV ECMO was a dynamic process, with frequent stopping in cases of bleeding and restart according to the clinical picture. Future studies might explore lower aPTT targets to reduce the risk of bleeding.

The History of Extracorporeal Membrane Oxygenation and the Development of Extracorporeal Membrane Oxygenation Anticoagulation

Extracorporeal membrane oxygenation (ECMO) was first started for humans in early 1970s by Robert Bartlett. Since its inception, there have been numerous challenges with extracorporeal circulation, such as coagulation and platelet activation, followed by consumption of coagulation factors and platelets, and biocompatibility of tubing, pump, and oxygenator. Unfractionated heparin (heparin hereafter) has historically been the defacto anticoagulant until recently. Also, coagulation monitoring was mainly based on bedside activated clotting time and activated partial thromboplastin time. In the past 50 years, the technology of ECMO has advanced tremendously, and thus, the survival rate has improved significantly. The indication for ECMO has also expanded. Among these are clinical conditions such as postcardiopulmonary bypass, sepsis, ECMO cardiopulmonary resuscitation, and even severe coronavirus disease 2019 (COVID-19). Not surprisingly, the number of ECMO cases has increased according to the Extracorporeal Life Support Organization Registry and prolonged ECMO support has become more prevalent. It is not uncommon for patients with COVID-19 to be on ECMO support for more than 1 year until recovery or lung transplant. With that being said, complications of bleeding, thrombosis, clot formation in the circuit, and intravascular hemolysis still remain and continue to be major challenges. Here, several clinical ECMO experts, including the "Father of ECMO"-Dr. Robert Bartlett, describe the history and advances of ECMO.

High-Risk Pulmonary Embolism: Management for the Intensivist

High-risk pulmonary embolism (PE) also known as massive PE carries a high rate of morbidity and mortality. The incidence of high-risk PE continues to increase, yet the outcomes of high-risk PE continue to remain poor. Patients with high-risk PE are often critically ill, with complex underlying physiology, and treatment for the high-risk PE patient almost always requires care and management from an intensivist. Treatment options for high-risk PE continue to evolve rapidly with multiple options for definitive reperfusion therapy and supportive care. A thorough understanding of the physiology, risk stratification, treatment, and support options for the high-risk PE patient is necessary for all intensivists in order to improve outcomes. This article aims to provide a review from an intensivist's perspective highlighting the physiological consequences, risk stratification, and treatment options for these patients as well as providing a proposed algorithm to the risk stratification and acute management of high-risk PE.

Nursing care for children with fulminant myocarditis treated with extracorporeal membrane oxygenation

To summarize the nursing experience of treating pediatric fulminant myocarditis with extracorporeal membrane oxygenation (ECMO). The intensive care unit of our hospital treated 6 children with fulminant myocarditis with ECMO from 2019 to 2022. The main nursing measures included establishing an ECMO rescue team, preparing before initiation of ECMO, management of arterial and venous catheters, enteral nutrition support, reducing the risk of infection aggravation, anticoagulation management, prevention of bleeding and thrombosis, management of ECMO pump failure, and post-ECMO care. One child's family abandoned treatment and left the hospital, while the other 5 children were transferred to the cardiovascular department after stable weaning from ECMO and continued treatment, with good condition, and eventually discharged. Pediatric fulminant myocarditis has a high mortality rate, but detailed evaluation and nursing care can improve the outcome of these patients.

Subtypes and Mechanistic Advances of Extracorporeal Membrane Oxygenation-Related Acute Brain Injury

Extracorporeal membrane oxygenation (ECMO) is a frequently used mechanical cardiopulmonary support for rescuing critically ill patients for whom conventional medical therapies have failed. However, ECMO is associated with several complications, such as acute kidney injury, hemorrhage, thromboembolism, and acute brain injury (ABI). Among these, ABI, particularly intracranial hemorrhage (ICH) and infarction, is recognized as the primary cause of mortality during ECMO support. Furthermore, survivors often suffer significant long-term morbidities, including neurocognitive impairments, motor disturbances, and behavioral problems. This review provides a comprehensive overview of the different subtypes of ECMO-related ABI and the updated advance mechanisms, which could be helpful for the early diagnosis and potential neuromonitoring of ECMO-related ABI.

Risk factors for cannula-associated arterial thrombosis following extracorporeal membrane oxygenation support: a retrospective study

BACKGROUND

Hemostatic dysfunction during extracorporeal membrane oxygenation (ECMO) due to blood-circuit interaction and the consequences of shear stress imposed by flow rates lead to rapid coagulation cascade and thrombus formation in the ECMO system and blood vessels. We aimed to identify the incidence and risk factors for cannula-associated arterial thrombosis (CaAT) post-decannulation.

METHODS

A retrospective study of patients undergoing arterial cannula removal following ECMO was performed. We evaluated the incidence of CaAT and compared the characteristics, ECMO machine parameters, cannula sizes, number of blood products transfused during ECMO, and daily hemostasis parameters in patients with and without CaAT. Multivariate analysis identified the risk factors for CaAT.

RESULTS

Forty-seven patients requiring venoarterial ECMO (VA-ECMO) or hybrid methods were recruited for thrombosis screening. The median Sequential Organ Failure Assessment score was 11 (interquartile range, 8-13). CaAT occurred in 29 patients (61.7%), with thrombosis in the superficial femoral artery accounting for 51.7% of cases. The rate of limb ischemia complications in the CaAT group was 17.2%. Multivariate analysis determined that the ECMO flow rate-body surface area (BSA) ratio (100 ml/min/m2) was an independent factor for CaAT, with an odds ratio of 0.79 (95% confidence interval, 0.66-0.95; P=0.014).

CONCLUSIONS

We found that the incidence of CaAT was 61.7% following successful decannulation from VA-ECMO or hybrid modes, and the ECMO flow rate-BSA ratio was an independent risk factor for CaAT. We suggest screening for arterial thrombosis following VA-ECMO, and further research is needed to determine the risks and benefits of such screening.

Circuit change during extracorporeal membrane oxygenation: single-center retrospective study of 48 changes

BACKGROUND

Bleeding and thrombosis induce major morbidity and mortality in patients under extracorporeal membrane oxygenator (ECMO). Circuit changes can be performed for oxygenation membrane thrombosis but are not recommended for bleeding under ECMO. The objective of this study was to evaluate the course of clinical, laboratory, and transfusion parameters before and after ECMO circuit changes warranted by bleeding or thrombosis.

METHODS

In this single-center, retrospective, cohort study, clinical parameters (bleeding syndrome, hemostatic procedures, oxygenation parameters, transfusion) and laboratory parameters (platelet count, hemoglobin, fibrinogen, PaO₂) were collected over the seven days surrounding the circuit change.

RESULTS

In the 274 patients on ECMO from January 2017 to August 2020, 48 circuit changes were performed in 44 patients, including 32 for bleeding and 16 for thrombosis. Mortality was similar in the patients with vs. without changes (21/44, 48% vs. 100/230, 43%) and in those with bleeding vs. thrombosis (12/28, 43% vs. 9/16, 56%, P = 0.39). In patients with bleeding, numbers of bleeding events, hemostatic procedures, and red blood cell transfusions were significantly higher before vs. after the change (P < 0.001); the platelet counts and fibrinogen levels decreased progressively before and increased significantly after the change. In patients with thrombosis, numbers of bleeding events and red blood cell transfusions did not change after membrane change. No significant differences were demonstrated between oxygenation parameters (ventilator FiO₂, ECMO FiO₂, and PaO₂) and ECMO flow before vs. after the change.

CONCLUSIONS

In patients with severe and persistent bleeding, changing the ECMO circuit decreased clinical bleeding and red blood cell transfusion needs and increased platelets and fibrinogen levels. Oxygenation parameters did not change significantly in the group with thrombosis.

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.

Haematological Trends and Transfusion during Adult Extracorporeal Membrane Oxygenation: A Single Centre Study

The temporal trends in haematological parameters and their associations with blood product transfusion requirements in patients supported with extracorporeal membrane oxygenation (ECMO) are poorly understood. We performed a retrospective data analysis to better understand the behaviour of haematological and coagulation parameters and their associations with transfusion requirements during ECMO.

METHODS

Patient demographics, haematological and coagulation parameters, plasma haemoglobin and fibrinogen concentrations, platelet count, the international normalised ratio (INR), the activated partial thromboplastin time (APTT), and blood product transfusion data from 138 patients who received ECMO in a single high-volume centre were analysed.

RESULTS

Ninety-two patients received venoarterial (VA) ECMO and 46 patients received venovenous (VV) ECMO. The median (IQR) duration of VA, and VV ECMO was 8 (5-13) days and 13 (8-23) days, respectively. There were significant reductions in haemoglobin, the platelet count, and the fibrinogen concentration upon initiation of ECMO. On average, over time, patients on VV ECMO had platelet counts 44 × 109/L higher than those on VA ECMO (p ≤ 0.001). Fibrinogen and APTT did not vary significantly based on the mode of ECMO (p = 0.55 and p = 0.072, respectively). A platelet count < 50 × 109/L or a fibrinogen level < 1.8 g/L was associated with 50% chance of PRBC transfusion, regardless of the ECMO type, and packed red blood cell (PRBC) transfusion was more common with VA ECMO. APTT was predictive of the transfusion requirement, and the decrement in APTT was discriminatory between VVECMO survivors and nonsurvivors.

CONCLUSION

ECMO support is associated with reductions in haemoglobin, platelet count, and fibrinogen. Patients supported with VA ECMO are more likely to receive a PRBC transfusion compared to those on VV ECMO. Thrombocytopaenia, hypofibrinogenaemia, and anticoagulation effect the likelihood of requiring PRBC transfusion. Further research is needed to define optimal blood management during ECMO, including appropriate transfusion triggers and the anticoagulation intensity.

Prevalence of hematologic complications on extracorporeal membranous oxygenation in critically ill pediatric patients: A systematic review and meta-analysis

OBJECTIVES

Despite advances in Extracorporeal Membranous Oxygenation (ECMO) equipment, hematologic complications remain significant in critically ill children. The aim of this study is to summarize prevalence of hematologic complications for children and neonates.

METHODS

MEDLINE, PubMed and Scopus databases were searched focusing on the period from January 01, 2017 to October 01, 2022. The population included critically ill children and neonates with hematologic complications. The review included all aspects of related complications including hemorrhage, thrombosis, and hemolysis. We performed random effects meta-analyses. The primary outcome measure was overall hematologic complications. Secondary outcomes are changes in the prevalence of hemorrhagic complications. Risk of bias of included studies was assessed using the Joanna Briggs Institute checklist.

RESULTS

The systematic search identified 37 studies totaling 10,659 critically ill pediatric patients receiving ECMO. The pooled prevalence of hemorrhagic complications, thrombotic complications and hemolysis among pediatric patients requiring ECMO was 43.7 % (95 % CI: 28.6 % to 58.9 %, P < 0.001), 27.6 % (95 % CI: 20.4 % to 34.8 %, P < 0.001), 34.3 % (95 % CI: 22.9 % to 45.7 %, P < 0.001). The prevalence of hemorrhagic complications was represented in descending order: surgical site (21.6 %, 95 % CI: 10.3 % to 32.9 %); cannulation site (20.6 %, 95 % CI: 11.8 % to 29.3 %); intracranial (12.2 %, 95 % CI: 9.5 % to 15.0 %); pulmonary (7.7 %, 95 % CI: 5.9 % to 9.6 %); gastrointestinal (6.0 %, 3.7 % to 8.4 %). For the assessment of thrombotic complications, thrombosis in cannulation site had a higher prevalence (28.5 %, 95 % CI: 22.1 % to 34.9 %), followed by DIC (13.5 %, 95 % CI: 8.7 % to 18.3 %) and intracranial thrombosis (4.5 %, 95 % CI: 1.4 % to 7.6 %). Predictors of increased prevalence of hemorrhagic complications included age (P = 0.017) and VV-ECMO support mode (P = 0.029).

CONCLUSIONS

Among critically ill pediatric patients, there was a series of hematologic complications can occur during ECMO support. Physicians should pay special attention to the management and establish appropriate treatment programs to reduce the occurrence of hematologic complications.

Numerical and experimental investigation of a lighthouse tip drainage cannula used in extracorporeal membrane oxygenation

BACKGROUND

Extracorporeal membrane oxygenation is a life-saving therapy used in case of acute respiratory/circulatory failure. Exposure of blood to non-physiological surfaces and high shear stresses is related to hemolytic damage and platelet activation. A detailed knowledge of the fluid dynamics of the components under different scenarios is thus paramount to assess the thrombogenicity of the circuit.

METHODS

An investigation of the flow structures developing in a conventional lighthouse tip (single-staged) drainage cannula was performed with cross-validated computational fluid dynamics and particle image velocimetry. The aim was to quantify the variation in drainage performance and stress levels induced by different fluid models, hematocrit and vessel-to-cannula flow rate ratios.

RESULTS

The results showed that the 90° bends of the flow through the side holes created a recirculation zone inside the cannula which increased residence time. Flow structures resembling a jet in a crossflow were also observed. The use of different hematocrits did not significantly affect drainage performances. The most proximal set of holes drained the largest fraction of fluid. However, different flow rate ratios altered the flow rate drained through the tip. The use of 2D data led to a 50% underestimation of shear rate levels. In the drainage zone the non-Newtonian behavior of blood was less relevant.

CONCLUSIONS

The most proximal holes drained the largest amount of fluid. The flow features and distribution of flow rates among the holes showed little dependence on the hematocrit. The non-Newtonian behavior of blood had a small influence on the dynamics of the flow.

Anticoagulation in adult patients supported with extracorporeal membrane oxygenation: guidance from the Scientific and Standardization Committees on Perioperative and Critical Care Haemostasis and Thrombosis of the International Society on Thrombosis and Haemostasis

Anticoagulation of patients supported by extracorporeal membrane oxygenation is challenging because of a high risk of both bleeding and thrombotic complications, and often empirical. Practice in anticoagulation management is therefore highly variable. The scope of this guidance document is to provide clinicians with practical advice on the choice of an anticoagulant agent, dosing, and the optimal anticoagulant monitoring strategy during extracorporeal membrane oxygenation support in adult patients.

Thrombotic Events Develop in 1 Out of 5 Patients Receiving ECMO Support: An 11-Year Referral Centre Experience

BACKGROUND

The use of extracorporeal membrane oxygenation (ECMO) for critically ill patients is growing rapidly given recent developments in technology. However, adverse events are frequently reported that have potentially devastating impacts on patient outcomes. The information on predictors and risk factors for thrombotic events, especially that focusing on the comparison of veno-arterial and veno-venous ECMO configurations, are still inconsistent and sparse; therefore, we aimed to close this gap.

METHODS

We performed a retrospective analysis of all patients on extracorporeal life support admitted to the intensive care units of a tertiary university center in Europe.

RESULTS

From 645 patients, 417 who received extracorporeal life support due to cardiogenic shock (290, 70%), respiratory failure (116, 28%) or hypothermia (11, 3%) were included. In total, 22% (92) of the patients experienced thrombotic events with a similar incidence in both ECMO configurations. Anticoagulation consisted of unfractionated heparin (296, 71%) and argatroban (70, 17%). Univariate Cox analyses identified hemoconcentration and increased maximal clot firmness (thromboelastometry) as risk factors for thrombosis. Moreover, the patients experiencing thrombosis had longer ECMO duration and intensive care stays.

CONCLUSIONS

ECMO is a specialized life-support modality with a high risk of complications. A longer ECMO duration is associated with thrombosis occurrence in patients receiving ECMO support. Following hemorrhage, thromboembolic complications are common adverse events. However, in contrast to major bleeding, no impact on mortality was observed. The question arises if a protocol with less anticoagulation may have a role to play in the future.

Extracorporeal Cardiopulmonary Resuscitation: A Narrative Review and Establishment of a Sustainable Program

The rates of survival with functional recovery for out of hospital cardiac arrest remain unacceptably low. Extracorporeal cardiopulmonary resuscitation (ECPR) quickly resolves the low-flow state of conventional cardiopulmonary resuscitation (CCPR) providing valuable perfusion to end organs. Observational studies have shown an association with the use of ECPR and improved survivability. Two recent randomized controlled studies have demonstrated improved survival with functional neurologic recovery when compared to CCPR. Substantial resources and coordination amongst different specialties and departments are crucial for the successful implementation of ECPR. Standardized protocols, simulation based training, and constant communication are invaluable to the sustainability of a program. Currently there is no standardized protocol for the post-cannulation management of these ECPR patients and, ideally, upcoming studies should aim to evaluate these protocols.

ECMO Support in Refractory Cardiogenic Shock: Risk Factors for Mortality

BACKGROUND

Veno-arterial extracorporeal membrane oxygenation (va-ECMO) is a specialized temporary support for patients with refractory cardiogenic shock. The true value of this potentially lifesaving modality is still a subject of debate. Therefore, we aimed to investigate the overall in-hospital mortality and identify potential risk factors for mortality.

METHODS

We retrospectively analyzed the data of 453 patients supported with va-ECMO over a period of 14 years who were admitted to intensive care units of a tertiary university center in Austria.

RESULTS

We observed in-hospital mortality of 40% for patients with refractory cardiogenic shock. Hemorrhage, ECMO initiation on weekends, higher SAPS III score, and sepsis were identified as significant risk factors for mortality. Hemorrhage was the most common adverse event (46%), with major bleeding events dominating in deceased patients. Thromboembolic events occurred in 25% of patients, followed by sepsis (18%).

CONCLUSIONS

Although the rates of complications are substantial, a well-selected proportion of patients with refractory cardiogenic shock can be rescued from probable death. The reported risk factors could be used to increase the awareness of clinicians towards the development of new therapeutic concepts that may reduce their incidence.

Novel Coagulation Test Detects Anticoagulation Resistance and Is Associated With Thrombotic Events in Pediatric Patients Requiring Extracorporeal Membrane Oxygenation

Bivalirudin, an IV direct thrombin inhibitor, and unfractionated heparin (UFH) are frequently used anticoagulants in the pediatric critical care setting. An accurate, specific, point-of-care test to quantify and detect anticoagulation resistance is not currently available. This study evaluates the ability of a rapid (< 10 min), micro-volume (< 50 uL) coagulation test to detect and quantify the anticoagulation effect of bivalirudin and UFH using a functional, clot time endpoint in pediatric critical care patients.

DESIGN

Single-site retrospective laboratory sample analysis and chart review.

SETTING

A 105-bed pediatric and cardiac ICUs delivering extracorporeal membrane oxygenation.

SUBJECTS

Forty-one citrated, frozen, biobanked plasma specimens comprising 21 with bivalirudin and 20 with UFH from 15 anticoagulated pediatric patients were analyzed. Thirteen patients were on extracorporeal membrane oxygenation, one had a submassive pulmonary embolism, and one was on a left ventricular assist device.

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

A Clotting Time Score (CTS) was derived on each sample. The CTS detected patients that had developed a pathologic clotting event with 100% sensitivity and 82% specificity compared with prothrombin time with 25% sensitivity/76% specificity and activated partial thromboplastin time with 0% sensitivity/0% specificity. Additionally, the CTS detected subtherapeutic anticoagulation in response to UFH in patients that were clinically determined to be UFH resistant requiring alternative anticoagulation with bivalirudin.

CONCLUSIONS

The CTS appears to be a clinically valuable indicator of coagulation status in patients treated with either UFH or bivalirudin. Results outside of the therapeutic range due to inadequate dosing or anticoagulation resistance appeared to be associated with clot formation. CTS testing may reduce the risk of anticoagulation-related complications via the rapid identification of patients at high risk for pathologic thrombotic events.

Viscoelastic Testing in the Management of Adult Patients on Mechanical Circulatory Support Devices with Focus on Extracorporeal Membrane Oxygenation

Thromboembolic and hemorrhagic complications continue to remain frequent complications that significantly impact the morbidity and mortality of patients implanted with mechanical circulatory support devices (MCSDs). The severe acute respiratory syndrome caused by coronavirus 2 (SARS-CoV-2) has resulted in a number of COVID-19 patients being supported by MCSDs, specifically extracorporeal membrane oxygenation (ECMO), which in turn has created a crucial need for rapid assessment of hemostatic status in these patients to avoid bleeding and thrombotic complications. Currently, conventional plasma-based coagulation assays such as prothrombin time and activated partial thromboplastin time (aPTT) are used to assess hemostasis, and the activated clotting time (ACT) and aPTT are the most common tests used to monitor heparin anticoagulation in patients on ECMO. Unfractionated heparin remains the mainstay anticoagulation therapy for patients on ECMO. Extracorporeal Life Support Organization (ELSO) offers little guidance on the subject but does state that each institution should create its internal anticoagulation protocols. Viscoelastic assays (VEAs) are increasingly recognized by ELSO and ECMO community for their potential to assess hemostatic derangements in patients implanted with MCSDs as well as guidance for appropriate hemostatic therapy. This review focuses on the evidence for the use of viscoelastic assays to assess overall hemostasis and to guide the treatment of adult patients connected to an ECMO circuit. Limitations of the use of conventional assays, ACT, and VEA are also discussed.

Coagulation and Transfusion Updates From 2021

2021 and the COVID 19 pandemic have brought unprecedented blood shortages worldwide. These deficits have propelled national efforts to reduce blood usage, including limiting elective services and accelerating Patient Blood Management (PBM) initiatives. A host of research dedicated to blood usage and management within cardiac surgery has continued to emerge. The intent of this review is to highlight this past year's research pertaining to PBM and COVID-19-related coagulation changes.

Anticoagulation Strategies during Extracorporeal Membrane Oxygenation: A Narrative Review

The development of extracorporeal life support technology has added a new dimension to the care of critically ill patients who fail conventional treatment options. Extracorporeal membrane oxygenation (ECMO)—specialized temporary life support for patients with severe cardiac or pulmonary failure—plays a role in bridging the time for organ recovery, transplant, or permanent assistance. The overall patient outcome is dependent on the underlying disease, comorbidities, patient reaction to critical illness, and potential adverse events during ECMO. Moreover, the contact of the blood with the large artificial surface of an extracorporeal system circuit triggers complex inflammatory and coagulation responses. These processes may further lead to endothelial injury and disrupted microcirculation with consequent end-organ dysfunction and the development of adverse events like thromboembolism. Therefore, systemic anticoagulation is considered crucial to alleviate the risk of thrombosis and failure of ECMO circuit components. The gold standard and most used anticoagulant during extracorporeal life support is unfractionated heparin, with all its benefits and disadvantages. However, therapeutic anticoagulation of a critically ill patient carries the risk of clinically relevant bleeding with the potential for permanent injury or death. Similarly, thrombotic events may occur. Therefore, different anticoagulation strategies are employed, while the monitoring and the balance of procoagulant and anticoagulatory factors is of immense importance. This narrative review summarizes the most recent considerations on anticoagulation during ECMO support, with a special focus on anticoagulation monitoring and future directions.

Overt Disseminated Intravascular Coagulation with Severe Hypofibrinogenemia During Veno-Venous Extracorporeal Membrane Oxygenation

Disseminated intravascular coagulation (DIC) is a life-threatening hematologic derangement characterized by dysregulated thrombin generation and excessive fibrinolysis. However, DIC is poorly characterized in the extracorporeal membrane oxygenation (ECMO) population, and the underlying mechanisms are not well understood. Several mechanisms contribute to DIC in ECMO, including consumption of coagulation factors, acquired von Willebrand's syndrome leading to thrombocytopenia, and hyperfibrinolysis. There are few case reports of DIC in adult ECMO patients. Most are in the context of venoarterial ECMO, which is typically used in the setting of cardiogenic shock and cardiac arrest. These disease states themselves are known to be associated with DIC, liver failure, impaired anticoagulant mechanisms, and increased fibrinolysis. We present an unusual case of a 74-year-old man who developed overt DIC during veno-venous (VV) ECMO. DIC resulted in clinical bleeding and severe hypofibrinogenemia requiring massive cryoprecipitate transfusion of 87 pooled units. When the patient was decannulated from ECMO, his platelet count and fibrinogen concentration improved within 24 hours, suggesting that ECMO was a proximate cause of his DIC.

Extracorporeal cardiopulmonary resuscitation in adults: evidence and implications

Rates of survival with functional recovery for both in-hospital and out-of-hospital cardiac arrest are notably low. Extracorporeal cardiopulmonary resuscitation (ECPR) is emerging as a modality to improve prognosis by augmenting perfusion to vital end-organs by utilizing extracorporeal membrane oxygenation (ECMO) during conventional CPR and stabilizing the patient for interventions aimed at reversing the aetiology of the arrest. Implementing this emergent procedure requires a substantial investment in resources, and even the most successful ECPR programs may nonetheless burden healthcare systems, clinicians, patients, and their families with unsalvageable patients supported by extracorporeal devices. Non-randomized and observational studies have repeatedly shown an association between ECPR and improved survival, versus conventional CPR, for in-hospital cardiac arrest in select patient populations. Recently, randomized controlled trials suggest benefit for ECPR over standard resuscitation, as well as the feasibility of performing such trials, in out-of-hospital cardiac arrest within highly coordinated healthcare delivery systems. Application of these data to clinical practice should be done cautiously, with outcomes likely to vary by the setting and system within which ECPR is initiated. ECPR introduces important ethical challenges, including whether it should be considered an extension of CPR, at what point it becomes sustained organ replacement therapy, and how to approach patients unable to recover or be bridged to heart replacement therapy. The economic impact of ECPR varies by health system, and has the potential to outstrip resources if used indiscriminately. Ideally, studies should include economic evaluations to inform health care systems about the cost-benefits of this therapy.