Thromboelastography clot strength profiles and effect of systemic anticoagulation in COVID-19 acute respiratory distress syndrome: a prospective, observational study

Correlation between heparin anti-Xa activity and thromboelastography in adult critically ill COVID-19 patients

STUDY OBJECTIVE

Severe coronavirus disease 2019 (COVID-19) increases the risk of thrombotic complications with unfractionated heparin (UFH) as a commonly used agent in managing venous thromboembolism (VTE). The optimal anticoagulation intensity and monitoring parameters in intensive care unit (ICU) COVID-19 patients remains controversial. The primary study aim was to evaluate the relationship between anti-Xa and thromboelastography (TEG) reaction (R) time in patients with severe COVID-19 receiving therapeutic UFH infusions.

DESIGN

Single-center, retrospective study conducted over a 15-month period (2020-2021).

SETTING

Academic medical center (Banner University Medical Center Phoenix).

PATIENTS

Adult patients with severe COVID-19 administered therapeutic UFH infusions with one or more corresponding TEG, and anti-Xa assessments drawn within ≤2 hours of each other were included. The primary end point was the correlation between anti-Xa and TEG R time. Secondary aims were to describe the correlation between activated partial thromboplastin time (aPTT) and TEG R time, as well as clinical outcomes. Pearson's coefficient was used to evaluate the correlation using a kappa measure of agreement.

Viscoelastic Hemostatic Assays: A Primer on Legacy and New Generation Devices

Viscoelastic hemostatic assay (VHAs) are whole blood point-of-care tests that have become an essential method for assaying hemostatic competence in liver transplantation, cardiac surgery, and most recently, trauma surgery involving hemorrhagic shock. It has taken more than three-quarters of a century of research and clinical application for this technology to become mainstream in these three clinical areas. Within the last decade, the cup and pin legacy devices, such as thromboelastography (TEG^® 5000) and rotational thromboelastometry (ROTEM^® delta), have been supplanted not only by cartridge systems (TEG^® 6S and ROTEM^® sigma), but also by more portable point-of-care bedside testing iterations of these legacy devices (e.g., Sonoclot^®, Quantra^®, and ClotPro^®). Here, the legacy and new generation VHAs are compared on the basis of their unique hemostatic parameters that define contributions of coagulation factors, fibrinogen/fibrin, platelets, and clot lysis as related to the lifespan of a clot. In conclusion, we offer a brief discussion on the meteoric adoption of VHAs across the medical and surgical specialties to address COVID-19-associated coagulopathy.

Questions about COVID-19 associated coagulopathy: possible answers from the viscoelastic tests

Abnormal coagulation parameters are often observed in patients with coronavirus disease 2019 (COVID-19) and the severity of derangement has been associated with a poor prognosis. The COVID-19 associated coagulopathy (CAC) displays unique features that include a high risk of developing thromboembolic complications. Viscoelastic tests (VETs), such as thromboelastometry (ROTEM), thromboelastography (TEG) and Quantra Hemostasis Analyzer (Quantra), provide "dynamic" data on clot formation and dissolution; they are used in different critical care settings, both in hemorrhagic and in thrombotic conditions. In patients with severe COVID-19 infection VETs can supply to clinicians more information about the CAC, identifying the presence of hypercoagulable and hypofibrinolysis states. In the last year, many studies have proposed to explain the underlying characteristics of CAC; however, there remain many unanswered questions. We tried to address some of the important queries about CAC through VETs analysis.

Prevalence and Trajectory of COVID-19-Associated Hypercoagulability Using Serial Thromboelastography in a South African Population

Introduction

The coagulation abnormalities resulting from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been attributed to inflammation and subsequent cytokine storm. Thromboelastography (TEG) is a point-of-care test used to assess clot formation and degradation in whole blood and is an indicator of the overall real-time coagulopathic state of the patient.

Methods

A single-centre, prospective, observational cohort study was conducted in South Africa, analysing the coagulation patterns of 41 patients with hypoxia related to SARS-CoV-2 using serial thromboelastography (TEG) on admission, after 48 hours, and at resolution of hypoxia/day 10. Results: Two-thirds (n = 26) were women. The median age was 61 (IQR 50–67), and the majority (88%) were Black patients. Almost half (22) of the patients were critically ill and ventilated, with median SOFA and SAPS2 scores of 3 and 22 (IQR2-4 and 18–30), respectively. The prevalence of hypercoagulability was 0.54 (95% CI 0.46–0.62), whilst 29/41 (0.71, CI 0.64–0.78)) met the definition of hypofibrinolysis. Differences between the hypercoagulable (HC) and non-hypercoagulable groups remained apparent at 48 hours after anticoagulation. At this time point, the K time was significantly lower (p ˂ 0,01), and the α-angle (p ˂ 0,01) and maximum amplitude (MA) (p ˂ 0,01) were significantly higher in the HC cohort. At resolution of hypoxia, or day 10, only MA was significantly higher in the hypercoagulable group compared to the non-hypercoagulable group (p = 0.01). The initial impairment in fibrinolysis (Ly30), α angle, and MA were significantly associated with mortality, with p values of 0.006, 0.031, and 0.04, respectively.

Conclusions

In this South African population, hypercoagulability was a highly prevalent phenomenon in COVID-19 disease. It was typified by hypofibrinolysis and a persistently elevated MA, despite anticoagulation therapy.

The evolution of clot strength in critically-ill COVID-19 patients: a prospective observational thromboelastography study

BACKGROUND

Few studies detail the evolution of COVID-19 associated coagulopathy. We performed serial thromboelastography (TEG) and laboratory coagulation studies in 40 critically-ill, mechanically ventilated COVID-19 patients over a 14-day period and analysed differences between 30-day survivors and non-survivors.

METHODS

Single-center prospective, observational study including 40 patients with severe COVID-19 pneumonia admitted to the intensive care unit (ICU) for mechanical ventilation. TEG analysis was performed on days 1, 7 and 14 of ICU admission and laboratory coagulation studies were performed on days 1 and 14. Coagulation variables were evaluated for change over the 14-day observation period. Differences between survivors and non-survivors at 30-days were analysed and compared.

RESULTS

On admission, TEG maximum amplitude (MA) with heparinase correction was above the upper limit of the reference range in 32 (80%) patients while 33 (82.5%) presented with absent clot lysis at 30 min. The functional fibrinogen MA was also elevated above the upper limit of the reference range in 37 (92.5%) patients. All patients had elevated D-dimer and fibrinogen levels, mildly prolonged prothrombin times (PT), normal platelet counts and normal activated partial thromboplastin times (aPTT). The heparinase MA decreased significantly with time and normalised after 14 days (p = < 0.001) while the increased fibrin contribution to clot strength persisted with time (p = 0.113). No significant differences in TEG analysis were noted between 30-day survivors and non-survivors at all time points. No patients developed disseminated intravascular coagulopathy (DIC) after 14-days, however thrombosis and bleeding were each reported in 3 (7.5%) patients.

CONCLUSION

Critically-ill patients with COVID-19 present in a hypercoagulable state characterised by an increased clot strength. This state normalises after 14 days despite a persistently increased fibrin contribution to clot strength. We were unable to demonstrate any significant differences in TEG parameters between 30-day survivors and non-survivors at all time points.

Recurrent Hepatic Artery Thrombosis Following Living Donor Liver Transplant as Sequelae of SARS-CoV-2 Infection-a Case Report

As the second wave of COVID-19 disease is gripping the globe, liver transplant centers are increasingly receiving patients recovered from SARS-CoV-2 infection in recent few weeks. Unexpected complications in these patients are increasingly being recognized. We performed liver transplantation on a 51-year-old gentleman with decompensated liver disease 23 days after recovering from a mild SARS-CoV-2 infection. Surprisingly, despite massive blood loss and a prolonged anhepatic phase, his thromboelastographic (TEG) parameters persistently revealed hypercoagulability. After a brief uneventful early post-operative period, he developed hepatic arterial thrombosis on the 14th post-operative day, and again after 4 days, both of which required surgical intervention. Following discharge, the artery was thrombosed again which was only picked up when he developed a cholangiolar abscess, leading to graft loss necessitating re-transplantation. There is a lot of evidence suggesting that patients with SARS-CoV-2 infection tend to be hypercoagulable. We believe that this hypercoagulability might have played a significant role in the development of hepatic arterial thrombosis and eventual graft loss in this patient. This highlights the importance of revisiting anticoagulation protocols in liver transplant recipients recovered from COVID-19 and base them on TEG rather than routine parameters such as INR and APTT, which are routinely deranged in such patients.

Viscoelastometric Testing to Assess Hemostasis of COVID-19: A Systematic Review

Infection by SARS-CoV-2 is associated with a high risk of thrombosis. The laboratory documentation of hypercoagulability and impaired fibrinolysis remains a challenge. Our aim was to assess the potential usefulness of viscoelastometric testing (VET) to predict thrombotic events in COVID-19 patients according to the literature. We also (i) analyzed the impact of anticoagulation and the methods used to neutralize heparin, (ii) analyzed whether maximal clot mechanical strength brings more information than Clauss fibrinogen, and (iii) critically scrutinized the diagnosis of hypofibrinolysis. We performed a systematic search in PubMed and Scopus databases until 31st December 2020. VET methods and parameters, and patients' features and outcomes were extracted. VET was performed for 1063 patients (893 intensive care unit (ICU) and 170 non-ICU, 44 studies). There was extensive heterogeneity concerning study design, VET device used (ROTEM, TEG, Quantra and ClotPro) and reagents (with non-systematic use of heparin neutralization), timing of assay, and definition of hypercoagulable state. Notably, only 4 out of 25 studies using ROTEM reported data with heparinase (HEPTEM). The common findings were increased clot mechanical strength mainly due to excessive fibrinogen component and impaired to absent fibrinolysis, more conspicuous in the presence of an added plasminogen activator. Only 4 studies out of the 16 that addressed the point found an association of VETs with thrombotic events. So-called functional fibrinogen assessed by VETs showed a variable correlation with Clauss fibrinogen. Abnormal VET pattern, often evidenced despite standard prophylactic anticoagulation, tended to normalize after increased dosing. VET studies reported heterogeneity, and small sample sizes do not support an association between the poorly defined prothrombotic phenotype of COVID-19 and thrombotic events.