ROTEM Testing for Direct Oral Anticoagulants

[Update on point-of-care-based coagulation treatment : Systems, reagents, device-specific treatment algorithms]

Viscoelastic test (VET) procedures suitable for point-of-care (POC) testing are in widespread clinical use. Due to the expanded range of available devices and in particular due to the development of new test approaches and methods, the authors believe that an update of the current treatment algorithms is necessary. The aim of this article is to provide an overview of the currently available VET devices and the associated reagents. In addition, two treatment algorithms for the VET devices most commonly used in German-speaking countries are presented.

Challenges to Laboratory Monitoring of Direct Oral Anticoagulants

Direct oral anticoagulants (DOACs) exert anticoagulation effect by directly inhibiting Factor Xa (rivaroxaban, apixaban, and edoxaban) or thrombin (dabigatran). Though DOACs are characterized by fixed-dose prescribing and generally do not require routine laboratory drug-level monitoring (DLM), circumstances may arise where the DLM may aid in clinical decision-making, including DOAC dose adjustment, anticoagulant class change, or decisions to withhold or administer reversal agents. We review the current literature that describes high-risk patient groups in which DLM may be beneficial for improved patient anticoagulation management and stewardship. The review also summarizes the limitations of conventional coagulation testing and discuss the emerging utility of quantitative methods for routine and rapid emergent evaluation of DOAC drug levels-in particular, the Anti-Xa activity to detect Factor Xa Inhibitors (rivaroxaban, apixaban, and edoxaban). Both technical and regulatory barriers to widespread DLM implementation are limiting factors to further clinical research that must be overcome, in order to propose universal DOAC DLM strategies and provide clinical-laboratory correlation to formally classify high-risk patient groups.

Multichannel resonant acoustic rheometry system for quantification of coagulation of multiple human plasma samples

Resonant Acoustic Rheometry (RAR), a newly developed ultrasound-based technique for non-contact characterization of soft viscoelastic materials, has shown promise for quantitative viscoelastic assessment of temporally changing soft biomaterials in real time, and may be used to monitor blood coagulation process. Here, we report the development of a novel, multichannel RAR (mRAR) system for simultaneous measurements of multiple temporally evolving samples and demonstration of its use for monitoring the coagulation of multiple small-volume plasma samples. The mRAR system was constructed using an array of 4 custom-designed ultrasound transducers at 5.0 MHz and a novel electronic driving system that controlled the generation of synchronized ultrasound pulses for real time assessment of multiple samples simultaneously. As a proof-of-concept of the operation of the mRAR system, we performed tests using pooled normal human plasma samples and anti-coagulated plasma samples from patients treated with warfarin with a range of International Normalized Ratio (INR) values as well-characterized samples with different coagulation kinetics. Our results show that simultaneous tracking of dynamic changes in 4 plasma samples triggered by either kaolin or tissue factor was achieved for the entire duration of coagulation. The mRAR system captured distinct changes in the samples and identified parameters including the clotting start time and parameters associated with the stiffness of the final clots that were consistent with INR levels. Data from this study demonstrate the feasibility of the mRAR system for efficient characterization of the kinetic coagulation processes of multiple plasma samples.

Viscoelastic Testing Methods

Viscoelastic testing methods examine the real-time formation of a clot in a whole blood sample, and include thromboelastography (TEG), rotational thromboelastometry (ROTEM), and several other testing platforms. They allow for concurrent assessment of multiple aspects of clotting, including plasmatic coagulation factors, platelets, fibrinogen, and the fibrinolytic pathway. This testing is rapid and may be performed at the point-of-care, allowing for prompt identification of coagulopathies to guide focused and rational administration of blood products as well as the identification of anticoagulant effect. With recent industry progression towards user-friendly, cartridge-based, portable instruments, viscoelastic testing has emerged in the 21st century as a powerful tool to guide blood transfusions in the bleeding patient, and to identify and treat both bleeding and thrombotic conditions in many operative settings, including trauma surgery, liver transplant surgery, cardiac surgery, and obstetrics. In these settings, the use of transfusion algorithms guided by viscoelastic testing data has resulted in widespread improvements in patient blood management as well as modest improvements in select patient outcomes. To address the increasingly wide adoption of viscoelastic methods and the growing number of medical and laboratory personnel tasked with implementing, performing, and interpreting these methods, this chapter provides an overview of the history, physiology, and technology behind viscoelastic testing, as well as a practical review of its clinical utility and current evidence supporting its use. Also included is a review of testing limitations and the contextual role played by viscoelastic methods among all coagulation laboratory testing.

Evaluation of Direct Oral Anticoagulant Reversal Agents in Intracranial Hemorrhage: A Systematic Review and Meta-analysis

IMPORTANCE

Direct oral anticoagulant (DOAC)-associated intracranial hemorrhage (ICH) has high morbidity and mortality. The safety and outcome data of DOAC reversal agents in ICH are limited.

OBJECTIVE

To evaluate the safety and outcomes of DOAC reversal agents among patients with ICH.

DATA SOURCES

PubMed, MEDLINE, The Cochrane Library, Embase, EBSCO, Web of Science, and CINAHL databases were searched from inception through April 29, 2022.

STUDY SELECTION

The eligibility criteria were (1) adult patients (age ≥18 years) with ICH receiving treatment with a DOAC, (2) reversal of DOAC, and (3) reported safety and anticoagulation reversal outcomes. All nonhuman studies and case reports, studies evaluating patients with ischemic stroke requiring anticoagulation reversal or different dosing regimens of DOAC reversal agents, and mixed study groups with DOAC and warfarin were excluded.

DATA EXTRACTION AND SYNTHESIS

Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines were used for abstracting data and assessing data quality and validity. Two reviewers independently selected the studies and abstracted data. Data were pooled using the random-effects model.

MAIN OUTCOMES AND MEASURES

The primary outcome was proportion with anticoagulation reversed. The primary safety end points were all-cause mortality and thromboembolic events after the reversal agent.

RESULTS

A total of 36 studies met criteria for inclusion, with a total of 1832 patients (967 receiving 4-factor prothrombin complex concentrate [4F-PCC]; 525, andexanet alfa [AA]; 340, idarucizumab). The mean age was 76 (range, 68-83) years, and 57% were men. For 4F-PCC, anticoagulation reversal was 77% (95% CI, 72%-82%; I2 = 55%); all-cause mortality, 26% (95% CI, 20%-32%; I2 = 68%), and thromboembolic events, 8% (95% CI, 5%-12%; I2 = 41%). For AA, anticoagulation reversal was 75% (95% CI, 67%-81%; I2 = 48%); all-cause mortality, 24% (95% CI, 16%-34%; I2 = 73%), and thromboembolic events, 14% (95% CI, 10%-19%; I2 = 16%). Idarucizumab for reversal of dabigatran had an anticoagulation reversal rate of 82% (95% CI, 55%-95%; I2 = 41%), all-cause mortality, 11% (95% CI, 8%-15%, I2 = 0%), and thromboembolic events, 5% (95% CI, 3%-8%; I2 = 0%). A direct retrospective comparison of 4F-PCC and AA showed no differences in anticoagulation reversal, proportional mortality, or thromboembolic events.

CONCLUSIONS AND RELEVANCE

In the absence of randomized clinical comparison trials, the overall anticoagulation reversal, mortality, and thromboembolic event rates in this systematic review and meta-analysis appeared similar among available DOAC reversal agents for managing ICH. Cost, institutional formulary status, and availability may restrict reversal agent choice, particularly in small community hospitals.

Tailored Direct Oral Anticoagulation in Patients with Atrial Fibrillation: The Future of Oral Anticoagulation?

Direct oral anticoagulants (DOAC) are currently the drug of choice for drug prevention of stroke or systemic embolism in patients with atrial fibrillation (AF). However, repeated ischemic stroke or systemic embolism and bleeding while on DOAC is still a challenging clinical phenomenon in the management of future long-term anticoagulation. It is not known whether tailoring the DOAC therapy to achieve optimal therapeutic drug levels could improve the clinical course of DOAC therapy. To be able to tailor the therapy, it is necessary to have a valid laboratory method for DOAC level assessment, to be aware of factors influencing DOAC levels and to have clinical options to tailor the treatment. Furthermore, the data regarding clinical efficacy/safety of tailored DOAC regimes are still lacking. This article reviews the current data on tailored direct oral anticoagulation in patients with AF.

Rotational thromboelastometry in patients with type 2 diabetes and mild COVID-19 pneumonia: A pilot prospective study

BACKGROUND

It was repeatedly demonstrated that patients with severe COVID-19 pneumonia, as well as patients with type 2 diabetes (T2D) have higher risk of thromboembolic complications. Rotational thromboelastometry (ROTEM®) is a viscoelastic hemostatic assay which allows complex assessment of hemostasis in whole blood. The aim of this study was to compare changes in hemostasis measured by ROTEM® in diabetic and nondiabetic patients with mild COVID-19 pneumonia.

METHODS

We performed a pilot, prospective, observational study and enrolled 33 consecutive patients (14 with T2D and 19 nondiabetic ones) admitted to regular ward with mild COVID-19 pneumonia. The control group consisted from 11 healthy, nondiabetic blood donors. Blood samples were tested with ROTEM® using INTEM® and EXTEM® reagents.

RESULTS

We detected significant differences in EXTEM® clotting time (CT), clot formation time (CFT), and maximum clot firmness (MCF) comparing patients with mild COVID-19 pneumonia and healthy donors. However, there were no significant differences in EXTEM®, INTEM®, and HEPTEM® parameters (CT, CFT, and MCF) according to diabetes status.

CONCLUSIONS

Our study demonstrated hypercoagulation in patients with mild COVID-19 pneumonia. T2D did not affected ROTEM® parameters in patients with mild COVID-19 pneumonia.

Biological Variation in Rotational Thromboelastometry in Patients with Atrial Fibrillation Receiving Rivaroxaban

Rotational thromboelastometry (ROTEM) is a viscoelastic hemostasis test used primarily in the management of bleeding after trauma or in cardiac surgery. To allow safe and valid clinical interpretation of test results, objective specifications for analytical performance are needed, which are generally based on biological variation within (CVI) and between (CVG) individuals. The aim of this study was to evaluate biological variation in ROTEM in patients receiving rivaroxaban. Sixty patients with atrial fibrillation on stable rivaroxaban therapy were included, from whom blood was collected on six occasions: three times at trough and three at peak rivaroxaban concentrations. ROTEM® Extem and LowTF were measured as well as rivaroxaban concentration, PT, APTT, and anti-Xa. Within- (CVI) and between-subject (CVG) biological estimates were calculated. Knowledge of these biological variation components will help to establish the appropriate objective analytical performance specifications for ROTEM analysis.

The Composition and Physical Properties of Clots in COVID-19 Pathology

Hemostasis is a finely tuned process of which dysregulation can lead either to bleeding or thrombotic complications. The latter is often caused by the hypercoagulable state as it is also seen in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, i.e., in COVID-19 patients. COVID-19 patients requiring hospitalization often suffer from thrombotic events that could not be predicted using routine coagulation assays. Recently, several studies have reported ROtational ThromboElastoMetry (ROTEM) as a promising tool to predict outcomes in COVID-19 patients. In this review we give an overview of ROTEM with a particular focus on the interpretation of the symmetrical clot formation curve in relation to coagulopathy in COVID-19 patients. Furthermore, we have introduced new parameters that might help to better distinguish between COVID-19 patients and outcomes.