Effect of rivaroxaban on blood coagulation using the viscoelastic coagulation test ROTEM™

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.

The impact of direct oral anticoagulants on viscoelastic testing - A systematic review

BACKGROUND

In case of bleeding patients and in acute care, the assessment of residual direct oral anticoagulant (DOAC) activity is essential for evaluating the potential impact on hemostasis, especially when a timely decision on urgent surgery or intervention is required. Viscoelastic tests are crucial in a modern goal-directed coagulation management to assess patients' coagulation status. However, the role of viscoelastic test to detect and quantify residual DOAC plasma levels is controversially discussed. The aim of this review was to systematically summarize the evidence of viscoelastic tests for the assessment of residual DOAC activity.

METHOD

PubMed, Embase, Scopus, and the Cochrane Library were searched for original articles investigating the effect of rivaroxaban, apixaban, edoxaban, or dabigatran plasma levels on different viscoelastic tests of the adult population from database inception to December 31, 2021.

RESULTS

We included 53 studies from which 31 assessed rivaroxaban, 22 apixaban, six edoxaban, and 29 dabigatran. The performance of viscoelastic tests varied across DOACs and assays. DOAC specific assays are more sensitive than unspecific assays. The plasma concentration of rivaroxaban and dabigatran correlates strongly with the ROTEM EXTEM, ClotPro RVV-test or ECA-test clotting time (CT) and TEG 6s anti-factor Xa (AFXa) or direct thrombin inhibitor (DTI) channel reaction time (R). Results of clotting time (CT) and reaction time (R) within the normal range do not reliable exclude relevant residual DOAC plasma levels limiting the clinical utility of viscoelastic assays in this context.

CONCLUSION

Viscoelastic test assays can provide fast and essential point-of-care information regarding DOAC activity, especially DOAC specific assays. The identification and quantification of residual DOAC plasma concentration with DOAC unspecific viscoelastic assays are not sensitive enough, compared to recommended anti-Xa activity laboratory measurements.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=320629], identifier [CRD42022320629].

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.

In Vitro Apixaban Removal By CytoSorb Whole Blood Adsorber: An Experimental Study

OBJECTIVES

The use of unopposed oral anticoagulants while undergoing cardiothoracic surgery is associated with severe bleeding and increased morbidity. The aim of this experimental study was to examine if the apixaban concentration in reconstituted blood could be reduced in an in vitro setup by the use of CytoSorb whole blood adsorber, and to study how this affected global coagulation assays.

DESIGN AND SETTING

An experimental study performed in a laboratory.

PARTICIPANTS

An in vitro setup with reconstituted whole blood.

INTERVENTIONS

Reconstituted whole blood spiked with apixaban circulated in an in vitro circuit with the CytoSorb 300 mL device connected.

MEASUREMENTS AND MAIN RESULTS

Blood samples were drawn at 0, 5, 15, 30, 60, and 120 minutes of adsorption. The apixaban concentration was measured at each time point. In addition, the global coagulation assays, thromboelastometry clotting time and thrombin generation, were performed, and the results were compared with baseline values obtained before spiking blood with apixaban. After 30 minutes of adsorption, the mean apixaban concentration was reduced from 414.3 (±69.1) ng/mL to 33 (±11.4) ng/mL. Thrombin generation showed maximum effect after 60 minutes, and the thromboelastometry clotting time was close to baseline values after 120 minutes.

CONCLUSIONS

In this in vitro study, apixaban concentrations were effectively reduced, and the clotting time and thrombin generation assays were normalized by the use of CytoSorb whole blood adsorber.

"In Less than No Time": Feasibility of Rotational Thromboelastometry to Detect Anticoagulant Drugs Activity and to Guide Reversal Therapy

Anticoagulant drugs (i.e., unfractionated heparin, low-molecular-weight heparins, vitamin K antagonists, and direct oral anticoagulants) are widely employed in preventing and treating venous thromboembolism (VTE), in preventing arterial thromboembolism in nonvalvular atrial fibrillation (NVAF), and in treating acute coronary diseases early. In certain situations, such as bleeding, urgent invasive procedures, and surgical settings, the evaluation of anticoagulant levels and the monitoring of reversal therapy appear essential. Standard coagulation tests (i.e., activated partial thromboplastin time (aPTT) and prothrombin time (PT)) can be normal, and the turnaround time can be long. While the role of viscoelastic hemostatic assays (VHAs), such as rotational thromboelastometry (ROTEM), has successfully increased over the years in the management of bleeding and thrombotic complications, its usefulness in detecting anticoagulants and their reversal still appears unclear.

Rotational Thromboelastometry in High-Risk Patients on Dual Antithrombotic Therapy After Percutaneous Coronary Intervention

Aims: Patients using antithrombotic drugs after percutaneous coronary intervention (PCI) are at risk for bleeding and recurrent ischemia. We aimed to explore routine and tissue plasminogen activated (tPA) ROTEM results in a post-PCI population on dual antithrombotic treatment.

Methods and Results: In this prospective cohort, 440 patients treated with double antithrombotic therapy after recent PCI and with ≥3 risk factors for either ischemic or bleeding complications were included and compared with a control group (n = 95) consisting of perioperative patients not using antithrombotic medication. Laboratory assessment, including (tPA) ROTEM, was performed one month post-PCI and bleeding/ischemic complications were collected over a five-month follow-up. Patients were stratified by antithrombotic regimen consisting of a P2Y12 inhibitor with either aspirin (dual antiplatelet therapy; DAPT, n = 323), a vitamin K antagonist (VKA, n = 69) or a direct oral anticoagulant (DOAC, n = 48). All post-PCI patients had elevated ROTEM clot stiffness values, but only the DAPT group additionally presented with a decreased fibrinolytic potential as measured with tPA ROTEM. Patients receiving anticoagulants had prolonged clotting times (CT) when compared to the control and DAPT group; EXTEM and FIBTEM CT could best discriminate between patients (not) using anticoagulants (AUC > 0.97). Furthermore, EXTEM CT was significantly prolonged in DAPT patients with bleeding complications during follow-up (68 [62–70] vs. 62 [57–68], p = 0.030).

Conclusion: ROTEM CT has high potential for identifying anticoagulants and tPA ROTEM could detect a diminished fibrinolytic potential in patients using DAPT. Furthermore, the ability of EXTEM CT to identify patients at risk for bleeding may be promising and warrants further research.

ROTEM Testing for Direct Oral Anticoagulants

Direct oral anticoagulants (DOACs) are increasingly used worldwide for the prevention of stroke in patients with atrial fibrillation and to prevent or treat venous thromboembolism. In situations such as serious bleeding, the need for urgent surgery/intervention or the management of a thromboembolic event, the laboratory measurement of DOACs levels or anticoagulant activity may be required. Rotational thromboelastometry (ROTEM) is a viscoelastic hemostatic assay (VHA) which has been used in emergencies (trauma and obstetrics), and surgical procedures (cardiac surgery and liver transplants), but experience with this assay in DOACs-treated patients is still limited. This article reviews the use of ROTEM in the setting of DOACs therapy, focusing on DOACs-associated bleeding and the use of this VHA for the management of reversal strategies for DOACs-associated anticoagulation.

Investigation of the Optimal Dose aPCC in Reversing the Effect of Factor Xa Inhibitors-An In Vitro Study

Factor (F) Xa inhibitors are safe and effective alternatives to warfarin. There are concerns about the lack of a reversal strategy in case of serious bleeds or need for emergency surgery in situations when the antidote andexanet alfa is not available. Factor concentrates are widely used, but there are few clinical studies regarding the reversal effect of activated prothrombin complex concentrate (aPCC). Because of the feared thrombogenicity, administration of the lowest effective dose would be desirable. To determine the lowest concentration of aPCC sufficient to reverse the effect of rivaroxaban and apixaban. Blood from 18 healthy volunteers were supplemented with apixaban or rivaroxaban. aPCC was added to obtain 10 different concentrations ranging from 0.08-1.60 U/mL. Thromboelastometry and thrombin generation assay were used to assess the reversal effect. aPCC concentrations of 0.08 and 0.16 U/mL restored thromboelastometry clotting time to baseline in apixaban (P = 1.0) and rivaroxaban (P = 1.0)-containing samples, respectively. The concentrations 0.08 U/mL (P = 0.5) and 0.24 U/mL (P = 0.2) were sufficient to restore thrombin generation. Concentrations of 0.56 U/mL and higher, caused significantly higher ETP than baseline in apixaban-containing samples (P < 0.05). aPCC concentrations lower than previously reported were effective in reversing the effect of FXa inhibitors in vitro.

Real-time detection and differentiation of direct oral anticoagulants (rivaroxaban and dabigatran) using modified thromboelastometric reagents

INTRODUCTION

Timely measurement of direct oral anticoagulants (DOACs) is challenging, though clinically important. We tested the hypotheses, that thromboelastometry is able to detect dabigatran and rivaroxaban and discriminates between dabigatran and rivaroxaban as representatives of the two groups of DOACs.

METHODS AND MATERIALS

We conducted a prospective-observational study: In-vitro dose-effect-curves for rivaroxaban and dabigatran were performed (n = 10). Ex-vivo: Patients with indication of DOAC treatment (stroke; dabigatran/rivaroxaban) were included (n = 21). Blood samples were analyzed before first intake, at first estimated peak level and at 24 h after first but before following intake and 3 h after 24 h-intake. Standard and modified thromboelastometric-assays, using low tissue factor concentrations (TFTEM) or ecarin (ECATEM) were used. Receiver-operating-characteristics-curve-analysis (ROC), regression-analysis and two-way-ANOVA were performed.

RESULTS

In-vitro: TFTEM detected dabigatran and rivaroxaban (ROC_AUC: 0.99; sensitivity/specificity: 100%/98%) but could not discriminate. Dabigatran prolongs CT_ECATEM whereas rivaroxaban did not. Clotting Time (CT)-ratio TFTEM/ECATEM discriminated highly sensitive (100%) and specific (100%) between dabigatran and rivaroxaban even at very low concentrations (ROC_AUC:1.0). CT_ECATEM correlated with dabigatran spiked concentrations (r = 0.9985; p < 0.001) and CT_TFTEM (r = 0.9363; p = 0.006) with rivaroxaban. Similarly results could be demonstrated with patient data: We confirmed the performance for the differentiation of CT-ratio TFTEM/ECATEM (sensitivity 100%/specificity 100%) at any time after first intake of either DOAC.

CONCLUSION

The thromboelastometric tests TFTEM and ECATEM detect and differentiate rivaroxaban and dabigatran. Further investigations evaluate the other DOACs and the differentiation to phenprocoumon. However, results need to be confirmed in a larger study, and especially cut off values for differentiation need to be calculated from a larger sample size.

Correlation of Thromboelastography with Apparent Rivaroxaban Concentration: Has Point-of-Care Testing Improved?

BACKGROUND

Concern remains over reliable point-of-care testing to guide reversal of rivaroxaban, a commonly used factor Xa inhibitor, in high-acuity settings. Thromboelastography (TEG), a point-of-care viscoelastic assay, may have the ability to detect the anticoagulant effect of rivaroxaban. The authors ascertained the association of apparent rivaroxaban concentration with thromboelastography reaction time, i.e., time elapsed from blood sample placement in analyzer until beginning of clot formation, as measured using TEG and TEG6S instruments (Haemonetics Corporation, USA), hypothesizing that reaction time would correlate to degree of functional factor Xa impairment.

METHODS

The authors prospectively performed a diagnostic accuracy study comparing coagulation assays to apparent (i.e., indirectly assessed) rivaroxaban concentration in trauma patients with and without preinjury rivaroxaban presenting to a single center between April 2016 and July 2018. Blood samples at admission and after reversal or 24 h postadmission underwent TEG, TEG6S, thrombin generation assay, anti-factor Xa chromogenic assay, prothrombin time (PT), and ecarin chromogenic assay testing. The authors determined correlation of kaolin TEG, TEG6S, and prothrombin time to apparent rivaroxaban concentration. Receiver operating characteristic curve compared capacity to distinguish therapeutic rivaroxaban concentration (i.e., greater than or equal to 50 ng/ml) from nontherapeutic concentrations.

RESULTS

Eighty rivaroxaban patients were compared to 20 controls. Significant strong correlations existed between rivaroxaban concentration and TEG reaction time (ρ = 0.67; P < 0.001), TEG6S reaction time (ρ = 0.68; P < 0.001), and prothrombin time (ρ = 0.73; P < 0.001), however reaction time remained within the defined normal range for the assay. Rivaroxaban concentration demonstrated strong but not significant association with coagulation assays postreversal (n = 9; TEG reaction time ρ = 0.62; P = 0.101; TEG6S reaction time ρ = 0.57; P = 0.112) and small nonsignificant association for controls (TEG reaction time: ρ = -0.04; P = 0.845; TEG6S reaction time: ρ = -0.09; P = 0.667; PT-neoplastine: ρ = 0.19; P = 0.301). Rivaroxaban concentration (area under the curve, 0.91) and TEG6S reaction time (area under the curve, 0.84) best predicted therapeutic rivaroxaban concentration and exhibited similar receiver operating characteristic curves (P = 0.180).

CONCLUSIONS

Although TEG6S demonstrates significant strong correlation with rivaroxaban concentration, values within normal range limit clinical utility rendering rivaroxaban concentration the gold standard in measuring anticoagulant effect.

Measurements of endogenous thrombin potential using the CAT method in cats: Reference values and influence of the direct factor Xa inhibitor apixaban

The aim of this study was to establish a thrombin generation assay (calibrated automated thrombogram, CAT) in cats by determining the precision (repeatability), reference values, and the sensitivity to anticoagulant treatment with the factor Xa inhibitor apixaban. The CAT method was performed on citrated plasma with different commercial tissue factor (TF) reagents (PPP Reagent 1 pM [LOW], PPP Reagent 5 pM, PPP Reagent 20 pM [HIGH]) according to the manufacturers` test instruction. Measurements in triplicate were performed in platelet poor plasma (PPP) of 58 healthy cats and in 6 cats at different times following the oral administration of 2.5 mg apixaban. The median CVs in healthy cats usually were < 10% with the exception of thrombin peak height measured using PPP Reagent 1 pM (14.6%). Reference values of all parameters showed marked inter-individual variability and depended largely on the TF concentration of the used activating reagent. Thrombin generation was significantly influenced by apixaban and reacted more sensitively than other tests of haemostasis including the prothrombin time, aPTT, and rotational elastometry. In conclusion, thrombin generation measured by the CAT method using commercially available reagents seems suitable for the examination of feline PPP and may be a valuable method to establish effective anticoagulant therapies for the feline patient and monitoring of such therapies in cats.

In vitro effects of a kaolin-coated hemostatic dressing on anticoagulated blood

BACKGROUND

The use of kaolin-coated dressings has become common and have efficacy in normal patients, but their increased use will inevitably include use on bleeding patients taking anticoagulants. We hypothesize that kaolin coating material (KCM) will improve clotting regardless of anticoagulation medication.

METHODS

A prospective study was performed on blood from patients who were on a vitamin K antagonist (VKA), unfractionated heparin (UH), an antiplatelet (AP) agent, a Xa inhibitor (Xa), or a direct thrombin inhibitor (DTI). None were on more than one type of anticoagulation medication. Viscoelastic testing was performed with and without KCM. All p values were adjusted for multiple comparisons.

RESULTS

The addition of KCM significantly decreased the time for initial clot formation (CT) in all groups. The mean CT for controls was decreased from 692 to 190.8 s (p < 0.0001). KCM decreased the initial clot formation time by about 1.5 times in those on DTI (p = 0.043) and 2.5 times in those taking AP medication (p < 0.001). The most profound effect was seen in those on UH (no KCM 1,602 s vs. KCM 440 s; p < 0.001), VKA (no KCM 1,152 s vs. 232 s; p < 0.01), and Xa (no KCM 1,342 s vs. 287 s; p < 0.001). Analysis of other clot formation parameters revealed that KCM significantly improved the clot formation kinetics (CFT) only in patients taking Xa (p = 0.03). KCM improved maximum clot strength in patients on Xa inhibitors (p = 0.05). Patients on UH had a larger effect size with an increase in clot strength from 24.35 mm to 43.35 mm whereas those on Xa had an increase of 38.7 mm to 49.85 mm.

CONCLUSION

In this in vitro analysis, the addition of KCM to the blood of patients taking any of these anticoagulation medications significantly improved the time to initial clot formation, indicating that kaolin-based hemostatic dressings will be effective in initiating clot formation in patients on anticoagulants.

LEVEL OF EVIDENCE

Therapeutic, level IV.

Diagnostic accuracy of thromboelastometry and its correlation with the HPLC-MS/MS quantification test

The aim of the study was to evaluate the diagnostic accuracy of thromboelastometry for assessing rivaroxaban concentrations. The accuracy of thromboelastometry was compared with the high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method, which is the gold standard for drug plasma monitoring (the reference standard). Forty-six clinically stable patients were treated with 10, 15, or 20 mg of rivaroxaban once daily (OD group) or 15 mg twice a day (BID group) (no particular indication for treatment). Patient samples were collected 2 h after the use of the medication (peak) and 2 h before the next dose (trough). The rivaroxaban plasma concentrations were determined via HPLC-MS/MS, and thromboelastometry was performed using a ROTEM® delta analyzer. There were significant prolongations in clotting time (CT) for the 10, 15, and 20 mg of rivaroxaban treatments in the OD groups. In the 15 mg BID group, the responses at the peak and trough times were similar. At the peak times, there was a positive correlation between the plasma concentration of rivaroxaban and CT (Spearman correlation rho=0.788, P<0.001) and clot formation time (rho=0.784, P<0.001), and a negative correlation for alpha angle (rho=−0.771, P<0.001), amplitude after 5 min (rho=−0.763, P<0.001), and amplitude after 10 min (rho=−0.680, P<0.001). The CT presented higher specificity and sensitivity using the cut-off determined by the receiver characteristics curve. ROTEM has potential as screening tool to measure possible bleeding risk associated with rivaroxaban plasma levels.

Laboratory Assessment of the Anticoagulant Activity of Apixaban in Patients With Nonvalvular Atrial Fibrillation

Our aim is to determine the most appropriate laboratory tests, besides anti-factor Xa (anti-FXa) chromogenic assays, to estimate the degree of anticoagulation with apixaban and compare it with that of rivaroxaban in real-world patients. Twenty patients with nonvalvular atrial fibrillation treated with apixaban 5 mg twice daily and 20 patients on rivaroxaban 20 mg once daily were studied. Conventional coagulation tests, thrombin generation assay (TGA), and thromboelastometry (nonactivated TEM [NATEM] assay) were performed in the 40 patients and 20 controls. The anti-FXa chromogenic assays were used to measure apixaban and rivaroxaban plasma levels. The NATEM measurements showed no significant difference between the 2 groups of patients. Concerning TGA, endogenous thrombin potential (ETP) was significantly decreased in patients on rivaroxaban as compared to those treated with apixaban (P < .003). A statistically significant, strong inverse correlation between apixaban plasma concentrations and ETP (P < .001) was observed. Apixaban significantly reduces ETP compared to controls, but to a lesser extent than rivaroxaban. Thrombin generation assay might provide additional information on apixaban exposure, which is required in order to individualize treatment especially for patients with a high bleeding risk. Our findings have to be further investigated in studies with larger sample sizes, in the entire range of apixaban exposure, with other direct oral anticoagulants, and in relation to clinical outcomes.

Rapid determination of anticoagulating effects of dabigatran in whole blood with rotational thromboelastometry and a thrombin-based trigger

Essentials A rapid test to detect thrombin inhibition by dabigatran would be valuable in acute situations. A thrombin-based trigger was applied in whole blood using rotation thromboelastometry. Effects of dabigatran were assessed in vitro and in samples from patients on dabigatran. The test produced data rapidly and was sensitive to dabigatran concentrations from 20 to 500 ng mL-1 . SUMMARY: Background Rapid determination of the anticoagulant effect of dabigatran is essential in emergency situations. Objective To study a viscoelastic test (rotational thromboelastometry [ROTEM]) for rapid determination of dabigatran effects in whole blood samples. Method ROTEM measurements were performed with comparison of two triggers (thrombin-based versus the commercial tissue factor-based trigger Ex-tem) in samples from 10 healthy donors spiked with dabigatran (20-500 ng mL-1 ) and in samples from 35 patients receiving dabigatran treatment; 10 healthy subjects served as controls. Clotting time (CT) and the difference in CT without versus with addition of the dabigatran antidote idarucizumab (CTdiff ) were measured. Addition of idarucizumab reveals the contribution of dabigatran to ROTEM measurements and its potential reversibility. Results In vitro studies showed that thrombin CT and thrombin CTdiff were more sensitive than Ex-tem CT and Ex-tem CTdiff in detecting dabigatran in whole blood samples. In patient samples, when thrombin CT and thrombin CTdiff were used, it was possible to detect dabigatran with a cut-off of dabigatran at 20 ng mL-1 , whereas, when Ex-tem CT and Ex-tem CTdiff were used, the method was less sensitive. Data from patient samples were obtained within 15 min of blood sampling. Conclusions ROTEM CT with a thrombin-based trigger is more sensitive to dabigatran effects than Ex-tem CT, and detects anticoagulant effects of drug concentrations in the low-very low therapeutic range. Analysis with idarucizumab (CTdiff ) reveals dabigatran-specific effects. As data are rapidly obtained, this method could, with further development and validation of its performance, be suitable for detecting clinically significant dabigatran effects in emergency situations.

Differential Assessment of Factor Xa Activity and Global Blood Coagulability Utilizing Novel Dielectric Coagulometry

An easy-to-use assessment for activated factor X (FXa) is lacking despite its pivotal role in the coagulation. Dielectric blood coagulometry (DBCM) was recently invented as a novel assessment tool for determining the whole blood coagulability by measuring the temporal change in the permittivity of blood. We previously reported that it could evaluate the global blood coagulability. This study aimed to apply the DBCM for assessing FXa activity and its inhibition by anticoagulants. We performed the DBCM analysis along with measurement of the FXa activity by a fluorometric assay in samples from healthy subjects, and identified a new index named maximum acceleration time (MAT) that had a correlation to the FXa activity. Next the DBCM analysis was performed using blood samples mixed with anticoagulants (unfractionated heparin, dalteparin, and edoxaban). Blood samples with three anticoagulants had different profiles of the temporal change in the permittivity, reflecting their different selectivity for FXa. We compared the MAT with the anti-FXa activity assay, and found that the prolongation of MAT was similarly correlated with the anti-FXa activity regardless of the type of anticoagulants. In conclusion, the DBCM has the possibility for evaluating the innate FXa activity and effect of anticoagulants focusing on their FXa inhibition.

Role of Thromboelastography and Rotational Thromboelastometry in the Management of Cardiovascular Diseases

The monitoring of coagulation by viscoelastometric methods—thromboelastography and rotational thromboelastometry—may detect the contributions of cellular and plasma components of hemostasis. These methods might overcome some of the serious limitations of conventional laboratory tests. Viscoelastic testing can be repeatedly performed during and after surgery and thus provides a dynamic picture of the coagulation process during these periods. Several experiences with the use of these methods in cardiovascular surgery have been reported, but there is perspective for more frequent use of these assays in the assessment of platelet response to antiplatelet therapy and in the assessment of coagulation in patients on long-term dabigatran therapy. This article reviews the current role and future perspectives of thromboelastography and thromboelastometry in the management of cardiovascular diseases.

[Hemorrhage under direct oral anticoagulants : Occurrence and treatment in intensive care patients]

The use of anticoagulants is associated with an increased risk of bleeding and nevertheless bleeding complications can be lifethreatening. The focus is on bleeding under direct oral anticoagulants (DOAC) because antidotes and specific measures are lacking for some DOACs. Furthermore, routinely carried out clotting tests cannot be used to determine the degree of anticoagulation under DOACs. Therefore, it becomes difficult to determine whether the coagulation inhibition effect is present. This article presents the treatment of hemorrhage in patients with DOACs in the intensive care unit. Further, the indications for DOACS and details of administration and monitoring are presented.

Pharmacologic Reversal of Direct Oral Anticoagulants

Direct oral anticoagulants are becoming increasingly popular in outpatient use. These medications have lacked specific reversal agents. However, this is changing. The Federal Food and Drug Administration approved idarucizumab for reversal of dabigatran in 2016, and another agent, andexanet alfa, is currently in clinical trials for reversal of rivaroxaban and apixaban. This article examines the efficacy and safety of these emerging reversal agents, as well as other historical agents for reversal of direct oral anticoagulants.

Practical guidance on the use of laboratory testing in the management of bleeding in patients receiving direct oral anticoagulants

Direct oral anticoagulants (DOACs) have demonstrated a favorable benefit–risk profile in several thromboembolic disorders and are increasingly used in routine clinical practice. A number of real-world studies on DOACs are ongoing, and data published so far have shown broadly similar outcomes to those demonstrated in the respective phase III trials. Despite their beneficial attributes, bleeding risk (as with any other anticoagulants) is often a concern for physicians when prescribing DOACs, particularly in elderly patients, those with significant comorbidities, and other high-risk patient populations. Although the absence of routine coagulation monitoring is an advantage of the DOACs, measuring their anticoagulant effect and/or plasma drug levels may be helpful in certain clinical scenarios to help patient management and improve outcomes. In this paper, practical guidance and recommendations are provided for clinical situations in which the test results may aid clinical decision-making, including patients with life-threatening bleeding events, patients without bleeding but with test results indicating a risk of bleeding, for those patients with a suspected thromboembolism while receiving a DOAC, or prior to patients undergoing elective or urgent surgical procedures. Finally, appropriate monitoring of the DOACs could be of substantial benefit to patients, and there is a high potential for development in this area in the future.

Emergency care of patients receiving non-vitamin K antagonist oral anticoagulants

Non-vitamin K antagonist oral anticoagulants (NOACs), which inhibit thrombin (dabigatran) and factor Xa (rivaroxaban, apixaban, edoxaban) have been introduced in several clinical indications. Although NOACs have a favourable benefit-risk profile and can be used without routine laboratory monitoring, they are associated-as any anticoagulant-with a risk of bleeding. In addition, treatment may need to be interrupted in patients who need surgery or other procedures. The objective of this article, developed by a multidisciplinary panel of experts in thrombosis and haemostasis, is to provide an update on the management of NOAC-treated patients who experience a bleeding episode or require an urgent procedure. Recent advances in the development of targeted reversal agents are expected to help streamline the management of NOAC-treated patients in whom rapid reversal of anticoagulation is required.

The reversal effect of prothrombin complex concentrate (PCC), activated PCC and recombinant activated factor VII in apixaban-treated patients in vitro

BACKGROUND

The number of patients under treatment with FXa inhibitors is increasing, but there is no concensus on how to reverse their anticoagulant effect in case of a life-threatening bleeding. A specific antidote is not yet commercially available. Prothrombin complex concentrate (PCC), activated PCC (aPCC) and recombinant factor VIIa (rFVIIa) are suggested available reversal agents.

OBJECTIVES

To find the most effective reversal agent to apixaban and to determine the optimal dose.

PATIENTS/METHODS

PCC, aPCC, and rFVIIa at concentrations imitating 80%, 100%, and 125% of suggested therapeutic doses were added to blood drawn from apixaban-treated patients (n=30). aPCC was also tested in a 50% dose. Samples from healthy subjects (n=40) were used as controls. Thromboelastometry in whole blood (WB) and thrombin generation in platelet-poor plasma (PPP) were measured to assess the reversal effect.

RESULTS

aPCC shortened clotting time (CT) in WB, and increased the peak thrombin concentration and velocity index in PPP to a greater extent than PCC and rFVIIa. No significant differences were seen between rFVIIa and aPCC on thrombin generation lag time, or between PCC and aPCC on endogenous thrombin potential (ETP). The 50% dose of aPCC had a slightly inferior effect, but was comparable to the other reversal agents.

CONCLUSIONS

In this in vitro study the 80% dose of aPCC (40 IU/kg) reversed the anticoagulant effect of apixaban more effectively than the corresponding dose of rFVIIa and PCC both in WB (CT) and PPP (peak, ETP).

Anticoagulant activity of oral rivaroxaban in healthy dogs

Rivaroxaban is an oral, direct factor Xa inhibitor used in human thrombotic disorders. In view of the in vitro concentration dependent anticoagulant effects of rivaroxaban in dogs, the time course of its anticoagulant effects was characterized in healthy dogs. Twenty-four healthy Beagles were randomized into three groups (n = 8 per group) and received orally either a placebo or 20 mg rivaroxaban once or twice at an 8 h interval. Fifteen blood samples were collected over a 30 h period, and blindly assayed for prothrombin time (PT), activated partial thromboplastin time (aPTT), tissue factor induced thrombin generation (TG) and anti-factor Xa activity. Thromboelastography (TEG) was evaluated at 0, 1, 4, 8 and 24 h. Peak/baseline anticoagulant effect ratios were analyzed with generalized linear models using β distributions and times to return to baseline with survival analyses (α = 0.05). Peak/baseline anticoagulant effect ratios of PT, aPTT, anti-factor Xa activity, TG and R (TEG) differed significantly between placebo and both rivaroxaban groups (P <0.0001). The peak anticoagulant effect of rivaroxaban occurred 1.5 to 2 h after dosing. The median return to baseline occurred significantly sooner (P <0.01) with 20 mg rivaroxaban administered once (7.9-18.7 h) versus twice (17.5-26.8 h). The inter-individual variability differed amongst assays, but overall was moderate to large. No adverse effects were recorded. Twice oral administration of 2 mg/kg rivaroxaban at an 8 h interval maintained 24 h anticoagulant activity, but larger studies are needed to establish guidelines for the use of rivaroxaban in dogs.

Optimal Reversal of Novel Anticoagulants in Trauma

The incidence of patients with trauma on novel oral anticoagulants (NOACs) for the treatment of thromboembolic disorders is increasing. In severe bleeding or hemorrhage into critical spaces, urgent reversal of this underlying pharmacologic coagulopathy becomes paramount. Optimal reversal strategy for commonly used NOACs is still evolving. Basic tenets of evaluation of patients with trauma and resuscitation remain the same. Clinical outcomes data in bleeding human patients with trauma are lacking, but are needed to establish efficacy and safety in these treatments. This article summarizes the available evidence and provides the optimal reversal strategy for bleeding patients with trauma on NOACs.

The impact of irrigating fluid absorption on blood coagulation in patients undergoing transurethral resection of the prostate: A prospective observational study using rotational thromboelastometry

Although endoscopic transurethral resection of the prostate (TURP) is a well-established procedure as a treatment for benign prostatic hyperplasia, its complications remain a concern. Among these, coagulopathy may be caused by the absorption of irrigating fluid. This study aimed to evaluate such phenomenon using a rotational thromboelastometry (ROTEM).A total of 20 patients undergoing TURP participated in this study. A mixture of 2.7% sorbitol-0.54% mannitol solution and 1% ethanol was used as an irrigating fluid, and fluid absorption was measured via the ethanol concentration in expired breath. The effects on coagulation were assessed by pre- and postoperative laboratory blood tests, including hemoglobin, hematocrit, platelet count, international normalized ratio of prothrombin time (PT-INR), activated partial thromboplastin time, electrolyte, and ROTEM.INTEM-clotting time (INTEM-CT) was significantly lengthened by 14% (P = 0.001). INTEM-α-angle was significantly decreased by 3% (P = 0.011). EXTEM-clot formation time was significantly prolonged by 18% (P = 0.008), and EXTEM-maximum clot firmness (EXTEM-MCF) was significantly decreased by 4% (P = 0.010). FIBTEM-MCF was also significantly decreased by 13% (P = 0.015). Moreover, hemoglobin (P < 0.001), hematocrit (P < 0.001), platelet counts (P < 0.001), potassium (P = 0.024), and ionized calcium (P = 0.004) were significantly decreased, while PT-INR (P = 0.001) was significantly increased after surgery. The amount of irrigating fluid absorbed was significantly associated with the weight of resected prostatic tissue (P = 0.001) and change of INTEM-CT (P < 0.001).As shown by the ROTEM analysis, the irrigating fluid absorbed during TURP impaired the blood coagulation cascade by creating a disruption in the coagulation factor activity or by lowering the coagulation factor concentration via dilution.

Nonvitamin K antagonist oral anticoagulant activity: challenges in measurement and reversal

Background

Four nonvitamin K antagonist oral anticoagulants (NOACs) are approved for the prevention of stroke in patients with nonvalvular atrial fibrillation and for the treatment of venous thromboembolism. These include the direct thrombin inhibitor dabigatran and the direct factor Xa inhibitors rivaroxaban, apixaban, and edoxaban. Bleeding is a complication for all anticoagulants and concerns regarding bleeding risk and the suitability of effective reversal strategies may be a barrier to their prescription. Despite the reduced risk of bleeding compared with vitamin K antagonists, questions persist regarding the management of bleeding related to NOAC use.

Main text

To date, although a number of assays are responsive to NOACs, no single routine laboratory test has been identified to accurately measure the clinical anticoagulation state of patients on NOACs or established as a reliable predictor of bleeding risk. In addition, the establishment of a reliable human bleeding model to test novel inhibitors of the coagulation cascade has proved challenging. Although routine monitoring of anticoagulant levels is not necessary in patients taking NOACs, anticoagulant reversal and a means of measuring reversal may be required for patients who present with bleeding or require urgent surgery. Prothrombin complex concentrates are pooled plasma products containing varying amounts of inactive vitamin K-dependent clotting factors in addition to vitamin K-dependent proteins and can replenish factors in the intrinsic and extrinsic coagulation cascade, reversing an anticoagulant effect. Only one agent, idarucizumab, has been approved for rapid reversal of dabigatran-induced anticoagulation and one more agent, andexanet alfa, has been submitted for approval to reverse the anticoagulatory effects of direct and indirect factor Xa inhibitors.

Conclusions

This review discusses the laboratory tests available for assessing anticoagulation, human models of bleeding, and the use of current strategies—including prothrombin complex concentrates for reversal of anticoagulation by NOACs—to manage bleeding in patients.

Ex vivo reversal of effects of rivaroxaban evaluated using thromboelastometry and thrombin generation assay

Background

In major bleeding events, the new direct oral anticoagulants pose a great challenge for physicians. The aim of the study was to test for ex vivo reversal of the direct oral anticoagulant rivaroxaban with various non-specific reversal agents: prothrombin complex concentrate (PCC), activated prothrombin complex concentrate (aPCC), recombinant activated factor VII (rFVIIa), and fibrinogen concentrate (FI).

Methods

Blood was obtained from healthy volunteers and from patients treated with rivaroxaban. Blood samples from healthy volunteers were spiked with rivaroxaban to test the correlation between rivaroxaban concentration and coagulation tests. Patient blood samples were spiked with various concentrations of the above-mentioned agents and analysed using thromboelastometry and thrombin generation.

Results

When added in vitro, rivaroxaban was significantly (P<0.05) correlated with ROTEM^® thromboelastometry EXTEM (extrinsic coagulation pathway) clotting time (CT), time to maximal velocity (MaxV−t), and with all measured thrombin generation parameters. In vivo, CT, MaxV−t, lag time, and peak thrombin generation (C_max) were significantly correlated with rivaroxaban concentrations. Regarding reversal of rivaroxaban, all tested agents significantly (P<0.05) reduced EXTEM CT, but to different extents: rFVIIa by 68%, aPCC by 47%, PCC by 17%, and FI by 9%. Only rFVIIa reversed EXTEM CT to baseline values. Both PCC (+102%) and aPCC (+232%) altered overall thrombin generation (area under the curve) and increased C_max (+461% for PCC, +87.5% for aPCC).

Conclusions

Thromboelastometry and thrombin generation assays do not favour the same reversal agents for rivaroxaban anticoagulation. Controlled clinical trials are urgently needed to establish doses and clinical efficacy of potential reversal agents.

Clinical trial registration

EudracCT trial no. 213-00474-30.

Thromboelastometry versus free-oscillation rheometry and enoxaparin versus tinzaparin: an in-vitro study comparing two viscoelastic haemostatic tests' dose-responses to two low molecular weight heparins at the time of withdrawing epidural catheters from ten patients after major surgery

Background

Monitoring low molecular weight heparins (LMWH’s) in the perioperative period is prudent in patients at high risk of coagulative complications, especially when the patient has an epidural catheter requiring withdrawal, which is associated with the risk of spinal haematoma. The aim of this study was to evaluate the in vitro dose-responses of two different LMWH’s on two different viscoelastic haemostatic tests, using blood sampled from patients with normal routine coagulation parameters, on the day after major surgery when their epidural catheters were due to be withdrawn.

Methods

Enoxaparin or tinzaparin were added in vitro to blood from ten patients who had undergone oesophageal resection, to obtain plasma concentrations of approximately 0, 0.5, 1.0 and 1.5 IU/mL. Coagulation was monitored using thromboelastometry (ROTEM®) using the InTEM® activating reagent; and free oscillation rheometry (FOR: ReoRox®), activated using thromboplastin. Clot initiation was measured using ROTEM-CT, ReoRox-COT1 and ReoRox–COT2. Clot propagation was measured using ROTEM-CFT, ROTEM-Alpha Angle and ReoRox-Slope. Clot stability was measured using ROTEM-MCF and ReoRox-G’max, and clot lysis was measured using ROTEM-ML and ReoRox-ClotSR.

Results

Clot initiation time assessed by thromboelastometry and FOR was prolonged by increasing concentrations of both LMWH’s (P < 0.01). Equivalent doses of tinzaparin in international units (anti-FXa units) per millilitre prolonged clot initiation more than enoxaparin (P < 0.05). There was significant inter-individual variation – the ranges of CT and COT1 at LMWH-concentrations of 0 and 1.5 IU/mL overlapped. None of the tests reflecting clot formation rate or stability showed a dose–response to either LMWH but clot lysis showed a tentative negative dose–response to the LMWH’s.

Conclusions

Clot initiation time’s dose-dependent prolongation by LMWH’s in this study agrees with previous research, as does tinzaparin’s stronger anti-coagulative effect than enoxaparin at equivalent levels of anti-FXa activity. This casts doubt on the validity of using anti-FXa assays alone to guide dosage of LMWH’s. The significant inter-individual variation in dose–response suggests that the relationship between dose and effect in the postoperative period is complicated. While both ROTEM and FOR may have some role in postoperative monitoring, more research is needed before any conclusion can be made about their clinical usefulness.

Electronic supplementary material

The online version of this article (doi:10.1186/s12871-015-0145-2) contains supplementary material, which is available to authorized users.

Monitoring of hematological and hemostatic parameters in neurocritical care patients

Anemia and bleeding are paramount concerns in neurocritical care and often relate to the severity of intracranial hemorrhage. Anemia is generally associated with worse outcomes, and efforts to minimize anemia through reduced volume of blood sampled are encouraged. Point-of-care-testing reliably detects the use of non-steroidal anti-inflammatory drugs that may worsen bleeding and reduce platelet activity, particularly in patients with intracerebral hemorrhage. How best to monitor the effect of platelet transfusion or platelet-activating therapy is not well studied. For patients known to take novel oral anticoagulants, drug-specific coagulation tests before neurosurgical intervention are prudent.

Use of Thromboelastography (TEG) for Detection of New Oral Anticoagulants

CONTEXT

The clinical introduction of new oral anticoagulants (NOACs) has stimulated the development of tests to quantify the effects of these drugs and manage complications associated with their use. Until recently, the only treatment choices for the prevention of venous thromboembolism in orthopedic surgical patients, as well as for stroke and systemic embolism in patients with atrial fibrillation, were vitamin K antagonists, antiplatelet drugs, and unfractionated and low-molecular-weight heparins. With the approval of NOACs, treatment options and consequent diagnostic challenges have expanded.

OBJECTIVE

To study the utility of thromboelastography (TEG) in monitoring and differentiating between 2 currently approved classes of NOACs, direct thrombin inhibitors (dabigatran) and factor Xa inhibitors (rivaroxaban and apixaban).

DESIGN

Blood samples from healthy volunteers were spiked with each NOAC in both the presence and absence of ecarin, and the effects on TEG were evaluated.

RESULTS

Both the kaolin test reaction time (R time) and the time to maximum rate of thrombus generation were prolonged versus control samples and demonstrated a dose response for apixaban (R time within the normal range) and dabigatran. The RapidTEG activated clotting time test allowed the creation of a dose-response curve for all 3 NOACs. In the presence of anti-Xa inhibitors, the ecarin test promoted significant shortening of kaolin R times to the hypercoagulable range, while in the presence of the direct thrombin inhibitor only small and dose-proportional R time shortening was observed.

CONCLUSIONS

The RapidTEG activated clotting time test and the kaolin test appear to be capable of detecting and monitoring NOACs. The ecarin test may be used to differentiate between Xa inhibitors and direct thrombin inhibitors. Therefore, TEG may be a valuable tool to investigate hemostasis and the effectiveness of reversal strategies for patients receiving NOACs.

Point of care and factor concentrate-based coagulation algorithms

In the last years it has become evident that the use of blood products should be reduced whenever possible. There is increasing evidence regarding serious adverse events, including higher mortality and morbidity, related to transfusions. The use of point of care (POC) devices integrated in algorithms is one of the important mechanisms to limit blood product exposure. Any type of algorithm, especially the POC-based ones, allows goal-directed transfusions of blood products and even better targeted factor concentrate substitutions. Different types of algorithms in different surgical settings (cardiac surgery, trauma, liver surgery etc.) have been established with growing interest in their use as they offer objective therapy for management and reduction of blood product use. The use of POC devices with evidence-based algorithms is important in the bleeding patient independent of its origin (traumatic vs. surgical). The use of factor concentrates compared to the classical blood products can be cost-saving, beneficial for the patient, and in agreement with the WHO-requested standard of care. The empiric and uncontrolled use of blood products such as fresh frozen plasma, red blood cells, and platelets without POC monitoring should no longer be followed with regard to actual evidence in literature. Furthermore, the use of factor concentrates may provide better outcomes and potential for cost saving.

Thrombelastography detects the anticoagulant effect of rivaroxaban in patients with stroke

BACKGROUND AND PURPOSE

Factor Xa inhibitors are prescribed for stroke prevention in atrial fibrillation. Managing such patients is challenging especially if they are eligible for thrombolysis because there is no rapidly available test to detect the effect of such medications. Thrombelastography analyzes the dynamics of coagulation and can be rapidly performed. We sought to determine whether thrombelastography can detect the anticoagulation effect of factor Xa inhibitors in patients with stroke.

METHODS

Blood from 10 patients with stroke was analyzed by thrombelastography at baseline and 2 to 18 hours after rivaroxaban administration.

RESULTS

Increased R, K, and δ were seen at 2, 4, and 6 hours, while G, maximum amplitude, α-angle, and LY30 were decreased. Baseline R was 5.8±0.5 when compared with 11.4±1.0 at 2 hours. R remained prolonged at 18 hours. Other thrombelastography parameters were normal by 18 hours.

CONCLUSIONS

Thrombelastography can detect the anticoagulant effect of factor Xa inhibitors in patients with stroke and might be useful in the emergency management of those eligible for thrombolysis.

Novel anticoagulants and laboratory testing

The introduction of several oral direct anticoagulants within the past 2-3 years has dramatically changed clinical practice and has also impacted on utilization and interpretation of coagulation laboratory testing. This article reviews the effects of the oral thrombin inhibitor, dabigatran, and the oral factor Xa inhibitors, rivaroxaban and apixaban, on screening and diagnostic coagulation tests, and describes methods for measuring the their anticoagulant activity in plasma. Currently, there are evidence gaps regarding the role of laboratory testing for surveillance and management of adverse events associated with these new anticoagulants which do not require routine therapeutic drug monitoring. This is a rapidly changing field, and coagulation laboratory experts have a major role in ensuring patients receive appropriate testing and accurate interpretations of results.

Roles of thrombelastography and thromboelastometry for patient blood management in cardiac surgery

The value of thrombelastography (TEG) and thromboelastometry (ROTEM) to improve perioperative hemostasis is under debate. We aimed to assess the effects of TEG- or ROTEM-guided therapy in patients undergoing cardiac surgery on the use of allogeneic blood products. We analyzed 12 trials including 6835 patients, 749 of them included in 7 randomized controlled trials (RCTs). We collected data on the amount of transfused allogeneic blood products and on the proportion of patients who received allogeneic blood products or coagulation factor concentrates. Including all trials, the odds ratios (ORs) for transfusion of red blood cell (RBC) concentrates, fresh-frozen plasma (FFP), and platelets were 0.62 (95% confidence interval [CI], 0.56-0.69; P<.001), 0.28 (95% CI, 0.24-0.33; P<.001), and 0.55 (95% CI, 0.49-0.62; P<.001), respectively. However, more than 50% of the patients in this analysis were derived from one retrospective study. Including RCTs only, the ORs for transfusion of RBC, FFP, and platelets were 0.54 (95% CI, 0.38-0.77; P<.001), 0.36 (95% CI, 0.25-0.53; P<.001), and 0.57 (95% CI, 0.39-0.81; P=.002), respectively. The use of coagulation factor concentrates was reported in 6 studies, 2 of them were RCTs. The ORs for the infusion of fibrinogen and prothrombin complex concentrate were 1.56 (95% CI, 1.29-1.87; P<.001) and 1.74 (95% CI, 1.40-2.18; P<.001), respectively. However, frequencies and amounts were similar in the intervention and control group in the 2 RCTs. It is presumed that TEG- or ROTEM-guided hemostatic management reduces the proportion of patients undergoing cardiac surgery transfused with RBC, FFP, and platelets. This presumption is strongly supported by similar ORs found in the analysis including RCTs only. Patient blood management based on the transfusion triggers by TEG or ROTEM appears to be more restrictive than the one based on conventional laboratory testing. However, evidence for improved clinical outcome is limited at this time.

Current State of Knowledge on Oral Anticoagulant Reversal Using Procoagulant Factors

OBJECTIVE:

To discuss current trends and challenges in the use of procoagulants for treating bleeding caused by use of oral anticoagulants.

DATA SOURCES:

Literature searches of PubMed (MEDLINE), Google, and Medscape were conducted in February 2013. There were no date limitations. Search terms included anticoagulation agents, anticoagulation reversal, anticoagulation reversal agents, apixaban, clinical studies, dabigatran, 3-factor PCCs, 4-factor PCCs, FEIBA, fresh frozen plasma, human studies, pharmacology, prescribing information, rFVIIa, rivaroxaban, vitamin K, and warfarin.

DATA SYNTHESIS:

Warfarin has been the mainstay for the treatment and prevention of primary and secondary thrombosis in patients with cardiovascular disorders such as atrial fibrillation, deep vein thrombosis, pulmonary embolism, and stroke. Three oral anticoagulants have recently become available in the US: a direct thrombin inhibitor, dabigatran etexilate, and 2 direct factor Xa inhibitors, rivaroxaban and apixaban. Reversal strategies for anticoagulant-associated bleeding are well established for warfarin; however, strategies to stop bleeding in a patient who has taken one of the newer anticoagulants are less clear. In the US, agents available for oral anticoagulant reversal include activated prothrombin complex concentrate (APCC), 3-factor PCCs, and recombinant activated factor VII (rFVIIa). Few studies have evaluated the 3-factor PCCs, and current evidence for APCC and rFVIIa as reversal agents for dabigatran and rivaroxaban is based primarily on laboratory or animal studies, or on small studies in healthy humans and case reports.

CONCLUSIONS:

Patients contemplating using the new oral anticoagulants should be informed about specific clinical situations that could pose a bleeding risk such as the need for emergency surgery because no reliable antidote is available to stop the bleeding, which could prove fatal.