Reversal of rivaroxaban anticoagulation by haemostatic agents in rats and primates

Comparative analysis of andexanet alfa and prothrombin complex concentrate in reversing anticoagulation by rivaroxaban ex vivo

BACKGROUND

The comparative effectiveness of the specific antidote andexanet alfa vs the nonspecific therapy four-factor prothrombin complex concentrates (4F-PCCs) as reversal agents for direct factor Xa (FXa) inhibitors in severely bleeding patients is unclear. We hypothesised that specific reversal using andexanet alfa would be more effective than a high dose of PCC (50 IU kg-1) for reversing the FXa inhibitor rivaroxaban.

METHODS

The reversal potential of andexanet alfa, various 4F-PCCs, and activated PCC was investigated ex vivo in human blood anticoagulated with rivaroxaban (37.5, 75, 150, and 300 ng ml-1) using a panel of coagulation parameters, including conventional coagulation assays, thrombin generation, and a newly developed viscoelastometric device. We simulated in vivo conditions of coagulation activation and fibrin formation using flow chamber experiments of thrombogenicity potential under arterial flow conditions.

RESULTS

The 4F-PCCs normalised clotting profiles only at low rivaroxaban concentrations, whereas andexanet alfa and activated PCC significantly shortened clotting time at all rivaroxaban concentrations. Only andexanet alfa restored thrombin generation to baseline. Flow chamber results showed that various 4F-PCCs concentration-dependently restored clot formation.

CONCLUSIONS

In contrast to thrombin generation measurements, haemostatic reversal of rivaroxaban using high-dose 4F-PCCs exhibited similar efficacy as andexanet alfa in flow chamber experiments. The haemostatic effects of 4F-PCCs and andexanet alfa in the context of bleeding patients taking FXa inhibitors requires further study.

Real-world decision-making in the management of patients presenting with major bleeding on rivaroxaban: the Auckland regional experience

BACKGROUND

Rivaroxaban is used increasingly as an oral anticoagulant; however, a specific reversal agent is not currently available in the Australasian setting. There is also variation across international consensus guidelines regarding advice on the management of bleeding.

AIMS

To review the real-world management of rivaroxaban-associated major bleeding across the public hospitals of New Zealand's largest city.

METHODS

A retrospective cohort analysis was performed of patients prescribed rivaroxaban who presented to four metropolitan hospital Emergency Departments between 1 August 2018 and 31 May 2021 with major bleeding as defined by the International Society on Thrombosis and Haemostasis.

RESULTS

One hundred and twelve patients were identified, accounting for 115 major bleeding presentations. Upper gastrointestinal (34%) and intracranial (31%) bleeding sites were most common. Procedural intervention was required in 44% of patients. Haemostatic management involved tranexamic acid (TXA) in 26%, prothrombin complex concentrate (PCC) in 55% (dose range 1000-6000 IU or 10-65 IU/kg), vitamin K in 16% and fresh frozen plasma in 1%. Rivaroxaban was discontinued permanently following 56 (49%) events, switched to another anticoagulant in 24 (21%) and withheld in 30 (26%) from 2 days to 3 months (median 8.5 days). All-cause mortality at 90 days after bleeding was 17% (19 patients), and the incidence of combined venous and arterial thrombotic events was 10%.

CONCLUSIONS

There is considerable heterogeneity in the acute clinical management of patients presenting with rivaroxaban-related major bleeding. The use of PCC and dosage administered is inconsistent. TXA was utilised in only approximately one-quarter of all cases. Evidence-based guidance for treating rivaroxaban-related bleeding would improve the management of these patients and potentially improve clinical outcomes.

Recommendations for the use of andexanet alfa in the management of bleeding in patients on oral factor Xa inhibitors in Switzerland: Guideline from the Working Party Hemostasis of the Swiss Society of Hematology

Anticoagulants are essential in preventing and treating thrombosis. Unfortunately, their use is accompanied by an enhanced risk of bleeding. Since the introduction of direct oral anticoagulants (DOACs), the risk of major bleeding has been reduced but not eliminated. Major bleeding events related to the use of factor Xa inhibitors can be challenging to manage. In recent years, four-factor prothrombin complex concentrates have been used in patients with severe bleeding taking oral direct factor Xa inhibitors (apixaban, edoxaban and rivaroxaban). Andexanet alfa (OndexxyaTM, AstraZeneca AG) is a specially designed recombinant version of human factor Xa that acts as a decoy receptor to reverse the effects of factor Xa inhibitors. Since 2 December 2020, andexanet alfa has been used in Switzerland for adult patients receiving apixaban or rivaroxaban when reversal of anticoagulation is required because of life-threatening or uncontrolled bleeding. However, the use of andexanet alfa remains a challenge owing to its cost, the reported thrombotic complications and the fact that its efficacy mainly relates to intracranial haemorrhage. Moreover, the use of nonspecific reversal agents together with andexanet alfa is controversial. The present recommendations on the use of andexanet alfa in the management of bleeding in patients on factor Xa inhibitors in Switzerland were developed by a group of Swiss experts from the Working Party Hemostasis of the Swiss Society of Hematology. These recommendations aim to provide support to clinicians in their decision-making in the management of patients with major bleeding receiving factor Xa inhibitors.

Reversing Rivaroxaban Anticoagulation as Part of a Multimodal Hemostatic Intervention in a Polytrauma Animal Model

BACKGROUND

Life-threatening bleeding requires prompt reversal of the anticoagulant effects of factor Xa inhibitors. This study investigated the effectiveness of four-factor prothrombin complex concentrate in treating trauma-related hemorrhage with rivaroxaban-anticoagulation in a pig polytrauma model. This study also tested the hypothesis that the combined use of a low dose of prothrombin complex concentrate plus tranexamic acid and fibrinogen concentrate could improve its subtherapeutic effects.

METHODS

Trauma (blunt liver injury and bilateral femur fractures) was induced in 48 anesthetized male pigs after 30 min of rivaroxaban infusion (1 mg/kg). Animals in the first part of the study received prothrombin complex concentrate (12.5, 25, and 50 U/kg). In the second part, animals were treated with 12.5 U/kg prothrombin complex concentrate plus tranexamic acid or plus tranexamic acid and fibrinogen concentrate. The primary endpoint was total blood loss postinjury. The secondary endpoints (panel of coagulation parameters and thrombin generation) were monitored for 240 min posttrauma or until death.

RESULTS

The first part of the study showed that blood loss was significantly lower in the 25 U/kg prothrombin complex concentrate (1,541 ± 269 ml) and 50 U/kg prothrombin complex concentrate (1,464 ± 108 ml) compared with control (3,313 ± 634 ml), and 12.5 U/kg prothrombin complex concentrate (2,671 ± 334 ml, all P < 0.0001). In the second part of the study, blood loss was significantly less in the 12.5 U/kg prothrombin complex concentrate plus tranexamic acid and fibrinogen concentrate (1,836 ± 556 ml, P < 0.001) compared with 12.5 U/kg prothrombin complex concentrate plus tranexamic acid (2,910 ± 856 ml), and there were no early deaths in the 25 U/kg prothrombin complex concentrate, 50 U/kg prothrombin complex concentrate, and 12.5 U/kg prothrombin complex concentrate plus tranexamic acid and fibrinogen concentrate groups. Histopathologic analyses postmortem showed no adverse events.

CONCLUSIONS

Prothrombin complex concentrate effectively reduced blood loss, restored hemostasis, and balanced thrombin generation. A multimodal hemostatic approach using tranexamic acid plus fibrinogen concentrate enhanced the effect of low doses of prothrombin complex concentrate, potentially reducing the prothrombin complex concentrate doses required for effective bleeding control.

EDITOR’S PERSPECTIVE

Efficacy of prothrombin complex concentrate in the management of oral factor Xa inhibitors associated major bleed assessed by ISTH and ANNEXA-4 criteria

Direct oral anticoagulants (DOACs) are increasingly used for stroke prevention in atrial fibrillation and treatment and prevention of venous thromboembolism. They are also associated with bleeding risk. Existing literature suggests that prothrombin complex concentrate (PCC) administration may help control bleeding due to factor Xa inhibitors (FXaI). To determine the hemostatic efficacy of PCC in patients with major bleeding due to FXaI, we performed a retrospective chart review of 50 patients who presented with FXaI associated major bleeding that required urgent hemostatic management. Hemostatic assessment was performed using ISTH and ANNEXA-4 criteria. Twenty patients presented with intracranial hemorrhage (ICH), 20 had gastrointestinal bleeding, 3 had visceral bleeding, 3 had genitourinary bleeding, and 4 had miscellaneous types of bleeding. Fifty-six percent (28/50) had effective hemostasis using ISTH criteria and 84% (42/50) achieved effective hemostasis by ANNEXA-4 criteria. Hemostatic efficacy was similar by both tools for ICH (75% each). However, there was a major difference between ISTH and ANNEXA-4 hemostatic efficacy assessments for GI bleeding (45% and 95%, respectively). When comparing rivaroxaban and apixaban, there was no significant difference in effective hemostasis using either criteria, time to hemostasis, thromboembolic events, or patient mortality. Five (10%) patients had thromboembolic events within seven days of PCC administration, and the 30-day mortality rate was 14% (7/50). Our study shows similar efficacy, thromboembolic events, and mortality associated with PCC compared to andexanet alfa using ANNEXA-4 criteria, suggesting that PCC may be a viable alternative.

Activated prothrombin complex concentrates for direct oral anticoagulant-associated bleeding or urgent surgery: Hemostatic and thrombotic outcomes

INTRODUCTION

Studies evaluating the use of activated prothrombin complex concentrates (aPCCs) for DOAC-associated bleeding are sparse.

MATERIALS AND METHODS

We conducted a retrospective study of patients receiving aPCC for DOAC-associated bleeding or for pre-operative optimization of hemostasis prior to urgent surgery. The primary efficacy outcome was hemostatic efficacy, the primary safety outcome was the 30-day thromboembolic complication rate.

RESULTS

Eighty-two patients were included in the analysis; 14 patients on dabigatran, 39 patients on rivaroxaban and 29 patients on apixaban. Fifty-four patients received aPCC for major bleeding and 28 patients prior to urgent surgery. Mean aPCC dosing was 2974 IU (SD ± 857 IU). Hemostasis was deemed effective by ISTH criteria in 50% of cases and "Good" or "Moderate" by Sarode criteria in 45.2% and 14.3% of cases, respectively. Surgical hemostasis was rated as "Normal" in 84% of cases pre-operative administration. Median pre-aPCC INR was 1.6 (IQR 0.5) and median post-aPCC INR was 1.2 (IQR 0.2) (p < 0.00001). Median pre-aPCC aPTT was 36 s (IQR 12.8), median post-aPCC aPTT was 29 s (IQR 9.8) (p = 0.0001). The 30-day thromboembolic event rate was 6.1%.

CONCLUSION

Further study is needed to characterize the hemostatic effects and thromboembolic risk of aPCC among patients with DOAC-associated bleeding or for attempted normalization of hemostasis prior to urgent surgery.

Assessing and Reversing the Effect of Direct Oral Anticoagulants on Coagulation

This article presents a focused review of the available tests to assess the effect of direct oral anticoagulants on coagulation and the use of reversal agents in the perioperative setting for practicing anesthesiologists.

Four-factor Prothrombin Complex Concentrate for the Management of Patients Receiving Direct Oral Activated Factor X Inhibitors

Factor Xa inhibitors prevent thrombosis but are associated with severe or life-threatening bleeding. Here, the authors present data on four-factor prothrombin complex concentrates in management of anticoagulation-associated bleeding and restoring hemostasis, including recent results from the UPRATE study.

The impact of prothrombin complex concentrates when treating DOAC-associated bleeding: a review

Background

Bleeding complications are a risk associated with all anticoagulants. Currently, the treatment options for the management of direct oral anticoagulant (DOAC)-associated bleeding are limited. Prothrombin complex concentrates (PCCs) have been proposed as a potential therapeutic option, and evidence regarding their use is increasing.

Review

Many studies supporting PCC have used preclinical models and healthy volunteers; however, more recently, observational studies have further improved insight into current DOAC reversal strategies. Multiple clinical practice guidelines now specifically suggest use of PCCs for this indication. Specific reversal agents for Factor Xa inhibitors may become available in the near future, but data on their efficacy are still emerging.

Conclusions

Ultimately, a multimodal approach may be the optimal strategy to restore haemostasis in patients presenting with DOAC-associated coagulopathy.

Electronic supplementary material

The online version of this article (10.1186/s12245-018-0215-6) contains supplementary material, which is available to authorized users.

Safety of 4-factor prothrombin complex concentrate (4F-PCC) for emergent reversal of factor Xa inhibitors

Background

Although factor Xa inhibitors have become a popular choice for chronic oral anticoagulation, effective drug reversal remains difficult due to a lack of specific antidote. Currently, 4-factor prothrombin complex concentrate (4F-PCC) is considered the treatment of choice for factor Xa inhibitor-related major bleeding. However, safety of 4F-PCC and its risk of thrombosis when used for this off-label purpose remain unclear. The purpose of this retrospective study is to determine the rate of thromboembolism when 4F-PCC is used for the emergent reversal of factor Xa inhibitors.

Methods

We conducted a single-center retrospective review of medical records between 2013 and 2017. Patients were included if they received 4F-PCC to reverse rivaroxaban, apixaban, or edoxaban for emergent invasive procedures or during episodes of major bleeding defined as bleeding with hemodynamic instability, fall in hemoglobin of 2 g/dL, or bleeding requiring blood transfusion. Thrombotic events including myocardial infarction, pulmonary embolism, deep vein thrombosis, cerebral vascular accident, and arterial thrombosis of the limb or mesentery were recorded if they occurred within 14 days of 4F-PCC administration. Data was analyzed using point and interval estimation to approximate the rate and confidence interval of thromboembolic events.

Results

Forty-three patients were identified in our review. Doses of 4F-PCC were determined by the treating physician and mainly ranged from 25 to 50 IU/kg. Twenty-two patients (51.2%) received both sequential compression devices (SCDs) and subcutaneous heparin for DVT prophylaxis. Twenty-one patients (48.8%) were placed on SCDs only. Three patients received concomitant FFP. Thrombotic events within 14 days of 4F-PCC administration occurred in 1 out of 43 patients (2.1%, 95% CI [0.1–12.3]). This thrombotic event was an upper extremity DVT which occurred 1 day after the patient received 1325 IU (25 IU/kg) of 4F-PCC to reverse rivaroxaban for traumatic intracranial hemorrhage. The patient was taken for emergent decompressive craniotomy after rivaroxaban reversal. In patients who did not undergo surgery or who underwent minor invasive procedures, no thrombotic events were noted.

Conclusion

Based on our preliminary data, the thromboembolic rate of 4F-PCC when given at a dose of 25–50 IU/kg to emergently reverse rivaroxaban and apixaban appears acceptable. Since many patients who require 4F-PCC to emergently reverse factor Xa inhibitors will be at high risk of developing thrombotic events, practitioners should be highly vigilant of these complications. Large, multicenter prospective trials are needed to further determine this risk.

[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.

Pharmacological reversal of the direct oral anticoagulants-A comprehensive review of the literature

The direct oral anticoagulants (DOACs) are used for stroke prevention in atrial fibrillation (SPAF) and the prevention and treatment of venous thromboembolic disease (VTE). Although DOAC-associated bleeding events are less frequent as compared to vitamin K antagonists, there is significant concern surrounding physicians' ability to evaluate and manage DOAC-associated bleeding when it does occur. Idarucizumab is a specific reversal agent for dabigatran and is the agent of choice for dabigatran reversal in the setting of major bleeding or urgent surgery/procedures. There are no commercially available specific reversal agents for the direct Xa inhibitors. Although they have not been rigorously studied in DOAC-treated patients requiring urgent anticoagulant reversal, limited evidence from in vitro studies, animal bleeding models, human volunteer studies (in vivo and in vitro) and case series suggest that coagulation factor replacement with prothrombin complex concentrate (PCC) and activated PCC (FEIBA) may contribute to hemostasis. However, the safety and efficacy of these agents and the optimal dosing strategies remain uncertain.

Pretreatment with rivaroxaban attenuates stroke severity in rats by a dual antithrombotic and anti-inflammatory mechanism

Stroke outcome is more favourable in patients receiving oral anticoagulants compared with non-anticoagulated patients. The reasons for this “stroke-attenuating” property of oral anticoagulants are largely unknown. This study examined whether prestroke anticoagulation with rivaroxaban, a novel direct factor Xa inhibitor, influences stroke severity, thrombin-mediated intracerebral thrombus formation and pro-inflammatory processes in a rat model of brain ischaemia/reperfusion injury. Male Wistar rats were anticoagulated with rivaroxaban and subjected to 90 minutes of transient middle cerebral artery occlusion. Infarct size, functional outcome and the occurrence of intracranial haemorrhage (ICH) were assessed until day 7. Thrombin generation was determined by measuring the amount of thrombin/antithrombin complex. Intracerebral thrombus formation was evaluated by histology and Western blot. CD68-immunoreactivity and the expression of cytokines and adhesion molecules were investigated to assess postischaemic inflammation. The integrity of the blood–brain barrier was analysed using fluorescein isothiocyanate-dextran. Rats pretreated with rivaroxaban developed significantly smaller strokes and less severe functional deficits compared with controls. Although rivaroxaban strongly reduced thrombin-mediated thrombus formation, this was not accompanied by an increased risk of ICH. In addition, rivaroxaban dampened the inflammatory response in the ischaemic brain by downregulating ICAM-1 expression and the activation of CD68+-immune cells. In contrast, rivaroxaban had no effect on the integrity of the blood–brain barrier after stroke. Here, we identified reduced thrombo-inflammation as a major determinant of the stroke-protective property of rivaroxaban in rats. Further studies are needed to assess the therapeutic potential of novel oral anticoagulants in the acute phase after a stroke.

Initial anticoagulation in patients with pulmonary embolism: thrombolysis, unfractionated heparin, LMWH, fondaparinux, or DOACs?

The initial treatment of haemodynamically stable patients with pulmonary embolism (PE) has dramatically changed since the introduction of low molecular weight heparins (LMWHs). With the recent discovery of the direct oral anticoagulant drugs (DOACs), initial treatment of PE will be simplified even further. In several large clinical trials it has been demonstrated that DOACs are not inferior to standard therapy for the initial treatment of PE, and because of their practicability they are becoming the agents of first choice. However, many relative contraindications to DOACs were exclusion criteria in the clinical trials. Therefore, LMWHs will continue to play an important role in initial PE treatment and in some cases there still is a role for unfractionated heparin (UFH). In this review we will give an overview of the biophysical, pharmacokinetic and pharmacodynamic properties of anticoagulants currently available for the initial management of PE. In addition, we will provide a comprehensive overview of the indications for the use of UFH, LMWHs and DOACs in the initial management of PE from a pharmacokinetic/-dynamic point of view.

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 Reversal and Anesthetic Considerations

Bleeding complications are a common concern with the use of anticoagulant agents. In many situations, reversing of neutralizing their effects may be warranted. Prothrombin complex concentrate replaces coagulation factors lowered by warfarin, as does fresh frozen plasma, but in a more concentrated form. Protamine negates the effect of heparin and combines chemically with heparin molecules to form an inactive salt. It also partially reverses the effects of low-molecular-weight heparin. Recombinant activated factor VII is a nonspecific procoagulant that activates the extrinsic clotting pathway, resulting in thrombin generation, but does not directly neutralize the activity of any of the new oral anticoagulants.

The Reversal of Direct Oral Anticoagulants in Animal Models

Several direct oral anticoagulants (DOACs), including direct thrombin and factor Xa inhibitors, have been approved as alternatives to vitamin K antagonist anticoagulants. As with any anticoagulant, DOAC use carries a risk of bleeding. In patients with major bleeding or needing urgent surgery, reversal of DOAC anticoagulation may be required, presenting a clinical challenge. The optimal strategy for DOAC reversal is being refined, and may include use of hemostatic agents such as prothrombin complex concentrates (PCCs; a source of concentrated clotting factors), or DOAC-specific antidotes (which bind their target DOAC to abrogate its activity). Though promising, most specific antidotes are still in development.Preclinical animal research is the key to establishing the efficacy and safety of potential reversal agents. Here, we summarize published preclinical animal studies on reversal of DOAC anticoagulation. These studies (n = 26) were identified via a PubMed search, and used rodent, rabbit, pig, and non-human primate models. The larger of these animals have the advantages of similar blood volume/hemodynamics to humans, and can be used to model polytrauma. We find that in addition to varied species being used, there is variability in the models and assays used between studies; we suggest that blood loss (bleeding volume) is the most clinically relevant measure of DOAC anticoagulation-related bleeding and its reversal.The studies covered indicate that both PCCs and specific reversal agents have the potential to be used as part of a clinical strategy for DOAC reversal. For the future, we advocate the development and use of standardized, clinically, and pharmacologically relevant animal models to study novel DOAC reversal strategies.

Animal Models of Thrombosis From Zebrafish to Nonhuman Primates: Use in the Elucidation of New Pathologic Pathways and the Development of Antithrombotic Drugs

Thrombosis is a leading cause of morbidity and mortality worldwide. Animal models are used to understand the pathological pathways involved in thrombosis and to test the efficacy and safety of new antithrombotic drugs. In this review, we will first describe the central role a variety of animal models of thrombosis and hemostasis has played in the development of new antiplatelet and anticoagulant drugs. These include the widely used P2Y12 antagonists and the recently developed orally available anticoagulants that directly target factor Xa or thrombin. Next, we will describe the new players, such as polyphosphate, neutrophil extracellular traps, and microparticles, which have been shown to contribute to thrombosis in mouse models, particularly venous thrombosis models. Other mouse studies have demonstrated roles for the factor XIIa and factor XIa in thrombosis. This has spurred the development of strategies to reduce their levels or activities as a new approach for preventing thrombosis. Finally, we will discuss the emergence of zebrafish as a model to study thrombosis and its potential use in the discovery of novel factors involved in thrombosis and hemostasis. Animal models of thrombosis from zebrafish to nonhuman primates are vital in identifying pathological pathways of thrombosis that can be safely targeted with a minimal effect on hemostasis. Future studies should focus on understanding the different triggers of thrombosis and the best drugs to prevent each type of thrombotic event.

The reversal effect of prothrombin complex concentrate (PCC), activated PCC and recombinant activated factor VII against anticoagulation of Xa inhibitor

Background

An increasing number of patients are treated with direct-acting oral anticoagulants (DOACs), but the optimal way to reverse the anticoagulant effect is not known. Specific antidotes are not available and prothrombin complex concentrate (PCC), activated PCC (aPCC) and recombinant factor VIIa (rFVIIa) are variously used as reversal agents in case of a major bleeding. We aimed to determine the most effective haemostatic agent and dose to reverse the effect of rivaroxaban in blood samples from patients taking rivaroxaban for therapeutic reasons.

Methods

Blood samples from rivaroxaban-treated patients (n = 50) were spiked with PCC, aPCC and rFVIIa at concentrations imitating 80%, 100% and 125% of suggested therapeutic doses. The reversal effect was assessed by thromboelastometry in whole blood and a thrombin generation assay (TGA) in platelet-poor plasma. Samples from healthy subjects (n = 40) were included as controls.

Results

In thromboelastometry measurements, aPCC and rFVIIa had a superior effect to PCC in reversing the rivaroxaban-induced lenghtening of clotting time (CT). aPCC was the only haemostatic agent that shortened the CT down to below the control level. Compared to healthy controls, patients on rivaroxaban also had a prolonged lag time and decreased peak concentration, velocity index and endogenous thrombin potential (ETP) in platelet-poor plasma. aPCC reversed these parameters more effectively than rFVIIa and PCC. There were no differences in efficacy between 80%, 100% and 125% doses of aPCC.

Conclusions

aPCC seems to reverse the anticoagulant effect of rivaroxaban more effectively than rFVIIa and PCC by evaluation with thromboelastometry and TGA in vitro.

Management of neurologic complications of coagulopathies

Coagulopathy is common in intensive care units (ICUs). Many physiologic derangements lead to dysfunctional hemostasis; these may be either congenital or acquired. The most devastating outcome of coagulopathy in the critically ill is major bleeding, defined by transfusion requirement, hemodynamic instability, or intracranial hemorrhage. ICU coagulopathy often poses complex management dilemmas, as bleeding risk must be tempered with thrombotic potential. Coagulopathy associated with intracranial hemorrhage bears directly on prognosis and outcome. There is a paucity of high-quality evidence for the management of coagulopathies in neurocritical care; however, data derived from studies of patients with intraparenchymal hemorrhage may inform treatment decisions. Coagulopathy is often broadly defined as any derangement of hemostasis resulting in either excessive bleeding or clotting, although most typically it is defined as impaired clot formation. Abnormalities in coagulation testing without overt clinical bleeding may also be considered evidence of coagulopathy. This chapter will focus on acquired conditions, such as organ failure, pharmacologic therapies, and platelet dysfunction that are associated with defective clot formation and result in, or exacerbate, intracranial hemorrhage, specifically spontaneous intraparenchymal hemorrhage and traumatic brain injury.

Management of Bleeding With Non-Vitamin K Antagonist Oral Anticoagulants in the Era of Specific Reversal Agents

Vitamin K antagonists are commonly used by clinicians to provide anticoagulation to patients who have or are at risk of having thrombotic events. In addition to familiarity with the dosing and monitoring of vitamin K antagonists, clinicians are accustomed to using vitamin K if there is a need to reverse the anticoagulant effect of vitamin K antagonists. There are now 4 new non-vitamin K antagonist oral anticoagulants (NOACs) that are attractive alternatives to vitamin K antagonists. Despite similar or lower rates of serious bleeding with NOACs in comparison with warfarin, there is a pressing need for strategies to manage bleeding when it does occur with NOACs and to reverse the pharmacological effect of these agents if needed. Important steps in minimizing bleeding risks with NOACs include dose adjustment of the agents in the setting of renal dysfunction and avoidance of the concomitant use of other antithrombotic agents if feasible. Laboratory measurement of the anticoagulant effect of NOACs is best accomplished with specialized assays, although some of the more widely available coagulation tests can provide information that is potentially useful to clinicians. Nonspecific hemostatic agents such as prothrombin complex concentrates and recombinant factor VIIa can be used to reverse the effect of NOACs. More specific reversing agents include the approved humanized monoclonal antibody fragment idarucizumab for reversing the effects of dabigatran, the investigational factor Xa decoy andexanet alfa, and the synthetic small molecule ciraparantag. Both andexanet and ciraparantag have been reported to reverse the effects of the anti-Xa NOACs (rivaroxaban, apixaban, and edoxaban), and a number of other anticoagulant agents in common clinical use, as well.

Guidance for the practical management of the direct oral anticoagulants (DOACs) in VTE treatment

Venous thromboembolism (VTE) is a serious medical condition associated with significant morbidity and mortality, and an incidence that is expected to double in the next forty years. The advent of direct oral anticoagulants (DOACs) has catalyzed significant changes in the therapeutic landscape of VTE treatment. As such, it is imperative that clinicians become familiar with and appropriately implement new treatment paradigms. This manuscript, initiated by the Anticoagulation Forum, provides clinical guidance for VTE treatment with the DOACs. When possible, guidance statements are supported by existing published evidence and guidelines. In instances where evidence or guidelines are lacking, guidance statements represent the consensus opinion of all authors of this manuscript and are endorsed by the Board of Directors of the Anticoagulation Forum.

The authors of this manuscript first developed a list of pivotal practical questions related to real-world clinical scenarios involving the use of DOACs for VTE treatment. We then performed a PubMed search for topics and key words including, but not limited to, apixaban, antidote, bridging, cancer, care transitions, dabigatran, direct oral anticoagulant, deep vein thrombosis, edoxaban, interactions, measurement, perioperative, pregnancy, pulmonary embolism, reversal, rivaroxaban, switching, \thrombophilia, venous thromboembolism, and warfarin to answer these questions. Non- English publications and publications > 10 years old were excluded. In an effort to provide practical information about the use of DOACs for VTE treatment, answers to each question are provided in the form of guidance statements, with the intent of high utility and applicability for frontline clinicians across a multitude of care settings.

Idarucizumab for Reversal of Dabigatran-Associated Bleeding: Misnomer or Miracle?

BACKGROUND

The development of novel oral anticoagulants (NOACs) has revolutionized oral anticoagulation. Rapid incorporation of NOACs into general practice has heightened the demand for directed reversal agents. Idarucizumab is a targeted reversal agent that is approved for the urgent reversal of the anticoagulant effects of dabigatran. While it is a welcome addition to reversal strategies of dabigatran, a number of clinical questions exist regarding its place in therapy.

OBJECTIVE

We describe controversies regarding the use of idarucizumab therapy in patients with dabigatran-associated bleeding.

DISCUSSION

Although existing clinical studies show a rapid reversal of coagulation assays, these studies did not describe a corresponding improvement in mortality or rapid cessation of hemorrhage. It is questionable how heavily clinicians can rely upon the use of the surrogate endpoints in clinical studies, such as ecarin clotting time and dilute thrombin time. Another issue is whether patients exhibiting re-elevation of coagulation assays would benefit from an additional dose of idarucizumab, because this has not been studied. It is currently unclear if blood products must be given in addition to idarucizumab can be used as monotherapy.

CONCLUSIONS

The initial data suggest a definite role for idarucizumab in treatment of bleeding associated with dabigatran. As more clinical practice experience is gained with the agent and the remaining data on its use are released, clinicians can better guide the clinical use of idarucizumab. At present, there is currently not enough evidence for idarucizumab to be used as monotherapy.

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.

A rapid pro-hemostatic approach to overcome direct oral anticoagulants

Direct inhibitors of coagulation factor Xa (FXa) or thrombin are promising oral anticoagulants that are becoming widely adopted. The ability to reverse their anticoagulant effects is important when serious bleeding occurs or urgent medical procedures are needed. Here, using experimental mouse models of hemostasis, we show that a variant coagulation factor, FXa(I16L), rapidly restores hemostasis in the presence of the anticoagulant effects of these inhibitors. The ability of FXa(I16L) to reverse the anticoagulant effects of FXa inhibitor depends, at least in part, on the ability of the active site inhibitor to hinder antithrombin-dependent FXa inactivation, paradoxically allowing uninhibited FXa to persist in plasma. Because of its inherent catalytic activity, FXa(I16L) is more potent (by >50-fold) in the hemostasis models tested than a noncatalytic antidote that is currently in clinical development. FXa(I16L) also reduces the anticoagulant-associated bleeding in vivo that is induced by the thrombin inhibitor dabigatran. FXa(I16L) may be able to fill an important unmet clinical need for a rapid, pro-hemostatic agent to reverse the effects of several new anticoagulants.

Reversing the Effect of Oral Anticoagulant Drugs: Established and Newer Options

The vitamin K antagonists (VKAs) have been the standard (and only) oral anticoagulants used for the long-term treatment or prevention of venous thromboembolism or stroke in patients with atrial fibrillation. The coagulopathy induced by VKAs can be reversed with vitamin K, and in urgent situations, the vitamin K-dependent coagulation factors can be replaced by transfusion. In the last decade, a new class of oral anticoagulants has been developed, direct oral anticoagulants that bind to a specific coagulation factor and neutralize it. These compounds were shown to be effective and safe compared with the VKAs and were licensed for specific indications, but without a specific reversal agent. The absence of a reversal agent is a barrier to more widespread use of these agents. Currently, for the management of major life-threatening bleeding with the direct oral anticoagulants, most authorities recommend the use of four factor prothrombin complex concentrates. There are now three reversal agents in development and poised to enter the market. Idarucizumab is a specific antidote targeted to reverse the direct thrombin inhibitor, dabigatran, which was recently approved for use in the USA. Andexanet alfa is an antidote targeted to reverse the oral direct factor Xa inhibitors as well as the indirect inhibitor enoxaparin. Ciraparantag is an antidote targeted to reverse the direct thrombin and factor Xa inhibitors as well as the indirect inhibitor enoxaparin.

In vitro reversal of supratherapeutic rivaroxaban levels with coagulation factor concentrates

BACKGROUND

A bleeding patient undergoing therapy with new oral anticoagulants is every clinician's nightmare as no specific reversal agent is available yet. This in vitro study investigated the effect of prothrombin complex concentrate (PCC), recombinant activated factor VII (rFVIIa) and activated prothrombin complex concentrate (aPCC) on supratherapeutic rivaroxaban concentrations using standard laboratory parameters (prothrombin time [PT], activated partial thromboplastin time [aPTT] and PT ratio) and thromboelastometry (clotting time [CT]).

MATERIALS AND METHODS

Blood samples from 10 healthy volunteers were collected and spiked with a supratherapeutic dose of rivaroxaban. Afterwards PCC, rFVIIa and aPCC were added in two doses. The laboratory parameters were measured and thromboelastometry was performed.

RESULTS

The addition of the reversal agents had the following statistically significant effects (all p<0.01): +25 IU/kg PCC: CT -15 s, aPTT +5 s; +50 IU/kg PCC: aPTT +11 s; +90 μg rFVIIa: CT -141 s; +25 IU/kg aPCC: CT -142 s, aPTT -9 s, PT ratio +14%, PT -10.5 s; +50 IU/kg aPCC: CT -118 s, aPTT -7 s, PT ratio +17%, PT -12.2 s.

DISCUSSION

rFVIIa and aPCC, but not PCC, appear to shorten coagulation times significantly in standard laboratory and thromboelastometry assays. These results need confirmation through evaluation of these agents in the clinical setting.

Management of Periprocedural and Early Pericardial Effusions With Tamponade Following Ablation of Atrial Fibrillation With Uninterrupted Factor Xa Inhibitors: A Case Series

INTRODUCTION

Because of the absence of a dedicated reversal agent, the outcome of pericardial effusion (PE) following procedures performed with uninterrupted apixaban or rivaroxaban is unknown. We report the characteristics of PEs presenting with tamponade in patients undergoing AF ablation with uninterrupted factor Xa inhibition (FXaI) to understand their management and prognosis.

METHODS AND RESULTS

We performed a multicenter cross-sectional survey in 10 centers across the United States. Patient data were obtained by chart review. In all patients the procedure was performed with uninterrupted FXaI. A total of 16 PEs requiring intervention were reported from 5 centers. Two patients were on apixaban 5 mg BD, the remaining on rivaroxaban 20 mg OD. Eleven PEs occurred in the periprocedural setting, and 5 PEs occurred from 1 to 28 days after the procedure. Pericardiocentesis and drainage were performed in all cases. Protamine and 4-factor prothrombin complex concentrate (4F-PCC) were given in all periprocedural cases. Two patients required surgery: in one case coagulation of the pericardial blood prevented effective drainage, and in the other bleeding was secondary to a steam pop-induced atrial tear. None of the postprocedural cases required FXaI reversal and the dose of rivaroxaban was temporarily reduced. No fatal outcomes or thromboembolic events were reported.

CONCLUSION

Pericardiocentesis and drainage with FXaI reversal proved effective in the management of acute PEs with tamponade occurring periprocedurally in patients undergoing AF ablation with uninterrupted FXaI. Early postprocedural effusions can be treated with pericardiocentesis without the need of a reversal agent.

Managing Subdural Bleeding Associated With Rivaroxaban: A Series of 3 Cases

OBJECTIVE

To report 3 cases of subdural bleeding associated with rivaroxaban managed by 3-factor prothrombin complex concentrate (PCC3).

CASE SUMMARIES

Case 1 presented with a 1-cm thick subdural hematoma (SDH) 12 hours after her last dose of rivaroxaban. Case 2 presented with a right 1-cm acute right SDH with 2 to 3 mm of midline shift 24 hours after his last dose of rivaroxaban. Case 3 presented with a 1.8-cm thick right cerebral convexity hematoma 12 hours after her last dose of rivaroxaban. All patients received 23 to 35 units/kg PCC3 with 1 to 3 units of fresh frozen plasm (FFP) and demonstrated no progression in lesions measured by repeat computed tomography (CT). Two patients were discharged to rehabilitation facilities and 1 patient ultimately died due to the location of the lesion.

DISCUSSION

Rivaroxaban has no specific antidote. Current bleeding management strategies are based on expert opinion. The risks and benefits for differing strategies are unclear, and no clinical experience has been reported to date. These cases begin to illuminate differences among choices for managing bleeding associated with Xa inhibitors.

CONCLUSION

In this case series, 25 to 35 units/kilogram PCC3 and FFP 1 to 3 units ceased rivaroxaban-associated bleeding without thrombogenic complications.

Managing target-specific oral anticoagulant associated bleeding including an update on pharmacological reversal agents

Target-specific oral anticoagulants (TSOACs) dabigatran, rivaroxaban and apixaban are approved for the prevention and treatment of thromboembolism in several clinical settings. Bleeding is the major complication of anticoagulant therapy, including TSOACs, and anticoagulant reversal strategies are highly desired for the management of anticoagulant-associated major bleeding in addition to maximum supportive care and procedural/surgical intervention. Unlike VKAs for which vitamin K and coagulation factor replacement with prothrombin complex concentrate (PCC) can restore hemostasis, there are no clinically available agents proven to reverse TSOAC anticoagulant effect and ameliorate TSOAC-related major bleeding. This narrative review critically evaluates the evidence for TSOAC reversal using non-specific reversal agents PCC, activated PCC (APCC) and recombinant activated factor VII (rVIIa) which have been assessed primarily using in vitro experiments, animal models and healthy human volunteers. Aripazine is a novel agent undergoing clinical development for non-specific anticoagulant reversal, including TSOACs. Data are presented regarding specific reversal agents idarucizumab (dabigatran) and andexanet alfa (oral factor Xa inhibitors) currently being evaluated in clinical trials. A practical approach to management of patients with TSOAC-associated bleeding is also provided. There is an urgent need for clinical studies that evaluate the efficacy and safety of reversal strategies for TSOAC-related major bleeding with assessment of clinical outcomes such as bleeding and mortality.

Case Report: Apixaban-Associated Gluteal Artery Extravasation Reversed With PCC3 Without FFP

Apixaban, an oral factor Xa inhibitor, has no commercially available assay to measure its activity and no specific antidote. To date, recommendations for managing bleeding associated with apixaban are based on studies with animal models and healthy volunteers (who do not have identified thrombogenic risk factors) and expert opinion. No clinical experience has been published in the literature. Ideally, apixaban would be reversed sufficiently to stop a perilous bleed without producing more thrombogenic risk than the patients' underlying risk factors. Three-factor prothrombin complex concentrate (PCC3) is the least thrombogenic among the suggested reversal agents. Fresh frozen plasma (FFP) is sometimes recommended to add to PCC3, but it adds considerable volume. We describe successful management of an active left gluteal arterial extravasation due to trauma and associated apixaban, in a patient with aortic stenosis and atrial fibrillation, by administration of PCC3 alone, without the added volume of FFP.

In vivo increase in thrombin generation by four-factor prothrombin complex concentrate in apixaban-treated healthy volunteers

BACKGROUND

Four-factor prothrombin complex concentrate (PCC) (Cofact; Sanquin Blood Supply) 50 IU kg(-1) increased thrombin generation beyond baseline values in healthy, rivaroxaban-treated subjects.

OBJECTIVE

To assess whether infusion with doses of 37.5 IU kg(-1) and 25 IU kg(-1) PCC reverses the anticoagulant effect of high-dose apixaban, another oral direct factor Xa inhibitor.

METHODS

In a randomized, double-blind, placebo-controlled, crossover study, six healthy subjects received twice-daily apixaban 10 mg for 3.5 days followed by a single bolus of 37.5 IU kg(-1) PCC, 25 IU kg(-1) PCC, or placebo. The primary outcome was the effect of PCC 15 min after infusion on thrombin generation (endogenous thrombin potential [ETP]); secondary outcomes were the immediate effect of PCC on prothrombin time (PT) and the effect of PCC as compared with placebo over a period of 24 h on ETP and PT.

RESULTS

Fifteen minutes after infusion of 37.5 IU kg(-1) and 25 IU kg(-1) PCC, ETP increased from 41% ± 11% to 56% ± 23% (P = 0.06) and from 44% ± 12% to 51% ± 15% (P = 0.03), respectively. ETP significantly differed over time between 37.5 IU kg(-1) PCC and placebo during 24 h after infusion (P < 0.01). Both PCC doses restored apixaban-induced PT prolongation after 15 min (P < 0.01), and this was sustained over a period of 24 h.

CONCLUSION

Both 37.5 IU kg(-1) PCC and 25 IU/kg PCC improved coagulation parameters in healthy subjects, suggesting partial reversal of the anticoagulant effect of apixaban. This implies that PCC might be considered in patients with apixaban-associated bleeding. However, ETP was not immediately restored to pre-apixaban levels, suggesting that these doses are too low to instantly and fully restore hemostasis at peak apixaban levels.

Factor Xa inhibitors: a novel therapeutic class for the treatment of nonvalvular atrial fibrillation

Atrial fibrillation is the most common cause of stroke. Treatment with anticoagulants in patients with atrial fibrillation reduces embolic complications of the disease including stroke. However, the commonly used anticoagulant has a narrow therapeutic index, requires routine monitoring, and has numerous drug and food interactions leading to less than optimal rates of adherence. Inhibition of clotting factor Xa has been evaluated as a potential target for anticoagulation therapy with the hypothesis that using target-specific therapy will alleviate some of the dosing variability observed with the vitamin K antagonist. Three factor Xa inhibitors are currently indicated for use in nonvalvular atrial fibrillation. Similar to the vitamin K antagonist, warfarin, all of the factor Xa inhibitors are administered orally. Rivaroxaban and edoxaban are dosed once daily while apixaban is dosed twice daily. All three agents have demonstrated noninferiority when compared with current standard treatment with warfarin for efficacy and safety outcomes. The therapeutic dose of factor Xa inhibitors vary based on renal function. Unlike warfarin, there are no currently available antidotes for the factor Xa inhibitors although this is an area of interest for current and future studies. In the event of a life-threatening bleed there are established management strategies to reverse the bleeding effects of the factor Xa inhibitors.

Direct oral anticoagulants: new drugs and new concepts

Direct oral anticoagulants (DOACs) are approved for multiple thromboembolic disorders and provide advantages over existing agents. As with all anticoagulants, management protocols for the eventuality of bleeding are important. Randomized phase III studies generally show that DOACs have a similar risk of clinically relevant bleeding compared with standard anticoagulants, with reductions in major bleeding in some cases. This may be particularly important in patients with atrial fibrillation, for whom the rate of intracranial hemorrhage was approximately halved with DOACs compared with warfarin. Conversely, the risk of gastrointestinal bleeding may be increased. Specific patient characteristics, such as renal impairment, comedications, and particular aspects of each drug, including the proportion eliminated by the kidneys, must be taken into account when assessing the risk of bleeding. Although routine coagulation monitoring of DOACs is not required, it may be useful under some circumstances. Of the traditional clotting assays, a sensitive and calibrated prothrombin time may be useful for detecting the presence or absence of clinically relevant factor Xa inhibitor concentrations (rivaroxaban or apixaban), but specific anti-factor Xa assays can measure drug levels quantitatively. For dabigatran, the results of an activated partial thromboplastin time test may exclude a clinically relevant pharmacodynamic effect, but a calibrated dilute thrombin time assay can be used for quantification of drug levels. In the event of mild or moderate bleeding, normal hemostatic support measures are recommended. For life-threatening bleeding, use of nonspecific prohemostatic agents may be considered, although clinical evidence is scarce. Specific antidotes are in development.

Monitoring the Effects and Antidotes of the Non-vitamin K Oral Anticoagulants

In the last decade, we have witnessed the emergence of the oral non-vitamin K oral anticoagulants (NOACs), which have numerous advantages compared with the vitamin K antagonists, particularly their lack of need for monitoring; as a result their use is increasing. Nonetheless, the NOACs face two major challenges: the need for reliable laboratory assays to assess their anticoagulation effect, and the lack of approved antidotes to reverse their action. This article provides an overview of monitoring the anticoagulant effect of NOACs and their potential specific antidotes in development.

Reversal Strategies for Intracranial Hemorrhages in Patients Taking Oral Factor Xa Inhibitors

Factor Xa (fXa) inhibitors are becoming more common in clinical practice due to a variety of reasons. Unfortunately, limited data are currently available on the safe and efficacious reversal of these agents. This series presents 3 patient cases of intracranial hemorrhage and illustrates the observed effect of different methodologies undertaken in an attempt to reverse the fXa inhibitors implicated. Additionally, a brief review of the current available literature in reversal strategies is provided. The appropriate reversal for fXa inhibitors at this time is unknown. The cases described indicate that the administration of fresh frozen plasma and 4-factor prothrombin complex concentrate may provide minimal benefit in reversing the coagulation abnormalities caused by fXa inhibitors. However, in a life-threatening situation, the addition of these agents should be considered to prevent further progression of the bleed.

Practical management of bleeding in patients receiving non-vitamin K antagonist oral anticoagulants

Non-vitamin K antagonist oral anticoagulants (NOACs) are increasingly used in the prevention and treatment of venous thromboembolism and in the prevention of stroke in patients with non-valvular atrial fibrillation. In phase III clinical trials and meta-analyses, the NOACs were at least as effective as vitamin K antagonists (VKAs) and were associated with a similar or lower incidence of major bleeding, including consistent and significant decreases in intracranial bleeding, although with an increase in gastrointestinal bleeding for some agents compared with VKAs. Subsequent real-world evidence supports these outcomes. Despite this, physicians have concerns about serious bleeding or emergencies because there are no specific reversal agents for the NOACs. However, in clinical trials, patients receiving NOACs generally had similar or better outcomes after these events than those taking VKAs. As with any bleeding, anticoagulant-related bleeding should first be stratified according to severity and location; risk can be minimised by ongoing assessment. Management protocols for NOAC-related bleeding are similar to those for VKAs but should take into account the pharmacological profile of the specific drug. Because of their short half-lives, NOAC-related mild bleeding can often be controlled by temporarily withholding treatment. More severe bleeding requires standard escalating haemodynamic support measures, and non-specific reversal agents can be considered in life-threatening situations, based on limited clinical data. Specific and rapid reversal agents are not currently available for any oral anticoagulant and restoration of coagulation may not necessarily lead to better outcomes. Nevertheless, specific NOAC reversal agents are in development and show promise in healthy volunteers.

Reversal of rivaroxaban anticoagulation by nonactivated prothrombin complex concentrate in urgent surgery

Rivaroxaban is a once-daily oral anticoagulant currently indicated for the prevention of stroke and systemic embolism in patients with nonvalvular atrial fibrillation. It is also indicated for the prevention and treatment of venous or pulmonary thromboembolism. Despite the known advantages of rivaroxaban over standard therapy, this treatment is not exempt from bleeding. We present the case of a 51-year-old woman with arterial hypertension and paroxysmal atrial fibrillation anticoagulated with rivaroxaban 20 mg o.d. Patient was admitted to the emergency department because of intense abdominal pain, high temperature, hypotension, tachycardia and a big tumor in the right abdominal area. The ultrasonic exam showed a big collection in the thoracic and abdominal area, compatible with hematoma. Due to clinical instability, urgent surgery was required. Based on the results of coagulation parameters (PT: 17.5 s), the time from the last rivaroxaban dose was taken, and the patient weight, nonactivated prothrombin complex concentrate at a single dose of 1000 IU was administrated intravenously 1 h before the surgery. PT value decreased to normal value (13.5 s), and surgery was performed without any bleeding complication. The management of patients treated with rivaroxaban who require urgent surgery is discussed in this report.

Antidotes for novel oral anticoagulants: current status and future potential

The direct thrombin inhibitor dabigatran and the anti-Xa agents rivaroxaban, edoxaban, and apixaban are a new generation of oral anticoagulants. Their advantage over the vitamin K antagonists is the lack of the need for monitoring and dose adjustment. Their main disadvantage is currently the absence of a specific reversal agent. Dabigatran's, unlike the anti-Xa agents, absorption can be reduced by activated charcoal if administered shortly after ingestion and it can be removed from the blood with hemodialysis. Prothrombin complex concentrate, activated prothrombin complex concentrate, and recombinant factor VIIa all show some activity in reversing the anticoagulant effect of these drugs but this is based on ex vivo, animal, and volunteer studies. It is unclear, which, if any, of these drugs is the most suitable for emergency reversal. Three novel molecules (idarucizumab, andexanet, and PER977) may provide the most effective and safest way of reversal. These agents are currently in premarketing studies.