BAY 59-7939: an oral, direct factor Xa inhibitor for the prevention of venous thromboembolism in patients after total knee replacement. A phase II dose-ranging study

The safety and efficacy of NOACs versus LMWH for thromboprophylaxis after THA or TKA: A systemic review and meta-analysis

The differences in the safety and efficacy of anticoagulation between different types of new oral anticoagulants(NOACs) and low molecular weight heparin(LMWH) are still controversial. The main purposes of this study were to analyze safety and efficacy of NOACs versus LMWH for thromboprophylaxis, and perform subgroup analyses stratified by individual NOACs and different populations after total hip arthroplasty (THA) or total knee arthroplasty (TKA). Literature search was performed in PubMed, EMBASE, Cochrane Library, CNKI and Wanfang databases until June 31, 2022. This systematic review and meta-analysis included 46 randomized controlled trials (RCT) with 39, 924 patients. We evaluated the safety and efficacy of thromboprophylaxis between LMWH and NOACs. NOACs were more effective in reducing deep vein thrombosis (DVT) (RR0.59; 95%CI 0.49-0.71) and adverse events (RR: 0.96; 95%CI: 0.93-0.99) than LMWH. The subgroup analyses for different anticoagulants revealed that rivaroxaban (RR:0.49; 95%CI:0.36-0.66), apixaban (RR: 0.54; 95%CI: 0.36-0.81) and edoxaban (RR:0.49; 95%CI: 0.32-0.75) have the lower risk of DVT than LMWH. Apixaban (RR:0.89; 95%CI: 0.80-1.00) had superior prevention of bleeding to LMWH. Edoxaban exhibited a lower risk of VTE (RR: 0.46; 95%CI: 0.33-0.65), advantage events (RR: 0.87; 95%CI: 0.82-0.93), and drug-related adverse events (DRAEs) (RR: 0.64; 95%CI: 0.53-0.76) than LMWH. East Asian population was superior to western population for preventing DVT, advantage events, and DRAE using NOACs. In conclusion, NOACs are more effective than LMWH at preventing DVT and adverse events after arthroplasty. Apixaban has lower bleeding than LMWH, and East Asian populations may benefit more than western population from NOACs.

Efficacy and safety of commonly used thromboprophylaxis agents following hip and knee arthroplasty

Aims

We investigated the efficacy and safety profile of commonly used venous thromboembolism (VTE) prophylaxis agents following hip and knee arthroplasty.

Methods

A systematic search of PubMed, Embase, Cochrane Library, Web of Science, and OrthoSearch was performed. Prophylaxis agents investigated were aspirin (< 325 mg and ≥ 325 mg daily), enoxaparin, dalteparin, fondaparinux, unfractionated heparin, warfarin, rivaroxaban, apixaban, and dabigatran. The primary efficacy outcome of interest was the risk of VTE, whereas the primary safety outcomes of interest were the risk of major bleeding events (MBE) and wound complications (WC). VTE was defined as the confirmed diagnosis of any deep vein thrombosis and/or pulmonary embolism. Network meta-analysis combining direct and indirect evidence was performed. Cluster rank analysis using the surface under cumulative ranking (SUCRA) was applied to compare each intervention group, weighing safety and efficacy outcomes.

Results

Of 86 studies eligible studies, cluster rank analysis showed that aspirin < 325 mg daily (SUCRA-VTE 89.3%; SUCRA-MBE 75.3%; SUCRA-WC 71.1%), enoxaparin (SUCRA-VTE 55.7%; SUCRA-MBE 49.8%; SUCRA-WC 45.2%), and dabigatran (SUCRA-VTE 44.9%; SUCRA-MBE 52.0%; SUCRA-WC 41.9%) have an overall satisfactory efficacy and safety profile.

Conclusion

We recommend the use of either aspirin < 325 mg daily, enoxaparin, or dabigatran for VTE prophylaxis following hip and knee arthroplasty.

Antithrombotic prophylaxis following total knee arthroplasty: a level I Bayesian network meta-analysis

INTRODUCTION

Venous thromboembolism (VTE) is a major concern following total knee arthroplasty (TKA). The optimal pharmacological prophylaxis remains, however, controversial. The present investigation compared several non-vitamin K antagonist oral anticoagulants commonly employed as VTE prophylaxis following TKA. A Bayesian network meta-analysis was conducted to compare apixaban, aspirin, dabigatran, edoxaban, enoxaparin, fondaparinux, and rivaroxaban. The outcomes of interest were to compare the rate of deep venous thrombosis (DVT), pulmonary embolism (PE), and major and minor haemorrhages.

METHODS

This study was conducted according to the PRISMA Extension Statement for Reporting of Systematic Reviews Incorporating Network Meta-Analyses of Health Care Interventions. In March 2024, PubMed, Web of Science, and Google Scholar were accessed with no time constraints. All randomised controlled trials (RCTs) comparing two or more drugs for the prevention of VTE following TKA were considered for inclusion.

RESULTS

Data from 29,678 patients were collected. Of them, 67% (19,884 of 29,678 patients) were women. The mean age of the patients was 66.8 ± 2.8 years, and the mean BMI was 29.2 ± 1.5 kg/m2. There was comparability in age, sex, and BMI at baseline. Apixaban 5 mg, dabigatran 220 mg, and rivaroxaban 10 mg were the most effective in reducing the rate of DVT. Apixaban 5 mg, enoxaparin 60 mg, and rivaroxaban 40 mg were the most effective in reducing the rate of PE. Apixaban 5 mg, rivaroxaban 10 mg, and apixaban 10 mg were associated with the lowest rate of major haemorrhages. Apixaban 5 mg and 20 mg, and dabigatran 220 mg were associated with the lowest rate of minor haemorrhages.

CONCLUSION

Administration of apixaban 5 mg demonstrated the best balance between VTE prevention and haemorrhage control following TKA.

LEVEL OF EVIDENCE

Level I, network meta-analysis of RCTs.

Risks of major bleeding and venous thromboembolism in patients undergoing total hip or total knee arthroplasty using therapeutic dosages of DOACs

About 1.5% of patients undergoing total hip (THA) or total knee arthroplasty (TKA) still develop postoperative venous thromboembolism (VTE), indicating that the current thromboprophylaxis strategy is not optimal. To evaluate the feasibility of therapeutic dosages of direct oral anticoagulants (DOACs) as thromboprophylaxis for high VTE risk patients, we determined the risks of major bleeding and VTE in patients who underwent THA/TKA and were treated with DOACs in therapeutic dosages for atrial fibrillation (AF). We conducted a registry-based cohort study from 2010 to 2018 in Denmark and included AF patients on therapeutic DOACs dose who underwent THA/TKA. AF patients were utilized as proxy since they have a life-long indication for therapeutic anticoagulant medication. The 49-days cumulative incidence (with death as competing risk) of major bleeding was assessed. The same was done for VTE at 49- and 90-days. 1,354 THA and TKA procedures were included. The 49-days cumulative incidence of major bleeding was 1.40% (95%Confidence Interval[CI] 0.88-2.14%). Most bleeding events occurred at the surgical site. The cumulative incidence of VTE at 49-days was 0.59% (95%CI 0.28-1.13%) and 0.74% (95%CI 0.38-1.32%) at 90-days. The incidence of major bleeding in THA/TKA patients on DOACs in therapeutic dosages was in line with previously reported incidences among THA/TKA patients on thromboprophylaxis dosages, while the incidence of VTE was relatively low. These data provide a solid basis for the design of randomized controlled trials to establish the safety and efficacy of therapeutic dosages of DOACs to prevent VTE in high-risk patients.

Pharmacotherapy for Venous Thromboprophylaxis following Total Hip or Knee Arthroplasty: A Systematic Review and Network Meta-analysis

The optimal pharmacological prophylaxis for venous thromboembolism (VTE) after hip or knee arthroplasty is uncertain. We conducted a systematic review and network meta-analysis to compare the efficacy and safety of various medications. We searched multiple databases for randomized clinical trials (RCTs) comparing medications (including factor Xa inhibitors, factor IIa inhibitor, warfarin, unfractionated heparin [UFH], low-molecular-weight heparin [LMWH], aspirin, pentasaccharide) for VTE prophylaxis post-arthroplasty. Outcomes included any postoperative VTE identified with screening, major bleeding, and death. We used LMWH as the main comparator for analysis and performed trial sequential analysis (TSA) for each pairwise comparison. Certainty of evidence was assessed using GRADE (Grading of Recommendations, Assessments, Developments and Evaluations). We analyzed 70 RCTs (55,841 participants). Factor Xa inhibitors decreased postoperative VTE significantly compared with LMWH (odds ratio [OR]: 0.55, 95% confidence interval [CI]: 0.44-0.68, high certainty). Pentasaccharides probably reduce VTE (OR: 0.61, 95% CI: 0.36-1.02, moderate certainty), while the factor IIa inhibitor dabigatran may reduce VTE (OR: 0.75, 95% CI: 0.40-1.42, low certainty). UFH probably increases VTE compared with LMWH (OR: 1.31, 95% CI: 0.91-1.89, moderate certainty), and other agents like warfarin, aspirin, placebo, and usual care without thromboprophylaxis increase VTE (high certainty). Factor Xa inhibitors may not significantly affect major bleeding compared with LMWH (OR: 1.06, 95% CI: 0.81-1.39, low certainty). No medications had a notable effect on mortality compared with LMWH (very low certainty). TSA suggests sufficient evidence for the benefit of factor Xa inhibitors over LMWH for VTE prevention. Compared with LMWH and aspirin, factor Xa inhibitors are associated with reduced VTE after hip or knee arthroplasty, without an increase in bleeding and likely no impact on mortality.

Efficacy and Safety of Different Doses of Rivaroxaban and Risk Factors for Bleeding in Elderly Patients with Venous Thromboembolism: A Real-World, Multicenter, Observational, Cohort Study

INTRODUCTION

Venous thromboembolism (VTE) consists of deep vein thrombosis (DVT) and pulmonary embolism (PE). Rivaroxaban is a direct oral anticoagulant (DOAC) inhibiting activated coagulation factor X (FXa), and exerts several advantages in the treatment of VTE compared to conventional therapy. However, the efficacy and safety of rivaroxaban in elderly patients with VTE was still poorly understood.

METHODS

The study was carried out using an observational and non-interventional approach. A total of 576 patients aged ≥ 60 years with newly diagnosed VTE were included in the study. All patients received rivaroxaban with recommended treatment duration of ≥ 3 months for secondary prevention. In addition, 535 elderly patients with various diseases except VTE were included in the study in a retrospective and randomized way.

RESULTS

The total bleeding rate was 12.2% (70/576). Major bleeding and non-major clinically relevant (NMCR) bleeding occurred in 4 (0.69%) patients and 5 (0.87%) patients, respectively. The rate of recurrent VTE was 5.4%. The mean level of D-dimers was increased by 467.2% in the elderly patients with VTE compared with the elderly patients without VTE. The elderly patients with VTE receiving rivaroxaban at a dose of 10 mg once daily (n = 134) had lower risk for bleeding (3.7% vs 14.7%; P = 0.001) and a similar rate of recurrent VTE (4.5% vs 5.7%; P = 0.596) as compared to the elderly patients with VTE receiving rivaroxaban at higher doses including 15 mg once daily and 20 mg once daily (n = 442). In addition, age, concomitant aspirin, hemoglobin, activated partial thromboplastin time (APTT), and rivaroxaban doses were independent predictive factors for bleeding events.

CONCLUSIONS

The study suggested that a dose of 10 mg once daily should be the priority in elderly patients with VTE receiving long-term rivaroxaban anticoagulation therapy in view of reduced bleeding risk.

Venous Thromboembolism Prophylaxis in Major Orthopedic Surgeries and Factor XIa Inhibitors

Venous thromboembolism (VTE), comprising pulmonary embolism (PE) and deep vein thrombosis (DVT), poses a significant risk during and after hospitalization, particularly for surgical patients. Among various patient groups, those undergoing major orthopedic surgeries are considered to have a higher susceptibility to PE and DVT. Major lower-extremity orthopedic procedures carry a higher risk of symptomatic VTE compared to most other surgeries, with an estimated incidence of ~4%. The greatest risk period occurs within the first 7-14 days following surgery. Major bleeding is also more prevalent in these surgeries compared to others, with rates estimated between 2% and 4%. For patients undergoing major lower-extremity orthopedic surgery who have a low bleeding risk, it is recommended to use pharmacological thromboprophylaxis with or without mechanical devices. The choice of the initial agent depends on the specific surgery and patient comorbidities. First-line options include low-molecular-weight heparins (LMWHs), direct oral anticoagulants, and aspirin. Second-line options consist of unfractionated heparin (UFH), fondaparinux, and warfarin. For most patients undergoing knee or hip arthroplasty, the initial agents recommended for the early perioperative period are LMWHs (enoxaparin or dalteparin) or direct oral anticoagulants (rivaroxaban or apixaban). In the case of hip fracture surgery, LMWH is recommended as the preferred agent for the entire duration of prophylaxis. However, emerging factor XI(a) inhibitors, as revealed by a recent meta-analysis, have shown a substantial decrease in the occurrence of VTE and bleeding events among patients undergoing major orthopedic surgery. This discovery poses a challenge to the existing paradigm of anticoagulant therapy in this specific patient population and indicates that factor XI(a) inhibitors hold great promise as a potential strategy to be taken into serious consideration.

Rivaroxaban versus nadroparin for thromboprophylaxis following thoracic surgery for lung cancer: A randomized, noninferiority trial

The benefit of rivaroxaban in thromboprophylaxis after oncologic lung surgery remains unknown. To evaluate the efficacy and safety of rivaroxaban, patients who underwent thoracic surgery for lung cancer were enrolled, and randomly assigned to rivaroxaban or nadroparin groups in a 1:1 ratio; anticoagulants were initiated 12-24 h after surgery and continued until discharge. Four hundred participants were required according to a noninferiority margin of 2%, assuming venous thromboembolism (VTE) occurrence rates of 6.0% and 12.6% for patients in the rivaroxaban and nadroparin groups, respectively. The primary efficacy outcome was any VTE during the treatment and 30-day follow-up periods. The safety outcome was any on-treatment bleeding event. Finally, 403 patients were randomized (intention-to-treat [ITT] population), with 381 included in per-protocol (PP) population. The primary efficacy outcomes occurred in 12.5% (25/200) of the rivaroxaban group and 17.7% (36/203) of the nadroparin group (absolute risk reduction, -5.2%; 95% confidence interval [CI], [-12.2-1.7]), indicating the noninferiority of rivaroxaban in ITT population. Sensitivity analysis was performed in the PP population and yielded similar results, confirming the noninferiority of rivaroxaban. In the safety analysis population, the incidence of any on-treatment bleeding events did not differ significantly between the groups (12.2% for rivaroxaban vs. 7.0% for nadroparin; relative risk [RR], 1.9; 95% CI, [0.9-3.7]; p = .08), including major bleeding (9.7% vs. 6.5%; RR, 1.6 [95% CI, 0.9-3.7]; p = .24), and nonmajor bleeding (2.6% vs. 0.5%; RR, 5.2 [95% CI, 0.6-45.2]; p = .13). Rivaroxaban for thromboprophylaxis after oncologic lung surgery was shown to be noninferior to nadroparin.

Statistical Fragility of Venous Thromboembolism Prophylaxis Following Total Joint Arthroplasty

Background

Statistical fragility is a quantitative measure of the robustness of the statistical conclusions drawn in a study. Although statistical fragility has been comprehensively evaluated in the arthroplasty literature, the statistical fragility of large-scale randomized trials evaluating venous thromboembolism (VTE) prophylaxis has not been evaluated. The purpose of this study was to determine the utility of applying the fragility index (FI) and the fragility quotient (FQ) analysis to randomized controlled trials (RCTs) evaluating VTE prophylaxis following total joint arthroplasty.

Methods

A systematic review was performed by searching multiple databases to identify RCTs that evaluated VTE prophylaxis following total joint arthroplasty from 2000 to 2020. The FI was determined by manipulating each reported dichotomous outcome event until a reversal of significance was appreciated with 2 × 2 contingency tables. The associated FQ was determined by dividing the FI by the sample size.

Results

Thirty-two RCTs were ultimately included for analysis. The overall FI incorporating all 32 RCTs was only 7 (interquartile range 3-9), suggesting that the reversal of only 7 events is required to change study significance. The associated FQ was determined to be 0.01. Of the RCTs that reported lost-to-follow-up data, the majority of studies had lost-to-follow-up numbers greater than 7.

Conclusions

Our findings suggest that RCTs evaluating VTE prophylaxis following total hip arthroplasty and total knee arthroplasty may lack statistical stability as few outcome events are required to reverse the significance of outcomes. Future randomized trials should consider reporting FI and FQ along with the P value analysis to provide better context to the integrity of statistical stability.

Joint 2022 European Society of Thoracic Surgeons and The American Association for Thoracic Surgery guidelines for the prevention of cancer-associated venous thromboembolism in thoracic surgery

BACKGROUND

Venous thromboembolism (VTE), which includes deep vein thrombosis and pulmonary embolism, is a potentially fatal but preventable postoperative complication. Thoracic oncology patients undergoing surgical resection, often after multimodality induction therapy, represent among the highest risk groups for postoperative VTE. Currently there are no VTE prophylaxis guidelines specific to these thoracic surgery patients. Evidenced-based recommendations will help clinicians manage and mitigate risk of VTE in the postoperative period and inform best practice.

OBJECTIVE

These joint evidence-based guidelines from The American Association for Thoracic Surgery and the European Society of Thoracic Surgeons aim to inform clinicians and patients in decisions about prophylaxis to prevent VTE in patients undergoing surgical resection for lung or esophageal cancer.

METHODS

The American Association for Thoracic Surgery and the European Society of Thoracic Surgeons formed a multidisciplinary guideline panel that included broad membership to minimize potential bias when formulating recommendations. The McMaster University GRADE Centre supported the guideline development process, including updating or performing systematic evidence reviews. The panel prioritized clinical questions and outcomes according to their importance for clinicians and patients. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used, including GRADE Evidence-to-Decision frameworks, which were subject to public comment.

RESULTS

The panel agreed on 24 recommendations focused on pharmacological and mechanical methods for prophylaxis in patients undergoing lobectomy and segmentectomy, pneumonectomy, and esophagectomy, as well as extended resections for lung cancer.

CONCLUSIONS

The certainty of the supporting evidence for the majority of recommendations was judged as low or very low, largely due to a lack of direct evidence for thoracic surgery. The panel made conditional recommendations for use of parenteral anticoagulation for VTE prevention, in combination with mechanical methods, over no prophylaxis for cancer patients undergoing anatomic lung resection or esophagectomy. Other key recommendations include: conditional recommendations for using parenteral anticoagulants over direct oral anticoagulants, with use of direct oral anticoagulants suggested only in the context of clinical trials; conditional recommendation for using extended prophylaxis for 28 to 35 days over in-hospital prophylaxis only for patients at moderate or high risk of thrombosis; and conditional recommendations for VTE screening in patients undergoing pneumonectomy and esophagectomy. Future research priorities include the role of preoperative thromboprophylaxis and the role of risk stratification to guide use of extended prophylaxis.

Clinical Evaluation of Factor XIa Inhibitor Drugs: JACC Review Topic of the Week

Factor XI/XIa (FXI/FXIa) represents a potential target for improved precision in anticoagulation because it is involved primarily in thrombus formation and plays a much smaller role in clotting and hemostasis. This suggests that the inhibition of FXI/XIa could prevent pathologic thrombi from forming, but largely preserve a patient's ability to clot in response to bleeding or trauma. This theory is supported by observational data showing that patients with congenital FXI deficiency have lower rates of embolic events without an increase in spontaneous bleeding. Small phase 2 trials of FXI/XIa inhibitors have offered encouraging data with regard to bleeding and safety and evidence of efficacy for the prevention of venous thromboembolism. However, larger clinical trials across multiple patient groups are needed for this emerging class of anticoagulants to understand their possible role in clinical use. Here we review the potential clinical indications for FXI/XIa inhibitors, data available to date, and consider future trials.

Efficacy of 11 anticoagulants for the prevention of venous thromboembolism after total hip or knee arthroplasty: A systematic review and network meta-analysis

BACKGROUND

To systematically review the efficacy of 11 anticoagulants in the treatment of venous thromboembolism (VTE) after total hip or knee arthroplasty.

METHODS

PubMed, Cochrane Library, Embase, Web of Science, China National Knowledge Infrastructure, Wanfang Data, VIP, and China Biology Medicine databases were electronically searched for studies assessing the efficacy of different anticoagulants for the prevention of VTE after total hip or knee arthroplasty from January 1, 2010, to January 27, 2022. Two reviewers independently screened the literature, extracted data, and graded the evidence using Confidence in Network Meta-Analysis. The network meta-analysis was then performed using Stata 16.0 software and R 4.1.0 software.

RESULTS

A total of 61 articles were included. The results of network meta-analysis showed that apixaban, edoxaban, fondaparinux, rivaroxaban, and darexaban were the most effective anticoagulants for the prevention of deep vein thrombosis in patients undergoing total hip or knee arthroplasty (P < .05), while there was no difference in the efficacy among the anticoagulants for the prevention of pulmonary embolism (P > .05).

CONCLUSION

Apixaban, edoxaban, fondaparinux, rivaroxaban, and darexaban have the best efficacy for the prevention of VTE after total hip or knee arthroplasty.

Joint 2022 European Society of Thoracic Surgeons and The American Association for Thoracic Surgery guidelines for the prevention of cancer-associated venous thromboembolism in thoracic surgery

BACKGROUND

Venous thromboembolism (VTE), which includes deep vein thrombosis and pulmonary embolism, is a potentially fatal but preventable postoperative complication. Thoracic oncology patients undergoing surgical resection, often after multimodality induction therapy, represent among the highest risk groups for postoperative VTE. Currently there are no VTE prophylaxis guidelines specific to these thoracic surgery patients. Evidenced-based recommendations will help clinicians manage and mitigate risk of VTE in the postoperative period and inform best practice.

OBJECTIVE

These joint evidence-based guidelines from The American Association for Thoracic Surgery and the European Society of Thoracic Surgeons aim to inform clinicians and patients in decisions about prophylaxis to prevent VTE in patients undergoing surgical resection for lung or esophageal cancer.

METHODS

The American Association for Thoracic Surgery and the European Society of Thoracic Surgeons formed a multidisciplinary guideline panel that included broad membership to minimize potential bias when formulating recommendations. The McMaster University GRADE Centre supported the guideline development process, including updating or performing systematic evidence reviews. The panel prioritized clinical questions and outcomes according to their importance for clinicians and patients. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used, including GRADE Evidence-to-Decision frameworks, which were subject to public comment.

RESULTS

The panel agreed on 24 recommendations focused on pharmacological and mechanical methods for prophylaxis in patients undergoing lobectomy and segmentectomy, pneumonectomy, and esophagectomy, as well as extended resections for lung cancer.

CONCLUSIONS

The certainty of the supporting evidence for the majority of recommendations was judged as low or very low, largely due to a lack of direct evidence for thoracic surgery. The panel made conditional recommendations for use of parenteral anticoagulation for VTE prevention, in combination with mechanical methods, over no prophylaxis for cancer patients undergoing anatomic lung resection or esophagectomy. Other key recommendations include: conditional recommendations for using parenteral anticoagulants over direct oral anticoagulants, with use of direct oral anticoagulants suggested only in the context of clinical trials; conditional recommendation for using extended prophylaxis for 28 to 35 days over in-hospital prophylaxis only for patients at moderate or high risk of thrombosis; and conditional recommendations for VTE screening in patients undergoing pneumonectomy and esophagectomy. Future research priorities include the role of preoperative thromboprophylaxis and the role of risk stratification to guide use of extended prophylaxis. (J Thorac Cardiovasc Surg 2022;▪:1-31).

Pharmacotherapy for pulmonary embolism: new anticoagulants

Background: Pulmonary embolism is associated with reduced survival and considerable economic burden worldwide. In Korea, the incidence of pulmonary embolism has been gradually increasing. Older individuals are at an increased risk for pulmonary embolism and anticoagulation-related bleeding events. Typically, heparin and vitamin K antagonists are employed to treat pulmonary embolism; however, these agents present numerous limitations. Hence, novel anticoagulants with improved safety and efficacy profiles are urgently needed.Current Concepts: Direct oral anticoagulants (DOACs), including direct thrombin (coagulation factor II) inhibitors and selective inhibitors of coagulation factor Xa, have emerged as alternative agents. Phase III, large-scale clinical trials have revealed that DOACs are non-inferior to standard therapy during initial and long-term treatment of pulmonary embolism, considering the safety profile. Evidence-based clinical guidelines recommend that primary care clinicians employ DOACs over warfarin to achieve anticoagulation.Discussion and Conclusion: For over 70 years, the standard therapy for most patients with pulmonary embolism has involved heparin administration, overlapped and followed by a vitamin K antagonist. Recently developed DOACs against coagulation factor Xa or thrombin might overcome limitations of standard therapy, including the need for injection and regular dose adjustment with laboratory monitoring. These limitations hinder the management of patients with pulmonary embolism and negatively impact the patient’s quality of life. Four DOACs, including apixaban, dabigatran, edoxaban, and rivaroxaban, are currently available for treating pulmonary embolism in Korea, which could simplify the therapeutic strategy.

Role of Direct Oral Anticoagulants for Post-operative Venous Thromboembolism Prophylaxis

Venous thromboembolism (VTE) is one of the leading causes of post-operative morbidity and mortality. Over previous decades, heparin and warfarin were the predominant therapeutic options for post-operative thromboprophylaxis. However, their use is limited by drawbacks including a narrow therapeutic range, numerous food and drug interactions, and the need for regular monitoring for dose adjustments. Recently, direct oral anticoagulants (DOACs), such as dabigatran etexilate (a direct thrombin inhibitor) and apixaban, rivaroxaban and edoxaban (direct factor Xa inhibitors), have been developed to overcome these issues. DOACs have shown promising results in Phase III clinical trials for post-operative VTE prophylaxis. This review summarises the pharmacological profile of DOACs and highlights the use of DOACs in post-operative VTE prophylaxis based on the available clinical trial data.

The efficacy and cost-effectiveness of enoxaparin versus rivaroxaban in the prevention of venous thromboembolism following total hip or knee arthroplasty: A meta-analysis

INTRODUCTION

Thromboprophylaxis following total hip and knee arthroplasty is variable across institutions, but commonly consists of enoxaparin, and more recently rivaroxaban. We aimed to analyze the current evidence on the efficacy, safety and cost-effectiveness of rivaroxaban versus enoxaparin for thromboprophylaxis following TKA or THA.

METHODS

This study was conducted according to PRISMA guidelines. Electronic database searches were performed using three databases from their dates of inception to June 2020. Relevant randomized controlled studies were identified, with data extracted and analyzed.

RESULTS

From eight studies, 13,384 patients were included, with 5700 undergoing TKA and 7684 undergoing THA. There were 6629 patients receiving rivaroxaban and 6755 patients receiving enoxaparin. From the total cohort, rivaroxaban was associated with significantly lower rates of major VTE (p = 0.009) and DVT (p < 0.001) when compared to enoxaparin. There was no significant difference in bleeding complications between rivaroxaban and enoxaparin groups (p = 0.14). Subgroup analysis of patients undergoing THA demonstrated that rivaroxaban reduced risk of major VTE (p = 0.002) and DVT (p = 0.01) with no significant differences in any other complications. For those undergoing TKA, rivaroxaban significantly reduced the risk of DVT (p < 0.001) but was associated with higher rates of post-operative blood transfusion (p = 0.03). Cost-analysis revealed that rivaroxaban was superior to enoxaparin, with the medication cost needed to prevent one DVT being $1081 and $432 less with rivaroxaban for THA and TKA respectively.

CONCLUSIONS

Rivaroxaban may be a safe and cost-effective alternative to enoxaparin for routine thromboprophylaxis following total knee or hip arthroplasty.

Efficacy and Safety of Thromboprophylaxis Post-Orthopedic Surgery

Given the high risk of venous thromboembolism (VTE) post-orthopedic surgery and the vital role of thromboprophylaxis in preventing VTEs, this meta-analysis aimed to assess the efficacy of thromboprophylaxis post major orthopedic surgery and the relevant safety measures. In this review, we conducted a computer-aided search of Google Scholar, PubMed, CINAHL, Cochrane, Medline, and EMBASE databases. We included all published randomized clinical trials (RCTs) that utilized enoxaparin, fondaparinux, dabigatran, rivaroxaban, apixaban, and aspirin for VTE prophylaxis in patients undergoing total hip arthroplasty (THA), hip fracture surgery, and total knee arthroplasty (TKA) based on primary and secondary outcomes. The Cochrane Collaboration tool was used to evaluate the risk of bias. All statistical analyses were performed using Review Manager Software. A total of 23 RCTs were included with a total sample of 48,424 patients and an overall low risk of bias. The efficacy of enoxaparin in preventing VTEs in the TKA group was significantly better than fondaparinux. In the THA group, the efficacy of enoxaparin was significantly better than apixaban. The efficacies of fondaparinux, dabigatran, rivaroxaban, apixaban, and aspirin were comparable to that of enoxaparin in reducing VTE-associated mortality, major bleeding, and adverse events. In conclusion, we found that all included drugs were non-inferior to enoxaparin in VTE-associated mortality, major bleeding, and adverse events.

Dosing Regimen Prediction and Confirmation with Rivaroxaban for Thromboprophylaxis in Children after the Fontan Procedure: Insights from the Phase III UNIVERSE Study

Thrombosis remains an important complication for children with single ventricle physiology post-Fontan procedure and effective thromboprophylaxis is an important unmet medical need. To obviate conventional dose-finding studies and expedite clinical development, a rivaroxaban dose regimen for this indication was determined utilizing a model-informed drug development approach. A physiologically based pharmacokinetic (PBPK) rivaroxaban model was used to predict a pediatric dosing regimen that would produce drug exposures similar to that of 10 mg once daily in adults. This regimen was used in an open-label, multicenter Phase 3 study, which investigated the use of rivaroxaban for thromboprophylaxis in post-Fontan patients 2 to 8 years of age. The pharmacokinetics (PK) of rivaroxaban was assessed in Part A (n = 12) and in Part B (n = 64) of UNIVERSE. The safety and efficacy in the rivaroxaban group were compared to those in the acetylsalicylic acid group for 12 months. Pharmacodynamic endpoints were assessed in both parts of the study. Rivaroxaban exposures achieved in Part A and B were similar to the adult reference exposures. Prothrombin time also showed similarity to the adult reference. Exposure-response analysis did not identify a quantitative relationship between rivaroxaban exposures and efficacy/safety outcomes within the observed exposure ranges. A body-weight based dose regimen selected by PBPK modeling was shown in the UNIVERSE study to be appropriate for thromboprophylaxis in the post-Fontan pediatric population. Model-based dose selection can support pediatric drug development and bridge adult dose data to pediatrics, thereby obviating the need for dose-finding studies in pediatric programs. This article is protected by copyright. All rights reserved.

Efficacy and safety of anticoagulants for postoperative thrombophylaxis in total hip and knee arthroplasty: A PRISMA-compliant Bayesian network meta-analysis

OBJECTIVE

To search, review, and analyze the efficacy and safety of various anticoagulants from randomized clinical trials (RCTs) of anticoagulants for THA and TKA.

DESIGN

PRISMA-compliant Bayesian Network Meta-analysis.

DATA SOURCES AND STUDY SELECTION

The databases of The Medline, Embase, ClinicalTrial, and Cochrane Library databases were searched until March 2017 for RCTs of patients undergoing a THA or TKA.

MAIN OUTCOMES AND MEASURES

The primary efficacy measurement was the venous thromboembolism Odds ratio (OR). The safety measurement was the odds ratio of major or clinically relevant bleeding. OR with 95% credibility intervals (95%CrIs) were calculated. Findings were interpreted as associations when the 95%CrIs excluded the null value.

RESULTS

Thirty-five RCTs (53787 patients; mean age range, mostly 55-70 years; mean weight range, mostly 55-90 kg; and a higher mean proportion of women than men, around 60%) included the following Anticoagulants categories: fondaparinux, edoxaban, rivaroxaban, apixaban, dabigatran, low-molecular-weight heparin, ximelagatran, aspirin, warfarin. Anticoagulants were ranked for effectiveness as follows: fondaparinux (88.89% ± 10.90%), edoxaban (85.87% ± 13.34%), rivaroxaban (86.08% ± 10.23%), apixaban (68.26% ± 10.82%), dabigatran (41.63% ± 12.26%), low-molecular-weight heparin (41.03% ± 9.60%), ximelagatran (37.81% ± 15.87%), aspirin (35.62% ± 20.60%), warfarin (9.89% ± 9.07%), and placebo (4.56% ± 6.37%). Ranking based on clinically relevant bleeding events was as follows: fondaparinux (14.53% ± 15.25%), ximelagatran (18.93% ± 17.49%), rivaroxaban (23.86% ± 15.14%), dabigatran (28.30% ± 14.18%), edoxaban (38.76% ± 24.25%), low-molecular-weight heparin (53.28% ± 8.40%), apixaban (71.81% ± 10.92%), placebo (76.26% ± 14.61%), aspirin (86.32% ± 25.74%), and warfarin (87.95% ± 11.27%). No statistically significant heterogeneity was observed between trials.

CONCLUSIONS AND RELEVANCE

According to our results, all anticoagulant drugs showed some effectiveness for VTE prophylaxis. Our ranking indicated that fondaparinux and rivaroxaban were safer and more effective than other anticoagulant drugs for patients undergoing THA or TKA.

Associations between model-predicted rivaroxaban exposure and patient characteristics and efficacy and safety outcomes in the prevention of venous thromboembolism

Anticoagulant plasma concentrations and patient characteristics might affect the benefit–risk balance of therapy. The study objective was to assess the impact of model-predicted rivaroxaban exposure and patient characteristics on outcomes in patients receiving rivaroxaban for venous thromboembolism (VTE) prophylaxis (VTE-P) after hip/knee replacement surgery. Post hoc exposure–response analyses were conducted using data from the phase 3 RECORD1–4 studies, in which 12,729 patients were randomized to rivaroxaban 10 mg once daily or enoxaparin for ≤ 39 days. Multivariate regression approaches were used to correlate model-predicted individual rivaroxaban exposures and patient characteristics with outcomes. In the absence of measured rivaroxaban exposure, exposure estimates were predicted based on individual increases in prothrombin time (PT) and by making use of the known correlation between rivaroxaban plasma concentration and dynamics of PT. No significant associations between rivaroxaban exposure and total VTE or major bleeding were identified. A significant association between exposure and a composite of major or non-major clinically relevant (NMCR) bleeding from day 4 after surgery was observed. The relationship was shallow, with an approximate predicted absolute increase in a composite of major or NMCR bleeding from 1.08 [95% confidence interval (CI) 0.76–1.54] to 2.18% (95% CI 1.51–3.17) at the 5th and 95th percentiles of trough plasma concentration, respectively. In conclusion, based on the underlying data and analysis, no reliable target window for exposure with improved benefit–risk could be identified within the investigated exposure range. Hence, monitoring rivaroxaban levels is unlikely to be beneficial in VTE-P.

Ranking the efficacy of anticoagulants for the prevention of venous thromboembolism after total hip or knee arthroplasty: A systematic review and a network meta-analysis

BACKGROUND

Anticoagulants are essential in the prevention of venous thromboembolism. However, the effectiveness and safety of different anticoagulants have always been controversial. Therefore, we aimed to expand the sample of anticoagulant results and rank the efficacy and safety of 19 anticoagulants in the prevention of venous thromboembolism when total knee or total hip arthroplasty procedure is performed.

METHODS

A systematic review and network meta-analysis of randomized trials of adult patients undergoing total hip or knee arthroplasty were conducted. The trials were identified from PubMed, Web of Science, Cochrane Library, and Embase databases, in which anticoagulants were used as interventions randomized controlled trial. The incidence of venous embolism and bleeding are the key outcomes of assessing the efficacy of intervention drugs. We used the Physical Therapy Evidence Database (PEDro) to assess risk bias and used pairwise comparison and network meta-analysis with random effects to estimate the summary relative risk. The study has been registered with PROSPERO, number CRD42020200747.

RESULTS

From the 4083 identified manuscripts, 45,067 participants from 53 randomized trials were included in the analysis and randomly assigned to 19 anticoagulants. With Enoxaparin as a control, Rivaroxaban (risk difference 0.07, 95 % credible interval 0.06 to 0.08), Edoxaban (RD 0.09, 95 % CrI 0.08 to 0.11), and Apixaban (RD 0.05, 95 % CrI 0.04 to 0.06) had the best effect in preventing VTE. However, in terms of comprehensive bleeding rate, Apixaban, Edoxaban, and Darexaban were the most effective and stable. Although effective in preventing VTE, bleeding remains relatively high in Rivaroxaban. Enoxaparin is low-molecular-weight heparin that is widely used in clinics, and although its overall efficacy is not the best, its efficacy and safety are very stable.

CONCLUSION

According to the available data, Apixaban, Edoxaban, and Darexaban are better than any anticoagulants in the prevention of VTE and bleeding during total knee or total hip arthroplasty. In our study, Fondaparinux, Eribaxaban, Dalteparin, Betrixaban, Bemiparin, Reviparin, Acenocoumarol, and Tinzaparin were scarce in the included studies, therefore, more evidence is needed to prove their efficacy and safety.

Thromboprophylaxis across orthopaedic surgery: Bibliometric analysis of the most cited articles

PURPOSE

One of the most common adverse events after orthopaedic surgery, with a potential for subsequent serious morbidity and mortality is venous thromboembolism (VTE). Bibliometric analysis has been performed regarding many topics and across orthopaedics. As DVT prophylaxis is a major component of both orthopaedic surgery considerations and research, a bibliometric analysis in this area would prove beneficial in not only in understanding the research done in the field thus far, but would also direct future research efforts.

METHODS

The Web of Science (WoS) database from the Institute of Scientific Information (ISI) was used to compile articles for bibliometric analysis using Boolean search: ((Orthopaedic∗ OR Orthopaedic∗) AND (thromboprophylaxis OR Thromboembolism OR Deep vein thrombosis OR thrombus OR embolism OR anticoagulation OR Embolus OR prophylaxis)).

RESULTS

The Top 100 cited articles included in the final list generated a total of 21,099 citations. The highest cited article was Prevention of venous thromboembolism by Geerts et al. published in Chest, which had a total of 2802 on WoS, and a calculated citation density of 215.54 of citations/years since publication. Comparing the overall citation against the year of publication there was a slight positive trend favoring more recent publications (R-value: 0.142; adjusted R-squared: 0.01; p = 0.16). Analysis of an articles Level of Evidence (LOE), 17 were grade with a level of I.

CONCLUSIONS

Orthopaedic thromboprophylaxis is an ever-changing field that is at the forefront of orthopaedic literature. The significant trend favoring high quality research within orthopaedic thromboprophylaxis demonstrates the importance of this topic and there was a need for a guide to best understand the evolution of DVT prophylaxis.

Evaluation of the therapeutic effect of acoustic therapy combined with acupuncture on idiopathic tinnitus: A randomized controlled trial protocol

BACKGROUND:

There is no effective treatment for idiopathic tinnitus. Both acoustic therapy and acupuncture have been used in the treatment of idiopathic tinnitus, but the clinical efficacy is quite different. For there is no clinical study combining the 2, the purpose of this randomized controlled trial is to evaluate the effectiveness and safety of acoustic therapy combined with acupuncture in the treatment of idiopathic tinnitus.

METHODS:

This is a prospective randomized controlled trial to study the effectiveness and safety of acoustic therapy combined with acupuncture in the treatment of idiopathic tinnitus, and is approved by the clinical research ethics committee of our hospital. The patients are randomly divided into one of 2 treatment options: (A) acoustic therapy combined with acupuncture group and (B) simple acupuncture group. Patients, doctors, nurses, and data collection assistants are blinded to group allocation. Observation indicators include: 1. Tinnitus Disability Scale; 2. Loudness visual analog scale; 3. Adverse reactions. Data is analyzed using the statistical software package SPSS version 25.0 (Chicago, IL).

DISCUSSION:

This protocol will evaluate the efficacy and safety of acoustic therapy combined with acupuncture in the treatment of idiopathic tinnitus. The results of this experiment will provide clinical evidence for the use of acoustic therapy combined with acupuncture in the treatment of idiopathic tinnitus.

TRIAL REGISTRATION:

This study protocol is registered in

ETHICS AND DISSEMINATION:

Private information from individuals will not be published. This systematic review also does not involve endangering participant rights. Ethical approval was not required.

OSF REGISTRATION NUMBER:

DOI 10.17605/OSF.IO/87VFB.

Comparison of the efficacy of rivaroxaban and dabigatran etexilate in preventing venous thrombosis after arthroplasty: A protocol of randomized controlled trial

Background:

New oral anticoagulants (NOAC) are gradually accepted by clinical practice for its convenient route of administration and stable effect. Both rivaroxaban and dabigatran etexilate have been used in the prevention and treatment of venous embolism after arthroplasty, but there is a lack of direct comparison between the 2 effects. Therefore, the purpose of this randomized controlled trial was to evaluate the efficacy and safety of 2 new oral anticoagulants, rivaroxaban, and dabigatran etexilate, in the prevention of venous thromboembolism after joint replacement.

Methods:

This is a prospective randomized controlled trial to study the efficacy and safety of rivaroxaban and dabigatran etexilate in the prevention of venous thromboembolism after joint replacement, and is approved by the clinical research ethics of our hospital. Patients were randomly divided into 1 of 2 treatment regimens:

Patients, doctors, nurses, and data collection assistants were blinded to group allocation. The indicators of observation include:

Data were analyzed using the statistical software package SPSS version 25.0 (Chicago, IL).

Discussion:

This study will evaluate the efficacy and safety of rivaroxaban and dabigatran etexilate in preventing venous thrombosis after joint replacement. The results of this experiment will provide clinical basis for the use of rivaroxaban or dabigatran etexilate to prevent venous thrombosis after joint replacement.

Ethics and dissemination:

Private information from individuals will not be published. This systematic review also does not involve endangering participant rights. Ethical approval was not required. The results may be published in a peer-reviewed journal or disseminated at relevant conferences.

OSF Registration number:

DOI 10.17605/OSF.IO/QVDCW.

Direct oral anticoagulants (DOACs) and neck of femur fractures: Standardising the perioperative management and time to surgery

Demographic projections for hip fragility fractures indicate a rising annual incidence by virtue of a multimorbid, ageing population with more noncommunicable diseases (NCDs). NCDs are characterised by slow progression and long duration ranging from ischaemic cardiovascular disease, cerebrovascular disease, diabetes, chronic obstructive pulmonary disease to various cancers. Management of this disease burden often involves commencing patients on oral anticoagulants to reduce the risk of thromboembolic events. The use of direct oral anticoagulants (DOACs) in clinical practice has increased due to their rapid onset of action, short half-life and predictable anticoagulant effects, without the need for routine monitoring. Safe and timely surgical intervention relies on reversal of anticoagulants. However, the lack of specific evidence-based guidelines for the perioperative management of patients on DOACs with hip fractures has proved challenging; in particular, the accessibility of DOAC-specific assays, justification of the cost-benefit ratio of targeted reversal agents and indications for neuraxial anaesthesia. This has led to potentially avoidable delays in surgical intervention. Following a literature review of the pharmacokinetic and pharmacodynamics of commonly used DOACs in our region including the role of surrogate markers, we propose a systematic, evidence-based guideline to the perioperative management of hip fractures DOACs. We believe this standardised protocol can be easily replicated between hospitals. We recommend that if patients are deemed suitable for a general anaesthesia, with satisfactory renal function, optimal surgical time should be 24 h following the last ingested dose of DOAC.

Multi-Criteria Model for Evaluating Drugs to Prevent Deep Venous Thrombosis Associated With Orthopedic Surgery: A Hospital-Based Case Study

BACKGROUND

It's estimated that 40% to 60% of patients undergoing major orthopedic surgery of the hip or knee who do not receive thromboprophylaxis will develop deep venous thrombosis Instituto Nacional de Traumatologia e Ortopedia has established a guideline to prevent DVT with the administration of the Enoxaparin. Recently, institute stakeholders have been questioning this guideline as new oral anticoagulants that offer more comfort and efficacy, but present higher risk of bleeding, have been appearing in the market for treating deep venous thrombosis.

OBJECTIVE

This study aims to validate the application of a multicriteria decision analysis in a real-world problem, the use of rivaroxaban and enoxaparin to prevent deep venous thrombosis.

METHODS

The multicriteria method MACBETH (Measuring Attractiveness by a Categorical Based Evaluation Technique) was used in a decision conferencing process to develop an evaluation model for measuring the relative value of the drugs on each evaluation criterion, separately and globally. The model-building process was informed by a literature review and meta-analysis of randomized clinical trials with a critical appraisal of the evidence.

RESULTS

We report a model-structure with eight criteria, each one associated with a weighting coefficient and value function. Following a simple additive aggregation process, the model-outputs showed that Rivaroxaban was considered a robust option for DVT. Sensitivity analysis and robustness analysis were performed and testify the consistency of the results.

CONCLUSION

This article contributes to literature by showing how MACBETH method can be combined with scientific evidence and participatory group processes, for health technology assessment in hospitals.

Risk of Major Gastrointestinal Bleeding With New vs Conventional Oral Anticoagulants: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

There is controversy over whether use of non-vitamin K antagonist oral anticoagulants (NOACs) associates with increased risk of major gastrointestinal bleeding (GIB) compared with conventional therapies (such as vitamin K antagonists or anti-platelet agents). We performed a systematic review and meta-analysis of data from randomized controlled trials and high-quality real-world studies.

METHODS

We performed a systematic search of the MEDLINE, EMBASE, Cochrane Library, and ClinicalTrials.gov Website databases (through Oct 12, 2018) for randomized controlled trials and high-quality real-world studies that reported major GIB events in patients given NOACs or conventional therapy. Relative risks (RRs) for randomized controlled trials and adjusted hazard ratios (aHRs) for real-world studies were calculated separately using random-effects models.

RESULTS

We analyzed data from 43 randomized controlled trials (183,752 patients) and 41 real-world studies (1,879,428 patients). The pooled major rates of GIB for patients on NOACs (1.19%) vs conventional treatment (0.92%) did not differ significantly (RR from randomized controlled trials, 1.09; 95% CI, 0.91-1.31 and aHR from real-world studies, 1.02; 95% CI, 0.94-1.10; P_interaction=.52). Rivaroxaban, but not other NOACs, was associated with an increased risk for major GIB (RR from randomized controlled trials, 1.39; 95% CI, 1.17-1.65 and aHR from real-world studies, 1.14; 95% CI, 1.04-1.23; P_interaction = .06). Analyses of subgroups, such as patients with different indications, dosage, or follow-up time, did not significantly affect results. Meta-regression analysis failed to detect any potential confounding to impact the primacy outcome.

CONCLUSIONS

In a systematic review and meta-analysis of data from randomized controlled trials and real-world studies, we confirmed that there is no significant difference in risk of major GIB between patients receiving NOACs vs conventional treatment. Rivaroxaban users had a 39% increase in risk for major GIB.

American Society of Hematology 2019 guidelines for management of venous thromboembolism: prevention of venous thromboembolism in surgical hospitalized patients

BACKGROUND

Venous thromboembolism (VTE) is a common source of perioperative morbidity and mortality.

OBJECTIVE

These evidence-based guidelines from the American Society of Hematology (ASH) intend to support decision making about preventing VTE in patients undergoing surgery.

METHODS

ASH formed a multidisciplinary guideline panel balanced to minimize bias from conflicts of interest. The McMaster University GRADE Centre supported the guideline-development process, including performing systematic reviews. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to assess evidence and make recommendations, which were subject to public comment.

RESULTS

The panel agreed on 30 recommendations, including for major surgery in general (n = 8), orthopedic surgery (n = 7), major general surgery (n = 3), major neurosurgical procedures (n = 2), urological surgery (n = 4), cardiac surgery and major vascular surgery (n = 2), major trauma (n = 2), and major gynecological surgery (n = 2).

CONCLUSIONS

For patients undergoing major surgery in general, the panel made conditional recommendations for mechanical prophylaxis over no prophylaxis, for pneumatic compression prophylaxis over graduated compression stockings, and against inferior vena cava filters. In patients undergoing total hip or total knee arthroplasty, conditional recommendations included using either aspirin or anticoagulants, as well as for a direct oral anticoagulant over low-molecular-weight heparin (LMWH). For major general surgery, the panel suggested pharmacological prophylaxis over no prophylaxis, using LMWH or unfractionated heparin. For major neurosurgery, transurethral resection of the prostate, or radical prostatectomy, the panel suggested against pharmacological prophylaxis. For major trauma surgery or major gynecological surgery, the panel suggested pharmacological prophylaxis over no prophylaxis.

Enhancing the Quality of Rivaroxaban Exposure Estimates Using Prothrombin Time in the Absence of Pharmacokinetic Sampling

Prothrombin time (PT) is a measure of coagulation status and was assessed in the majority of patients in the rivaroxaban phase II and III clinical trials as a pharmacodynamic marker. In the absence of sufficient phase III pharmacokinetic (PK) data to provide individual exposure measures for input into rivaroxaban exposure–response analyses, the aim of the present study was to investigate the use of PT‐adjustment approaches (i.e., the use of observed individual PT measurements) to enhance the prediction of individual rivaroxaban exposure metrics (derived using a previously developed integrated population PK model) based on the observed linear relationship between PT and rivaroxaban plasma concentrations. The PT‐adjustment approaches were established using time‐matched PK and PT measurements, which were available from 1,779 patients across four phase II trials and one phase III trial of rivaroxaban. PT‐adjusted exposure estimates improved the identification of statistically significant effects when compared with covariate‐only exposure estimates.

Does the form of venous thromboembolism prophylaxis following primary total knee arthroplasty alter the rate of early reoperation or revision surgery?

BACKGROUND

Currently there is significant variation in the management of venous thromboembolism prophylaxis following total knee arthroplasty (TKA). Excessive wound ooze and bleeding is thought to increase a patient's risk of haematoma formation and possible infection. We evaluated the rate of unexpected reoperation in the perioperative period in patients who received aspirin, rivaroxaban or enoxaparin following primary TKA.

METHOD

A systematic literature search was conducted in MEDLINE, CENTRAL and Embase to identify patients who underwent primary TKA. Two researchers independently reviewed the references identified in the literature search. The final 11 studies included for review were published between 1996 and 2016.

RESULTS

There was a higher rate of reoperation in patients treated with aspirin following TKA when compared to enoxaparin and rivaroxaban in the perioperative period. Of the 5141 patients treated with enoxaparin, 11 (0.21%) required reoperation; of the 2764 patients treated with rivaroxaban, 12 (0.43%) required reoperation; and of the 228 patients treated with aspirin, seven (3.07%) required reoperation. The average time to follow-up in the 11 studies was 55 days, ranging from 30 to 180 days post-operatively.

CONCLUSION

There was a higher rate of reoperation in patients treated with aspirin following TKA when compared to enoxaparin and rivaroxaban in the perioperative period. While there is extensive data on the safety and efficacy of these medications following joint arthroplasty, improved reporting of surgically relevant outcomes are needed to assist both the surgeon and patient in clinical decision-making.

Clinical trial on the effect of tranexamic acid on bleeding and fibrinolysis in primary hip and knee replacement

BACKGROUND

Tourniquet-induced ischaemia could increase fibrinolysis and enhance tranexamic acid (TXA) efficacy in total knee arthroplasty (TKA) compared to total hip arthroplasty (THA). The aims of this study are to compare the effect of TXA on bleeding and fibrinolysis in both types of surgery, and to record thromboembolic complications.

METHODS

A prospective double-blind study was conducted on patients scheduled for TKA or THA who received TXA (2 bolus of 10mg/kg) or placebo. Bleeding and fibrinolysis were evaluated. Doppler-ultrasound and computed tomography were performed in order to assess any thromboembolic complications.

RESULTS

A total of 44 patients were included (11 THA and 11 TKA treated with TXA; 11 THA and 11 TKA as controls). Blood losses were significantly lower in the TXA group (mean 921mL vs 1,383mL in THA and 969mL vs 1,223mL in TKA), and no transfusions were needed with TXA, whereas 5 blood units were transfused in controls. TXA was equally effecting in reducing bleeding in both surgeries (33% in THA and 21% in TKA). The significant mean increase in D-dimers from baseline to 6 hours after surgery (1,004 ug/L to 10,284 ug/L in THA and 571 ug/L to 6,480 ug/L in TKA) was attenuated by TXA (1,077 ug/L to 2,590 ug/L in THA and 655 ug/L to 2,535 ug/L in TKA). There were no differences in thromboembolic episodes.

CONCLUSIONS

Prophylactic use of tranexamic acid is equally effective in reducing bleeding in TKA and THA. Both surgeries have a similar effect on fibrinolysis.

Effectiveness and safety of rivaroxaban for the prevention of thrombosis following total hip or knee replacement: A systematic review and meta-analysis

BACKGROUND

Prophylactic anticoagulant therapy is recommended to reduce the risk of venous thromboembolism (VTE) after total hip or knee arthroplasty, and has become the standard of care. Rivaroxaban is a novel oral medication that directly inhibits factor Xa for the prevention and treatment of thromboembolic conditions.

METHOD

A meta-analysis of randomized controlled trials (RCTs) was performed to determine the efficacy and safety of rivaroxaban after total hip arthroplasty (THA) and total knee arthroplasty (TKA) surgery. We reviewed several databases including PubMed, the Cochrane Library, Embase and the US trial registry to detect appropriate RCTs for our meta-analysis. The primary efficacy outcome of this meta-analysis was the combination of any deep-vein thrombosis (DVT), non-fatal pulmonary embolism (PE), and death from any cause. The main safety outcome was bleeding events which included significant bleeding events, clinically relevant insignificant bleeding events, or minor events. Other end points were the number of patients who received blood transfusion the volume of transfused whole blood or red blood cells, and the volume of postoperative drainage.

RESULT

Thirteen RCTs were included in this meta-analysis. This meta-analysis showed that the overall rate of VTE events, DVT, PE, and death were 1%, 6%, < 1% and < 1%, respectively, for patients receiving treatment with rivaroxaban after THA and TKA surgery. The subgroup analysis demonstrated rivaroxaban had more superior effects in THA patients. The pooled analysis of bleeding events showed that the overall rate of major bleeding events, overt bleeding events associated with fall in Hb of > 2 g/DL, clinically overt bleeding events leading to transfusion of > 2 units of blood, clinically overt bleeding events leading to further surgeries, and non-major bleeding events were < 1%, < 1%, < 1%, < 1%, and 3%, respectively.

CONCLUSION

This is the first systematic review of the literature providing incidence of efficacy and safety outcomes for thromboprophylaxis in THA and TKA patients. Moreover, this meta-analysis showed that rivaroxaban had more superior effect in THA patients.

Rivaroxaban for prevention and treatment of venous thromboembolism

Until recently, heparins and vitamin K antagonists (VKAs) were the cornerstones for prevention and treatment of venous thromboembolism (VTE). This situation changed with the introduction of the direct oral anticoagulants, which are now replacing low-molecular-weight heparin for thromboprophylaxis after elective hip or knee arthroplasty and VKAs for VTE treatment. Rivaroxaban, an oral factor Xa inhibitor, was the first direct oral anticoagulant licensed for VTE prevention and treatment. This paper provides the rationale for factor Xa as a target for anticoagulants, describes the development of rivaroxaban, reviews its pharmacological profile, discusses the clinical trials with rivaroxaban for VTE prevention and treatment and highlights areas of uncertainty.

Influence of age on the pharmacokinetics, pharmacodynamics, efficacy, and safety of rivaroxaban

OBJECTIVE

Atrial fibrillation, peripheral and coronary artery disease, and venous thromboembolism are major risk factors for stroke, disability, and death in the rapidly growing older (≥ 65 years.) population. In the absence of clear guidelines on the appropriate use of the newer non-vitamin K antagonist oral anticoagulants in this population, this study specifically reviews the available literature for rivaroxaban and the impact of age that may affect the pharmacokinetics, pharmacodynamics, efficacy, and safety of this anticoagulant.

METHODS

This review includes a summary of data obtained from the available literature concerning both older healthy subjects and older patients with various aspects of cardiovascular disease enrolled in rivaroxaban clinical trials and data from real world evidence studies.

RESULTS

Evaluation of the clinical pharmacology in healthy, older adults reveal no clinically relevant effect of age on rivaroxaban pharmacokinetics and pharmacodynamics. Population pharmacokinetic studies in older patients with thromboembolic diseases suggest a moderate effect of increasing age on rivaroxaban clearance, albeit not clinically significant. Additionally, sub-group analyses from large, phase 3 clinical trials demonstrate consistent efficacy and safety in the older patient population vs the overall population. These findings are further supported by real-world evidence studies.

CONCLUSION

A favorable clinical profile with rivaroxaban was observed across age sub-groups, supporting the premise that dosing in older adults does not necessitate adjustment. However, it is prudent that a cautious and individualized approach is taken for treatment with any anticoagulant in older adults.

Rivaroxaban versus enoxaparin for the prevention of venous thromboembolism after total knee arthroplasty: A meta-analysis

OBJECTIVE

This article analyzed the clinical efficacy and tolerability of rivaroxaban and enoxaparin in patients undergoing total knee arthroplasty (TKA) surgery.

METHODS

Five randomized, controlled clinical trials on rivaroxaban versus enoxaparin in patients who underwent TKA were identified and included in this meta-analysis.

RESULTS

The meta-analysis indicated that rivaroxaban prophylaxis was associated with lower rates of symptomatic venous thromboembolism (VTE) (relative risk[RR]:0.55; 95% confidence interval [CI]: 0.35-0.86; P = .009), symptomatic deep vein thrombosis (DVT) (RR 0.44, 95% CI 0.25-0.80, P = .007), asymptomatic DVT (RR: 0.57; 95% CI: 0.37-0.89; P = .01), distal DVT (RR: 0.62; 95% CI: 0.45-0.85; P = .003) and proximal DVT (RR: 0.42; 95% CI: 0.24-0.75; P = .004). Compared with the enoxaparin group, the incidence of symptomatic pulmonary embolism (PE) (RR: 0.48; 95% CI: 0.19-1.24; P = .13) in the rivaroxaban group was not significantly different. A nonsignificant trend towards all-cause death (RR: 0.38; 95% CI: 0.03-4.92; P = .46) or major bleeding (RR: 1.59; 95% CI: 0.77-3.27; P = .21) risk between rivaroxaban and enoxaparin prophylaxis was found.

CONCLUSION

Compared with the enoxaparin group, the group using rivaroxaban after TKA had a significantly lower rate of symptomatic VTE, symptomatic DVT, asymptomatic DVT, distal DVT, and proximal DVT. Our study shows that rivaroxaban after TKA is more effective than enoxaparin and did not increase major bleeding or all-cause mortality.

Combined use of topical intraarticular tranexamic acid and rivaroxaban in total knee arthroplasty safely reduces blood loss, transfusion rates, and wound complications without increasing the risk of thrombosis

BACKGROUND

Blood loss and deep vein thrombosis (DVT) are important complications after total knee arthroplasty (TKA). Topical tranexamic acid (TXA) effectively reduces wound bleeding but may elevate the risk of DVT. In contrast, rivaroxaban potently prevents DVT but has been associated with bleeding complications. The simultaneous use of topical TXA and rivaroxaban in TKA has not been much investigated.

METHODS

A retrospective cohort study was conducted with two consecutive groups of patients who underwent TKA. Intraoperatively, one group (RVTX group) received topical, intraarticular TXA, while the other (RV group) did not. Both groups were administered rivaroxaban postoperatively for 14 days and underwent Doppler ultrasound for DVT screening. After propensity score matching, both groups consisted of 52 patients (104 patients in total) and were compared regarding total drain output, nadir haemoglobin (Hb), maximum Hb decrease, calculated total blood loss, transfusion rate, and incidence of DVT and wound complications.

RESULTS

Both groups showed no significant differences in the propensity-matched variables of age, sex, body mass index, American Society of Anesthesiologists physical status score, and preoperative Hb. The RVTX group showed a significantly higher nadir Hb (p < 0.001), lower drain output (p < 0.001), Hb decrease (p = 0.015), total blood loss (p < 0.001), and rate of transfusion (p < 0.001) and fewer wound complications (p = 0.027). However, the incidence of DVT (p = 1.000) did not differ significantly between the two groups, and all cases were asymptomatic.

CONCLUSIONS

The combined use of intraarticular topical TXA with rivaroxaban in patients undergoing TKA is a safe and effective method to reduce blood loss, the need for transfusion, and wound complications without elevating the risk of DVT.

Integrated Population Pharmacokinetic Analysis of Rivaroxaban Across Multiple Patient Populations

The population pharmacokinetics (PK) of rivaroxaban have been evaluated in several population‐specific models. We developed an integrated population PK model using pooled data from 4,918 patients in 7 clinical trials across all approved indications. Effects of gender, age, and weight on apparent clearance (CL/F) and apparent volume of distribution (V/F), renal function, and comedication on CL/F, and relative bioavailability as a function of dose (F) were analyzed. Virtual subpopulations for exposure simulations were defined by age, creatinine clearance (CrCL) and body mass index (BMI). Rivaroxaban PK were adequately described by a one‐compartment disposition model with a first‐order absorption rate constant. Significant effects of CrCL, use of comedications, and study population on CL/F, age, weight, and gender on V/F, and dose on F were identified. CrCL had a modest influence on exposure, whereas age and BMI had a minor influence. The model was suitable to predict rivaroxaban exposure in patient subgroups of special interest.

Oral anticoagulants for primary prevention, treatment and secondary prevention of venous thromboembolic disease, and for prevention of stroke in atrial fibrillation: systematic review, network meta-analysis and cost-effectiveness analysis

BACKGROUND

Warfarin is effective for stroke prevention in atrial fibrillation (AF), but anticoagulation is underused in clinical care. The risk of venous thromboembolic disease during hospitalisation can be reduced by low-molecular-weight heparin (LMWH): warfarin is the most frequently prescribed anticoagulant for treatment and secondary prevention of venous thromboembolism (VTE). Warfarin-related bleeding is a major reason for hospitalisation for adverse drug effects. Warfarin is cheap but therapeutic monitoring increases treatment costs. Novel oral anticoagulants (NOACs) have more rapid onset and offset of action than warfarin, and more predictable dosing requirements.

OBJECTIVE

To determine the best oral anticoagulant/s for prevention of stroke in AF and for primary prevention, treatment and secondary prevention of VTE.

DESIGN

Four systematic reviews, network meta-analyses (NMAs) and cost-effectiveness analyses (CEAs) of randomised controlled trials.

SETTING

Hospital (VTE primary prevention and acute treatment) and primary care/anticoagulation clinics (AF and VTE secondary prevention).

PARTICIPANTS

Patients eligible for anticoagulation with warfarin (stroke prevention in AF, acute treatment or secondary prevention of VTE) or LMWH (primary prevention of VTE).

INTERVENTIONS

NOACs, warfarin and LMWH, together with other interventions (antiplatelet therapy, placebo) evaluated in the evidence network.

MAIN OUTCOME MEASURES

Efficacy Stroke, symptomatic VTE, symptomatic deep-vein thrombosis and symptomatic pulmonary embolism. Safety Major bleeding, clinically relevant bleeding and intracranial haemorrhage. We also considered myocardial infarction and all-cause mortality and evaluated cost-effectiveness.

DATA SOURCES

MEDLINE and PREMEDLINE In-Process & Other Non-Indexed Citations, EMBASE and The Cochrane Library, reference lists of published NMAs and trial registries. We searched MEDLINE and PREMEDLINE In-Process & Other Non-Indexed Citations, EMBASE and The Cochrane Library. The stroke prevention in AF review search was run on the 12 March 2014 and updated on 15 September 2014, and covered the period 2010 to September 2014. The search for the three reviews in VTE was run on the 19 March 2014, updated on 15 September 2014, and covered the period 2008 to September 2014.

REVIEW METHODS

Two reviewers screened search results, extracted and checked data, and assessed risk of bias. For each outcome we conducted standard meta-analysis and NMA. We evaluated cost-effectiveness using discrete-time Markov models.

RESULTS

Apixaban (Eliquis^®, Bristol-Myers Squibb, USA; Pfizer, USA) [5 mg bd (twice daily)] was ranked as among the best interventions for stroke prevention in AF, and had the highest expected net benefit. Edoxaban (Lixiana^®, Daiichi Sankyo, Japan) [60 mg od (once daily)] was ranked second for major bleeding and all-cause mortality. Neither the clinical effectiveness analysis nor the CEA provided strong evidence that NOACs should replace postoperative LMWH in primary prevention of VTE. For acute treatment and secondary prevention of VTE, we found little evidence that NOACs offer an efficacy advantage over warfarin, but the risk of bleeding complications was lower for some NOACs than for warfarin. For a willingness-to-pay threshold of > £5000, apixaban (5 mg bd) had the highest expected net benefit for acute treatment of VTE. Aspirin or no pharmacotherapy were likely to be the most cost-effective interventions for secondary prevention of VTE: our results suggest that it is not cost-effective to prescribe NOACs or warfarin for this indication.

CONCLUSIONS

NOACs have advantages over warfarin in patients with AF, but we found no strong evidence that they should replace warfarin or LMWH in primary prevention, treatment or secondary prevention of VTE.

LIMITATIONS

These relate mainly to shortfalls in the primary data: in particular, there were no head-to-head comparisons between different NOAC drugs.

FUTURE WORK

Calculating the expected value of sample information to clarify whether or not it would be justifiable to fund one or more head-to-head trials.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42013005324, CRD42013005331 and CRD42013005330.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Persistent Pulmonary Embolism Rates Following Total Knee Arthroplasty Even With Prophylactic Anticoagulants

BACKGROUND

Symptomatic pulmonary embolism (PE), a significant and life-threatening complication following total knee arthroplasty (TKA), has been described as a "never event." Despite a number of advancements in care, PE continues to occur following TKA. This study evaluates symptomatic PE rates over time in TKA patients enrolled in multicenter randomized clinical trials assessing the efficacy of venous thromboembolism prophylaxis regimens.

METHODS

The MEDLINE and Cochrane Central Register of Controlled Trials were searched to identify clinical trials assessing prophylactic anticoagulation in patients undergoing TKA between January 1995 and December 2016. A random effect model was used to combine PE rates across studies. The pooled proportion of symptomatic PEs was calculated and heterogeneity was quantified with the I² statistic. A 95% prediction interval was constructed to examine what the expected range in the proportion of symptomatic PEs would be in future studies. Meta-regression was used to explore the effect of time on the rate of symptomatic PEs.

RESULTS

A total of 18 studies representing 27,073 patients were included in the meta-analysis. The symptomatic PE rate was 0.37% (95% confidence interval, 0.24%-0.52%). There was significant heterogeneity across studies, I² = 66%. Between 1996 and 2010, the proportion of PEs did not change in the regression analysis. The 95% prediction interval was 0.0002 to 0.0106, indicating that in similar future studies, the true proportion of symptomatic PEs would range from 0.02% to 1.06%.

CONCLUSION

Over a 14-year period, the symptomatic PE rate after TKA was relatively constant even when patients received potent anticoagulation. These results suggest that some patients may have a genetic predisposition to develop a PE and more effective risk stratification protocols need to be developed to make sure patients receive appropriate anticoagulation.

Interpretation of endpoints in a network meta-analysis of new oral anticoagulants following total hip or total knee replacement surgery

New oral anticoagulant (NOAC) regimens [dabigatran 150 mg (D150) and 220 mg (D220), rivaroxaban 10 mg (R20), and apixaban 2.5 mg bid (A5)] were effective and safe compared to enoxaparin for the prevention of venous thromboembolism (VTE) following elective total knee (TKR) or hip replacement (THR) surgery. First a cluster analysis was used to identify homogeneous studies for the trial programs of each NOAC. Second, only studies reporting VTE and VTE-related death, major bleeding, and mortality were included. The odds ratio (OR) and 95% confidence interval (CI) were calculated for each NOAC regimen versus the comparator. Third, these data were used for the indirect comparison between NOACs. Cluster analysis identified duration of treatment (10 ± 5 and 34 ± 5 days) as the only homogeneous parameter across all NOAC programs (p>0.05) except for A5 and VTE over 10 ± 5 days (analysis not performed). The results of the calculated OR and 95% CI of the four NOAC regimens over 10 ± 5 and 34 ± 5 days showed inferiority of D150 and D220 compared to R10 for VTE (p<0.01, p<0.001). Comparisons of major bleeding and mortality were not different for all indirect comparisons. Despite the lack of standard definitions for VTE and bleeding outcomes, cluster analysis seems to be an appropriate tool to identify homogeneity across trial programs and to perform an indirect comparison for NOACs for prevention of VTE following TKR and THR surgery.

New oral anticoagulants in venous thromboembolism prophylaxis in orthopaedic patients: Are they really better?

Prophylaxis against venous thromboembolism (VTE) is considered standard of care. Appropriate chemoprophylaxis for VTE has been mandated by the United States government agencies and consumer groups. However, controversies exist regarding the most clinically relevant and safe chemoprophylaxis protocols in patients undergoing joint replacement surgery. Thus, this paper reviews the clinical efficacy and safety of newer oral anticoagulants. A literature search was performed for oral anticoagulants in advanced stages of development using PubMed and abstracts from thrombosis meetings. Most clinical trial data have demonstrated equal or superior efficacy in venographic endpoints in comparison to low-molecular-weight heparins (LMWH). However, bleeding complications have been reported to occur with oral anticoagulants as frequently as or more frequently than with LMWH. Other potential complications reported include liver enzyme elevation and cardiac irregularities. It remains to be established whether newer oral anticoagulants will be better alternatives to the current standard-ofcare in real-life medical clinical practice.

Low-Molecular-Weight Heparin and the Relative Risk of Surgical Site Bleeding Complications: Results of a Systematic Review and Meta-Analysis of Randomized Controlled Trials of Venous Thromboprophylaxis in Patients After Total Joint Arthroplasty

BACKGROUND

Venous thromboembolism causes significant morbidity and mortality in patients after total joint arthroplasty. Although network meta-analyses have demonstrated a benefit of various thromboprophylactic agents, there remains a concern in the surgical community regarding the resulting wound complications. There is currently no systematic review of the surgical site bleeding complications of thromboprophylactic agents. The aim of this study was to systematically review the surgical site bleeding outcomes of venous thromboembolism prophylaxis in this population.

METHODS

A systematic review and meta-analysis was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Randomized controlled trials comparing more than one of low-molecular-weight heparin (LMWH), warfarin, rivaroxaban, apixaban, dabigatran, aspirin, or no pharmacologic treatment in patients after total hip or knee arthroplasty were selected for inclusion. Five meta-analyses were performed to compare LMWH with control, warfarin, apixaban, rivaroxaban, and dabigatran.

RESULTS

Forty-five randomized controlled trials of 56,730 patients were included. LMWH had a significantly increased relative risk of surgical site bleeding in comparison with control (relative risk, 2.32; 95% confidence interval, 1.40-3.85) and warfarin (1.54; 1.23-1.94). The relative risk of LMWH trended higher than apixaban (1.27; 1.00-1.63) and was similar to rivaroxaban (0.95; 0.74-1.23). Only 1 study reported the risk of surgical site bleeding in LMWH vs dabigatran (5.97; 2.08-17.11).

CONCLUSION

LMWH increased the risk of surgical site bleeding compared with control, warfarin. and dabigatran and trended toward an increased risk compared with apixaban. The risk of surgical site bleeding was similar with LMWH and rivaroxaban.

Direct Oral Anticoagulants Vs. Enoxaparin for Prevention of Venous Thromboembolism Following Orthopedic Surgery: A Dose-Response Meta-analysis

We carried out a dose–response model‐based meta‐analysis to assess venous thromboembolism (VTE) and bleeding with factor Xa (FXa) inhibitors (apixaban, edoxaban, rivaroxaban) and a thrombin inhibitor (dabigatran) compared with European (EU) (40 mg q.d.) and North American (NA) (30 mg Q12H) dose regimens of a low molecular weight heparin (enoxaparin) following orthopedic surgery. Statistically significant differences in both VTE and bleeding outcomes were found between the NA and EU doses of enoxaparin, with odds ratios (95% confidence interval) for the NA vs. EU dose of 0.73 (0.71–0.76) and 1.20 (1.14–1.29) for total VTE and major bleeding, respectively. At approved doses, estimated odds ratios vs. both doses of enoxaparin for the three FXa inhibitors (range: 0.35–0.75 for VTE; 0.76–1.09 for bleeding) compared with those for dabigatran (range: 0.66–1.21 for VTE; 1.10–1.38 for bleeding) suggested generally greater efficacy and less bleeding for the FXa inhibitors.

Differential inhibitory action of apixaban on platelet and fibrin components of forming thrombi: Studies with circulating blood and in a platelet-based model of thrombin generation

Introduction

Mechanisms of action of direct oral anticoagulants (DOAC) suggest a potential therapeutic use in the prevention of thrombotic complications in arterial territories. However, effects of DOACs on platelet activation and aggregation have not been explored in detail. We have investigated the effects of apixaban on platelet and fibrin components of thrombus formation under static and flow conditions.

Methods

We assessed the effects of apixaban (10, 40 and 160 ng/mL) on: 1) platelet deposition and fibrin formation onto a thrombogenic surface, with blood circulating at arterial shear-rates; 2) viscoelastic properties of forming clots, and 3) thrombin generation in a cell-model of coagulation primed by platelets.

Results

In studies with flowing blood, only the highest concentration of apixaban, equivalent to the therapeutic C_max, was capable to significantly reduce thrombus formation, fibrin association and platelet-aggregate formation. Apixaban significantly prolonged thromboelastometry parameters, but did not affect clot firmness. Interestingly, results in a platelet-based model of thrombin generation under more static conditions, revealed a dose dependent persistent inhibitory action by apixaban, with concentrations 4 to 16 times below the therapeutic C_max significantly prolonging kinetic parameters and reducing the total amount of thrombin generated.

Conclusions

Our studies demonstrate the critical impact of rheological conditions on the antithrombotic effects of apixaban. Studies under flow conditions combined with modified thrombin generation assays could help discriminating concentrations of apixaban that prevent excessive platelet accumulation, from those that deeply impair fibrin formation and may unnecessarily compromise hemostasis.

Pulmonary embolism: new treatments for an old problem

Nonvitamin K antagonist oral anticoagulants, previously referred to as novel oral anticoagulants, have emerged in recent years as attractive treatment options for acute pulmonary embolism (PE). However, despite the widespread anticipation by physicians and the approval of rivaroxaban, apixaban, dabigatran, and more recently edoxaban, there is still some reluctance to choose these newer agents over conventional treatment with heparin/vitamin K antagonists. Acute PE puts a considerable strain on emergency departments, and medical staff rely on efficient diagnosis and risk assessment to manage the condition appropriately and economically. Rivaroxaban and apixaban offer a convenient and cost-effective single-drug therapeutic approach. The ease of administration and drug management may enable earlier discharge and outpatient treatment in low-risk patients and alleviate the demands put on emergency-care infrastructures. This review discusses the current guidelines and anticoagulation options in the emergency setting for patients with acute PE and explores the reasons for the slow transition from old to new treatment options.