Dabigatran versus enoxaparin for prevention of venous thromboembolism after hip or knee arthroplasty: a pooled analysis of three trials. Thromb Res. 2010;126:175-182. [PMID: 20434759 DOI: 10.1016/j.thromres.2010.03.021]

Outcomes of different perioperative management strategies of patients on chronic anticoagulation in elective total hip and knee arthroplasty: a systematic review

INTRODUCTION

There are currently different management guidelines for patients undergoing elective total hip arthroplasty (THA) or total knee arthroplasty (TKA) that are on long-term anticoagulation. The timing of discontinuation and restarting the anticoagulation is challenging during the postoperative care, which often involves general practitioners and physiotherapists.

METHODS

The systematic review followed the PRISMA guidelines and included 3 databases: PubMed/MEDLINE, EMBASE, and Web of Science Core Collection. It was registered in the International Prospective Register for Systematic Reviews and Meta-analysis (PROSPERO) under the registration number: CRD42023408906. The risk of bias assessment was performed using the Methodological index for non-randomized studies (MINORS) criteria.

RESULTS

Six retrospective studies involving 727 patients with therapeutic anticoagulation (1,540 controls) for elective THA, TKA and revision arthroplasty have been included. The follow-up ranged from 30 days to 1 year postoperatively. All studies evaluated outcomes of warfarin therapeutic anticoagulation versus prophylactic dosages of one or more of the following: warfarin, aspirin, low-molecular-weight heparin (LMWH) and unfractionated low-dose heparin (UFH). One study did not discontinue therapeutic anticoagulation. Two studies reported no significant differences in complications between groups, whilst 3 studies had significantly higher rates of superficial wound infections, revision surgeries, postoperative haematomas, and prosthetic joint infections (PJI).

CONCLUSION

Different anticoagulation-related perioperative management strategies achieve different outcomes following elective arthroplasty in patients with therapeutic chronic anticoagulation. There is contradictory evidence regarding the need for the discontinuation of therapeutic warfarin. Retrospective data showed that individual risk stratification with multi-modal prophylaxis resulted in minimal complications.

LEVEL OF EVIDENCE

Systematic Review of Level III studies.

Current Evidence and Expert Opinion on Thromboprophylaxis After Total Knee and Hip Replacement

An effective anticoagulant provides a balance between the risk for venous thromboembolism (VTE) and bleeding and is crucial in achieving optimal clinical outcomes in patients undergoing total hip replacement (THR) and total knee replacement (TKR) surgeries. We performed a review of the literature on thromboprophylaxis for patients undergoing total hip or knee replacement. This review article summarizes current guidelines and evidence for anticoagulation along with the expert opinion about pharmacological VTE prophylaxis, particularly non-Vitamin K antagonist oral anticoagulants (NOACs), for patients after total hip or knee replacement. Aspirin for VTE prophylaxis after TKR/THR has been controversial and most of the evidence is reported from observational research. Although the guidelines do not recommend any specific thromboprophylaxis agent, available evidence suggests that NOACs are as effective as low molecular weight heparins (LMWHs) in preventing VTE. Oral administration and the lack of dose monitoring make NOACs easy to use in outpatient settings in cases with challenging treatment compliances. They can be used for two weeks after TKR and five weeks after THR - six weeks after TKR and THR to cover the at-risk period for VTE post-discharge. Owing to the lack of evidence for a head-to-head comparison of NOACs, an anticoagulant with better efficacy and safety may be suggested in special patient populations (elderly, obese patients, or those with renal dysfunction). The expert opinion on pharmacological VTE prophylaxis provided in this article could address some gaps in the management of anticoagulation in patients with total hip or knee replacement.

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.

Efficacy and Safety of Enoxaparin versus New Oral Anticoagulants to Prevent Venous Thromboembolism after Total Hip Replacement: A Systematic Review and Meta-Analysis

Prophylactic anticoagulant therapy is recommended for reducing the risk of venous thromboembolism (VTE) after a total hip replacement (THR). However, it is not clear which anticoagulant is preferable. Hence, a systematic review and meta-analysis of randomized double-blind controlled trials (RDBCTs) were conducted to investigate the clinical efficacy and safety of enoxaparin in comparison with newer oral anticoagulants for the prevention of VTE after THR. The Cochrane Library, Scopus, Web of Science, Embase, and PubMed/Medline databases were used for PICO search strategy. Relative risks (RR) of symptomatic VTE, clinically relevant bleeding, mortality, and a net clinical endpoint were estimated employing a random effect meta-analysis. ITC and RevMan software were used for indirect and direct comparisons, respectively. Nine RDBCTs comprising 24,584 patients were included. As compared to enoxaparin, a reduced risk for symptomatic VTE was observed with rivaroxaban (confidence interval [CI]: 0.32–0.77; RR: 0.46%) and comparable with apixaban (0.12–1.26; 0.42%) and dabigatran (0.22–2.20; 0.70%). Contrarily to enoxaparin, a greater risk for clinically relevant bleeding was observed with rivaroxaban (1.03–1.48; 1.23%), comparable with dabigatran (0.96–1.33; 1.10%) and reduced with apixaban (0.19–5.66; 0.96%). In indirect or direct comparisons, the interventions did not differ on the net clinical endpoint. In conclusion, the findings of this meta-analysis revealed no significant difference in the efficacy and safety of new oral anticoagulants as compared to enoxaparin for the prevention of VTE after total hip replacement surgery.

Safety and Efficacy of Low Molecular Weight Heparin for Thromboprophylaxis in the Elderly: A Network Meta-Analysis of Randomized Clinical Trials

Background: Given their changing pathophysiology, elderly patients carry a high risk of embolism and bleeding events; hence, use of appropriate anticoagulants is very important. Low molecular weight heparin (LMWH) is one of the most widely used anticoagulants although LMWHs differ in their anti-Xa, antithrombin, and anticoagulant activities. To date, no study has directly compared the safety and efficacy of different LMWHs in the elderly. We aimed to compare such differences by conducting a network meta-analysis.

Methods: We searched the Pubmed, Embase, and Cochrane databases for randomized controlled trials (RCTs) of LMWHs that included patients ≥60 years old up to July 22, 2020. Safety outcomes included venous thromboembolism (VTE) or VTE-related death, deep thrombus embolism, and pulmonary embolism. Safety outcomes were clinically relevant bleeding, major bleeding, minor bleeding, and all-cause death. We calculated relative ratios (RR) and 95% confidence intervals (CI) for all outcomes. The cumulative ranking probabilities (SUCRA) were conducted to rank the comparative effects and safety of all LMWHs.

Results: We included 27 RCTs (30,441 elderly), comprising five LMWHs. LMWH was more effective than placebo in preventing VTE or VTE-related death (RR 0.36, 95% CI 0.25–0.53) but less effective than a novel oral anticoagulant (RR 1.59, 95% CI 1.33–1.91) and safer than acenocoumarol regarding risk of clinically relevant bleeding (RR 0.67, 95% CI 0.49–0.90). However, indirect comparison of efficacy and safety of the five LMWHs showed no significant difference in our network analysis, and the subgroup analyses (such as in patients with deep venous thrombosis, cardiac disease, or age >65 years old) supported the results. The SUCRA showed that tinzaparin performed best in preventing VTE or VTE-related death (SUCRA 68.8%, cumulative probability 42.3%) and all-cause death (SUCRA 84.2%, cumulative probability 40.7%), whereas nadroparin was predominant in decreasing the risk of clinically relevant bleeding (SUCRA 84.8%, cumulative probability 77.0%).

Conclusions: On present evidence, there are no significant differences in the efficacy and safety of different LMWHs for the elderly. According to the rank probability analysis, nadroparin seems to be safer for the elderly with a high risk of bleeding, whereas tinzaparin is more effective for those with low bleeding risk.

Thromboembolic and bleeding complications following primary total knee arthroplasty : a Danish nationwide cohort study

AIMS

The aim of this study is to compare the effectiveness and safety of thromboprophylactic treatments in patients undergoing primary total knee arthroplasty (TKA).

METHODS

Using nationwide medical registries, we identified patients with a primary TKA performed in Denmark between 1 January 2013 and 31 December 2018 who received thromboprophylactic treatment. We examined the 90-day risk of venous thromboembolism (VTE), major bleeding, and all-cause mortality following surgery. We used a Cox regression model to compute hazard ratios (HRs) with 95% confidence intervals (CIs) for each outcome, pairwise comparing treatment with dalteparin or dabigatran with rivaroxaban as the reference. The HRs were both computed using a multivariable and a propensity score matched analysis.

RESULTS

We identified 27,736 primary TKA patients who received thromboprophylactic treatment (rivaroxaban (n = 18,846); dalteparin (n = 5,767); dabigatran (n = 1,443); tinzaparin (n = 1,372); and enoxaparin (n = 308)). In the adjusted multivariable analysis and compared with rivaroxaban, treatment with dalteparin (HR 0.68 (95% CI 0.49 to 0.92)) or dabigatran (HR 0.31 (95% CI 0.13 to 0.70)) was associated with a decreased risk of VTE. No statistically significant differences were observed for major bleeding or all-cause mortality. The propensity score matched analysis yielded similar results.

CONCLUSION

Treatment with dalteparin or dabigatran was associated with a decreased 90-day risk of VTE following primary TKA surgery compared with treatment with rivaroxaban. Cite this article: Bone Joint J 2021;103-B(10):1571-1577.

Point-of-care detection and differentiation of anticoagulant therapy - development of thromboelastometry-guided decision-making support algorithms

Background

DOAC detection is challenging in emergency situations. Here, we demonstrated recently, that modified thromboelastometric tests can reliably detect and differentiate dabigatran and rivaroxaban. However, whether all DOACs can be detected and differentiated to other coagulopathies is unclear. Therefore, we now tested the hypothesis that a decision tree-based thromboelastometry algorithm enables detection and differentiation of all direct Xa-inhibitors (DXaIs), the direct thrombin inhibitor (DTI) dabigatran, as well as vitamin K antagonists (VKA) and dilutional coagulopathy (DIL) with high accuracy.

Methods

Following ethics committee approval (No 17–525-4), and registration by the German clinical trials database we conducted a prospective observational trial including 50 anticoagulated patients (n = 10 of either DOAC/VKA) and 20 healthy volunteers. Blood was drawn independent of last intake of coagulation inhibitor. Healthy volunteers served as controls and their blood was diluted to simulate a 50% dilution in vitro. Standard (extrinsic coagulation assay, fibrinogen assay, etc.) and modified thromboelastometric tests (ecarin assay and extrinsic coagulation assay with low tissue factor) were performed. Statistical analyzes included a decision tree analyzes, with depiction of accuracy, sensitivity and specificity, as well as receiver-operating-characteristics (ROC) curve analysis including optimal cut-off values (Youden-Index).

Results

First, standard thromboelastometric tests allow a good differentiation between DOACs and VKA, DIL and controls, however they fail to differentiate DXaIs, DTIs and VKAs reliably resulting in an overall accuracy of 78%. Second, adding modified thromboelastometric tests, 9/10 DTI and 28/30 DXaI patients were detected, resulting in an overall accuracy of 94%. Complex decision trees even increased overall accuracy to 98%. ROC curve analyses confirm the decision-tree-based results showing high sensitivity and specificity for detection and differentiation of DTI, DXaIs, VKA, DIL, and controls.

Conclusions

Decision tree-based machine-learning algorithms using standard and modified thromboelastometric tests allow reliable detection of DTI and DXaIs, and differentiation to VKA, DIL and controls.

Trial registration

Clinical trial number: German clinical trials database ID: DRKS00015704.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12959-021-00313-7.

Bleeding complications of thromboprophylaxis with dabigatran, nadroparin or rivaroxaban for 6 weeks after total knee arthroplasty surgery: a randomised pilot study

OBJECTIVES

For the non-vitamin-K oral anticoagulants, data on bleeding when used for 42 days as thromboprophylaxis after total knee arthroplasty (TKA) are scarce. This pilot study assessed feasibility of a multicentre randomised clinical trial to evaluate major and clinically relevant non-major bleeding during 42-day use of dabigatran, nadroparin and rivaroxaban after TKA.

PATIENTS AND METHODS

In 70 weeks, between July 2012 and November 2013, 198 TKA patients were screened for eligibility in the Martini Hospital (Groningen, the Netherlands). Patients were randomly assigned to dabigatran (n=45), nadroparin (n=45) or rivaroxaban (n=48). The primary outcome was the combined endpoint of major bleeding and clinically relevant non-major bleeding. Secondary endpoints of this study were the occurrence of clinical venous thromboembolism (VTE) (pulmonary embolism or deep venous thrombosis), compliance, duration of hospital stay, rehospitalisation, adverse events and Knee Injury and Osteoarthritis Outcome Score (KOOS).

RESULTS

The primary outcome was observed in 33.3% (95% CI 20.0% to 49.0%), 24.4% (95% CI 12.9% to 39.5%) and 27.1% (95% CI 15.3% to 41.8%) of patients who received dabigatran, nadroparin or rivaroxaban, respectively (p=0.67). Major bleeding was found in two patients who received nadroparin (p=0.21). Clinically relevant non-major bleeding was observed in 33.3% (95% CI 20.0% to 49.0%), 22.2% (95% CI 11.2% to 37.1%) and 27.1% (95% CI 15.3% to 41.8%) for dabigatran, nadroparin and rivaroxaban, respectively (p=0.51). Wound haematoma was the most observed bleeding event. VTE was found in one patient who received dabigatran (p=0.65). The presurgery and postsurgery KOOS qQuestionnaires were available for 32 (71%), 35 (77%) and 35 (73%) patients for dabigatran, nadroparin and rivaroxaban, respectively. KOOS was highly variable, and no significant difference between treatment groups in mean improvement was observed.

CONCLUSIONS

A multicentre clinical trial may be feasible. However, investments will be substantial. No differences in major and clinically relevant non-major bleeding events were found between dabigatran, nadroparin and rivaroxaban during 42 days after TKA. KOOS may not be suitable to detect functional loss due to bleeding.

TRIAL REGISTRATION NUMBER

NCT01431456.

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

INTRODUCTION

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

METHODS AND MATERIALS

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

RESULTS

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

CONCLUSION

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

Efficacy and safety of dabigatran for venous thrombosis prophylaxis after knee replacement surgery in Thai patients: a prospective non-randomized controlled trial

Background

Dabigatran, a direct oral anticoagulant, has been approved for the prevention of venous thromboembolism (VTE) after orthopedic surgery in many countries. The efficacy and safety of this agent were most studied in Western countries.

Objective

To assess the efficacy and safety of dabigatran in preventing venous thromboembolic diseases after total knee arthroplasty (TKA) in Asian patients.

Methods

We conducted a prospective nonrandomized controlled study in Thai patients undergoing TKA. Thirty-two patients received 220 mg of dabigatran once daily for 14 days as thromboprophylaxis and 32 patients in the control group received none. The primary efficacy outcome was deep vein thrombosis (DVT), which was identified by color Doppler ultrasonography and/or diagnosed pulmonary embolism (PE). The primary safety outcomes were major bleeding and clinically relevant nonmajor bleeding events.

Results

There were no DVTs or PEs diagnosed in either group. The difference in the composite incidence of major and clinically relevant nonmajor bleedings between the dabigatran and control groups did not reach significant (6.2% vs. 0%, P = 0.15).

Conclusion

Dabigatran might have no clear benefit for the prevention of VTE after TKA in Thai patients. We do not recommend the routine use of dabigatran as a chemical thromboprophylaxis after TKA in Thai patients. To determine the safety profile, further study with larger sample sizes is required.

Non-Vitamin K Antagonist Oral Anticoagulants in Medical Conditions at High Risk of Thromboembolism beyond Atrial Fibrillation

Non-Vitamin K antagonist oral anticoagulants (NOACs) have been extensively investigated in medical conditions at high risk of venous or arterial thrombosis other than atrial fibrillation (AF), including hip or knee arthroplasty, acute venous thromboembolism (VTE), cancer-associated VTE, acute coronary syndrome (ACS), stable atherosclerotic vascular disease, chronic heart failure, and embolic stroke of undetermined source (ESUS). Two large ESUS trials failed to show the benefit of rivaroxaban or dabigatran, and large randomized controlled trial (RCT) data of NOACs are lacking for another potential candidates of patent foramen ovale-related stroke, acute ischemic stroke, and cerebral venous thrombosis. On the other hand, high quality evidences of NOACs have been compiled for VTE prophylaxis after hip or knee arthroplasty, acute VTE, cancer-associated VTE, and concomitant ACS and AF, which have been reflected in clinical practice guidelines. In addition, RCTs showed the benefit of very low dose rivaroxaban in combination with antiplatelet therapy in patients with ACS and in those with stable cardiovascular disease. This article summarizes the accumulated evidences of NOACs in cardiovascular diseases beyond AF, and aims to inform healthcare providers of optimal regimens tailored to individual medical conditions and help investigators design future clinical trials.

[Thromboembolic prophylaxis in orthopaedics: update on the current S3 guideline, effective 2015]

BACKGROUND

Thromboembolism is one of the most significant complications in many orthopaedic treatments and illnesses. Therefore, prevention is of vital importance.

CURRENT STATUS

The existing S3 guideline, revised in 2015, investigates the various symptoms and treatments in great detail, and thus provides very good recommendations. The difficulties of thrombosis prophylaxis in orthopaedics were ever-present in 2018, which is shown by the large number of publications on the topic. These new findings can be incorporated into further versions of the guideline, thereby adapting them to the current status. Finally, the fact that is especially important for everyday practice should be mentioned, that is, in particular when patients are transferred or discharged, information about the necessary prophylaxis is communicated to the colleagues who will be carrying out further treatment to guarantee uninterrupted prophylaxis.

Preventive Effects of Different Drugs on Asymptomatic Lower Extremities Deep Venous Thrombosis After Artificial Joint Replacement: A Mixed Treatment Comparison

This network meta-analysis aims to compare the preventive effects of 8 drugs (edoxaban, dabigatran, apixaban, rivaroxaban, warfarin, bemiparin, ximelagatran, and enoxaparin) on asymptomatic deep venous thrombosis (DVT) of lower extremities after artificial joint replacement. PubMed, Cochrane Library, and Embase were searched from their inception through October 2015 for randomized controlled trials comparing 8 drugs for the prevention of asymptomatic DVT of lower extremities after artificial joint replacement. Network meta-analysis combined the direct and indirect evidence to evaluate odd ratios (ORs) and surface under the cumulative ranking curves values. A total of 15 randomized controlled trials satisfying the inclusion criteria were enrolled. Edoxaban, apixaban, and rivaroxaban had poorer preventive effects on asymptomatic DVT of lower extremities after undergoing artificial joint replacement when compared with warfarin [OR = 0.16, 95% confidence interval (CI), 0.04-0.60; OR = 0.22, 95% CI, 0.07-0.64; OR = 0.16, 95% CI, 0.05-0.49, respectively]. When compared with enoxaparin, the preventive effects of edoxaban and rivaroxaban were poorer (OR = 0.37, 95% CI, 0.15-0.85; OR = 0.37, 95% CI, 0.21-0.59, respectively). The preventive effects of edoxaban and rivaroxaban were poorer than dabigatran (OR = 0.38, 95% CI, 0.14-0.99; OR = 0.38, 95% CI, 0.18-0.73, respectively). The surface under the cumulative ranking curves values showed that warfarin had better preventive effects on asymptomatic DVT of lower extremities after undergoing artificial joint replacement. Among the 8 drugs (edoxaban, dabigatran, apixaban, rivaroxaban, warfarin, bemiparin, ximelagatran, and enoxaparin), warfarin had better preventive effects on asymptomatic DVT of lower extremities after undergoing artificial joint replacement.

Factor Xa Inhibitors and Direct Thrombin Inhibitors Versus Low-Molecular-Weight Heparin for Thromboprophylaxis After Total Hip or Total Knee Arthroplasty: A Systematic Review and Meta-Analysis

BACKGROUND

The purpose of this study is to perform a meta-analysis to compare outcomes of venous thromboembolism (VTE) prophylaxis with low-molecular-weight heparin (LMWH) vs other anticoagulants in patients who received total knee (TKA) or total hip arthroplasty (THA).

METHODS

MEDLINE, Cochrane, EMBASE, and Google Scholar databases were searched until June 30, 2017 for eligible randomized controlled studies.

RESULTS

Thirty-two randomized controlled studies were included. LMWH provided better protection against VTE than placebo. In both TKA and THA patients, the rates of VTE were lower with factor Xa inhibitors than LMWH. In THA patients, the rate of deep vein thrombosis (DVT) was lower with factor Xa inhibitors than LMWH. In TKA patients, the rates of VTE and DVT were similar between LMWH and direct thrombin inhibitors. In THA patients, the rate of VTE was lower with direct thrombin inhibitors than with LMWH, while the DVT rates were similar. The pulmonary embolism rates were similar between all 3 classes of drugs in TKA and THR patients, as were the major bleeding rates. Nonmajor and minor bleeding rates were also similar between the 3 drug classes.

CONCLUSION

LMWH is associated with a higher rate of VTE than factor Xa inhibitors in TKA and THA patients. Direct thrombin inhibitors are associated with a lower rate of VTE in THA patients, but their effectiveness with respect to DVT and pulmonary embolism prophylaxis is similar to that of LMWH in TKA and THA patients.

Features of Pharmacodynamics of the Anticoagulant Dabigatran in Secondary Thrombophilia

One of the crucial risk factors for development of severe postthrombotic disease (PTD) is the recurrence of deep vein thrombosis (DVT). New opportunities for pharmacological thromboprophylaxis of secondary thrombophilia were associated with the direct thrombin inhibitor—Dabigatran (Pradaxa; Boehringer Ingelheim, Germany). We aimed to investigate the daily pharmacodynamics of dabigatran in healthy volunteers and patients with PTD. Treatment with dabigatran in patients with PTD having chronic chronometric hypercoagulation and structural hypocoagulation before the administration of the drug is fraught with excessive anticoagulation and a high risk of clinically significant bleeding. In patients with PTD with detected chronometric and structural hypercoagulability before taking a direct thrombin inhibitor, treatment with dabigatran is fraught with possible inadequate anticoagulation and a high risk of clinically significant relapses of thromboses. According to our data, markers of risk of hemorrhagic complications under Dabigatran are the thromboelastography indicators lying within the reference values of the healthy before the administration of the drug: fibrin–platelet clot formation, maximum amplitude of TEG; total lytic activity of blood, and thrombodynamic potential index . Monitoring the effects of the targeted anticoagulant demonstrated the need for correction of dosage and discrete use of the drug in prevention and treatment for thrombohemorrhagic complications in this category of patients. The results of the study prove the efficiency of the therapy with dabigatran and “behavior” of hemostatic potential in patients being taken into account and controlled. Therapy may be long term but requires dynamic monitoring of patients with timely dose adjustment to achieve and maintain the target level of hemostatic potential.

A rationale for universal tranexamic acid in major joint arthroplasty: overall efficacy and impact of risk factors for transfusion

BACKGROUND

Tranexamic acid (TXA) therapy is effective in reducing postoperative red blood cell (RBC) transfusion in total joint arthroplasty (TJA), yet uncertainty persists regarding comparative efficacy and safety among specific patient subgroups. We assessed the impact of a universal TXA protocol on RBC transfusion, postoperative hemoglobin (Hb), and adverse outcomes to determine whether TXA is safe and effective in TJA, both overall and in clinically relevant subgroups.

STUDY DESIGN AND METHODS

A retrospective observational study was performed on patients undergoing TJA at our institution spanning 1 year before and after the implementation of a universal protocol to administer intravenous (IV) TXA. The primary outcome was percentage of patients transfused, and secondary outcomes were perioperative Hb and occurrence of adverse events (death, myocardial infarction, stroke, seizure, pulmonary embolism, deep vein thrombosis, and acute kidney injury ). Outcomes were compared in pre- and post-protocol groups with χ² analysis. Logistic regression compared risk of transfusion in pre- and post-protocol subgroups of patients with differing risk for transfusion (anemia, body mass index [BMI], and sex).

RESULTS

No differences were found in baseline patient characteristics across pre- and post-protocol groups (n = 1084 and 912, respectively). TXA use increased from 32.3% to 92.2% while transfusion rates decreased from 10.3% to 4.8% (p < 0.001). Postoperative Day 3 Hb increased from 95.8 to 101.4 g/L (p < 0.001). Logistic regression demonstrated reduced transfusion in post-protocol subgroups regardless of sex, anemia, or BMI (p < 0.001). No increase in adverse events was observed (p = 0.8451).

CONCLUSIONS

Universal TXA was associated with a reduction of RBC transfusion, overall and in clinically relevant subgroups, strengthening the rationale for universal therapy.

Bleeding in patients receiving non-vitamin K oral anticoagulants: clinical trial evidence

In optimizing anticoagulation therapy, it is essential to balance treatment efficacy with the major adverse effect of anticoagulant treatment, bleeding risk. This narrative review examines the efficacy and safety of the non-vitamin K antagonist oral anticoagulants (NOACs) dabigatran, rivaroxaban, apixaban, and edoxaban compared with standard anticoagulation or placebo. NOAC therapies provide equivalent to superior protection versus standard therapy, with similar or superior safety, and potential benefits in convenience. We will review the phase III evidence for each of the available NOACs in different antithrombotic indications, including atrial fibrillation (in the absence of significant mitral stenosis or mechanical heart valves); prophylaxis of venous thromboembolism (VTE) in patients undergoing orthopedic surgery; and acute and long-term treatment of VTE. Further, we will illustrate scenarios in which the evidence is stronger for a particular agent in the context of the overall positive safety and efficacy profile of NOACs in general. Limitations of the factor Xa inhibitors include the lack of a specific antidote in case of a bleeding emergency (an approved agent is available for reversing the effect of the direct thrombin inhibitor). We discuss the options for mitigating bleeding and describe the ongoing developments towards specific reversal agents. In conclusion, the available data for efficacy and safety, together with reliable pharmacokinetics obviating the need for regular monitoring, indicate that NOACs may offer substantial benefits for patients with nonvalvular atrial fibrillation or VTE.

Low molecular weight heparin versus other anti-thrombotic agents for prevention of venous thromboembolic events after total hip or total knee replacement surgery: a systematic review and meta-analysis

Background

Venous thromboembolism (VTE) is an important complication following total hip replacement (THR) and total knee replacement (TKR) surgeries. Aim of this study was to comprehensively compare the clinical outcomes of low-molecular-weight heparin (LMWH) with other anticoagulants in patients who underwent TKR or THR surgery.

Methods

Medline, Cochrane, EMBASE, and Google Scholar databases were searched for eligible randomized controlled studies (RCTs) published before June 30, 2017. Meta-analyses of odds ratios were performed along with subgroup and sensitivity analyses.

Results

Twenty-one RCTs were included. In comparison with placebo, LMWH treatment was associated with a lower risk of VTE and deep vein thrombosis (DVT) (P values < 0.001) but similar risk of pulmonary embolism (PE) (P = 0.227) in THR subjects. Compared to factor Xa inhibitors, LMWH treatment was associated with higher risk of VTE in TKR subjects (P < 0.001), and higher DVT risk (P < 0.001) but similar risk of PE and major bleeding in both THR and TKR. The risk of either VTE, DVT, PE, or major bleeding was similar between LMWH and direct thrombin inhibitors in both THR and TKR, but major bleeding was lower with LMWH in patients who underwent THR (P = 0.048).

Conclusion

In comparison with factor Xa inhibitors, LMWH may have higher risk of VTE and DVT, whereas compared to direct thrombin inhibitors, LMWH may have lower risk of major bleeding after THR or TKR.

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2215-3) contains supplementary material, which is available to authorized users.

Incidence of symptomatic venous thromboembolism in 2372 knee and hip replacement patients after discharge: data from a thromboprophylaxis registry in Montreal, Canada

Background

Low-molecular-weight heparin (LMWH) is a recommended anticoagulant for thromboprophylaxis after major orthopedic surgery. Dabigatran etexilate is an oral anticoagulant recognized as noninferior to LMWH. We aimed to assess the incidence of symptomatic venous thromboembolic events (VTEs) after discharge in patients who underwent joint replacement, using a hospital registry.

Patients and methods

Patients who underwent total knee and hip arthroplasty between September 2011 and March 2015 were selected. Subcutaneous enoxaparin (30 mg twice daily) was given during hospitalization. At discharge, patients received either enoxaparin 30 mg twice daily/40 mg once daily or dabigatran 220 mg/150 mg once daily. Patients were seen or called at 2, 6, and 12 weeks after surgery. Outcomes were the number of VTEs, including deep venous thrombosis, pulmonary embolism, and the number of major/minor bleeding events after discharge.

Results

After discharge, 1468 patients were prescribed enoxaparin and 904 dabigatran (1396 total knee arthroplasty and 976 total hip arthroplasty patients). Mean age was 66±10 years, and 60% were female. The cumulative incidence of VTEs during the 12-week follow-up was 0.7%. One patient sustained a VTE during the switch window. Seven patients sustained a pulmonary embolism (0.3%). There was no statistical difference between the total knee arthroplasty and total hip arthroplasty groups. The incidence of major and minor bleeding events during follow-up was 0.3% and 30.3%, respectively. These events had a higher incidence in the dabigatran group compared to the enoxaparin group after discharge (p<0.05), but not between knee and hip replacement groups for major bleeding events.

Conclusion

A pharmaceutical prophylaxis protocol using LMWH and dabigatran during the post-discharge period resulted in low incidences of VTE and equivalence between treatments. However, the increased number of major and minor bleeding events in patients taking dabigatran is of concern regarding the safety and needs to be evaluated using analyses adjusted for risk factors.

Vitamin K antagonists

For the last decades, anticoagulation for stroke prevention in atrial fibrillation (AF) as well as for the prophylaxis and long-term treatment of venous thromboembolism has been entirely based on vitamin K antagonists (VKA). Although very effective under optimal conditions, long-term treatment with these drugs is flawed by the fact that the time in the therapeutic range frequently is suboptimal due to biological factors, drug interactions and compliance.

The direct thrombin inhibitor dabigatran, as well as the direct FXa inhibitors rivaroxaban and apixaban provide more consistent anticoagulation and have proven their efficacy and safety against VKAs in several large scale randomized clinical trials for stroke prevention in atrial fibrillation as well as for the treatment and prevention of venous thromboembolism. In view of these convincing data and other advantages such as the lack of mandatory monitoring and only few drug interactions,VKAs will most likely be replaced in a majority of patients for these indications. Based on the most recent trial evidence, the current review discusses the role of VKA treatmentand that of the novel anticoagulants.

Pharmacokinetics and pharmacodynamics in Japanese and Caucasian subjects after oral administration of dabigatran etexilate

Ethnic differences in drug disposition may potentially influence therapeutic response to dabigatran, a reversible direct thrombin inhibitor used for the prevention and/or treatment of various thromboembolic disorders. This analysis of data from 18 clinical studies in healthy volunteers and patients with non-valvular atrial fibrillation (AF) or undergoing knee or hip arthroplasty investigated whether there were any clinically relevant differences in the pharmacokinetics and pharmacodynamics of dabigatran, the active form of dabigatran etexilate, between Japanese and Caucasian subjects. In pooled data from 14 phase I trials, total exposure (i.e. area under the plasma concentration-time curve [AUC]) after administration of dabigatran 150 mg once or twice-daily was on average 20% higher in Japanese than Caucasian subjects (median [10th to 90th percentile] 1,110 [644–1,824] vs. 924 [420–1,654] ng·h/ml) although the difference between the groups was not significant. Within-trial comparisons in subjects treated with dabigatran 150 mg twice-daily showed that AUC and maximum plasma concentration differed by less than 10% between the two groups. In patients with AF, trough concentrations after administration of 150 mg twice-daily were similar in Japanese and Caucasian subjects (80.1 [34.5–193.8] vs. 71.0 [34.0–190] ng/ml). Various factors, including body weight and renal clearance, may explain these observed pharmacokinetic differences. The relationship between plasma concentration and coagulation markers was similar and indicative of no difference in the exposure-pharmacodynamic response between these two groups. In conclusion, the results of this analysis show that the pharmacokinetics and pharmacodynamics of dabigatran are similar in Japanese and Caucasian subjects and suggest that there is no need for dose adjustment of dabigatran in Japanese subjects.

Venous thromboembolism prevention with fondaparinux 1.5 mg in renally impaired patients undergoing major orthopaedic surgery

Despite the need for effective and safe thromboprophylactic drugs for patients with renal impairment, clinical trial data on anticoagulant agents are limited in this population. The study aim was to assess in the real-world setting the use of the once-daily 1.5 mg reduced dosage regimen of fondaparinux available for this context. In this prospective cohort study, patients with a creatinine clearance (CrCl) of 20–50 ml/ minute, undergoing total hip (THR) or knee (TKR) replacement or hip fracture surgery (HFS) received fondaparinux thromboprophylaxis. Main clinical outcomes were bleeding (major/clinically relevant nonmajor), symptomatic venous thromboembolism (VTE) and death. Overall, 442 patients (353 women; median age: 82 years; 39.4% in ASA class ≥3; mean ± SD CrCl: 39.0 ± 8.0 ml/minute; 78% with additional risk factors for bleeding), undergoing THR (43.7%), TKR (27.6%), or HFS (28.7%) received fondaparinux 1.5 mg for a mean ± SD duration of 16.0 ± 12.5 days. At postoperative day 10, the rates (95% confidence interval) of major bleeding, clinically relevant bleeding and symptomatic VTE were 4.5% (2.8–6.9), 0.5% (0.1–1.6) and 0.5% (0.05–1.62), respectively; no fatal bleeding, bleeding into a critical organ, pulmonary embolism or proximal deep-vein thrombosis occurred. Corresponding rates at one month were 5.2%, 0.7% and 0.7%. One-month mortality was 2.3% (0.9–3.6). This large clinical prospective study provides for the first time, under conditions reflecting “real-world” routine clinical practice, data on the bleeding and VTE risks of thromboprophylaxis with fondaparinux 1.5 mg after major orthopaedic surgery in renally impaired patients. It shows that these patients constitute a very elderly and fragile population.

ClinicalTrials.gov number, NCT00555438

A combined pharmacometric analysis of dabigatran etexilate in healthy volunteers and patients with atrial fibrillation or undergoing orthopaedic surgery

Dabigatran etexilate is the orally bioavailable pro-drug of dabigatran, a direct thrombin inhibitor. Using data from eight clinical studies in healthy volunteers and patients with non-valvular atrial fibrillation (AF) or undergoing orthopaedic surgery (OS), population pharmacokinetic (PK) and pharmacodynamic (PD) models were developed to investigate whether the PK and PD of dabigatran differ across different populations. In both healthy volunteers (n=80) and patients (n=1,965), the PK of dabigatran was best described by a two-compartment disposition model with first-order absorption and elimination. Renal function was the only covariate shown to have a clinically relevant impact on dabig-atran exposure. The patient PK model was successfully applied in predicting exposure observed in the RE-LY trial evaluating dabigatran treatment in patients with non-valvular AF. The relationship between dabigatran plasma concentrations and activated partial thromboplastin time in healthy volunteers and patients (n=762) was best described with a combination of a linear model and a maximum effect (Emax) model, consistent with previous reports. PK/PD relationships were robust across the various populations tested and were not affected by any of the covariates examined. In summary, the PK of dabigatran is sufficiently consistent to allow extrapolation of data generated in healthy volunteers to patients with AF or undergoing OS.

Darexaban (YM150) versus enoxaparin for the prevention of venous thromboembolism after total hip arthroplasty: a randomised phase IIb dose confirmation study (ONYX-3)

This double-blind, double-dummy, randomised, phase IIb study (NCT00902928) evaluated different dosing regimens of darexaban compared with enoxaparin (randomised 1:1:1:1:1 to 15 mg twice daily [bid], 30 mg once daily [qd], 30 mg bid or 60 mg qd or enoxaparin 40 mg qd) in patients undergoing elective total hip arthroplasty. Patients, investigators, pharmacists and sponsor were all blinded to treatment allocation. Darexaban administration started 6-10 hours (h) post-surgery. Enoxaparin 40 mg qd administration started 12 ± 2 h before surgery. Treatment continued for 35 days. Bilateral venography was performed on Day 10 ± 2. The primary efficacy outcome was total VTEs (composite of proximal/distal deep-vein thrombosis, pulmonary embolism) or death, at Day 12. Total VTE rates were similar across all groups. There was no apparent difference in efficacy between onceand twice-daily darexaban (odds ratio [OR] 1.00; 95% confidence interval [CI] 0.71–1.42; p=0.988), or total daily dose (30 mg/day vs 60 mg/day; OR 0.81; 95% CI 0.57–1.15; p=0.244). There was no significant difference in major and/or clinically relevant non-major bleeding between darexaban qd or bid, or between total daily doses of 30 mg or 60 mg, and also for any dosing regimen of darexaban vs enoxaparin. Darexaban was well tolerated, without signs of liver toxicity. In conclusion, darexaban, administered qd or bid, and at total daily doses of 30 mg or 60 mg, appears to be effective for VTE prevention and was well tolerated. Data suggest no significant differences between a once- or twice-daily dosing regimen.

A randomised study in healthy volunteers to investigate the safety, tolerability and pharmacokinetics of idarucizumab, a specific antidote to dabigatran

Idarucizumab, a monoclonal antibody fragment that binds dabigatran with high affinity, is in development as a specific antidote for dabigatran. In this first-in-human, single-rising-dose study, we investigated the pharmacokinetics, safety and tolerability of idarucizumab. Healthy male volunteers aged 18–45 years received between 20 mg and 8 g idarucizumab as a 1-hour intravenous infusion in 10 sequential dose groups, or 1, 2 or 4 g idarucizumab as a 5-minute infusion. Subjects within each dose group were randomised 3:1 to idarucizumab or placebo. A total of 110 randomised subjects received study drug (27 placebo, 83 idarucizumab). Peak and total exposure to idarucizumab increased proportionally with dose. Maximum plasma concentrations were achieved near the end of infusion, followed by a rapid decline, with an initial idarucizumab half-life of ∼45 minutes. For the 5-minute infusions, this resulted in a reduction of plasma concentrations to less than 5 % of peak within 4 hours. Idarucizumab (in the absence of dabigatran) had no effect on coagulation parameters or endogenous thrombin potential. Overall adverse event (AE) frequency was similar for idarucizumab and placebo, and no relationship with idarucizumab dose was observed. Drug-related AEs (primary endpoint) were rare (occurring in 2 placebo and 3 idarucizumab subjects) and were mostly of mild intensity; none of them resulted in study discontinuation. In conclusion, the pharmacokinetic profile of idarucizumab meets the requirement for rapid peak exposure and rapid elimination, with no effect on pharmacodynamic parameters. Idarucizumab was safe and well tolerated in healthy males.

Clinical trial registration: http://clinicaltrials.gov/ct2/show/NCT01688830?term=NCT01688830&rank=1 (NCT01688830).

Effects of different anticoagulant drugs on the prevention of complications in patients after arthroplasty: A network meta-analysis

BACKGROUND

After arthroplasty treatment, some complications commonly occur, such as early revision, infection/dislocation, and venous thromboembolism (VTE). This study aims to use a network meta-analysis to compare effects of 9 anticoagulant drugs (edoxaban, dabigatan, apixaban, rivaroxaban, warfarin, heparin, bemiparin, ximelagatran, and enoxaparin) in preventing postoperative complications in arthroplasty patients.

METHODS

After retrieving PubMed, Embase, and Cochrane Library database from the inception to November 2016, randomized controlled trials were enrolled. The integration of direct and indirect evidences was performed to calculate odd ratios and the surface under the cumulative ranking curves. Nineteen eligible randomized controlled trials were included.

RESULTS

The network meta-analysis results showed that compared with warfarin, edoxaban, apixaban, and rivaroxaban had a lower incidence rate in asymptomatic deep venous thrombosis, which indicated that edoxaban, apixaban, and rivaroxaban had better effects on prevention. Similarly, in comparison to enoxaparin, edoxaban and rivaroxaban had better effect; rivaroxaban was better than ximelagatran in preventive effects. Compared with apixaban, edoxaban, dabigatan, rivaroxaban, and enoxaparin had a higher incidence rate in clinically relevant non-major bleeding, which showed that preventive effects were relatively poor. In addition, the results of the surface under the cumulative ranking curves showed that rivaroxaban and bemiparin worked best on symptomatic deep venous thrombosis and pulmonary embolism. In terms of bleeding, apixaban and warfarin had better preventive effects.

CONCLUSION

Our findings suggested that rivaroxaban may work better in terms of symptomatic deep venous thrombosis and pulmonary embolism, whereas apixaban had better preventive effects in bleeding.

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.

Direct oral anticoagulants and venous thromboembolism

Venous thromboembolism (VTE), consisting of deep vein thrombosis and pulmonary embolism, is a major clinical concern associated with significant morbidity and mortality. The cornerstone of management of VTE is anticoagulation, and traditional anticoagulants include parenteral heparins and oral vitamin K antagonists. Recently, new oral anticoagulant drugs have been developed and licensed, including direct factor Xa inhibitors (e.g. rivaroxaban, apixaban and edoxaban) and thrombin inhibitors (e.g. dabigatran etexilate). This narrative review focusses on the characteristics of these direct anticoagulants and the main results of published clinical studies on their use in the prevention and treatment of VTE.

Patient compliance with new oral anticoagulants after major orthopaedic surgery: rivaroxaban and dabigatran compared with subcutaneous injection of fondaparinux

PURPOSE

the main purpose of our study was to compare patient compliance with the orally administered new oral anticoagulants (NOCs) dabigatran and rivaroxaban compared with subcutaneously injected fondaparinux after major orthopaedic surgery, and to assess patient preference for the oral vs subcutaneous administration route.

METHODS

prophylactic antithrombotic drug therapy with dabigatran (group D; GD, n=32 patients), rivaroxaban (group R; GR, n=38 patients) or fondaparinux (group F; GF, n=30 patients), to prevent deep vein thrombosis, was started immediately after surgery in 100 patients submitted to total hip arthroplasty.

RESULTS

the patients had a mean age of 68.7±11 years and 62% were female. In GD, 87.5% of patients indicated that they preferred oral intake of medications to subcutaneous injection (12.5%). In GR, 84.2% declared a preference for oral administration over subcutaneous injection (15.8%). In GF, a surprisingly high proportion of patients (73.3%; p < 0.001) declared that they preferred subcutaneous administration of medications over the oral route (26.7%). Overall, the rate of compliance with antithrombotic drug therapy was very high, at 99%.

CONCLUSIONS

intake of the NOAs dabigatran and rivaroxaban following hospital discharge is entirely the responsibility of the patient; a high level of patient compliance with these drugs must therefore be demonstrated in order for them to become well accepted within the medical community. The results of this study showed a very high level of compliance both with orally and subcutaneously administered drugs.

LEVEL OF EVIDENCE

Level I, randomized clinical study.

Dabigatran etexilate for thromboprophylaxis in over 5000 hip or knee replacement patients in a real-world clinical setting

BACKGROUND

Thromboprophylaxis is recommended for patients undergoing total hip or total knee replacement (THR, TKR). An international, open-label, prospective, observational, single-arm study in a routine clinical setting was performed to assess the safety and efficacy of dabigatran etexilate 220 mg once daily in patients undergoing THR or TKR, and in subgroups of patients with potentially increased risk of bleeding or venous thromboembolism (VTE).

MATERIALS AND METHODS

Patients were ≥18 years and required to be eligible to receive dabigatran 220 mg once daily (first dose 110 mg 1-4 h after THR/TKR surgery) according to the European Summary of Product Characteristics. The primary safety and efficacy outcomes were incidence of major bleeding events (MBEs), and the composite incidence of symptomatic VTE events and all-cause mortality, respectively.

RESULTS

In total, 5292 patients (median age 64 years) were enrolled and received dabigatran (2734 THR and 2558 TKR). Median drug exposure was 31 days (THR 34 days; TKR 27 days). Overall incidence of MBEs was 0.72 % (95 % confidence interval [CI] 0.51, 0.98), and this rate was comparable between types of surgery and was not significantly affected by protocol-defined risk factors. The overall incidence of symptomatic VTE and all-cause mortality was 1.04 % (95 % CI 0.78, 1.35); the only significant risk factor was history of VTE events (odds ratio 5.59; 95 % CI 2.53, 11.08). A post-hoc analysis showed that the incidence of MBEs in this observational study was similar to or lower than those reported in previous phase 3 trials.

CONCLUSIONS

Results from this observational study of dabigatran etexilate administered to patients undergoing THR or TKR surgery are reassuring and supportive of those obtained in dabigatran phase 3 trials.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00846807.

The Prevention of Venous Thromboembolism in Surgical Patients

Patients undergoing surgery are at an increased risk of VTE. Since the early 1990s the prevention of VTE has been dominated by the administration of low-molecular weight heparin during admission. New oral anticoagulants have been extensively researched and have increased in popularity. This chapter reviews why surgical patients are at increased risk of VTE and summaries both the pharmacological and mechanical methods of prophylaxis available.

The evolution of anticoagulant therapy

Arterial and venous thromboembolism are leading causes of morbidity and mortality around the world. For almost 70 years, heparins (unfractionated heparin and low molecular weight heparins) and vitamin K antagonists have been the leading therapeutic medical options for the treatment and prevention of thromboembolic disorders. Nevertheless, the many limitations of these traditional anticoagulants have fuelled the search for novel agents over the past 15 years, and a new class of oral anticoagulants that specifically target activated factor X and thrombin has been developed and is now commercially available. In this narrative review, the evolution of anticoagulant therapy is summarised, with a focus on newer oral anticoagulants.

Oral dabigatran etexilate versus enoxaparin for venous thromboembolism prevention after total hip arthroplasty: pooled analysis of two phase 3 randomized trials

Background

Two phase 3 trials compared 28–35 days of treatment with oral dabigatran 220 mg or 150 mg (RE-NOVATE) or 220 mg (RE-NOVATE II) once daily with subcutaneous enoxaparin 40 mg once daily for prevention of venous thromboembolism (VTE) after elective total hip arthroplasty.

Methods

This prespecified pooled analysis compared the outcomes for the dabigatran 220 mg dose with enoxaparin, which included 4,374 patients. Total VTE (venographic and symptomatic) plus all-cause mortality (primary efficacy), major VTE (proximal deep vein thrombosis [DVT] or non-fatal pulmonary embolism) plus VTE-related death, and bleeding events were evaluated. Efficacy analysis was based on the modified intention-to-treat (ITT) population and safety analysis was based on all treated patients. The common risk difference (RD) for dabigatran versus enoxaparin was estimated using a fixed effects model.

Results

Total VTE and all-cause mortality occurred in 6.8 % (114/1,672) and 7.7 % (129/1,682) (RD:–0.8 %, 95 % confidence interval [CI] –2.6 to 0.9) for dabigatran and enoxaparin, respectively. Major VTE plus VTE-related mortality occurred in 2.7 % (46/1,714) and 4.0 % (69/1,711) (RD: –1.4 %, 95 % CI –2.6 to –0.2) of patients receiving dabigatran 220 mg and enoxaparin, respectively. Major bleeding occurred in 1.7 % (37/2,156) and 1.3 % (27/2,157) (RD: 0.5 %, 95 % CI –0.2 to 1.2), for dabigatran and enoxaparin respectively.

Conclusions

Extended prophylaxis with oral dabigatran 220 mg once daily was as effective as enoxaparin 40 mg once daily in reducing the risk of total VTE and all-cause mortality after total hip arthroplasty, with a similar bleeding profile. The clinically relevant outcome of major VTE and VTE-related death was significantly reduced with dabigatran versus enoxaparin.

Trial registration

NCT00657150 and NCT00168818

The effect of ultrafiltration with cardiopulmonary bypass on the removal of dabigatran from the circulation of adult pigs

Objective:

Dabigatran etexilate is a direct thrombin inhibitor approved for use in patients with non-valvular atrial fibrillation. There is no currently available pharmacological therapy to reverse this renally cleared anticoagulant. Dabigatran has a low level of plasma protein binding and has been considered dialyzable. We used a pig model with renal artery ligation to exclude intrinsic drug excretion to examine the efficacy of ultrafiltration (UF) during cardiopulmonary bypass (CPB) for dabigatran removal.

Method:

Dabigatran was intravenously infused (20 mg) in Yorkshire pigs (male, n=7, 70±1 kg) following renal artery ligation. CPB with UF was initiated after heparinization and continued until a total volume of 6 liters of UF effluent was removed. Serial labs, including dabigatran concentration, activated coagulation times (ACT), hematocrit and creatinine were drawn at intervals before the start of CPB and then incrementally during UF (0, 2, 4 and 6 L removed). Hemodialysis (HD) was performed on one animal following UF.

Results:

Dabigatran concentration (ng/mL) rose from undetectable levels at baseline to 296±70 (p<0.05) at the conclusion of infusion, but dropped significantly upon administration of heparin (178±40, p<0.05). A further decrement in dabigatran concentration was observed from the administration of heparin to the start of CPB (to 135±28, p<0.05). Once on CPB, dabigatran remained stable, with the end UF (eUF) dabigatran concentration being 133±34. Dabigatran concentration in the UF effluent was measured in one animal and was 98.8, with 6 L of effluent having been removed. The total recovery of dabigatran was calculated to be less than 5%. Dabigatran concentrations also did not decrease appreciably with HD on CPB following UF.

Conclusions:

UF in conjunction with CPB was ineffective at removing dabigatran. Heparin demonstrated a dabigatran-lowering effect, suggesting a possible drug interaction or assay impairment. Based on these findings, emergent cardiac surgery with UF on cardiopulmonary bypass to remove dabigatran is not advisable. Alternative forms of drug removal or reversal must be identified.

Unmet Needs in Anticoagulant Therapy: Potential Role of Rivaroxaban

The new generation of non-vitamin K antagonist oral anticoagulants (NOACs) have been welcomed as a convenient alternative to warfarin. Three new oral anticoagulants, dabigatran etexilate, rivaroxaban and apixaban have been approved for the prevention of stroke and systemic embolism (SSE) in patients with atrial fibrillation (AF) and the prevention of venous thromboembolic events (VTEs) in patients who have undergone elective hip or knee replacement surgery. Dabigatran etexilate and rivaroxaban are also indicated for the treatment of VTE and the long-term prevention of recurrent deep vein thrombosis (DVT) and pulmonary embolism (PE). A fourth agent, edoxaban, has been successfully tested for several indications but is not yet approved for use in North America or Europe. Building on these successes, new trials are planned to address remaining unmet needs and knowledge gaps. This paper examines the unresolved issues in anticoagulant therapy with a focus on planned and ongoing trials.

Current and emerging strategies in the management of venous thromboembolism: benefit-risk assessment of dabigatran

Venous thromboembolism (VTE) is a disease state that carries significant morbidity and mortality, and is a known cause of preventable death in hospitalized and orthopedic surgical patients. There are many identifiable risk factors for VTE, yet up to half of VTE incident cases have no identifiable risk factor and carry a high likelihood of recurrence, which may warrant extended therapy. For many years, parenteral unfractionated heparin, low-molecular weight heparin, fondaparinux, and oral vitamin K antagonists (VKAs) have been the standard of care in VTE management. However, limitations in current drug therapy options have led to suboptimal treatment, so there has been a need for rapid-onset, fixed-dosing novel oral anticoagulants in both VTE treatment and prophylaxis. Oral VKAs have historically been challenging to use in clinical practice, with their narrow therapeutic range, unpredictable dose responsiveness, and many drug-drug and drug-food interactions. As such, there has also been a need for novel anticoagulant therapies with fewer limitations, which has recently been met. Dabigatran etexilate is a fixed-dose oral direct thrombin inhibitor available for use in acute and extended treatment of VTE, as well as prophylaxis in high-risk orthopedic surgical patients. In this review, the risks and overall benefits of dabigatran in VTE management are addressed, with special emphasis on clinical trial data and their application to general clinical practice and special patient populations. Current and emerging therapies in the management of VTE and monitoring of dabigatran anticoagulant-effect reversal are also discussed.

New oral pharmacotherapeutic agents for venous thromboprophylaxis after total hip arthroplasty

Patients undergoing total hip arthroplasty (THA) are at high risk for developing venous thromboembolism and, therefore, require short term prophylaxis with antithrombotic agents. Recently, target specific oral anticoagulants (TSOA) including the direct thrombin inhibitor, dabigatran, and the factor Xa inhibitors rivaroxaban, apixaban, and edoxaban have been approved for THA thrombopropylaxis in various countries. The TSOAs provide a rapid acting, oral alternative to parenteral agents including low-molecular weight heparins (LMWH) and fondaparinux; and compared to warfarin, they do not require routine laboratory monitoring and possess much fewer drug-drug interactions. Based on phase III clinical studies, TSOAs have established themselves as an effective and safe option for thromboprophylaxis after THA compared to LMWH, particularly enoxaparin, but require additional evaluation in specific populations such as the renally impaired or elderly. The ability to monitor and reverse these TSOAs in the case of bleeding complications or suspected sub- or supra-therapeutic anticoagulation is of importance, but remains investigational. This review will focus on the drug-specific characteristics, efficacy, safety, and economic impact of the TSOAs for thromboprophylaxis following THA, as well as the aspects of therapeutic monitoring and anticoagulation reversal in the event of bleeding complications or a need for urgent reversal.

Hip arthroplasty fatality related to dabigatran induced gastrointestinal haemorrhage

We report a fatality due to massive gastrointestinal haemorrhage in a patient receiving prophylactic dabigatran etexilate following a total hip replacement. A 79-year-old woman was commenced on dabigatran for venous thromboembolic prophylaxis following a total hip replacement. She presented again four days after surgery with haematemesis and hypotension but her coagulopathy could not be corrected, leading to her death. This case highlights the lack of reversal agent for dabigatran etexilate that resulted in this fatal complication.

The use of novel oral anticoagulants for thromboprophylaxis after elective major orthopedic surgery

Venous thromboembolism is a common cause of morbidity and mortality among patients undergoing elective orthopedic surgery. Due to the high incidence of venous thromboembolism in this setting, perioperative anticoagulation is the recommended approach for thromboprophylaxis. Low molecular weight heparin (LMWH), fondaparinux and warfarin are the agents commonly used for thromboprophylaxis. The well-recognized limitations of warfarin and the inconvenience and discomfort associated with the subcutaneous administration of low molecular weight heparin and fondaparinux inspired intense investigation to develop novel oral anticoagulants (NOACs) with more predictable pharmacokinetics, fewer drug interactions and no need for regular laboratory monitoring. Three NOACs have been demonstrated to be effective for thromboprophylaxis after total hip arthroplasty (THA) and total knee arthroplasty (TKA) in large randomized controlled trials. Here we review the pharmacology of rivaroxaban, dabigatran, and apixaban, summarize the major clinical trials of these agents in thromboprophylaxis after THA and TKA, and discuss the clinical factors to be considered by providers when selecting a NOAC for their patients.