Extended Thromboprophylaxis with Low Molecular Weight Heparin Reduces Symptomatic Venous Thromboembolism following Lower Limb Arthroplasty - a Meta-analysis

Pharmacological thromboprophylaxis to prevent venous thromboembolism in patients with temporary lower limb immobilization after injury: systematic review and network meta-analysis

BACKGROUND

Thromboprophylaxis has the potential to reduce venous thromboembolism (VTE) following lower limb immobilization resulting from injury.

OBJECTIVES

We aimed to estimate the effectiveness of thromboprophylaxis, compare different agents, and identify any factors associated with effectiveness.

METHODS

We undertook a systematic review and network meta-analysis (NMA) of randomized trials reporting VTE or bleeding outcomes that compared thromboprophylactic agents with each other or to no pharmacological prophylaxis, for this indication. An NMA was undertaken for each outcome or agent used, and a series of study-level network meta-regressions examined whether population characteristics, type of injury, treatment of injury, or duration of thromboprophylaxis were associated with treatment effect.

RESULTS

Data from 6857 participants across 13 randomized trials showed that, compared with no treatment, low molecular weight heparin (LMWH) reduced the risk of any VTE (odds ratio [OR]: 0.52; 95% credible interval [CrI]: 0.37-0.71), clinically detected deep vein thrombosis (DVT) (OR: 0.39; 95% CrI: 0.12-0.94) and pulmonary embolism (PE) (OR: 0.16; 95% CrI: 0.01-0.74), whereas fondaparinux reduced the risk of any VTE (OR: 0.13; 95% CrI: 0.05-0.30) and clinically detected DVT (OR: 0.10; 95% CrI: 0.01-0.86), with inconclusive results for PE (OR: 0.40; 95% CrI: 0.01-7.53).

CONCLUSIONS

Thromboprophylaxis with either fondaparinux or LMWH appears to reduce the odds of both asymptomatic and clinically detected VTE in people with temporary lower limb immobilization following an injury. Treatment effects vary by outcome and are not always conclusive. We were unable to identify any treatment effect modifiers other than thromboprophylactic agent used.

Extended-duration betrixaban versus shorter-duration enoxaparin for venous thromboembolism prophylaxis in critically ill medical patients: an APEX trial substudy

PURPOSE

To assess the efficacy and safety of betrixaban for venous thromboembolism (VTE) prophylaxis among critically ill patients.

METHODS

The APEX trial randomized 7513 acutely ill hospitalized patients to betrixaban for 35-42 days or enoxaparin for 10 ± 4 days. Among those, 703 critically ill patients admitted to the intensive care unit were included in the analysis, and 547 patients who had no severe renal insufficiency or P-glycoprotein inhibitor use were included in the full-dose stratum. The risk of VTE, bleeding, net clinical benefit (composite of VTE and major bleeding), and mortality was compared at 35-42 days and at 77 days.

RESULTS

At 35-42 days, extended betrixaban reduced the risk of VTE (4.27% vs 7.95%, P = 0.042) without causing excess major bleeding (1.14% vs 3.13%, P = 0.07). Both VTE (3.32% vs 8.33%, P = 0.013) and major bleeding (0.00% vs 3.26%, P = 0.003) were decreased in the full-dose stratum. Patients who received betrixaban had more non-major bleeding than enoxaparin (overall population: 2.56% vs 0.28%, P = 0.011; full-dose stratum: 3.32% vs 0.36%, P = 0.010). Mortality was similar at the end of study (overall population: 13.39% vs 16.19%, P = 0.30; full-dose stratum: 13.65% vs 16.30%, P = 0.39).

CONCLUSIONS

Compared with shorter-duration enoxaparin, critically ill medical patients who received extended-duration betrixaban had fewer VTE without more major bleeding events. The benefit of betrixaban was driven by preventing asymptomatic thrombosis and offset by an elevated risk of non-major bleeding. The APEX trial did not stratify by intensive care unit admission and the present study included a highly selected population of critically ill patients. These hypothesis-generating findings need to be validated in future studies.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov . Unique identifier: NCT01583218.

Symptoms and clinical relevance: A dilemma for clinical trials on prevention of venous thromboembolism

The outcomes of thromboprophylactic trials have been debated for decades. Recently, the 9th edition of the American College of Chest Physicians (ACCP) evidence-based clinical practice guidelines based their strong recommendations only on patient-important outcomes. Practically, symptoms were considered the crucial element. Consequently, studies that primarily aimed at reducing venographic thrombi were considered less pertinent than studies that focused on symptomatic thrombosis. In the present viewpoint, we challenge the argument that “symptomatic” and “clinically relevant” are interchangeable. In particular, the case is made that asymptomatic events may be clinically relevant and that asymptomatic venographically detected thrombosis is a clinically relevant surrogate outcome for fatal pulmonary embolism.

Low dose compared to variable dose Warfarin and to Fondaparinux as prophylaxis for thromboembolism after elective hip or knee replacement surgery; a randomized, prospective study

Background

Deep vein thrombosis (DVT) and pulmonary emboli (PE), known together as venous thromboembolic (VTE) disease remain major complications following elective hip and knee surgery. This study compares three chemoprophylactic regimens for VTE following elective primary unilateral hip or knee replacement, one of which was designed to minimize risk of post-operative bleeding.

Methods

Patients were randomized and stratified for hip vs. knee to receive A: variable dose warfarin (first dose on the night preceding surgery with subsequent target INR 2.0–2.5), B: 2.5 mg fondaparinux daily starting 6–18 h postoperatively, or C: fixed 1.0 mg dose warfarin daily starting 7 days preoperatively. All treatments continued until bilateral leg venous ultrasound day 28 ± 2 or earlier upon a VTE event. The study examined primary endpoints including leg DVT, PE or death due to VTE and secondary endpoints including effects on D-dimer, estimated blood loss (EBL) at surgery and hemorrhagic complications.

Results

Three hundred fifty-five patients were randomized. None was lost to follow-up. Taking 1.0 mg warfarin for seven days preoperatively did not prolong the prothrombin time (PT). Two patients in Arm C had asymptomatic distal DVT. One major bleed occurred in Arm B and one in Arm C (ischemic colitis). Elevated d-dimer did not predict delayed VTE for one year.

Conclusions

Fixed low dose warfarin started preoperatively is equivalent to two other standards of care under study (95 % CI: -0.0428, 0.0067 for both) as VTE prophylaxis for the patients having elective major joint replacement surgery.

Trial registration

ClinicalTrials.gov identifier # NCT00767559

FDA IND: 103,716

The incidence of deep vein thrombosis and pulmonary embolism following cast immobilisation and early functional bracing of Tendo Achilles rupture without thromboprophylaxis

PURPOSE

The routine use of thromboprophylaxis during cast immobilisation for lower leg trauma is controversial. The concern involves the perceived increased risk of deep vein thrombosis (DVT) and its sequelae following leg immobilisation. However, immobilisation is used for a spectrum of trauma and for varying duration. This heterogenicity in management is reflected in the current evidence and coupled with the risks of thromboprophylaxis; no clear consensus has been made.

METHODS

In this retrospective study, we report the incidence of DVT and pulmonary embolism (PE) observed following cast immobilisation and early functional management of patients with Tendo Achilles rupture. Over 12 years, 945 consecutive patients (949 tendons) were treated without additional thromboprophylaxis.

RESULTS

The incidence of DVT was 1.05 % and PE was 0.32 %. Females were significantly more likely to develop a DVT but not a PE. When compared to the incidence of DVT and PE observed in the general population, DVT rate was statistically significantly higher than that observed in the general population. There was no significant difference in PE rates. The number needed to treat to reduce the DVT incidence is 106. The number needed to treat to reduce the PE incidence is 475.

CONCLUSIONS

Although we can conclude that conservative treatment for Tendo Achilles does increase the incidence of symptomatic DVT from the general population, we feel that large randomised control trials are required to evaluate the efficacy, compliance and cost effectiveness of routine DVT thromboprophylaxis in the outpatient setting.

Antithrombotic prophylaxis in major orthopaedic surgery: an historical overview and update of current recommendations

The risk of venous thromboembolism following major orthopaedic procedures, such as joint arthroplasty and hip fracture surgery, are well recognised and represent one of the major challenges in orthopaedic practice, having in mind the increasing number of arthroplasties of the hip and knee done worldwide per year and their successful outcome. This potentially fatal complication remains a challenge in orthopaedic practice. The percentage of patients in whom antithrombotic prophylaxis has not been administrated or has been inadequate may reach 50%. Until recently, anticoagulant prophylaxis with low molecular weight heparins (LMWHs) has been a "gold standard". LMWHs are indirect inhibitors of the clotting factors Xa and thrombin and are administered by daily subcutaneous injection. Their efficacy has been proven in numerous clinical trials and the rate of complications with their use is relatively low. However these compounds are associated with a failure rate and are inconvenient to administer, requiring subcutaneous injection, leading to inadequate compliance. For these reasons postoperative thrombembolism continues to occur in up to 10% of this patient population. Recently, novel oral anticoagulants have been introduced into practice for thromboprophylaxis after joint arthroplasy and hip fracture surgery. These drugs are direct thrombin inhibitors (dabigatran) or direct factor Xa inhibitors (rivaroxaban, apixaban and edoxaban). These oral drugs have the same efficacy as the LMWHs with the same or slightly more clinically significant haemorrhage as their main side effect. Their ease of administration and favourable clinical profile makes them an important addition to the therapeutic armamentarium available for venous thromboprophylaxis. In this paper we review the aetiology and pathogenesis of venous thromboembolism and present the various alternatives for its prevention after major orthopaedic surgical procedures with emphasis on the new oral drugs.

Clinical Venous Thromboembolism Following Joint Surgery

We describe annual incidences and 6-month postoperative patterns of clinical venous thromboembolism (VTE) in 9078 patients undergoing major joint surgery in a Scandinavian hospital. In cohort I (1989-1999), low-molecular-weight heparin thromboprophylaxis for 7 to 10 days was uniformly introduced, 5-week thromboprophylaxis becoming routine after total hip replacement (THR), partially applied after hip fracture surgery (HFS), but not used after total knee replacement (TKR) thereafter (2003-2011; cohort II). Mean annual VTE incidence was lower in cohort II than in cohort I after THR and HFS but not after TKR. In cohort I, the cumulative VTE incidence increased sharply during the first 5 postoperative weeks in all groups, subsequently plateauing up to 6 months postsurgery. In cohort II, this incidence remained low and stable during 5 weeks post-THR, rising gradually up to 6 months, with a comparable but less pronounced pattern following HFS but not TKR. In conclusion, the VTE risk after major joint surgery seems to persist after 5- and 1-week prophylaxis in patients undergoing hip surgery and TKR, respectively.

NOACs for thromboprophylaxis in medical patients

The risk of venous thrombosis extends for an indeterminate length of time following admission to hospital with a medical or surgical condition. Observational studies in surgery show this risk extends for months and perhaps more than one year, for medical patients the risk extends for at least several weeks. Large bodies of evidence support the heightened risk status of hospitalised surgical and medical patients, and that prophylactic measures significantly reduce the risk of thrombosis. Extending thromboprophylaxis for 4-6 weeks with anticoagulants both old and new has been shown to be efficacious and safe in surgical patients. However in populations of medical patients although prolonged anticoagulant thromboprophylaxis has been shown to be efficacious it also results in more bleeding and the risk benefit is not clear. Hence no therapies are approved for prolonged thromboprophylaxis in medical patients. In this area there have been one phase III study of low molecular weight heparin and two completed phase III studies of NOACs. This article briefly summarises our understanding of the background to preventing venous thromboembolism in hospitalised medical patients and reviews the details of the studies using NOACs.

Symptomatic venous thromboembolism and mortality in orthopaedic surgery - an observational study of 45 968 consecutive procedures

Background

Little information exists on the presentation of symptomatic venous thromboembolism (VTE) in orthopaedic surgery when a defined protocol for thromboprophylaxis is used. The objective with this study was to establish the VTE rate and mortality rate in orthopaedic surgery.

Methods

We performed a prospective, single centre observational cohort study of 45 968 consecutive procedures in 36 388 patients over a 10 year period. Follow-up was successful in 99.3%. The primary study outcome was the incidence of symptomatic deep vein thrombosis (DVT), symptomatic pulmonary embolism (PE) and mortality at 6 weeks, specified for different surgical procedures. The secondary outcome was to describe the DVT distribution in proximal and distal veins and the proportion of VTEs diagnosed after hospital discharge. For validation purposes, a retrospective review of VTEs diagnosed 7–12 weeks postoperatively was also performed.

Results

In total, 514 VTEs were diagnosed (1.1%; 95% CI: 1.10-1.14), the majority (84%) after hospital discharge (432 out of 514).With thromboprophylaxis, high incidence of VTE was found after internal fixation (IF) of pelvic fracture (12%; 95% CI: 5–26), knee replacement surgery (3.7%; 95% CI: 2.8-5.0), after internal fixation (IF) of proximal tibia fracture (3.8%; 95% CI: 2.3-6.3) and after IF of ankle fracture (3.6%; 95% CI: 2.9-4.4). Without thromboprophylaxis, high incidence of VTE was found after Achilles tendon repair (7.2%; 95% CI: 5.5-9.4). In total 1094 patients deceased (2.4%; 95% confidence interval (CI): 2.33- 2.44) within 6 weeks of surgery. Highest mortality was seen after lower limb amputation (16.3%, CI: 13.8-19.1) and after hip hemiarthroplasty due to hip fracture (9.6%, CI; 7.6-12.1).

Conclusion

The overall incidence of VTE is low after orthopaedic surgery but our study highlights surgical procedures after which the risk for VTE remains high and improved thromboprophylaxis is needed.

Thromboprophylaxis for deep vein thrombosis and pulmonary embolism after total joint arthroplasty in a low incidence population

Postoperative venous thromboembolism is one of the most serious complications following total joint arthroplasty. Pharmacological and mechanical prophylaxis methods are used to reduce the risk of postoperative symptomatic deep vein thrombosis and pulmonary embolism. Use of pharmacological prophylaxis requires a fine balance between the efficacy of the drug in preventing deep vein thrombosis and the adverse effects associated with the use of these drugs. In regions with a low prevalence of deep vein thrombosis such as Korea, there might be a question whether the benefits of using pharmacological prophylaxis outweigh the risks involved. The current article reviews the need for thromboprophylaxis, guidelines, problems with the guidelines, pharmacological prophylaxis use, and the current scenario of deep vein thrombosis, and discusses whether the use of pharmacological prophylaxis should be mandatory in low incidence populations.

The incidence of pulmonary embolism and deep vein thrombosis after knee arthroplasty in Asians remains low: a meta-analysis

BACKGROUND

While Western literature has mostly reported the incidence of deep vein thrombosis (DVT) and pulmonary embolism (PE) after TKA with chemoprophylaxis, the Asian literature still has mostly reported the incidence without chemoprophylaxis. This may reflect a low incidence of DVT and PE in Asian patients, although some recent studies suggest the incidence after TKA in Asian patients is increasing. Moreover, it is unclear whether the incidence of DVT and PE after TKA is similarly low among different Asian countries.

QUESTIONS/PURPOSES

We therefore determined the overall incidence of symptomatic PE and DVT without chemoprophylaxis after TKA in the Asian population, determined whether the incidence had a tendency to increase over time in Asia, and compared the incidence of symptomatic PE and DVT among Asian countries through a meta-analysis.

METHODS

We searched the PubMed, Embase, Cochrane Library, Web of Science, and Google Scholar websites for prospective studies published between 1996 and 2011. A total of 1947 patients from 18 studies were reviewed for meta-analysis.

RESULTS

The incidence of symptomatic PE was 0.01%. The incidences of overall DVT, proximal DVT, and symptomatic DVT were 40.4%, 5.8% and 1.9%, respectively. We found no difference in incidence of symptomatic PE among Asian countries and no trends in changes of the incidence over time.

CONCLUSIONS

The incidence of symptomatic PE and DVT after TKA without prophylaxis is low in Asian countries and has not changed over time, despite Westernizing lifestyles and an aging populace. Further investigation with large randomized studies is necessary to confirm our findings and identify risk factors predisposing to DVT.

[The new guidelines for deep venous thromboembolic disease prophylaxis in elective hip and knee replacement surgery. Are we nearer or further away from a consensus?]

Venous thromboembolism events (VTE) prophylaxis after elective hip or knee replacement surgery is a subject of controversy. Three sets of guidelines (NICE, ACCP and AAOS) on this topic have recently been updated. The guidelines have points in common: prophylaxis is necessary, it is recommended to combine mechanical and pharmacological prophylaxis in patients who have suffered a previous VTE, isolated mechanical measures and low molecular weight heparins are effective, the new oral anticoagulants and fondaparinux are effective drugs. There is some consensus in recommending regional anaesthesia, in advising against echography studies in asymptomatic patients, and in the promotion of early mobilisation of the patient. There is controversy over the most suitable pharmacological treatment and the time of starting, and the duration of this, as well as on vena cava filters, antiplatelet drugs, and VTE or bleeding risk factors.

Chinese orthopedic surgeons' practice regarding postoperative thromboembolic prophylaxis after major orthopedic surgery

OBJECTIVE

To assess Chinese surgeon practice of thromboprophylaxis following major orthopedic surgery.

METHODS

A questionnaire survey was conducted amongst Chinese orthopedic surgeons. A total of 293 surgeons were surveyed concerning five key aspects of thromboembolic prophylaxis after major orthopedic surgery at the proseminar of Chinese guidelines for prevention of venous thromboembolism (VTE) after major orthopedic surgery in January of 2009.

RESULTS

Totally, 208 surgeons (71.0%) responded, successfully completing the questionnaire. Of them, 57.6% respondents selected combined basic, mechanical, and pharmacologic methods for thromboprophylaxis; 51.0% respondents prefer starting prophylaxis 12-24 hours after surgery; 60.3% surgeons would use chemoprophylaxis for 7-10 days; 47.6% respondents prefer VTE prevention based on patients' special conditions and needs upon discharge."Safety" was the most repeated and emphasized factor during VTE prophylaxis.

CONCLUSIONS

Multimodal thromboprophylaxis is frequently used after major orthopedic surgery. Half surgeons prefer to start chemoprophylaxis 12-24 hours after surgery. Thromboprophylaxis regimen varies for discharged patients.

Relevance of immobility and importance of risk assessment management for medically ill patients

Recent or continued immobility is a significant risk factor for venous thromboembolism (VTE) in acutely ill medical patients. Patients may benefit from thromboprophylaxis; however, its optimal duration remains unclear. The Extended Clinical Prophylaxis in Acutely Ill Medical Patients (EXCLAIM) study was the first trial to systematically investigate how the degree of immobilization relates to the risk of developing VTE. EXCLAIM offers insights into the duration of VTE risk associated with reduced mobility and helps identify which patients would benefit most from extended-duration thromboprophylaxis. Further recent studies suggest that extended-duration thromboprophylaxis may be in order in certain high-risk patients to protect the patients from the risk of VTE events occurring, particularly in the posthospitalization period. Baseline d-dimer data and level of mobility could be included in risk assessment. Physicians are recommended to consider the use of extended-duration thromboprophylaxis based on individual risk assessment management (RAM) and balance of benefit and harm.

Performance measures for improving the prevention of venous thromboembolism: achievement in clinical practice

Venous thromboembolism (VTE) is a common complication during and after hospitalization for acute medical illness or surgery. Despite the existence of evidence-based guidelines for VTE prevention, real-world prescribing practices are frequently suboptimal. Specific performance measures relating to VTE prevention and treatment have been developed by US health care organizations to increase adherence with best-practice recommendations and ultimately reduce the number of preventable VTE events. Two measures developed by the Surgical Care Improvement Project have been endorsed by the National Quality Forum (NQF) and focus on VTE prevention. In addition, six measures have been developed recently by The Joint Commission in collaboration with the NQF; three measures relate to VTE prevention and three focus on treatment. To attain widespread achievement of these performance goals, it is essential to raise awareness of their existence and specifications. It is also imperative that hospitals develop and implement effective VTE protocols. The use of multiple, active strategies, such as computer decision support systems with regular audit and feedback, may be particularly valuable approaches to improve current practices within an integrated quality improvement program. During practical implementation of VTE protocols at Norton Healthcare (Kentucky's largest healthcare system), strong leadership, physician engagement, and caregiver accountability were identified as key factors influencing the process. As such, more hospitals may be able to increase adherence with guidelines, improve achievement of quality goals, and help to reduce the substantial burden associated with avoidable VTE.

Identification of patient venous thromboembolism risk across the continuum of care

Venous thromboembolism (VTE) complications are the leading cause of preventable in-hospital mortality and morbidity in the United States. Initiatives by the National Quality Forum, the Joint Commission, and the Surgical Care Improvement Project aim to improve the prevention of VTE and emphasize the need to recognize the risk of the condition in hospitalized patients. In clinical practice, individual risk assessment using a validated scoring system provides patients with the best care in the prevention of VTE. This is accomplished by a weighted scoring of risk factors, selection of the most appropriate prevention strategy for patients at risk, and regular risk review across the continuum of care. All hospitals should have a local, written, care pathway which assesses inpatient risk of VTE as early as possible upon admission and identifies members of the health care team responsible for applying risk assessment. Venous thromboembolism risk should be regularly reassessed for any changes in the level of risk, with extended out-of-hospital prophylaxis considered for patients with continued risk factors, such as prolonged immobility or illness, treated at home, or in a long-term care facility. Finally, a mandatory alert system requiring the clinician to address the issue of prophylaxis before any orders are carried out by the nursing staff is one way to protect all hospitalized patients.

Is there adequate provision of venous thromboembolism prophylaxis following hip arthroplasty? An audit and international survey

INTRODUCTION

The peak incidence of venous thrombo-embolism (VTE) occurs 3 weeks following hip arthroplasty surgery and current guidelines proposing VTE prophylaxis continuing for 4 weeks after surgery. This study first compares the duration of treatment and satisfaction between patients prescribed low molecular weight heparin (LMWH) and rivaroxaban, a new oral Factor Xa inhibitor, following elective hip arthroplasty; and second, surveys the duration of LMWH use in other units.

SUBJECTS AND METHODS

An international survey detailing the use of LMWH was performed. A prospective audit was performed of 100 hip replacements, with 50 prescribed 40 mg once daily of subcutaneous enoxaparin and subsequently 50 patients prescribed 10 mg once daily of oral rivaroxaban. The duration of treatment, patient satisfaction and complications for both cohorts was quantified and compared against published evidence-based guidelines.

RESULTS

The survey demonstrated that four out of 39 (10.2%) units that routinely prescribe LMWH do so for at least 4 weeks following surgery. The audit demonstrated that rivaroxaban afforded a superior mean duration of postoperative VTE prophylaxis (35 days vs 5.4 days; P < 0.05) and superior patient satisfaction. There was no difference in the incidence of bleeding, wound infection or thrombotic complications.

CONCLUSIONS

This study demonstrates that patients are exposed to an increased VTE risk following hip replacement surgery due to the inadequate prescription of LMWH. This is poor clinical practice, contrary to current evidence-based guidelines and has potential medicolegal implications. The prescription of rivaroxaban affords a superior patient compliance compared with subcutaneous LMWH, thus ensuring that patients receive VTE prophylaxis for the current recommend period of time.

Implementation of the NICE guidelines for venous thromboprophylaxis; a national survey of hip surgeons

The 2007 United Kingdom National Institute for Health and Clinical Excellence (NICE) thromboprophylaxis guidelines concerning hip arthroplasty remain contentious in spite of significant evidence. A survey among British Hip Society members was performed to investigate the impact of these guidelines. Information on thromboprophylactic measures before and after guideline publication was gathered for three categories; Total Hip Replacement (THR), hip fracture and high-risk patients (as defined by NICE). The response rate was 185/250 (74%). All responders used thromboprophylaxis, but only 44%, 22% and 7% indicated they were currently acting in accordance with guidance for THR, high risk and hip fracture groups respectively. Only 19%, 14% and 14% had changed their practice since publication of the guidance in THR, high risk and hip fracture groups respectively. The effects of national guidance in influencing thromboprophylactic protocols have therefore been limited. The reasons were not investigated in this survey.

[Prevention of venous thromboembolic disease in general surgery]

Postoperative venous thromboembolic disease (VTED) affects approximately one in four general surgery patients who do not receive preventive measures. In addition to the risk of pulmonary embolism, which is often fatal, patients with VTED may develop long-term complications such as post-thrombotic syndrome or chronic pulmonary hypertension. In addition, postoperative VTED is usually asymptomatic or produces clinical manifestations that are attributed to other processes and consequently this complication is often unnoticed by the surgeon who performed the procedure. Thus, the most effective strategy consists of effective prevention of VTED using the most appropriate prophylactic measures against the patient's thromboembolic risk. There is sufficient evidence that VTED can be prevented by pharmacological methods, especially heparin and its derivatives and with mechanical methods such as support tights or intermittent pneumatic compression of the lower extremities. To reduce the incidence of VTED as far as possible, strategies have been proposed that include a combination of drugs and mechanical methods, new antithrombotic drugs, or prolonging the duration of prophylaxis in patients at very high risk, such as those who have undergone surgery for cancer. Another important aspect is the optimal moment to initiate prophylaxis with anticoagulant drugs with the aim of achieving an adequate equilibrium between antithrombotic efficacy and the risk of hemorrhagic complications. The present article reviews the available evidence to attempt to optimize prevention of VTED in general surgery and in some special groups, such as laparoscopic surgery, short-stay surgery and obesity.

Prevention of venous thromboembolism: consensus, controversies, and challenges

The last 50 years have witnessed a multitude of publications evaluating the efficacy, safety and cost effectiveness of many different thromboprophylaxis interventions. There is widespread consensus that thromboprophylaxis safely reduces morbidity and mortality. More than 25 evidence-based guidelines, published since 1986, also recommend routine thromboprophylaxis in the majority of hospitalized patients. As a result, thromboprophylaxis is recognized as a key safety priority for hospitals. Some of the remaining areas of controversy that will be discussed in this paper include the role of individual risk assessments to determine thrombosis risk and prophylaxis, replacement of low-dose heparin by low-molecular-weight heparin (LMWH), the optimal duration of prophylaxis, the role of combined thromboprophylaxis modalities, the safety of anticoagulant prophylaxis with regional analgesia, the use of LMWHs in chronic renal insufficiency, and the emerging role of new oral anticoagulants as thromboprophylactic agents. Despite the overwhelming evidence supporting thromboprophylaxis, rates of thromboprophylaxis use remain far from optimal. Successful implementation strategies to bridge this knowledge:care gap are the most important current challenges in this area. These strategies must be multifaceted, utilizing local, systems-based approaches as well as legislation and incentives that reinforce best practices.

Decreased venous thromboembolism with injectable vs oral anticoagulation after discharge for major orthopedic surgery

The use of outpatient anticoagulation after major orthopedic surgery with oral or injectable anticoagulants is recommended by national guidelines. A retrospective analysis of medical and pharmacy claims data using the PharMetrics Patient-Centric Database Inc, Watertown, Mass, was conducted. After adjusting for covariates, patients receiving warfarin were approximately 30% more likely to experience a venous thromboembolism than those receiving an injectable anticoagulant (6.3% vs 4.8%; adjusted odds ratio, 1.3; 95% confidence interval, 1.1-1.5) by 30 days. The data at 90 days showed similar results. No significant differences in the incidence of major bleeding events between the cohorts were observed (incidence of major bleed <0.4%). These findings support the randomized controlled studies and expand the data to the real-world perspective. Clinicians should evaluate these data alongside the clinical trial data when selecting the safest and most effective prophylactic therapy for postdischarge anticoagulation.

Postdischarge oral versus injectable anticoagulation following major orthopedic surgery

BACKGROUND

Multiple clinical studies have shown postdischarge anticoagulation to be beneficial following major orthopedic surgery (MOS); however, outpatient prophylaxis is not widely practiced.

OBJECTIVE

To quantify, from a third-party payer perspective, real-world clinical and economic outcomes for patients receiving injectable or oral anticoagulation as prophylaxis for venous thromboembolism (VTE) following discharge after MOS.

METHODS

A retrospective database analysis was conducted using outpatient medical and pharmacy data from the PharMetrics Patient-Centric Database (January 1, 2002, to March 31, 2006). Patients greater than 18 years of age with 9 months of continuous eligibility who received an anticoagulant in the outpatient setting following MOS were eligible. Patients were stratified into 2 cohorts: injectable (dalteparin, enoxaparin, fondaparinux) and oral (warfarin), and were matched 1:1 on demographic and clinical characteristics.

RESULTS

A total of 12,724 patients were included (injectable, 6362; oral, 6362). At 90 days, patients receiving oral anticoagulation were 20% more likely to experience a VTE than were those receiving an injectable agent (7.4% vs 6.3%; p = 0.02, OR 1.18; 95% CI 1.03 to 1.36). No significant differences in bleeding were observed (<0.4%). The average adjusted total 6-month costs were significantly (p < 0.001) higher for the oral versus injectable cohort ($18,039 vs $16,429). Medical costs in the oral cohort offset the higher pharmacy costs in the injectable cohort.

CONCLUSIONS

This study demonstrates that the risk of VTE extends to the outpatient setting following MOS, even with postdischarge anticoagulation. Injectable agents used in the outpatient setting may result in fewer clinical VTEs without increasing the risk for major bleeding. These findings support the data from controlled clinical studies and expand the evidence to the real-world setting. Despite higher pharmacy acquisition costs for injectable anticoagulants, injectable agents may offer significant per patient savings to third party payers.

The safety and efficacy of extended thromboprophylaxis with fondaparinux after major orthopedic surgery of the lower limb with or without a neuraxial or deep peripheral nerve catheter: the EXPERT Study

BACKGROUND

The benefit-risk ratio of extended fondaparinux therapy has not been assessed in patients undergoing major lower limb joint arthroplasty. Few data on the concomitant use of fondaparinux and continuous neuraxial or deep peripheral nerve blockade are available. We performed a prospective intervention study in patients undergoing major orthopedic surgery primarily designed to assess the efficacy of fondaparinux when drug administration was withheld for 48 h to permit removal of a neuraxial or deep peripheral nerve catheter. The safety and efficacy of extended fondaparinux therapy for the prevention of venous thromboembolism were also evaluated.

METHODS

Patients received a daily subcutaneous injection of 2.5 mg fondaparinux for 3 to 5 wk postoperatively. In patients with a neuraxial or deep peripheral nerve catheter, the catheter was removed 36 h after the last fondaparinux dose. The next fondaparinux dose was administered 12 h after catheter removal. The primary end points were symptomatic venous thromboembolism and major bleeding up to 4-6 wk after surgery.

RESULTS

We recruited 5704 patients. A neuraxial or deep peripheral nerve catheter was inserted in 1553 (27%) patients and 78 (1.4%) patients, respectively. The rate of venous thromboembolism was 1.0% (54 of 5387). There was no difference between patients without (1.1%) or with (0.8%) a catheter (the upper limit of the 95% confidence interval of the odds ratio, 1.49, being below the predetermined noninferiority margin of 1.75). The incidence of major bleeding was 0.8% (42 of 5382). No neuraxial or perineural hematoma was reported.

CONCLUSIONS

Once-daily subcutaneous injection of 2.5 mg fondaparinux given for 3 to 5 wk was effective and safe for prevention of venous thromboembolism after major orthopedic surgery. Temporary discontinuation of fondaparinux for 48 h permitted safe removal of a neuraxial or deep peripheral nerve catheter without decreasing thromboprophylatic efficacy.

Epidemiology of venous thromboembolism after lower limb arthroplasty: the FOTO study

BACKGROUND

In view of recent substantial changes in the management of orthopedic surgery patients, a study was performed in order to update data on the epidemiology of venous thromboembolism (VTE) in patients undergoing lower limb arthroplasty according to contemporary practise.

METHODS

We performed a prospective observational study of a cohort of consecutive patients hospitalized for total hip or knee replacement in June 2003. The primary study outcome was the incidence of symptomatic VTE at 3 months. All events were adjudicated by an independent critical event committee.

RESULTS

Data from 1080 patients (mean age 68.0 years) were available; 63.2% were undergoing total hip replacement and 36.8% total knee replacement. Pharmacological thromboprophylaxis was administered for a mean time of 36 days. Injectable antithrombotics were used in more than 99% of patients, irrespective of the type of surgery. The incidence of the primary study outcome was 1.8% (20 events; 95% CI: 1.0-2.6%). The incidences were 1.3% and 2.8% in hip and knee surgery patients, respectively. There were two pulmonary embolisms, both in knee surgery patients; neither was fatal. Thirty-five per cent of VTEs occurred after hospital discharge. An age of at least 75 years and the absence of ambulation before hospital discharge were the only significant (P < 0.05) predictors of VTE. The rate of clinically significant bleeding was 1.0% and the rate of death was 0.9%.

CONCLUSIONS

The incidence of symptomatic VTE after lower limb arthroplasty is low, even if there is still a need to improve thromboprophylaxis, notably in patients undergoing knee arthroplasty.

Insufficient duration of venous thromboembolism prophylaxis after total hip or knee replacement when compared with the time course of thromboembolic events: findings from the Global Orthopaedic Registry

Patients who have undergone total hip or knee replacement (THR and TKR, respectively) are at high risk of venous thromboembolism. We aimed to determine the time courses of both the incidence of venous thromboembolism and effective prophylaxis. Patients with elective primary THR and TKR were enrolled in the multi-national Global Orthopaedic Registry. Data on the incidence of venous thromboembolism and prophylaxis were collected from 6639 THR and 8326 TKR patients. The cumulative incidence of venous thromboembolism within three months of surgery was 1.7% in the THR and 2.3% in the TKR patients. The mean times to venous thromboembolism were 21.5 days (sd 22.5) for THR, and 9.7 days (sd 14.1) for TKR. It occurred after the median time to discharge in 75% of the THR and 57% of the TKA patients who developed venous thromboembolism. Of those who received recommended forms of prophylaxis, approximately one-quarter (26% of THR and 27% of TKR patients) were not receiving it seven days after surgery, the minimum duration recommended at the time of the study. The risk of venous thromboembolism extends beyond the usual period of hospitalisation, while the duration of prophylaxis is often shorter than this. Practices should be re-assessed to ensure that patients receive appropriate durations of prophylaxis.

Fondaparinux combined with intermittent pneumatic compression vs. intermittent pneumatic compression alone for prevention of venous thromboembolism after abdominal surgery: a randomized, double-blind comparison

BACKGROUND

The benefit of combined mechanical and pharmacologic methods for venous thromboembolism prevention after abdominal surgery has not been clearly established.

OBJECTIVES

To compare the efficacy and safety of fondaparinux in conjunction with intermittent pneumatic compression vs. intermittent pneumatic compression alone in this context.

PATIENTS AND METHODS

This was a randomized, double-blind, placebo-controlled superiority trial. Patients aged at least 40 years undergoing abdominal surgery were randomized to receive either fondaparinux 2.5 mg or placebo s.c. for 5-9 days, starting 6-8 h postoperatively. All patients received intermittent pneumatic compression. The primary efficacy outcome was venous thromboembolism up to day 10. The main safety outcomes were major bleeding and all-cause mortality. Follow-up lasted 32 days.

RESULTS

Of the 1309 patients randomized, 842 (64.3%) were evaluable for efficacy. The venous thromboembolism rate was 1.7% (7/424) in the fondaparinux-treated patients and 5.3% (22/418) in the placebo-treated patients (odds ratio reduction 69.8%; 95% confidence interval 27.9-87.3; P = 0.004). Fondaparinux significantly reduced the proximal deep vein thrombosis rate from 1.7% (7/417) to 0.2% (1/424; P = 0.037). Major bleeds occurred in 1.6% (10/635) and 0.2% (1/650) of fondaparinux-treated and placebo-treated patients, respectively (P = 0.006), none being fatal or involving a critical organ. By day 32, eight patients (1.3%) receiving fondaparinux and five (0.8%) receiving placebo had died.

CONCLUSIONS

In patients undergoing abdominal surgery and receiving intermittent pneumatic compression, fondaparinux 2.5 mg reduced the venous thromboembolism rate by 69.8% as compared to pneumatic compression alone, with a low bleeding risk as compared to placebo.

Mechanical and pharmacological methods to prevent venous thromboembolism

Today, it is possible to define certain risk groups for the development of venous thromboembolism, most studies having been conducted on post-operative venous thromboembolism. Nonetheless, the risk classification is rather inexact, resulting in many patients receiving prophylaxis who would not have gone on to develop the complication. However, the current prophylactic methods are safe and can therefore also be used in the post-operative situation. The dominating pharmacological substances are unfractionated heparin, low-molecular-weight heparins and the pentasaccharide fondaparinux. In some situations (such as elective hip surgery and likely hip fracture surgery, and in many cases where malignant diseases in the abdomen/pelvis have been operated upon), extended prophylaxis for 1 month should be considered.

Management patterns of thrombosis prophylaxis and related costs in hip and knee replacement in Germany

The objective of the study was to depict treatment strategies, health care utilisation and cost evaluation of hip and knee replacement surgery in Germany, with a particular emphasis on thrombosis prophylaxis (TP) for the prevention of deep vein thrombosis (DVT). In this multi-centre prospective cohort study, medical record data (socio-demographics, risk factors for thrombosis, thrombosis prophylaxis, course of hospital stay) were collected for patients undergoing either total hip replacement (THR) or total knee replacement (TKR). One and three months post-operatively, post-operative outcomes and health care resource use were documented by patient and physician questionnaires. A total of 309 patients participated in the study (59% female, mean age 66 [SD 10] years). Parenteral anticoagulation was administered for a mean of 38 (SD 16) days. 27 (9%) patients received subsequent oral anticoagulation for a mean of 38 (SD 21) additional days. Symptomatic DVT was reported by four (1.3%) patients. Mean overall direct costs associated with surgery from baseline to 3 months were EUR 11 264 (median 11 564, SD 2 481). Hospital and rehabilitation accounted for 97% of direct costs; costs for medications, physical therapy, physician office visits, out-of-pocket expenses, as well as complication costs accounted for an additional 3% of direct costs. Within these direct costs, a mean of EUR 348 (SD 361) was related to thrombosis prophylaxis, accounting for 3% of direct costs. Mean overall cost was EUR 11 926 (SD 2 481), including 6% indirect costs of productivity loss. Extended thrombosis prophylaxis was observed in the usual care setting of the study and associated with low incidence of symptomatic DVT. Thrombosis prophylaxis is — within the considerable economic burden of joint replacement surgery — a relatively small cost component.

Prolonged prophylaxis with dalteparin to prevent late thromboembolic complications in patients undergoing major abdominal surgery: a multicenter randomized open-label study

BACKGROUND

Patients undergoing major abdominal surgery carry a high risk of venous thromboembolism (VTE), but the optimal duration of postoperative thromboprophylaxis is unknown.

OBJECTIVES

To evaluate the efficacy and safety of thromboprophylaxis with the low molecular weight heparin (dalteparin), administered for 28 days after major abdominal surgery compared to 7 days' treatment.

PATIENTS/METHODS

A multicenter, prospective, assessor-blinded, open-label, randomized trial was performed in order to evaluate prolonged thromboprophylaxis after major abdominal surgery. In total, 590 patients were recruited, of whom 427 were randomized and received at least 1 day of study medication, and 343 reached an evaluable endpoint. The primary efficacy endpoint was objectively verified VTE occurring between 7 and 28 days after surgery. All patients underwent bilateral venography at day 28.

RESULTS

The cumulative incidence of VTE was reduced from 16.3% with short-term thromboprophylaxis (29/178 patients) to 7.3% after prolonged thromboprophylaxis (12/165) (relative risk reduction 55%; 95% confidence interval 15-76; P=0.012). The number that needed to be treated to prevent one case of VTE was 12 (95% confidence interval 7-44). Bleeding events were not increased with prolonged compared with short-term thromboprophylaxis.

CONCLUSIONS

Four-week administration of dalteparin, 5000 IU once daily, after major abdominal surgery significantly reduces the rate of VTE, without increasing the risk of bleeding, compared with 1 week of thromboprophylaxis.

Evidence for the prevention of venous thromboembolism

Patients undergoing major orthopaedic surgery are at high risk of developing venous thromboembolism (VTE). VTE is preventable and venous prophylaxis consensus groups recommend that each patient is assessed for risk of VTE and then stratified into one of the three categories of risk. Rick stratification enables the choice of the most appropriate preventative interventions. This article examines a decision making framework for VTE prevention with particular focus on a validated risk assessment model (RAM) to facilitate risk stratification. The relevant literature is also scrutinised in terms of the best venous antithrombotic strategies, for patients undergoing major orthopaedic surgery, according to scientific evidence.

Prevention of postoperative venous thromboembolism. Risk assessment and methods of prophylaxis

PURPOSE

To describe risk assessment models that have been developed to stratify patients into different risk levels of postoperative venous thromboembolism (VTE) and then to review the different methods of prophylaxis and to outline the evidence supporting their effectiveness and safety.

SOURCE

Our review of the literature is focused on consensus documents, recent large randomized trials and meta-analyses.

PRINCIPAL FINDINGS

The risk of VTE is determined by the type of surgery and underlying patient factors. Risk assessment models are useful in stratifying patients into different VTE risk levels. However, multiple risk factors are often present in the same patient and in practice the evaluation of their relative contribution to the overall risk remains difficult. A variety of prophylactic strategies including physical and pharmacological methods have been shown to be effective in different patient groups. Patients with a moderate or high risk of VTE should receive prophylaxis consisting of an antithrombotic agent, unless contraindicated, used alone or in combination with a mechanical method. Recommendations concerning which prophylaxis to use and how intensive it should be are based mainly on data from trials using surrogate endpoints, and do not translate easily into practical decisions aiming to reduce the incidence of symptomatic events.

CONCLUSION

Although risk assessment models and recommendations provided by consensus documents are of practical assistance, a decision concerning any patient is best made by combining recommendations of the literature with clinical judgment, including individual patient risk factors for thrombosis and bleeding.

Pharmacological methods of thromboprophylaxis

The burden of venous thromboembolism (VTE) in hospitalized patients is significant and often underestimated. In this article the rationale for thromboprophylaxis is reviewed and rates of VTE in different patient populations considered. The options for pharmacological methods of prophylaxis are outlined and the evidence for their use in specific patient groups is reviewed. Thromboprophylaxis is effective but currently underused. Strategies are being developed to remedy this situation including the development of national guidelines and intervention by the Department of Health.

Assessment of a self-administration protocol for extended subcutaneous thromboprophylaxis in lower limb arthroplasty

The risk of venous thromboembolism in patients following arthroplasty may be reduced by continuing chemical thromboprophylaxis for up to 35 days post-operatively. This prospective cohort study investigated the compliance of 40 consecutive consenting patients undergoing lower limb arthroplasty with self-administration of a recommended subcutaneous chemotherapeutic agent for six weeks after surgery. Compliance was assessed by examination of the patient for signs of injection, number of syringes used, and a self-report diary at the end of the six-week period. A total of 40 patients, 15 men and 25 women, were recruited. One woman was excluded because immediate post-operative complications prevented her participation. Self-administration was considered feasible in 87% of patients (95% confidence interval (CI) 76 to 98) at the time of discharge. Among this group of 34 patients, 29 (85%) were compliant (95% CI 73 to 97). Patients can learn to self-administer subcutaneous injections of thromboprophylaxis, and compliance with extended prophylaxis to six weeks is good.

Deep-vein thrombosis rates after major orthopedic surgery in Asia. An epidemiological study based on postoperative screening with centrally adjudicated bilateral venography

BACKGROUND

The incidence of postsurgical venous thromboembolism is thought to be low in Asian ethnic populations.

OBJECTIVE

We studied the incidence of deep-vein thrombosis (DVT) in Asian patients undergoing major orthopedic surgery of the lower limbs.

PATIENTS/METHODS

We performed a prospective epidemiological study in 19 centers across Asia (China, Indonesia, South Korea, Malaysia, Philippines, Taiwan, and Thailand) in patients undergoing elective total hip replacement (THR), total knee replacement (TKR) or hip fracture surgery (HFS) without pharmacological thromboprophylaxis. The primary endpoint was the rate of DVT of the lower limbs documented objectively with bilateral ascending venography performed 6-10 days after surgery using a standardized technique and evaluated by a central adjudication committee unaware of local interpretation.

RESULTS

Overall, of 837 Asian patients screened for this survey, 407 (48.6%, aged 20-99 years) undergoing THR (n = 175), TKR (n = 136) or HFS (n = 96) were recruited in 19 centers. DVT was diagnosed in 121 of 295 evaluable patients [41.0%, (95% confidence interval (CI): 35.4-46.7)]. Proximal DVT was found in 30 patients [10.2% (7.0-14.2)]. Total DVT and proximal DVT rates were highest in TKR patients (58.1% and 17.1%, respectively), followed by HFS patients (42.0% and 7.2%, respectively), then THR patients (25.6% and 5.8%, respectively). DVT was more frequent in female patients aged at least 65 years. Pulmonary embolism was clinically suspected in 10 of 407 patients (2.5%) and objectively confirmed in two (0.5%).

CONCLUSIONS

The rate of venographic thrombosis in the absence of thromboprophylaxis after major joint surgery in Asian patients is similar to that previously reported in patients in Western countries.

Clinical efficacy and safety of fondaparinux in the prevention and treatment of venous and arterial thrombosis

Fondaparinux (Arixtra®) is a synthetic, selective Factor Xa inhibitor. Its pharmacokinetic profile allows once-daily subcutaneous administration of the drug without any laboratory monitoring. The benefit-to-risk ratio of fondaparinux in the prevention of venous thromboembolism has been extensively studied in both surgical and acutely ill medical patients at risk of thrombosis. Its efficacy and safety have also been investigated in the initial treatment of symptomatic deep-vein thrombosis and pulmonary embolism. Finally, a number of Phase II trials investigated the safety and efficacy of fondaparinux in patients with acute coronary syndromes, and a large Phase III program is ongoing in this setting. This review focuses on the use of fondaparinux in the prevention and treatment of thromboembolic disorders.

Randomized clinical trial of postoperative fondaparinux versus perioperative dalteparin for prevention of venous thromboembolism in high-risk abdominal surgery

BACKGROUND

The aim of this study was to assess whether the synthetic factor Xa inhibitor fondaparinux reduced the risk of venous thromboembolism more efficiently than the low molecular weight heparin dalteparin in patients undergoing major abdominal surgery.

METHODS

In a double-blind double-dummy randomized study, patients scheduled for major abdominal surgery under general anaesthesia received once-daily subcutaneous injections of fondaparinux 2.5 mg or dalteparin 5000 units for 5-9 days. Fondaparinux was started 6 h after surgery. The first two doses of dalteparin, 2500 units each, were given 2 h before surgery and 12 h after the preoperative administration. The primary outcome measure was a composite of deep vein thrombosis detected by bilateral venography and symptomatic, confirmed deep vein thrombosis or pulmonary embolism up until day 10. The main safety outcome measure was major bleeding during treatment.

RESULTS

Among 2048 patients evaluable for efficacy, the rate of venous thromboembolism was 4.6 per cent (47 of 1027) with fondaparinux compared with 6.1 per cent (62 of 1021) with dalteparin, a relative risk reduction of 24.6 (95 per cent confidence interval -9.0 to 47.9) per cent (P = 0.144), which met the predetermined criterion for non-inferiority of fondaparinux. Major bleeding was observed in 49 (3.4 per cent) of 1433 patients given fondaparinux and 34 (2.4 per cent) of 1425 given dalteparin (P = 0.122).

CONCLUSION

Postoperative fondaparinux was at least as effective as perioperative dalteparin in patients undergoing high-risk abdominal surgery.

The true treatment benefit is unpredictable in clinical trials using surrogate outcome measured with diagnostic tests

BACKGROUND AND OBJECTIVES

Clinical trials increasingly use results of diagnostic tests as surrogate outcomes. Our objective was to answer the following questions: (1) is the parameter measured by the reference standard a valid surrogate? (2) How does the tests accuracy influence the estimate of the treatment benefit on surrogate? (3) Is it possible to correct the measured treatment effect given by results of inaccurate tests?

METHODS AND SETTING

We reviewed the literature on asymptomatic deep venous thrombosis (DVT), detected by the reference standard and other imaging techniques, as surrogate for venous thromboembolism. The influence of test inaccuracy on the measurement of treatment benefit was calculated as a function of the patient baseline risk, the treatment effect model, and test performances.

RESULTS

We show that: (1) asymptomatic DVT is correlated with clinical outcomes but is yet to be established as a surrogate; (2) inaccurate diagnostic test underestimates the treatment effect on surrogate; (3) the prevalence of the disease, the treatment effect model, and the accuracy of the test and the reference standard used to evaluate it need to be known to correct this underestimation.

CONCLUSION

Even when the surrogate end point is valid, without a reliable study of the diagnostic test we cannot quantify the true treatment effect.

New anticoagulant therapy

The development of new anticoagulants is expanding the list of drugs that can be used to prevent and treat venous and arterial thrombosis. New parenteral anticoagulants have been developed to overcome the limitations of heparin and low-molecular-weight heparin, whereas novel orally active anticoagulants have been designed to provide more streamlined therapy than vitamin K antagonists. This review identifies the molecular targets of new anticoagulants, describes the results of clinical trials, and provides clinical perspective on the opportunities for new anticoagulants.