Efficacy and safety of prolonged thromboprophylaxis with a low molecular weight heparin (dalteparin) after total hip arthroplasty--the Danish Prolonged Prophylaxis (DaPP) Study

Venous Thromboembolism Prophylaxis in Major Orthopedic Surgeries and Factor XIa Inhibitors

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

Double Blind Pilot Randomized Trial Comparing Extended Anticoagulation to Placebo Following Major Lung Resection for Cancer

Venous thromboembolism (VTE), which comprises pulmonary embolus (PE) and deep vein thrombosis (DVT), is a significant cause of postoperative morbidity and mortality. This pilot randomized control trial (RCT) evaluated the feasibility of a full-scale RCT investigating extended thromboprophylaxis in patients undergoing oncological lung resections. Patients undergoing oncological lung resections in 2 tertiary centers received in-hospital, thromboprophylaxis and were randomized to receive post-discharge low-molecular-weight heparin (LMWH) or placebo injections once-daily for 30 days. At 30 days postoperatively, all patients underwent chest computed tomography with PE protocol and bilateral leg venous ultrasound. Primary outcomes included feasibility and safety; VTE incidence and 90-day survival were secondary outcomes. Between December 2015 and June 2018, 619 patients were screened, of whom 62.7% (165/263) of eligible patients consented to participate, and 133 (81%) were randomized. One-hundred and 3 patients, (77.4%), completed the 90-day study follow-up. Reasons for non-participation pre-randomization included patient discomfort and LMWH/placebo administration challenges. Post-randomization withdrawals were due to patient preference, surgeon preference and minor adverse events. Six asymptomatic VTE events (5 PE and 1 DVT) were detected within 30 days (3 in each group), for an overall incidence of 7%. There were 3 minor and no major adverse events. This study is the first to demonstrate the feasibility and safety of a full-scale extended thromboprophylaxis RCT in thoracic surgical oncology. Our results demonstrate that, while recruitment and retention rates were modest, the study design is feasible and with minimal adverse events and no intervention-related mortality.

Venous Thromboembolism following Microsurgical Breast Reconstruction: A Longitudinal Analysis of 12,778 Patients

BACKGROUND

Venous thromboembolism is a dreaded complication following microsurgical breast reconstruction. Although the high-risk nature of the procedure is well known, a thorough analysis of modifiable risk factors has not been performed. The purpose of this study was to analyze the association of such factors with the postoperative occurrence of venous thromboembolism longitudinally.

METHODS

Using the Truven MarketScan Database, a retrospective cohort study of women who underwent microsurgical breast reconstruction from 2007 to 2015 and who developed postoperative venous thromboembolism within 90 days of reconstruction was performed. Predictor variables included age, timing of reconstruction, body mass index, history of radiation therapy, history of venous thromboembolism, Elixhauser Comorbidity Index, and length of stay. Univariate analyses were performed, in addition to logistic and zero-inflated Poisson regressions, to evaluate predictors of venous thromboembolism and changes in venous thromboembolism over the study period, respectively.

RESULTS

Twelve thousand seven hundred seventy-eight women were identified, of which 167 (1.3 percent) developed venous thromboembolism. The majority of venous thromboembolisms (67.1 percent) occurred following discharge, with no significant change from 2007 to 2015. Significant predictors of venous thromboembolism included Elixhauser score (p < 0.01), history of venous thromboembolism (p < 0.03), and length of stay (p < 0.001). Compared to patients who developed a venous thromboembolism during the inpatient stay, patients who developed a postdischarge venous thromboembolism had a lower mean Elixhauser score (p < 0.001).

CONCLUSIONS

Postoperative venous thromboembolism continues to be an inadequately addressed problem, as evidenced by a stable incidence over the study period. Identification of modifiable risk factors, such as length of stay, provides potential avenues for intervention. As the majority of venous thromboembolisms occur following discharge, future studies are warranted to investigate the role for an intervention in this period.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, III.

Mortality risk associated with venous thromboembolism: a systematic review and Bayesian meta-analysis

BACKGROUND

Venous thromboembolism is associated with increased mortality risk in some populations, but how frequently it is a direct cause of death is unclear. We used data from venous thromboembolism prevention trials to evaluate the causal effect of venous thromboembolism reduction on mortality.

METHODS

We did a systematic review and meta-analysis of randomised controlled trials (RCTs) evaluating venous thromboembolism prevention. We searched MEDLINE, Embase, PubMed, and Web of Science starting from Jan 1, 1993, to March 19, 2018. We included studies of patients who were at elevated risk of venous thromboembolism and were randomly assigned to either anticoagulant or antiplatelet therapy versus placebo or no treatment. We excluded studies with an active control agent (which might mitigate the lethality of venous thromboembolism) and those for which mortality data were unavailable. We modelled heterogeneity in a Bayesian framework, taking overall mortality as a primary endpoint, and pulmonary embolism, fatal pulmonary embolism, and major bleeding as secondary endpoints. We focused our analyses on studies reporting statistically significant effects of prevention on venous thromboembolism endpoints. We report treatment effects as median risk ratios (RRs), wherein a null effect equals 1, with 95% credible intervals (CrIs). This meta-analysis was registered with PROSPERO, CRD42018089697.

FINDINGS

From 4229 studies screened, we identified 86 eligible RCTs; 52, with data from over 70 000 patients, were positive, with significantly increased venous thromboembolism risk in patients in control groups versus treatment groups (RR 2·74, 95% CrI 2·32-3·31, p<0·0001). The meta-analysis established that the causal effect of venous thromboembolism prevention on mortality was null (control group mortality was 3391 [9·8%] of 34 537 patients; treatment group mortality was 3498 [9·8%] of 35 795 patients [RR 1·01, 95% CrI 0·97-1·06; p=0·58]) with low heterogeneity (τ 0·02, 95% CrI 0·00-0·07, p=0·89). Patients in control groups had more pulmonary embolism (RR 2·22, 95% CrI 1·78-2·89, p<0·0001) and fatal pulmonary embolism (1·58, 1·14-2·19, p=0·01), but less major bleeding (0·60, 0·47-0·75, p<0·0001) than those in treatment groups. A meta-analysis with the additional 34 negative studies yielded similar results for all endpoints except fatal pulmonary embolism, where evidence of an effect was weaker (1·42, 1·05-1·91, p=0·02).

INTERPRETATION

The perception that venous thromboembolism is a common cause of mortality should be revised considering the null effect of venous thromboembolism prevention on mortality. Our findings call into question the use of composite endpoints in venous thromboembolism-prevention trials and provide rationale for de-escalation trials.

FUNDING

None.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Venous Thromboembolism Prophylaxis Strategies for People Undergoing Elective Total Hip Replacement: A Systematic Review and Network Meta-Analysis

OBJECTIVES

To assess the efficacy and safety of venous thromboembolism prophylaxis in people undergoing elective total hip replacement.

METHODS

Systematic review and Bayesian network meta-analyses of randomized controlled trials were conducted for 3 outcomes: deep vein thrombosis (DVT), pulmonary embolism (PE), and major bleeding (MB). MEDLINE, EMBASE, and Cochrane Library (CENTRAL) databases were searched. Study quality was assessed using the Cochrane risk-of-bias checklist. Fixed- and random-effects models were fitted and compared. The median relative risk (RR) and odds ratio (OR) compared with no prophylaxis, with their 95% credible intervals (CrIs), rank, and probability of being the best, were calculated.

RESULTS

Forty-two (n = 24 374, 26 interventions), 30 (n = 28 842, 23 interventions), and 24 (n = 31 792, 15 interventions) randomized controlled trials were included in the DVT, PE, and MB networks, respectively. Rivaroxaban had the highest probability of being the most effective intervention for DVT (RR 0.06 [95% CrI 0.01-0.29]). Strategy of low-molecular-weight heparin followed by aspirin had the highest probability of reducing the risk of PE and MB (RR 0.0011 [95% CrI 0.00-0.096] and OR 0.37 [95% CrI 0.00-26.96], respectively). The ranking of efficacy estimates across the 3 networks, particularly PE and MB, had very wide CrIs, indicating high degree of uncertainty.

CONCLUSIONS

A strategy of low-molecular-weight heparin given for 10 days followed by aspirin for 28 days had the best benefit-risk balance, with the highest probability of being the best on the basis of the results of the PE and MB network meta-analyses. Nevertheless, there is considerable uncertainty around the median ranks of the interventions.

A prospective randomized comparative study to determine appropriate edoxaban administration period, to prevent deep vein thromboembolism in patients with total knee arthroplasty

BACKGROUND

This study aimed to determine the appropriate administration duration of edoxaban 15 mg (a factor Xa inhibitor) for the prevention of deep vein thrombosis (DVT) after total knee arthroplasty (TKA).

METHODS

Our study comprised 202 patients who underwent TKA (excluding bilateral TKA) at our institution between 2014 and 2015. The subjects received edoxaban 15 mg daily for 1 (n = 93) or 2 (n = 109) weeks; group assignment was random. B-mode ultrasonography was performed 7 and 14 days post-TKA for the detection of DVT. We compared the incidence of DVT between the groups and examined for side effects.

RESULTS

The demographic data of the patients in the 1- and 2-week administration groups were similar at baseline. DVT incidence did not differ significantly between the groups at 1 week post-TKA. However, it was significantly lower in the 2-week administration group (n = 0) than in the 1-week administration group (n = 7; p = 0.004) at 2 weeks post-DVT. Neither group exhibited symptomatic DVT. A total of six patients withdrew during the study period because of hepatic dysfunction.

CONCLUSIONS

Our results show that the administration of edoxaban 15 mg is more effective in preventing DVT after TKA when administered for 2 weeks than for 1 week.

Assessment of 30-day mortality and complication rates associated with extended deep vein thrombosis prophylaxis following hip fracture surgery

BACKGROUND

DVT is a common complication following lower extremity surgery, occurring in up to 60% of patients undergoing hip fracture surgery without postoperative anticoagulation. The risk of fatal PE continues well-beyond two weeks postoperatively, thus extended DVT prophylaxis beyond 14 days may be warranted. This investigation sought to examine the association between prescription of extended DVT prophylaxis and 30-day postoperative complications following hip fracture surgery.

METHODS

This study utilized the ACS NSQIP Hip Fracture Procedure Targeted dataset, a newly available set of patient variables for 2016. The outcome measures were death, occurrence of any postoperative complication, complication subtype, readmission or reoperation within 30-days postoperatively, and length of stay. The primary independent variable was medical DVT prophylaxis continued 28-days postoperatively ("extended DVT prophylaxis"). The control group contains both patients receiving no prophylaxis and those receiving short-duration prophylaxis. Multivariate stepwise logistic regression was employed to control for potential demographic, comorbidity, and procedural/medical confounding factors.

RESULTS

In total, 7533 surgically treated hip fracture patients treated in 2016 were analyzed. Overall, 57.8% of patients (n = 4354) were prescribed extended DVT prophylaxis. On bivariate analysis, prescription of extended DVT prophylaxis was associated with significantly lower incidence of death (7.7% without vs. 2.7% with, p < 0.0001) and stroke/CVA (1.4% vs. 0.6%, p = 0.0016). In multivariate analysis, prescription of extended DVT prophylaxis was significantly associated with lower odds of death (OR 0.33, p < 0.0001), stroke/CVA (OR 0.44, p = 0.0010), and acute kidney injury (AKI) (OR 0.31, p = 0.0010).

CONCLUSIONS

This retrospective cohort study of the 2016 ACS NSQIP found that hip fracture surgery patients prescribed ≥28 days of postoperative DVT prophylaxis exhibited 67% lower odds of death and significantly lower rates of AKI and stroke/CVA as compared to those prescribed short-duration prophylaxis. Given the retrospective and uncontrolled nature of this analysis, these results should be interpreted with caution, and additional prospective randomized controlled trials examining the association between extended DVT prophylaxis and postoperative outcomes are warranted. If these observations accurately reflect real-world experience, these data suggest that ≥28 days of DVT prophylaxis following hip fracture surgery should be strongly considered for patients without explicit contraindications.

European perspectives in Thoracic Surgery, the ESTS venous thromboembolism (VTE) working group

Venous thromboembolism (VTE), composed of deep vein thrombosis (DVT) and PE is a well-recognized cause for significant perioperative morbidity and mortality. While in orthopedic surgery and general oncology surgery there are well established guidelines regarding VTE prophylaxis, based on carefully conducted high level studies, in thoracic surgery the level of evidence and overall knowledge in the field is still lacking, The European Society of Thoracic Surgeons have established an international working group in 2016, whose task was the define contemporary best practice, coordinate research efforts and eventually define best practice guidelines. This collaboration has matured into a multi-organizational effort, with participation of the American Association for Thoracic Surgery, the International Society on Thrombosis and Haemostasis and Chinese and Japanese thoracic societies. Two major projects (International practice survey and an expert group Delphi process re best practice and VTE risk factors) have been completed so far. For 2018, the working group goals will be to establish VTE prophylaxis guidance in Thoracic Surgery.

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-molecular-weight heparins for the prevention of recurrent venous thromboembolism in patients with cancer: A systematic literature review of efficacy and cost-effectiveness

Background

Patients with cancer have an elevated risk of venous thromboembolism. Importantly, patients with cancer, who have metastatic disease, renal insufficiency, or are receiving anticancer therapy, have an even higher risk of a recurrent event. Similarly, the risk of recurrent venous thromboembolism is higher than the risk of an initial event. To reduce the risk, extended duration of prophylaxis for up to six months with low-molecular-weight heparins such as dalteparin, enoxaparin, nadroparin, and tinzaparin is recommended by international guidelines. In this paper, the clinical and economic literature is reviewed to provide evidenced based recommendations based on clinical benefit and economic value.

Methods

A systematic review of major databases was conducted from January 1996 to October 2016 for randomized controlled trials evaluating the four distinct low-molecular-weight heparins against a vitamin K antagonists control group for the prevention of recurrent venous thromboembolism in patients with active cancer. This was then followed by the application of the National Institute of Health and Clinical Excellence guidance to assess the quality of all trials that met the inclusion criteria. Finally, the cost-effectiveness literature supporting the value proposition of each product was reviewed.

Results

Six randomized trials met the inclusion criteria. There were one, two, and three trials that compared dalteparin, tinzaparin, and enoxaparin to a vitamin K antagonists control group. However, there were no trials for nadroparin in the setting of secondary venous thromboembolism prevention. In addition, only the dalteparin and one of the tinzaparin trials were of high quality and adequately powered. Of the two studies, only the dalteparin trial reported a statistically significant benefit in terms of venous thromboembolism absolute risk reduction when compared to a vitamin K antagonists control group (HR = 0.48; p = 0.002). In addition, there was robust pharmacoeconomic data from Canada, the Netherlands, France, and Austria supporting the cost-effectiveness of dalteparin for this indication. There were no such studies for any of the other agents.

Conclusions

The totality of high-quality clinical and cost-effectiveness data supports the use of dalteparin over other low-molecular-weight heparins for preventing recurrent venous thromboembolism in patients with cancer.

Pulmonary Embolism Rates Following Total Hip Arthroplasty With Prophylactic Anticoagulation: Some Pulmonary Emboli Cannot Be Avoided

BACKGROUND

A symptomatic pulmonary embolism (PE) after total joint arthroplasty has been described as a "never event." Despite potent anticoagulants and improvements in patient care, PE continues to occur following total hip arthroplasty (THA). This study evaluates symptomatic PE rates over time in THA patients enrolled in multicenter randomized clinical trials (RCTs) assessing the efficacy of venous thromboembolism prophylaxis regimens.

METHODS

The MEDLINE and Cochrane Central Register of Controlled Trials were searched to identify clinical trials assessing prophylactic anticoagulation in patients undergoing THA between January 1995 and December 2015. Inclusion criteria consisted of RCTs evaluating prophylactic anticoagulation in patients undergoing THA. A random effect model was used to combine PE rates across studies.

RESULTS

A total of 21 studies (34,764 patients) were included. Patients were administered low molecular weight heparin (13,590 patients), oral factor Xa inhibitors (6609 patients), oral direct thrombin inhibitors (5965 patients), indirect factors Xa/IIa inhibitors (3444 patients), aspirin (2427 patients), and warfarin (489 patients). Mobile compression was used in 199 patients, and placebo was used in 2041 patients. Across all included studies, the estimated PE rate was 0.21% (95% confidence interval: 0.13%, 0.32%). Between 1997 and 2013, the proportion of PEs did not change in regression analysis.

CONCLUSION

Although the PE rate was low, it was consistent throughout the 17 years spanning these RCTs, which excluded patients with significant morbidity. These results suggest that even healthy THA patients receiving aggressive anticoagulation still have a risk for PE, and the "never event" designation requires reassessment.

Thromboprophylaxis after Knee Arthroscopy and Lower-Leg Casting

BACKGROUND

The use of thromboprophylaxis to prevent clinically apparent venous thromboembolism after knee arthroscopy or casting of the lower leg is disputed. We compared the incidence of symptomatic venous thromboembolism after these procedures between patients who received anticoagulant therapy and those who received no anticoagulant therapy.

METHODS

We conducted two parallel, pragmatic, multicenter, randomized, controlled, open-label trials with blinded outcome evaluation: the POT-KAST trial, which included patients undergoing knee arthroscopy, and the POT-CAST trial, which included patients treated with casting of the lower leg. Patients were assigned to receive either a prophylactic dose of low-molecular-weight heparin (for the 8 days after arthroscopy in the POT-KAST trial or during the full period of immobilization due to casting in the POT-CAST trial) or no anticoagulant therapy. The primary outcomes were the cumulative incidences of symptomatic venous thromboembolism and major bleeding within 3 months after the procedure.

RESULTS

In the POT-KAST trial, 1543 patients underwent randomization, of whom 1451 were included in the intention-to-treat population. Venous thromboembolism occurred in 5 of the 731 patients (0.7%) in the treatment group and in 3 of the 720 patients (0.4%) in the control group (relative risk, 1.6; 95% confidence interval [CI], 0.4 to 6.8; absolute difference in risk, 0.3 percentage points; 95% CI, -0.6 to 1.2). Major bleeding occurred in 1 patient (0.1%) in the treatment group and in 1 (0.1%) in the control group (absolute difference in risk, 0 percentage points; 95% CI, -0.6 to 0.7). In the POT-CAST trial, 1519 patients underwent randomization, of whom 1435 were included in the intention-to-treat population. Venous thromboembolism occurred in 10 of the 719 patients (1.4%) in the treatment group and in 13 of the 716 patients (1.8%) in the control group (relative risk, 0.8; 95% CI, 0.3 to 1.7; absolute difference in risk, -0.4 percentage points; 95% CI, -1.8 to 1.0). No major bleeding events occurred. In both trials, the most common adverse event was infection.

CONCLUSIONS

The results of our trials showed that prophylaxis with low-molecular-weight heparin for the 8 days after knee arthroscopy or during the full period of immobilization due to casting was not effective for the prevention of symptomatic venous thromboembolism. (Funded by the Netherlands Organization for Health Research and Development; POT-KAST and POT-CAST ClinicalTrials.gov numbers, NCT01542723 and NCT01542762 , respectively.).

Therapeutic Update on the Prevention and Treatment of Venous Thromboembolism

Venous thromboembolism (VTE) is a common condition that increases in incidence with age and risk factors. Therapies for VTE are aimed at either preventing the disease in high-risk individuals or treating patients who have developed VTE. Assessing risk and aggressively using the recommended therapies is primacy in preventing VTE in surgical and medical patients. Risk of VTE in medical patients has become more defined in recent years, and prophylaxis in this group can prevent scores of iatrogenic VTE. Treatment of VTE has evolved in the past decade from a condition that required hospitalization for 5 to 7 days to a disease state that can be conveniently and safely treated on an outpatient basis, largely due to the advent of low-molecular-weight heparins and patient self-directed treatment.

Anticoagulants (extended duration) for prevention of venous thromboembolism following total hip or knee replacement or hip fracture repair

BACKGROUND

The optimal duration of thromboprophylaxis after total hip or knee replacement, or hip fracture repair remains controversial. It is common practice to administer prophylaxis using low-molecular-weight heparin (LMWH) or unfractionated heparin (UFH) until discharge from hospital, usually seven to 14 days after surgery. International guidelines recommend extending thromboprophylaxis for up to 35 days following major orthopaedic surgery but the recommendation is weak due to moderate quality evidence. In addition, recent oral anticoagulants that exert effect by direct inhibition of thrombin or activated factor X lack the need for monitoring and have few known drug interactions. Interest in this topic remains high.

OBJECTIVES

To assess the effects of extended-duration anticoagulant thromboprophylaxis for the prevention of venous thromboembolism (VTE) in people undergoing elective hip or knee replacement surgery, or hip fracture repair.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Specialised Register (last searched May 2015) and CENTRAL (2015, Issue 4). Clinical trials databases were searched for ongoing or unpublished studies.

SELECTION CRITERIA

Randomised controlled trials assessing extended-duration thromboprophylaxis (five to seven weeks) using accepted prophylactic doses of LMWH, UFH, vitamin K antagonists (VKA) or direct oral anticoagulants (DOAC) compared with short-duration thromboprophylaxis (seven to 14 days) followed by placebo, no treatment or similar extended-duration thromboprophylaxis with LMWH, UFH, VKA or DOACs in participants undergoing hip or knee replacement or hip fracture repair.

DATA COLLECTION AND ANALYSIS

We independently selected trials and extracted data. Disagreements were resolved by discussion. We performed fixed-effect model meta-analyses with odds ratios (ORs) and 95% confidence intervals (CIs). We used a random-effects model when there was heterogeneity.

MAIN RESULTS

We included 16 studies (24,930 participants); six compared heparin with placebo, one compared VKA with placebo, two compared DOAC with placebo, one compared VKA with heparin, five compared DOAC with heparin and one compared anticoagulants chosen at investigators' discretion with placebo. Three trials included participants undergoing knee replacement. No studies assessed hip fracture repair.Trials were generally of good methodological quality. The main reason for unclear risk of bias was insufficient reporting. The quality of evidence according to GRADE was generally moderate, as some comparisons included a single study, low number of events or heterogeneity between studies leading to wide CIs.We showed no difference between extended-duration heparin and placebo in symptomatic VTE (OR 0.59, 95% CI 0.35 to 1.01; 2329 participants; 5 studies; high quality evidence), symptomatic deep vein thrombosis (DVT) (OR 0.73, 95% CI 0.39 to 1.38; 2019 participants; 4 studies; moderate quality evidence), symptomatic pulmonary embolism (PE) (OR 0.61, 95% CI 0.16 to 2.33; 1595 participants; 3 studies; low quality evidence) and major bleeding (OR 0.59, 95% CI 0.14 to 2.46; 2500 participants; 5 studies; moderate quality evidence). Minor bleeding was increased in the heparin group (OR 2.01, 95% CI 1.43 to 2.81; 2500 participants; 5 studies; high quality evidence). Clinically relevant non-major bleeding was not reported.We showed no difference between extended-duration VKA and placebo (one study, 360 participants) for symptomatic VTE (OR 0.10, 95% CI 0.01 to 1.94; moderate quality evidence), symptomatic DVT (OR 0.13, 95% CI 0.01 to 2.62; moderate quality evidence), symptomatic PE (OR 0.32, 95% CI 0.01 to 7.84; moderate quality evidence) and major bleeding (OR 2.89, 95% CI 0.12 to 71.31; low quality evidence). Clinically relevant non-major bleeding and minor bleeding were not reported.Extended-duration DOAC showed reduced symptomatic VTE (OR 0.20, 95% CI 0.06 to 0.68; 2419 participants; 1 study; moderate quality evidence) and symptomatic DVT (OR 0.18, 95% CI 0.04 to 0.81; 2459 participants; 2 studies; high quality evidence) compared to placebo. No differences were found for symptomatic PE (OR 0.25, 95% CI 0.03 to 2.25; 1733 participants; 1 study; low quality evidence), major bleeding (OR 1.00, 95% CI 0.06 to 16.02; 2457 participants; 1 study; low quality evidence), clinically relevant non-major bleeding (OR 1.22, 95% CI 0.76 to 1.95; 2457 participants; 1 study; moderate quality evidence) and minor bleeding (OR 1.18, 95% CI 0.74 to 1.88; 2457 participants; 1 study; moderate quality evidence).We showed no difference between extended-duration anticoagulants chosen at investigators' discretion and placebo (one study, 557 participants, low quality evidence) for symptomatic VTE (OR 0.50, 95% CI 0.09 to 2.74), symptomatic DVT (OR 0.33, 95% CI 0.03 to 3.21), symptomatic PE (OR 1.00, 95% CI 0.06 to 16.13), and major bleeding (OR 5.05, 95% CI 0.24 to 105.76). Clinically relevant non-major bleeding and minor bleeding were not reported.We showed no difference between extended-duration VKA and heparin (one study, low quality evidence) for symptomatic VTE (OR 1.64, 95% CI 0.85 to 3.16; 1279 participants), symptomatic DVT (OR 1.36, 95% CI 0.69 to 2.68; 1279 participants), symptomatic PE (OR 9.16, 95% CI 0.49 to 170.42; 1279 participants), major bleeding (OR 3.87, 95% CI 1.91 to 7.85; 1272 participants) and minor bleeding (OR 1.33, 95% CI 0.64 to 2.76; 1279 participants). Clinically relevant non-major bleeding was not reported.We showed no difference between extended-duration DOAC and heparin for symptomatic VTE (OR 0.70, 95% CI 0.28 to 1.70; 15,977 participants; 5 studies; low quality evidence), symptomatic DVT (OR 0.60, 95% CI 0.11 to 3.27; 15,977 participants; 5 studies; low quality evidence), symptomatic PE (OR 0.91, 95% CI 0.43 to 1.94; 14,731 participants; 5 studies; moderate quality evidence), major bleeding (OR 1.11, 95% CI 0.79 to 1.54; 16,199 participants; 5 studies; high quality evidence), clinically relevant non-major bleeding (OR 1.08, 95% CI 0.90 to 1.28; 15,241 participants; 4 studies; high quality evidence) and minor bleeding (OR 0.95, 95% CI 0.82 to 1.10; 11,766 participants; 4 studies; high quality evidence).

AUTHORS' CONCLUSIONS

Moderate quality evidence suggests extended-duration anticoagulants to prevent VTE should be considered for people undergoing hip replacement surgery, although the benefit should be weighed against the increased risk of minor bleeding. Further studies are needed to better understand the association between VTE and extended-duration oral anticoagulants in relation to knee replacement and hip fracture repair, as well as outcomes such as distal and proximal DVT, reoperation, wound infection and healing.

Comparative study of extended versus short term thromboprophylaxis in patients undergoing elective total hip and knee arthroplasty in Indian population

BACKGROUND

Postoperative thromboprophylaxis with low molecular weight heparin (LMWH) for an extended period of 4 weeks is now preferred over short term thromboprophylaxis in patients undergoing total hip/knee arthroplasty (THA/TKA). However, most of the data demonstrating the efficacy and safety of extended thromboprophylaxis and short term thromboprophylaxis is from clinical trials done in the West. In India, the data of the incidence of venous thromboembolism (VTE) following THA/TKA has been conflicting and the duration has not been clearly defined. The aim of the study was to evaluate and compare the efficacy of extended thromboprophylaxis over short term thromboprophylaxis in Indian patients undergoing elective THA/TKA surgeries.

MATERIALS AND METHODS

A prospective arm of 197 consecutive patients undergoing elective THA/TKA surgeries who were administered extended thromboprophylaxis for 4 weeks was compared with a historical group of 795 patients who were administered short term thromboprophylaxis for only 7-11 days. In both groups, LMWH (enoxaparin) was used in a dose of 40 mg subcutaneously, in addition to mechanical thromboprophylaxis. Primary efficacy endpoint was objectively confirmed venous thromboembolism (VTE). The presence of DVT was confirmed by a combination of pretest scoring, D-dimer, and Color Doppler Flow Imaging (CDFI) of deep veins of the legs, and pulmonary thromboembolism (PTE) was confirmed by ventilation perfusion (V/Q) scan or pulmonary angiography. Fisher's exact test and t test were used for the statistical analysis. The baseline confounding factors were compared between the two groups using t test for comparing the means for continuous data and Fisher's exact test for categorical data.

RESULTS

In the prospective arm, only 1 patient developed symptomatic PTE compared to 26 (3.27%) cases of VTE (20 cases of PTE and 6 cases of DVT) in the retrospective group.

CONCLUSION

Extended thromboprophylaxis (for 4 weeks) was found to be more effective than short term thromboprophylaxis in minimizing the risk of postoperative VTE in patients who underwent THA/TKA.

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.

Prevention of VTE in orthopedic surgery patients: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

VTE is a serious, but decreasing complication following major orthopedic surgery. This guideline focuses on optimal prophylaxis to reduce postoperative pulmonary embolism and DVT.

METHODS

The methods of this guideline follow those described in Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines in this supplement.

RESULTS

In patients undergoing major orthopedic surgery, we recommend the use of one of the following rather than no antithrombotic prophylaxis: low-molecular-weight heparin; fondaparinux; dabigatran, apixaban, rivaroxaban (total hip arthroplasty or total knee arthroplasty but not hip fracture surgery); low-dose unfractionated heparin; adjusted-dose vitamin K antagonist; aspirin (all Grade 1B); or an intermittent pneumatic compression device (IPCD) (Grade 1C) for a minimum of 10 to 14 days. We suggest the use of low-molecular-weight heparin in preference to the other agents we have recommended as alternatives (Grade 2C/2B), and in patients receiving pharmacologic prophylaxis, we suggest adding an IPCD during the hospital stay (Grade 2C). We suggest extending thromboprophylaxis for up to 35 days (Grade 2B). In patients at increased bleeding risk, we suggest an IPCD or no prophylaxis (Grade 2C). In patients who decline injections, we recommend using apixaban or dabigatran (all Grade 1B). We suggest against using inferior vena cava filter placement for primary prevention in patients with contraindications to both pharmacologic and mechanical thromboprophylaxis (Grade 2C). We recommend against Doppler (or duplex) ultrasonography screening before hospital discharge (Grade 1B). For patients with isolated lower-extremity injuries requiring leg immobilization, we suggest no thromboprophylaxis (Grade 2B). For patients undergoing knee arthroscopy without a history of VTE, we suggest no thromboprophylaxis (Grade 2B).

CONCLUSIONS

Optimal strategies for thromboprophylaxis after major orthopedic surgery include pharmacologic and mechanical approaches.

Efficacy and safety of venous thromboembolism prophylaxis with apixaban in major orthopedic surgery

Over the last 15 years, low-molecular-weight heparins (LMWHs) have been accepted as the “gold standard” for pharmaceutical thromboprophylaxis in patients at high risk of venous thromboembolism (VTE) in most countries around the world. Patients undergoing major orthopedic surgery (MOS) represent a population with high risk of VTE, which may remain asymptomatic or become symptomatic as deep vein thrombosis or pulmonary embolism. Numerous trials have investigated LMWH thromboprophylaxis in this population and demonstrated high efficacy and safety of these substances. However, LMWHs have a number of disadvantages, which limit the acceptance of patients and physicians, especially in prolonged prophylaxis up to 35 days after MOS. Consequently, new oral anticoagulants (NOACs) were developed that are of synthetic origin and act as direct and very specific inhibitors of different factors in the coagulation cascade. The most developed NOACs are dabigatran, rivaroxaban, and apixaban, all of which are approved for thromboprophylaxis in MOS in a number of countries around the world. This review is focused on the pharmacological characteristics of apixaban in comparison with other NOACs, on the impact of NOAC on VTE prophylaxis in daily care, and on the management of specific situations such as bleeding complications during NOAC therapy.

Preoperative versus postoperative initiation of thromboprophylaxis following major orthopedic surgery: safety and efficacy of postoperative administration supported by recent trials of new oral anticoagulants

In European countries, low-molecular-weight heparin is generally initiated preoperatively for thromboprophylaxis in hip or knee replacement surgery. The objective of this review is to compare pre- and postoperative thromboprophylaxis strategies using available evidence, and discuss the challenges and issues that arise. Surgery is the first step in the process of thrombus formation, but thrombosis is not an instant process and the formation and growth of the thrombus can take several days or weeks. Hence, it may be possible to stop this process if thromboprophylaxis is initiated after surgery. Meta-analyses or systematic reviews comparing pre- and postoperative initiation of therapy have found no consistent differences in efficacy and similar safety (bleeding rates) between the two strategies. The recently available oral anticoagulant dabigatran etexilate provides thromboprophylaxis when administered postoperatively and is as safe as preoperative enoxaparin. Further support for the use of postoperative oral thromboprophylaxis in hip or knee replacement surgery has been provided by the phase III clinical trials of rivaroxaban and apixaban versus preoperative enoxaparin. Postoperative thromboprophylaxis offers the opportunity to change management practices in Europe. As postoperative initiation may have a clinical benefit in some settings (e.g. for neuraxial anesthesia) and practical advantages (e.g. allowing same-day admission), it is a worthwhile thromboprophylactic strategy for hip or knee replacement surgery.

Differentiation of parenteral anticoagulants in the prevention and treatment of venous thromboembolism

BACKGROUND

The prevention of venous thromboembolism has been identified as a leading priority in hospital safety. Recommended parenteral anticoagulant agents with different indications for the prevention and treatment of venous thromboembolism include unfractionated heparin, low-molecular-weight heparins and fondaparinux. Prescribing decisions in venous thromboembolism management may seem complex due to the large range of clinical indications and patient types, and the range of anticoagulants available.

METHODS

MEDLINE and EMBASE databases were searched to identify relevant original articles.

RESULTS

Low-molecular-weight heparins have nearly replaced unfractionated heparin as the gold standard antithrombotic agent. Low-molecular-weight heparins currently available in the US are enoxaparin, dalteparin, and tinzaparin. Each low-molecular-weight heparin is a distinct pharmacological entity with different licensed indications and available clinical evidence. Enoxaparin is the only low-molecular-weight heparin that is licensed for both venous thromboembolism prophylaxis and treatment. Enoxaparin also has the largest body of clinical evidence supporting its use across the spectrum of venous thromboembolism management and has been used as the reference standard comparator anticoagulant in trials of new anticoagulants. As well as novel oral anticoagulant agents, biosimilar and/or generic low-molecular-weight heparins are now commercially available. Despite similar anticoagulant properties, studies report differences between the branded and biosimilar and/or generic agents and further clinical studies are required to support the use of biosimilar low-molecular-weight heparins. The newer parenteral anticoagulant, fondaparinux, is now also licensed for venous thromboembolism prophylaxis in surgical patients and the treatment of acute deep-vein thrombosis; clinical experience with this anticoagulant is expanding.

CONCLUSIONS

Parenteral anticoagulants should be prescribed in accordance with recommended dose regimens for each clinical indication, based on the available clinical evidence for each agent to assure optimal safety and efficacy.

Meta regression analysis to indirectly compare dalteparin to enoxaparin for the prevention of venous thromboembolic events following total hip replacement

BACKGROUND

Patients undergoing elective total hip replacement (THR) surgery are at an increased risk for venous thromboembolic events (VTEs). Dalteparin and enoxaparin are recommended as thromboprophylaxis for at least 10 days in these patients. Even though both agents have proven clinical effectiveness through placebo controlled studies, there have been no head to head trials to assess comparative effectiveness. Indirect statistical techniques were used to compare safety and efficacy between dalteparin and enoxaparin following THR surgery.

METHODS

A literature search was conducted from January 1980 to November 2009 for randomized trials evaluating dalteparin or enoxaparin prophylaxis in THR patients. In trials where a common control was used (e.g. placebo), indirect statistical comparisons between dalteparin and enoxaparin were performed using meta regression analysis with active drug as the primary independent variable.

RESULTS

A total of nine placebo controlled enoxaparin (n = 5) and dalteparin (n = 4) trials met the inclusion criteria. THR patients treated with enoxaparin or dalteparin had a 50% VTE risk reduction compared to the placebo control (RR = 0.50, p < 0.001). This benefit was achieved without a significant increase in the risk for major bleeds (RR = 1.19, p = 0.76), heparin induced thrombocytopenia (HIT) (RR = 1.13, p = 0.83) or death (RR = 0.72, p = 0.59). The indirect comparison was not able to find significant differences between enoxaparin and dalteparin in terms of VTEs (p = 0.36), major bleeds (p = 0.45), HIT (p = 0.48) and death (p = 0.86).

CONCLUSIONS

The findings suggested comparable safety and efficacy between dalteparin and enoxaparin in TKR patients. Therefore, treatment decisions should be based on other considerations, such as patient or physician preference, ease of administration and cost.

Meta-analysis of low molecular weight heparin versus placebo in patients undergoing total hip replacement and post-operative morbidity and mortality since their introduction

OBJECTIVES

1) To establish the clinical validity for in-patient low molecular weight heparin (LMWH) following total hip replacement (THR) through a meta-analysis of peer reviewed and published randomised placebo controlled trials (RCTs). 2) To establish whether modern peri-operative practices were associated with changes in rates of clinical venous thromboembolic (VTE) and all-cause mortality after THR by review of series of patients receiving in-patient LMWH published between 1985 and 2000. DATASOURCES: Medline and Embase (from 1980 to 2005), Datastar and Proquest databases were searched and references from bibliographies traced.

REVIEW METHODS

Studies of adult patients receiving in-patient LMWH following elective primary or revision THR were sought and data abstracted. The first part of our analysis included only randomised placebo controlled trials. For the second part, randomised control trials were included and divided by their year of completion into three groups.

RESULTS

We found no difference between LMWH and placebo in the risk of fatal pulmonary embolism (PE), other deaths, all cause mortality or major bleeding. LMWH reduced non-fatal PE (OR=0.14, 95%CI 0.03 to 0.74, p=0.029) at the expense of haematoma formation (7/147 vs 0/149, p=0.015). 35 studies were included in the second part of our analysis. Point estimates of rates of fatal and non-fatal pulmonary embolism and other deaths suggest a decline over time but fell short of statistical significance.

CONCLUSION

Clinically relevant VTEs are a rare complication following THR. The lower risk of VTE narrows the risk benefit of potent pharmacological thromboprophylaxis. We do not support their use in patients undergoing THR without additional thromboembolic risk factors.

Review article: thromboprophylaxis after total hip replacement

The risk of secondary haematologic complications such as deep vein thrombosis or pulmonary embolism increases significantly when a transient period of hypercoagulability is induced after total hip replacement (THR). A number of drug-based anticoagulant approaches are available to modulate this risk, but the optimal length of therapy for such approaches remains unclear. The literature was reviewed for evidence-based support of the routine use of an extended course (>14 days) of thromboprophylaxis after THR. Electronic databases and real-time online literature searches were performed, using the PubMed (Medline), EMBASE, CINAHL and GoogleScholar, and the Cochrane and British Medical Journal Clinical Evidence libraries. Author-defined key word searches were performed. Only articles in the English language, for which full text could be retrieved, were reviewed. There is robust evidence to support an extended course (>14 days) of thromboprophylaxis after THR. Such recommendations have been translated into the guidelines of key professional bodies, including those of the American College of Chest Physicians. Meta-review suggests a clear benefit of such regimens and supports wider adoption, even when weighed against a small increase in adverse events.

Need to improve thromboprophylaxis across the continuum of care for surgical patients

INTRODUCTION

Prophylaxis for venous thromboembolism (VTE) is underused following major surgery and frequently stopped at hospital discharge despite short stays and high VTE risk for several weeks postsurgery. We evaluated inpatient and postdischarge prophylaxis in patients who underwent major abdominal or orthopedic surgery.

METHODS

Patient records were assessed for anticoagulant use by cross-matching data from the Premier's Perspective discharge database with the i3/Ingenix LabRx outpatient and inpatient database from January 2005 to December 2007. Abdominal or orthopedic surgery patients at risk of VTE according to the 2004 American College of Chest Physicians guidelines and with no contraindications to anticoagulation were included.

RESULTS

A total of 14,009 eligible surgical discharges were analyzed. Only 27.9% of the 10,698 abdominal surgery patients received anticoagulation in hospital. Most inpatients received unfractionated heparin (12.3% of the total abdominal surgery population) or enoxaparin (11.8%). Of the 3311 orthopedic surgery patients, 91.1% received in-hospital anticoagulation. Similar proportions of patients received enoxaparin (32.1%), warfarin (31.1%), or other agents (28.0%). Only 1.2% of abdominal surgery patients had an anticoagulant prescription filled 30 days postdischarge. Although orthopedic surgery outpatients had higher anticoagulation rates, only 54.4% had filled a prescription 30 days postdischarge with 31.1% receiving warfarin, 18.5% receiving enoxaparin, and 4.8% receiving other anticoagulants. The higher prophylaxis rate in orthopedic patients may reflect the high VTE risk in orthopedic surgery patients and increased awareness among orthopedic surgeons.

CONCLUSION

This real-world study highlights the underuse of thromboprophylaxis in hospitalized surgical patients, especially following abdominal surgery. Furthermore, a considerable proportion of these patients do not receive postdischarge anticoagulation despite guideline recommendations. Further efforts are needed to improve anticoagulant use, particularly in the outpatient setting.

The ''critical thrombosis period'' in major orthopedic surgery: when to start and when to stop prophylaxis

Patients undergoing major orthopedic surgery are at high venous thromboembolism (VTE) risk, with morbid and potentially fatal consequences. Anticoagulant VTE prophylaxis reduces rates of postoperative deep vein thrombosis by up to 60% to 70% in these patients. Therefore, pharmacological prophylaxis with low-molecular-weight heparins (LMWHs), vitamin K antagonists, or fondaparinux is recommended by current guidelines. However, there remains an ongoing debate regarding when to initiate and the optimal duration for prophylaxis. Here, we discuss the mechanisms underlying thrombus formation in patients undergoing major orthopedic surgery, and we review the current literature on the benefit-to-risk ratio associated with preoperative and postoperative initiation of thromboprophylaxis and also the benefit-to-risk ratio in cases of neuraxial anesthesia. We also discuss the duration of postoperative VTE risk following major orthopedic surgery and assess the ''critical thrombosis period'' when prophylaxis should be provided. Current literature reflects the need to balance the improved efficacy of initiating prophylaxis close to the surgery with increased risk of perioperative bleeding. Evidence from pathology, epidemiology, and clinical studies suggests the risk period for VTE begins at surgery and extends well beyond hospitalization-a crucial issue when considering how long to give prophylaxis-and, in the case of total hip arthroplasty, for at least 3 months after surgery. Literature supports the greater use of ''just-in-time'' thromboprophylaxis initiation and after-discharge continuation of optimal prophylaxis in orthopedic surgery patients. Providing optimal thromboprophylaxis throughout the critical thrombosis period where a patient is at VTE risk will ensure the best reductions in VTE-related morbidity and mortality.

Prophylaxis of venous thromboembolism in the US: improving hospital performance

Venous thromboembolism (VTE) prevention has been recognized as the most important practice for improving patient safety in hospitals. To be effective, VTE prophylaxis must be appropriately prescribed with respect to type, dose and duration. Large-scale studies of medical discharge records have highlighted low rates of appropriate thromboprophylaxis in hospitalized medical patients, especially those with cancer or severe lung disease. Lack of prophylaxis and an insufficient duration are the most common forms of inappropriate prophylaxis. Multifaceted, active, quality improvement initiatives have been developed and shown to successfully increase the appropriate prescribing of VTE prophylaxis in patients at risk. By increasing the use of appropriate VTE prophylaxis in at-risk patients, the disease burden of hospital-acquired VTE and its resulting complications can be reduced.

Cost-effectiveness of prolonged thromboprophylaxis after cancer surgery

BACKGROUND

Consensus guidelines recommend prolonged thromboprophylaxis for up to 4 weeks after major abdominopelvic cancer operations. Several factors impede widespread adoption of these guidelines. These include lack of awareness, cost, increased bleeding complications, increased incidence of heparin-induced thrombocytopenia, and poor patient compliance.

METHODS

A cost-effectiveness model was constructed comparing four potential strategies to postdischarge thromboprophylaxis in surgical oncology patients: (1) low-molecular-weight heparin (LMWH) once daily; (2) low-dose unfractionated heparin (LDUH) three times daily; (3) oral aspirin once daily; or (4) no prolonged prophylaxis. Probabilities and costs were estimated on the basis of published literature and average Medicare reimbursement. The decision analysis was conducted from the perspective of the health care system, with the primary end point being cost per patient without venous thromboembolism (VTE). Sensitivity analyses tested the robustness of the results.

RESULTS

LDUH was most cost-effective, saving $154 per patient without VTE compared with no prophylaxis. LMWH was not cost-effective, incurring a cost of $230 per patient without VTE compared with no prophylaxis. Aspirin was a viable alternative to LDUH, saving $123 compared with no prophylaxis. When poor compliance was considered, aspirin became the dominant strategy. Sensitivity analyses failed to show any instance where LMWH was cost-effective. In terms of population costs, widespread use of LDUH after discharge would save $30.3 million per year in the United States.

CONCLUSIONS

Although all chemical prophylaxis is effective in preventing VTE in the outpatient setting after cancer surgery, either LDUH or aspirin are the most cost-effective, depending on patient compliance.

Overview of current venous thromboembolism protocols in hip reconstruction

Venous thromboembolic disease continues to be a serious complication of total-hip arthroplasty. The use of anticoagulant drugs for preventing this complication has repeatedly been proven to be useful. This article reviews the current evidence-based recommendations for anticoagulant prophylaxis after total-hip arthroplasty and provides insight into the current areas of active research and controversy.

[Thromboembolic disease in orthopedic surgery]

Thromboembolic complications are frequent after orthopaedic surgery of the limbs. Strategies to minimize these complications go from recognize the risk factors of the patient to introduce new antithrombotic drugs, and including general medical care, regional anaesthesia and early mobilization. Based in epidemiological studies, prophylaxis must be extended 4-6 weeks in total hip and knee arthroplasty and in surgery of the hip fracture.

Extended duration rivaroxaban versus short-term enoxaparin for the prevention of venous thromboembolism after total hip arthroplasty: a double-blind, randomised controlled trial

BACKGROUND

The risk of venous thromboembolism is high after total hip arthroplasty and could persist after hospital discharge. Our aim was to compare the use of rivaroxaban for extended thromboprophylaxis with short-term thromboprophylaxis with enoxaparin.

METHODS

2509 patients scheduled to undergo elective total hip arthroplasty were randomly assigned, stratified according to centre, with a computer-generated randomisation code, to receive oral rivaroxaban 10 mg once daily for 31-39 days (with placebo injection for 10-14 days; n=1252), or enoxaparin 40 mg once daily subcutaneously for 10-14 days (with placebo tablet for 31-39 days; n=1257). The primary efficacy outcome was the composite of deep-vein thrombosis (symptomatic or asymptomatic detected by mandatory, bilateral venography), non-fatal pulmonary embolism, and all-cause mortality up to day 30-42. Analyses were done in the modified intention-to-treat population, which consisted of all patients who had received at least one dose of study medication, had undergone planned surgery, and had adequate assessment of thromboembolism. This study is registered at ClinicalTrials.gov, number NCT00332020.

FINDINGS

The modified intention-to-treat population for the analysis of the primary efficacy outcome consisted of 864 patients in the rivaroxaban group and 869 in the enoxaparin group. The primary outcome occurred in 17 (2.0%) patients in the rivaroxaban group, compared with 81 (9.3%) in the enoxaparin group (absolute risk reduction 7.3%, 95% CI 5.2-9.4; p<0.0001). The incidence of any on-treatment bleeding was much the same in both groups (81 [6.6%] events in 1228 patients in the rivaroxaban safety population vs 68 [5.5%] of 1229 patients in the enoxaparin safety population; p=0.25).

INTERPRETATION

Extended thromboprophylaxis with rivaroxaban was significantly more effective than short-term enoxaparin plus placebo for the prevention of venous thromboembolism, including symptomatic events, in patients undergoing total hip arthroplasty.

Cost-effectiveness of extended prophylaxis with fondaparinux compared with low molecular weight heparin against venous thromboembolism in patients undergoing hip fracture surgery

A model was developed to estimate costs and clinical effectiveness of fondaparinux compared with enoxaparin after hip fracture surgery in Sweden. Outcomes and costs of venous thromboembolism (VTE)-related care from a health care perspective were incorporated, with symptomatic deep-vein thrombosis and pulmonary embolism, recurrent VTE, post-thrombotic syndrome, major haemorrhage and all-cause death being included. Event probabilities were derived from fondaparinux clinical trial data and published data. VTE-related resource use and associated costs as well as costs of prophylaxis were based on local Swedish data. Extended prophylaxis with fondaparinux could avoid an additional 28 symptomatic VTE per 1,000 patients compared with extended prophylaxis with enoxaparin in hip fracture surgery patients. Although the prophylaxis costs were higher in the fondaparinux group, these were offset by the lower costs associated with treating fewer VTE, which thus indicates that extended fondaparinux prophylaxis is the dominant alternative when compared with enoxaparin in hip fracture surgery.

Optimal duration of prophylaxis for venous thromboembolism following total hip arthroplasty and total knee arthroplasty

Elective total hip arthroplasty and total knee arthroplasty are associated with a high risk of postoperative venous thromboembolism. Traditionally, antithrombotic prophylaxis has been administered during the hospital stay. However, with patients spending less time in the hospital after surgery, there is a need to continue thromboprophylaxis beyond hospital discharge. The current recommendation for prophylaxis in total joint arthroplasty patients is a minimum of 10 days, with extended prophylaxis up to 28 to 35 days following total hip arthroplasty. Prophylaxis with low-molecular-weight heparins for approximately 4 weeks following hip arthroplasty has resulted in clinically significant reductions in the incidence of venographically confirmed deep vein thrombosis. Currently, no data support extended thromboprophylaxis beyond 10 days following total knee arthroplasty. Using weighted risk factors to assess individual risk for venous thromboembolism can help the physician determine the optimal duration of prophylaxis.

Extended duration of thromboprophylaxis in acutely ill medical patients: optimizing therapy?

Summary. Patients who are hospitalized for an acute medical illness are at risk of venous thromboembolism (VTE). Current evidence-based guidelines recommend prophylaxis with unfractionated heparin or low-molecular-weight heparin in acutely ill medical patients who are admitted to hospital with congestive heart failure, severe respiratory disease, or who are bedridden with an additional VTE risk factor. The need for thromboprophylaxis is therefore clear in this patient population; however, the optimal duration of prophylaxis in these patients is less clear. In patients undergoing orthopedic or cancer surgery, extended-duration prophylaxis has been shown to be superior to placebo. To date, however, no large-scale clinical trials have assessed the benefits of extended-duration prophylaxis in acutely ill medical patients. This review therefore focuses on the VTE risk profile of acutely ill medical patients, examines the currently available literature for evidence of a potential benefit of extended-duration prophylaxis in these patients, and provides a rationale for the testing of such a hypothesis in a randomized clinical trial.

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.

Review of the rebound phenomenon in new anticoagulant treatments

BACKGROUND

The launch of new anticoagulant treatments has sparked debate as to the optimal drug to use for primary prevention of venous thromboembolism (VTE) in major orthopaedic surgery, for the treatment of VTE, and for stroke prevention in atrial fibrillation, taking into account both efficacy and tolerability. Newer drugs such as fondaparinux and ximelagatran have shown improvements in short-term efficacy or convenience, but such effects may be offset by reduced tolerability. They also raise the question of a possible delayed increase in thromboembolic events after these drugs are stopped, the so-called 'rebound effect'.

OBJECTIVE

To review pharmacological and clinical data describing the rebound effect associated with new and standard anticoagulant drugs.

RESEARCH DESIGN AND METHODS

Computerized searches, covering the period 1960-2005 for the historical background and physiopathology review, and from 1999 to 2005 for the clinical trial analysis, were performed on BIOSIS, PubMed and clinicaltrials.gov databases. The terms 'rebound', 'anticoagulant', and 'heparin' were used. Only articles written in English were reviewed. Articles with drug interactions from other therapeutic classes or types of vascular surgery and commentary articles were excluded.

RESULTS

Available data in relation to a possible rebound phenomenon following cessation of active treatment are very limited. Results coming mainly from orthopaedic surgery trials suggest an increased rate of venous or arterial thromboembolic events with newer anticoagulants, compared with standard anticoagulant therapy. An increase in the rate of serious arterial adverse events has, for example, been observed in VTE patients treated with ximelagatran relative to those receiving warfarin/placebo (short-term exposure: 0.75% vs 0.26%, p < 0.05; long-term exposure: 1.70% vs 0.70%, p <or= 0.1).

CONCLUSIONS

Further clinical trials or meta-analyses are needed before we can determine whether the unexpected thromboembolic events found with newer anticoagulants can be linked to a rebound effect on treatment cessation.

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.

Primary and secondary prophylaxis of venous thromboembolism with low-molecular-weight heparins: prolonged thromboprophylaxis, an alternative to vitamin K antagonists

Low-molecular-weight heparins (LMWHs) are used widely in the treatment and prevention of venous thromboembolism (VTE). The LMWHs dalteparin and enoxaparin reduce the rate of VTE by at least 50% if administered for 4-5 weeks following major orthopedic surgery, compared with in-hospital prophylaxis for 7-15 days. Meta-analyses have confirmed that the size of the reduction is similar for both clinical and asymptomatic VTE. Vitamin K antagonists (VKAs) have been shown to be associated with significantly higher bleeding rates compared with LMWH when used as prolonged prophylaxis against VTE following major orthopedic surgery. Patients with cancer are a recognized group at high risk of VTE, and those undergoing major surgery for their malignancy are at particular risk. Evidence from clinical trials is amassing to show that prolonged prophylaxis with LMWH (dalteparin, enoxaparin) in these patients can significantly reduce the rate of postoperative VTE. In cancer patients with acute VTE, the traditional approach is to initiate acute treatment with unfractionated heparin or LMWH followed by long-term treatment with VKA to prevent recurrence. However, clinical trial data have confirmed that the LMWH dalteparin, when administered for 6 months, is significantly more effective than VKA in preventing recurrence, cutting the rate of VTE by 52% without increasing the risk of bleeding. A new and intriguing area of interest is whether LMWH can enhance survival in patients with cancer. Preliminary data suggest that a biological effect of LMWH may act to prolong survival in patients with cancer.