Low-molecular-weight heparinoid orgaran is more effective than aspirin in the prevention of venous thromboembolism after surgery for hip fracture

The efficacy and safety of aspirin in preventing venous thrombosis in major orthopedic surgery: An updated meta-analysis of randomized controlled trials

BACKGROUND

Major orthopedic surgery, including hip and knee replacement and lower extremity trauma fractures surgery, is associated with a high risk of venous thromboembolism (VTE), especially proximal deep vein thrombosis (DVT), and pulmonary embolism (PE), and is linked with high morbidity and mortality rates. Chemical anticoagulation is routinely used to prevent VTE, with previous meta-analyses reporting on the efficacy and safety of aspirin and other anticoagulants, however, opinions are divided. In the past 2 years, several large randomized controlled trials have been published, therefore, we reanalyzed aspirin efficacy and safety when compared with other anticoagulants in preventing VTE in major orthopedic surgery.

METHODS

Using PubMed, The Cochrane Library, Embase, and Web of Science databases, we conducted a RCT search in August 2023. The main outcomes included VTE, proximal DVT or PE. Additional outcomes included bleeding events, wound complications, wound infections, blood transfusions, and death events.

RESULTS

In total, 17 eligible articles, involving 29,522 patients (15,253 aspirin vs 14,269 other anticoagulant cases), were included. Primary outcomes showed that VTE incidence was more high in the aspirin group when compared with other anticoagulants (risk ratio [RR] = 1.45, 95% confidence interval [CI] = 1.18-1.77, P = .0004) and proximal in the aspirin group the DVT and/or PE incidence was significantly higher in the aspirin group when compared with other anticoagulants (RR = 1.19, 95% CI = 1.02-1.39, P = .03). No significant secondary outcome differences were identified in the aspirin group when compared with other anticoagulants (bleeding events [RR] = 0.83, 95% CI = 0.63-1.10, P = .20); wound complications (RR = 0.45, 95% CI = 0.20-1.04, P = .06); wound infection (RR = 1.08, 95% CI = 0.85-1.38, P = .53); blood transfusion events (RR = 1.00, 95% CI = 0.84-1.19, P = 1.00) and death events (RR = 1.11, 95% CI = 0.78-1.57, P = .55).

CONCLUSIONS

Our updated meta-analysis showed that aspirin was inferior to when compared with other anticoagulants in VTE-related orthopedic major surgery, including proximal DVT and/or PE, and was more likely to form VTE. No differences between groups were identified for bleeding, wound complications, wound infections, transfusion, or death events.

The Incremental Cost of Inpatient Venous Thromboembolism After Hip Fracture Surgery

OBJECTIVES

To (1) identify trends in the rates of deep venous thrombosis (DVT) and pulmonary embolism (PE) and (2) calculate the additional incremental inpatient cost and length of stay associated with venous thromboembolism (VTE) after hip fracture surgery.

DESIGN

Retrospective database analysis.

SETTING

Hospital discharge data.

PATIENTS/PARTICIPANTS

A total of 838,054 patients undergoing operative treatment of hip fractures in the National Inpatient Sample from 2003 to 2014.

INTERVENTION

Internal fixation or partial/total hip replacement.

MAIN OUTCOME MEASURES

The length of stay and cost of hospitalization were compared between patients with VTE and those without using a Student t-test. A logistic regression model was performed to evaluate the trends in VTE rates, and a multivariable linear regression model was performed to evaluate inpatient hospital costs.

RESULTS

The overall rates of DVT and PE were 0.3% and 0.53%, respectively. VTE was associated with an increased length of stay (9 days vs. 5 days) and increased inpatient cost ($103,860.83 vs. $51,576.00). The rate of DVT over the study period decreased, whereas the rate of PE increased.

CONCLUSIONS

Each episode of VTE after hip fracture is a significant source of additional inpatient cost. Patients who sustain a VTE have approximately twice the length of stay and total inpatient cost compared with those who do not. The rates of DVT after hip fracture surgery are decreasing, whereas the rates of PE are increasing.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Venous thromboembolism after hospital discharge in pelvic and acetabular fracture patients treated operatively

PURPOSE

The purposes of this study were to determine the rate of venous thromboembolism (VTE) after discharge from the hospital in patients treated operatively with a pelvic ring or acetabular fracture and to define the main time frame in which VTE occurs within the 90-day period after hospital discharge.

METHODS

California and Florida State Inpatient Databases from 2005 to 2009 were used to identify patients with clinically significant VTEs within 90 days of hospital discharge. ICD-9 diagnosis codes identified patients with a pelvic ring or acetabular fracture and a VTE. Procedure codes distinguished patients having surgical fracture treatment. Deep vein thrombosis (DVT) and pulmonary embolus (PE) were included.

RESULTS

Overall, 13,589 patients had a pelvic ring or acetabular fracture and operative treatment. One hundred thirteen patients (0.83%) had a VTE within 90 days after hospital discharge: 69 (0.51%) had a DVT, 28 (0.21%) had a PE, and 16 (0.12%) had both. Twenty-four (28%) of DVTs and 10 (23%) of PEs occurred >35 days after discharge, being evenly distributed out to 90 days. There were five fatal PEs, occurring 2, 3, 7, 31, and 51 days after discharge. Therefore, overall, <0.2% of patients developed a DVT and <0.1% were diagnosed with a PE (only 1 fatal; <0.01%) >35 days after the index hospitalization.

CONCLUSIONS

A substantial proportion of VTE events occur over 35 days after discharge; however, the overall risk is low with fatal PE being extremely low (<0.01%). Given the diminished VTE risk after 35 days, the decision to further extend antithrombotic drug therapy may be guided by patient-specific factors, such as prolonged immobility.

Thromboprophylaxis an update of current practice: Can we reach a consensus?

Diagnosis, prophylaxis, and management of venous thromboembolism (VTE) in patients with fractures remain a highly controversial topic with little consensus in clinical practice or the literature. The following manuscript represents a summary of evidence presented at the 2017 OTA Annual Meeting Symposium; "Thromboprophylaxis an Update of Current Practice: Can We Reach A Consensus?" The need for prophylaxis in pelvic and acetabular fracture patients; the existing body of evidence related to VTE, pulmonary embolism (PE), and prophylaxis for patients with fractures about the knee; current evidence in Edinburgh Scotland, regarding VTE prophylaxis in patients with isolated ankle fractures and the risk of VTE in patients with a hip fracture are topics that are addressed. The reader will benefit from the wisdom of this compilation of global contributions on thromboprophylaxis.

Comparison of the Efficacy and Safety of Aspirin and Rivaroxaban Following Enoxaparin Treatment for Prevention of Venous Thromboembolism after Hip Fracture Surgery

OBJECTIVE

To compare the efficacy and safety of aspirin with rivaroxaban following treatment with enoxaparin for prevention of venous thromboembolism (VTE) after hip fracture surgery (HFS).

METHODS

A total of 390 patients were enrolled in the trial. According to an odd or even number at the end of their registration number, the patients were divided into the aspirin group (n = 198) and the rivaroxaban group (n = 192). All patients were given enoxaparin subcutaneous injection after the operation and returned to the routine dose the next day until postoperative day five. The patients in the aspirin group received an additional 16 days of thromboprophylaxis with 100 mg of aspirin once daily. The rivaroxaban group was assigned to receive an additional 16 days of thromboprophylaxis with 10 mg of oral rivaroxaban once daily. Patients were followed for 90 days regarding VTE and bleeding complications.

RESULTS

The incidence of VTE in the aspirin group and rivaroxaban group was 6.6% (13/198) and 5.7% (11/192), respectively (P = 0.83). The rate of major bleeding events occurred in two (1.0%) patients in the aspirin group and in one patient (0.5%) in the rivaroxaban group (P = 1.0). A combination of major bleeding and clinically relevant nonmajor bleeding occurred in five patients (2.5%) in the aspirin group and in six patients (3.1%) in the rivaroxaban group (P = 0.77). During the 90-day follow-up, a pulmonary embolism developed in one patient (0.5%) in the aspirin group and none in the rivaroxaban group (P = 1.0).

CONCLUSIONS

Extended prophylaxis for 21 days with aspirin was equivalent to the direct oral anticoagulant rivaroxaban after hip fracture surgery with an initial 5-day postoperative course of enoxaparin. Aspirin may be an effective, safe, convenient, and cheap alternative for extended prophylaxis after hip fracture surgery.

Venous thromboembolism in plastic surgery: the current state of evidence in risk assessment and chemoprophylactic options

The application of venous thromboembolism (VTE) prophylaxis has been the topic of intense debate in plastic surgery. The overall incidence of VTE is low in plastic surgery patients as compared to other surgical subspecialties but may be higher in the inpatient rather than outpatient plastic surgery populations. The Caprini Risk Assessment Model is the most highly studied and validated tool to assess VTE risk in plastic surgery patients. However, the Caprini model lacks procedure-specific risk assessment and patient-specific risk factor calculations. Due to these limitations, such as the low incidence and the heterogeneous nature of the specialty, trials lacked the power to capture proof of benefit, except in the highest-risk inpatient population. The emerging use of aspirin and novel oral anticoagulants may provide an alternative, as noninferiority in terms of efficacy and safety has been demonstrated in other fields. In this review, the authors intend to summarize the current state of evidence for prevention and explore the modalities available for prophylaxis, including novel oral anticoagulants.

Recent Updates of the Diagnosis and Prevention of Venous Thromboembolism in Patients with a Hip Fracture

Venous thromboembolism (VTE) is a potentially fatal complication that is relatively common after hip surgery. Since patients with a hip fracture have a higher risk of preoperative VTE due to an inability to ambulate after injury and aggravation of underlying age-related conditions, it may be difficult to effectively prevent VTE using only conventional approaches. Very few studies have been published reporting on the prevalence and prevention of VTE in patients with a hip fracture compared to those with hip arthroplasty. For this reason, we aimed to share recent updates on the diagnosis and prevention of VTE in patients with a hip fracture. Preoperative screening tests to diagnose VTE need to be performed more actively following hip fracture and indirect multidetector computed tomography venography is considered the most effective test for this purpose. As the risk of VTE appears to increase with time following a hip fracture, preventive measures should be taken as soon as possible in patients with a hip fracture. A wide variety of mechanical and pharmacological options are available for prophylaxis. When considering patient compliance and preventive impact, intermittent pneumatic compression devices and foot pumps are recommended as mechanical modalities. Of the available preventive medications for patients with a hip fracture, low molecular weight heparin seems to be the most appropriate option because of its short half-life and fast onset of action. Surgery should be performed as soon as possible in patients with hip fractures, and we recommend mechanical and pharmacological methods as active interventions immediately after injury to prevent VTE.

Effect of pathological heterogeneity on shear wave elasticity imaging in the staging of deep venous thrombosis

Background

We aimed to observe the relationship between the pathological components of a deep venous thrombus (DVT), which was divided into three parts, and the findings on quantitative ultrasonic shear wave elastography (SWE) to increase the accuracy of thrombus staging in a rabbit model.

Methods

A flow stenosis-induced vein thrombosis model was used, and the thrombus was divided into three parts (head, body and tail), which were associated with corresponding observation points. Elasticity was quantified in vivo using SWE over a 2-week period. A quantitative pathologic image analysis (QPIA) was performed to obtain the relative percentages of the components of the main clots.

Results

DVT maturity occurred at 2 weeks, and the elasticity of the whole thrombus and the three parts (head, body and tail) showed an increasing trend, with the Young's modulus values varying from 2.36 ± 0.41 kPa to 13.24 ± 1.71 kPa; 2.01 ± 0.28 kPa to 13.29 ± 1.48 kPa; 3.27 ± 0.57 kPa to 15.91 ± 2.05 kPa; and 1.79 ± 0.36 kPa to 10.51 ± 1.61 kPa, respectively. Significant increases occurred on different days for the different parts: the head showed significant increases on days 4 and 6; the body showed significant increases on days 4 and 7; and the tail showed significant increases on days 3 and 6. The QPIA showed that the thrombus composition changed dynamically as the thrombus matured, with the fibrin and calcium salt deposition gradually increasing and the red blood cells (RBCs) and platelet trabecula gradually decreasing. Significant changes were observed on days 4 and 7, which may represent the transition points for acute, sub-acute and chronic thrombi. Significant heterogeneity was observed between and within the thrombi.

Conclusions

Variations in the thrombus components were generally consistent between the SWE and QPIA. Days 4 and 7 after thrombus induction may represent the transition points for acute, sub-acute and chronic thrombi in rabbit models. A dynamic examination of the same part of the thrombus may be helpful for improving the sensitivity and reproducibility of SWE for DVT diagnosis and staging.

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.

Aspirin versus anticoagulation for prevention of venous thromboembolism major lower extremity orthopedic surgery: a systematic review and meta-analysis

BACKGROUND

Hip fracture surgery and lower extremity arthroplasty are associated with increased risk of both venous thromboembolism and bleeding. The best pharmacologic strategy for reducing these opposing risks is uncertain.

PURPOSE

To compare venous thromboembolism (VTE) and bleeding rates in adult patients receiving aspirin versus anticoagulants after major lower extremity orthopedic surgery.

DATA SOURCES

Medline, Cumulative Index to Nursing and Allied Health Literature, and the Cochrane Library through June 2013; reference lists, ClinicalTrials.gov, and scientific meeting abstracts.

STUDY SELECTION

Randomized trials comparing aspirin to anticoagulants for prevention of VTE following major lower extremity orthopedic surgery.

DATA EXTRACTION

Two reviewers independently extracted data on rates of VTE, bleeding, and mortality.

DATA SYNTHESIS

Of 298 studies screened, 8 trials including 1408 participants met inclusion criteria; all trials screened participants for deep venous thrombosis (DVT). Overall rates of DVT did not differ statistically between aspirin and anticoagulants (relative risk [RR]: 1.15 [95% confidence interval {CI}: 0.68-1.96]). Subgrouped by type of surgery, there was a nonsignificant trend favoring anticoagulation following hip fracture repair but not knee or hip arthroplasty (hip fracture RR: 1.60 [95% CI: 0.80-3.20], 2 trials; arthroplasty RR: 1.00 [95% CI: 0.49-2.05], 5 trials). The risk of bleeding was lower with aspirin than anticoagulants following hip fracture repair (RR: 0.32 [95% CI: 0.13-0.77], 2 trials), with a nonsignificant trend favoring aspirin after arthroplasty (RR: 0.63 [95% CI: 0.33-1.21], 5 trials). Rates of pulmonary embolism were too low to provide reliable estimates.

CONCLUSION

Compared with anticoagulation, aspirin may be associated with higher risk of DVT following hip fracture repair, although bleeding rates were substantially lower. Aspirin was similarly effective after lower extremity arthroplasty and may be associated with lower bleeding risk. Journal of Hospital Medicine 2014;9:579-585. © 2014 Society of Hospital Medicine.

Venous thromboembolism and postoperative management of anticoagulation

Deep venous thrombosis and pulmonary embolism are common after fragility fracture surgery, although the incidence is decreasing over time. Prophylaxis is important, because it is effective; additionally, the consequences are significant. Several medications are available for prophylaxis, and the choice of agent should be determined based on patient and surgery characteristics, and balancing of venous thromboembolism (VTE) and bleeding risk. A comprehensive approach to VTE prophylaxis includes consideration of a pharmacologic agent and nonpharmacologic management.

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.

Medical management of hip fractures and the role of the orthogeriatrician

Published literature shows that evidence-based medical care can improve hip fracture outcomes. The orthogeriatrician plays a key role in providing this care, in collaboration with surgical and multidisciplinary professionals, managing pre-operative conditions and post-operative complications that may affect functional recovery, and ensuring co-ordinated effective management of hip fractures right from admission to discharge. Several management guidelines are available for this vulnerable group of elderly patients. Recent UK guidelines recommend that, from time of admission, hip fracture patients should be offered a formal acute orthogeriatric or orthopaedic ward-based ‘Hip Fracture Programme’, which includes orthogeriatric assessment as an essential key component.

Deep vein thrombosis: a clinical review

Background:

Deep vein thrombosis (DVT) is the formation of blood clots (thrombi) in the deep veins. It commonly affects the deep leg veins (such as the calf veins, femoral vein, or popliteal vein) or the deep veins of the pelvis. It is a potentially dangerous condition that can lead to preventable morbidity and mortality.

Aim:

To present an update on the causes and management of DVT.

Methods:

A review of publications obtained from Medline search, medical libraries, and Google.

Results:

DVT affects 0.1% of persons per year. It is predominantly a disease of the elderly and has a slight male preponderance. The approach to making a diagnosis currently involves an algorithm combining pretest probability, D-dimer testing, and compression ultrasonography. This will guide further investigations if necessary. Prophylaxis is both mechanical and pharmacological. The goals of treatment are to prevent extension of thrombi, pulmonary embolism, recurrence of thrombi, and the development of complications such as pulmonary hypertension and post-thrombotic syndrome.

Conclusion:

DVT is a potentially dangerous condition with a myriad of risk factors. Prophylaxis is very important and can be mechanical and pharmacological. The mainstay of treatment is anticoagulant therapy. Low-molecular-weight heparin, unfractionated heparin, and vitamin K antagonists have been the treatment of choice. Currently anticoagulants specifically targeting components of the common pathway have been recommended for prophylaxis. These include fondaparinux, a selective indirect factor Xa inhibitor and the new oral selective direct thrombin inhibitors (dabigatran) and selective factor Xa inhibitors (rivaroxaban and apixaban). Others are currently undergoing trials. Thrombolytics and vena caval filters are very rarely indicated in special circumstances.

Venous thromboembolic prophylaxis for hip fractures

Patients with hip fractures are at very high risk for the development of venous thromboembolism (VTE). To provide an overview of cause, risk factors, current treatment strategies, and complications associated with VTE prophylaxis, we reviewed the most current, best available evidence on VTE prophylaxis for patients with hip fractures. We comprehensively reviewed the literature to assess the efficacy of VTE prophylaxis in patients with hip fractures, including the most recent published guidelines by national medical and surgical health organizations from the UK, USA, and Canada. Mechanical devices are effective in reducing the risk of VTE for hip fracture, but poor patient compliance is common and the devices are not recommended for sole VTE prophylaxis. Aspirin reduces the risk of VTE but does not provide optimal protection compared with other chemical agents; therefore, it is not recommended for sole VTE prophylaxis. Fondaparinux, warfarin, low-molecular-weight heparin, and unfractionated heparin reduce the risk of venographic deep vein thrombosis, but there is insufficient evidence that they reduce fatal pulmonary embolism or all-cause mortality. Fondaparinux is considered to be cost effective and more efficacious than low-molecular-weight heparin. At present, most major health organizations advocate at least 28 days of postoperative chemical prophylaxis. Chemical VTE prophylaxis should be administered to all patients with hip fractures unless contraindicated. Additional research is required to establish an agent that has a significant impact on fatal pulmonary embolism and all-cause mortality, without increasing bleeding complications, in this group of patients.

Comparing consensus guidelines on thromboprophylaxis in orthopedic surgery

BACKGROUND

Different guidelines exist regarding the prevention of venous thromboembolism (VTE) in orthopedic surgery.

OBJECTIVES

We aimed to compare (inter)national guidelines and analyse differences.

METHODS

MEDLINE, the Cochrane Library and the internet were searched for guidelines on the prevention of VTE in orthopedic surgery. From these, we constructed a table comparing the different antithrombotic regimens during different orthopedic surgical and plaster cast treatments.

RESULTS

Eleven guidelines from nine different countries and one international guideline were included. Few guidelines advise on thrombosis prophylaxis after plaster cast immobilization, (prolonged) arthroscopic surgery and isolated lower extremity trauma. Different opinions exist on the sole use of aspirin and mechanical prophylaxis and on the use of vitamin K antagonists after major hip and knee surgery.

CONCLUSION

Based on the same available literature, different guidelines recommend different thromboprophylactic regimens. Ideally, the grade of recommendation should be based on the same level of evidence world-wide. Whilst there is no agreement on the relevance of different endpoints (e.g. asymptomatic DVT), it is very difficult to reach a consensus. Thromboprophylaxis guidelines should be reviewed and updated on a regular basis, because the evidence is evolving rapidly.

Prevention of venous thromboembolism

Venous thromboembolism (VTE) is a preventable cause of significant morbidity and mortality in hospitalized patients, especially in the perioperative period. After identifying the risk factors, it is possible to stratify patients into groups based on their degree of risk for developing VTE. Methods available for the prevention of VTE vary in degree of intensity, efficacy, and side effects. The type of preventive measure used for each patient is based on matching the degree of risk for VTE with the intensity of prophylaxis, keeping in mind the risk-benefit ratio. This article discusses VTE prophylaxis relevant to oral and maxillofacial surgery patients.

Perioperative anticoagulant management

The oral anticoagulant warfarin is a common medication that requires special consideration in the perioperative period. Although some procedures do not require warfarin interruption, the majority will necessitate its temporary cessation due to the risk of bleeding. Determining whether patients will benefit from the temporary use of a heparin product while warfarin is discontinued perioperatively (so-called "bridging" therapy) needs to take into consideration the risk of bleeding balanced with the risk of thromboembolism. Perioperative care also requires minimizing the risk of venous thromboembolism (VTE). Understanding the patient-specific and procedure-specific risks for VTE is paramount to employ optimal risk reduction strategies. This article uses a case-based approach to present the topics of perioperative warfarin management and postoperative VTE prevention.

Contributions of extravascular and intravascular cells to fibrin network formation, structure, and stability

Fibrin is essential for hemostasis; however, abnormal fibrin formation is hypothesized to increase thrombotic risk. We previously showed that in situ thrombin generation on a cell's surface modulates the 3-dimensional structure and stability of the fibrin network. Currently, we compared the abilities of extravascular and intravascular cells to support fibrin formation, structure, and stability. Extravascular cells (fibroblasts, smooth muscle) supported formation of dense fibrin networks that resisted fibrinolysis, whereas unstimulated intravascular (endothelial) cells produced coarse networks that were susceptible to fibrinolysis. All 3 cell types produced a fibrin structural gradient, with a denser network near, versus distal to, the cell surface. Although fibrin structure depended on cellular procoagulant activity, it did not reflect interactions between integrins and fibrin. These findings contrasted with those on platelets, which influenced fibrin structure via interactions between beta3 integrins and fibrin. Inflammatory cytokines that induced prothrombotic activity on endothelial cells caused the production of abnormally dense fibrin networks that resisted fibrinolysis. Blocking tissue factor activity significantly reduced the density and stability of fibrin networks produced by cytokine-stimulated endothelial cells. Together, these findings indicate fibrin structure and stability reflect the procoagulant phenotype of the endogenous cells, and suggest abnormal fibrin structure is a novel link between inflammation and thrombosis.

Perioperative anticoagulant management

The oral anticoagulant warfarin is a common medication that requires special consideration in the perioperative period. Although some procedures do not require warfarin interruption, the majority will necessitate its temporary cessation due to the risk of bleeding. Determining whether patients will benefit from the temporary use of a heparin product while warfarin is discontinued perioperatively (so-called "bridging" therapy) needs to take into consideration the risk of bleeding balanced with the risk of thromboembolism. Perioperative care also requires minimizing the risk of venous thromboembolism (VTE). Understanding the patient-specific and procedure-specific risks for VTE is paramount to employ optimal risk reduction strategies. This article uses a case-based approach to present the topics of perioperative warfarin management and postoperative VTE prevention.

Does acetyl salicylic acid (ASA) have a role in the prevention of venous thromboembolism?

Guidelines differ on whether acetyl salicylic acid (ASA, aspirin) should be used for prophylaxis in patients at high-risk of venous thromboembolism (VTE), principally because of differences in perceptions of its efficacy. ASA is an attractive therapeutic option because it is inexpensive, easy to administer and does not require monitoring. We critically reappraised the evidence from randomized controlled trials for the efficacy of ASA in VTE prevention. ASA is clearly efficacious in preventing VTE compared to placebo or no treatment, but appears to be less efficacious than the low molecular weight heparins in small trials. There is little data for ASA in comparison with unfractionated heparin and warfarin. A large randomized controlled trial is required to clarify the role of ASA compared to contemporary anticoagulant strategies for the prevention of VTE.

Prevention of venous thromboembolism after surgery

Venous thromboembolism, including deep vein thrombosis and pulmonary embolism, is the third leading cause of cardiovascular death after myocardial infarction and stroke in the United States. Recommendations regarding the type and duration of prophylaxis for the various conditions are summarized herein.

Antiplatelet drugs: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This article about currently available antiplatelet drugs is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). It describes the mechanism of action, pharmacokinetics, and pharmacodynamics of aspirin, reversible cyclooxygenase inhibitors, thienopyridines, and integrin alphaIIbbeta3 receptor antagonists. The relationships among dose, efficacy, and safety are thoroughly discussed, with a mechanistic overview of randomized clinical trials. The article does not provide specific management recommendations; however, it does highlight important practical aspects related to antiplatelet therapy, including the optimal dose of aspirin, the variable balance of benefits and hazards in different clinical settings, and the issue of interindividual variability in response to antiplatelet drugs.

Prevention of venous thromboembolism in the geriatric patient

Elderly patients immobilized because of an acute medical illness or surgery have a very high risk of developing venous thromboembolism (VTE). Aggressive pharmacologic prophylaxis is necessary and should be initiated either at admission for a medical condition or shortly after surgery. Aggressive prophylaxis may result in fewer patients developing VTE in the hospital and ultimately lead to fewer patients requiring full-dose anticoagulation for VTE. Mechanical prophylaxis can be used as an adjunct to an anticoagulant-based regimen but should only be used as primary prophylaxis when there is a contraindication, such as active bleeding. It is recommended that the clinician carefully evaluate the elderly patient's creatinine clearance and weight before prescribing anticoagulants, particularly when using fixed dosing regimens.

Aspirin in the prevention and treatment of venous thromboembolism

This review summarizes available evidence on effects of aspirin on incidence and outcomes of venous thromboembolism (VTE). From a pathophysiological point of view, inhibition of platelet aggregation is associated with an impaired thrombus formation both in an experimental model of venous thrombosis and in vivo. Epidemiological evidence in support of a beneficial effect of acetylsalicylic acid on VTE incidence is provided by the Antiplatelet Trialists' Collaboration meta-analysis of studies on the use of antiplatelet agents in cardiovascular risk reduction, showing a significant 25% risk reduction of pulmonary embolism. Moreover, a meta-analysis on older trials of antiplatelet agents in postsurgical VTE prevention and the large Pulmonary Embolism Prevention trial demonstrate a protective effect of the same magnitude: 25-30%. However, as low-molecular-weight heparins (LMWH) and vitamin K antagonists (VKA) have shown a superior efficacy and safety profile, and no direct comparisons have been made between aspirin, LMWH and VKA in prolonged use, the most recent guidelines advise against aspirin monotherapy for thromboprophylaxis in the surgical patient. Currently, there is no evidence to support a role for aspirin in air travel-related VTE. Regarding prevention of recurrent VTE, studies are ongoing to determine the potential role of aspirin after a first unprovoked VTE.

Prevention and Management of Venous Thromboembolism in People with Cancer: A Review of the Evidence

Venous thromboembolism (VTE) constitutes an important health problem in developed countries. Owing to their underlying malignancies, people with cancer are at particularly high risk of VTE. The level of this risk is influenced by several factors, including type of cancer and the presence or absence of metastases. However, different types of oncology treatment can also further increase the thrombotic risk. Consequently, primary and secondary thromboprophylaxis in people with cancer should be considered as part of any integrated oncology treatment. Moreover, recent exciting studies have suggested that low molecular weight heparins (LMWH) may also influence overall survival in people with cancer. Clearly, these findings raise the likelihood that the use of LMWH in oncology practice may increase significantly in the near future. However, it is important to appreciate that the use of thromboprophylaxis in people with cancer is complicated by a number of specific problems. In this overview, we have systematically addressed the difficult clinical issues that are involved in the selection of appropriate primary and secondary thromboprophylaxis for people with cancer.

Prevention of Venous Thromboembolism in the Geriatric Patient

Elderly patients immobilized because of an acute medical illness or surgery have a very high risk of developing venous thromboembolism (VTE). Aggressive pharmacologic prophylaxis is necessary and should be initiated either at admission for a medical condition or shortly after surgery. Aggressive prophylaxis may result in fewer patients developing VTE in the hospital and ultimately lead to fewer patients requiring full-dose anticoagulation for VTE. Mechanical prophylaxis can be used as an adjunct to an anticoagulant-based regimen but should only be used as primary prophylaxis when there is a contraindication, such as active bleeding. It is recommended that the clinician carefully evaluate the elderly patient's creatinine clearance and weight before prescribing anticoagulants, particularly when using fixed dosing regimens.

Thromboembolic disease prophylaxis in patients with hip fracture: a multimodal approach

OBJECTIVES

To assess if pneumatic compression in conjunction with chemoprophylaxis is an effective way to reduce the incidence of deep vein thrombosis in orthopedic trauma patients sustaining fragility hip fractures.

DESIGN

Two hundred patients admitted to the authors' institution between May 1998 and June 2002 for fractures of the hip were prospectively studied. All patients were treated operatively and received the VenaFlow calf compression device on both lower extremities immediately following surgery. Chemical prophylaxis of either aspirin (n = 67) or warfarin (n = 133) was administered in addition to mechanical compression. A noninvasive serial color flow duplex scan was performed 1 to 11 days postoperatively (mean 4.5 days) to determine the presence or absence of deep vein thrombosis. All patients were followed clinically 3 months postoperatively for a clinical evaluation of symptomatic deep vein thrombosis or pulmonary embolism.

RESULTS

Overall, the incidence of deep vein thrombosis was 3.5% (7 of 200) and included only 1 proximal thrombosis (1 out of 200, or 0.5%) and no pulmonary embolism. Five of the 7 patients positive for deep vein thrombosis were in the mechanical compression and warfarin prophylaxis group and 2 were in the aspirin arm of the study. For patients with deep vein thrombosis, the average number of risk factors was 3.71, whereas patients without clots averaged 1.75 clinical risk factors (P < or = 0.05). Three patients in the warfarin group developed bleeding complications (1 with a gastrointestinal bleed and 2 with minor bleeding not at the operative site). No evidence of a symptomatic deep vein thrombosis or pulmonary embolism was reported within a 3-month period following hospitalization.

CONCLUSIONS

Our findings suggest mechanical compression with the VenaFlow calf compression device in conjunction with chemoprophylaxis is an effective means of reducing thromboembolic disease in this high-risk population.

The therapeutic potential of novel anticoagulants

Conventional anticoagulant therapy has been based on indirect inhibition of coagulation factors with heparin and warfarin. These agents display liabilities prompting the development of new anticoagulants over the last two decades. The first to be developed was a series of low molecular weight heparins(LMWHs). Their favourable pharmacokinetic profiles and risk/benefit ratios led to widespread use in Europe and, more recently, approval for their use in the USA. Paralleling the development of LMWHs has been the pursuit of a different strategy focused on direct rather than indirect inhibition of enzymes in the coagulation cascade. In contrast to heparin, LMWHs, or other glycosaminoglycans, direct inhibitors exert their effects independent of either antithrombin III (ATIII) or heparin cofactor II (HCII) and more effectively inhibit clot-bound thrombin or FXa. Highly potent, selective (versus other serine proteases)direct thrombin and FXa inhibitors have been identified and isolated from natural sources, such as leeches, ticks and hookworms. The recombinant forms and analogues of the senatural proteins have been produced using molecular biology techniques, i.e., rHirudin, Hirulogs, recombinant tick anticoagulant peptide (rTAP), recombinant antistasin (rATS) and recombinant nematode anticoagulant peptide-5 (rNAP-5). The design of novel structures or the modification of existing chemicals has led to the synthesis of many non-peptide, low molecular weight inhibitors of thrombin and FXa. Some of them are orally active and may be suitable for long-term clinical use. In addition, considerable progress has been made in developing specific TF/VIIa complex inhibitors. The anticoagulation properties of the new agents are being characterised in experimental studies. Some of them have been advanced to large scale clinical trials and their effectiveness, and sometimes relative ineffectiveness,in arterial and venous thromboembolic disorders has been demonstrated. They are being tested for their potential as new antithrombotic agents that act via direct enzyme inhibition. Thus,the clinician should in future be able to target different thrombotic conditions with proven, specific anticoagulant interventions.

Prevention of thrombosis with warfarin, aspirin, and mechanical methods

Venous thromboembolism (VTE) is a serious disorder and a major cause of morbidity and mortality among acutely ill medical patients. However, despite the growing number of patients with acute medical illnesses who have an associated risk of VTE, the widespread use of VTE prophylaxis does not yet occur for both surgical and nonsurgical patients. Although individuals at greatest risk for VTE include patients undergoing major orthopedic surgery and those with medical conditions that require prolonged immobilization, all patients who have acute medical illnesses should be considered for VTE prophylaxis. Several strategies, including various mechanical and pharmacologic approaches, are currently used for VTE prophylaxis. Increased awareness about the full range of options for VTE prophylaxis can help health care providers select the appropriate course of action to help reduce the incidence of VTE among patients with acute medical illnesses.

Major bleeding rates after prophylaxis against venous thromboembolism: Systematic review, meta-analysis, and cost implications

Objectives: The frequency and consequences of major bleeding associated with anticoagulant prophylaxis for prevention of venous thromboembolism is examined.

Methods: We conducted a systematic review and meta-analysis of controlled trials that reported rates of major bleeding after pharmaceutical thromboprophylaxis in patients undergoing major orthopedic surgery. Thromboprophylactic agents were divided into four groups:warfarin/other coumarin derivatives (WARF), unfractionated heparin (UFH), low molecular weight heparin (LMWH), and pentasaccharide (PS). Meta-analysis was conducted comparing LMWH with each of WARF, UFH, and PS. The frequency of re-operation due to major bleeding was reviewed and combined with published costs to estimate the mean cost of managing major bleeding events in these patients.

Results: Twenty-one studies including 20,523 patients met inclusion criteria for the meta-analysis. No evidence of significant between-trial heterogeneity in risk ratios was found. Combined (fixed effects) relative risks (RR) of major bleeding compared with LMWH were WARF – RR 0.59 (95 percent confidence interval [CI], 0.44–0.80); UFH – RR 1.52 (95 percent CI, 1.04–2.23); PS – RR 1.52 (95 percent CI, 1.11–2.09). Seventy-one studies including 32,433 patients were included in the review of consequences of major bleeding. We estimated that the average cost of major bleeding is $113 per patient receiving thromboprophylaxis.

Conclusions: LMWH results in fewer major bleeding episodes than UFH and PS but more than WARF. These events are costly and clinically important.

Prevention of venous thromboembolism: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy

This article discusses the prevention of venous thromboembolism (VTE) and is part of the Seventh American College of Chest Physicians Conference on Antithrombotic and Thrombolytic Therapy: Evidence-Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this chapter are the following. We recommend against the use of aspirin alone as thromboprophylaxis for any patient group (Grade 1A). For moderate-risk general surgery patients, we recommend prophylaxis with low-dose unfractionated heparin (LDUH) (5,000 U bid) or low-molecular-weight heparin (LMWH) [< or = 3,400 U once daily] (both Grade 1A). For higher risk general surgery patients, we recommend thromboprophylaxis with LDUH (5,000 U tid) or LMWH (> 3,400 U daily) [both Grade 1A]. For high-risk general surgery patients with multiple risk factors, we recommend combining pharmacologic methods (LDUH three times daily or LMWH, > 3,400 U daily) with the use of graduated compression stockings and/or intermittent pneumatic compression devices (Grade 1C+). We recommend that thromboprophylaxis be used in all patients undergoing major gynecologic surgery (Grade 1A) or major, open urologic procedures, and we recommend prophylaxis with LDUH two times or three times daily (Grade 1A). For patients undergoing elective total hip or knee arthroplasty, we recommend one of the following three anticoagulant agents: LMWH, fondaparinux, or adjusted-dose vitamin K antagonist (VKA) [international normalized ratio (INR) target, 2.5; range, 2.0 to 3.0] (all Grade 1A). For patients undergoing hip fracture surgery (HFS), we recommend the routine use of fondaparinux (Grade 1A), LMWH (Grade 1C+), VKA (target INR, 2.5; range, 2.0 to 3.0) [Grade 2B], or LDUH (Grade 1B). We recommend that patients undergoing hip or knee arthroplasty, or HFS receive thromboprophylaxis for at least 10 days (Grade 1A). We recommend that all trauma patients with at least one risk factor for VTE receive thromboprophylaxis (Grade 1A). In acutely ill medical patients who have been admitted to the hospital with congestive heart failure or severe respiratory disease, or who are confined to bed and have one or more additional risk factors, we recommend prophylaxis with LDUH (Grade 1A) or LMWH (Grade 1A). We recommend, on admission to the intensive care unit, all patients be assessed for their risk of VTE. Accordingly, most patients should receive thromboprophylaxis (Grade 1A).

Bilateral vs. ipsilateral venography as the primary efficacy outcome measure in thromboprophylaxis clinical trials: a systematic review

Contrast venography, in combination with symptomatic venous thromboembolism (VTE), is the standard efficacy outcome measure in clinical trials of thromboprophylaxis in major orthopedic surgery. It is uncertain whether performing bilateral venography offers any real advantage over venography of the operated leg alone. This study was undertaken to determine the risk of isolated contralateral deep vein thrombosis (DVT) following major orthopedic surgery and to evaluate whether bilateral venography, rather than venography on the operated leg alone, offers any gain in DVT detection and, thereby, improves efficiency in clinical study design. A systematic review of prospective studies that reported DVT incidence as the primary efficacy outcome based on mandatory bilateral venography in patients undergoing elective hip or knee arthroplasty or hip fracture repair was conducted. Based on the use of bilateral venography as a primary efficacy outcome measure, the incidence of any DVT is 16.7% following total hip replacement, 18.8% after hip fracture repair, and 33.8% after total knee replacement. While DVT risk in the operated leg varies depending on the type of surgery, the risk of isolated DVT in the non-operated leg is approximately 4% to 5% in all three procedures. By increasing the detection of any DVT, the use of bilateral venography reduces required sample size by 16% to 25% compared to ipsilateral venography. In clinical trials evaluating the efficacy of thromboprophylaxis in major orthopedic surgery, bilateral venography reduces the risk of undiagnosed DVT in the non-operated leg and improves the efficiency of study design by substantially reducing the sample size requirement.

Platelet-Active Drugs: The Relationships Among Dose, Effectiveness, and Side Effects

This article discusses platelet active drugs as part of the Seventh American College of Chest Physicians Conference on Antithrombotic and Thrombolytic Therapy: Evidence-Based Guidelines. New data on antiplatelet agents include the following: (1) the role of aspirin in primary prevention has been the subject of recommendations based on the assessment of cardiovascular risk; (2) an increasing number of reports suggest a substantial interindividual variability in the response to antiplatelet agents, and various phenomena of "resistance" to the antiplatelet effects of aspirin and clopidogrel; (3) the benefit/risk profile of currently available glycoprotein IIb/IIIa antagonists is substantially uncertain for patients with acute coronary syndromes who are not routinely scheduled for early revascularization; (4) there is an expanding role for the combination of aspirin and clopidogrel in the long-term management of high-risk patients; and (5) the cardiovascular effects of selective and nonselective cyclooxygenase-2 inhibitors have been the subject of increasing attention.

Evidence for Extended Prophylaxis in the Setting of Orthopedic Surgery

Patients undergoing orthopedic surgery represent one of the highest risk groups for the development of venous thromboembolism (VTE). Evidence shows that this risk extends beyond the period in which the patient is hospitalized, especially for patients undergoing hip surgery. Clinical trials have shown that extended prophylaxis with the low-molecular-weight heparins is effective in reducing the rate of total VTE, and a meta-analysis demonstrated a reduction in symptomatic VTE with extended prophylaxis after total hip replacement surgery. Based on these results, the American College of Chest Physicians gives a grade 2A recommendation for the use of extended prophylaxis after orthopedic surgery. Until recently, data evaluating the role of prophylaxis in patients undergoing hip fracture surgery were limited. Subsequently, a novel anticoagulant, fondaparinux, demonstrated significant benefit in these patients and has become the first and only agent approved by the United States Food and Drug Administration (FDA) for use in patients undergoing hip fracture surgery Despite the limitations of the older trials, their findings supported the need to evaluate extended prophylaxis in patients undergoing hip fracture surgery. In the first well-conducted trial of extended prophylaxis for hip fracture surgery, fondaparinux provided impressive results in reducing total and symptomatic VTE. The results of this trial have once again led to fondaparinux being the first and only agent to be granted FDA approval for the indication of extended prophylaxis in patients undergoing hip fracture surgery.

A cost-effectiveness analysis of fondaparinux sodium compared with enoxaparin sodium as prophylaxis against venous thromboembolism: use in patients undergoing major orthopaedic surgery

OBJECTIVE

To determine the cost effectiveness of fondaparinux sodium compared with enoxaparin sodium for prophylaxis against venous thromboembolism in patients undergoing major orthopaedic surgery.

METHODS

Using a cohort simulation model, two primary analyses were conducted from the perspective of the US healthcare payer. Probabilities for a trial-based analysis were obtained from patients participating in the fondaparinux clinical trial programme supplemented with data from published literature. Probabilities for a label-based analysis were estimated for a hypothetical cohort of US patients receiving either fondaparinux or enoxaparin as recommended by US FDA-approved labelling. Resource use and costs were obtained from large US healthcare databases. Outcome measures were rates of symptomatic thromboembolic events and healthcare costs. Costs were in 2003 values.

RESULTS

In the trial-based analysis, fondaparinux was estimated to prevent 15.1 symptomatic venous thromboembolic events (per 1,000 patients) at 3 months for patients undergoing major orthopaedic surgery compared with enoxaparin. The cost savings (per patient) of using fondaparinux over enoxaparin are US 61 dollars at 30 days, US 89 dollars at 3 months, and US 155 dollars at 5 years. In the label-based analysis, fondaparinux was estimated to prevent 17.8 venous thromboembolic events (per 1,000 patients) at 3 months compared with enoxaparin, producing savings per patient of US 25 dollars at discharge, US 112 dollars over 1 month, US 141 dollars over 3 months and US 234 dollars over 5 years. Results remain robust to clinically plausible variation in input parameters and assumptions.

CONCLUSION

Our model suggests that fondaparinux, when compared with the current standard regimen of enoxaparin for prophylaxis of venous thromboembolism in major orthopaedic surgery, improves outcomes and is cost saving from a US healthcare-payer perspective over the broad range of assumptions evaluated.

Evidence‐based guidelines for fixing broken hips: an update

OBJECTIVE

To update evidence-based guidelines for the treatment of proximal femoral fractures published in the Journal in 1999.

DATA SOURCES

Systematic literature search of MEDLINE, CINAHL and EMBASE from January 1996 to September 2001 and the Cochrane Database of Systematic Reviews (most recent issue searched - Issue 2, 2002).

STUDY SELECTION

Randomised controlled trials and meta-analyses of all aspects of acute-care hospital treatment and rehabilitation of proximal femoral fractures among subjects aged 50 years and over with proximal femoral fractures not associated with metastatic disease or multiple trauma.

DATA EXTRACTION

All studies were read independently by two reviewers. Reviewers recorded individual study results, and an assessment of study quality and treatment conclusions according to Cochrane Collaboration protocols. If necessary, a third review was performed to reach consensus.

RESULTS

93 new studies were identified and 82 met our inclusion criteria. Recommendations for thromboprophylaxis, anaesthesia, surgical fixation of fractures and nutritional status have been altered to incorporate new evidence. Recommendations have been added regarding postoperative blood transfusion, the management of subtrochanteric fractures, and the type of surgical swabs which should be used.

CONCLUSIONS

Although there have been few significant changes to the previous recommendations, updating the guidelines has required substantial effort. The common clinical problem of hip fracture should be treated according to the most up-to-date evidence to achieve the best possible outcomes and optimal utilisation of limited resources. Guideline updates also require resourcing.

Improvements in the prevention of postoperative venous thromboembolism in hip fracture patients

Hip fracture surgery carries a high risk of venous thromboembolism and, until recently, was poorly investigated. The efficacy and safety of fondaparinux, a new synthetic antithrombotic, were investigated in two large, thromboprophylaxis studies. Results of the Penthifra study, which was a randomized, double-blind phase III trial, showed that 1 week of fondaparinux, compared with enoxaparin, significantly reduced venous thromboembolic events from 19.1% to 8.3% (relative risk reduction: 56.4%; P<.001) without increasing bleeding risk. Penthifra Plus results showed that extending fondaparinux prophylaxis from 1 to 4 weeks was well tolerated and, compared to placebo, significantly reduced delayed venous thromboembolism events from 35% to 1.4% (relative risk reduction: 95.9%; P<.001). Based on these findings, 4-week fondaparinux treatment may become the standard thromboprophylaxis after hip fracture surgery.

Selective factor Xa inhibition improves efficacy of venous thromboembolism prophylaxis in orthopedic surgery

Venous thromboembolism is a serious, frequent, and potentially fatal complication of major orthopedic surgery. Currently available pharmacologic agents for the prevention of venous thromboembolism in this high-risk population consist of the oral anticoagulants and the heparin family of antithrombotic agents (unfractionated heparin, low-molecular-weight heparin, heparinoids). These classes of agents interfere with the activity of both thrombin and factor Xa (or their respective zymogens) to varying degrees. Newer antithrombotic agents in various stages of development exert their antithrombotic effect through a more targeted mechanism of action. Direct factor Xa inhibitors and the newest class of antithrombotic agents, the indirect factor Xa inhibitors, the prototype of which is the synthetic pentasaccharide fondaparinux sodium, limit fibrin formation through their exclusive inactivation of factor Xa. Clinical data from venous thromboembolism prophylaxis trials in hip and knee replacement and hip fracture surgeries, including the recently completed fondaparinux phase II and phase III trials, indicate that selective antifactor Xa activity may improve the efficacy:safety ratio of antithrombotic therapies for the prevention of venous thromboembolism in high-risk major orthopedic surgery.