Low-molecular-weight heparin (enoxaparin) as prophylaxis against venous thromboembolism after total hip replacement

New developments in the prevention and treatment of venous thromboembolism

Although unfractionated heparin has been widely used for preventing and treating venous thromboembolism, low-molecular-weight heparins (LMWHs) have been extensively studied. In particular, LMWHs have been valuable in the prevention of venous thromboembolism in high-risk surgical patients, such as those undergoing total joint replacement, and in high-risk medical patients. Recent studies indicated that the extended use of LMWHs after discharge in patients undergoing total hip replacement significantly decreases the frequency of venous thrombosis compared with placebo. Furthermore, LMWHs have been shown to be as effective and safe as unfractionated heparin for the initial treatment of both deep vein thrombosis and pulmonary embolism and have extended the treatment of these conditions into the outpatient setting. New recommendations from the sixth American College of Chest Physicians Consensus Conference on Antithrombotic Therapy and the rationale for change are discussed.

Low-molecular-weight heparins are essentially the same for treatment and prevention of venous thromboembolism

The pharmacodynamic properties of low-molecular-weight heparins differ. Data from randomized clinical trials show that despite these differences, the agents have similar efficacy and safety profiles in preventing and treating new and recurrent venous thromboembolism in patients who underwent general surgery or total hip or knee replacement. Dalteparin, enoxaparin, or tinzaparin, when administered at the dosages used in the reviewed clinical trials, are essentially indistinguishable.

Clinical and economic aspects of managing venous thromboembolism in the outpatient setting

Low-molecular-weight heparins (LMWHs) are at least as effective and safe as unfractionated heparin (UFH) in the prevention and initial treatment of venous thromboembolism (VTE), and their fixed-dose, once- or twice-daily dosing regimen without laboratory monitoring makes them suitable for outpatient use. Postoperative thromboprophylaxis usually continues until hospital discharge, but evidence demonstrates that the VTE risk persists for several weeks. Economic pressures, changes in clinical practice, and patient preferences make hospital stays shorter. As a result, outpatient thromboprophylaxis with LMWH has been investigated. LMWH self-administered at home once daily for up to 4 weeks after hospital discharge is safe and well tolerated and significantly reduces the incidence of postdischarge VTE after hip replacement. Targeted appropriately, extended thromboprophylaxis may be cost effective, and the development of an autoinjection device may increase the proportion of patients eligible for home management. LMWHs may also be of value as long-term secondary thromboprophylaxis in patients with contraindications to oral anticoagulants. Standard initial treatment for VTE comprises intravenous UFH administered to the patient in the hospital. However, three large-scale studies have demonstrated the efficacy and safety of outpatient treatment of acute VTE using LMWHs. The economic benefits of shortening or eliminating inpatient therapy are substantial, but successful home treatment requires careful patient selection, intensive education and a comprehensive system of professional support to optimize compliance and safety.

Prolonged enoxaparin therapy to prevent venous thromboembolism after primary hip or knee replacement. Enoxaparin Clinical Trial Group

BACKGROUND

Patients undergoing hip or knee joint replacement are at risk for venous thromboembolic complications for up to twelve weeks postoperatively. We evaluated the efficacy and safety of a prolonged post-hospital regimen of enoxaparin, a low-molecular-weight heparin, in this patient population.

METHODS

Following elective total hip or knee replacement, 968 patients received subcutaneous enoxaparin (30 mg twice daily) for seven to ten days, and 873 were then randomized to receive three weeks of double-blind outpatient treatment with either enoxaparin (40 mg once daily) or a placebo. The primary efficacy end point was the prevalence of objectively confirmed venous thromboembolism or symptomatic pulmonary embolism during the double-blind phase of treatment.

RESULTS

Of the 873 randomized patients, 435 underwent elective total hip replacement and 438 underwent elective total knee replacement. Enoxaparin was superior to the placebo in reducing the prevalence of venous thromboembolism in patients treated with hip replacement: 8.0% (eighteen) of the 224 patients treated with enoxaparin had venous thromboembolism compared with 23.2% (forty-nine) of the 211 patients treated with the placebo (p < 0.001; odds ratio, 3.62; 95% confidence interval, 2.00 to 6.55; relative risk reduction, 65.5%). Enoxaparin had no significant benefit in the patients treated with knee replacement: thirty-eight (17.5%) of the 217 patients treated with enoxaparin had venous thromboembolism compared with forty-six (20.8%) of the 221 patients treated with the placebo (p = 0.380; odds ratio, 1.24; 95% confidence interval, 0.76 to 2.02; relative risk reduction, 15.9%). Symptomatic pulmonary embolism developed in three patients, one with a hip replacement and two with a knee replacement; all had received the placebo. There was no significant difference in the prevalence of hemorrhagic episodes or other types of toxicity between the enoxaparin and placebo-treated groups.

CONCLUSIONS

Prolonging enoxaparin thromboprophylaxis following hip replacement for a total of four weeks provided therapeutic benefit, by reducing the prevalence of venous thromboembolism, without compromising safety. A similar benefit was not observed in patients treated with knee replacement.

Prevention of venous thromboembolism

Recognition of the patient at risk and delivery of appropriate prophylaxis are imperative to reduce the incidence of VTE (including fatal PE) in hospitalized patients. This article provides estimates of risk and a summary of effective prophylaxis methods such that physicians can tailor an individual patient's prophylaxis regimen to maximize DVT risk reduction in the safest and most cost-effective manner.

Dosing and monitoring of low-molecular-weight heparins in special populations

As a result of numerous clinical trials and meta-analyses supporting the superior efficacy and relative safety of low-molecular-weight heparins (LMWHs) compared with unfractionated heparin (UFH), LMWHs are emerging as the antithrombotic agents of choice for the prevention and treatment of deep vein thrombosis and pulmonary embolism. In addition, data indicate that enoxaparin given with low-dosage aspirin is more effective than UFH in treating acute coronary syndromes. Anti-Xa activity can be used as a biologic marker of LMWH activity. Because of the more predictable anticoagulant response to subcutaneous administration of LMWHs compared with UFH, routine monitoring of anti-Xa activity in clinically stable adults with uncomplicated disease is not recommended. Because the optimal dosage of LMWHs has not been established for patients with renal insufficiency or extremes of body weight, during pregnancy, or for children, anti-Xa activity monitoring may be warranted in these subsets.

Low-molecular-weight heparin prophylaxis: preoperative versus postoperative initiation in patients undergoing elective hip surgery

Administration of low-molecular-weight heparin prophylaxis in elective hip implant patients commonly begins 12 h preoperatively in European practices to optimize effectiveness, and 12 to 24 h postoperatively in North American practices to optimize safety. A meta-analysis comparing these two treatment regimes revealed that preoperative initiation demonstrated greater efficacy and superior safety for patients (10.0% rate of total deep-vein thrombosis vs. 15.3%, P = .023). In addition to the pre/postsurgical debate, proximity of initiation of low-molecular-weight heparin in relation to surgery is an issue of critical importance. Recent studies revealed that beginning therapy immediately within 2 h preoperatively or 6 h postoperatively dramatically decreased the risk of venous thrombosis. An investigation of low-molecular-weight heparin prophylaxis initiated 2 h before elective hip surgery or approximately 6 h after surgery compared with warfarin sodium revealed that total and proximal deep-vein thrombosis rates were reduced in patients receiving low-molecular-weight heparin compared with warfarin. The frequencies of deep-vein thrombosis for patients receiving preoperative and postoperative dalteparin vs. warfarin for all deep-vein thrombosis were 36 of 337 (10.7%, P < .001) and 44 of 336 (13.1%, P < .001) vs. 81 of 338 (24.0%); and for proximal deep-vein thrombosis were 3 of 354 (0.8%, P = .035) and 3 of 358 (0.8%, P = .033) vs. 11 of 363 (3.0%). Relative risk reductions for the dalteparin groups vs. warfarin ranged from 45% to 72%. In this case, low-molecular-weight heparin administered in close proximity to surgery provided superior efficacy over warfarin. Major bleeding was significantly increased with the preoperative regimen but not the postoperative regimen.

Low-molecular-weight heparin: the optimal duration of prophylaxis against postoperative venous thromboembolism after total hip or knee replacement

Venous thromboembolism is a major health problem. In about 20% of cases, the initial clinical manifestation of venous thromboembolism is sudden death due to pulmonary embolism. Consequently, appropriate prophylaxis is critical in order to improve survival. Because patients with recent surgery have a 22-fold increased risk of postoperative venous thromboembolism, a large research effort has been directed toward identifying the safest and most effective prophylaxis after surgery, especially after total hip or knee replacement. While low-molecular-weight heparin is the most effective prophylaxis currently available, from 15% to 30% of hip or knee replacement patients still develop deep vein thrombosis by the time of hospital discharge, and another 25% develop new deep vein thrombosis by 3 weeks after discharge. Extended out-of-hospital low-molecular-weight heparin prophylaxis can safely reduce the prevalence of deep vein thrombosis by about 50%. However, essentially all of these thrombi are small, asymptomatic, and resolve without serious clinical sequelae. Based on one clinical trial, out-of-hospital low-molecular-weight heparin prophylaxis could reduce the incidence of symptomatic venous thromboembolism or all-cause death after discharge by a maximum of 2.2%. At current drug costs, universal out-of-hospital low-molecular-weight heparin prophylaxis is unlikely to be cost-effective. For most patients, 7 to 10 days of low-molecular-weight heparin prophylaxis is adequate. Future research should be directed at identifying patients at risk for out-of-hospital venous thromboembolism, and targeting extended prophylaxis to those at highest risk.

Predictors of rehospitalization for symptomatic venous thromboembolism after total hip arthroplasty

BACKGROUND

Recent studies have shown that symptomatic venous thromboembolism after total hip arthroplasty most commonly develops after the patient is discharged from the hospital. Risk factors associated with these symptomatic thromboembolic events are not well defined.

METHODS

Using administrative data from the California Medicare records for 1993 through 1996, we identified 297 patients 65 years of age or older who were rehospitalized for thromboembolism within three months after total hip arthroplasty. We compared demographic, surgical, and medical variables potentially associated with the development of thromboembolism in these patients and 592 unmatched controls.

RESULTS

A total of 89.6 percent of patients with thromboembolism and 93.8 percent of control patients were treated with pneumatic compression, warfarin, enoxaparin, or unfractionated heparin, alone or in combination. In addition, 22.2 percent and 29.7 percent, respectively, received warfarin after discharge. A body-mass index (the weight in kilograms divided by the square of the height in meters) of 25 or greater was associated with rehospitalization for thromboembolism, with an odds ratio of 2.5 (95 percent confidence interval, 1.8 to 3.4). In a multivariate model, the only prophylactic regimens associated with a reduced risk of thromboembolism were pneumatic compression in patients with body-mass indexes of less than 25 (odds ratio, 0.3; 95 percent confidence interval, 0.2 to 0.6) and warfarin treatment after discharge (odds ratio, 0.6; 95 percent confidence interval, 0.4 to 1.0).

CONCLUSIONS

In patients who underwent total hip arthroplasty, a body-mass index of 25 or greater was associated with subsequent hospitalization for thromboembolism. Pneumatic compression in patients with a body-mass index of less than 25 and prophylaxis with warfarin after discharge were independently protective against thromboembolism.

Economic evaluation of enoxaparin as postdischarge prophylaxis for deep vein thrombosis (DVT) in elective hip surgery

OBJECTIVES

Clinical trials indicate enoxaparin thromboprophylaxis (Clexane) can be effective and safe when used in an outpatient setting and that extending the length of thromboprophylaxis with enoxaparin to the postdischarge period may be more effective than inpatient thromboprophylaxis alone. This may increase the cost of thromboprophylaxis. The objective of the study was to estimate the expected cost-effectiveness of using enoxaparin for hospital admission only vs. enoxaparin for hospital admission and for 21 days postdischarge.

METHODS

Decision analysis was used to combine probability, resource use and unit cost data, using the framework of cost-effectiveness analysis. The model used a societal perspective to estimate the expected costs of treatment and outcomes to patients undergoing orthopedic surgery for elective hip replacement. Incremental cost-effectiveness ratios were calculated to provide estimates of the cost per life gained, cost per year life year gained and cost per quality-adjusted life year gained with extended use of enoxaparin thromboprophylaxis.

RESULTS

There was an expected cost per quality-adjusted life year gained of pounds 5732 associated with extended enoxaparin thromboprophylaxis. The results were sensitive to the percentage of patients who could administer enoxaparin injections at home, the rate of DVT associated with standard enoxaparin thromboprophylaxis and the rate of PE associated with standard and extended enoxaparin thromboprophylaxis.

CONCLUSIONS

The analyses indicated that in most cases extended enoxaparin thromboprophylaxis resulted in increased costs for health care services. In all cases, extended thromboprophylaxis with enoxaparin was associated with improved survival and life-years gained.

Changes of hemostatic molecular markers after gynecological surgery

The authors evaluated the hemostatic abnormalities occurring in the postoperative period of eight patients with malignant tumors and compared them with those occurring in the postoperative period of eight patients with benign tumors. Two of the patients with malignant tumor presented pulmonary embolism after operation. Plasma fibrinogen and fibrin degradation product levels in patients with malignant tumors were already high before operation and further increased significantly after operation. The plasma levels of D-dimer, thrombin-antithrombin complex, and free-tissue factor pathway inhibitor were increased in both groups after operation, but they were higher in patients with malignant tumors than in patients with benign tumors. The plasma levels of protein C and antithrombin were significantly decreased in both groups after operation. but they were significantly lower in patients with malignant tumors than in those with benign tumors. The decreased activity of protein C or antithrombin may be not only a risk factor of thrombotic disease, such as pulmonary embolism, but also the cause of thrombosis. In patients with malignant tumors, the operation time was significantly longer than that in patients with benign tumors. This long operative period might cause vascular endothelial cell injury which is reflected by the plasma levels of free-tissue factor pathway inhibitor, antithrombin, and protein C.

Symptomatic and asymptomatic deep vein thrombosis after total hip replacement. Differences in phlebographic pattern, described by a scoring of the thrombotic burden

The aim was to describe the phlebographic pattern of asymptomatic and symptomatic deep vein thrombosis (DVT) after total hip replacement by the use of a scoring system in 102 consecutive patients (54 asymptomatic, 48 symptomatic). The DVTs were scored from 1 to 3, and registered in a scoring system dividing the deep veins into 12 separate segments. The asymptomatic patients had a significantly lower total mean DVT score of 3.7 compared to 9.1 in the symptomatic group of patients. The mean ratio of the DVT scores in the deep muscle veins in conjunction with the superficial femoral vein in relation to the total mean score was significantly higher in the asymptomatic patients (74.9%) compared to the symptomatic group (62.4%). A direct sign of DVT, displayed as a filling defect, was seen on the phlebogram in 116 of the 119 legs, and concomitant nonfilling in other vein segments was noted in 6% of the asymptomatic patients, while in the symptomatic group this was the case to a significantly higher level, namely, 46%. A subgroup of asymptomatic patients operated unilaterally, with bilateral DVT had a significantly higher total mean DVT score on the operated side (4. 6) compared to the unoperated side (3.4). The total mean DVT score increased with time after surgery in the group of symptomatic patients. A low total mean DVT score with a predominance of DVT in, or in the connection to, the deep muscle veins is displayed among the asymptomatic patients. This is significantly different from the symptomatic patients who have more extensive DVTs, especially when diagnosed several weeks postoperatively, and frequently with edema and occlusive DVT.

Management of venous and cardiovascular thrombosis: enoxaparin

Enoxaparin has strong clinical evidence that supports its license in a broad spectrum of therapeutic indications, including thromboprophylaxis in surgical patients, medical patients bedridden because of acute illness, the once-daily treatment of venous thromboembolism and the treatment of unstable angina and non-Q wave myocardial infarction.

Prolonged prophylaxis with unfractioned heparin is effective to reduce delayed deep vein thrombosis in total hip replacement

The aim of this study was to assess the incidence of deep vein thrombosis (DVT) and pulmonary embolism (PE) until 45 days after elective total hip replacement (THR) and the efficacy of prolonged unfractioned heparin (UH) prophylaxis up to postoperative day 30. To this end 79 of 96 patients admitted consecutively to the University Hospital of Pisa for THR were randomly assigned to short- or long-term UH prophylaxis. Sixty-one patients completed the study: 28 of them received short-term prophylaxis (subcutaneous UH 15,000 IU/24 h for 15 days) and 33 prolonged prophylaxis (subcutaneous UH 15,000 IU/24 h for 30 days). Lower limb phlebography was performed in all patients on day 45 after THR. DVT was demonstrated in 10 (16.3%) cases after hospital discharge. Among them, 2 patients also had symptomatic PE. The incidence of DVT was 21.4% in short- and 12.1% in long-term UH-treated patients. The incidence of only proximal DVT was 17.8% in short- and 3.0% in long-term UH-treated patients; although the difference was only close to significance (p = 0.085), the relative risk of developing proximal DVT was about six times greater in the former group of patients. We concluded that the risk for thromboembolism persists at least until 45 days after surgery in patients subjected to THR. Prophylaxis with UH given up to postoperative day 30 appears more effective and safer in reducing the delayed thromboembolic risk compared to prophylaxis with UH given up to discharge only.

The risk of venous thromboembolism is increased throughout the course of malignant glioma: an evidence-based review

BACKGROUND

Venous thromboembolism (VTE) frequently complicates the course of patients with cancer, and there is evidence to suggest that patients with brain tumors are at particularly high risk. The objective of this methodology-based literature review was to quantify the rate of incidence of VTE in patients with malignant glioma and to determine the factors that predict an increased risk of this complication.

METHODS

Studies meeting predefined inclusion criteria were evaluated independently on an eight-item methodology index by three raters. Authors were contacted to resolve ambiguities. The results of the studies were summarized and the incidence rate of VTE within the early postoperative phase and during extended follow-up were reported separately.

RESULTS

Within 6 weeks after surgery the incidence rate of deep venous thrombosis (DVT) ranged from 3% to 60%, varying with the prophylaxis regimen used, the method of diagnosis, and the study design. Beyond 6 weeks postoperatively, the rates of DVT ranged from 0.013 to 0.023 per patient-month of follow-up. The single study with no significant methodologic deficiencies found a 24% rate of incidence of symptomatic DVT over the 17 months of follow-up beyond the first 6 postoperative weeks. In 6 studies the presence of leg paresis, histologic diagnosis of glioblastoma multiform, age >/= 60 years, large tumor size, use of chemotherapy, and length of surgery > 4 hours were identified as possible risk factors.

CONCLUSIONS

The incidence of VTE is high throughout the course of malignant glioma. A randomized, controlled trial is needed to clarify whether the benefits of long term anticoagulant prophylaxis outweigh the risks and costs of such therapy.

Prophylaxis for deep venous thrombosis and pulmonary embolism in the surgical patient

The fifth American College of Chest Physicians Consensus Conference on Antithrombotic Therapy provides the most up-to-date guidelines for the prevention of deep venous thrombosis (DVT) and pulmonary embolism (PE) in the surgical patient (1). These recommendations have become a major guideline for clinicians managing patients in the perioperative period. Despite these recommendations, there remains a concern for balancing the risk of major postoperative bleeding with the benefit of preventing thrombosis. In an attempt to resolve this issue, clinicians have requested clear-cut guidelines for identification of high-risk groups for whom prophylaxis must be used. This article will review the etiology, risk-factor stratification, regimens of prophylaxis, and recommendations for prevention of postoperative DVT and PE.

Dalteparin: an update of its pharmacological properties and clinical efficacy in the prophylaxis and treatment of thromboembolic disease

Dalteparin is a low molecular weight heparin (LMWH) with a mean molecular weight of 5000. Compared with unfractionated heparin (UFH), the drug has markedly improved bioavailability and increased plasma elimination half-life, and exerts a greater inhibitory effect on plasma activity of coagulation factor Xa relative to its effects on other coagulation parameters. Dalteparin also has less lipolytic activity than UFH. Dalteparin 2500U once daily subcutaneously is of similar antithrombotic efficacy to UFH 5000IU twice daily, and 2 studies have shown superiority over UFH 2 or 3 times daily of dalteparin 5000U once daily in patients requiring surgical thromboprophylaxis. After total hip arthroplasty, dalteparin was superior to adjusted-dosage warfarin and was of greater thromboprophylactic efficacy when given for 35 than for 7 days. Intravenous or subcutaneous dalteparin is as effective as intravenous UFH when given once or twice daily in the initial management of established deep vein thrombosis (DVT). The drug is also effective in long term home treatment. Dalteparin has been shown to be effective in combination with aspirin in the management of unstable coronary artery disease (CAD), with composite end-point data from 1 study suggesting benefit for up to 3 months. Current data indicate potential of the drug in the management of acute myocardial infarction (MI). Dalteparin is also of similar efficacy to UFH, with a single bolus dose being sufficient in some patients, in the prevention of clotting in haemodialysis and haemofiltration circuits. Pharmacoeconomic data indicate that overall costs relative to UFH from a hospital perspective can be reduced through the use of dalteparin in patients receiving treatment for venous thromboembolism. Dalteparin has also been shown to be cost effective when used for surgical thromboprophylaxis. Overall, rates of haemorrhagic complications in patients receiving dalteparin are low and are similar to those seen with UFH.

CONCLUSIONS

Dalteparin is effective and well tolerated when given subcutaneously once daily in the prophylaxis and treatment of thromboembolic disease. The simplicity of the administration regimens used and the lack of necessity for laboratory monitoring facilitate home or outpatient treatment and appear to translate into cost advantages from a hospital perspective over UFH or warfarin. Dalteparin also maintains the patency of haemodialysis and haemofiltration circuits, with beneficial effects on blood lipid profiles and the potential for prophylaxis with a single bolus injection in some patients. Data are also accumulating to show dalteparin to be an effective and easily administered alternative to UFH in patients with CAD.

Management of thromboembolism in the outpatient setting

Low-molecular-weight heparins (LMWHs) are suitable for self-administration at home, because they have a predictable anticoagulant effect following subcutaneous injection and do not require laboratory monitoring. Clinical trials evaluating the safety and efficacy of LMWHs in the outpatient setting for the prevention of deep vein thrombosis (DVT) after orthopedic surgery and for the treatment of established DVT are reviewed. Extended LMWH prophylaxis reduces the incidence of venographically detected DVT by approximately 50%. Medical practice relies heavily on clinical diagnosis of DVT, for which both sensitivity and specificity are poor. It is uncertain how the results of research trials on DVT prevention based on venography relate to ordinary practice. In the treatment of established DVT, there was no significant difference between outpatient management with LMWH and inpatient treatment with unfractionated heparin (UFH). However, outpatient management offered a considerable reduction in resource usage, with associated cost savings.

Enoxaparin and bleeding complications: a review in patients with and without renal insufficiency

STUDY OBJECTIVE

To compare the frequency of bleeding complications from enoxaparin in patients with normal renal function versus patients with renal insufficiency.

DESIGN

Retrospective chart review.

SETTING

University-based tertiary care center.

PATIENTS

One hundred six patients who received two or more doses of enoxaparin.

MEASUREMENTS AND MAIN RESULTS

Total bleeding complications occurred in 22% of patients with normal renal function and 51% with renal insufficiency (p<0.01). Major bleeds were also significantly different, 2% and 30%, respectively (p<0.001). No patients with normal renal function were given fresh-frozen plasma or packed red blood cells, whereas in those with renal insufficiency, 13% and 32%, respectively, received these products (p<0.01).

CONCLUSION

Enoxaparin may have resulted in increased bleeding complications and use of blood products in patients with renal insufficiency. Prospective studies need to be conducted to define the drug's role and dosage adjustments in these patients.

Ardeparin sodium for extended out-of-hospital prophylaxis against venous thromboembolism after total hip or knee replacement. A randomized, double-blind, placebo-controlled trial

BACKGROUND

The optimal duration of prophylaxis against venous thromboembolism after total hip or knee replacement is uncertain.

OBJECTIVE

To determine the efficacy and safety of extended out-of-hospital prophylaxis with low-molecular-weight heparin (ardeparin sodium).

DESIGN

Randomized, double-blind, placebo-controlled trial.

SETTING

33 community, university, or university-affiliated hospitals.

PATIENTS

1195 adults who had elective total hip or knee replacement and completed 4 to 10 days of postoperative ardeparin prophylaxis.

INTERVENTION

Daily subcutaneous ardeparin (100 anti-Xa IU/kg of body weight) or placebo from time of hospital discharge to 6 weeks after surgery.

MEASUREMENTS

Symptomatic, objectively documented venous thromboembolism or death, along with major bleeding, from time of hospital discharge to 12 weeks after surgery.

RESULTS

Patients who received ardeparin (n = 607) and those who received placebo (n = 588) did not differ significantly in the cumulative incidence of venous thromboembolism or death (9 cases [1.5%] compared with 12 cases [2.0%]; odds ratio, 0.7 [95% CI, 0.3 to 1.7]; P > 0.2; absolute difference, -0.56 percentage points [CI, -2.2 to 1.1 percentage points]) or major bleeding (2 cases [0.3%] compared with 3 cases [0.5%]).

CONCLUSIONS

Among patients who had total knee or total hip replacement and received 4 to 10 days of postoperative ardeparin prophylaxis, the cumulative incidence of symptomatic venous thromboembolism or death after hospital discharge was not significantly reduced by extended out-of-hospital ardeparin prophylaxis. Extended ardeparin use could provide a maximum 2.2-percentage point true reduction in such events. The benefit of extended ardeparin use is not clinically important for most patients. Future research should identify high-risk patients who would benefit most from extended prophylaxis.

Isolated nonfilling of contrast in deep leg vein segments seen on phlebography, and a comparison with color Doppler ultrasound, to assess the incidence of deep leg vein thrombosis

Nonfilling of contrast in deep veins on phlebography is claimed to be an indirect sign of deep vein thrombosis (DVT) by some authors but rejected by others. The aim of this study was to prospectively assess, with color Doppler ultrasound (CDU), the occurrence and distribution of DVT in isolated, nonfilling, deep vein segments seen on a phlebogram. One hundred consecutive patients with clinical signs of acute DVT, in whom phlebography displayed nonfilling of the posterior tibial veins and/or the deep calf muscle veins, were examined with CDU on the same occasion. Ultrasound confirmed a DVT in 31 (31%) patients; in another 38 (38%) patients other pathology, without concomitantly detected DVT, such as edema, bleedings, ligament and muscle ruptures, Baker cysts, or superficial thrombophlebitis were found instead; and in the remaining 31 (31%) patients no pathology that could explain the nonfilling was identified. Isolated, nonfilling of the posterior tibial and/or deep muscle veins of the calf found by phlebography may be an indirect sign of DVT but is equally commonly caused by other pathological conditions or arises without any detectable explanation. When the thrombotic burden is to be scored, and to facilitate the establishment of the correct diagnosis, additional CDU is recommended when isolated nonfilling is present.

Tranexamic acid, given at the end of the operation, does not reduce postoperative blood loss in hip arthroplasty

We performed a randomized double-blind study on the effect of tranexamic acid on postoperative blood loss and blood transfusions in 39 primary THR operations. Tranexamic acid was given at the end of the operation and 3 hours later. Ultrasound examination 1 week later was performed to measure the occurrence of deep hematomas. In contrast to previous findings in knee arthroplasty, the administration of tranexamic acid failed to give a significant reduction in the postoperative blood loss. This lack of effect was possibly related to the fact that the drug was administered too late. In 11 of the 20 patients receiving tranexamic acid, blood transfusion was not necessary, this being the case in 4/19 in the placebo group (p = 0.05). The occurrence of postoperative deep venous thromboses was similar in the tranexamic acid and placebo groups.

Dose-dependent release of endogenous tissue factor pathway inhibitor by different low molecular weight heparins

Tissue factor pathway inhibitor (TFPI) is released to circulating blood after intravenous and subcutaneous injections of heparins, and may thus contribute to the antithrombotic effect of heparins. A previous study suggested different abilities of various low molecular weight heparins (LMWH) to release endogenous TFPI, but the dose-response relationship was not determined. In the present study, the dose-response relationship for escalating doses of two LMWHs, dalteparin and enoxaparin, on the release of endogenous TFPI was investigated. Six healthy male participants were given 50, 100 and 200 U/kg dalteparin and 0.5, 1.0 and 2.0 mg/kg enoxaparin as a single subcutaneous injection. The study was a randomized, cross-over design with a 1-week wash-out period between each injection. Peak free TFPI antigen and TFPI activity were detected after only 1 h, whereas anti-activated factor X (anti-FXa) and anti-activated factor II (anti-FIIa) activities were detected after 2-6 h. Putative therapeutic equivalent doses of dalteparin and enoxaparin gave similar release of endogenous TFPI, but dissimilar effects on anti-FXa and anti-FIIa activities.

Cost effectiveness of outpatient anticoagulant prophylaxis after total hip arthroplasty

Guidelines for deep venous thrombosis (DVT) and pulmonary embolism (PE) prophylaxis have been developed for patients undergoing total hip arthroplasty (THA). Studies suggest that risk for developing these complications may exist for as long as 3 months following surgery. Cost-effectiveness analyses were performed on three pharmacoprophylaxis regimens administered over a 30-day period using literature-reported values for incidences of DVT and PE in patients postdischarge following THA. A cost savings of $21,466.89 will occur for each thromboembolic event avoided if low-dose warfarin daily is used routinely compared to enoxaparin 40 mg daily. Additionally, a cost savings of $18,618.10 is experienced if enoxaparin 40 mg daily for 4 days plus low-dose warfarin daily is administered versus enoxaparin 40 mg daily. Clinicians may choose to continue prophylaxis postdischarge with enoxaparin 40 mg daily for 4 days in combination with warfarin for 30 days in these patients until results of more definitive studies become available.

New antithrombotics for the intensive care unit setting: GP IIb/IIIa inhibitors, low-molecular-weight heparins, and direct thrombin inhibitors

Thromboembolic disease (TED) is a frequent problem encountered by clinicians in the intensive care unit (ICU). Traditionally, unfractionated heparin (UFH) has been used in the treatment and prophylaxis of TED. However, newer antithrombotic agents have evolved as effective alternatives to UFH. Low-molecular-weight heparins are effective for both the treatment and prophylaxis of TED. Lepirudin is useful for patients with TED and a history of heparin-induced thrombocytopenia. The platelet glycoprotein IIb/IIIa inhibitors are synergistic with UFH for the treatment of acute coronary syndromes and percutaneous coronary interventions (PCI). Several drugs are now available to clinicians for the treatment and prophylaxis of TED.

Cost-effectiveness of low-molecular-weight heparin in the treatment of proximal deep vein thrombosis

OBJECTIVE

To estimate the cost-effectiveness of low-molecular-weight heparin (LMWH) in the treatment of proximal lower extremity deep venous thrombosis.

DESIGN

Cost-effectiveness analysis that includes the treatment of the index case and simulated 3-month follow-up.

SETTING

Acute care facility.

PATIENTS AND PARTICIPANTS

Hypothetical cohorts of 1,000 patients who present with proximal deep venous thrombosis.

INTERVENTIONS

Intravenous unfractionated heparin (UH), LMWH (40% at home, 60% in hospital), or selective UH/LMWH (UH for hospitalized patients and LMWH for patients treated at home).

MEASUREMENTS AND MAIN RESULTS

The outcomes were recurrent thrombosis, mortality, direct medical costs, and marginal cost-effectiveness ratios from the payer's perspective. At the base-case and under most assumptions in the sensitivity analysis, the LMWH and the selective UH/LMWH strategies dominate the UH strategy i.e., they result in fewer cases of recurrent thrombosis and fewer deaths, and they save resources. The savings occur primarily by decreasing the length of stay. The LMWH strategy resulted in lower costs as compared with the UH strategy when the proportion of patients treated at home was more than 14%. Treating 1, 000 patients with the LMWH strategy as compared with the UH/LMWH strategy would result in 10 fewer cases of recurrent thrombosis, 1.2 fewer deaths, at an additional cost of $96,822; the cost-effectiveness ratio was $9,667 and $80,685 per recurrent thrombosis or death prevented, respectively.

CONCLUSIONS

Treatment with LMWH leads to savings and better outcomes as compared with UH in patients with lower extremity deep venous thrombosis. The selective UH/LMWH strategy is an alternative option.

Late occurring clinical deep vein thrombosis in joint-operated patients

In a prospective study of 4,840 patients, we determined the annual incidence of clinical deep vein thrombosis (DVT) in mobilized, discharged orthopedic-operated "high-risk" patients (hip replacement surgery, knee replacement surgery, nailed hip fracture) and assumed "low-risk" patients (diagnostic knee arthroscopy). In addition, the time from the operation to the time when the patients were readmitted with clinically suspected DVT and the distribution of radiologically-confirmed DVT were recorded. Thromboprophylaxis was routinely given for about 10 days to the high-risk groups during the hospital stay but not to patients undergoing knee arthroscopy. During 9 years, the annual incidence of DVT following major procedures was 2.1% (95% CI 1.6-2.6) vs. 0.6% (95% CI 0.2-1.1) after diagnostic knee arthroscopy. Symptoms appeared, on average, 27 (3-150) days after total hip replacement surgery, 36 (3-150) days after nailed hip fracture, 17 (6-30) days after total knee replacement and 1 (1-6) day after knee arthroscopy. In hip-operated patients, 50% of the DVTs were found in the proximal veins vs. 40% following knee arthroplasty.

Prevention of venous thromboembolism

Venous thromboembolism is the most common cause of preventable death among hospitalised patients. Systematic prophylaxis with antithrombotic agents in patients at risk for venous thromboembolism is the most effective approach to reduce morbidity and mortality. Despite this evidence, antithrombotic prophylaxis is still underused, due to the underestimation of incidence of venous thromboembolism and to the unjustified fear of bleeding complications. Both the characteristics of the individual patient and the clinical setting contribute to the definition of the risk for venous thromboembolism. Patient-related risk factors include clinical and molecular abnormalities. The grade of risk for venous thromboembolism is defined better by the clinical setting than by the patient characteristics. Prophylactic studies have been extensively carried out in surgical patients and, only more recently, in medical patients. Prophylactic methods include pharmacological agents, such as heparin, low molecular weight heparins, warfarin, and hirudin, as well as mechanical methods such as compression stockings and intermittent pneumatic compression.

Formulary management of low molecular weight heparins

Low molecular weight heparins (LMWHs) are increasingly being utilised as anticoagulants in healthcare settings. These agents offer several advantages over standard unfractionated heparin. Indications for LMWHs include deep vein thrombosis and pulmonary embolism prophylaxis, deep vein thrombosis treatment, use in coronary procedures associated with a high risk for bleeding, and in acute coronary syndromes. Prior to being added to formularies, LMWHs should be evaluated for efficacy, safety and economic benefits over other anticoagulants. Institutions should be prepared to conduct their own economic assessments in the absence of readily available studies. There is clear evidence that LMWHs are cost saving or are at least cost effective as thromboprophylactic agents in major orthopaedic surgery. The economic benefits of LMWHs in other surgical situations is less clear. Consistent evidence from several countries indicate that LMWHs are cost saving as anticoagulants for the initial treatment of DVT. Further studies are needed to evaluate the efficacy, safety and economics of LMWHs in other conditions besides hip and knee arthroplasty and general surgery.

Cost analyses of extended prophylaxis with enoxaparin after hip arthroplasty

Venous thromboembolic complications occur in 50% to 70% of patients undergoing total hip arthroplasty if no prophylactic regimen is used. Because enoxaparin and warfarin are useful for extended outpatient prophylaxis, the objective of this study was to determine which of these agents is most cost effective in preventing venous thromboembolic complications. A decision tree analysis was developed to simulate a hypothetical cohort of patients with total hip arthroplasty. The analysis considered home health care services to perform monitoring and compliance verification. Accounting for prophylactic failures and treatment complications, results showed that enoxaparin maintained a cost effective advantage over warfarin for extended prophylaxis in the time after discharge and total hip arthroplasty ranging from 19 to 31 days after the patient was discharged from the hospital. The duration of cost effectiveness of enoxaparin was reduced to 14 to 17 days when home care services were excluded. These results indicated that approximately 3 weeks of outpatient therapy with enoxaparin is cost effective. With the cornerstone of managed care being cost efficiency in the provision of quality care, this conclusion warrants the development of integrated care strategies for the patient having orthopaedic surgery to achieve cost effective patient management.

Advances in Therapy and the Management of Antithrombotic Drugs for Venous Thromboembolism

This review focuses on antithrombotic therapy for venous thromboembolism and covers a diverse range of topics including a discussion of emerging anticoagulant drugs, a renewed focus on thrombolytic agents for selected patients, and an analysis of the factors leading to adverse events in patients on warfarin, and how to optimize therapy. In Section I Dr. Weitz discusses new anticoagulant drugs focusing on those that are in the advanced stages of development. These will include drugs that (a) target factor VIIa/tissue factor, including tissue factor pathway inhibitor and NAPc2; (b) block factor Xa, including the synthetic pentasaccharide and DX9065a; (c) inhibit factors Va and VIIIa, i.e., activated protein C; and (d) block thrombin, including hirudin, argatroban, bivalirudin and H376/95. Oral formulations of heparin will also be reviewed.

In Section II, Dr. Comerota will discuss the use of thrombolysis for selected patients with venous thromboembolism. Fibrinolytic therapy, which has suffered from a high risk/benefit ratio for routine deep venous thrombosis, may have an important role to play in patients with iliofemoral venous thrombosis. Dr. Comerota presents his own results with catheter-directed thrombolytic therapy and the results from a large national registry showing long-term outcomes and the impact on quality of life.

In Section III, Dr. Ansell presents a critical analysis of the factors responsible for adverse events with oral anticoagulants and the optimum means of improving outcomes. The poor status of present day anticoagulant management is reviewed and the importance of achieving a high rate of “time in therapeutic range,” is emphasized. Models of care to optimize outcomes are described, with an emphasis on models that utilize patient self-testing and patient self-management of oral anticoagulation which are considered to be the ultimate in anticoagulation care. The treatment of venous and arterial thromboembolism is undergoing rapid change with respect to the development of new antithrombotic agents, an expanding list of new indications, and new methods of drug delivery and management. In spite of these changes, many of the traditional therapeutics are still with us and continue to play a vital role in the treatment of thromboembolic disease. The following discussion touches on a wide range of therapeutic interventions, from old to new, exploring the status of anticoagulant drug development, describing a new intervention for iliofemoral venous thrombosis, and analyzing the critical factors for safe and effective therapy with oral anticoagulants.

Advances in Therapy and the Management of Antithrombotic Drugs for Venous Thromboembolism

This review focuses on antithrombotic therapy for venous thromboembolism and covers a diverse range of topics including a discussion of emerging anticoagulant drugs, a renewed focus on thrombolytic agents for selected patients, and an analysis of the factors leading to adverse events in patients on warfarin, and how to optimize therapy. In Section I Dr. Weitz discusses new anticoagulant drugs focusing on those that are in the advanced stages of development. These will include drugs that (a) target factor VIIa/tissue factor, including tissue factor pathway inhibitor and NAPc2; (b) block factor Xa, including the synthetic pentasaccharide and DX9065a; (c) inhibit factors Va and VIIIa, i.e., activated protein C; and (d) block thrombin, including hirudin, argatroban, bivalirudin and H376/95. Oral formulations of heparin will also be reviewed.

In Section II, Dr. Comerota will discuss the use of thrombolysis for selected patients with venous thromboembolism. Fibrinolytic therapy, which has suffered from a high risk/benefit ratio for routine deep venous thrombosis, may have an important role to play in patients with iliofemoral venous thrombosis. Dr. Comerota presents his own results with catheter-directed thrombolytic therapy and the results from a large national registry showing long-term outcomes and the impact on quality of life.

In Section III, Dr. Ansell presents a critical analysis of the factors responsible for adverse events with oral anticoagulants and the optimum means of improving outcomes. The poor status of present day anticoagulant management is reviewed and the importance of achieving a high rate of “time in therapeutic range,” is emphasized. Models of care to optimize outcomes are described, with an emphasis on models that utilize patient self-testing and patient self-management of oral anticoagulation which are considered to be the ultimate in anticoagulation care. The treatment of venous and arterial thromboembolism is undergoing rapid change with respect to the development of new antithrombotic agents, an expanding list of new indications, and new methods of drug delivery and management. In spite of these changes, many of the traditional therapeutics are still with us and continue to play a vital role in the treatment of thromboembolic disease. The following discussion touches on a wide range of therapeutic interventions, from old to new, exploring the status of anticoagulant drug development, describing a new intervention for iliofemoral venous thrombosis, and analyzing the critical factors for safe and effective therapy with oral anticoagulants.

Heparin, low molecular weight heparin and physical methods for preventing deep vein thrombosis and pulmonary embolism following surgery for hip fractures

BACKGROUND

Hip fracture patients have a high risk of thromboembolic complications following surgical management.

OBJECTIVES

To examine the effects of heparin (unfractionated (U), and low molecular weight (LMW) heparins), and physical methods (compression stockings, calf or foot pumps) for prevention of deep venous thrombosis (DVT) and pulmonary embolism after surgery for hip fracture in the elderly.

SEARCH STRATEGY

We searched the Cochrane Musculoskeletal Injuries Group trials register, Medline, Embase, and reference lists of published papers and books. We contacted trialists and other workers in the field. Date of most recent search: September 1996.

SELECTION CRITERIA

Randomised and quasi-randomised trials evaluating the use of heparins and physical agents for prevention of DVT and pulmonary embolism in patients undergoing surgery for hip fracture.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed methodological quality and extracted data. Trials were grouped into four categories (heparin versus control, mechanical versus control, LMW heparin versus U heparin, and miscellaneous) and results pooled where possible.

MAIN RESULTS

The 26 included trials involved 2600 predominantly female and elderly patients. Overall, trial quality was disappointing. Ten trials involving 826 patients which compared U heparin with control, and four trials of 471 patients which compared LMW heparin with control, showed a reduction in the incidence of lower limb DVT (121/511 (24%) versus 203/519 (39%); Peto odds ratio 0.41; 95% confidence interval 0.31 to 0.55). There were insufficient data to confirm the efficacy of either agent in the prevention of pulmonary embolism. There was a non significant increase in overall mortality in the heparin group (46/420 (11%) versus 35/423 (8%); Peto odds ratio 1.39; 95% confidence interval 0. 86 to 2.23). Data were inadequate for all other outcomes including wound complications. There is insufficient evidence from five trials, involving 644 patients, to establish if LMW heparin was superior to U heparin. Most trials evaluating heparins had methodological defects. Four trials, involving 442 patients, testing mechanical pumping devices were also methodologically flawed, and so pooled results need to be viewed cautiously. Mechanical pumping devices may protect against DVT (12/202 (6%) versus 42/212 (19%); Peto odds ratio 0.24; 95% confidence interval 0.13 to 0.44). Although the limited data indicated a potential benefit, they were inadequate to establish any effect on the incidence of pulmonary embolism and overall mortality. Problems with skin abrasion and compliance were reported.

REVIEWER'S CONCLUSIONS

U and LMW heparins protect against lower limb DVT. There is insufficient evidence to confirm either protection against pulmonary embolism or overall benefit, or to distinguish between various applications of heparin. Foot and calf pumping devices appear to prevent DVT, may protect against pulmonary embolism, and reduce mortality, but compliance remains a problem. Good quality trials of mechanical methods as well as direct comparisons with heparin should be considered.

Extended prophylaxis against venous thromboembolism following total hip and knee replacement

The recently reported reductions in the incidence of post-operative venous thromboembolism (VTE) are related to the widespread use of prophylactic anticoagulants. Many uncertainties remain with regard to the most effective ways to use thromboprophylaxis, however. The trend towards shorter hospital stays means that patients may receive less than the recommended 7-10 days of prophylaxis. Prolonged periods of thromboprophylaxis may be beneficial for patients at high risk of post-operative VTE, such as those undergoing major orthopaedic surgery. The relative rarity of symptomatic deep vein thrombosis and pulmonary embolism means that very large patient populations are required for studies that rely on clinical endpoints, but studies using venographic endpoints have shown 28-35 days of prophylaxis with low-molecular-weight heparin to be more effective than 10-14 days. Other factors that may influence the efficacy of thromboprophylaxis include the timing of the first injection and the choice of agent.

The influence of oral anticoagulation therapy on deep vein thrombosis rates four weeks after total hip replacement

PURPOSE

The purpose of this study was to assess the rate of postoperative deep vein thrombosis (DVT) as a function of oral anticoagulation therapy after total hip replacement surgery.

METHODS

A total of 125 patients completed the study. All the patients received sequential gradient pneumatic compression over elastic stockings until hospital discharge. In addition, all the patients underwent postoperative heparin therapy followed by oral warfarin therapy, adjusted in dose to maintain a goal international normalized ratio (INR) level of 2.0 to 3.0. Warfarin therapy and compression stockings were continued for 1 month after surgery. Bilateral duplex scanning was performed 1 and 4 weeks after surgery to assess the rate of DVT.

RESULTS

Nineteen of the 125 patients had DVT develop (15.2%). Of those thromboses, six (31.6%) and 13 (68%) were detected 1 week and 1 month after surgery, respectively. The rate of proximal DVT was 2.4% (3 of 125) 1 week after surgery and rose to 8.2% (10 of 122) 1 month after surgery. Most DVT cases (64%; 12 of 19) were asymptomatic. The patients in whom DVT developed had significantly lower INR values during the second to fourth postoperative weeks than did those patients without thrombosis, and no differences in INR values were found during the first postoperative week.

CONCLUSION

The risk of the development of DVT extends beyond hospital discharge in patients who undergo total hip replacement, despite a regimen of prolonged oral anticoagulation therapy. This is particularly true in patients whose INR values did not reach therapeutic range during the first postoperative month. Therefore, thrombosis prophylaxis regimens on the basis of the administration of warfarin should try to maintain INR values within therapeutic range during the entire first postoperative month to minimize the incidence of DVT.