Treatment of acute venous thromboembolism with low molecular weight heparin (Fragmin). Results of a double-blind randomized study

Anticoagulation for the initial treatment of venous thromboembolism in people with cancer

BACKGROUND

Compared with people without cancer, people with cancer who receive anticoagulant treatment for venous thromboembolism (VTE) are more likely to develop recurrent VTE.

OBJECTIVES

To compare the efficacy and safety of three types of parenteral anticoagulants (i.e. fixed-dose low molecular weight heparin (LMWH), adjusted-dose unfractionated heparin (UFH), and fondaparinux) for the initial treatment of VTE in people with cancer.

SEARCH METHODS

We performed a comprehensive search in the following major databases: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (via Ovid) and Embase (via Ovid). We also handsearched conference proceedings, checked references of included studies, and searched for ongoing studies. This update of the systematic review is based on the findings of a literature search conducted on 14 August 2021.

SELECTION CRITERIA

Randomised controlled trials (RCTs) assessing the benefits and harms of LMWH, UFH, and fondaparinux in people with cancer and objectively confirmed VTE.

DATA COLLECTION AND ANALYSIS

Using a standardised form, we extracted data - in duplicate - on study design, participants, interventions, outcomes of interest, and risk of bias. Outcomes of interest included all-cause mortality, symptomatic VTE, major bleeding, minor bleeding, postphlebitic syndrome, quality of life, and thrombocytopenia. We assessed the certainty of evidence for each outcome using the GRADE approach.

MAIN RESULTS

Of 11,484 identified citations, 3073 were unique citations and 15 RCTs fulfilled the eligibility criteria, none of which were identified in the latest search. These trials enrolled 1615 participants with cancer and VTE: 13 compared LMWH with UFH; one compared fondaparinux with UFH and LMWH; and one compared dalteparin with tinzaparin, two different types of low molecular weight heparin. The meta-analyses showed that LMWH may reduce mortality at three months compared to UFH (risk ratio (RR) 0.66, 95% confidence interval (CI) 0.40 to 1.10; risk difference (RD) 57 fewer per 1000, 95% CI 101 fewer to 17 more; low certainty evidence) and may reduce VTE recurrence slightly (RR 0.69, 95% CI 0.27 to 1.76; RD 30 fewer per 1000, 95% CI 70 fewer to 73 more; low certainty evidence). There were no data available for bleeding outcomes, postphlebitic syndrome, quality of life, or thrombocytopenia. The study comparing fondaparinux with heparin (UFH or LMWH) found that fondaparinux may increase mortality at three months (RR 1.25, 95% CI 0.86 to 1.81; RD 43 more per 1000, 95% CI 24 fewer to 139 more; low certainty evidence), may result in little to no difference in recurrent VTE (RR 0.93, 95% CI 0.56 to 1.54; RD 8 fewer per 1000, 95% CI 52 fewer to 63 more; low certainty evidence), may result in little to no difference in major bleeding (RR 0.82, 95% CI 0.40 to 1.66; RD 12 fewer per 1000, 95% CI 40 fewer to 44 more; low certainty evidence), and probably increases minor bleeding (RR 1.53, 95% CI 0.88 to 2.66; RD 42 more per 1000, 95% CI 10 fewer to 132 more; moderate certainty evidence). There were no data available for postphlebitic syndrome, quality of life, or thrombocytopenia. The study comparing dalteparin with tinzaparin found that dalteparin may reduce mortality slightly (RR 0.86, 95% CI 0.43 to 1.73; RD 33 fewer per 1000, 95% CI 135 fewer to 173 more; low certainty evidence), may reduce recurrent VTE (RR 0.44, 95% CI 0.09 to 2.16; RD 47 fewer per 1000, 95% CI 77 fewer to 98 more; low certainty evidence), may increase major bleeding slightly (RR 2.19, 95% CI 0.20 to 23.42; RD 20 more per 1000, 95% CI 14 fewer to 380 more; low certainty evidence), and may reduce minor bleeding slightly (RR 0.82, 95% CI 0.30 to 2.21; RD 24 fewer per 1000, 95% CI 95 fewer to 164 more; low certainty evidence). There were no data available for postphlebitic syndrome, quality of life, or thrombocytopenia.

AUTHORS' CONCLUSIONS

Low molecular weight heparin (LMWH) is probably superior to UFH in the initial treatment of VTE in people with cancer. Additional trials focusing on patient-important outcomes will further inform the questions addressed in this review. The decision for a person with cancer to start LMWH therapy should balance the benefits and harms and consider the person's values and preferences.

Anticoagulation for the initial treatment of venous thromboembolism in people with cancer

BACKGROUND

Compared with people without cancer, people with cancer who receive anticoagulant treatment for venous thromboembolism (VTE) are more likely to develop recurrent VTE.

OBJECTIVES

To compare the efficacy and safety of three types of parenteral anticoagulants (i.e. fixed-dose low molecular weight heparin (LMWH), adjusted-dose unfractionated heparin (UFH), and fondaparinux) for the initial treatment of VTE in people with cancer.

SEARCH METHODS

A comprehensive search included a major electronic search of the following databases: Cochrane Central Register of Controlled Trials (CENTRAL) (2018, Issue 1), MEDLINE (via Ovid) and Embase (via Ovid); handsearching of conference proceedings; checking of references of included studies; use of the 'related citation' feature in PubMed; and a search for ongoing studies. This update of the systematic review was based on the findings of a literature search conducted on 14 January 2018.

SELECTION CRITERIA

Randomized controlled trials (RCTs) assessing the benefits and harms of LMWH, UFH, and fondaparinux in people with cancer and objectively confirmed VTE.

DATA COLLECTION AND ANALYSIS

Using a standardized form, we extracted data in duplicate on study design, participants, interventions outcomes of interest, and risk of bias. Outcomes of interested included all-cause mortality, symptomatic VTE, major bleeding, minor bleeding, postphlebitic syndrome, quality of life, and thrombocytopenia. We assessed the certainty of evidence for each outcome using the GRADE approach.

MAIN RESULTS

Of 15440 identified citations, 7387 unique citations, 15 RCTs fulfilled the eligibility criteria. These trials enrolled 1615 participants with cancer and VTE: 13 compared LMWH with UFH enrolling 1025 participants, one compared fondaparinux with UFH and LMWH enrolling 477 participants, and one compared dalteparin with tinzaparin enrolling 113 participants. The meta-analysis of mortality at three months included 418 participants from five studies and that of recurrent VTE included 422 participants from 3 studies. The findings showed that LMWH likely decreases mortality at three months compared to UFH (risk ratio (RR) 0.66, 95% confidence interval (CI) 0.40 to 1.10; risk difference (RD) 57 fewer per 1000, 95% CI 101 fewer to 17 more; moderate certainty evidence), but did not rule out a clinically significant increase or decrease in VTE recurrence (RR 0.69, 95% CI 0.27 to 1.76; RD 30 fewer per 1000, 95% CI 70 fewer to 73 more; moderate certainty evidence).The study comparing fondaparinux with heparin (UFH or LMWH) did not exclude a beneficial or detrimental effect of fondaparinux on mortality at three months (RR 1.25, 95% CI 0.86 to 1.81; RD 43 more per 1000, 95% CI 24 fewer to 139 more; moderate certainty evidence), recurrent VTE (RR 0.93, 95% CI 0.56 to 1.54; RD 8 fewer per 1000, 95% CI 52 fewer to 63 more; moderate certainty evidence), major bleeding (RR 0.82, 95% CI 0.40 to 1.66; RD 12 fewer per 1000, 95% CI 40 fewer to 44 more; moderate certainty evidence), or minor bleeding (RR 1.53, 95% CI 0.88 to 2.66; RD 42 more per 1000, 95% CI 10 fewer to 132 more; moderate certainty evidence)The study comparing dalteparin with tinzaparin did not exclude a beneficial or detrimental effect of dalteparin on mortality (RR 0.86, 95% CI 0.43 to 1.73; RD 33 fewer per 1000, 95% CI 135 fewer to 173 more; low certainty evidence), recurrent VTE (RR 0.44, 95% CI 0.09 to 2.16; RD 47 fewer per 1000, 95% CI 77 fewer to 98 more; low certainty evidence), major bleeding (RR 2.19, 95% CI 0.20 to 23.42; RD 20 more per 1000, 95% CI 14 fewer to 380 more; low certainty evidence), or minor bleeding (RR 0.82, 95% CI 0.30 to 2.21; RD 24 fewer per 1000, 95% CI 95 fewer to 164 more; low certainty evidence).

AUTHORS' CONCLUSIONS

LMWH is possibly superior to UFH in the initial treatment of VTE in people with cancer. Additional trials focusing on patient-important outcomes will further inform the questions addressed in this review. The decision for a person with cancer to start LMWH therapy should balance the benefits and harms and consider the person's values and preferences.

Fixed dose subcutaneous low molecular weight heparins versus adjusted dose unfractionated heparin for the initial treatment of venous thromboembolism

BACKGROUND

Low molecular weight heparins (LMWHs) have been shown to be effective and safe in preventing venous thromboembolism (VTE). They may also be effective for the initial treatment of VTE. This is the third update of the Cochrane Review first published in 1999.

OBJECTIVES

To evaluate the efficacy and safety of fixed dose subcutaneous low molecular weight heparin compared to adjusted dose unfractionated heparin (intravenous or subcutaneous) for the initial treatment of people with venous thromboembolism (acute deep venous thrombosis or pulmonary embolism).

SEARCH METHODS

For this update the Cochrane Vascular Information Specialist (CIS) searched the Cochrane Vascular Specialised Register (15 September 2016). In addition the CIS searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 8) in the Cochrane Library (searched 15 September 2016) and trials' registries.

SELECTION CRITERIA

Randomised controlled trials comparing fixed dose subcutaneous LMWH with adjusted dose intravenous or subcutaneous unfractionated heparin (UFH) in people with VTE.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, assessed for quality and extracted data.

MAIN RESULTS

Six studies were added to this update resulting in a total of 29 included studies (n = 10,390). The quality of the studies was downgraded as there was a risk of bias in some individual studies relating to risk of attrition and reporting bias; in addition several studies did not adequately report on the randomisation methods used nor on how the treatment allocation was concealed.During the initial treatment period, the incidence of recurrent venous thromboembolic events was lower in participants treated with LMWH than in participants treated with UFH (Peto odds ratio (OR) 0.69, 95% confidence intervals (CI) 0.49 to 0.98; 6238 participants; 18 studies; P = 0.04; moderate-quality evidence). After a follow-up of three months, the period in most of the studies for which oral anticoagulant therapy was given, the incidence of recurrent VTE was lower in participants treated with LMWH than in participants with UFH (Peto OR 0.71, 95% CI 0.56 to 0.90; 6661 participants; 16 studies; P = 0.005; moderate-quality evidence). Furthermore, at the end of follow-up, LMWH was associated with a lower rate of recurrent VTE than UFH (Peto OR 0.72, 95% CI 0.59 to 0.88; 9489 participants; 22 studies; P = 0.001; moderate-quality evidence). LMWH was also associated with a reduction in thrombus size compared to UFH (Peto OR 0.71, 95% CI 0.61 to 0.82; 2909 participants; 16 studies; P < 0.00001; low-quality evidence), but there was moderate heterogeneity (I² = 56%). Major haemorrhages occurred less frequently in participants treated with LMWH than in those treated with UFH (Peto OR 0.69, 95% CI 0.50 to 0.95; 8780 participants; 25 studies; P = 0.02; moderate-quality evidence). There was no difference in overall mortality between participants treated with LMWH and those treated with UFH (Peto OR 0.84, 95% CI 0.70 to 1.01; 9663 participants; 24 studies; P = 0.07; moderate-quality evidence).

AUTHORS' CONCLUSIONS

This review presents moderate-quality evidence that fixed dose LMWH reduced the incidence of recurrent thrombotic complications and occurrence of major haemorrhage during initial treatment; and low-quality evidence that fixed dose LMWH reduced thrombus size when compared to UFH for the initial treatment of VTE. There was no difference in overall mortality between participants treated with LMWH and those treated with UFH (moderate-quality evidence). The quality of the evidence was assessed using GRADE criteria and downgraded due to concerns over risk of bias in individual trials together with a lack of reporting on the randomisation and concealment of treatment allocation methods used. The quality of the evidence for reduction of thrombus size was further downgraded because of heterogeneity between studies.

Low-Molecular-Weight Heparin for the Treatment of Venous Thromboembolism in the Elderly

Venous thromboembolism (deep vein thrombosis and/or pulmonary embolism) is a common problem in the elderly population. Indeed, increasing age is a significant risk factor for venous thromboembolism. The treatment of venous thromboembolism in the elderly population presents certain unique problems related to aging, such as decreasing body weight, increasing renal insufficiency and numerous comorbid conditions, which complicate therapy. Treatment of venous thromboembolism in the elderly has been complicated by an increased incidence of bleeding, particularly with the use of warfarin. The risk of bleeding may be substantially reduced by carefully adjusting the warfarin dose to maintain a therapeutic INR and for this purpose anticoagulant management clinics have been shown to be useful. The low-molecular-weight heparins have been shown to be efficacious and safe for the treatment of venous thromboembolism in several clinical trials, including many patients in the older age brackets. Furthermore, these agents can safely be used in the out-of-hospital setting. Long-term use of low-molecular-weight heparin is an alternative to the use of oral anticoagulant therapy, particularly in patients with cancer or recurrent venous thromboembolism.

The Treatment of Proximal Vein Thrombosis with Subcutaneous Low-Mole Molecular-Weight Heparin Compared with Continuous Intravenous Heparin

Low-molecular-weight heparin, compared with unfractionated heparin, has a higher bioavailability and a more prolonged half-life. There are limited data comparing the use of low-molecular-weight heparin with unfractionated heparin for the treatment of deep vein thrombosis. We have compared fixed-dose, subcutaneous low-molecular-weight heparin given once daily with adjusted-dose intravenous heparin given by continuous infusion in a multicenter double-blind clinical trial for the initial treatment of patients with proximal vein thrombosis. Clinical outcomes were objectively documented. Six of 213 patients receiving low-molecular-weight heparin (2.8%) and 15 of 219 patients receiving intravenous heparin (6.9%) developed new episodes of venous thromboembolism (p = 0.07; 95% confidence interval for the difference, 0.02%-8.1%). During initial therapy, major bleeding occurred in one patient receiving low-molecular-weight heparin (0.5%) and in 11 patients receiving intravenous heparin (5.0%), a risk reduction of 91% (p = 0.006). This apparent protection against major bleeding was lost during long-term therapy. Minor bleeding complications were rare. During the period of the study, 10 patients receiving low-molecular-weight heparin (4.7%) died, as compared with 21 patients receiving intravenous heparin (9.6%), a risk reduction of 51%(p = 0.049). This study shows that low-molecular-weight heparin is at least as effective as classic intravenous heparin therapy and that there was a reduction in deaths and bleeding complications. Furthermore, low-molecular-weight heparin was more convenient to administer. The simplified therapy with low-molecular-weight heparin given by once-daily subcutaneous injection without monitoring may allow patients with uncomplicated proximal deep vein thrombosis to be cared for as outpatients. Key Words: Low-molecular-weight heparin—Unfractionated heparin—Deep vein thrombosis—Deaths—Bleeding complications.

Guidance for the practical management of the heparin anticoagulants in the treatment of venous thromboembolism

Venous thromboembolism (VTE) is a serious and often fatal medical condition with an increasing incidence. Despite the changing landscape of VTE treatment with the introduction of the new direct oral anticoagulants many uncertainties remain regarding the optimal use of traditional parenteral agents. This manuscript, initiated by the Anticoagulation Forum, provides clinical guidance based on existing guidelines and consensus expert opinion where guidelines are lacking. This specific chapter addresses the practical management of heparins including low molecular weight heparins and fondaparinux. For each anticoagulant a list of the most common practice related questions were created. Each question was addressed using a brief focused literature review followed by a multidisciplinary consensus guidance recommendation. Issues addressed included initial anticoagulant dosing recommendations, recommended baseline laboratory monitoring, managing dose adjustments, evidence to support a relationship between laboratory tests and meaningful clinical outcomes, special patient populations including extremes of weight and renal impairment, duration of necessary parenteral therapy during the transition to oral therapy, candidates for outpatient treatment where appropriate and management of over-anticoagulation and adverse effects including bleeding and heparin induced thrombocytopenia. This article concludes with a concise table of clinical management questions and guidance recommendations to provide a quick reference for the practical management of heparin, low molecular weight heparin and fondaparinux.

Treatment of deep vein thrombosis in patients with pulmonary embolism: subgroup analysis on the efficacy and safety of certoparin vs. unfractionated heparin

The objective of this subgroup analysis of the pivotal studies NMH-TH-3 and NMH-TH-4 was to investigate the incidence of recurrent events of venous thromboembolism in patients with acute deep vein thrombosis (DVT) with and without pulmonary embolism treated with subcutaneous fixed-dose low-molecular-weight heparin certoparin or intravenous unfractionated heparin (UFH). To assess whether the efficacy of the two treatments is modified by the presence or absence of pulmonary embolism, a P value for subgroup by treatment interaction was calculated using logistic regression. The rate of recurrent venous thromboembolic events, defined as DVT, pulmonary embolism and death due to pulmonary embolism, was observed over 6 months. After 6 months of follow-up, 6.58% of patients with pulmonary embolism at baseline treated with certoparin (5/76) compared with 11.5% of patients with pulmonary embolism at baseline treated with UFH (7/61) had a venous thromboembolic event [relative risk (RR) = 0.57, confidence interval (CI) = 0.19-1.72]. In the group of patients without pulmonary embolism at baseline, 2.82% of patients treated with certoparin (23/816) and 4.63% of patients treated with UFH (37/800) had a venous thromboembolic event (RR = 0.61, CI = 0.37-1.02). The test for interaction between the groups of patients with and without pulmonary embolism was not significant (P = 0.886). The same was true for the safety results with regard to major bleedings and death. These data suggest that the recommendation for the use of certoparin in the treatment of isolated DVT can safely be extended to treatment of DVT in patients concomitantly suffering from pulmonary embolism.

Secular trends in occurrence of acute venous thromboembolism: the Worcester VTE study (1985-2009)

BACKGROUND

The clinical epidemiology of venous thromboembolism has changed recently because of advances in identification, prophylaxis, and treatment. We sought to describe secular trends in the occurrence of venous thromboembolism among residents of the Worcester, Massachusetts, metropolitan statistical area.

METHODS

Population-based methods were used to monitor trends in event rates of first-time or recurrent venous thromboembolism in 5025 Worcester, Massachusetts, metropolitan statistical area residents who were diagnosed with acute pulmonary embolism or lower-extremity deep vein thrombosis during 9 annual periods between 1985 and 2009. Medical records were reviewed by abstractors and validated by clinicians.

RESULTS

Age- and sex-adjusted annual event rates for first-time venous thromboembolism increased from 73 (95% confidence interval [CI], 64-82) per 100,000 in 1985/1986 to 133 (CI, 122-143) in 2009, primarily because of an increase in pulmonary embolism. The rate of recurrent venous thromboembolism decreased from 39 (CI, 32-45) in 1985/1986 to 19 (CI, 15-23) in 2003, and then increased to 35 (CI, 29-40) in 2009. There was an increasing trend in using noninvasive diagnostic testing, with approximately half of tests being invasive in 1985/1986 and almost all noninvasive by 2009.

CONCLUSIONS

Despite advances in identification, prophylaxis, and treatment between 1985 and 2009, the annual event rate of venous thromboembolism has increased and remains high. Although these increases partially may be due to increased sensitivity of diagnostic methods, especially for pulmonary embolism, they also may imply that current prevention and treatment strategies are less than optimal.

Anticoagulation for the initial treatment of venous thromboembolism in patients with cancer

BACKGROUND

Compared with patients without cancer, patients with cancer who receive anticoagulant treatment for venous thromboembolism (VTE) are more likely to develop recurrent VTE.

OBJECTIVES

To compare the efficacy and safety of three types of parenteral anticoagulants (i.e. fixed-dose low molecular weight heparin (LMWH), adjusted-dose unfractionated heparin (UFH), and fondaparinux) for the initial treatment of VTE in patients with cancer.

SEARCH METHODS

A comprehensive search for studies of anticoagulation in patients with cancer including a February 2013 electronic search of: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, and ISI Web of Science.

SELECTION CRITERIA

Randomized clinical trials (RCTs) comparing LMWH, UFH, and fondaparinux in patients with cancer and objectively confirmed VTE.

DATA COLLECTION AND ANALYSIS

Using a standardized data form, review authors extracted data in duplicate on methodologic quality, participants, interventions, and outcomes of interest that included mortality, recurrent VTE, major bleeding, minor bleeding, postphlebitic syndrome, quality of life, and thrombocytopenia.

MAIN RESULTS

Of 9559 identified citations, 16 RCTs were eligible: 13 compared LMWH with UFH, two compared fondaparinux with heparin, and one compared dalteparin with tinzaparin. Meta-analysis of 11 studies showed a statistically significant reduction in mortality at three months of follow-up with LMWH compared with UFH (risk ratio (RR) 0.71; 95% confidence interval (CI) 0.52 to 0.98). There was little change in the effect estimate after excluding studies of lower methodologic quality (RR 0.72; 95% CI 0.52 to 1.00). A meta-analysis of three studies comparing LMWH with UFH showed no statistically significant reduction in VTE recurrence (RR 0.78; 95% CI 0.29 to 2.08). The overall quality of evidence was low for LMWH versus UFH due to imprecision and likely publication bias. There were no statistically significant differences between heparin and fondaparinux for the outcomes of mortality (RR 1.27; 95% CI 0.88 to 1.84), recurrent VTE (RR 0.95; 95% CI 0.57 to 1.60), major bleeding (RR 0.79; 95% CI 0.39 to1.63), or minor bleeding (RR 1.50; 95% CI 0.87 to 2.59). The one study comparing dalteparin with tinzaparin found no statistically significant difference in mortality (RR 0.86; 95% CI 0.43 to 1.73).

AUTHORS' CONCLUSIONS

LMWH is possibly superior to UFH in the initial treatment of VTE in patients with cancer. Additional trials focusing on patient-important outcomes will further inform the questions addressed in this review.

Clinical and health costs impact of progress in diagnosis and treatment in venous thromboembolic disease: evolution in 15 years

BACKGROUND

The therapeutic and diagnostic approach in deep vein thrombosis (DVT) has changed enormously in the last two decades with the introduction of ultrasound, low-molecular-weight heparin (LMWH), and premature motion. The aim of this study is to evaluate these changes and analyze their clinical and economic aspects.

METHODS

We registered all inpatients with a diagnosis of DVT during 1994 (n=110) and 2009 (n=75) and their sociodemographic and clinical features in a descriptive observational design. We performed a comparison of diagnostic techniques, length of stay, inpatient complications, and costs thus derived for both series, based on 2009 prices, so that we could get comparable results.

RESULTS

Ninety-one percent of inpatients in 1994 were diagnosed by venography, whereas, in 2009, the diagnosis was based on clinical features, D-dimer, and ultrasound in 100% of patients. Inpatient treatment went from 7% LMWH in 1994 to 96% in 2009, and as outpatient from 82% acenocumarol to 90.6% LMWH. Complications decreased by 13.3%. Length of stay was 2.7 higher in 1994. Globally, the cost per patient decreased by 63.39%, based primarily on reduced length of stay.

CONCLUSIONS

The current diagnostic and therapeutic approach in DVT allows for effective treatment, fewer complications, and a drastic reduction in inpatient costs.

Anticoagulation for the initial treatment of venous thromboembolism in patients with cancer

BACKGROUND

Compared to patients without cancer, patients with cancer who receive anticoagulant treatment for venous thromboembolism are more likely to develop recurrent venous thromboembolism (VTE).

OBJECTIVES

To compare the efficacy and safety of three types of parenteral anticoagulants for the initial treatment of VTE in patients with cancer.

SEARCH STRATEGY

A comprehensive search for studies of anticoagulation in cancer patients including a February 2010 electronic search of: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and ISI Web of Science.

SELECTION CRITERIA

Randomized clinical trials (RCTs) comparing low molecular weight heparin (LMWH), unfractionated heparin (UFH), and fondaparinux in patients with cancer and objectively confirmed VTE.

DATA COLLECTION AND ANALYSIS

Using a standardized data form, data was extracted in duplicate on methodological quality, participants, interventions, and outcomes of interest that included mortality, recurrent VTE, major bleeding, minor bleeding, postphlebitic syndrome, quality of life, and thrombocytopenia.

MAIN RESULTS

Of 3986 identified citations, 16 RCTs were eligible: 13 compared LMWH to UFH, two compared fondaparinux to heparin, and one compared dalteparin to tinzaparin. Meta-analysis of 11 studies showed a statistically significant reduction in mortality at three months of follow up with LMWH compared with UFH (relative risk (RR) 0.71; 95% confidence interval (CI) 0.52 to 0.98). There was little change in the effect estimate after excluding studies of lower methodological quality (RR 0.72; 95% CI 0.52 to 1.00). A meta-analysis of three studies comparing LMWH with UFH showed no statistically significant reduction in VTE recurrence (RR 0.78; 95% CI 0.29 to 2.08). The overall quality of evidence was low for LMWH versus UFH due to imprecision and likely publication bias. There were no statistically significant differences between heparin and fondaparinux for the outcomes of death (RR 1.27; 95% CI 0.88 to 1.84), recurrent VTE (RR 0.95; 95% CI 0.57 to 1.60), major bleeding (RR 0.79; 95% CI 0.39 to1.63) or minor bleeding (RR 1.50; 95% CI 0.87 to 2.59). The one study comparing dalteparin to tinzaparin did not find a statistically significant difference in mortality (RR 0.86; 95% CI 0.43 to 1.73).

AUTHORS' CONCLUSIONS

LMWH is possibly superior to UFH in the initial treatment of VTE in patients with cancer. Additional trials focusing on patient important outcomes will further inform the questions addressed in this review.

Anticoagulation for the initial treatment of venous thromboembolism in patients with cancer

BACKGROUND

Compared to patients without cancer, patients with cancer who receive anticoagulant treatment for venous thromboembolism are more likely to develop recurrent venous thromboembolism (VTE).

OBJECTIVES

To compare the efficacy and safety of three types of parenteral anticoagulants for the initial treatment of VTE in patients with cancer.

SEARCH STRATEGY

A comprehensive search for studies of anticoagulation in cancer patients including a February 2010 electronic search of: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and ISI Web of Science.

SELECTION CRITERIA

Randomized clinical trials (RCTs) comparing low molecular weight heparin (LMWH), unfractionated heparin (UFH), and fondaparinux in patients with cancer and objectively confirmed VTE.

DATA COLLECTION AND ANALYSIS

Using a standardized data form, data was extracted in duplicate on methodological quality, participants, interventions, and outcomes of interest that included mortality, recurrent VTE, major bleeding, minor bleeding, postphlebitic syndrome, quality of life, and thrombocytopenia.

MAIN RESULTS

Of 3986 identified citations, 16 RCTs were eligible: 13 compared LMWH to UFH, two compared fondaparinux to heparin, and one compared dalteparin to tinzaparin. Meta-analysis of 11 studies showed a statistically significant reduction in mortality at three months of follow up with LMWH compared with UFH (relative risk (RR) 0.71; 95% confidence interval (CI) 0.52 to 0.98). There was little change in the effect estimate after excluding studies of lower methodological quality (RR 0.72; 95% CI 0.52 to 1.00). A meta-analysis of three studies comparing LMWH with UFH showed no statistically significant reduction in VTE recurrence (RR 0.78; 95% CI 0.29 to 2.08). The overall quality of evidence was low for LMWH versus UFH due to imprecision and likely publication bias. There were no statistically significant differences between heparin and fondaparinux for the outcomes of death (RR 1.27; 95% CI 0.88 to 1.84), recurrent VTE (RR 0.95; 95% CI 0.57 to 1.60), major bleeding (RR 0.79; 95% CI 0.39 to1.63) or minor bleeding (RR 1.50; 95% CI 0.87 to 2.59). The one study comparing dalteparin to tinzaparin did not find a statistically significant difference in mortality (RR 0.86; 95% CI 0.43 to 1.73).

AUTHORS' CONCLUSIONS

LMWH is possibly superior to UFH in the initial treatment of VTE in patients with cancer. Additional trials focusing on patient important outcomes will further inform the questions addressed in this review.

Anticoagulation for the initial treatment of venous thromboembolism in patients with cancer

BACKGROUND

Compared to patients without cancer, patients with cancer who receive anticoagulant treatment for venous thromboembolism are more likely to develop recurrent venous thromboembolism (VTE).

OBJECTIVES

To compare the efficacy and safety of three types of parenteral anticoagulants for the initial treatment of VTE in patients with cancer.

SEARCH STRATEGY

A comprehensive search for studies of anticoagulation in cancer patients including a February 2010 electronic search of: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and ISI Web of Science.

SELECTION CRITERIA

Randomized clinical trials (RCTs) comparing low molecular weight heparin (LMWH), unfractionated heparin (UFH), and fondaparinux in patients with cancer and objectively confirmed VTE.

DATA COLLECTION AND ANALYSIS

Using a standardized data form, data was extracted in duplicate on methodological quality, participants, interventions, and outcomes of interest that included mortality, recurrent VTE, major bleeding, minor bleeding, postphlebitic syndrome, quality of life, and thrombocytopenia.

MAIN RESULTS

Of 3986 identified citations, 16 RCTs were eligible: 13 compared LMWH to UFH, two compared fondaparinux to heparin, and one compared dalteparin to tinzaparin. Meta-analysis of 11 studies showed a statistically significant reduction in mortality at three months of follow up with LMWH compared with UFH (relative risk (RR) 0.71; 95% confidence interval (CI) 0.52 to 0.98). There was little change in the effect estimate after excluding studies of lower methodological quality (RR 0.72; 95% CI 0.52 to 1.00). A meta-analysis of three studies comparing LMWH with UFH showed no statistically significant reduction in VTE recurrence (RR 0.78; 95% CI 0.29 to 2.08). The overall quality of evidence was low for LMWH versus UFH due to imprecision and likely publication bias. There were no statistically significant differences between heparin and fondaparinux for the outcomes of death (RR 1.27; 95% CI 0.88 to 1.84), recurrent VTE (RR 0.95; 95% CI 0.57 to 1.60), major bleeding (RR 0.79; 95% CI 0.39 to1.63) or minor bleeding (RR 1.50; 95% CI 0.87 to 2.59). The one study comparing dalteparin to tinzaparin did not find a statistically significant difference in mortality (RR 0.86; 95% CI 0.43 to 1.73).

AUTHORS' CONCLUSIONS

LMWH is possibly superior to UFH in the initial treatment of VTE in patients with cancer. Additional trials focusing on patient important outcomes will further inform the questions addressed in this review.

Fixed dose subcutaneous low molecular weight heparins versus adjusted dose unfractionated heparin for venous thromboembolism

BACKGROUND

Low molecular weight heparins (LMWHs) have been shown to be effective and safe in preventing venous thromboembolism (VTE). They may also be effective for the initial treatment of VTE. This is an update of a Cochrane review first published in 1999 and previously updated in 2004.

OBJECTIVES

To determine the effect of LMWH compared with unfractionated heparin (UFH) for the initial treatment of VTE.

SEARCH STRATEGY

Trials were identified by searching the Cochrane Peripheral Vascular Diseases Group Specialised Register and CENTRAL (The Cochrane Library). Colleagues and pharmaceutical companies were contacted for additional information.

SELECTION CRITERIA

Randomised controlled trials comparing fixed dose subcutaneous LMWH with adjusted dose intravenous or subcutaneous UFH in people with VTE.

DATA COLLECTION AND ANALYSIS

Two review authors assessed trials for inclusion and quality, and extracted data independently.

MAIN RESULTS

Twenty-three studies were included (n = 9587). Thrombotic complications occurred in 3.6% of participants treated with LMWH compared with 5.3% treated with UFH (odds ratio (OR) 0.70; 95% confidence interval (CI) 0.57 to 0.85). Thrombus size was reduced in 53% of participants treated with LMWH and 45% treated with UFH (OR 0.69; 95% CI 0.59 to 0.81). Major haemorrhages occurred in 1.1% of participants treated with LMWH compared with 1.9% treated with UFH (OR 0.58; 95% CI 0.40 to 0.83). In 19 trials, 4.3% of participants treated with LMWH died compared with 5.8% of participants treated with UFH (OR 0.77; 95% CI 0.63 to 0.93).Nine studies (n = 4451) examined proximal thrombosis, 2192 participants were treated with LMWH and 2259 with UFH. Subgroup analysis showed statistically significant reductions favouring LMWH in thrombotic complications and major haemorrhage. By end of follow up, 80 (3.6%) participants treated with LMWH had thrombotic complications compared with 143 (6.3%) treated with UFH (OR 0.57; 95% CI 0.44 to 0.75). Major haemorrhages occurred in 18 (1.0%) participants treated with LMWH compared with 37 (2.1%) treated with UFH (OR 0.50; 95% CI 0.29 to 0.85). Nine studies showed a statistically significant reduction in mortality favouring LMWH. By the end of follow up, 3.3% (70/2094) of participants treated with LMWH had died and 5.3% (110/2063) treated with UFH.

AUTHORS' CONCLUSIONS

Fixed dose LMWH is more effective and safer than adjusted dose UFH for the initial treatment of VTE. Compared to UFH, LMWH significantly reduced the incidence of thrombotic complications, the occurrence of major haemorrhage during initial treatment and overall mortality at follow up.

Anticoagulation for the initial treatment of venous thromboembolism in patients with cancer

BACKGROUND

Compared to patients without cancer, patients with cancer receiving anticoagulant treatment for venous thromboembolism are more likely to develop recurrent venous thromboembolism (VTE).

OBJECTIVES

To compare the efficacy and safety of three types of anticoagulants (i.e. low molecular weight heparin (LMWH), unfractionated heparin (UFH), and fondaparinux) for the initial treatment of VTE in patients with cancer.

SEARCH STRATEGY

A comprehensive search for studies of anticoagulation in cancer patients including a January 2007 electronic search of : Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and ISI the Web of Science.

SELECTION CRITERIA

Randomized clinical trials (RCTs) comparing LMWH, UFH, and fondaparinux in patients with cancer and objectively confirmed VTE.

DATA COLLECTION AND ANALYSIS

Using a standardized data form data was extracted in duplicate on methodological quality, participants, interventions and outcomes of interest that included all cause mortality, recurrent VTE, major bleeding, minor bleeding, thrombocytopenia and postphlebitic syndrome.

MAIN RESULTS

Of 3986 identified citations, 26 RCTs including cancer patients as subgroups fulfilled the inclusion criteria. Cancer subgroup data was obtained for 15 of the 26 RCTs. Thirteen studies compared a LMWH to UFH while one study compared fondaparinux to UFH and one study compared dalteparin to tinzaparin. Meta-analysis of 11 studies showed a statistically significant mortality reduction in patients treated with LMWH compared with those treated with UFH (Relative risk (RR) = 0.71; 95% confidence interval (CI) 0.52 to 0.98). There was little change in the results after excluding studies of lower methodological quality (RR = 0.72; 95% CI 0.52 to 1.00). A meta-analysis of three studies comparing LMWH with UFH in reducing recurrent VTE was inconclusive (RR = 0.78; 95% CI 0.29 to 2.08). No data was available for bleeding outcomes, thrombocytopenia or postphlebitic syndrome. Compared to UFH, fondaparinux showed a non-statistically significant benefit for the outcome of death (RR = 0.52; 95% CI 0.26 to 1.05). The one study comparing dalteparin to tinzaparin showed a non-statistically significant mortality reduction with dalteparin (RR = 0.86; 95% CI 0.43 to 1.73).

AUTHORS' CONCLUSIONS

Based on the included trials, LMWH is likely to be superior to UFH in the initial treatment of VTE in patients with cancer. However, there is a need for more trials to better address this research question in cancer patients. Moreover, researchers should consider making the raw data of RCTs available for individual patient data meta-analyses.

No Difference in Risk for Thrombocytopenia During Treatment of Pulmonary Embolism and Deep Venous Thrombosis With Either Low-Molecular-Weight Heparin or Unfractionated Heparin

BACKGROUND

Low-molecular-weight heparin (LMWH) is a popular alternative to unfractionated heparin (UH) for the treatment of pulmonary embolism (PE) and deep vein thrombosis (DVT), in part based on the perception of a lower risk for heparin-induced thrombocytopenia (HIT). To investigate the evidence supporting this perception, we performed a metaanalysis to compare the incidence of thrombocytopenia between LMWH and UH during PE and/or DVT treatment.

METHODS

Randomized trials comparing LMWH with UH for PE and/or DVT treatment were searched for in the MEDLINE database, bibliographies, and by correspondence with published investigators. Two reviewers independently selected high-quality studies and extracted data regarding heparin-associated thrombocytopenia (HAT), HIT confirmed by laboratory testing, and heparin-induced thrombocytopenia with thrombosis (HITT). Outcome rates between LMWH and UH were compared using a binomial, generalized linear mixed model with a logit link and Gaussian random effects for study.

RESULTS

Thirteen studies involving 5,275 patients met inclusion criteria. There were no statistically significant differences in HAT rates between the two treatments (LMWH, 1.2%; UH, 1.5%; p = 0.246). The incidence of documented HIT and HITT was too low to make an adequate comparison between groups.

CONCLUSIONS

Our review disclosed no statistically significant difference in HAT between LMWH and UH and insufficient evidence to conclude that HIT and HITT rates were different between them. There was no evidence from randomized comparative trials to support the contention that patients receiving treatment for PE or DVT with UH are more prone to these complications than those receiving LMWH.

The effect of anticoagulants on cancer risk and survival: systematic review

OBJECTIVES

Several in vitro and in vivo studies have shown that low molecular weight heparin and warfarin may directly inhibit tumour cell growth and prevent metastatic spread. However, the clinical evidence in support of an anti-cancer effect is less conclusive. We summarize the evidence from clinical studies that examine the effect of these anticoagulants on cancer development and briefly describe the current understanding of the potential mechanisms by which anticoagulants may exert an anti-cancer effect.

METHODS

English-language articles reporting on warfarin, coumarin or low molecular weight heparin for the treatment or prevention of cancer were selected from PUBMED. All randomized clinical trials, case-control studies, cohort studies, and meta-analyses were retrieved. Detailed data review and abstraction was performed according to pre-specified criteria.

RESULTS

Of ninety-nine articles retrieved, 12 warfarin and 17 low molecular weight heparin articles were included in the review. We found no consistent evidence that warfarin may improve cancer survival, though there is indirect evidence that prolonged warfarin use may decrease the risk of urogenital cancer. Low molecular weight heparin may improve survival of patients with small cell lung cancer and those with advanced malignancy who have more favorable prognoses.

CONCLUSION

Clinical evidence exists in support of an anti-neoplastic effect of anticoagulants. However, more research is needed to further define which cancer type and stage would most benefit from low molecular weight heparin, as well as to explore the role of warfarin in urogenital tumour development.

Life-Threatening Hemorrhage After Dalteparin Therapy in a Patient with Impaired Renal Function

Dalteparin and other low-molecular-weight heparins are frequently used for the treatment of deep vein thrombosis and for other indications. Unlike unfractionated heparin (UFH), dalteparin is mainly cleared through the kidney; therefore, it can accumulate in patients with impaired renal function, increasing the risk of hemorrhage. An 84-year-old woman with chronic renal failure was hospitalized because of stenosis of a femorofibular bypass in her right leg. Peripheral transluminal angioplasty was performed successfully. Later the same day, Doppler sonography revealed deep vein thrombosis of the left lower leg. Treatment with dalteparin was started. The patient was discharged home 3 days later, with dalteparin to be continued at home. One day later, the patient was rehospitalized because of a pronounced hematoma on her flank. Her hemoglobin level had dropped to 5.5 g/dl. Treatment with dalteparin was stopped, and protamine 2500 U and two transfusions of packed red blood cells were administered. Treatment with UFH and oral anticoagulants were started because of a persistent risk for venous thrombosis. Thereafter, the patient's hemoglobin level remained stable, and no further bleeding episodes occurred. As long as systematic studies of the efficacy and safety of dalteparin in patients with severe renal impairment are lacking, dalteparin should be avoided or used only with close monitoring of antifactor Xa activity in these patients. As an alternative, UFH can be used because monitoring of UFH is well established and easier than it is with dalteparin. Renal impairment does not notably influence the short elimination half-life of UFH, which unlike that of dalteparin or other low-molecular-weight heparins allows for rapid dosage adjustments to prevent hemorrhage.

Heparin in interventional radiology: a therapy in evolution

Interventional radiology techniques made possible by the antithrombotic properties of heparin have revolutionized treatment for a myriad of disorders. Newer low-molecular-weight heparins (LMWHs) offer several advantages over unfractionated heparin (UFH), especially in chronic settings. They are increasing in popularity for use during vascular procedures. However, LMWH shares limitations with UFH such as heterogeneity, nonspecificity, and induction of thrombocytopenia. These drawbacks have led to a search for the next generation of antithrombotic agents. Homogeneous drugs targeting specific coagulation cascade molecules are now available. The number of alternative anticoagulant drug combinations presents clinicians with a confusing array of choices. The strengths and weaknesses of UFH, LMWH, and direct antithrombin agents are presented. The promising future of LMWH and hirudins is discussed.

Five-year outcome study of deep vein thrombosis in the lower limbs

OBJECTIVE

Venous disease was evaluated in relation to post-thrombotic syndrome 5 years after deep venous thrombosis (DVT) in patients treated with a regimen of low-molecular-weight heparin (LMWH) and warfarin in a Hospital-in-the-Home program.

METHODS

The presence of flow, reflux and compressibility in 51 patients (102 limbs, 54 with DVT and 48 without DVT) was assessed by duplex ultrasound scanning. Blood tests were carried out for prothrombotic screening. Venous disease was related to pathologic severity of post-thrombotic syndrome, characterized by the CEAP (clinical, etiologic, anatomic, pathophysiologic) classification on a scale of 0 to 6.

RESULTS

In the 102 limbs studied, 30 patients (59%) had an underlying thrombophilic disorder. The most common cause of DVT was postoperation and prolonged immobilization not related to postoperation. The most common thrombophilic abnormalities were anticardiolipin antibody and a deficiency of protein C or S, or both. Twenty-six limbs (48%) had proximal involvement (proximal and proximal plus distal DVT); resolution (recanalization or normal vein) in these limbs was seen in 85% at 6 months and 96% at 5 years. After 5 years, 25 of these proximal DVT limbs (96%) developed reflux and there were 4 limbs in CEAP class 0, 8 in classes 1 to 3, and 14 in classes 4 to 6. All of the 28 limbs (52%) with distal DVT showed DVT resolution by 6 months. After 5 years, 10 limbs (36%) developed reflux, and 13 limbs were in class 0, 12 in classes 1 to 3, and 3 limbs in classes 4 to 6. No DVT was detected in the 48 contralateral limbs, but reflux was detected in 25 limbs (52%), predominately in the superficial veins (16 limbs, 64%).

CONCLUSIONS

The resolution of thrombus was more rapid and complete in patients with distal DVT than in those with proximal DVT. Patients with proximal DVT developed a more severe form of post-thrombotic syndrome that was likely related to the development of deep venous reflux. An important finding of this study was an unexpectedly high incidence of venous reflux in the apparently unaffected limb. Although these non-DVT limbs were not investigated at presentation, our data is consistent with the hypothesis that DVT may result in a more systemic disorder of venous function.

Fixed dose subcutaneous low molecular weight heparins versus adjusted dose unfractionated heparin for venous thromboembolism

BACKGROUND

Low molecular weight heparins (LMWH) have been shown to be effective and safe in preventing venous thromboembolism (VTE), and may also be effective for the initial treatment of VTE.

OBJECTIVES

To determine the effect of LMWH compared with unfractionated heparin (UFH) for the initial treatment of VTE.

SEARCH STRATEGY

Trials were identified from the Cochrane Peripheral Vascular Diseases Group's Specialised Register, CENTRAL and LILACS. Colleagues and pharmaceutical companies were contacted for additional information.

SELECTION CRITERIA

Randomised controlled trials comparing fixed dose subcutaneous LMWH with adjusted dose intravenous or subcutaneous UFH in people with VTE.

DATA COLLECTION AND ANALYSIS

At least two reviewers assessed trials for inclusion and quality, and extracted data independently.

MAIN RESULTS

Twenty-two studies were included (n = 8867). Thrombotic complications occurred in 151/4181 (3.6%) participants treated with LMWH, compared with 211/3941 (5.4%) participants treated with UFH (odds ratio (OR) 0.68; 95% confidence intervals (CI) 0.55 to 0.84, 18 trials). Thrombus size was reduced in 53% of participants treated with LMWH and 45% treated with UFH (OR 0.69; 95% CI 0.59 to 0.81, 12 trials). Major haemorrhages occurred in 41/3500 (1.2%) participants treated with LMWH, compared with 73/3624 (2.0%) participants treated with UFH (OR 0.57; 95% CI 0.39 to 0.83, 19 trials). In eighteen trials, 187/4193 (4.5%) participants treated with LMWH died, compared with 233/3861 (6.0%) participants treated with UFH (OR 0.76; 95% CI 0.62 to 0.92). Nine studies (n = 4451) examined proximal thrombosis; 2192 participants treated with LMWH and 2259 with UFH. Subgroup analysis showed statistically significant reductions favouring LMWH in thrombotic complications and major haemorrhage. By the end of follow up, 80 (3.6%) participants treated with LMWH had thrombotic complications, compared with 143 (6.3%) treated with UFH (OR 0.57; 95% CI 0.44 to 0.75). Major haemorrhage occurred in 18 (1.0%) participants treated with LMWH, compared with 37 (2.1%) treated with UFH (OR 0.50; 95% CI 0.29 to 0.85). Nine studies (n = 4157) showed a statistically significant reduction favouring LMWH with respect to mortality. By the end of follow up, 3.3% (70/2094) of participants treated with LMWH had died, compared with 5.3% (110/2063) of participants treated with UFH (OR 0.62; 95% CI 0.46 to 0.84).

REVIEWERS' CONCLUSIONS

LMWH is more effective than UFH for the initial treatment of VTE. LMWH significantly reduces the occurrence of major haemorrhage during initial treatment and overall mortality at follow up.

Correlation between thrombus regression and recurrent venous thromboembolism. Examining venographic and clinical effects of low-molecular-weight heparins: a meta-analysis

We analyzed the correlation between thrombus regression on control venography performed after discontinuation of heparin therapy and recurrent venous thromboembolism (VTE) detected during clinical follow-up in randomized trials comparing low-molecular-weight heparin (LMWH) and unfractionated heparin (UFH) in patients with deep vein thrombosis (DVT). Data were abstracted from MEDLINE, conference abstracts and reference lists of previous reviews. Randomized, controlled trials comparing LMWH and UFH for the treatment of DVT using a combined venographic and clinical assessment and with at least 2 months of follow-up were selected. The proportions of patients with thrombus regression on control venography performed soon after discontinuation of heparin therapy and recurrent VTE at 2-6 months were independently collected by two researchers. Thirteen studies met the inclusion criteria. There was a strong inverse correlation between thrombus regression and recurrent VTE (r =- 0.70; P =0.008). The venographic effect varied between the different LMWHs (P = 0.013). A very strong correlation was found when the results were pooled by the type of LMWH used (r = - 0.84; P=0.037). No influence of the dose interval used on the venographic effect (P=0.156) or on recurrent VTE (P=0.218) was shown. The lack of thrombus regression in venography, performed soon after heparin discontinuation, was correlated with clinical recurrence. Non-invasive imaging techniques should be relevant to identify non-responders and to assess the optimal duration of initial heparin treatment in daily clinical practice.

Low molecular weight heparin (dalteparin) is equally effective as unfractionated heparin in reducing coagulation activity and perfusion abnormalities during the early treatment of pulmonary embolism

Little is known about the differences between unfractionated heparin (UFH) and low molecular weight heparin (LMWH) with regard to their effects on coagulation activity during treatment for pulmonary embolism. The objective of this study was to compare UFH and LMWH (dalteparin) in the early treatment of pulmonary embolism in terms of control of coagulation markers and perfusion abnormalities. Thirty-seven patients with acute pulmonary embolism were randomized to receive intravenous UFH or subcutaneous dalteparin, each accompanied by acenocoumarol. Daily blood samples were obtained for the measurement of thrombin generation (fragments 1 and 2 [F1+2], thrombin-antithrombin (TAT) complexes and fibrin monomers [FMs]) and fibrinolysis (d-dimer concentrations and clot-lysis times). Ventilation-perfusion scintigraphies were performed, and with the data they yielded, percentage of vascular obstruction scores (PVOs) were calculated on days 0 and 5. The international normalized ratio was within the therapeutic range in both groups on day 3. F1+2 and TAT complexes rapidly normalized, without differences between the groups (P =.5 and.4, respectively). FM levels did not decrease and, in fact, showed an increase in the UFH group from day 3 on (P <.05 between groups). d-Dimer levels decreased over time, with no differences between groups (P =.6). Clot-lysis times were shorter in the UFH group (P <.05). PVOs on days 0 and 5 were not different (P =.5 and.8, respectively), but the decrease in PVOs over time was greater in the dalteparin group (P =.04). These results show that dalteparin is at least as effective as UFH in reducing coagulation activity and perfusion abnormalities in the early treatment of pulmonary embolism.

Low Molecular Weight Heparins in Special Populations

Low molecular weight heparins (LMWH) are replacing unfractionated heparin (UH) as safe and effective agents for the prevention and treatment of thromboembolism. Although LMWH offer many advantages over UH, usage is less clearly defined in certain special populations, including renal dysfunction, obesity and pregnancy. This article will briefly review the pharmacology of LMWH and discuss usage in these special populations.

Outpatient treatment of acute venous thromboembolic disease

Once- or twice-daily subcutaneous dosing of LMWHs without laboratory monitoring has facilitated outpatient VTE therapy. Clinical trials have demonstrated at least equivalent efficacy and safety and potential cost savings of outpatient therapy for uncomplicated proximal DVT with LMWH when compared with inpatient therapy. Explicit criteria exist for outpatient DVT therapy. Home therapy for PE requires further evaluation before it can be recommended outside of a trial or other supervised setting.

Effects of ximelagatran, the oral form of melagatran, in the treatment of caval vein thrombosis in conscious rats

The antithrombotic effects of direct (ximelagatran and hirudin) and indirect (dalteparin) anticoagulants were compared using a deep venous thrombosis (DVT) treatment model in conscious rats. Thrombus formation was induced in the inferior caval vein by total stasis plus topically applied ferric chloride. After 1-h thrombus maturation, one group of 10 rats were sacrificed and the mean thrombus weight in this group was 27.3 +/- 2.7 mg. This thrombus weight was handled as a reference to which all other results were compared. In all other groups, the total occlusion was removed after 1 h but a partial stasis was retained, permitting some blood flow around the thrombus. Groups of animals received subcutaneous (s.c.) dalteparin (200 IU/kg), s.c. hirudin (0.75 micromol/kg), one of four oral doses of ximelagatran (2.5, 5, 10 or 20 micromol/kg) or s.c. saline (control). After the 3-h treatment, mean thrombus weight in the saline group (26.5 +/- 3.3 mg) did not differ significantly from that of the reference group (27.3 +/- 2.7 mg, see above). Ximelagatran decreased thrombus weight in a dose-dependent manner, with an estimated ID(50) of 15 micromol/kg. Mean thrombus weight with the highest ximelagatran dose (11.1 +/- 1.3 mg) was similar to that with hirudin (13.0 +/- 1.5 mg). The effect of dalteparin on thrombus regression was much less pronounced (20.2 +/- 1.2 mg), compared with ximelagatran and hirudin, even though it was administered at a dose that yielded a similar activated partial thromboplastin time (APTT) prolongation. In conclusion, the results from this DVT treatment model showed that direct thrombin inhibitors ximelagatran and hirudin exhibited superior antithrombotic properties to low molecular weight heparin (LMWH).

Treating venous thromboembolism: enoxaparin

This article reviews the developments that have occurred in the treatment of venous thromboembolism during the last decade, with emphasis on the establishment of low molecular weight heparin as a therapeutic agent of proven efficacy and examines the evidence that supports the movement from inpatient to outpatient hospital management of venous thromboembolism.

Severe postoperative haemorrhage and airway obstruction following high-dose enoxaparin

Unfractionated heparin infusion may be a more suitable choice of anticoagulant treatment in patients with venous thromboembolism in the immediate postoperative period.

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.

Effects of a low-molecular-weight heparin on thrombus regression and recurrent thromboembolism in patients with deep-vein thrombosis

BACKGROUND

Low-molecular-weight heparins are frequently used to treat venous thromboembolism, but optimal dosing regimens and clinical outcomes need further definition.

METHODS

In this multicenter, open-label study with blinded adjudication of end points, we randomly assigned patients with acute deep-vein thrombosis to one of three treatment regimens: intravenous administration of unfractionated heparin; subcutaneous administration of a low-molecular-weight heparin, reviparin, twice a day for one week; or subcutaneous administration of reviparin once a day for four weeks. The primary end point was evidence of regression of the thrombus on venography on day 21; secondary end points were recurrent venous thromboembolism, major bleeding within 90 days after enrollment, and death.

RESULTS

Of the patients receiving unfractionated heparin, 40.2 percent (129 of 321) had thrombus regression, as compared with 53.4 percent (175 of 328) of patients receiving reviparin twice daily and 53.5 percent (167 of 312) of the patients receiving reviparin once daily. With regard to thrombus regression, reviparin administered twice daily was significantly more effective than unfractionated heparin (relative likelihood of thrombus regression, 1.28; 97.5 percent confidence interval, 1.08 to 1.52), as was reviparin administered once daily (relative likelihood, 1.29; 97.5 percent confidence interval, 1.08 to 1.53). Mortality and the frequency of episodes of major bleeding were similar in the three groups.

CONCLUSIONS

In acute deep-vein thrombosis, reviparin regimens are more effective than unfractionated heparin in reducing the size of the thrombus. Reviparin is also more effective than unfractionated heparin for the prevention of recurrent thromboembolism and equally safe.

For the initial treatment of venous thromboembolism: are all low-molecular-weight heparin compounds the same?

Low-molecular-weight heparin compounds have been used in the treatment of patients with venous thromboembolism for approximately 15 years. Ever since their introduction, there has been discussion about whether low-molecular-weight heparin compounds differ in their efficacy and safety. The best answer would be provided by direct comparison of different low-molecular-weight heparin preparations; however, these trials have not been conducted. Classical meta-analysis has its limitations for such a comparison since only a very small number of trials with the respective low-molecular-weight heparin compounds are available. The objective of the present analysis has been the use of meta-regression to compare the efficacy and safety of different low-molecular-weight heparin compounds in the initial treatment of patients with venous thromboembolism. We used computerized literature searches to identify studies that compared dose-adjusted unfractionated heparin treatment with fixed dose subcutaneous low-molecular-weight heparin treatment in patients with established venous thromboembolism. The individual odds ratios of the studies were plotted against the absolute percentage of the major outcomes in the unfractionated heparin control group. Linear regression was used to find differences between different low-molecular-weight heparin compounds. There appears to be some variation in efficacy and safety among the currently available low-molecular-weight heparin preparations.

The use of low molecular weight heparin in pediatric patients: a prospective cohort study

OBJECTIVE

Low molecular weight heparins (LMWHs) offer several advantages over standard anticoagulant therapy (unfractionated heparin/warfarin) including predictable pharmacokinetics, minimal monitoring, and subcutaneous administration. Our objective was to determine the safety and efficacy of LMWHs in children.

METHODS

A prospective cohort of children treated with the LMWH enoxaparin (Rhone Poulenc Rorer) was monitored at the Hospital for Sick Children, Toronto, Canada, from March 1994 until July 1997.

RESULTS

There were 146 courses of LMWH administered for treatment and 31 courses for prophylaxis of thromboembolic events (TEs). Clinical resolution of TEs occurred in 94% of children receiving therapeutic doses of LMWH, and 96% of children receiving prophylactic doses of LMWH had no symptoms of recurrent or new TEs. Major bleeding occurred in 5% of children receiving therapeutic doses. Recurrent or new TEs occurred in 1% and 3% of children receiving therapeutic and prophylactic doses of LMWH, respectively.

CONCLUSION

LMWH appears to be efficacious and safe for both management and prophylaxis of TEs. The results of this cohort study justify a randomized controlled trial comparing LMWH with standard therapy for the management of TEs in children.

Fixed dose subcutaneous low molecular weight heparins versus adjusted dose unfractionated heparin for venous thromboembolism

BACKGROUND

Low molecular weight heparins have been shown to be effective and safe for prevention of venous thromboembolism. There is accumulating evidence that these new anticoagulants are also effective and safe for treatment of venous thromboembolism.

OBJECTIVES

The objective of this review was to determine the effect of fixed-dose, subcutaneous low molecular weight heparins compared with adjusted-dose, intravenous or subcutaneous, unfractionated heparin for initial treatment of acute deep venous thrombosis or pulmonary embolism.

SEARCH STRATEGY

Trials were identified from the Cochrane Peripheral Vascular Diseases Group trials register and LILACS. The reviewers contacted colleagues and representatives of pharmaceutical companies for additional information about trials.

SELECTION CRITERIA

Randomised trials comparing fixed-dose, subcutaneous low molecular weight heparin with adjusted-dose, intravenous or subcutaneous, unfractionated heparin in patients with venous thromboembolism.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed trials for inclusion and quality, and extracted data independently.

MAIN RESULTS

Fourteen studies with a total of 4754 patients were included. By the end of follow up in ten trials, thrombotic complications occurred in 86 (4.3%) of the 1998 patients treated with low molecular weight heparin, compared with 113 (5.6%) of the 2021 patients treated with unfractionated heparin (odds ratio 0.76, 95% confidence interval 0.57 to 1.01). In eight trials a reduction in thrombus size was shown by 60% treated with low molecular weight heparin and 54% treated with unfractionated heparin (odds ratio 0.77, 95% confidence interval 0.61 to 0.97). At the end of the initial treatment period, in all 14 of the trials, major haemorrhages occurred in 30 (1.3%) of the 2353 patients treated with low molecular weight heparin, compared with 51 (2.1%) of the 2401 patients treated with unfractionated heparin (odds ratio 0.60, 95% confidence interval 0.39 to 0.93). By the end of follow up in 11 trials, 135 (6.4%) of the 2108 patients treated with low molecular weight heparin had died, compared with 172 (8.0%) of the 2137 patients treated with unfractionated heparin (odds ratio 0.78, 95% confidence interval 0.62 to 0.99). Five studies with a total of 1636 patients examined proximal (above the knee) thrombosis; 814 treated with low molecular weight heparin and 822 with unfractionated heparin. A sub-analysis of these trials showed statistically significant reductions favouring the action of low molecular weight heparin in three areas: thrombotic complications; major haemorrhages; and overall mortality. By the end of follow up 39 (4. 8%) patients treated with low molecular weight heparin had thrombotic complications, compared with 64 (7.8%) treated with unfractionated heparin (odds ratio 0.60, 95% confidence interval 0. 40 to 0.89). Major haemorrhages occurred in 8 (1.0%) treated with low molecular weight heparin, compared with 68 (8.3%) treated with unfractionated heparin (odds ratio 0.44, 95% confidence interval 0. 21 to 0.95). By the end of follow up, 44 (5.4%) treated with low molecular weight heparin had died, compared with 68 (8.3%) treated with unfractionated heparin (odds ratio 0.64, 95% confidence interval 0.43 to 0.93).

REVIEWER'S CONCLUSIONS

Low molecular weight heparin is at least as effective as unfractionated heparin in preventing recurrent venous thromboembolism, and significantly reduces the occurrence of major haemorrhage during initial treatment and overall mortality at the end of follow-up. It can be adopted safely as the standard therapy for deep venous thrombosis, and studies comparing individual low molecular weight heparins are merited.

Treatment of Venous Thromboembolism with Low-Molecular-Weight Heparin

There is now ample evidence to indicate that certain low-molecular-weight heparins given subcutaneously can replace continuous intravenous unfractionated heparin for the initial treatment of venous thromboembolism. The low-molecular-weight heparins have a predictably high absorption rate when given subcutaneously and a prolonged duration of action, permitting them to be given by a once or twice daily injection for the prevention or treatment of venous thrombosis. Furthermore, treatment does not require laboratory monitoring, thus eliminating the need for continuous IV infusion and permitting the early discharge of patients with venous thromboembolism. This should eventually lead to the outpatient treatment of venous thromboembolism. Studies to date indicate that low-molecular-weight heparin is more cost-effective than unfractionated heparin in the treatment of venous thromboembolism and the cost effectiveness will be increased by out-of-hospital treatment. At the present time, the findings associated with any individual low-molecular-weight heparin preparation cannot be extrapolated to different low-molecular-weight heparins, and therefore each must be evaluated in separate clinical trials. The information to date is that low-molecular-weight heparin is safer and more effective than continuous intravenous unfractionated heparin in the treatment of proximal venous thrombosis. The decreased mortality rate seen in two clinical trials, particularly in patients with metastatic cancer, was quite unexpected. This requires further confirmation in larger prospective randomized trials.

Outpatient treatment of deep vein thrombosis: translating clinical trials into practice

To develop a rational approach to outpatient management, we review the pharmacologic properties of low-molecular-weight heparins and their efficacy in clinical trials of deep vein thrombosis treatment. Low-molecular-weight heparins have better bioavailability and more predictable anticoagulant activity than standard heparin and thus can be administered without routine laboratory monitoring. Randomized trials comparing subcutaneous low-molecular-weight heparin administered primarily at home with inpatient intravenous standard heparin have established the safety and efficacy of outpatient treatment of selected patients. However, many patients were excluded from these studies. The benefits demonstrated in carefully controlled clinical trials of outpatient treatment of deep vein thrombosis required a complex multidisciplinary organization of medical care that is not readily achievable in routine practice. A structured protocol is necessary to ensure that patient care is optimal. The essential components of an outpatient program include appropriate patient selection, adequate patient education, daily follow-up during therapy with low-molecular-weight heparin, and easy access to health-care professionals.

Criteria for outpatient management of proximal lower extremity deep venous thrombosis

STUDY OBJECTIVES

To develop and to evaluate selection criteria for outpatient management of deep venous thrombosis (DVT).

DESIGN

We developed outpatient treatment eligibility criteria that incorporated demographic and clinical data. We aimed to exclude patients at high risk for bleeding or recurrent clotting, as well as those with pulmonary embolism, limited cardiopulmonary reserve, or need for hospitalization due to another illness. Then, we retrospectively applied the criteria to hospitalized patients with newly diagnosed proximal lower extremity DVT to determine the fraction of patients eligible for outpatient therapy; patients were classified as eligible, possibly eligible, or ineligible for home treatment based on the selection criteria.

SETTING

University hospital.

PATIENTS

One hundred ninety-five hospitalized patients diagnosed as having proximal lower extremity DVT by duplex ultrasound over a 1-year period.

MEASUREMENTS

Frequency of complications during initial DVT therapy, including major bleeding, symptomatic thromboembolism, and death.

RESULTS

Eighteen (9%) patients were classified as eligible, and 18 (9%) were classified as possibly eligible for outpatient therapy. None of these patients developed complications. Of the 159 (82%) patients classified as ineligible, 13 (8%; 95% confidence interval [CI], 4 to 12%) died or developed serious complications. Therefore, the eligibility criteria had a sensitivity of 100% (95% CI, 92 to 100%) and a negative predictive value of 100% (95% CI, 92 to 100%) for predicting serious complications.

CONCLUSIONS

Specific eligibility criteria may identify a subset of patients with acute DVT who can be treated safely at home.