Subcutaneous low-molecular-weight heparin compared with continuous intravenous heparin in the treatment of proximal-vein thrombosis

Non-haemorrhagic obstetric shock

The causes of non-haemorrhagic obstetric shock (pulmonary thromboembolism, amniotic fluid embolism, acute uterine inversion and sepsis) are uncommon but responsible for the majority of maternal deaths in the developed world. Clinically suspected pulmonary thromboembolism should be treated initially with heparin and objective testing should be performed. If the diagnosis is confirmed, heparin is usually continued until delivery, following which anticoagulation in the puerperium is achieved with either warfarin or heparin. Amniotic fluid embolism is a rare complication of pregnancy, occurring most commonly during labour. The management of amniotic fluid embolism involves maternal oxygenation, the maintenance of cardiac output and blood pressure, and the management of any associated coagulopathy. Acute uterine inversion arises most commonly following mismanagement of the third stage of labour. The shock in uterine inversion is neurogenic in origin, although there may also be profound haemorrhage. The management of this condition includes maternal resuscitation and replacement of the uterus either manually, surgically or by hydrostatic pressure. Genital tract sepsis remains a significant cause of maternal death, the most common predisposing factor being prolonged rupture of the fetal membranes. The management of septic shock in pregnancy includes resuscitation, identification of the source of infection and alteration of the systemic inflammatory response.

The Essence Trial: Efficacy and Safety of Subcutaneous Enoxaparin in Unstable Angina and Non-Q-Wave MI: A Double-Blind, Randomized, Parallel-Group, Multicenter Study Comparing Enoxaparin and Intravenous Unfractionated Heparin: Methods and Design

Antithrombotic therapy reduces the risk of recurrent ischemic events in patients with unstable angina. The primary aim of the ESSENCE trial is to evaluate the efficacy of enoxaparin (low molecular weight heparin) versus unfractionated heparin, plus aspirin, in patients with rest angina or non-Q-wave infarction. This is a randomized, double-blind, placebo-controlled study of 3180 patients comparing enoxaparin, 1 mg/kg sc bid, with unfractionated heparin via continuous iv infusion to maintain the aPTT at 2 x control. Patients within 24 hours of the onset of acute myocardial ischemia without ST elevation are eligible, and trial therapy is administered for a minimum of 48 hours to a maximum of 8 days. Primary endpoints analyzed are death, myocardial infarction (MI), or recurrent angina at 14 days. Currently 3019 patients have been randomized in 10 countries. The mean age is 64 years, 33% are female, and 46% have had a prior MI. The overall event rates at 14 days are 1.7% mortality, 5.9% subsequent MI, and 17% recurrent angina. The composite triple endpoint rate is 23.6%. Recruitment should be complete by June 1996. The methods and design of the study are presented in this article.

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.

The emerging role of low-molecular-weight heparin in cardiovascular medicine

Although unfractionated heparin is widely used in the treatment of acute coronary syndromes, it has several pharmacokinetic, biophysical, and biological limitations. The practical advantages and success of low-molecular-weight heparin administered subcutaneously without laboratory monitoring for the treatment of venous thromboembolism have prompted a number of randomized studies investigating the efficacy and safety of these agents in patients with acute coronary syndromes. This article will review the limitations of unfractionated heparin and the mechanisms by which low-molecular-weight heparin overcomes these limitations, as well as the results of recent trials involving low-molecular-weight heparin in the management of patients with acute coronary syndromes.

Low-molecular-weight heparins in the treatment of venous thromboembolism

Venous thromboembolism is a common disease that is associated with considerable morbidity if left untreated. Recently, low-molecular-weight heparins (LMWHs) have been evaluated for use in acute treatment of deep venous thrombosis and pulmonary embolism. Randomized studies have shown that LMWHs are as effective as unfractionated heparin in the prevention of recurrent venous thromboembolism, and are as safe with respect to the occurrence of major bleeding. A pooled analysis did not show substantial differences among different LMWH compounds used, but no direct comparison of the different LMWHs is currently available. Finally, in patients with pulmonary embolism, there is a relative lack of large studies of daily practice. It could be argued that large prospective studies, in patients who were treated with LMWHs from the moment of diagnosis, are needed.

Heparin-induced thrombocytopenia and thrombosis

Heparin remains the most commonly used parenteral medication in hospitalized patients. Heparin induced thrombocytopenia (HIT) and heparin induced thrombocytopenia with thrombosis syndrome or the white clot syndrome are important complications of heparin use. This article provides an in-depth review of the etiopathogenesis, clinical manifestations, diagnosis, and management options in patients with HIT. Clinical problems associated with HIT such as antiphospholipid antibody syndrome and venous gangrene are described. The management options of HIT patients during cardiac interventional procedures and coronary surgery as well as recent advances in therapeutic options are summarized.

Treatment of venous thromboembolism

The combination of heparin and oral anticoagulants has been the treatment of choice for most patients with venous thromboembolism in the last two decades. Heparin has been proven to be effective when administered by intravenous continuous infusion or by subcutaneous injection. Oral anticoagulants should be started at the same time and heparin should be discontinued when the levels of the International Normalized Ratio reach the therapeutic range, between 2.0 and 3.0. Low molecular weight heparin has potential advantages over heparin and can be administered in subcutaneous weight-adjusted fixed doses without need for monitoring. This has made home treatment of a large proportion of patients possible. Randomized clinical trials have demonstrated the efficacy and safety of this approach. The optimal duration of the secondary prophylaxis with oral anticoagulants is still a matter of debate. The rate of recurrence has been shown to be elevated, particularly in those patients with idiopathic venous thromboembolism. The presence of an active cancer or a thrombophilic state may require long-term anticoagulation, although not all the congenital hypercoagulable states seem to carry the same level of risk. A 3-month therapy is recommended when a transient risk factor is identified; lifelong treatment is recommended for patients with a second episode of venous thromboembolism. In all other cases, 6 months are currently recommended, but thereafter close monitoring of the patients is advisable. The use of different treatment strategies such as vena caval filter placement, thrombolysis, and surgical thrombectomy should be restricted to a limited number of situations.

Clotting for the Clinician: An Overview of Thrombosis and Antithrombotic Therapy

The use of antithrombotic therapy has taken on central importance in the field of cardiovascular disease. Currently, anticoagulants and antiplatelet drugs are central to the treatment and the primary and secondary prevention of coronary artery disease. New insights into the "revised" coagulation cascade have highlighted new targets for intervention. In addition, the interactions between the coagulation system and platelets demonstrate ways that anticoagulants may affect platelet function and how antiplatelet agents may have anticoagulant effects. This overview will describe the present understanding of primary and secondary hemostasis, and current and future therapeutic approaches to modify these systems for therapeutic effects in cardiovascular medicine.

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.

Recurrent venous thromboembolism in a Spanish population: incidence, risk factors, and management in a hospital setting

The major concern in the management of venous thromboembolism is the propagation of thrombus and rethrombosis. The incidence of recurrences and the duration of oral anticoagulant therapy in these patients are still controversial. The aim of this study was to determine the incidence, timing, and outcome of further thrombotic events after an initial episode of venous thromboembolism in a hospital setting. In addition, we evaluated potential risk factors for all these outcomes. This was designed as a retrospective analysis of all patients admitted to our Center with an episode of deep vein thrombosis and/or pulmonary embolism between 1986 and 1996. The patients included in the study had to be treated with unfractionated heparin or low molecular weight heparin, followed by at least 3 months of oral anticoagulants. Natural and acquired hemostasis inhibitors were assayed in patients aged less than 50 years. A total of 290 patients with a first episode of venous thromboembolism were included in the study. A total of 33 patients (11.9%, 95% confidence interval. 7.4-14.6) had recurrent episodes. The cumulative incidence of recurrent venous thromboembolism after 2, 5, and 10 years was 7.68, 10, and 12.4%, respectively. The incidence of rethrombosis was significantly higher in patients with idiopathic venous thromboembolism than in patients with secondary thrombosis. Abnormalities of hemostasis were found in 54.5% (95% confidence interval, 37.6-71.4) of the patients with recurrences and under the age of 50 years. Three of seven patients who stopped anticoagulant therapy after the second episode presented a third thrombotic event. In our study population, those patients with idiopathic venous thromboembolism seem to have an increased risk of recurrence. The second thrombotic episode occurs more frequently during the following 2 years after cessation of anticoagulation therapy. Our findings strongly support the use of long-term anticoagulant therapy in patients with recurrent venous thromboembolism.

New-generation anticoagulants: the low molecular weight heparins

Heparin has been the mainstay of acute anticoagulation therapy for decades. Within the past 20 years, several different heparin fractions-collectively known as low molecular weight heparins (LMWHs)-have been evaluated in various medical and surgical settings in which anticoagulation is routinely warranted. The LMWHs are efficacious, safe, cost-effective, and easier to administer and monitor than standard, unfractionated heparin. As LMWH use becomes more widespread, emergency physicians will use these new agents instead of unfractionated heparin for unstable angina, non-Q-wave myocardial infarction, or thromboembolic disease. This review focuses on the pharmacologic properties of unfractionated heparin and LMWH, associated complications, and the use of these agents in acute ischemic coronary syndromes, thromboembolic disease, and other selected clinical situations.

Partial depletion of tissue factor pathway inhibitor during subcutaneous administration of unfractionated heparin, but not with two low molecular weight heparins

Tissue factor pathway inhibitor (TFPI) is released to circulating blood after intravenous (i.v.) and subcutaneous (s.c.) injections of heparins, and may thus contribute to the antithrombotic effect of heparins. We have recently shown that total TFPI activity, plasma free TFPI antigen, and heparin releasable TFPI were partially depleted during repeated and continuous i.v. infusion of unfractionated heparin (UFH), but not during s.c. treatment with a low molecular weight heparin (LMWH). The difference may be attributed to a different mode of action or the different mode of administration. In the present randomized cross-over study, s.c. administration of therapeutic doses of UFH was compared with s.c. administration of two LMWHs. 12 healthy male volunteers were treated for 3 d with UFH, 250 U/kg twice daily, dalteparin, 200 U/kg once daily, and enoxaparin, 1.5 mg/kg once daily. Six participants were also treated with UFH, 300 U/kg once daily. On day 5 a single dose of either drug was given. Peak levels of total TFPI activity and free TFPI antigen were detected 1 h after injection, whereas maximal prolongation of activated partial thromboplastin time (APTT) and peak levels of anti-factor Xa activity and anti-factor IIa activity were detected after 4 h. On UFH administered twice daily, free TFPI antigen decreased by 44% from baseline level before the first injection on day 1 to pre-injection level on day 5. On UFH administered once daily, basal free TFPI antigen decreased by 50%, 56% and 27% on day 2, 3 and 5 respectively, compared with day 1. Minimal depletion of TFPI was detected during treatment with LMWHs. The study demonstrates the different modes of action of LMWHs and UFH and may help to explain the superior antithrombotic efficacy of LMWHs.

Major bleeding after hospitalization for deep-venous thrombosis

PURPOSE

Most studies of oral anticoagulant-related bleeding have analyzed the incidence of adverse outcomes among patients with a variety of different conditions and without any comparison with a control group. We determined the incidence, time course, and risk factors associated with major bleeding after hospital discharge among patients with deep-vein thrombosis, and estimated the excess risk of bleeding associated with oral anticoagulant therapy.

METHODS

A total of 22,000 adults were hospitalized in California for 3 or more days with a diagnosis of deep-venous thrombosis between January 1, 1992, and September 30, 1994. We determined the risk factors associated with readmission for bleeding. We compared the incidence of readmission for bleeding with comparison cohorts of patients with pneumonia or cellulitis who were matched for age, gender, race, and length of hospital stay.

RESULTS

Of 21,250 patients with deep-venous thrombosis who were discharged without bleeding, 1.4% were readmitted for bleeding within 91 days; the rate was 2.7 times greater in the first 30 days than in the next 61 days. Risk factors for bleeding included hospitalization with gastrointestinal bleeding during the previous 18 months (relative hazard [RH] = 2.6, 95% confidence interval [CI]: 1.6 to 4.1), hospitalization with an alcohol-related diagnosis during the previous 18 months (RH = 2.6, 95% CI: 1.4 to 4.8), chronic renal disease (RH = 2.4, 95% CI: 1.4 to 4.2), female gender (RH = 1.7, 95% CI: 1.3 to 2.2), presence of a malignancy (RH = 1.6, 95% CI: 1.2 to 2.2), nonwhite race (RH = 1.6, 95% CI: 1.2 to 2.1), and age over 65 years (RH = 1.3, 95% CI: 1.0 to 1.7). Significantly more women (n = 40) had intracranial bleeding than men (n = 18, P = 0.02). In the comparison cohorts, the incidence of readmission for bleeding within 3 months of discharge was 0.7%, and the relative risk (RR) of readmission was greater in those with deep-venous thrombosis than in those with cellulitis (RR = 2.0, 95% CI: 1.6 to 2.5) or pneumonia (RR = 2.0, 95% CI: 1.7 to 2.5).

CONCLUSIONS

The incidence of rehospitalization for bleeding was greatest in the first 30 days after discharge, and was approximately twice that seen in patients hospitalized for cellulitis or pneumonia. Further studies are needed to determine why women and nonwhite patients are at increased risk for anticoagulant-related bleeding.

A controlled trial of low-molecular-weight heparin (dalteparin) versus unfractionated heparin as anticoagulant during continuous venovenous hemodialysis with filtration

OBJECTIVE

To compare the efficacy, safety, and cost of fixed-dose low-molecular-weight heparin (dalteparin) with adjusted-dose unfractionated heparin as anticoagulant for continuous hemofiltration.

DESIGN

Prospective, randomized, controlled clinical trial.

SETTING

University-affiliated adult intensive care unit

PATIENTS

All patients requiring continuous hemofiltration for acute renal failure or systemic inflammatory response syndrome (SIRS) were eligible. Fifty-seven patients were enrolled. Eleven were excluded, seven because of major protocol violations and four died before hemofiltration.

INTERVENTIONS

Patients received continuous venovenous hemodialysis with filtration with prefilter replacement at 500 mL/hr and countercurrent dialysate at 1000 mL/hr. Filters were primed with normal saline containing anticoagulant. Dalteparin-treated patients received a commencement bolus of 20 units/kg and a maintenance infusion at 10 units/kg/hr. Heparin-treated patients received a commencement bolus of 2000-5000 units and a maintenance infusion at 10 units/kg/hr, titrated to achieve an activated partial thromboplastin time in the patient of 70-80 secs.

MEASUREMENTS AND MAIN RESULTS

The primary outcome measure--time to failure of the hemofilter--was compared using survival analysis. Twenty-two patients (13 with acute renal failure and nine with SIRS; total, 41 filters) were randomized to heparin. Twenty-five patients (16 with acute renal failure and nine with SIRS; total, 41 filters) were randomized to dalteparin. Mean (SE) activated partial thromboplastin time in the heparin group was 79 (4.3) secs. Mean (SE) anti-factor-Xa activity in the six patients given dalteparin who were assayed was 0.49 (0.07). Mean (SE) prehemofiltration platelet count was 225 (35.5) x 10(9) for heparin and 178 (18.1) x 10(9) for dalteparin (p = .24, unpaired Student's t-test). Mean (SE) prehemofiltration hemoglobin was 11.4 (0.61) g/dL for heparin and 10.6 (0.38) g/dL for dalteparin (p = .31, unpaired Student's t-test).

PRIMARY OUTCOME

There was no significant difference in the time to failure between the two groups (p = .75, log rank test). For dalteparin, Kaplan-Meier (K-M) mean (SE) time to failure of the hemofilter was 46.8 (5.03) hrs. For heparin, K-M mean (SE) time to failure was 51.7 (7.51) hrs. The 95% CI for difference in mean time to failure was -13 to 23 hrs. The power of this study to detect a 50% change in filter life was >90%.

SECONDARY OUTCOMES

Mean (SE) reduction in platelet count during hemofiltration was 63 (25.8) x 10(9) for heparin and 41.8 (26.6) x 10(9) for dalteparin (p = .57, unpaired Student's t-test). Eight patients given dalteparin and four patients given heparin had screening for heparin-induced thrombocytopenia; three of the dalteparin patients and one of the heparin patients were positive (p = 1.0, Fisher's exact test). There were three episodes of trivial bleeding and two episodes of significant bleeding for dalteparin, and there were three episodes of trivial bleeding and four episodes of significant bleeding for heparin (p = .53, chi-square test). The mean (SE) decrease in hemoglobin concentration during hemofiltration was 0.51 (0.54) g/dL for heparin and 0.28 (0.49) g/dL for dalteparin (p = .75, unpaired Student's t-test). The mean (SE) packed-cell transfusion volume during hemofiltration was 309 (128) mL for heparin and 290 (87) mL for dalteparin (p = .90, unpaired Student's t-test). Daily costs, including coagulation assays, of hemofiltration were approximately 10% higher using dalteparin than with heparin.

CONCLUSIONS

Fixed-dose dalteparin provided identical filter life, comparable safety, but increased total daily cost compared with adjusted-dose heparin. Unfractionated heparin remains our anticoagulant of choice for continuous hemofiltration in intensive care.

Comparison of low-molecular-weight heparin, administered primarily at home, with unfractionated heparin, administered in hospital, and subcutaneous heparin, administered at home for deep-vein thrombosis

In this study, 294 patients with acute proximal DVT (deep venous thrombosis) were randomly assigned to receive intravenous standard heparin in the hospital (98 patients) or low-molecular-weight heparin (LMWH) (nadroparin 0.1 mL [equivalent to 100 AXa IU] per kg of body weight subcutaneously twice daily) administered primarily at home (outpatients) or alternatively in hospital (97 patients) or subcutaneous calcium heparin (SCHep) (99 patients, 0.5 mL bid) administered directly at home. The study design allowed outpatients taking LMWH heparin to go home immediately and hospitalized patients taking LMWH to be discharged early. Patients treated with standard heparin or LMWH received the oral anticoagulant starting on the second day, and heparin was discontinued when the therapeutic range (INR 2-3) had been reached. Anticoagulant treatment was maintained for 3 months. Patients treated with SCHep were injected twice daily for 3 months without oral anticoagulants. Patients were evaluated for inclusion and follow-up with color duplex scanning. Venography was not used. In case of suspected pulmonary embolism (PE) a ventilatory-perfusional lung scan was performed. Endpoints of the study were recurrent or extension of DVT, bleeding, the number of days spent in hospital, and costs of treatments. Of the 325 patients included, 294 completed the study. Dropouts totaled 31 (10.5%); six of the 325 included patients (1.8%) died from the related, neoplastic illness. Recurrence or extension of DVT was observed in 6.1% of patients in the LMWH group, in 6.2% in the standard heparin group, and in 7.1% in the SCHep group. Most recurrences (11/17) were in the first month in all groups. Bleedings were all minor, mostly during hospital stay. Hospital stay in patients treated with LMWH was 1.2+/-1.4 days in comparison with 5.4+/-1.2 in those treated with standard heparin. There was no hospital stay in the SCHep group. Average treatment costs in 3 months in the standard heparin group (US $2,760) were considered to be 100%; in comparison costs in the LMWH group was 28% of the standard heparin and 8% in the SCHep group. This study indicated that LMWH and SCHep can be used safely and effectively to treat patients with proximal DVT at home at a lower cost.

Long-term outpatient dalteparin (fragmin) therapy for arterial and venous thrombosis: efficacy and safety--a preliminary report

The availability of low molecular weight heparin (LMWH), with associated ease of home delivery and enhanced efficacy and safety, has rendered the long-term outpatient use of LMWH feasible. Although warfarin is usually used for long-term secondary prevention, it is not the drug of choice for a variety of conditions such as antiphospholipid thrombosis syndrome, sticky platelet syndrome, and patients with malignancy and other medical conditions who have failed adequate warfarin doses. We assessed the long-term efficacy and safety of outpatient dalteparin in a series of patients with conditions associated with prior warfarin failure or potential to warfarin therapy (antiphospholipid syndrome). The results of this study, detailed herein, demonstrate that long-term dalteparin is highly effective and safe when used as long-term therapy for secondary prevention in selected prothrombotic disorders.

Low molecular weight heparin in acute coronary syndromes

Traditionally, unfractionated heparin has played an important role in the treatment of acute coronary syndromes. Low molecular weight heparin (LMWH), is a promising new type of heparin, which is fractionated to include only heparin molecules of lower molecular weight. LMWHs are administered subcutaneously and do not require monitoring of the activated partial thromboplastin time, making them much easier to use. LMWHs are combined inhibitors of both thrombin and Factor Xa inhibitors. Several recent large trials in unstable angina and non-Q wave myocardial infarction have shown that LMWH is effective, and one agent has been shown to be superior to unfractionated heparin in reducing death, myocardial infarction, or recurrent angina. They also are very low cost (approximately $50 per day) and appear to be very cost effective in the treatment of unstable angina. Thus, LMWHs appear to be the new anticoagulant agent in acute coronary syndromes.

Venographic comparison of subcutaneous low-molecular weight heparin with oral anticoagulant therapy in the long-term treatment of deep venous thrombosis

PURPOSE

The primary objective of this study was to evaluate with venography the rate of thrombus regression after a fixed dose of low-molecular weight heparin (LMWH) per day for 3 months compared with oral anticoagulant therapy for deep venous thrombosis (DVT). Secondary endpoints were the comparisons of the efficacy and safety of both treatments.

METHODS

This study was designed as an open randomized clinical study in a university hospital setting. Of the 165 patients finally enrolled in the study, 85 were assigned LMWH therapy and 80 were assigned oral anticoagulant therapy. In the group randomized to oral anticoagulant therapy, the patients first underwent treatment in the hospital with standard unfractionated heparin and then coumarin for 3 months. Doses were adjusted with laboratory monitoring to maintain the international normalized ratio between 2.0 and 3.0. Patients in the LMWH group were administered subcutaneous injections of fixed doses of 40 mg enoxaparin (4000 anti-Xa units) every 12 hours for 7 days, and after discharge from the hospital, they were administered 40 mg enoxaparin once daily at fixed doses for 3 months without a laboratory control assay. A quantitative venographic score (Marder score) was used to assess the extent of the venous thrombosis, with 0 points indicating no DVT and 40 points indicating total occlusion of all deep veins. The rate of thrombus reduction was defined as the difference in quantitative venographic scores after termination of LMWH or coumarin therapy as compared with the scores obtained on the initial venographic results. The efficacy was defined as the ability to prevent symptomatic extension or recurrence of venous thromboembolism (documented with venograms or serial lung scans). The safety was defined as the occurrence of hemorrhages.

RESULTS

After 3 months of treatment, the mean Marder score was significantly decreased in both groups in comparison with the baseline score, although the effect of therapy was significantly better after LMWH therapy (49.4% reduction) than after coumarin therapy (24.5% reduction; P <.001). LMWH therapy and male gender were independently associated with an enhanced resolution of the thrombus. A lower frequency of symptomatic recurrent venous thromboembolism was also shown in patients who underwent treatment with LMWH therapy (9.5%) than with oral anticoagulant therapy (23.7%; P <.05), although this difference was entirely a result of recurrence of DVT. Bleeding complications were significantly fewer in the LMWH group than in the coumarin group (1. 1% vs 10%; P <.05). This difference was caused by minor hemorrhages. Coumarin therapy and cancer were independently associated with an enhanced risk of complications. Subcutaneous heparin therapy was well tolerated by all patients.

CONCLUSION

The patients who were allocated to undergo enoxaparin therapy had a significantly greater improvement in their quantitative venographic score, a significantly lower recurrence rate of symptomatic venous thromboembolism, and a significantly lower incidence of bleeding than patients who underwent treatment with coumarin. LMWH can be used on an outpatient basis as a safer and more effective alternative to classical oral anticoagulant therapy for the secondary prophylaxis of selected patients with DVT.

Treatment and prevention of venous thromboembolic disease in pregnancy

Pulmonary embolism is a major, but potentially preventable, cause of maternal mortality in North America and Europe. Because venous thromboembolism is an infrequent cause of maternal morbidity, there are few randomized clinical trials to guide clinical decision-making with respect to treatment, prevention, and evaluation of innovative management modalities such as low molecular weight heparin. This article focuses on the evidence supporting the current guidelines for the pharmacologic management of venous thromboembolic disease in pregnancy.

Heparin and low molecular weight heparin for treatment of acute pulmonary embolism

Pulmonary embolism occurs in more than 175,000 patients each year in the United States. The objectives of treatment are to prevent death from the existing embolus, to prevent death and morbidity from recurrent pulmonary embolism, and to prevent morbidity from recurrent deep-vein thrombosis. For patients with adequate cardiorespiratory reserve, the primary objective is to prevent recurrent pulmonary embolism. Anticoagulant therapy with intravenous unfractionated heparin or subcutaneous low molecular weight heparin followed by oral anticoagulant treatment for at least 3 months is the treatment of choice for most of these patients. Clinical trials indicate that the effectiveness of intravenous heparin depends on achieving an adequate heparin effect (activated partial thromboplastin time above lower limit) during the initial 24 hours. A validated protocol for intravenous heparin should be used to lessen the likelihood of delayed heparinization. Low molecular weight heparin given subcutaneously either once or twice daily is as effective as intravenous heparin for the treatment of patients with deep-vein thrombosis and submassive pulmonary embolism. Low molecular weight heparin enables many patients with uncomplicated deep-vein thrombosis to be treated in an outpatient setting.

Large amounts of vascular endothelial growth factor at the site of hemostatic plug formation in vivo

Vascular endothelial growth factor (VEGF) is important for the proliferation, differentiation, and survival of microvascular endothelial cells. It is a potent angiogenic factor and a specific endothelial cell mitogen that increases fenestration and extravasation of plasma macromolecules. Recently, large quantities of VEGF were detected in human megakaryocytes. Incubation of human platelets with thrombin in vitro resulted in the release of large amounts of VEGF. To investigate whether VEGF is released from platelets during coagulation activation in vivo, we measured in human subjects VEGF at the site of plug formation, ie, in blood emerging from a standardized injury made to determine bleeding time (shed blood). VEGF was also determined in the same volunteers after treatment with the specific thrombin inhibitor recombinant hirudin (r-hirudin). In a double-blind, randomized, crossover study, 17 healthy male volunteers (aged 20 to 35 years) were investigated. VEGF concentrations were measured in venous blood and in shed blood by the use of an immunoassay 10 minutes after intravenous administration of r-hirudin (0.35 mg/kg of body weight) or physiological saline. Prothrombin fragment f1.2 (f1.2) and beta-thromboglobulin (beta-TG) were determined as indicators of coagulation and platelet activation, respectively. Concentrations of VEGF, f1.2, and beta-TG in shed blood 4 minutes after injury were significantly higher than in venous blood (VEGF, 55.8+/-9.2 versus <20 pg/mL, P<0.001; f1.2, 71.3+/-10.4 versus 0.78+/-0.03 nmol/L, P<0. 001; beta-TG, 2290+/-170 versus 53.2+/-14.0 ng/mL, P<0.001). Administration of r-hirudin caused a >50% inhibition of the beta-TG and f1.2 levels in shed blood. In a similar manner, much lower amounts of VEGF were detectable at the site of plug formation after r-hirudin treatment (69.0+/-9.5 versus 37.8+/-2.6 pg/mL per minute; P=0.0015). Our data indicate that substantial quantities of VEGF are released from platelets during the interaction with the injured vessel wall in vivo. This finding may be relevant with respect to wound healing and tissue repair, tumor vascularization, or arterial thrombus formation.

Calf-thigh sequential pneumatic compression compared with plantar venous pneumatic compression to prevent deep-vein thrombosis after non-lower extremity trauma

OBJECTIVE

To compare the effectiveness of calf-thigh sequential pneumatic compression devices with the effectiveness of plantar venous intermittent pneumatic compression devices in prevention of venous thrombosis after major trauma.

SUBJECTS AND METHODS

We evaluated 181 consecutive patients after major trauma without lower extremity injuries that precluded the use of pneumatic compression devices. We randomly assigned 149 patients to either calf-thigh sequential pneumatic compression or plantar venous pneumatic compression. After blinding the observers to the method of prophylaxis against deep-vein thrombosis, we performed bilateral compression ultrasonography on or before day 8 after randomization.

RESULTS

Among 149 randomized patients, 62 who received calf-thigh sequential pneumatic compression and 62 who received plantar venous intermittent pneumatic compression devices completed the trial. Thirteen patients randomized to plantar venous intermittent pneumatic compression (21.0%) and 4 patients randomized to calf-thigh sequential pneumatic compression (6.5%) had deep-vein thrombosis (p = 0.009). Seven of 13 patients with deep-vein thrombosis after prophylaxis with plantar venous intermittent pneumatic compression had bilateral deep-vein thromboses, whereas all 4 patients with deep-vein thrombosis after prophylaxis with calf-thigh sequential pneumatic compression had unilateral deep-vein thrombosis.

CONCLUSION

Calf-thigh sequential pneumatic compression prevents deep-vein thrombosis more effectively than plantar venous intermittent pneumatic compression after major trauma without lower extremity injuries.

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.

Electrochemical sensors for polyionic macromolecules: development and applications in pharmaceutical research

The first electrochemical sensors responsive towards polyionic heparin and protamine - two clinically important polymeric drugs - have been fully developed. The response mechanism of these sensors has been completely elucidated. As well as their significance in measuring blood heparin levels in clinically relevant concentration ranges, these polyion sensors could also find broad applications in pharmaceutical research, such as in the study of the binding events between heparin (or protamine) and other polycationic (or polyanionic) macromolecules. In addition, the sensors could be employed in the design of blood assays for a range of clinically important proteases and their inhibitors by utilizing either protamine or specially designed synthetic polypeptides as the substrates

Occurrence of thrombosis and haemorrhage, relationship with anti-Xa, anti-IIa activities, and D-dimer plasma levels in patients receiving a low molecular weight heparin, enoxaparin or tinzaparin, to prevent deep vein thrombosis after hip surgery

Studies in experimental animal models and in patients receiving low molecular weight heparin (LMWH) to prevent thromboembolic events after surgery have not demonstrated a clear relationship between anti-Xa and anti-IIa activities in plasma and either bleeding or prevention of thrombosis. The relationship between these clinical outcomes and ex vivo anti-Xa and anti-IIa activities, activated partial thromboplastin time (APTT) and D-dimers were evaluated in 440 patients undergoing total hip replacement and given prophylaxis once daily with a LMWH (tinzaparin or enoxaparin) in a multicentre double-blind randomized study. 221 patients received 4500 anti-Xa IU of tinzaparin; 219 patients received 40 mg (4000 anti-Xa IU) of enoxaparin. Both regimens were administered subcutaneously once daily. Blood samples for anti-IIa, anti-Xa, D-dimers levels and APTT were taken at baseline, on day 1, day 5 and on the day of discharge (days 8-14) and clinical assessments were performed dafly until day 14. All patients had bilateral venography between days 8 and 14. All coagulation tests were performed in central laboratories. A significant correlation was observed between anti-IIa activity and anti-Xa activity and the dose of each LMWH injected. The anti-Xa activity was significantly higher with enoxaparin and the anti-IIa activity was significantly higher with tinzaparin. No clear relationship between these two activities and the clinical outcomes was observed. This was also true with regards to APTT. Before and after surgery, D-dimers were significantly higher in patients with deep vein thrombosis (DVT) than in those without DVT but had no predictive value. Interestingly, a significant post-operative increase of D-dimers persisted in both groups of patients during the whole observation period, possibly suggesting that a longer duration of prophylactic treatment may be appropriate.

Current Clinical Practice: Low-Molecular-Weight Heparins in The Prophylaxis and Treatment of Thrombo-Embolic Disease

Low-Molecular-Weight Heparin (LMWH) fractions are prepared from standard unfractionated heparin (UFH) and are thus similar to it in many aspects. The major advantages of LMWH are improved efficacy and safety, longer half-life and reduced need for laboratory monitoring. In addition, the dangers of UFH administered by continuous infusion in the hospital setting are often not fully appreciated and the necessary monitoring and dosage adjustment poorly carried out resulting in inadequate doses being given. LMWHs are the drug of choice in many clinical situations. Four LMWHs are now licensed in the UK for prophylaxis of venous thrombo-embolism during or after surgery (Certoparin, Dalteparin [Fragmin], Enoxaparin [Lovenox/Clexane] and Tinzaparin [Inno-hep]; a fifth is licensed but not currently available in the UK. Dalteparin, Enoxaparin and Tinzaparin are licensed for the treatment of Deep Vein Thrombosis (DVT), and Tinzaparin additionally for the treatment of Pulmonary Embolism (PE), but so far none is licensed for use in pregnancy or paediatrics.

Venous thrombosis: diagnosis and treatment; new methods and strategies for management

Venous thrombosis most often attacks patients who have had alterations of venous stasis, endothelial damage, and/or hypercoagulability. Diagnosis generally depends on venography or duplex doppler ultrasonography; treatment is usually started with heparin and may proceed to warfarin alone.

Low molecular weight heparins: current use and indications

Thromboembolic complications are associated with significant morbidity and mortality in postoperative patients. For many years, unfractionated heparin has been used successfully in primary and secondary prophylaxis of these complications. In recent times, however, the usefulness of LMWHs has caught the attention of clinicians because of improved bioavailability, predictable anticoagulation, ease of administration, and the lack of need for monitoring anticoagulation. In clinical situations, LMWHs have been tested and proved to be safe and equipotent or supe rior when compared with unfractionated heparin or warfarin (Table 5). It is clear from clinical trials that LMWHs are superior in primary prophylaxis of DVT in orthopaedic surgical procedures, treatment of unstable angina, and in patients with multiple traumas. LMWHs were also tested and found to be an acceptable alternative to unfractionated heparin in both the primary prophylaxis of DVT in high risk general surgical procedures and in the treatment of patients with DVT and pulmonary embolism. However, the role of LMWHs in ischemic heart diseases, valvular heart diseases, postcoronary angioplasty, and vascular surgery remains to be proved. The major impact of LMWHs would be in allowing clinicians to treat PE and DVT in an outpatient setting, which would directly impact medical economics. LMWHs are associated with similar complications as unfractionated heparin is, but the complications occur less frequently. Currently, the main limitation in using LMWHs in place of unfractionated heparin or warfarin is its cost. However, taking into account the cost incurred by hospitalization and longterm monitoring of anticoagulation in patients treated with unfractionated heparin, certain trials have proved the cost of LMWHs to be the same or less than the cost of unfractionated heparin overall. We envision that LMWHs will be widely used in the future and will bring welcomed change in the treatment of thromboembolic diseases.

Low-molecular-weight heparins

Low-molecular-weight heparins (LMWH) are a new group of parenteral anticoagulants. They represent a major clinical advance in anticoagulation since the identification of unfractionated heparin (UFH) in 1922 and the introduction of the synthetic coumarin derivative, warfarin, in 1948. Their predictable pharmacokinetics, increased bioavailability, and longer plasma half-life allow for once- or twice-daily dosing and eliminate the need for routine laboratory monitoring. This simplified administration stands to alter the clinical practice of anticoagulation. This review high-lights recent clinical trials and focuses on studies comparing LMWH with the other two major anticoagulants: UFH and coumadin.

Use of antithrombotic agents during pregnancy

Anticoagulant therapy is indicated during pregnancy for the prevention and treatment of VTE, for the prevention and treatment of systemic embolism in patients with mechanical heart valves, and, in combination with aspirin, for the prevention of pregnancy loss in women with APLA and previous pregnancy losses. Several questions concerning anticoagulant therapy remain unanswered. Oral anticoagulants are fetopathic, but the true risks of the warfarin embryopathy and CNS abnormalities are unknown. There is some evidence that warfarin embryopathy occurs only when oral anticoagulants are administered between the 6th and the 12th weeks of gestation and that oral anticoagulants may not be fetopathic when administered in the first 6 weeks of gestation. Oral anticoagulant therapy should be avoided in the weeks before delivery because of the risk of serious perinatal bleeding caused by the trauma of delivery to the anticoagulated fetus. The safety of aspirin during the first trimester of pregnancy is still a subject of debate. There is a concern about the efficacy of unfractionated heparin in the prevention of arterial embolism in pregnant women with mechanical heart valves. Finally, the role of LMWH and heparinoids and appropriate dosing have still to be determined. Because it is safe for the fetus, heparin is the anticoagulant of choice during pregnancy for situations in which its efficacy is established. The evidence for the efficacy of heparin for the prevention and treatment of VTE disorders during pregnancy is based on level IV studies. There is some doubt that heparin is effective for the prevention of systemic embolism in patients with mechanical heart valves. Low doses of heparin or poorly controlled heparin therapy are not effective in preventing systemic embolism in patients with mechanical heart valves.

Low-molecular-weight heparins in non-ST-segment elevation ischemia: the ESSENCE trial. Efficacy and Safety of Subcutaneous Enoxaparin versus intravenous unfractionated heparin, in non-Q-wave Coronary Events

Combination antithrombotic therapy with heparin plus aspirin decreases the risk of recurrent ischemic events in patients with acute coronary syndromes without persistent ST-segment elevation. Compared with standard unfractionated heparin, low-molecular-weight heparin (LMWH) has a more predictable antithrombotic effect, is easier to administer, and does not require coagulation monitoring. At 176 hospitals in 3 continents, 3,171 patients with rest unstable angina or non-wave myocardial infarction were randomly assigned to either enoxaparin (a LMWH), 1 mg/kg twice daily subcutaneously, or to continuous intravenous unfractionated heparin, for a minimum of 48 hours to a maximum of 8 days. Trial medication was administered in a double-blind, placebo-controlled fashion. At 14 days, the primary endpoint, the composite risk of death, myocardial infarction, or recurrent angina with electrocardiographic changes or prompting intervention, was significantly lower in patients assigned to enoxaparin compared with heparin (16.6% vs 19.8%; odds ratio [OR] 1.24; 95% confidence interval [CI] 1.04-1.49; p = 0.019). At 30 days, the composite risk of death, myocardial infarction, or recurrent angina remained significantly lower in the enoxaparin group compared with the unfractionated heparin group (19.8% vs 23.3%, OR 1.23; 95% CI 1.0-1.46, p = 0.016). The rate of revascularization procedures at 30 days was also significantly lower in patients assigned to enoxaparin (27.1% vs 32.2%, p = 0.001). The 30-day incidence of major bleeding complication was 6.5% versus 7.0% (p = not significant), but the incidence of minor bleeding was significantly higher in the enoxaparin group (13.8% vs 8.8%, p <0.001) due primarily to injection-site ecchymosis. Thus, combination antithrombotic therapy with enoxaparin plus aspirin is more effective than unfractionated heparin plus aspirin in decreasing ischemic outcomes in patients with unstable angina or non-Q-wave myocardial infarction in the early (30 days) phase. The lower recurrent ischemic event rate seen with the LMWH, enoxaparin, is achieved without an increase in major bleeding, but with an increase in minor bleeding complications due mainly to injection-site ecchymosis.

Heparin and low-molecular-weight heparin in the treatment of venous thromboembolism

Venous thromboembolism (deep vein thrombosis and pulmonary embolism) continues to constitute a major clinical challenge. Effective and safe prophylactic measures against venous thromboembolism are now available for most high risk patients. In spite of this, pulmonary embolism is responsible for approximately 150,000 to 200,000 deaths per year in the United States alone. Over the past 20 years, based on a number of high quality (Level I) clinical trials, patterns of practice with respect to the treatment of venous thromboembolism have changed dramatically. The standard treatment of venous thromboembolism has been the use of unfractionated heparin by continuous intravenous infusion, with laboratory monitoring using the activated partial thromboplastin time (APTT), with warfarin starting on day 1 or 2 and continued for 3 months. Unfractionated heparin has withstood the test of time and has been shown to be safe and effective in preventing recurrent venous thromboembolism and death in numerous clinical trials. The response of individual patients to heparin is highly variable, requiring frequent laboratory monitoring. Heparin has a number of other troublesome side effects including bleeding, heparin-induced thrombocytopenia and osteoporosis. The low-molecular-weight heparins have a number of advantages over unfractionated heparin. In particular, their increased bio-availability and prolonged half-life permit once daily subcutaneous injections and their predictable antithrombotic response based on body weight permits treatment without laboratory monitoring. Low-molecular-weight heparin in therapeutic doses causes less bleeding than unfractionated heparin and evidence is accumulating that the incidence of heparin-induced thrombocytopenia and osteoporosis are decreased as well. In individual clinical trials and meta-analyses, low-molecular-weight heparin treatment results in decreased recurrent thromboembolism, major bleeding and death when compared with unfractionated heparin in the treatment of deep vein thrombosis and pulmonary embolism. These agents have also been shown to be both effective and safe for the out-of-hospital treatment of venous thrombosis. Therefore, in many countries, low-molecular-weight heparin has replaced unfractionated heparin for the treatment of venous thromboembolism.

Outpatient management of deep vein thrombosis

OBJECTIVE

To assess whether patients with deep vein thrombosis (DVT) could be satisfactorily treated on an outpatient basis with low molecular weight (LMW) heparin and warfarin.

DESIGN

A 22 month prospective study of adults attending St Peter's Hospital accident and emergency department with DVT.

RESULTS

1093 patients were referred and assessed; 160 were venogram positive, of which 159 patients between the ages of 22 and 89 years of age have now been treated with LMW heparin as outpatients. Direct liaison with community nurses has minimised the impact on general practitioner workload.

CONCLUSIONS

1272 bed days were saved during this period (an estimated 320,000 pounds). The outpatient treatment of thromboembolism has been shown to be effective and safe.

Venous thromboembolism and cancer

The association of thrombosis with malignant disease has been recognized for well over 100 years. Evidence from experimental and clinical studies indicates that the haemostatic system is involved in the growth, invasion and metastasis of tumours. Laboratory parameters of haemostasis are frequently deranged in patients with cancer and overt thrombosis is common spontaneously where it may be the first sign of malignancy or secondary to therapy. The mechanisms by which coagulation activation facilitates the malignant process remain to be completely elucidated, but it is clear that cells and proteins of the coagulation and fibrinolytic systems are involved at many steps in the processes of tumour growth and dissemination. The low-molecular-weight heparins with their well-proven safety and efficacy profiles offer unique modalities for the prevention and treatment of cancer-associated thrombosis. They may also play a role in overall mortality reduction in patients with malignant disease.

Dose titration study of tinzaparin, a low molecular weight heparin, in patients on chronic hemodialysis

The minimal necessary dose of Innohep (IH) (MNDI) (Innohep [tinzaparin], Leo Pharmaceutical Corp., Ballerup, Denmark) was examined in 40 patients switched from conventional heparin ([CH], Leo Pharmaceutical Corp.) to IH and in 13 patients already treated with IH. Clotting in the venous chamber and in the dialyzer was evaluated on a 4 point scale by visual inspection. IH was administrated as a bolus injection into the arterial side of the dialyzer at the beginning of dialysis sessions. The initial dose of IH was 50% of the total dose of CH used before the study (in respective IU). According to clotting in the venous chamber or dialyzer, the dose of IH was titrated by stepwise changes of 500 IU to the lowest possible dose until 3 subsequent dialysis sessions without clotting were obtained. The total dose of CH (bolus and infusion) before switching was 6,162 +/- 2,100 IU. The bleeding time from the cannulation site after dialysis, in 24 patients with A-V fistulas, was 7.1 +/- 2.8 min(triplicates). Eight patients were excluded before achieving the MNDI, 3 due to bleeding not clearly related to heparinization (1 due to gingival bleeding, 1 to epistaxis, and 1 to sugillations), 1 due to alopecia, 2 due to a need of more than 10,000 IU of IH, and 2 patients due to cessation of treatment resulting from anxiety. After switching over, the MNDI amounted to 66 +/- 26% in respective IU. The conversion IH/CH ratio correlated significantly to the blood flow rate and the type of dialyzer. When compared on 3 subsequent sessions before and after switching to IH, no differences were found in the bleeding time after decannulation and in clotting in the venous chamber while dialyzer clotting fell on the visual scale from an average of 0.36 to 0.19 (p < 0.01). No total clot formation was observed during the study. The MNDI correlated positively to the body weight, blood flow rate, and time on dialysis (with the respective coefficients of correlation of r being 0.58, 0.44, and 0.30, p < 0.05) and was also influenced by the type of dialyzer. The average MNDIs for the Hemoflow-FS hollow-fiber (Fresenius, Bad Homburg, Germany), Lundia PRO plate (Gambro, Lund, Sweden), and Polyflux hollow fiber (Gambro) were 2,571, 3,727, and 5,020 IU (p < 0.01, ANOVA). In patients on chronic hemodialysis, IH given as a bolus of 4,250 IU effectively prevented extracorporeal clotting during dialysis, similarly to CH. However, a considerable individual variation in MNDIs not related to the need for CH was observed, and this necessitates individual dosage adjustments to obtain the optimal prevention of clotting with minimal bleeding risk.

Unfractionated versus low-molecular-weight heparin in the treatment of venous thromboembolism

Low-molecular-weight heparin (LMWH) fractions are prepared from standard unfractionated heparin (UFH) and are thus similar to UFH in many aspects. The main advantages of this new class of antithrombotic agents as compared with UFH are: (1) an improved bioavailability and a prolonged half-life, which alleviate cumbersome laboratory monitoring and may permit one single daily subcutaneous injection; and (2) an improved efficacy-to-safety ratio, with less bleeding despite similar or improved efficacy. For these reasons, LMWH is progressively replacing UFH for preventing postoperative thromboembolism and for treating established deep vein thrombosis and pulmonary embolism. However, the effects of the new compounds need to be evaluated carefully in some other indications (arterial thrombosis, unstable angina, or myocardial infarction-the latter also in conjunction with thrombolytic treatment) before they can generally replace UFH in pharmacotherapy.

Long-term outcomes after deep venous thrombosis of the lower extremities

Few natural history studies are available which describe long-term outcomes after venous thromboembolism. However, symptomatic deep-vein thrombosis (DVT) of the lower extremities carries a high risk for recurrent venous thromboembolism that persists for many years. This risk is higher among patients with permanent risk factors including inherited abnormalities of hemostasis than among patients who have suffered trauma or who are postoperative. The development of recurrent ipsilateral DVT carries a high risk for severe post-thrombotic syndrome, an otherwise rare problem in patients with a first episode of DVT adequately treated with anticoagulant drugs and wearing vascular compression stockings. Long-term survival following DVT is generally good in the absence of malignancy. Carefully designed randomized trials are needed to determine whether chronic anticoagulation can reduce further the risks of recurrent DVT and symptoms of post-thrombotic syndrome.

New approaches to the delivery of anticoagulant services

Anticoagulant services are changing in response to the increasing demands on the service. New approaches to the delivery of the service are evolving with more local delivery of services and a shift in the service from secondary to primary care. This change has been assisted by the development of near patient testing devices and the use of computerized anticoagulant decision support systems that are increasingly used in both secondary and primary care. The evolving role of the clinical nurse/pharmacist in the provision of this service is an important development enabling more rapid discharge of patients and the provision of local delivery of service.