LMWH for Perioperative Anticoagulation in Patients on Chronic Warfarin Therapy

OBJECTIVE:

To review current data regarding low-molecular-weight heparin (LMWH) use for perioperative anticoagulation in patients receiving chronic warfarin therapy.

DATA SOURCES:

Data were obtained from the Sixth American College of Chest Physicians Consensus Conference on Antithrombotic Therapy guidelines and a MEDLINE search (1996-January 2003). Search terms included heparin, low-molecular-weight heparin, warfarin, perioperative care, and anticoagulants.

DATA SYNTHESIS:

Heparin is the most common agent used as bridge therapy for perioperative anticoagulation in patients on chronic warfarin therapy; LMWHs are also used. Studies that evaluated enoxaparin and/or dalteparin were reviewed.

CONCLUSIONS:

Although published studies demonstrate efficacy and safety of LMWHs, more data are needed to support their use as bridge therapy.

Subcutaneous Adjusted-Dose Unfractionated Heparin vs Fixed-Dose Low-Molecular-Weight Heparin in the Initial Treatment of Venous Thromboembolism

BACKGROUND

Few reports have addressed the value of unfractionated heparin (UFH) or low-molecular-weight heparin in treating the full spectrum of patients with venous thromboembolism (VTE), including recurrent VTE and pulmonary embolism.

METHODS

In an open, multicenter clinical trial, 720 consecutive patients with acute symptomatic VTE, including 119 noncritically ill patients (16.5%) with pulmonary embolism and 102 (14.2%) with recurrent VTE, were randomly assigned to treatment with subcutaneous UFH with dose adjusted by activated partial thromboplastin time by means of a weight-based algorithm (preceded by an intravenous loading dose), or fixed-dose (adjusted only to body weight) subcutaneous nadroparin calcium. Oral anticoagulant therapy was started concomitantly and continued for at least 3 months. We recorded the incidence of major bleeding during the initial heparin treatment and that of recurrent VTE and death during 3 months of follow-up.

RESULTS

Fifteen (4.2%) of the 360 patients assigned to UFH had recurrent thromboembolic events, as compared with 14 (3.9%) of the 360 patients assigned to nadroparin (absolute difference between rates, 0.3%; 95% confidence interval, -2.5% to 3.1%). Four patients assigned to UFH (1.1%) and 3 patients assigned to nadroparin (0.8%) had episodes of major bleeding (absolute difference between rates, 0.3%; 95% confidence interval, -1.2% to 1.7%). Overall mortality was 3.3% in each group.

CONCLUSIONS

Subcutaneous UFH with dose adjusted by activated partial thromboplastin time by means of a weight-based algorithm is as effective and safe as fixed-dose nadroparin for the initial treatment of patients with VTE, including those with pulmonary embolism and recurrent VTE.

The safety of antithrombotic therapy during pregnancy

A number of clinical conditions can require the use of antithrombotic drugs during pregnancy. These mainly include prevention of venous thromboembolism (VTE) and fetal complications in high-risk patients, treatment of VTE and prevention of arterial emboli in patients with mechanical heart valve prostheses. However, there are several problems when using antithrombotic drugs during pregnancy. Warfarin, as well as the other coumarin compounds, crosses the placenta and has the potential to cause both bleeding in the fetus and teratogenicity, therefore its use is not recommended during the first trimester and during the perinatal period. Unfractionated heparin (UFH) and low molecular weight heparin (LMWH) do not cross the placenta and are safe for the fetus, but long-term treatment with UFH is problematic because of its inconvenient administration, the need to monitor anticoagulant activity and because of its potential side effects, such as heparin-induced thrombocytopenia and osteoporosis. LMWH is the drug of choice in the prevention and treatment of VTE during pregnancy because of its practical advantages over UFH and because of a lower risk of side effects. Patients with mechanical heart valve prostheses represent a major clinical challenge. Warfarin, the drug of choice in non-pregnant women, can be administered between the 12th and 36th week. Full-dose UFH is recommended in the first trimester and after week 36. The use of LMWH as an alternative to UFH is still a matter of debate, because inadequate data are available.

Thromboembolic Prophylaxis as a Risk Factor for Postoperative Complications after Breast Cancer Surgery

Hematoma and bruising (sugillation) are frequent problems after operations for primary breast cancer. In the present study we evaluated the influence of various methods of perioperative thromboembolic prophylaxis on the postoperative incidence of hematoma and suggilation. From June 1994 through August 1996, a series of 425 patients consecutively operated on for primary breast cancer were included. Thromboembolic prophylaxis was low-molecular-weight heparin (LMWH) in 310 patients and thigh-long graded compression (TED) stockings in 102 patients. Postoperative complications including deep vein thrombosis, pulmonary embolism, wound hematoma, and sugillation were recorded, and 17 variables with a potential influence on complications were analyzed by logistic regression analysis. Heparin prophylaxis compared to prophylaxis with TED stockings was significantly and independently associated with postoperative hematoma [odds ratio (OR) 3, 13; 95% confidence interval (CI) 1.38-7.13] or sugillation (OR 3.34; 95% CI 1.93-5.78). No clinically overt thromboembolic complications were diagnosed. After operations for breast cancer we found that LMWH was significantly associated with postoperative hematoma and sugillation compared to TED stockings for perioperative thromboembolic prophylaxis.

Low-molecular-weight heparin (LMWH) in the treatment of thrombosis

Thromboembolic complications are a common and costly medical problem, associated with significant morbidity and mortality, especially in postoperative patients. There have been reports of death due to thromboembolic complications even after short procedures, e.g. arthroscopy. Low-molecular-weight heparins (LMWHs) (e.g., certoparin, dalteparin, enoxaparin, nadroparin, reviparin, tinzaparin) have been tested for treatment of deep vein thrombosis in comparison to unfractionated heparin (UFH) in many patients being effective and safe alternative for treatment of deep vein thrombosis (DVT) and venous thromboembolism (VTE). Fixed-dose subcutaneous LMWH once daily is in most cases of equivalent efficacy and safety compared to conventional UFH therapy. There may be less risk for bleeding, less platelet activation together with a control of markers of haemostatic system activation, and either no progression or regression of thrombus size in patients treated with LMWH. The handling of LMWH is more comfortable for patients and less time consuming for nurses and laboratories compared to UFH. The cost-effectiveness analysis showed that LMWH are more cost effective than UFH. It has been calculated that outpatient treatment with LMWH may save 1641 dollars per patient in comparison to hospital treatment. This economic benefit of outpatient treatment of DVT seems to be realized in different health systems. Women with antiphospholipid antibodies and a history of either prior thrombotic events or pregnancy loss are at high risk during pregnancy for either another fetal death or thrombosis and may benefit from treatment with LMWH. In patients with malignant tumors secondary prophylaxis or long-term treatment with LMWH is successful. Patients with a contraindication for oral anticoagulants may benefit from treatment with LMWH as do patients on chronic anticoagulation treatment scheduled for an operative intervention. In most instances LMWH (dalteparin, enoxaparin, nadroparin) treatment for DVT may be given once daily at a fixed dose without any harm, based on a prolonged antithrombin activity. Effectiveness and safety of LMWH (dalteparin, enoxaparin, nadroparin, tinzaparin) in comparison to UFH treatment on outpatient basis has been demonstrated in several studies. In summary, LMWHs have an established role in the treatment of DVT and pulmonary embolism (PE), on an in- and outpatient basis and could realize substantial savings. Most studies were performed with dalteparin, enoxaparin and nadroparin. There is evidence that LMWHs may help to prolong survival in cancer patients and to avoid complications of the acute coronary syndrome.

Pathophysiology, epidemiology, diagnosis and treatment of heparin-induced thrombocytopenia (HIT)

Due to the widespread use of unfractionated (UFH) and low molecular weight heparins (LWH) for prophylaxis and treatment of thrombosis, heparin-induced thrombocytopenia is considered to be the most frequent (and potentially the most devastating) drug-induced thrombocytopenia. Induced by an immune response, excessive activation of platelets and endothelium cells causes massive thrombin generation and, as a result, life-threatening venous and arterial thrombotic vessel occlusion. The rate of mortality and amputation in HIT II is estimated to be 30% and 20%, respectively. The clinical course of HIT II depends highly on early therapeutic intervention consisting of immediate interruption of heparin application and, most important, of compatible thrombin inhibition. All measures implying a potentially procoagulant risk such as begin of oral anticoagulation or platelet substitution may result in disastrous side effects.

Skin reactions due to low molecular weight heparin in pregnancy: a strategic dilemma

INTRODUCTION

Heparin-induced allergic reactions may cause problems if heparin administration is needed for thrombo-embolic disease in pregnancy.

CASE REPORTS

We report two cases of hypersensitivity to low molecular weight heparin (LMWH) in pregnancy.

DISCUSSION

Alternative methods and new antithrombotic agents are discussed.

Nursing initiatives for deep vein thrombosis prophylaxis. Pragmatic timing of administration

This review explores the importance of the course of time in the development of deep vein thrombosis and its connection to prophylaxis in total hip replacement, emphasizing the impact on nursing practice. It examines the application of expanded use of low-molecular-weight heparin as an effective option versus warfarin. The principles behind once-daily dosing for prevention of thromboembolic disease in total hip replacement are presented, as well as the benefits of extended prophylaxis. Finally, a series of initiatives provides orthopaedic nurses with an action plan to expand their role in clinical decision-making with other members of the healthcare team.

Low molecular weight heparin (tinzaparin) vs. placebo in the treatment of mild to moderately active ulcerative colitis

BACKGROUND

Heparin has anti-inflammatory and immunomodulatory activity which may be of therapeutic benefit in the treatment of ulcerative colitis.

AIM

To test whether low molecular weight heparin, given subcutaneously, would provide a significant therapeutic response compared with placebo in the treatment of mild to moderate ulcerative colitis.

STUDY DESIGN

A prospective, double-blind, randomized, placebo-controlled, multi-centre trial comparing tinzaparin 175 anti-Xa IU/kg/day (innohep, LEO Pharma) subcutaneously for 14 days followed by tinzaparin 4500 anti-Xa IU/day subcutaneously for 28 days with placebo, administered subcutaneously once daily for up to 42 days. The primary outcome measure was the mean change in colitis activity from baseline to the end of study treatment assessed by the sum of scores of stool frequency, rectal bleeding, sigmoidoscopic appearance and histology. Secondary outcome measures included changes in individual activity indices and laboratory parameters. Patients were assessed at weekly intervals for 6 weeks and within 1 week of completing treatment.

RESULTS

One hundred patients with active ulcerative colitis (up to six bloody stools per day, no fever, no tachycardia or systemic disturbances) were randomized. Forty-eight received tinzaparin and 52 received placebo. The difference in the mean percentage change in colitis activity from baseline to end of treatment (tinzaparin-placebo) was not statistically significant (P = 0.84). There was no difference between tinzaparin and placebo in any secondary outcome measure. One major bleed (rectal), occurred in a patient receiving placebo.

CONCLUSION

This is the largest trial to date of heparin in ulcerative colitis. The results show no benefit of low molecular weight heparin over placebo in mild to moderately active ulcerative colitis.

[Evaluation of predisposing factors for mediastinal bleeding in myocardial revascularization surgery. Role of acetylsalicylic acid, other platelet adhesion inhibitors, and anticoagulants]

OBJECTIVE

To determine the main factors for perioperative mediastinal bleeding during coronary artery by-pass grafting and to establish the role of acetylsalicylic acid, other inhibitors of platelet adhesion, and anticoagulants in its occurrence.

METHODS

A multivariate analysis was performed to the data obtained from 251 patients subjected to coronary artery by-pass grafting in the year 2002.

RESULTS

There were no significant differences for the occurrence of perioperative bleeding induced by the preoperative administration of acetylsalicylic acid. No significant increment in the need for blood, platelet, or cryoprecipitates transfusion existed. Patients receiving non-fractionated or low molecular weight heparin had a significantly greater (p < 0.001) transoperative bleeding than patients without this drug. Administration of the other studied drugs did not increase either mediastinal bleeding or the need for blood derivatives.

CONCLUSIONS

No statistical evidence was found to suspend administration of inhibitors of platelet adhesion in patients with coronary syndromes, subjected to coronary artery by-pass grafting. However, data obtained suggest the convenience of suspending administration of low molecular weight or non-fractionated heparin to patients subjected electively to coronary artery by-pass grafting.

Developing an algorithm for treating heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a serious and common complication of heparin therapy that can lead to significant losses of life and limb. It is often under-recognized and, therefore, goes untreated until thrombosis develops. This article is meant to provide specific recommendations for treating patients with immune-mediated HIT, whether or not it is associated with thrombosis. These recommendations are based on our clinical experience treating patients with HIT and our evaluation of the published data on the efficacy and safety of lepirudin and argatroban, the 2 drugs approved by the Food and Drug Administration for treating HIT. Based on these criteria, we consider lepirudin the treatment of choice in all patients with HIT except those with severe or deteriorating renal function.

Anticoagulation therapy in children

Thromboembolic disease (TED) is increasingly recognized as a major cause of morbidity and mortality in tertiary pediatrics. Children younger than 1 year of age and teenage girls are at greatest risk of thromboembolism. Although anticoagulation therapy is the treatment of choice for TED, the treatment strategy is often difficult, especially in children. Treatment relies largely on anticoagulation with heparin and warfarin. Recommendations for antithrombotic therapy in children have been loosely extrapolated from recommendations for adults; however, it is likely that optimal treatment of children with TED differs from adults because of important ontogenic features of hemostasis that affect both the pathophysiology of the thrombotic processes and the response to antithrombotic agents. Until recently, the primary treatment for TED has been unfractionated heparin (UFH) in conjunction with warfarin. Warfarin, the most commonly used oral anticoagulant, acts through inhibition of the vitamin K-dependent transcarboxylation reactions that convert precursors of clotting factors into their active form. Appropriate use of UFH and warfarin requires close patient monitoring and dosage adjustments to ensure tolerability and efficacy. In recent years, low molecular weight heparins (LMWH) have become available as alternatives to UFH and warfarin, for both the prevention and treatment of TED. Potentially, LMWH have significant advantages. They have superior pharmacokinetics, which results in minimal laboratory monitoring, offering important benefits to children with poor venous access. Based on available data, LMWHs are at least as effective and well tolerated as UFH, and are more convenient. Although LMWHs are more expensive than UFH, the expense is likely to be offset by savings from a reduced hospital stay.