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Biomedical subjects

S M Bates

Publications and source records attributed to S M Bates.

33 records · Page 2Linked to original sources
PubMed2000

The mechanism of action of thrombin inhibitors.

Although heparin is widely used to treat arterial thrombosis, it has limitations in this setting. These limitations reflect heparin's inability to inactivate fibrin-bound thrombin, a major stimulus for thrombus growth, and the fact that heparin is neutralized by platelet factor 4, large quantities of which are released from platelets at the site of plaque rupture. Heparin also has a propensity to bind non-specifically to other plasma proteins. Because plasma levels of these heparin-binding proteins vary from patient to patient, the anticoagulant response to heparin is unpredictable and careful laboratory monitoring is necessary to ensure that an adequate anticoagulant effect is achieved. Direct thrombin inhibitors, such as bivalirudin and hirudin, overcome many of the limitations of heparin. These agents inhibit fibrin-bound thrombin, as well as fluid-phase thrombin. Direct thrombin inhibitors also produce a more predictable anticoagulant response than heparin because they do not bind to plasma proteins and are not neutralized by platelet factor 4. Bivalirudin appears to have a wider therapeutic window than hirudin. Because this may permit administration of higher doses of bivalirudin, this agent may also have an efficacy advantage over hirudin. Differences observed between hirudin and bivalirudin demonstrate that not all direct thrombin inhibitors have the same risk-benefit profile.

Angioplasty, Balloon, Coronary↗
PubMed1999

Prevention of activation of blood coagulation during acute coronary ischemic syndromes: beyond aspirin and heparin.

Many of the acute coronary ischemic syndromes are triggered by spontaneous or mechanical disruption of atherosclerotic plaques with resultant activation of platelets and coagulation. Given the central role of platelets and thrombin in arterial thrombosis, current strategies for its prevention and treatment focus on both inhibition of platelet aggregation and control of thrombin generation and activity. Although aspirin and unfractionated heparin are the cornerstones of current treatment strategies, both have limitations. This review will describe these limitations and discuss new antithrombotic agents developed for use in acute coronary ischemic syndromes and as adjuncts for percutaneous coronary revascularization procedures.

Anticoagulants↗
PubMed1999

Optimal management of pregnant women with acute venous thromboembolism.

Venous thromboembolism (VTE) is an important cause of obstetric morbidity and mortality. Its management during pregnancy is problematic because anticoagulants, the cornerstone of initial therapy for VTE, may have significant foetal as well as maternal side effects. Unfractionated heparin has been the anticoagulant of choice in pregnancy; however, there is growing clinical experience with low-molecular-weight heparin (LMWH) in this patient population. A recently published systematic review of the literature suggests that the use of LMWH during pregnancy is not associated with adverse foetal/infant outcomes. Moreover, its long-term use appears to be safe for the mother, as symptomatic osteoporosis, bleeding and heparin- induced thrombocytopenia occurred only infrequently. There are limited data regarding the efficacy of anticoagulant therapy in the treatment of VTE during pregnancy, and treatment recommendations have largely been extrapolated from data in non-pregnant patients and case series of pregnant patients. This paper will briefly review the challenges and areas of controversy associated with the use of anticoagulants in the treatment of pregnancy-associated VTE.

Female↗
PubMed1999

Anticoagulation in pregnancy.

The use of anticoagulants during pregnancy for prevention and treatment of venous thromboembolism and prevention of systemic embolism in patients with valvular heart disease presents several problems. This article discusses the complications associated with warfarin, unfractionated heparin, and low-molecular-weight heparin as well as the benefits of each. While a literature review turned up only limited data, the authors extrapolated from existing data recommendations for treatment during pregnancy, finding that oral warfarin should be replaced by heparin during pregnancy, especially from the 6th to the 12th week and near term. In addition, treatment recommendations are provided for different stages of pregnancy, delivery, and postpartum.

Anticoagulants↗
PubMed1998

Direct thrombin inhibitors for treatment of arterial thrombosis: potential differences between bivalirudin and hirudin.

Given the central role of thrombin in arterial thrombogenesis, most treatment strategies for acute coronary syndromes are aimed at inhibiting its generation or blocking its activity. Although heparin has been widely used, it has limitations in the setting of arterial thrombosis. These limitations reflect the inability of heparin to inactivate thrombin bound to fibrin, a major stimulus for thrombus growth. In addition, the anticoagulant response to heparin varies from patient to patient, and heparin is neutralized by platelet Factor IV, large quantities of which are released from platelets activated at sites of plaque rupture. Consequently, heparin requires careful laboratory monitoring to ensure an adequate anticoagulant effect. Direct thrombin inhibitors, such as hirudin and bivalirudin, overcome the limitations of heparin. These agents inhibit fibrin-bound thrombin, as well as fluid-phase thrombin, and produce a predictable anticoagulant response. Bivalirudin has both safety and potential efficacy advantages over hirudin. Bivalirudin appears to have a wider therapeutic window than hirudin, possibly because bivalirudin only transiently inhibits the active site of thrombin. The better safety profile of bivalirudin permits administration of higher doses, which may give it an efficacy advantage. Hirudin prevents thrombin from activating protein C, thereby suppressing this natural anticoagulant pathway. In contrast, bivalirudin may promote protein C activation by transiently inhibiting thrombin until it can be bound by thrombomodulin. Differences between bivalirudin and hirudin, as well as other direct thrombin inhibitors, highlight the pitfalls of considering all direct thrombin inhibitors to have equivalent risk-benefit profiles.

Acute Disease↗
PubMed1998

The new heparins.

Explore the source record for details and available documents.

Clinical Trials as Topic↗
PubMed1997

Anticoagulants in pregnancy: fetal effects.

Anticoagulants are used during pregnancy to prevent venous thrombo-embolism in highrisk patients, to prevent systemic embolism in patients with prosthetic heart valves or native valvular heart disease, and to treat patients with acute venous thrombo-embolism. Neither unfractionated nor low-molecular-weight heparin cross the placenta and both appear to be safe for the fetus. Oral anticoagulants do cross the placenta and they have been associated with the development of warfarin embryopathy, central nervous system anomalies, and fetal haemorrhage. The true incidence of these events is not known. Both heparin and oral anticoagulants can be safely administered to nursing mothers.

Abnormalities, Drug-Induced↗
PubMed1997

Thrombosis in pregnancy.

Thrombosis during pregnancy poses special problems. This review focuses on risk factors for the development of venous thromboembolism during pregnancy, diagnosis of deep vein thrombosis and pulmonary embolism during pregnancy, therapeutic recommendations for the treatment of acute thromboembolism during pregnancy, and thromboprophylaxis in the pregnant woman. Management of pregnant women with antiphospholipid antibodies is also reviewed.

Antibodies, Antiphospholipid↗
PubMed1990

Hepatoblastoma: detection of tumor vascularity with duplex Doppler US.

The evaluation of pediatric abdominal masses commonly includes computed tomography, ultrasound (US), and, more recently, magnetic resonance imaging. A previous study suggested that duplex US is of use in further tissue characterization of hepatic lesions in adults. The authors describe the Doppler signals arising from hepatoblastomas in three infants. Peak systolic Doppler frequency shifts in the neoplasms of these three patients were all equal to or greater than 4 kHz, well above the normal range for hepatic arteries. Each neoplasm also exhibited antegrade diastolic flow. The detection of high Doppler frequency shifts associated with neovascularity may prove useful in future evaluation of pediatric hepatic masses.

Carcinoma, Hepatocellular↗
PubMedDate not supplied

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.

Anticoagulants↗