Practical tips for warfarin dosing and monitoring.
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Patients on warfarin and their physicians must constantly balance the risks of bleeding and clotting. We offer practical tips for safe and effective warfarin therapy, based on the practices of the Anticoagulation Clinic of The Cleveland Clinic. (+info)
Oral anticoagulation in patients after cerebral ischemia of arterial origin and risk of intracranial hemorrhage.
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BACKGROUND AND PURPOSE: In the recently published Warfarin Aspirin Recurrent Stroke Study (WARSS), a low-intensity anticoagulation regimen was used because of safety concerns. Such concerns are corroborated by the results of the Stroke Prevention in Reversible Ischemia Trial (SPIRIT), which was stopped early because of a high incidence of intracranial hemorrhage with a target international normalized ratio (INR) of 3.0 to 4.5. In the ongoing European/Australasian Stroke Prevention in Reversible Ischaemia Trial (ESPRIT), an intermediate anticoagulation regimen (INR 2.0 to 3.0) is used. METHODS: We performed an interim analysis of the incidence of intracranial hemorrhage in ESPRIT. RESULTS: Thus far the overall rate of intracranial hemorrhage is 0.31% (95% CI, 0.18% to 0.52%) per year and 1.21% if all of these were in the anticoagulation group. CONCLUSIONS: We conclude that anticoagulation with achieved INR of 2.0 to 3.0 is reasonably safe in patients with cerebral ischemia of arterial origin. (+info)
Reliability of international normalised ratios from two point of care test systems: comparison with conventional methods.
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OBJECTIVE: To find out how accurately two point of care test systems--CoaguChek Mini and TAS PT-NC (RapidPointCoag)--display international normalised ratios (INRs). DESIGN: Comparison of the INRs from the two systems with a "true" INR on a conventional manual test from the same sample of blood. SETTING: 10 European Concerted Action on Anticoagulation centres. PARTICIPANTS: 600 patients on long term dosage of warfarin. MAIN OUTCOME MEASURES: Comparable results between the different methods. RESULTS: The mean displayed INR differed by 21.3% between the two point of care test monitoring systems. The INR on one system was 15.2% higher, on average, than the true INR, but on the other system the INR was 7.1% lower. The percentage difference between the mean displayed INR and the true INR at individual centres varied considerably with both systems. CONCLUSIONS: Improved international sensitivity index calibration of point of care test monitors by their manufacturers is needed, and better methods of quality control of individual instruments by their users are also needed. (+info)
Capillary whole blood testing by a new portable monitor. Comparison with standard determination of the international normalized ratio.
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We evaluated a new portable monitor (AvoSure PT PRO, Menarini Diagnostics, Firenze, Italy) developed to test the prothrombin time in capillary blood and plasma by comparing it with the standard laboratory determination. We studied 62 patients receiving acenocoumarol therapy. The international normalized ratio (INR) in capillary blood was analyzed by 2 methods: AvoSure PT PRO and Thrombotrack Nycomed Analyzer (Axis-Shield, Dundee, Scotland). Parallel studies were performed in plasma samples by a reference method using the Behring Coagulation Timer (Behring Diagnostics, Marburg, Germany). Plasma samples also were tested with the AvoSure PT PRO. Correlation was good for INR values for capillary blood and plasma samples by AvoSure PT PRO and our reference method (R2 = 0.8596) and for capillary blood samples tested by the AvoSure PT PRO and Thrombotrack Nycomed Analyzer (R2 = 0.8875). The correlation for INR in capillary blood and plasma samples by AvoSure PT PRO was 0.6939 (P < .0004). Capillary blood determinations are rapid and effective for monitoring oral anticoagulation therapy and have a high correlation to plasma determinations. AvoSure PT PRO is accurate for controlling INR in plasma and capillary blood samples, may be used in outpatient clinics, and has advantages over previous portable monitors. (+info)
The influence of cyclo-oxygenase specificity of non-steroidal anti-inflammatory drugs on bleeding complications in concomitant coumarine users.
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BACKGROUND: Concomitant use of coumarines and non-steroidal anti-inflammatory drugs (NSAIDs) may induce bleeding complications, due to the inhibition of both coagulant factors and platelet function. Unlike non-selective NSAIDs, cyclo-oxygenase-2 (COX-2)-selective NSAIDs interfere very little with platelet aggregation. AIM: To determine whether COX-2-selective NSAIDs are associated with less bleeding complications in coumarine users, compared with non-selective NSAIDs. DESIGN: Prospective, nested case-control study. METHODS: We studied concomitant coumarine and NSAID users over two years. Patients with bleeding (cases), and frequency-matched patients without bleeding (controls), were sent questionnaires regarding possible risk factors for bleeding. International normalized ratio (INR) values were recorded. Univariate and multivariate analyses were used to detect factors contributing to bleeding. RESULTS: There were 1491 reported bleeds. NSAIDs were involved in 14.8%; 3.9% involving COX-2-selective NSAIDs. In non-bleeders, 2601 prescriptions with a coumarine/NSAID combination were detected; 9.7% were COX-2-selective. Adjusted ORs (95% CI) for a bleeding complication were 3.07 (1.18-8.03) for non-selective NSAID use, 3.01 (1.42-6.37) for NSAID use > 1 month, and 1.89 (1.03-3.49) for INR > or = 4.0. DISCUSSION: In coumarine users, COX-2-selective NSAIDs are associated with less bleeding complications than non-selective NSAIDs are. Duration of NSAID use, as well as intensity of coumarine treatment, plays an important additional role. When the coumarine-NSAID combination is inevitable in an individual patient, a COX-2-selective NSAID may be preferred, with careful monitoring of the INR. (+info)
Comparison of low-intensity warfarin therapy with conventional-intensity warfarin therapy for long-term prevention of recurrent venous thromboembolism.
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BACKGROUND: Warfarin is very effective in preventing recurrent venous thromboembolism but is also associated with a substantial risk of bleeding. After three months of conventional warfarin therapy, a lower dose of anticoagulant medication may result in less bleeding and still prevent recurrent venous thromboembolism. METHODS: We conducted a randomized, double-blind study, in which 738 patients who had completed three or more months of warfarin therapy for unprovoked venous thromboembolism were randomly assigned to continue warfarin therapy with a target international normalized ratio (INR) of 2.0 to 3.0 (conventional intensity) or a target INR of 1.5 to 1.9 (low intensity). Patients were followed for an average of 2.4 years. RESULTS: Of 369 patients assigned to low-intensity therapy, 16 had recurrent venous thromboembolism (1.9 per 100 person-years), as compared with 6 of 369 assigned to conventional-intensity therapy (0.7 per 100 person-years; hazard ratio, 2.8; 95 percent confidence interval, 1.1 to 7.0). A major bleeding episode occurred in nine patients assigned to low-intensity therapy (1.1 events per 100 person-years) and eight patients assigned to conventional-intensity therapy (0.9 event per 100 person-years; hazard ratio, 1.2; 95 percent confidence interval, 0.4 to 3.0). There was no significant difference in the frequency of overall bleeding between the two groups (hazard ratio, 1.3; 95 percent confidence interval, 0.8 to 2.1). CONCLUSIONS: Conventional-intensity warfarin therapy is more effective than low-intensity warfarin therapy for the long-term prevention of recurrent venous thromboembolism. The low-intensity warfarin regimen does not reduce the risk of clinically important bleeding. (+info)
Comparing the quality of oral anticoagulant management by anticoagulation clinics and by family physicians: a randomized controlled trial.
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BACKGROUND: There is growing evidence that better outcomes are achieved when anticoagulation is managed by anticoagulation clinics rather than by family physicians. We carried out a randomized controlled trial to evaluate these 2 models of anticoagulant care. METHODS: We randomly allocated patients who were expected to require warfarin sodium for 3 months either to anticoagulation clinics located in 3 Canadian tertiary hospitals or to their family physician practices. We evaluated the quality of oral anticoagulant management by comparing the proportion of time that the international normalized ratio (INR) of patients receiving warfarin sodium was within the target therapeutic range +/- 0.2 INR units (expanded therapeutic range) while they were managed in anticoagulation clinics as opposed to family physicians' care over 3 months. We measured the rates of thromboembolic and major hemorrhagic events and patient satisfaction in the 2 groups. RESULTS: Of the 221 patients enrolled, 112 were randomly assigned to anticoagulation clinics and 109 to family physicians. The INR values of patients who were managed by anticoagulation clinics were within the expanded therapeutic range 82% of the time versus 76% of the time for those managed by family physicians (p = 0.034). High-risk INR values (defined as being < 1.5 or > 5.0) were more commonly observed in patients managed by family physicians (40%) than in patients managed by anticoagulation clinics (30%, p = 0.005). More INR measurements were performed by family physicians than by anticoagulation clinics (13 v. 11, p = 0.001). Major bleeding events (2 [2%] v. 1 [1%]), thromboembolic events (1 [1%] v. 2 [2%]) and deaths (5 [4%] v. 6 [6%]) occurred at a similar frequency in the anticoagulation clinic and family physician groups respectively. Of the 170 (77%) patients who completed the patient satisfaction questionnaire, more were satisfied when their anticoagulant management was managed through anticoagulation clinics than by their family physicians (p = 0.001). INTERPRETATION: Anticoagulation clinics provided better oral anticoagulant management than family physicians, but the differences were relatively modest. (+info)
Protocol for Birmingham Atrial Fibrillation Treatment of the Aged study (BAFTA): a randomised controlled trial of warfarin versus aspirin for stroke prevention in the management of atrial fibrillation in an elderly primary care population [ISRCTN89345269].
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BACKGROUND: Atrial fibrillation (AF) is an important independent risk factor for stroke. Randomised controlled trials have shown that this risk can be reduced substantially by treatment with warfarin or more modestly by treatment with aspirin. Existing trial data for the effectiveness of warfarin are drawn largely from studies in selected secondary care populations that under-represent the elderly. The Birmingham Atrial Fibrillation Treatment of the Aged (BAFTA) study will provide evidence of the risks and benefits of warfarin versus aspirin for the prevention of stroke for older people with AF in a primary care setting. STUDY DESIGN: A randomised controlled trial where older patients with AF are randomised to receive adjusted dose warfarin or aspirin. Patients will be followed up at three months post-randomisation, then at six monthly intervals there after for an average of three years by their general practitioner. Patients will also receive an annual health questionnaire.1240 patients will be recruited from over 200 practices in England. Patients must be aged 75 years or over and have AF. Patients will be excluded if they have a history of any of the following conditions: rheumatic heart disease; major non-traumatic haemorrhage; intra-cranial haemorrhage; oesophageal varices; active endoscopically proven peptic ulcer disease; allergic hypersensitivity to warfarin or aspirin; or terminal illness. Patients will also be excluded if the GP considers that there are clinical reasons to treat a patient with warfarin in preference to aspirin (or vice versa). The primary end-point is fatal or non-fatal disabling stroke (ischaemic or haemorrhagic) or significant arterial embolism. Secondary outcomes include major extra-cranial haemorrhage, death (all cause, vascular), hospital admissions (all cause, vascular), cognition, quality of life, disability and compliance with study medication. (+info)