Anticoagulants and Bleeding Risk

Anticoagulants reduce the formation or activity of clotting factors so that a new clot is less likely to form and an existing clot is less likely to extend. They do not dissolve an established thrombus. The same reduction in clot formation that protects against stroke or venous thromboembolism also weakens the patient’s ability to stop bleeding after tissue injury. Bleeding risk is not determined by the drug name alone. Renal clearance, hepatic function, platelet count, blood pressure, age, recent procedures, the indication for anticoagulation, and interacting medications all change the balance between thrombosis and haemorrhage. Aspirin, other antiplatelet agents and NSAIDs are particularly important because they impair platelet-related haemostasis in addition to the anticoagulant effect. Anticoagulants are high-alert medications in Canada. A dose error, wrong concentration or unrecognized decline in renal function can produce serious harm. Independent double checks, standardized concentrations and careful verification of the indication are safety measures, not paperwork. Warfarin illustrates why laboratory results must be interpreted in context. It inhibits vitamin K epoxide reductase, reducing the liver’s production of factors II, VII, IX and X, as...