[Anticoagulant or antiplatelet drugs and anesthesia]

An increasing number of preoperative patients are receiving therapy with an oral anticoagulant (warfarin) or antiplatelet drugs to prevent thromboembolic complications. Because of its irreversible inhibition on hepatic synthesis of vitamin K-dependent coagulation factors, warfarin must be stopped 3 to 4 (ideally 4 to 5) days prior to the planned major operation. Normal PT-INR is mandatory prior for neuraxial block. Rapid reversal of warfarin in emergency settings with FFP rather than vitamin K is advocated. More reliable and prompt reversal is possible with PCCs and rFVIIa, but this approach is off-label use in Japan as well as in the US. Antiplatelet drugs have different mechanisms to suppress platelet aggregation. Ticlopidine and clopidogrel should be stopped 7 days prior to the major surgery because of their irreversible inhibition on ADP receptors of platelets. Although it is recommended to stop aspirin 7 days prior to the planned major surgery in some guidelines, low dose oral aspirin (75-300 mg day(-1)) alone is accepted in another guideline because it does not create a level of risk that will interfere with the performance of neuraxial blocks.