A Study of Oral Anticoagulant Therapy at an Early Stage after Cardiac Operation to Determine the Starting Dose of Warfarin Therapy / 日本心臓血管外科学会雑誌

Single administration of warfarin at 0.1mg/kg was carried out at an early stage after cardiac operation, and changes in the blood vitamin K levels, blood coagulation factors and the blood warfarin levels within 24 hours of administration were evaluated to determine an ideal mode of initiating the administration and the initial dose in warfarin therapy at an early postoperative stage. The study group consisted of 30 postoperative cardiac cases, and 20 healthy individuals as controls. The results showed that anticoagulant effects cause close to the therapeutic range within 24 hours of administration of oral warfarin therapy in prothrombin time of the postoperative cases. As regards the blood vitamin K levels, both vitamin K₁ and K₂ levels were more depressed in the subjects than in the control group. Differences in the vitamin K level seemed to play a key role in the difference in anticoagulability between the two groups. It was thus implied that the risk of an abrupt decline in coagulability and a decrease in the level of vitamin K parallels the starting level of warfarin instituted in the wake of a cardiac operation. To conclude, safe and effective warfarin therapy should be started at a 0.1mg/kg dosage level at an early stage after the cardiac operation.