RESUMO
One hundred and forty-six cases of cardiac valvular prostheses in the Department of Surgery, Siriraj hospital, were studied retrospectively for the effect of long-term oral anticoagulant therapy. Warfarin sodium was given to 119 patients after operation, 5 cases discontinued therapy and 27 cases received no anticoagulant at all due to loss of follow-up. One stage prothrombin time was used as laboratory control. The advocated therapeutic range for commercial rabbit brain thromboplastin was 1.35-2.2 P.T. ratio. The incidence of thromboembolism was 8.9 per 100 patients - year in the nontherapeutic group, and was 0.6 per 100 patients - year in the therapeutic group (p less than 0.05). Bleeding complications was 26.9 per cent. These were 34 minor-, 11 major-and 2 fatal bleeding episodes. One bleeding manifestation was found in the nontherapeutic group, the etiology was not recorded. The mean dose of warfarin sodium in the thromboembolic group was 2.5 mg/day, this gave a therapeutic ratio of less than 1.4. In the bleeding group that had P.T. ratio not exceeding 2.2, the mean dose was 3.37 mg/day; and 5.23 mg/day when P.T. ratio was higher than 2.2 (p less than 0.01). Therefore, it seems justifiable to conclude that the appropriate mean dose should be over 2.5 mg/day and less than 3.37 mg/day. However, regular blood test to determine the appropriate daily dose for each individual patient is obligatory, as patients might be more or less sensitive to the drug than the average and drug requirement varies from time to time even in the same individual owing to many factors.(ABSTRACT TRUNCATED AT 250 WORDS)