We carried out a placebo-controlled, double-blind, randomized study of the hemostatic effect of tranexamic acid mouthwash after oral surgery in 39 patients receiving anticoagulant agents because of the presence of cardiac valvular stenosis, a prosthetic cardiac valve, or a vascular prosthesis. Surgery was performed with no change in the level of anticoagulant therapy, and treatment with the anticoagulant agent was continued after surgery. Before it was sutured, the operative field was irrigated in 19 patients with 10 ml of a 4.8 percent aqueous solution of tranexamic acid (an inhibitor of fibrinolysis) and in 20 patients with a placebo solution. For seven days thereafter, patients were instructed to rinse their mouths with 10 ml of the assigned solution for two minutes four times a day. There were no significant differences between the two treatment groups in base-line variables, including the level of anticoagulation at the time of surgery. Eight patients in the placebo group had a total of 10 postoperative bleeding episodes, whereas only 1 patient in the tranexamic acid group had a bleeding episode (P = 0.01). There were no systemic side effects. We conclude that local antifibrinolytic therapy is effective in preventing bleeding after oral surgery in patients who are being treated with anticoagulants.

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A modification of the fibrin plate method is presented. Plasminogen-free human fibrinogen and plasminogen purified by affinity chromatography have been used. Fibrin plates without and with a constant amount of plasminogen and with agarose as stabilizing medium were used for the estimation of plasmin and plasminogen activator activity. Activator activity could be demonstrated in sterile bile and saliva. When plasmin activity was present, estimations of plasminogen activator were approximate. The method is sensitive, small volumes of reagents and samples are needed. The error of the method is comparatively low and the reproducibility is good.