Several guidelines have been developed for management of the patient with a supratherapeutic international normalized ratio (INR). Consequently, over-anticoagulation is common. Because of its narrow therapeutic index, maintaining anticoagulation in the therapeutic range can be difficult. This inhibition prevents the gamma carboxylation of the vitamin K-dependent clotting factors, ultimately leading to their depletion. As a vitamin K antagonist, warfarin inhibits the cyclic conversion of vitamin K 2,3 epoxide to vitamin K quinone as well as the conversion of vitamin K quinone to vitamin K quinol, the active moiety. In addition, warfarin is used to treat formed thrombus including those in the deep veins.
Warfarin is widely used to prevent thrombus formation resulting from mechanical heart valves as well as in conditions including atrial fibrillation and dilated cardiomyopathy. Bleeding events occurred in a minority of patients. In this case series of acute warfarin overdose, nearly all patients developed a coagulopathy, and nearly three-quarters of patients received vitamin K. Three bleeding events occurred one classified as major, and two as minor. The maximal total amount of vitamin K administered to a single patient during the index hospitalization was 110 mg. Seventeen subjects received vitamin K, with a median (IQR) dose of 15 (10–50) mg. The median (interquartile range (IQR)) age was 43 (32–48.5) years. Twenty-three patients were admitted during the time period males accounted for 15/23 (62.5 %) subjects. Clinical characteristics were abstracted, and bleeding categories (major, minor, trivial) were defined a priori. A retrospective chart review of patients admitted with an acute warfarin overdose at two tertiary care medical centers in the USA was conducted. A secondary goal is to describe the amount of vitamin K administered to patients presenting with warfarin overdoses. The primary objective of this manuscript is to characterize the coagulopathy and describe the bleeding events that occur after a warfarin overdose.
There is a paucity of literature describing the latter. While guidelines exist for management of a supratherapeutic international normalized ratio following therapeutic warfarin use, these guidelines are not designed for management of the acute warfarin overdose. Warfarin, a vitamin K antagonist, is widely used for the prophylaxis and treatment of thromboembolic disease.
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