Bleeding and vitamin K deficiency

Vitamin K is a cofactor for human glutamic acid carboxylase enzymes in multiple tissues and organs. The dominant vitamin K activity is gamma-carboxylation of selective glutamic acid residues on coagulation factors X, IX, VII, and II. Humans predominantly rely on green vegetable dietary sources of vitamin K rather than synthesis of vitamin K by intestinal bacteria. Vitamin K deficiency bleeding in newborns is uncommon, potentially devastating, and preventable with vitamin K prophylaxis. Other causes of vitamin K deficiency include prolonged anorexia, malabsorption, and rapid depletion without adequate intake during acute medical and surgical events. The significance and mechanisms of antibiotic-associated vitamin K deficiency remain controversial and incompletely investigated. Management options for vitamin K deficiency include oral and parenteral vitamin K and coagulation factor replacement. Ingestion of "superwarfarin" rodenticides produces a severe and prolonged coagulopathy with potential for major bleeding complications.