Since calcium ions are needed in all phases of clotting, removal of these ions will prevent coagulation. Citrate was formerly used to complex the calcium as insoluble calcium citrate, thus preventing clotting during storage.
	Note that the three forms of hemophilia are caused by deficiency of factors in the intrinsic pathway. Individuals with these disorders will suffer internal hemorrhaging from bruises etc. but their blood will clot, although more slowly, from external wounds which involve tissue damage. Factors synthesized by genetically engineered bacteria are used to treat these conditions.