Contrast agents and contact activation of coagulation

The effects of angiographic contrast agents on the coagulation mechanisms have been a matter of considerable controversy recently. These agents in general have inhibitory effects on fibrin polymerization but are also contact activators of factor xII. These phenomena and the differences between ionic and nonionic agents have been discussed in the context of the safety of angiographic procedures. However, these phenomena may also help explain the basic mechanisms of some adverse reactions to intravascular contrast agents