Blood clot formation in angiographic syringes containing nonionic contrast media.

Spontaneous thrombus formation may occur if blood is allowed to mix with a nonionic contrast medium in the injection syringe or angiographic catheter. This is probably due to the absence of significant inhibition of the normal blood coagulation mechanism by currently used nonionic contrast media. Careful angiographic techniques will prevent blood from mixing with the contrast medium before injection. The use of a three-way stopcock and connecting tube between catheter and syringe is suggested. Contrast material should be flushed from the catheter immediately after injection. Systemic anticoagulation is not justified as a means of preventing thrombus formation. The potential prophylactic use of heparin added to the contrast medium during angiography or premedication with aspirin, and the attendant risks of these techniques, are discussed.