[Effects of uro-angiographic contrast media on blood coagulation--a scanning electron microscopic study on time dependent changes of blood clot and a clinical study].

Anticoagulant activity of ionic and nonionic contrast media (CM) was investigated in vitro and in vivo. Based on the time course of FPA and TAT generations and gross examinations of the blood clots on the catheters placed in CM-blood mixtures [an 2 to 8 ratio (20% v/v)]. It was demonstrated that blood coagulation was activated during the period of 20 to 30 minutes when nonionic CM (iopamidol, iohexol) was employed, but no activation of blood coagulation was noted with ionic CM (diatrizoate, ioxaglate). Scanning electron microscopic examinations of the clots on the catheters revealed that fine fibrin meshwork fibers, in which many red blood cells were trapped in bound, were observed with nonionic CM. In contrast, no fibrin mesh was formed with ionic CM after 30 minutes. In vivo, antithrombin III and fibrinogen significantly decreased in the patients who underwent infusion of nonionic CM. Our studies confirmed that nonionic CM show weaker anticoagulant activity than do ionic CM. And these findings account for previous reported thromboembolic complications with the use of nonionic CM. Extreme caution should be therefore exercised when nonionic CM are employed during prolonged angiographic and interventional procedures.