A technique for estimating the probability of clots in blood/contrast agent mixtures

Blood that contaminates the contrast agent syringe during angiography may clot and is thus a potential source of emboli. The older, high-osmolality agents prevent clotting. Newer, low-osmolality agents, while possessing other advantages, are less effective in this regard. The time over which such mixtures do not contain clot can be determined by allowing gross clotting to take place, modeling the process mathematically and determining the clot-free time from the model. Blood-contaminated Omnipaque-300® (Win- throp-Breon, New York, NY) (iohexol), Isovue-300® (E.R. Squibb and Sons, New Brunswick, NJ) (iopamidol), Hexabrix® (Mallinckrodt, St. Louis, MO) (ioxaglate sodium meglumine), Renografin-76® (E.R. Squibb and Sons, New Brunswick, NJ) (diatrizoate sodium meglumine), and saline were studied in glass and plastic syringes (80 samples of each agent). After deliberate blood contamination, Renografin and Hexabrix showed no clots during the 90-minute study period. There was, however, a 1.3% chance of clotting in Omnipaque (range 0.4%-4.0%) and a 1.9% chance of clotting in Isovue (range 0.6%-5.5%) at 5 minutes after contamination of these contrast agents in plastic syringes. The chance of clotting in glass containers was significantly greater. We conclude that Hexabrix is a substantially stronger anticoagulant than Omnipaque and Isovue. Furthermore, it appears that this method will allow determination of clotting risks for other combinations of contrast agent and container.