Do nonionic contrast media increase red cell aggregation and clot formation?

Red cell aggregate formation was studied both macroscopically and microscopically in blood mixed with a contrast medium, either ioxaglate or iohexol. Whole blood was layered on top of the contrast medium, and after being shaken, blood cells were separated from the medium by centrifugation. The kinetics of red cell aggregate formation were measured by a transparent rheoscope and a photoaggregometer at different shear rates. Coagulation studies were conducted on citrated platelet-rich plasma mixed with contrast media. Platelet shapes were observed with phase contrast optics, and coagulation times were measured. It was demonstrated that the increased red cell aggregation, which occurred during the initial contact between blood and the contrast medium, dispersed after being submitted to shear force and did not re-form in the remaining plasma. Since this phenomenon is associated with high concentrations of contrast media in nonflowing blood, the high shear rate in arteries and arterioles make it unimportant in the in vivo situation. Within highly concentrated contrast media solutions, blood clot formation was not inducible, and the risk of thrombus formation in fresh blood drawn into contrast medium-filled syringes appears minimal.