Influence of radiographic contrast media (Iomeprol 350 versus Iopentol 350) on cutaneous microcirculation: single-center prospective randomized double-blind phase iv study in parallel-group design.

This single-center, prospective, randomized, double-blind phase IV study in parallel-group design was carried out to investigate whether either of two different x-ray contrast media (iomeprol 350 or iopentol 350) injected into the axillary artery has any influence on cutaneous microcirculation. The investigation was carried out on two groups of patients (n = 10 in each group) who had to undergo a diagnostic heart catheter angiography. The confirmatory response variable for the study was the mean capillary erythrocyte velocity (mm/sec). Blood flow through the ipsilateral nail-fold capillaries was recorded continuously for 3 minutes before and 6 minutes after the injection of the randomly assigned x-ray contrast medium, and was evaluated off-line. A contrast medium-induced, rheologically determined disturbance of the microcirculation was found, which was due to two different effects. First, the high intrinsic viscosity (iopentol = 12.3 mPa.sec) led to an immediate reduction in capillary blood flow. This did not occur in the case of iomeprol (intrinsic viscosity = 7.5 mPa.sec). Second, the contrast medium molecules cause a morphological change in the erythrocyte membrane; echinocytes are formed and are further desiccated depending on osmolality of the contrast medium. The time course of the conversion of erythrocytes into echinocytes leads to a maximum reduction in capillary erythrocyte velocity of 30 seconds after the bolus of contrast medium. For the more viscous contrast medium of higher osmolarity (iopentol), this led to a significant overall reduction of up to 48.6% in capillary blood flow (p < 0.0001) that lasted for up to 150 seconds, while iomeprol did not significantly affect capillary blood flow (p = 0.2759).