The effect of low-osmolar ionic and nonionic contrast media on human blood viscosity, erythrocyte morphology, and aggregation behavior.

The effects of three low-osmolar radiographic contrast media (CM)--two nonionic (iohexol, iopamidol) and one ionic (ioxaglate)--on red blood cell (RBC) morphology and aggregation behavior, as well as on blood and plasma viscosity, have been studied. Blood taken from normal, healthy individuals and from patients with uremia was investigated. The authors controlled for the effects of dilution, ionic and nonionic hyperosomolality, and specific chemotoxicity. With ioxaglate, the normal biconcave RBC morphology was fairly well maintained. Iohexol produced a mixture of more-or-less normal cells and echinocytes, while iopamidol yielded only echinocytes. Irregular RBC aggregates have been frequently associated with the presence of echinocyte morphology. In the case of ioxaglate, the capacity of normal blood for rouleaux formation was preserved. This appeared to be compatible with an only moderate decrease in low shear viscosity values. In comparison to the normal control group, RBCs from patients with uremia were clearly more sensitive for hyperosmolar stress. It can be concluded that, in contrast to the nonionic CM, the ionic dimeric compound ioxaglate seems to protect human RBCs against hyperosmolar stress by a mechanism unknown at the present.