Hemorheological effects of a nonionic contrast medium: An ex vivo study

Blood and plasma viscosity were measured in 10 patients, before and after administration of the nonionic contrast medium Iopromide for coronary angiography. In all patients the hematocrit dropped markedly; the mean (± SD) value decreased from 0.425 ± 0.036 to 0.386 ± 0.037 (p < 0.001). The mean blood viscosity also decreased significantly, in a dose-dependent way; this effect could be entirely explained by the change in hematocrit. Plasma viscosity remained constant despite the high viscosity of the contrast medium. The drop in hematocrit was caused by the volume of the contrast medium plus a shift of water from extravascular spaces to plasma, due to the high osmolarity of the contrast agent. The contrast medium studied is unlikely to cause clinically relevant late effects on blood rheology other than hemodilution.