Effects of contrast media on blood rheology: Comparison in humans, pigs, and sheep

Purpose: To compare whole blood viscosity and erythrocyte aggregation in hu mans, pigs, and sheep, before and after adding water-soluble iodinated cont rast medium (CM). Methods: Two CMs were studied: iopromide (nonionic) and ioxaglate (ionic). The blood-CM viscosity was measured with a Couette viscometer. Erythrocyte aggregation was measured with an erythroaggregometer. Results: The blood-CM viscosity was increased up to +20% (relative to pure blood) with a CM concentration of 0%-10%, At CM concentrations from 10% to 50%, the viscosity decreased. The disaggregation shear stress was increased (relative to pure blood) at low CM concentration (0%-10%). When the CM con centration increased from 10% to 20%, the disaggregation shear stress was d ecreased, except with the pig blood-ioxaglate mixture. Conclusion: At low CM concentration the blood viscosity was increased in pi g, sheep, and humans and the disaggregation shear stress was increased in p ig and humans. The aggregation of sheep blood was too low to be detected by the erythroaggregometer. This rise can be explained by the formation of po orly deformable echinocytes. At higher CM concentration, the viscosity and the disaggregation shear stress decreased in relation to the blood dilution . We conclude that pig blood and sheep blood can both be used to study the effect of CM injection on blood viscosity. Nevertheless, the theologic beha vior of pig blood in terms of erythrocyte aggregation is closer to that of human blood than is sheep blood when mixed with CM. Pigs could thus be more suitable than sheep for in vivo studies of CM miscibility with blood durin g selective cannulation procedures.