Iodinated contrast media: effect of osmolarity and injection temperature on erythrocyte morphology in vitro

Background: Some side effects of intravenously injected iodinated contrast media are thought to be linked to the biological properties of the various agents and their effect on blood components. Purpose: To assess the effect of osmolarity and injection temperature of iodinated contrast media on erythrocyte (RBC) morphology in vitro. Material and Methods: Blood from 20 volunteers was incubated with three different contrast media (320 mg I/ml iso-osmolar iodixanol, 300 mg I/ml low-osmolar iopromide, 300 mg I/ml low-osmolar iopamidol) injected at 37°C, 43°C, and 48°C, and in two different volumes corresponding to the estimated concentration at the site of venous injection and after systemic distribution. After 10 min incubation, aliquots were removed for complete blood count analysis and blood smears. Two hematologists blindedly and independently reviewed all smears, and determined the grade of morphological RBC changes compared to a blank sample. Results: There was excellent (κ = 0.98) inter-reader correlation for grading RBC changes. At systemic concentration at 37°C, the grade of RBC changes was significantly (P<0.05) less in blood samples exposed to iso-osmolar iodixanol (mean 0.21) as compared to low-osmolar iopromide (mean 0.26) and low-osmolar iopamidol (mean 0.58). These differences became more significant at higher volumes, corresponding to concentrations at the site of injection and higher injection temperatures. Conclusion: In vitro, RBC morphology is less affected by iso-osmolar as compared to low-osmolar contrast media. These differences become more significant at higher injection temperatures that are proposed to improve flow dynamics for high-speed injection.