Complement activation by iodinated contrast media.

Activation of the complement system by iodinated contrast medium (ICM) infusion was studied in 25 children with congenital heart disease who received 76% Urographin during angiocardiographic studies. Total hemolytic activity (CH50), C1q, C3, C4 and C3 activator were determined before and 2, 5, 10, 15 and 20 minutes after Urographin infusion. Results showed that CH50 decreased in 16 patients (64%), C3 in 12 patients (48%), C3 activator in 12 patients (48%), C1q in 11 patients (44%) and C4 in 11 patients (44%). No side effect was encountered in all patients. It is therefore concluded that both the classic and alternative complement pathways could be activated by ICM and no causal relationship could be found between the presence of complement activation and the occurrence of adverse reactions to ICM infusion.