In vivo study of the complement system during infusion of radiographic contrast media.

It has been claimed that activation of the complement system may play a role in reaction to radiographic contrast media (RCM) infusion. In order to clarify the effects of RCM on the complement system, three different parameters (CH50, C3a, and C1 inhibitor) were measured in 20 patients undergoing intravenous pyelography for diagnostic purposes. We found no significant changes in C3a levels, but CH50 and C1 inhibitor fell significantly at the different sampling times; however, the decreases lost significance when the data were corrected for hemodilution with the total protein content of each sample as a reference. We conclude that RCM infusion does not activate the complement system.