General toxicity of water-soluble iodinated contrast media. Pathogenic concepts.

Despite many studies, the mechanism of the general accidents induced by the intravascular injection of water-soluble iodinated contrast media remains unclear. Two theories are proposed; until now, they have not been related to each other. Lalli emphasizes the role of a cerebral impact related to stress, which induces a chain of accidents that are perhaps more aggressive when the molecules cross the blood-brain barrier. Lasser has proposed a theory based on the biochemical catastrophies secondary to the damage of the vascular endothelium and the activation of the Hageman's factor XII. A true anaphylaxis has not been proven: specific immunoglobulins are only exceptionally found, and an actual primary activation of the complement system pathway with mediator release is a controversial phenomenon in vivo. The anaphylactoid collapses result from a chemotoxic effect that might be decreased by several kinds of pharmaceutical premedications; none of them are constantly efficient. The new low osmolar molecules have a very low general toxicity, but their use does not guarantee the lack of anaphylactoid reactions.