Complement and coagulation: causative considerations in contrast catastrophies.

Earlier studies suggest that adverse reactions to injected radiographic contrast media are idiosyncratic. In an attempt to gain a better understanding of pathophysiologic events underlying these reactions, rabbit models injected with lethal dose ranges of a cholangiographic contrast material were studied. These animals showed activation of both the complement and coagulation systems. Externally applied heat potentiated complement consumption and increased mortality. Depleting complement components C3-C9 by cobra venom factor did not prevent activation of coagulation or diminish mortality. However, depleting fibrinogen diminished complement activation and markedly diminished mortality. Heparin, administered at several hourly intervals after contrast challenge, also diminished mortality. These studies suggest that the adverse effects of contrast media in this model system are mediated chiefly by the coagulation system, and that complement, if it participates deleteriously, must involve components up to, but not including, C3. A logical role for the inhibitor of C1 esterase in adverse contrast reactions is considered.