Reactions to radiographic contrast media.

Patients with a history of an anaphylactoid reaction to radiographic contrast media are at increased risk for a subsequent reaction, but reactions cannot be predicted. Because contrast studies are often essential for optimal management, it may be necessary to take the risk of reexposing the patient to the contrast media. Prednisone-diphenhydramine pretreatment significantly decreases the likelihood of another reaction. Treatment of an anaphylactoid reaction requires knowledge of basic and advanced cardiopulmonary resuscitation.