Which of the following is indicative of a severe reaction to contrast media?

Severe reactions to contrast media are characterized by a range of symptoms that indicate a significant physiological response, often involving life-threatening conditions. Chills and severe vomiting represent a serious reaction, as they can be associated with anaphylaxis or a severe hypersensitivity reaction to the contrast agent. These symptoms signify the body's extreme response to the substance, often accompanied by systemic effects like difficulty breathing, hives, or swelling.

In contrast, isolated chest pain is more ambiguous and can be related to a variety of non-life-threatening causes. Mild urticaria, which refers to slight hives or rash, typically indicates a mild allergic reaction and is not characteristic of severe reactions. Protracted nausea can occur in various contexts and does not specifically denote a severe response to contrast media. Hence, chills and severe vomiting stand out as a clear marker of a more acutely dangerous reaction requiring immediate medical attention.