Final answer:
For a patient with hives due to a contrast agent, epinephrine should be readily available to quickly address the type I hypersensitivity reaction.
Step-by-step explanation:
When a patient develops hives following the injection of an iodinated contrast agent, this is indicative of a type I hypersensitivity reaction, which can range from mild to severe, potentially leading to anaphylaxis. In such cases, it is essential to have epinephrine readily available. Epinephrine works quickly to counteract the effects of the allergic reaction by constricting blood vessels, which increases blood pressure, and by relaxing the muscles in the airways, which improves breathing. After initial treatment with epinephrine, other medications such as antihistamines and corticosteroids may be administered to further manage the reaction and prevent late-phase reactions.