A nurse is assisting in the care of a client who is receiving a transfusion of packed red blood cells. The client develops itching and hives. Which of the following actions should the nurse take first?

Choice A rationale The development of itching and hives suggests an allergic (urticarial) transfusion reaction, mediated by IgE antibodies reacting to plasma proteins in the donor blood. The first priority is to immediately stop the infusion to prevent the introduction of more antigens and halt the subsequent mast cell degranulation and histamine release, thereby minimizing the severity of the systemic reaction. Choice B rationale Notifying the registered nurse (RN) is a crucial subsequent step for collaborative management, documentation, and to initiate necessary treatment protocols, such as administering antihistamines and potentially antipyretics, and securing the necessary lab work to identify the reaction type. However, stopping the antigen exposure must occur first. Choice C rationale Obtaining a complete set of vital signs, including blood pressure, heart rate, respiratory rate, and temperature, is essential for monitoring for signs of a more severe reaction, such as anaphylaxis or a febrile non-hemolytic reaction. This is necessary but follows the immediate cessation of the causative agent, the blood product. Choice D rationale Administering diphenhydramine, an H1-receptor antagonist, is the appropriate pharmacological intervention to block the effects of histamine released during the allergic response, thereby alleviating symptoms like itching and hives. This is a treatment, but the primary action is removing the antigenic source by stopping the transfusion.