Final answer:
The top priority for a nurse caring for a child with an anaphylactic reaction is to administer epinephrine to counteract the life-threatening symptoms of anaphylaxis.
Step-by-step explanation:
When caring for a school-age child experiencing an anaphylactic reaction in the ED, the priority action by the nurse is to administer epinephrine. Anaphylaxis is a rapid, life-threatening allergic reaction caused by a massive release of histamines leading to symptoms like respiratory distress, plummeting blood pressure, and potential suffocation. Epinephrine is the drug of choice for counteracting these effects as it constricts blood vessels to increase blood pressure, relaxes smooth muscles in the lungs to help with breathing, modulates heart rate, and reduces airway swelling. While assessing respiratory status and providing emotional support are important, they follow in priority after the administration of epinephrine, which addresses the critical physiological threats of anaphylaxis immediately and can be lifesaving.