A nurse is caring for a patient who is experiencing anaphylaxis after receiving a penicillin injection. Which nursing action should be the FIRST priority?

Epinephrine is the first-line treatment for anaphylaxis and must be administered immediately to counteract severe allergic reactions and prevent cardiovascular collapse. Other interventions like airway management, IV fluids, and antihistamines are secondary supportive measures.

Understanding the Priority: Anaphylaxis Management
When a patient develops anaphylaxis following a penicillin injection, the clinical priority is to halt the progression of a life-threatening, systemic hypersensitivity reaction. Anaphylaxis involves massive release of mediators from mast cells and basophils, leading to profound vasodilation, increased capillary permeability, and bronchoconstriction. This can rapidly progress to airway compromise and cardiovascular collapse. The foundational principle of emergency response, as highlighted in the 2025 Korean Guidelines for Cardiopulmonary Resuscitation for anaphylaxis, is the immediate administration of intramuscular epinephrine .

Why Epinephrine is the First Priority
Epinephrine is the first-line drug because it directly counteracts the pathophysiological mechanisms of anaphylaxis. Its alpha-adrenergic effects cause vasoconstriction, which reverses peripheral vasodilation and reduces edema, thereby supporting blood pressure. Its beta-adrenergic effects cause bronchodilation, relieving respiratory distress, and suppress further release of inflammatory mediators from mast cells. Delaying epinephrine administration is associated with increased risk of fatality and biphasic reactions. The recommended dose for adults is 0.3 mg intramuscularly into the anterolateral thigh, which provides rapid absorption and peak plasma concentrations .

Analyzing the Other Options in Sequence
While all the listed actions are part of the comprehensive management of anaphylaxis, they are secondary to epinephrine. The clinical sequence should follow a "circulation, airway, breathing" approach in this context, where establishing effective circulation with epinephrine is the immediate life-saving measure.

- Option 1: Administer diphenhydramine 25 mg IV push. Diphenhydramine is an H1-antihistamine. It can relieve cutaneous symptoms like urticaria and pruritus but has a slow onset of action and does not reverse cardiovascular collapse or bronchospasm. It is a second-line, adjunctive treatment, never the first priority in an acute crisis.
- Option 3: Establish a patent airway and administer high-flow oxygen. Airway management and oxygenation are critical. However, upper airway edema (e.g., laryngeal edema) causing obstruction is often rapidly progressive. The vasoconstrictive effect of epinephrine can reduce this edema, potentially averting the need for immediate advanced airway intervention. While preparing for airway management, the first and most critical action is to inject epinephrine, which can stabilize the airway and breathing concurrently.
- Option 4: Start a large-bore IV line and infuse normal saline rapidly. Aggressive fluid resuscitation is essential to counteract the distributive shock from profound vasodilation and increased vascular permeability. However, fluid alone will not reverse the underlying bronchoconstriction or mediator release. Epinephrine must be given first to provide the pharmacologic support needed for fluid resuscitation to be effective in restoring hemodynamic stability.

The systematic approach to anaphylaxis is clear: early recognition and immediate intramuscular epinephrine administration is the cornerstone of treatment and the single most critical intervention to prevent progression to fatal outcomes . This principle is also fundamental in high-risk environments such as schools, where protocols for managing anaphylaxis from food allergies similarly prioritize immediate epinephrine access and administration .