A nurse is caring for a patient experiencing anaphylaxis. Which intervention should the nurse prioritize first?

Epinephrine is the first-line treatment for anaphylaxis, administered immediately to counteract severe allergic reactions and prevent cardiovascular collapse. Other interventions like oxygen and IV access are supportive but secondary.

Clinical Priority in Anaphylaxis

The correct answer is Administer epinephrine 0.3-0.5 mg intramuscularly. In the management of anaphylaxis, prompt administration of intramuscular epinephrine into the anterolateral thigh is the single most critical intervention and must be prioritized above all other measures, including airway management and fluid resuscitation.

Pathophysiological Rationale
Anaphylaxis is a severe, life-threatening systemic hypersensitivity reaction driven by massive mediator release from mast cells and basophils. This results in a rapid cascade of physiological derangements: profound vasodilation leading to distributive shock, increased vascular permeability causing airway edema, and bronchoconstriction leading to respiratory failure. Epinephrine acts as the physiological antagonist to this cascade. Its alpha-1 adrenergic effects reverse peripheral vasodilation and reduce mucosal edema, restoring hemodynamic stability and airway patency. Its beta-2 adrenergic effects cause bronchodilation and further stabilize mast cells by inhibiting further release of inflammatory mediators . No other single agent—not oxygen, intravenous fluids, or positioning—can simultaneously address the multiple life-threatening mechanisms of anaphylaxis. Delay in epinephrine administration is consistently associated with fatal outcomes .

Analysis of Other Options
- Option 1 (Administer high-flow oxygen): While supplemental oxygen is a critical supportive measure for hypoxemia, it does not reverse the underlying vasodilation, capillary leak, or bronchoconstriction. Establishing an airway and providing oxygen is a secondary step that follows the immediate administration of epinephrine.
- Option 3 (Establish large-bore IV access for fluid resuscitation): Aggressive fluid resuscitation is essential for managing the distributive shock component of anaphylaxis, as intravascular volume is rapidly depleted. However, obtaining IV access takes time, and crystalloid infusion alone cannot overcome the profound vasodilation without the vasopressor effect of epinephrine. This intervention is performed concurrently but is secondary in priority to the first dose of epinephrine.
- Option 4 (Position the patient in Trendelenburg position): The Trendelenburg position is no longer recommended for shock management. For anaphylaxis, the recommended position is supine with legs elevated to promote venous return, unless this causes respiratory distress. More importantly, positioning is a supportive measure that does not treat the underlying pathophysiology and must never delay epinephrine administration.

Integration of Evidence and Clinical Practice
The 2025 Korean Guidelines for Cardiopulmonary Resuscitation explicitly identify anaphylaxis as a priority emergency and emphasize that the core principle of first aid is the immediate administration of epinephrine . This guideline reflects the global consensus that epinephrine is the first-line drug with no absolute contraindications in the setting of suspected anaphylaxis. The systematic review on food allergy management in schools reinforces this by highlighting that environments caring for children at risk for anaphylaxis must have protocols centered on rapid recognition and immediate epinephrine injection as the cornerstone of emergency response . Furthermore, research on pediatric emergency nursing education identifies the management of severe allergic reactions as a high-priority competency, underscoring the need for nurses to have automated, rapid decision-making skills where epinephrine administration is the reflexive first action . While concerns about medication allergies, such as penicillin, can complicate clinical decision-making in other contexts, the acute management of anaphylaxis itself is unambiguous: the risk of death from untreated anaphylaxis far outweighs any hypothetical risk from a single dose of intramuscular epinephrine . The nurse's priority is to administer the epinephrine immediately upon recognizing the signs of a severe, rapidly progressing allergic reaction.