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

Administer epinephrine 0.3-0.5 mg IM into the anterolateral thigh as soon as anaphylaxis is recognized. This is the single most critical intervention and should not be delayed for airway management or IV access. The dose can be repeated every 5-15 minutes if symptoms persist.

• Positioning: Place the patient supine with legs elevated to promote venous return. Avoid the Trendelenburg position. If respiratory distress is present, the patient may sit upright, but monitor closely for hypotension.
• Oxygenation: Administer high-flow oxygen (100% non-rebreather mask) to target SpO2 > 92%.
• Fluid Resuscitation: Establish large-bore IV access and administer isotonic crystalloid (e.g., 0.9% normal saline) at 1-2 L for adults, or 20 mL/kg for children, for persistent hypotension.
• Adjunctive Therapies: Consider second-line agents such as H1/H2 antihistamines (e.g., diphenhydramine, famotidine) and corticosteroids (e.g., methylprednisolone) for symptom control, but they do not replace epinephrine.

Continuously monitor airway, breathing, circulation, and vital signs. Observe for biphasic reactions, which can occur hours after the initial episode. All patients receiving emergency epinephrine require a period of observation, typically in an emergency department, and should be prescribed an epinephrine auto-injector upon discharge with education on trigger avoidance.