A client is experiencing an anaphylactic reaction. What is the priority intervention?

Anaphylaxis is a life-threatening systemic allergic reaction requiring immediate action. Signs: hives, urticaria, swelling (face, lips, tongue, throat), wheezing, stridor, hypotension, shock. Priority interventions: (1) Stop the offending agent — discontinue IV infusion, remove contact; (2) Assess and maintain the airway — anaphylaxis can cause rapid airway swelling; (3) Administer epinephrine IM (epinephrine auto-injector or 1:1000 solution, 0.3-0.5 mg adult dose, IM in vastus lateralis) — epinephrine is the first-line treatment, given immediately; (4) Call rapid response or code team; (5) Position supine with legs elevated unless respiratory distress requires sitting up; (6) Administer high-flow oxygen; (7) Establish IV access for fluids and additional medications; (8) Prepare for possible intubation. Secondary medications: antihistamines (diphenhydramine), corticosteroids (methylprednisolone), bronchodilators if wheezing. Epinephrine works within minutes; a second dose may be needed in 5-15 minutes.