During a transfusion, a patient develops anaphylaxis. What is the immediate action?

• A. Epinephrine
• B. RhoGAM
• C. Diphenhydramine
• D. Fresh frozen plasma

Answer: (A)

Anaphylaxis is a rapid, life-threatening hypersensitivity reaction that causes widespread vasodilation, increased vascular permeability leading to edema, and bronchospasm. The immediate intervention is epinephrine, because it acts quickly on multiple receptors to reverse these processes: alpha-1 effects constricting vascular beds to raise blood pressure and reduce edema, beta-1 effects increasing heart rate and contractility to support circulation, and beta-2 effects relaxing bronchial smooth muscle to relieve bronchospasm. Administer epinephrine intramuscularly without delay (adult dose typically 0.3–0.5 mg of 1:1000 solution; repeat every 5–15 minutes as needed). Stop the transfusion right away, secure the airway, give high-flow oxygen, and establish IV access with fluids as needed. While diphenhydramine or steroids can be given as adjuncts, they do not replace epinephrine as the immediate life-saving treatment. RhoGAM and fresh frozen plasma are not used for acute anaphylaxis.