Definition: Severe, systemic hypersensitivity reaction. Usually rapid in
onset and characterized by compromise in airway, breathing, and/or
circulation. May involve multiple organ systems, including the following:
a. Cutaneous/mucosal (80% to 90%): Flushing, urticaria, pruritis,
angioedema
b. Respiratory (70%): Laryngeal edema, bronchospasm, dyspnea,
wheezing, stridor, hypoxemia
c. Gastrointestinal (45%): Vomiting, diarrhea, nausea, crampy
abdominal pain
d. Circulatory (45%): Tachycardia, hypotension, syncope

2. Management:
   a. Stop exposure to precipitating antigen.
   b. While performing A-B-Cs, immediately give intramuscular (IM)
   epinephrine into midanterolateral thigh.
   (1) For child, administer 0.01 mg/kg of 1 mg/mL solution up to a max
   dose of 0.3 mg/dose. For adult-sized patients, first administer 0.2
   to 0.5 mg of 1 mg/mL solution, increasing as necessary up to max
   single dose of 0.5 mg.
   (2) Autoinjector dosing: 7.5 to <15 kg use 0.1 mg, 15 to <30 kg use
   0.15 mg, ≥30 kg use 0.3 mg.
   (3) Repeat dosing every 5 to 15 minutes as needed.
   c. Provide oxygen and ventilatory assistance. Consider early
   endotracheal intubation.
   d. Obtain IV access. For management of shock, resuscitate with 20 mL/
   kg isotonic crystalloid fluid boluses and vasoactive agents as
   needed.
   e. Place patient in Trendelenburg position (head 30 degrees below feet).
   f. Consider adjuvant pharmacologic agents:
   (1) Histamine receptor antagonist: Diphenhydramine (H1-
   antagonism) and famotidine (H2-antagonism)
   (2) Corticosteroid: Methylprednisolone or dexamethasone
   (3) Inhaled b2 agonist: Albuterol