Question: A 20 year-old patient presents with hypotension, wheezing, and urticaria 30 minutes after a bee sting. What is the appropriate treatment?
Answer:
This patient’s presentation is that of systemic anaphylaxis. Anaphylaxis is an immediate hypersensitivity reaction caused by mast cell/basophil release of multiple potent mediators, including histamine, prostaglandins, and leukotrienes, into tissues and the circulation. Prompt treatment is critical, and therapy should be directed toward maintaining cardiovascular and pulmonary function. Initial treatment should be administration of epinephrine either by subcutaneous or intramuscular (IM) routes (0.3-0.5cc of a 1:1000 dilution). In the face of cardiovascular collapse, intravenous (IV) epinephrine may be indicated. Other immediate steps include applying a tourniquet proximal to the site of allergen inoculation (for example, a bee sting or allergen injection in the forearm). If the anaphylaxis is due to oral intake of an allergen (such as food ingestion), a nasogastric (NG) tube may be inserted and residual gastric contents removed to prevent further antigen absorption. The patient’s legs should be elevated, oxygen and airway support provided as needed, and IV fluids (such as normal saline) given for blood pressure support. Parenteral H1 (diphenhydramine) and H2 (Ranitidine) antihistamines may also be administered. Inhaled beta-1 agonists can be given prophylactically or if bronchospasm is present. Repeat doses of medication such as epinephrine should be given as needed and vasopressor agents given when indicated. Although steroids will not alter the acute course of anaphylaxis, they may be given to attenuate a subsequent late phase response. The aggressiveness of the above outlined therapy depends on the severity of the anaphylaxis and the response to treatment.