Review Question - QID 100602

This clinical scenario is consistent with anaphylactic shock, the treatment of which is intramuscular epinephrine in the lateral thigh. Epinephrine is an alpha-1 and beta-1 agonist.

Anaphylaxis is a severe form of a type I hypersensitivity reaction. Bee stings are the most common cause of death from venomous insect/animal bites in the US, secondary to anaphylactic shock. Signs and symptoms include rash, dyspnea (secondary to laryngotracheal edema), and cardiovascular collapse. Treatment with epinephrine increases blood pressure (alpha-1 agonism), increases cardiac contractility (beta-1 agonism) and causes bronchodilation (beta-2 agonism).

Arnold and Williams describe the epidemiology and pathophysiology of anaphylaxis. This condition is usually immunoglobulin E-mediated, leading to mast cell and basophil activation. This cascade results in dermatologic, respiratory, cardiovascular, gastrointestinal, and neurologic symptoms, dermatologic and respiratory being the most common. The three most common stimuli are food, insect stings, and medications.

Dhami et al. performed a systematic literature review of the acute management of anaphylaxis. Drugs currently used include epinephrine (first line for severe reactions), H1-antihistamines, systemic glucocorticosteroids, and methylxanthines. Long term prevention mainly includes allergen-specific immunotherapy.

Illustration A shows a child with a severe allergic reaction. While there appears to be no facial edema this could progress further into anaphylactic shock without treatment.

Incorrect Answers:
Answer 2: No single drug can agonize alpha-1 while antagonizing beta-1.
Answer 3: No single drug can antagonize alpha-1 while agonizing beta-1.
Answer 4: Labetalol is an example of an alpha-1 and beta-1 antagonist and is not used in anaphylactic shock.
Answer 5: Midodrine is an example of a selective alpha agonist and is not used in anaphylactic shock.