Question

question #4

why do we administer epinephrine to a patient experiencing an anaphylactic reaction?

to increase heart rate.
to neutralize the allergen.
to constrict blood vessels.
to constrict the bronchioles.

Explanation:

Analyze the pathophysiology of anaphylaxis

Using the Anaphylaxis Management knowledge point
Anaphylaxis is a severe, life-threatening systemic allergic reaction characterized by widespread vasodilation (which leads to severe hypotension and distributive shock) and bronchoconstriction (which causes airway obstruction and respiratory distress).

Evaluate the physiological effects of epinephrine

Using the Epinephrine Indications knowledge point
Epinephrine acts as an agonist on alpha-1, beta-1, and beta-2 adrenergic receptors:

• Alpha-1 receptor stimulation causes vasoconstriction (constriction of blood vessels), which reverses systemic vasodilation and elevates blood pressure.
• Beta-2 receptor stimulation causes bronchodilation (relaxation of bronchial smooth muscle), which relieves airway obstruction.
• Beta-1 receptor stimulation increases heart rate and contractility.

Match effects to the given options

• To increase heart rate: While epinephrine does increase heart rate (via \(\beta_1\) receptors), this is a side effect rather than the primary therapeutic reason we administer it to reverse the life-threatening distributive shock of anaphylaxis.
• To neutralize the allergen: Epinephrine does not interact with or neutralize allergens.
• To constrict blood vessels: This directly addresses the life-threatening vasodilation and hypotension associated with anaphylactic shock by stimulating \(\alpha_1\) receptors.
• To constrict the bronchioles: Epinephrine dilates (relaxes) the bronchioles rather than constricting them.

Therefore, the most accurate therapeutic reason among the choices is to constrict blood vessels.

Answer:

• To increase heart rate.
• To neutralize the allergen.
• To constrict blood vessels. (Correct answer)
• To constrict the bronchioles.