Why Is Epinephrine the First-Line Treatment for Anaphylactic Shock?
Aug 06, 2021
Source: Cainiu Health
Dr. Sun Yinghua
Introduction
Why epinephrine is the first-line treatment for anaphylactic shock: Epinephrine directly stimulates both α- and β-adrenergic receptors. Stimulation of cardiac β₁ receptors enhances myocardial contractility and increases cardiac output; stimulation of vascular α receptors induces vasoconstriction and elevates blood pressure; and stimulation of β₂ receptors relaxes bronchial smooth muscle. Collectively, these effects precisely counteract the symptoms of anaphylactic shock.
Anaphylactic shock refers to a severe, life-threatening, multi-organ reaction occurring rapidly after exposure to exogenous antigenic stimuli—such as house dust mites, pollen, and animal dander—that trigger an immune-mediated response.
Epinephrine directly stimulates both α- and β-adrenergic receptors. Stimulation of cardiac β1 receptors enhances myocardial contractility, increases heart rate and conduction velocity, and augments cardiac output.
Stimulation of vascular α receptors induces vasoconstriction, thereby increasing peripheral vascular resistance and elevating blood pressure. It also causes constriction of bronchial mucosal vessels, helping to reduce bronchial mucosal edema and decrease bronchial secretions. Stimulation of β2 receptors relaxes bronchial smooth muscle and inhibits mast cell release of allergic mediators. Collectively, these effects effectively reverse the key manifestations of anaphylactic shock—including hypotension and bronchospasm—making epinephrine the first-line drug of choice for anaphylactic shock.
