A nurse is caring for a client experiencing anaphylaxis after receiving a penicillin injection. The client is hypotensive, has difficulty breathing, and shows signs of laryngeal edema. What is the priority nursing intervention?

In anaphylaxis, epinephrine is the first-line treatment and must be administered immediately to counteract severe allergic reaction and prevent cardiovascular collapse. Other interventions like oxygen, IV access, and positioning are supportive but secondary.

Understanding Anaphylaxis Pathophysiology
Anaphylaxis is a severe, systemic hypersensitivity reaction that can rapidly become life-threatening ^[1][2]. When an allergen such as penicillin enters a previously sensitized client, it triggers massive degranulation of mast cells and basophils, releasing histamine, leukotrienes, and prostaglandins. These mediators cause profound vasodilation, increased capillary permeability, and bronchoconstriction. The client’s hypotension results from fluid shifting out of the vascular space (relative hypovolemia) combined with vasodilation, while difficulty breathing and laryngeal edema stem from airway mucosal swelling and bronchospasm. Without immediate intervention, cardiovascular collapse and respiratory failure can occur ^[1][2].

Priority Intervention: Epinephrine Administration
The priority nursing intervention is to administer epinephrine 1:1000 intramuscularly into the anterolateral thigh immediately. Epinephrine is the first-line drug for anaphylaxis because it directly counteracts the underlying pathophysiology ^[1]. It acts as an alpha-adrenergic agonist, causing vasoconstriction that reverses hypotension and decreases mucosal edema, including laryngeal swelling. As a beta-adrenergic agonist, it provides bronchodilation to ease breathing difficulty and suppresses further release of inflammatory mediators from mast cells ^[1]. Delaying epinephrine administration is associated with poor outcomes, including progression to refractory anaphylactic shock, which may require second-line vasopressors and mechanical ventilation ^[2].

Why Other Options Are Not the Priority
Administering high-flow oxygen (Option 1) is critical for hypoxia but does not reverse the underlying vasodilation, bronchoconstriction, or edema. Establishing large-bore IV access for fluid resuscitation (Option 2) is an essential second step to restore intravascular volume, as fluid shifts cause relative hypovolemia ^[1]. However, fluid alone will not correct vasodilation or airway compromise without the pharmacologic action of epinephrine. Positioning the client in Trendelenburg (Option 4) is not recommended in anaphylaxis; it can worsen respiratory distress by increasing pressure on the diaphragm and may exacerbate cerebral edema. The immediate focus must be on halting the release of mediators and reversing their effects, which only epinephrine achieves ^[1].

Clinical Implications and Vigilance
Early recognition of anaphylaxis signs—hypotension, respiratory distress, and laryngeal edema—is essential for prompt epinephrine administration ^[1]. The intramuscular route into the vastus lateralis muscle provides the most rapid absorption in a shocked client. If there is an insufficient response to the initial dose, repeat doses may be required, and refractory anaphylaxis can develop, defined as ongoing symptoms despite two appropriate epinephrine doses . In such cases, advanced support including continuous vasopressor infusions and mechanical ventilation may become necessary ^[2]. Additionally, clinicians must be aware of biphasic reactions, where symptoms recur after initial resolution, requiring extended monitoring even after a full clinical response .