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Difficulty: HardPharmacologic Interventions

A 62-year-old man is brought to the emergency department by emergency medical services (EMS) due to the sudden onset of difficulty breathing, facial swelling, and a diffuse pruritic rash. The symptoms began 15 minutes ago while he was eating at a seafood restaurant. His medical history is significant for hypertension, coronary artery disease, and heart failure with preserved ejection fraction. His home medications include lisinopril, metoprolol, aspirin, and atorvastatin. Upon arrival, his blood pressure is 74/40 mm Hg, pulse is 62/min, and oxygen saturation is 90% on room air. Physical examination reveals marked angioedema of the lips, widespread urticaria, and diffuse bilateral expiratory wheezing. EMS has established peripheral intravenous access.

Arrange the following pharmacologic interventions in the correct sequential order of administration for the acute escalation of therapy in this patient.

  1. 1Administer intramuscular epinephrine (1:1,0001:1,000) into the anterolateral thigh
  2. 2Administer a rapid intravenous bolus of 0.9% sodium chloride
  3. 3Administer intravenous glucagon
  4. 4Initiate a continuous intravenous epinephrine infusion

Answer

The correct sequence is: 1) Administer intramuscular epinephrine, 2) Administer a rapid intravenous bolus of 0.9% sodium chloride, 3) Administer intravenous glucagon, 4) Initiate a continuous intravenous epinephrine infusion.
The correct sequential management for severe anaphylactic shock in a patient taking beta-blockers follows a distinct escalation pathway. First, intramuscular epinephrine is the absolute first-line therapy and must never be delayed. Second, for persistent hypotension, aggressive intravenous fluid resuscitation with isotonic crystalloids (0.9% sodium chloride) is the next immediate step to counteract massive vasodilation and capillary leak. Third, because this patient is on metoprolol, his beta-adrenergic receptors are blocked, which can render standard epinephrine less effective (evidenced by his lack of compensatory tachycardia). In such refractory cases, intravenous glucagon is administered because it increases intracellular cAMP and provides inotropic and chronotropic effects independent of beta-receptors. Finally, if the patient remains in shock despite these interventions, a continuous intravenous epinephrine infusion is initiated to maintain perfusion.

Step-by-Step Solution

1
Diagnose the acute condition based on the clinical presentation.
The patient is experiencing severe anaphylactic shock.
Sudden onset of dyspnea, angioedema, urticaria, wheezing, and profound hypotension after allergen exposure (seafood) confirm anaphylaxis.
2
Identify the critical home medication influencing the presentation.
The patient is taking metoprolol, a beta-blocker.
The relative bradycardia (pulse 62/min) in the setting of severe distributive shock suggests beta-blockade, which blunts the compensatory tachycardic response and can render standard epinephrine doses ineffective.
3
Select the immediate first-line pharmacologic intervention.
Administer intramuscular epinephrine.
Intramuscular epinephrine is the life-saving first step for all anaphylaxis patients to halt mast cell degranulation, regardless of concurrent beta-blocker use.
4
Determine the next step for persistent distributive shock.
Administer a rapid intravenous bolus of 0.9% sodium chloride.
Aggressive fluid resuscitation is required to counteract the massive capillary leak and vasodilation that occurs in anaphylaxis.
5
Select the specific antidote for beta-blocker-associated refractory anaphylaxis.
Administer intravenous glucagon.
Glucagon bypasses the blocked beta-adrenergic receptors to increase intracellular cAMP, providing essential inotropic and chronotropic support as well as bronchodilation.
6
Identify the final escalation step if the patient remains in shock.
Initiate a continuous intravenous epinephrine infusion.
When intermittent intramuscular doses, fluids, and glucagon fail to restore perfusion, a continuous vasopressor infusion is necessary.

Key Concept

The correct escalation sequence for managing refractory anaphylaxis in a patient on beta-blockers is intramuscular epinephrine, followed by intravenous fluid resuscitation, intravenous glucagon, and finally continuous intravenous epinephrine infusion.
Estimated Time:1m 30s
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Pharmacologic Interventions

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