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Difficulty: HardPharmacologic Interventions

A 55-year-old man is brought to the emergency department by emergency medical services 15 minutes after being stung by multiple wasps while gardening. He complains of a feeling of impending doom, difficulty breathing, and dizziness. His medical history is significant for hypertension, coronary artery disease, and heart failure with reduced ejection fraction. His current medications include lisinopril, carvedilol, aspirin, and atorvastatin. On arrival, he is in severe respiratory distress with audible stridor. His temperature is 37.0°C (98.6°F), blood pressure is 72/4072/40 mm Hg, pulse is 110110/min, and oxygen saturation is 88%88\% on room air. Physical examination reveals diffuse wheezing bilaterally, periorbital edema, and a widespread urticarial rash. Arrange the following pharmacologic interventions in the most appropriate sequential order for the optimal acute management of this patient's condition.

  1. 1Intramuscular epinephrine
  2. 2Rapid intravenous normal saline bolus
  3. 3Intravenous glucagon
  4. 4Intravenous methylprednisolone

Answer

The correct sequential order is: 1) Intramuscular epinephrine, 2) Rapid intravenous normal saline bolus, 3) Intravenous glucagon, 4) Intravenous methylprednisolone.
The standard protocol for severe anaphylactic shock prioritizes immediate, life-saving intramuscular epinephrine. This is rapidly followed by intravenous fluid resuscitation to correct distributive shock. In patients chronically taking beta-blockers, the efficacy of epinephrine is blunted, necessitating the subsequent administration of intravenous glucagon, which acts independently of beta-receptors to increase myocardial cAMP. Finally, intravenous corticosteroids are given as an adjunctive measure; they have a delayed onset of several hours and are solely intended to prevent biphasic reactions, placing them last in the acute treatment sequence.

Step-by-Step Solution

1
Administer intramuscular epinephrine
Immediate alpha-1, beta-1, and beta-2 receptor agonism.
This is the universal first step in anaphylaxis to reverse life-threatening airway compromise and cardiovascular collapse.
2
Administer rapid intravenous normal saline bolus
Expansion of the intravascular volume compartment.
Anaphylaxis causes severe distributive shock due to massive capillary leak; volume expansion is required sequentially as intravenous access is established.
3
Administer intravenous glucagon
Increased intracellular cAMP independent of the beta-adrenergic receptor.
The patient is taking carvedilol, making him prone to beta-blocker-induced refractory anaphylaxis. Glucagon provides necessary inotropic and chronotropic support when epinephrine is blunted.
4
Administer intravenous methylprednisolone
Modulation of gene transcription to downregulate the systemic inflammatory response.
Steroids are adjunctive therapies given after acute stabilization to prevent late-phase (biphasic) anaphylactic reactions.

Key Concept

Sequential Pharmacologic Management of Anaphylactic Shock in Patients on Beta-Blockers
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Topics

Pharmacologic Interventions

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