What is the treatment for anaphylaxis due to peanut allergy with respiratory distress, hypotension, and hypoxemia?

Treatment of Anaphylaxis from Peanut Allergy

Immediately administer intramuscular epinephrine 0.3-0.5 mg (1:1000 concentration) into the anterolateral thigh (vastus lateralis muscle), activate emergency medical services, place the patient supine, administer high-flow supplemental oxygen, establish IV access for aggressive fluid resuscitation with normal saline, and prepare to repeat epinephrine every 5-15 minutes if symptoms persist. 1

Immediate First-Line Treatment

Epinephrine Administration

• Epinephrine is the only first-line treatment for anaphylaxis and must never be delayed or substituted with antihistamines or other medications 1, 2
• Administer 0.01 mg/kg of 1:1000 (1 mg/mL) epinephrine intramuscularly, with a maximum single dose of 0.5 mg in adults and 0.3 mg in children 1, 2
• Inject into the anterolateral thigh (vastus lateralis muscle) for optimal absorption—this is superior to subcutaneous injection which delays onset of action 1, 2
• Repeat epinephrine every 5-15 minutes if symptoms persist or worsen, as 7-18% of patients require multiple doses 1
• There are no absolute contraindications to epinephrine use in anaphylaxis—the risk of death from untreated anaphylaxis far outweighs any potential adverse effects 1

Critical Supportive Measures (Concurrent with Epinephrine)

• Activate emergency medical services immediately as this patient requires advanced care and monitoring 1
• Position the patient supine to optimize cardiovascular perfusion given the hypotension (BP 89/50) 1
• Administer high-flow supplemental oxygen immediately to address the hypoxemia (O2 sat 87%) and respiratory distress 1
• Establish large-bore IV access for aggressive fluid resuscitation 1

Aggressive Fluid Resuscitation

• Administer large-volume normal saline boluses immediately as anaphylaxis can cause up to 35% of intravascular volume to shift into the extravascular space within minutes 1
• Any patient with hypotension (BP 89/50) or incomplete response to initial epinephrine requires immediate large-volume fluid resuscitation 1
• Continue fluid boluses until blood pressure stabilizes 1

Adjunctive Respiratory Management

Bronchodilators

• Administer nebulized albuterol for the bronchospasm and diminished breath sounds that are not responsive to initial epinephrine 1, 2
• Albuterol is adjunctive only and does not relieve upper airway edema (laryngeal edema/stridor)—it cannot substitute for epinephrine 1
• Nebulized therapy is preferred over metered-dose inhalers in severe respiratory distress 1

Airway Management Preparation

• Given the stridor, diminished breath sounds, and severe respiratory distress (RR 32, O2 sat 87%), prepare for potential endotracheal intubation as this patient may require advanced airway management 1
• Have equipment ready for emergency cricothyrotomy if complete airway obstruction develops 1

Refractory Hypotension Management

If hypotension persists despite repeated epinephrine and aggressive fluid resuscitation:

• Consider IV epinephrine infusion (1:10,000 solution) for patients not responding to IM epinephrine and who may not be adequately perfusing muscle tissues 1
• Initiate vasopressor infusion (such as dopamine) titrated to restore blood pressure 1, 2
• Continuous hemodynamic monitoring is essential when using IV epinephrine or vasopressors 1

Secondary Medications (Never First-Line)

H1 Antihistamines

• Administer diphenhydramine 25-50 mg IV as adjunctive therapy only for urticaria and itching 1, 2
• Antihistamines do not relieve stridor, shortness of breath, wheezing, or shock and must never substitute for epinephrine 1, 2

Corticosteroids

• Consider methylprednisolone 1-2 mg/kg IV to potentially prevent biphasic reactions (which occur in up to 20% of cases) 1, 2
• Corticosteroids have no role in acute symptom relief due to their 4-6 hour onset of action 1
• If administered, continue for 2-3 days maximum as all biphasic reactions occur within 3 days 1

H2 Antihistamines

• Consider famotidine or ranitidine IV in combination with H1 antihistamines, though evidence is limited 1

Special Considerations

Tachycardia Management

• The heart rate of 154 is an appropriate compensatory response to hypotension and hypoxemia—do not treat with beta-blockers 1
• Focus on treating the underlying anaphylaxis with epinephrine and fluids, which will normalize heart rate 1

Monitoring for Biphasic Reactions

• All patients with anaphylaxis require hospital admission and observation for at least 4-8 hours due to risk of biphasic reactions 2
• This patient's severe presentation (hypotension, respiratory compromise, hypoxemia) mandates ICU-level monitoring 1

Critical Pitfalls to Avoid

• Never delay epinephrine while administering antihistamines or corticosteroids—delay in epinephrine administration is associated with anaphylaxis fatalities 2, 3
• Never use subcutaneous epinephrine instead of intramuscular—absorption is significantly delayed 2, 3
• Never administer IV epinephrine as a bolus outside of cardiac arrest—use only as a controlled infusion with continuous monitoring 1, 4
• Never rely on antihistamines or bronchodilators alone—they do not address the life-threatening cardiovascular and upper airway components 1, 2
• Do not hesitate to give repeat doses of epinephrine—waiting too long between doses increases mortality risk 1