What is the treatment for anaphylaxis?

Treatment of Anaphylaxis

Immediately administer intramuscular epinephrine 0.01 mg/kg (maximum 0.5 mg in adults, 0.3 mg in children) into the anterolateral thigh—this is the first-line, life-saving treatment with no absolute contraindications. 1, 2, 3

Immediate First-Line Management

Stop the Trigger and Give Epinephrine

• Stop any ongoing infusion or exposure to the suspected allergen immediately 1, 4
• Administer intramuscular epinephrine into the vastus lateralis muscle of the anterolateral thigh for optimal absorption 1, 2, 4
• Dose: 0.01 mg/kg of 1:1000 concentration (1 mg/mL), with maximum single dose of 0.5 mg for adults (>50 kg) and 0.3 mg for children 1, 2, 3
• Repeat epinephrine every 5-15 minutes as needed if symptoms persist or recur 2, 4

Autoinjector Dosing (Alternative to Drawing Up)

• 0.15 mg for children weighing 10-25 kg 2
• 0.30 mg for individuals weighing ≥25 kg 2
• 0.1 mg for infants where available (or 0.15 mg if >7.5 kg when 0.1 mg unavailable) 2
• Autoinjectors minimize dosing errors and expedite delivery when staff experience is limited 1

Critical Considerations About Epinephrine

• There are NO absolute contraindications to epinephrine in anaphylaxis—use it even in elderly patients, those with cardiac disease, frailty, complex congenital heart disease, or pulmonary hypertension 1, 2, 4
• Delayed epinephrine administration is associated with fatalities and increased risk of biphasic reactions 1, 4
• Intramuscular administration in the thigh provides superior pharmacokinetics compared to subcutaneous injection 2, 5

Supportive Care (Secondary to Epinephrine)

Airway, Breathing, Circulation

• Establish and maintain airway patency 4
• Administer high-flow oxygen at 6-8 L/min 4
• Establish IV access and begin aggressive fluid resuscitation with normal saline for hypotension 1, 4

Adjunctive Medications (Only AFTER Epinephrine)

• H1 antihistamines (diphenhydramine or chlorphenamine 25-50 mg IV) for cutaneous symptoms only—never give before or instead of epinephrine 2
• H2 antihistamines (ranitidine 50 mg IV in adults) may be added after H1 blockers 2
• Bronchodilators for persistent bronchospasm after epinephrine stabilization 1
• Corticosteroids are secondary treatments with no immediate benefit 1

Management of Severe or Refractory Anaphylaxis

When Initial IM Epinephrine Fails

• For persistent symptoms after initial epinephrine, consider IV epinephrine boluses: 2
  • 20 μg for Grade II reactions
  • 50-100 μg for Grade III reactions
  • 1 mg for Grade IV reactions (cardiac arrest—follow ACLS)
• For protracted anaphylaxis requiring >3 epinephrine boluses, start epinephrine infusion at 0.05-0.1 μg/kg/min 2
• Alternative IV epinephrine preparation: 1:10,000 concentration (1 mg/10 mL) administered slowly 1, 4

Special Situation: Beta-Blocker Use

• Patients on beta-blockers who are unresponsive to epinephrine should receive glucagon 1-5 mg IV over 5 minutes, followed by infusion at 5-15 μg/min 4

Post-Acute Management and Observation

Monitoring Period

• Observe all patients for minimum 6 hours in a monitored setting after symptom resolution 2, 4
• Biphasic reactions can occur up to 72 hours after initial reaction, with higher risk in severe initial presentations 4
• Early epinephrine administration may reduce biphasic reaction risk 4

Diagnostic Testing

• Obtain mast cell tryptase levels at three time points: 2
  • First sample at 1 hour after reaction onset
  • Second sample at 2-4 hours
  • Baseline sample at least 24 hours post-reaction

Common Pitfalls to Avoid

Distinguishing Anaphylaxis from Vasovagal Reactions

• Vasovagal reactions present with bradycardia (not tachycardia) and lack cutaneous manifestations (no urticaria, angioedema, flushing, or pruritus) 1, 4
• In anaphylaxis, tachycardia precedes any bradycardia; in vasovagal reactions, bradycardia occurs immediately 1
• Patients prone to vasovagal reactions are NOT candidates for premedication 1

Critical Errors to Avoid

• Never delay epinephrine while giving antihistamines or corticosteroids first—this delay kills patients 1, 2, 5, 6
• Avoid subcutaneous epinephrine—delayed onset of action compared to IM 5
• Avoid IV epinephrine as first-line unless cardiac arrest—increased risk of adverse cardiac effects when given as initial therapy 7
• Do not inject epinephrine into fingers when using autoinjectors—inject into thigh only 1