What is the treatment protocol for anaphylaxis?

Anaphylaxis Treatment Protocol

Immediately administer intramuscular epinephrine 0.01 mg/kg (maximum 0.5 mg in adults, 0.3 mg in children) into the anterolateral thigh as soon as anaphylaxis is recognized—this is the single most critical intervention that saves lives. 1, 2

Immediate Recognition and First Actions

• Stop any ongoing allergen exposure (e.g., halt intravenous contrast infusion, discontinue medication administration) 3
• Call for help immediately—activate emergency medical services or resuscitation team while simultaneously beginning treatment 2
• Do not delay epinephrine administration while waiting for help or additional assessment—delays in epinephrine are associated with fatalities 3, 1

First-Line Treatment: Epinephrine Administration

Epinephrine is the only first-line treatment for anaphylaxis with no absolute contraindications, even in elderly patients with cardiac disease, complex congenital heart disease, or pulmonary hypertension. 3, 1

Dosing and Route

• Adults and adolescents >50 kg: 0.3-0.5 mg intramuscular (0.3-0.5 mL of 1:1000 concentration) 2, 4
• Children: 0.01 mg/kg intramuscular (maximum 0.3 mg for prepubertal children) 1, 2
• Inject into the vastus lateralis muscle (mid-outer anterolateral thigh)—this achieves faster and higher plasma levels than subcutaneous or deltoid administration 3, 1
• Repeat every 5-15 minutes as needed if symptoms persist or recur 1

Autoinjector Dosing

• 0.15 mg for children weighing 10-25 kg 1
• 0.30 mg for individuals weighing ≥25 kg 1
• 0.1 mg for infants where available (or 0.15 mg if >7.5 kg when 0.1 mg unavailable) 1

Patient Positioning

• Place patient supine with legs elevated to combat hypotension from vasodilation and capillary leak 1, 2
• Exception: If respiratory distress or vomiting present, position for comfort 2
• In pregnant women: Perform left uterine displacement to avoid aortocaval compression 1
• Never allow patient to stand, walk, or run—this can precipitate cardiovascular collapse 2

Supportive Care (Concurrent with Epinephrine)

Oxygen and IV Access

• Administer supplemental oxygen for any respiratory symptoms 1, 2
• Establish intravenous access immediately 1

Fluid Resuscitation

• Grade II reactions: Initial bolus 0.5 L crystalloids 1
• Grade III reactions: Initial bolus 1 L crystalloids 1
• Repeat boluses as needed up to 20-30 mL/kg based on clinical response 1
• Large-volume fluid resuscitation is imperative for hypotension or incomplete response to epinephrine 1, 2

Management of Refractory Anaphylaxis

If symptoms persist after 2-3 doses of intramuscular epinephrine, escalate to intravenous epinephrine or infusion. 1

IV Epinephrine Dosing

• Grade II reactions: 20 μg IV 1
• Grade III reactions: 50-100 μg IV 1
• Grade IV reactions (cardiac arrest): 1 mg IV following advanced life support guidelines 1
• Epinephrine infusion: 0.05-0.1 μg/kg/min when >3 boluses have been administered 1

Alternative Vasopressors

• Consider norepinephrine, vasopressin, phenylephrine, or metaraminol for persistent hypotension despite epinephrine 1

Special Populations

• Patients on beta-blockers: May require glucagon IV 1-2 mg 1
• Extreme cases: Consider extracorporeal life support 1

Second-Line Adjunctive Therapies (ONLY After Epinephrine)

Antihistamines and corticosteroids should never be given before or in place of epinephrine—they address only minor symptoms and do not prevent life-threatening complications. 3, 1

• H1 antihistamines (chlorphenamine or diphenhydramine 25-50 mg IV): For cutaneous symptoms only 1
• H2 antihistamines (ranitidine 50 mg IV in adults): May be added after H1 antihistamines 1
• Albuterol nebulizer or MDI: For persistent bronchospasm 2
• Corticosteroids: May prevent biphasic reactions but have no role in acute stabilization 3

Observation Period

• Minimum 6 hours observation in a monitored area for all patients, or until stable and symptoms regressing 1, 2
• Grade III-IV reactions: Typically require ICU admission 1
• High-risk patients (severe anaphylaxis, required >1 dose epinephrine, history of biphasic reactions): May require extended observation up to 6 hours or more 1, 2
• Biphasic reactions (recurrence without re-exposure) can occur in 4-12 hours 5

Diagnostic Testing

Mast Cell Tryptase Sampling

• First sample: 1 hour after reaction onset 1
• Second sample: 2-4 hours after onset 1
• Baseline sample: At least 24 hours post-reaction for comparison 1

Discharge Planning

Before discharge, ensure:

• Two epinephrine autoinjectors prescribed with proper training on use 2
• Written anaphylaxis emergency action plan provided 2
• Referral to allergist for evaluation and identification of trigger 2

Critical Pitfalls to Avoid

• Do not confuse vasovagal reactions with anaphylaxis: Vasovagal reactions present with bradycardia and pallor without skin manifestations (urticaria, angioedema, pruritus), whereas anaphylaxis typically presents with tachycardia and cutaneous symptoms 3
• Do not use subcutaneous epinephrine: Onset of action is delayed compared to intramuscular administration 3, 6
• Do not give antihistamines first: This delays life-saving epinephrine and addresses only non-life-threatening cutaneous symptoms 3, 1
• Do not underestimate fluid requirements: Anaphylaxis causes massive capillary leak requiring aggressive volume resuscitation 1