What is the management of anaphylaxis?

Management of Anaphylaxis

Administer intramuscular epinephrine 0.01 mg/kg (maximum 0.3 mg in prepubertal children, 0.5 mg in adults) into the mid-outer thigh immediately upon recognition of anaphylaxis—this is the single most critical intervention that saves lives. 1

Immediate First-Line Treatment

Epinephrine is the only first-line treatment; there are no absolute contraindications to its use in anaphylaxis. 2, 1

• Use 1:1000 concentration (1 mg/mL) administered intramuscularly into the anterolateral thigh (vastus lateralis), as this site produces higher and more rapid peak plasma levels compared to deltoid injection 2, 1
• Dosing: 0.01 mg/kg up to maximum 0.3 mg in prepubertal children or 0.5 mg in adults 2, 1
• For children, use epinephrine auto-injector 0.15 mg if weight 10-25 kg, or 0.3 mg if ≥25 kg 1, 3
• Repeat every 5-15 minutes if symptoms persist or progress—delays in administration are associated with fatality 2, 1, 4
• The more rapidly anaphylaxis develops, the more likely it is to be severe and life-threatening 2

Critical pitfall: Delaying epinephrine while administering antihistamines or bronchodilators increases mortality. When in doubt, administer epinephrine—it is better to err on the side of caution. 2, 5

Immediate Supportive Measures (Concurrent with Epinephrine)

• Call emergency services (911/EMS) immediately 3
• Position patient supine with elevated lower extremities to prevent orthostatic hypotension and improve circulation to vital organs—this positioning is critical as sudden upright positioning can precipitate cardiovascular collapse 1, 3
• Establish intravenous access 2, 1
• Administer supplemental oxygen at 6-8 L/min 2, 1

Fluid Resuscitation (For Hypotension or Poor Response to Epinephrine)

• Administer normal saline rapidly: 1-2 L in adults at 5-10 mL/kg in first 5 minutes 1
• Children may require up to 30 mL/kg in first hour 1
• Up to 7 L of crystalloid may be necessary due to increased vascular permeability that can transfer 50% of intravascular fluid to extravascular space within 10 minutes 1

Airway Management

• Maintain airway patency—consider endotracheal intubation or cricothyroidotomy if laryngeal edema is severe and clinicians are adequately trained 2, 1
• This intervention may be life-saving when upper airway obstruction progresses despite epinephrine 2

Second-Line Adjunctive Therapies (ONLY After Epinephrine)

These medications are adjuncts only and should never replace or delay epinephrine administration. 1, 3

Antihistamines

• H1-antihistamine: diphenhydramine 1-2 mg/kg or 25-50 mg IV/IM (primarily relieves urticaria and itching, not life-threatening symptoms) 1, 6
• H2-antihistamine: ranitidine 50 mg IV in adults (1 mg/kg in children) diluted in 5% dextrose over 5 minutes 1, 6

Bronchodilators

• For bronchospasm resistant to adequate epinephrine doses: nebulized albuterol 2.5-5 mg in 3 mL saline, repeat as necessary 1

Corticosteroids

• Consider for patients with history of idiopathic anaphylaxis, asthma, or severe/prolonged anaphylaxis 2, 1, 6
• Corticosteroids have NO acute benefit (onset 4-6 hours) but may prevent biphasic or protracted reactions 2, 1, 7
• Dosing: IV glucocorticosteroids every 6 hours at 1.0-2.0 mg/kg/day equivalent, or oral prednisone 0.5 mg/kg for less critical episodes 2

Management of Refractory Anaphylaxis

If inadequate response after 10 minutes or more than 2-3 doses of epinephrine: 1, 6

• Double the epinephrine bolus dose 1, 6
• Consider epinephrine infusion at 0.05-0.1 μg/kg/min when more than three boluses have been administered 1, 6
• Add vasopressor for persistent hypotension despite epinephrine and fluids:
  • Norepinephrine infusion 0.05-0.5 μg/kg/min, OR 1, 6
  • Dopamine 2-20 μg/kg/min titrated to maintain systolic BP >90 mmHg 2, 1
• For patients on beta-blockers with refractory symptoms: administer IV glucagon 1-2 mg 6

Cardiopulmonary Arrest During Anaphylaxis

• Initiate CPR and advanced cardiac life support immediately 2, 6
• Administer high-dose IV epinephrine rapidly: 1-3 mg (1:10,000 dilution) over 3 minutes, then 3-5 mg over 3 minutes, followed by 4-10 μg/min infusion 2, 6
• For children: initial resuscitation dose 0.01 mg/kg (0.1 mL/kg of 1:10,000 solution) repeated every 3-5 minutes; higher doses (0.1-0.2 mg/kg) may be considered for unresponsive asystole 2
• Prolonged resuscitation is encouraged—efforts are more likely to be successful in anaphylaxis than other causes of cardiac arrest 2

Observation and Monitoring

Observe ALL patients for minimum 6 hours in a monitored setting, as there are no reliable predictors of biphasic reactions based on initial presentation. 2, 1, 6

• Biphasic reactions (recurrence without re-exposure) occur in up to 20% of cases 1
• Patients with severe reactions, delayed epinephrine administration, or history of biphasic reactions may require longer observation (up to 12 hours) 8

Post-Event Management (Before Discharge)

• Provide patient with TWO epinephrine auto-injectors and comprehensive training on self-administration 1, 3
• Provide written anaphylaxis emergency action plan 3
• Recommend medical identification jewelry (e.g., Medic Alert) 2
• Refer ALL patients to an allergist-immunologist for diagnostic evaluation, identification of triggers, and long-term management including consideration for desensitization or immunotherapy 2, 1

Key Pitfalls to Avoid

• Never substitute antihistamines or bronchodilators for epinephrine—these are adjuncts only 3, 6
• Never administer IV epinephrine in non-arrest situations without appropriate monitoring—several fatalities have been attributed to injudicious IV epinephrine use 2
• Never discharge patients prematurely without adequate observation period—biphasic reactions can occur hours after initial resolution 1, 6
• Never delay epinephrine while obtaining IV access or administering other medications—IM epinephrine can be given immediately without IV access 4, 5