What are the guidelines for epinephrine (adrenaline) administration in anaphylaxis and severe angioedema?

Epinephrine Guidelines in Anaphylaxis and Angioedema

Epinephrine is the first-line treatment for anaphylaxis and severe angioedema, and should be administered immediately upon recognition of symptoms via intramuscular injection into the anterolateral thigh at a dose of 0.01 mg/kg (maximum 0.3 mg in children, 0.3-0.5 mg in adults). 1, 2

Dosing Guidelines

Adults and Children ≥30 kg:

• 0.3-0.5 mg (0.3-0.5 mL) of 1:1000 concentration epinephrine
• Administered intramuscularly into the anterolateral thigh
• May repeat every 5-10 minutes as necessary 1, 2

Children <30 kg:

• 0.01 mg/kg (0.01 mL/kg) of 1:1000 concentration epinephrine
• Maximum single dose: 0.3 mg (0.3 mL)
• Administered intramuscularly into the anterolateral thigh
• May repeat every 5-10 minutes as necessary 3, 2

Auto-injector Selection:

• 7.5-25 kg: 0.15 mg auto-injector
• ≥25 kg: 0.3 mg auto-injector 3

Administration Technique

• Preferred route: Intramuscular injection into the anterolateral thigh (vastus lateralis muscle)
• This route achieves peak plasma concentrations in approximately 8 minutes
• Significantly faster absorption than subcutaneous administration 3, 4
• May be administered through clothing if necessary 2
• Do not administer repeated injections at the same site (risk of tissue necrosis) 2
• Do not inject into buttocks, digits, hands, or feet 2

Management Algorithm for Anaphylaxis

1. Immediate intervention:

   • Assess airway, breathing, circulation, and mental status
   • Administer epinephrine intramuscularly as outlined above
   • Place patient in recumbent position with lower extremities elevated 1

2. Subsequent measures (based on response to epinephrine):

   • Establish and maintain airway
   • Administer oxygen (6-8 L/min)
   • Establish venous access
   • Administer normal saline for fluid replacement 1

3. For refractory anaphylaxis:

   • Repeat epinephrine doses
   • Consider epinephrine infusion in severe cases (hospital setting)
   • Transfer to acute-care facility/ICU for treatment and monitoring 1

Monitoring and Observation

• All patients who receive epinephrine should be observed for 4-6 hours or longer based on severity of reaction 1, 3
• Extended observation is recommended for patients with:
  • Severe anaphylaxis
  • Need for >1 dose of epinephrine
  • History of biphasic reactions
  • Cardiovascular comorbidities
  • Lack of access to emergency care 1

Biphasic Reactions

• Risk factors include severe anaphylaxis and/or need for >1 dose of epinephrine 1
• 7-18% of people with anaphylaxis require >1 dose of epinephrine 1
• Most patients who require a second dose improve after administration 1
• If a person with anaphylaxis does not respond to the initial dose and EMS arrival will exceed 5-10 minutes, a repeat dose may be considered 1

Adjunctive Treatments

• H1 antihistamines, H2 antihistamines, and corticosteroids are considered secondary treatments 1
• These should never delay or substitute for epinephrine administration 1, 3
• Antihistamines may treat urticaria and itching but do not treat the life-threatening aspects of anaphylaxis 1
• Corticosteroids have not been proven to prevent biphasic reactions 1

Special Considerations

• No absolute contraindications to epinephrine use in anaphylaxis 1, 5
• Use with caution in elderly patients and those with:
  • Underlying cardiac disease
  • Hyperthyroidism
  • Parkinson's disease
  • Diabetes
  • Pheochromocytoma 3
• In obese patients, standard auto-injector needle length may not reach muscle 3

Patient Education

All patients should receive:

• Epinephrine auto-injector prescription and training
• Education on allergen avoidance
• Anaphylaxis emergency action plan
• Medical identification jewelry or wallet card
• Follow-up with allergist/immunologist 1

Common Pitfalls to Avoid

1. Delayed administration: The most common error in anaphylaxis management is delaying or withholding epinephrine 4, 6
2. Substituting antihistamines: Using antihistamines instead of epinephrine as first-line treatment 1
3. Incorrect injection site: Administering into areas other than the anterolateral thigh 2
4. Inadequate monitoring: Discharging patients too early without proper observation 1, 3
5. Insufficient prescribing: Not providing patients with two epinephrine auto-injectors for emergency use 6

Prompt recognition and immediate epinephrine administration remain the cornerstone of anaphylaxis management, with the potential to significantly reduce morbidity and mortality.