Anaphylaxis Treatment Protocol
Immediate First-Line Treatment: Intramuscular Epinephrine
Epinephrine intramuscular injection is the only first-line treatment for anaphylaxis and must be administered immediately upon recognition—delays in administration are associated with fatalities. 1, 2
Adult Dosing (IM)
- 0.3–0.5 mg (0.3–0.5 mL of 1:1000 solution) injected into the anterolateral thigh (vastus lateralis) 1, 3
- Maximum single dose capped at 0.5 mg regardless of body weight 4
- Repeat every 5–15 minutes as needed until symptoms resolve 1, 2
- Approximately 10–20% of patients require more than one dose 4
- There is no maximum number of doses—continue every 5 minutes as clinically needed 4
Pediatric Dosing (IM)
- 0.01 mg/kg (0.01 mL/kg of 1:1000 solution), maximum 0.3–0.5 mg per dose 1, 5
- Age-based dosing from guidelines: 6
- >12 years: 500 mcg (0.5 mL of 1:1000); use 300 mcg if child is small
- 6–12 years: 300 mcg (0.3 mL of 1:1000)
- Up to 6 years: 150 mcg (0.15 mL of 1:1000)
- Autoinjector dosing: 0.3 mg for patients ≥30 kg; 0.15 mg for children 15–30 kg 4
- Repeat every 5–15 minutes as needed 1
Critical Administration Details
- Inject into the anterolateral thigh (vastus lateralis muscle)—this achieves peak plasma concentration in 8±2 minutes vs. 34±14 minutes with subcutaneous deltoid injection 4, 7
- Never delay epinephrine to give antihistamines or corticosteroids 1, 2
- Epinephrine has no absolute contraindication in anaphylaxis, even in elderly or cardiac patients—risk of death from untreated anaphylaxis exceeds risk of epinephrine adverse effects 4
Concurrent Immediate Management
Positioning and Monitoring
- Position patient supine with legs elevated (unless respiratory distress prevents this) 1
- Never allow patient to stand or walk—this increases mortality risk 4
- Activate emergency medical services (911) immediately 1, 4
- Begin continuous hemodynamic monitoring (blood pressure, heart rate, oxygen saturation, ECG if available) 1
Airway Management
- Administer 100% oxygen and maintain airway 6
- Intubate if necessary—prepare for emergency cricothyrotomy if rapid oropharyngeal/laryngeal edema develops 6, 1
- Triage to provider with advanced airway expertise promptly 1
Fluid Resuscitation
- Administer 0.9% saline or lactated Ringer's solution at high rate via large-bore IV 6
- Adults: 500–1000 mL (or 1000–2000 mL) bolus 1, 4
- Children: 20 mL/kg bolus 1
- Large volumes may be required due to massive capillary leak 6
Intravenous Epinephrine (Refractory Cases Only)
IV epinephrine should only be used when anaphylaxis is refractory to multiple IM doses and aggressive fluid resuscitation, or during cardiac arrest. 1, 7
IV Bolus Dosing
- Adults: 50–100 mcg (0.05–0.1 mg of 1:10,000 solution) administered slowly IV, repeat as needed 6, 1
- Children: Start with 1 mcg/kg (one-tenth of prepared syringe), titrate to response 6
- Prepare 1 mL of 1:10,000 epinephrine for each 10 kg body weight (yields 10 mcg/kg total)
- Many children respond to as little as 1 mcg/kg 6
- Critical safety warning: Always use 1:10,000 concentration (0.1 mg/mL) for IV to prevent fatal arrhythmias—never use 1:1000 IV 1, 4
IV Infusion Protocol
- Starting rate: 1–4 mcg/min (or 0.05–0.1 mcg/kg/min) 1, 7
- Titrate up to maximum 10 mcg/min based on clinical response 1, 7
- Preparation: Add 1 mg (1 mL) of 1:1000 epinephrine to 250 mL D5W to yield 4 mcg/mL concentration 1, 7
- Pediatric infusion: Start at 0.1 mcg/kg/min, range 0.1–1.0 mcg/kg/min (up to 5 mcg/kg/min in exceptional circumstances) 7
- Requires continuous cardiac monitoring 1, 7
Cardiac Arrest Dosing
- Adults: 1–3 mg (1:10,000) IV over 3 minutes, then 3–5 mg over 3 minutes, followed by infusion at 4–10 mcg/min 1
- Children: 0.01 mg/kg (0.1 mL/kg of 1:10,000), maximum 0.3 mg 1
- Apply standard BLS/ACLS protocols with immediate epinephrine as priority 1
Secondary Medications (Adjunctive Only—No Acute Benefit)
Antihistamines and corticosteroids provide no acute benefit in anaphylaxis and must never delay or replace epinephrine. 1, 2
H1-Antihistamine
- Diphenhydramine 25–50 mg IV/IM (adults) 1
- Children: 1–2 mg/kg IV/IM, maximum 50 mg 1, 4
- Chlorphenamine (alternative): 6
12 years: 10 mg IV/IM
- 6–12 years: 5 mg IV/IM
- 6 months–6 years: 2.5 mg IV/IM
- <6 months: 250 mcg/kg IV/IM
H2-Antihistamine
- Ranitidine 50 mg IV (adults) or 1 mg/kg (children, maximum 75–150 mg) 1
- Famotidine 20 mg IV if ranitidine unavailable 1
- Combination H1 + H2 superior to H1 alone for symptom control 1
Corticosteroids
- Purpose: May prevent biphasic reactions (occur in 7–18% of cases) and protracted anaphylaxis—no acute benefit 1
- Adults: 1
- Methylprednisolone 1–2 mg/kg IV (typically 40 mg IV every 6 hours for 70 kg adult)
- Hydrocortisone 200 mg IV
- Children: 6, 1
12 years: Hydrocortisone 200 mg IV/IM
- 6–12 years: Hydrocortisone 100 mg IV/IM
- 6 months–6 years: Hydrocortisone 50 mg IV/IM
- <6 months: Hydrocortisone 25 mg IV/IM
Treatment of Persistent Bronchospasm
- Albuterol nebulization 2.5–5 mg in 3 mL saline if bronchospasm unresponsive to epinephrine 1
- Consider IV salbutamol infusion or metered-dose inhaler if appropriate connector available 6
- Consider IV aminophylline or magnesium sulfate for refractory bronchospasm 6
Special Populations
Patients on Beta-Blockers
If anaphylaxis is refractory to epinephrine in a patient taking beta-blockers, administer glucagon: 1, 7
- Adults: 1–5 mg IV over 5 minutes, followed by infusion at 5–15 mcg/min 1, 7
- Children: 20–30 mcg/kg (maximum 1 mg) IV over 5 minutes 1, 7
- Glucagon is second-line only—never delays or replaces epinephrine 1
Pregnant Patients
- Same epinephrine dosing as non-pregnant adults (0.3–0.5 mg IM) 1
- Risk of untreated anaphylaxis to mother and fetus far exceeds epinephrine risk 4
Observation and Disposition
- Observe minimum 4–6 hours after symptom resolution 1
- Extend observation for: 1
- Severe anaphylaxis requiring multiple epinephrine doses
- Persistent airway symptoms
- History of biphasic reactions
- Delayed presentation (>1 hour after exposure)
- Biphasic reactions occur in 7–18% of cases and are unpredictable 1
Discharge Protocol
Prescriptions
- Two epinephrine autoinjectors (0.3 mg for adults/children ≥30 kg; 0.15 mg for children 15–30 kg) with hands-on training 1, 4
- Prednisone 1 mg/kg daily (maximum 60–80 mg) for 2–3 days (no taper needed) 1
- H1-antihistamine for 2–3 days 1
- H2-antihistamine twice daily for 2–3 days 1
Follow-Up
- Written anaphylaxis action plan 1
- Allergist referral within 1–2 weeks for formal allergy testing and long-term management 1, 4
Laboratory Testing
Obtain mast cell tryptase levels: 6
- First sample: As soon as feasible after resuscitation starts (do not delay resuscitation)
- Second sample: 1–2 hours after symptom onset
- Third sample: At 24 hours or in convalescence (baseline level)
- Label all samples with time and date 6
Critical Pitfalls to Avoid
- Never delay epinephrine to give antihistamines, corticosteroids, or obtain IV access 1, 2
- Never use subcutaneous route—IM vastus lateralis is superior 4, 3
- Never confuse concentrations: 1:1000 for IM; 1:10,000 for IV only 1, 4
- Never stop at one dose if symptoms persist or progress—repeat every 5 minutes 4, 2
- Never use IV epinephrine as first-line unless cardiac arrest or profound refractory shock 1, 7
- Never discharge prematurely—observe minimum 4–6 hours even if symptoms resolve 1