What is the treatment protocol for a patient experiencing anaphylaxis?

Treatment Protocol for Anaphylaxis

Immediately administer intramuscular epinephrine 0.3-0.5 mg (1:1000 concentration) into the mid-outer thigh (vastus lateralis) as soon as anaphylaxis is recognized—this is the only first-line treatment and delays in administration are associated with fatal outcomes. 1, 2

Immediate Recognition and Initial Actions

Anaphylaxis presents with sudden onset (minutes to hours) involving multiple organ systems 3:

• Skin/mucosal: Itching, hives, swelling, flushing 3
• Respiratory: Throat tightness, stridor, wheeze, difficulty breathing, cyanosis 3
• Cardiovascular: Hypotension, tachycardia, weak pulse, dizziness, syncope, collapse 3
• Gastrointestinal: Nausea, vomiting, crampy abdominal pain, diarrhea 3
• Neurologic: Sense of doom, confusion, altered mental status 3

Call for help immediately: Activate 911/EMS in community settings or resuscitation team in healthcare facilities while simultaneously beginning treatment 2.

First-Line Treatment: Epinephrine Administration

Dosing and Route

Intramuscular injection into the vastus lateralis (mid-outer thigh) is the method of choice because it produces higher and more rapid peak plasma levels compared to deltoid or subcutaneous routes 3, 1:

• Adults and adolescents >50 kg: 0.3-0.5 mg of 1:1000 epinephrine IM 3, 2, 4
• Prepubertal children: 0.01 mg/kg IM (maximum 0.3 mg) 3, 2
• Can inject through clothing if using autoinjector 3

Repeat Dosing

Repeat epinephrine every 5-15 minutes as needed if symptoms persist or recur 3, 1, 2. Approximately 6-19% of pediatric patients and 17% of all patients require a second dose 3. There is no absolute contraindication to epinephrine in anaphylaxis 3, 2.

Critical Pitfall to Avoid

Never use subcutaneous injection or delay for IV access—subcutaneous administration delays absorption, and IV epinephrine should only be used for cardiac arrest or profound hypotension unresponsive to IM epinephrine due to risk of lethal arrhythmias 3, 1.

Patient Positioning

Place patient supine with lower extremities elevated 3, 2. If respiratory distress or vomiting is present, position for comfort 3, 2. Never allow the patient to stand, walk, or run—this can precipitate cardiovascular collapse 3, 2.

Supportive Measures (After Epinephrine)

Airway and Breathing

• Administer supplemental oxygen at 6-8 L/min 3, 2
• Establish and maintain airway; consider endotracheal intubation or cricothyrotomy if needed 3
• For bronchospasm resistant to epinephrine: Nebulized albuterol 1, 2

Circulation and Fluid Resuscitation

• Establish IV access 3
• Administer normal saline rapidly: 5-10 mL/kg in first 5 minutes for adults (1-2 L total); up to 30 mL/kg in first hour for children 3
• Large volumes of crystalloid may be required; consider colloid-containing solutions if hypotension persists 3

Second-Line Adjunctive Treatments (Never Substitutes for Epinephrine)

Antihistamines

H1 antihistamines (diphenhydramine) can be administered as second-line therapy only after epinephrine 1, 2. Combination of H1 and H2 antihistamines is superior to H1 alone, but both remain second-line 1. Use oral liquid formulations for faster absorption 2.

Glucocorticoids

Systemic corticosteroids have no role in acute anaphylaxis due to slow onset of action 1. Consider for patients with history of idiopathic anaphylaxis, asthma, or severe/prolonged reactions 1. If given, use IV at 1.0-2.0 mg/kg/day equivalent, every 6 hours 3.

Management of Refractory Anaphylaxis

For Persistent Hypotension Despite Epinephrine and Fluids

Consider continuous epinephrine infusion: Add 1 mg (1 mL) of 1:1000 epinephrine to 250 mL D5W (4 mcg/mL concentration), infuse at 1-4 mcg/min initially, titrate up to maximum 10 mcg/min for adults 3. Alternatively, use vasopressor infusion such as dopamine with continuous hemodynamic monitoring 1, 2.

For Patients on Beta-Blockers

Consider glucagon infusion: 1-5 mg IV over 5 minutes, followed by 5-15 mcg/min infusion titrated to response 1, 2. Note that rapid glucagon administration can induce vomiting 2.

Observation and Monitoring

All patients must be transferred to an emergency department for observation, preferably by EMS vehicle 3, 2. Minimum observation period is 4-6 hours due to risk of biphasic reactions (recurrence without re-exposure) 1, 2, 5. Prolonged observation or admission is warranted for:

• Severe or refractory symptoms 2
• History of biphasic reactions 2
• Coexisting asthma (especially if severe or poorly controlled) 3, 1
• Adolescents and young adults 2
• Peanut/tree nut allergies 2

Discharge Planning

Before discharge, ensure 1, 2:

• Two epinephrine autoinjectors prescribed with proper training on use
• Written anaphylaxis emergency action plan provided
• Referral to allergist for evaluation and trigger identification
• Education on trigger avoidance, signs/symptoms recognition, and biphasic reaction risk

High-Risk Populations Requiring Heightened Vigilance

Fatal anaphylaxis is associated with 3, 1, 2:

• Adolescence and young adulthood
• Concomitant asthma (especially severe or poorly controlled)
• Previous history of anaphylaxis
• Peanut and tree nut allergies
• Failure to inject epinephrine promptly