What is the management approach for a patient experiencing anaphylaxis, particularly those with a history of allergies or previous anaphylactic reactions?

Anaphylaxis Management

Immediately administer intramuscular epinephrine 0.3-0.5 mg (0.01 mg/kg in children) into the anterolateral thigh at the first sign of anaphylaxis—this is the only first-line treatment and must not be delayed for any reason. 1, 2, 3

Immediate Recognition and First-Line Treatment

Epinephrine is the drug of choice and the only medication proven to prevent death from anaphylaxis. 2, 3 There are no absolute contraindications to epinephrine administration, even in patients with cardiac disease, advanced age, or those on beta-blockers. 1, 4

Epinephrine Dosing

• Adults and children ≥30 kg: 0.3-0.5 mg IM (0.3-0.5 mL of 1:1000 solution) 2
• Children 10-25 kg: 0.15 mg via autoinjector 5
• All patients: 0.01 mg/kg per dose (maximum 0.5 mg) 5
• Injection site: Vastus lateralis muscle in the anterolateral thigh 1
• Repeat dosing: Every 5-15 minutes as needed if symptoms persist or worsen 5, 2

Critical Action Steps

Stop any suspected triggering agent immediately (medications, infusions, food exposure). 1 Delayed epinephrine administration is directly associated with increased mortality and biphasic reactions—do not wait to confirm the diagnosis if anaphylaxis is suspected. 1, 2

Supportive Care and Adjunctive Measures

After epinephrine administration, implement these concurrent interventions:

Airway and Breathing

• Establish and maintain airway patency 1
• Administer supplemental oxygen at 6-8 L/min 1
• For bronchospasm: Albuterol via MDI (4-8 puffs in children, 8 puffs in adults) or nebulized solution (1.5 mL in children, 3 mL in adults) every 20 minutes 5

Circulation and Positioning

• Place patient in recumbent position with lower extremities elevated if tolerated 5
• Establish IV access immediately 1
• Administer rapid IV fluid bolus: Normal saline 1-2 L at 5-10 mL/kg in first 5 minutes, then crystalloid or colloid boluses of 20 mL/kg for persistent hypotension 5, 2

Adjunctive Medications (Never Replace Epinephrine)

• H1 antihistamine: Diphenhydramine 1-2 mg/kg IV or oral (maximum 50 mg); oral liquid absorbs faster than tablets 5
• H2 antihistamine: Ranitidine 50 mg IV 5
• Corticosteroids: Methylprednisolone 1-2 mg/kg IV every 6 hours (onset 4-6 hours, no immediate effect) 5, 4

These adjunctive medications should never delay epinephrine administration and do not reliably prevent biphasic reactions. 6, 4

Management of Refractory Anaphylaxis

Persistent Hypotension Despite IM Epinephrine

• IV epinephrine: 1:10,000 concentration administered slowly 1
• Epinephrine infusion: 4.0 μg/mL concentration at 1-4 μg/min, increasing to maximum 10 μg/min if needed 1
• Vasopressors: Dopamine 400 mg in 500 mL at 2-20 μg/kg/min OR vasopressin 0.01-0.04 U/min 5

Patients on Beta-Blockers

These patients may be unresponsive to epinephrine. Administer glucagon 1-5 mg IV over 5 minutes, followed by infusion at 5-15 μg/min. 5, 1

Bradycardia

Administer atropine 600 μg IV. 5

Cardiopulmonary Arrest

Initiate CPR and advanced cardiac life support with high-dose IV epinephrine and rapid volume expansion. 1

Observation Period

All patients who receive epinephrine must proceed to an emergency facility for observation, even if symptoms resolve. 5

Minimum Observation Times

• Standard cases: 4-6 hours minimum 5, 6
• Severe anaphylaxis or multiple epinephrine doses: At least 6 hours, consider prolonged observation or hospital admission 1, 2, 6
• High-risk patients: Extended observation (cardiovascular comorbidity, severe initial presentation, unknown trigger) 6

Biphasic Reaction Risk

Biphasic reactions occur in 1-20% of cases, typically around 8 hours after initial reaction but can occur up to 72 hours later. 5, 2, 6 Risk factors include severe initial presentation, wide pulse pressure, unknown trigger, cutaneous manifestations, drug triggers in children, and delayed epinephrine administration. 1, 6

Mandatory Discharge Requirements

Every patient must leave with all of the following—no exceptions: 6

1. Two epinephrine autoinjectors with instructions to carry at all times and self-inject at first sign of symptom recurrence 5, 6
2. Written anaphylaxis emergency action plan 5, 6
3. Proper training on autoinjector technique with demonstration 6
4. Mandatory referral to allergist-immunologist for trigger identification and comprehensive evaluation 1, 6
5. Plan for monitoring autoinjector expiration dates 5

Consider Short-Term Adjunctive Medications

Continue H1 antihistamine, H2 antihistamine, and corticosteroid for 2-3 days post-discharge, though these do not reliably prevent biphasic reactions. 6

High-Risk Populations Requiring Epinephrine Autoinjector Prescription

Prescribe epinephrine autoinjectors for patients with: 5

• Previous systemic allergic reaction or anaphylaxis
• Food allergy combined with asthma (especially poorly controlled)
• Known allergy to peanuts, tree nuts, fish, or crustacean shellfish
• Consider for all patients with IgE-mediated food allergies

Adolescents, young adults, and patients with concomitant asthma are at highest risk for fatal anaphylaxis. 5, 6

Common Pitfalls to Avoid

• Never substitute antihistamines or corticosteroids for epinephrine—these are adjunctive only and have no immediate effect on preventing death. 4
• Do not delay epinephrine while waiting for diagnostic confirmation or IV access. 2, 7
• Never discharge without two autoinjectors and proper training—this is associated with increased mortality. 6
• Do not confuse anaphylaxis with vasovagal reactions, which present with bradycardia (not tachycardia) and lack cutaneous manifestations. 1
• Avoid premature discharge—observation must account for biphasic reaction risk extending up to 72 hours. 6