What is the immediate treatment for a patient experiencing anaphylaxis?

Immediate Treatment of Anaphylaxis

Intramuscular epinephrine 0.3-0.5 mg (adults) or 0.01 mg/kg (children, maximum 0.3 mg) injected into the mid-outer thigh (vastus lateralis) is the first-line, life-saving treatment that must be administered immediately upon recognition of anaphylaxis—there are no absolute contraindications to its use. 1, 2

Recognition and Immediate Action

Anaphylaxis presents with rapid onset (minutes to hours) involving multiple organ systems: 1

• Skin/mucosal: Lip and facial swelling, hives, flushing, pruritus 1
• Respiratory: Throat tightness, stridor, wheezing, dyspnea, sensation of throat closing 1
• Cardiovascular: Hypotension, tachycardia, dizziness, syncope, pallor 1
• Gastrointestinal: Nausea, vomiting, cramping, diarrhea 1
• Neurologic: Altered mental status, sense of doom, confusion 1

Activate emergency medical services (911/EMS) immediately—do not delay while treating. 1, 3 Approximately 500-1,000 people die annually in the United States from anaphylaxis, and patients require advanced interventions beyond first aid. 1

Epinephrine Administration Protocol

Dosing and Route

• Adults and adolescents >50 kg: 0.3-0.5 mg intramuscular (1:1000 concentration) 1, 3
• Prepubertal children: 0.01 mg/kg intramuscular, maximum 0.3 mg 1, 3
• Injection site: Mid-outer thigh (vastus lateralis muscle)—this provides optimal absorption compared to subcutaneous or arm injection 1, 3
• Autoinjector use: If available, the patient should self-administer or first aid providers should assist if the patient cannot manipulate the device due to respiratory distress, hypotension, or altered mental status 1, 3

The intramuscular thigh route achieves higher peak plasma epinephrine concentrations more rapidly than subcutaneous or arm administration. 1 Injection can be given through clothing, but avoid seams or pockets with objects. 4

Repeat Dosing

Administer a second dose of epinephrine every 5-15 minutes if symptoms persist or recur. 1, 3 Between 7-18% of patients with anaphylaxis require more than one dose of epinephrine. 1, 4 Consider repeat dosing if: 1, 3

• Initial symptoms do not improve within 5-15 minutes
• Severe or rapidly progressive anaphylaxis
• EMS arrival will exceed 5-10 minutes

Patients requiring multiple epinephrine doses have more severe illness but benefit from additional treatment—this reflects disease severity, not medication adverse effects. 1

Patient Positioning

Place the patient supine with lower extremities elevated. 1, 3 This positioning is critical for cardiovascular support. 1

• Exception: If respiratory distress or vomiting is present, position for comfort 1, 3
• Never allow standing, walking, or running—sudden position changes can precipitate cardiovascular collapse and death 1, 3

Adjunctive Treatments (Only AFTER Epinephrine)

These interventions are secondary and should never delay epinephrine: 1, 3

• Supplemental oxygen: For respiratory symptoms or patients receiving multiple epinephrine doses 1, 3
• Intravenous fluids: Large-volume crystalloid resuscitation (normal saline) for hypotension or cardiovascular involvement—administer early with first epinephrine dose 1
• Inhaled beta-2 agonists (albuterol): For persistent bronchospasm after epinephrine 1, 3
• H1 antihistamines: May address cutaneous symptoms only—no role in treating life-threatening manifestations 1, 3
• H2 antihistamines: No high-quality evidence supports efficacy in anaphylaxis 1
• Glucocorticoids: No role in acute treatment due to slow onset; do not prevent biphasic reactions 1

Critical Pitfalls to Avoid

Delayed epinephrine administration is associated with increased mortality, biphasic reactions, and poor outcomes. 1, 3, 5 Common errors include: 1, 3

• Administering antihistamines or corticosteroids before or instead of epinephrine
• Using subcutaneous route or arm injection site
• Waiting to "see if symptoms improve" before giving epinephrine
• Failing to activate EMS while treating

There are no absolute contraindications to epinephrine in anaphylaxis—the risk of death from untreated anaphylaxis far exceeds any theoretical medication concerns. 1, 3

Observation and Transfer

All patients must be transferred to an emergency department, preferably by EMS vehicle, for extended observation. 1, 3

• Minimum observation: 4-6 hours after symptom resolution 3
• Extended observation/admission: For severe anaphylaxis, requirement of multiple epinephrine doses, or history of biphasic reactions 1, 3
• Biphasic anaphylaxis: Occurs in 7-10% of cases, with symptom recurrence up to 72 hours later (mean 11 hours) 1

Risk factors for biphasic reactions include severe initial presentation, requiring >1 dose of epinephrine (odds ratio 4.82), wide pulse pressure, and unknown trigger. 1

Post-Emergency Management

Before discharge from emergency care: 3

• Prescribe two epinephrine autoinjectors with hands-on training in proper use 3
• Provide written anaphylaxis emergency action plan 1, 3
• Refer to allergist for trigger identification and long-term management 3
• Educate on biphasic reaction risk and when to re-administer epinephrine 1, 3

High-Risk Populations

Patients at increased risk for severe or fatal anaphylaxis require heightened vigilance: 1, 3

• Adolescents and young adults
• Coexisting asthma (especially severe or poorly controlled)
• Previous anaphylaxis history
• Peanut/tree nut allergies
• Patients on beta-blockers (may require glucagon for refractory hypotension) 3