What is the initial management of anaphylactic shock in adults and children?

Anaphylactic Shock Management

Immediately administer intramuscular epinephrine 0.3-0.5 mg (adults) or 0.01 mg/kg up to 0.3 mg (children) into the anterolateral thigh—this is the first-line, life-saving treatment that must never be delayed. 1

Immediate First-Line Treatment: Epinephrine

Intramuscular epinephrine is the cornerstone of anaphylaxis management and should be given immediately upon recognition. 1, 2

Dosing and Route

• Adults and children ≥30 kg: 0.3-0.5 mg (0.3-0.5 mL of 1:1000 solution) IM 3
• Children <30 kg: 0.01 mg/kg (maximum 0.3 mg) IM 3
• Autoinjector dosing: 0.15 mg for children 10-25 kg; 0.3 mg for individuals ≥25 kg 2, 4
• Injection site: Anterolateral thigh (vastus lateralis muscle) at 90-degree angle—this achieves peak plasma levels in 8±2 minutes vs. 34±14 minutes subcutaneously 1, 2, 4
• Repeat dosing: Every 5-15 minutes as needed if symptoms persist or recur 1, 2, 3

Critical Pitfall to Avoid

Never delay epinephrine to establish IV access, give antihistamines, or perform other interventions—delayed epinephrine administration is directly associated with anaphylaxis fatalities. 2, 5, 6

Concurrent Supportive Measures

Positioning and Oxygen

• Position patient supine with legs elevated (unless respiratory distress present) 2
• Pregnant patients: Left uterine displacement to avoid aortocaval compression 2
• Administer supplemental oxygen 2

Fluid Resuscitation

• Establish IV access immediately 2
• Grade II reactions: 0.5 L crystalloid bolus initially 2
• Grade III reactions: 1 L crystalloid bolus initially 2
• Repeat boluses up to 20-30 mL/kg based on clinical response—this combats vasodilation and capillary leak 2

Refractory Anaphylaxis Management

For patients requiring >3 IM epinephrine doses or with persistent shock, escalate to IV epinephrine infusion. 1, 2

IV Epinephrine Protocol

• Preparation: 1 mg (1 mL of 1:1000) in 250 mL D5W = 4 μg/mL concentration 2, 4
• Infusion rate: Start at 0.05-0.1 μg/kg/min (or 1-4 μg/min in adults), titrate up to maximum 10 μg/min 2, 4
• IV bolus alternative (if IV already in place): 0.05-0.1 mg (50-100 μg) of 1:10,000 concentration, titrated slowly 1
• Requires continuous cardiac monitoring for arrhythmias and hypertension 2

Alternative Vasopressors

If hypotension persists despite epinephrine, consider norepinephrine, vasopressin, phenylephrine, or metaraminol. 2

Airway Management

Immediately refer to a provider with advanced airway expertise when oropharyngeal or laryngeal edema develops—emergency cricothyroidotomy or tracheostomy may be required. 1

Second-Line Adjunctive Therapies

These should NEVER be given before or instead of epinephrine—they are adjuncts only. 2, 7

Antihistamines (After Epinephrine)

• H1 antihistamine: Diphenhydramine 25-50 mg IV or chlorphenamine 2
• H2 antihistamine: Ranitidine 50 mg IV (adults) 2
• These treat only cutaneous symptoms and do NOT prevent cardiovascular collapse or airway obstruction 2

Corticosteroids

• Methylprednisolone 1-2 mg/kg/day IV every 6 hours may prevent biphasic reactions but does not help acute treatment 2

Special Populations

Patients on Beta-Blockers

May require glucagon 1-2 mg IV for refractory hypotension due to blunted response to epinephrine 2

No Absolute Contraindications

There are no absolute contraindications to epinephrine in anaphylaxis, even in elderly patients with cardiac disease, complex congenital heart disease, or pulmonary hypertension. 2, 4

Monitoring and Observation

• Minimum 6 hours observation in monitored area or until stable and symptoms resolved 2
• Grade III-IV reactions typically require ICU admission 2
• Cardiovascular and respiratory status can change rapidly—close monitoring is imperative 1

Tryptase Sampling

• First sample: 1 hour after reaction onset 2
• Second sample: 2-4 hours after onset 2
• Baseline sample: ≥24 hours post-reaction for comparison 2

Discharge Requirements

All patients must be discharged with:

• Two epinephrine autoinjectors (0.15 mg for 10-25 kg; 0.3 mg for ≥25 kg) 2
• Written, personalized anaphylaxis emergency action plan with triggers, symptoms, and clear instructions 2
• Referral to allergist for trigger identification and ongoing risk assessment 2
• Education on autoinjector use and expiration date monitoring 2

Critical Safety Point

Patients and caregivers must understand to inject epinephrine FIRST at earliest sign of anaphylaxis and always seek emergency care afterward, even if symptoms improve, due to risk of biphasic reactions. 2