What is the recommended emergency treatment for anaphylaxis following vaccination?

Emergency Treatment of Anaphylaxis Following Vaccination

Immediately administer intramuscular epinephrine 0.3-0.5 mg (1:1000 concentration) into the mid-outer thigh for adults and adolescents ≥30 kg, or 0.01 mg/kg (maximum 0.3 mg) for children <30 kg, and repeat every 5-15 minutes as needed—this is the only first-line treatment that prevents death from anaphylaxis. 1, 2

Immediate First-Line Management

Epinephrine Administration

• Inject epinephrine intramuscularly in the anterolateral aspect of the mid-thigh (vastus lateralis muscle) as soon as anaphylaxis is recognized. This route achieves peak plasma concentrations in 8±2 minutes compared to 34±14 minutes with subcutaneous administration. 1, 2, 3

• Dosing for adults and adolescents ≥30 kg: 0.3-0.5 mg of 1:1000 (1 mg/mL) epinephrine intramuscularly 1, 2, 4

• Dosing for children <30 kg: 0.01 mg/kg (0.01 mL/kg of 1:1000 solution), up to a maximum of 0.3 mg 1, 2, 4

• Autoinjector dosing: 0.15 mg for children weighing 10-25 kg; 0.3 mg for individuals ≥25 kg; 0.1 mg for infants where available (if unavailable, 0.15 mg is appropriate for infants >7.5 kg) 2, 1

• Repeat dosing: If symptoms persist or recur, repeat the intramuscular epinephrine dose every 5-15 minutes as needed. Approximately 6-19% of pediatric patients require a second dose. 1, 5

Critical Safety Point

Delayed epinephrine administration is directly associated with anaphylaxis fatalities—inject epinephrine first, before any other intervention. 1, 2, 3

Concurrent Supportive Measures

Patient Positioning

• Place the patient supine with legs elevated (unless there is respiratory distress or vomiting, in which case position for comfort). 1, 2
• Never allow the patient to stand, walk, or run as sudden postural changes can precipitate cardiovascular collapse. 1

Activate Emergency Response

• Call for help immediately: 911/EMS in community settings or activate the resuscitation team in healthcare settings. 1, 5

Establish IV Access and Fluid Resuscitation

• Establish intravenous access immediately and administer aggressive crystalloid resuscitation (normal saline or lactated Ringer's solution). 2, 5
• For Grade II reactions: Initial bolus of 0.5 L of crystalloids 2
• For Grade III reactions: Initial bolus of 1 L of crystalloids 2
• Repeat boluses as needed up to 20-30 mL/kg based on clinical response to combat vasodilation and capillary leak. 2

Supplemental Oxygen

• Provide supplemental oxygen at 6-8 L/min for any patient with respiratory symptoms or who has required multiple epinephrine doses. 2, 5

Adjunctive Medications (Second-Line Only)

These medications should NEVER be administered before or instead of epinephrine—they are adjuncts only and do not prevent death from anaphylaxis. 1, 2

H1 Antihistamines

• Diphenhydramine 25-50 mg IV/IM (or 1-2 mg/kg in children) for relief of urticaria and itching only—does not relieve stridor, bronchospasm, gastrointestinal symptoms, or shock. 1, 2, 5
• Alternative: Cetirizine 10 mg orally (less sedating second-generation H1 antihistamine with relatively rapid onset) 1

H2 Antihistamines

• Ranitidine 50 mg IV in adults (1 mg/kg in children, 12.5-50 mg) over 5 minutes, in combination with H1 antihistamine—minimal evidence supports use but may provide additional symptom relief. 1, 2, 5

Bronchodilators

• For persistent bronchospasm after epinephrine: Nebulized albuterol 2.5-5 mg in 3 mL saline, repeated as necessary. 1, 2, 5
• Important caveat: Albuterol does not relieve airway edema (laryngeal edema) and should never substitute for epinephrine. 1

Corticosteroids

• Corticosteroids are NOT helpful in acute anaphylaxis treatment due to slow onset of action (4-6 hours) and lack of proven benefit in preventing biphasic reactions. 1, 2
• If administered: Methylprednisolone 1-2 mg/kg/day IV every 6 hours, but recognize this is empiric practice without strong evidence. 1, 5

Management of Refractory Anaphylaxis

When to Consider IV Epinephrine

Use IV epinephrine only when: IV access is already established AND the patient has anaphylactic shock unresponsive to multiple IM injections, OR in cardiac arrest. 2, 6

IV Epinephrine Dosing (Extreme Caution Required)

• IV bolus: 50-100 mcg (0.05-0.1 mg) using 1:10,000 concentration, titrated slowly to response rather than rapid bolus 2, 6, 5
• IV infusion: Add 1 mg (1 mL) of 1:1000 epinephrine to 250 mL D5W (concentration 4.0 μg/mL); infuse at 1-4 μg/min initially, increasing to maximum 10 μg/min as needed 6, 5
• Alternative infusion rate: 0.05-0.1 μg/kg/min with mandatory continuous cardiac monitoring 2, 6

Critical warning: IV bolus epinephrine carries significantly higher risk of cardiovascular complications (10% vs 1.3% for IM) and overdose (13.3% vs 0% for IM) compared to intramuscular administration. 7

Alternative Vasopressors

• For persistent hypotension despite epinephrine and fluids: Consider norepinephrine, vasopressin, phenylephrine, or metaraminol. 2

Special Consideration: Beta-Blocker Patients

• Patients on beta-blockers may have refractory hypotension despite epinephrine. Administer glucagon 1-5 mg IV over 5 minutes, followed by infusion at 5-15 μg/min. 6, 5

Observation and Monitoring

Observation Period

• Observe all patients for a minimum of 4-6 hours in a facility capable of managing anaphylaxis, or until stable and symptoms have resolved. 2, 5, 8
• Extended observation (up to 6 hours or more) is required for:
  • Patients who received more than one dose of epinephrine 2, 8
  • Grade III-IV reactions (typically require ICU admission) 2
  • Severe initial presentation, wide pulse pressure, unknown trigger, or drug-triggered reactions in children 2

Biphasic Reaction Risk

• Biphasic anaphylaxis (recurrence after appropriate initial treatment) occurs in up to 20% of patients and can occur within 3 days, though most occur within the observation period. 1, 2

Tryptase Sampling

• Obtain mast cell tryptase samples to confirm diagnosis when clinical presentation is unclear:
  • First sample: 1 hour after reaction onset 2, 5
  • Second sample: 2-4 hours after onset 2, 5
  • Baseline sample: At least 24 hours post-reaction for comparison 2, 5

Discharge Planning

Mandatory Prescriptions

• Prescribe two epinephrine autoinjectors (0.15 mg for 10-25 kg; 0.3 mg for ≥25 kg) with a written anaphylaxis emergency action plan. 2
• Provide clear instructions on when and how to use the autoinjector, emphasizing immediate use at first sign of anaphylaxis. 2

Follow-Up

• Refer to an allergist for trigger identification and ongoing risk assessment. 2, 5, 8
• Educate on avoidance measures and monitoring autoinjector expiration dates. 2

Common Pitfalls to Avoid

• Never use antihistamines or corticosteroids as first-line treatment instead of epinephrine—this is the most common fatal error. 5, 8
• Never delay IM epinephrine while establishing IV access—IM injection achieves therapeutic levels much faster. 2
• Never administer epinephrine subcutaneously or in the deltoid—these routes have delayed and inadequate absorption. 1, 2, 3
• Never inject epinephrine into buttocks, digits, hands, or feet—risk of tissue necrosis and inadequate absorption. 4
• Never discharge patients too early without adequate observation—biphasic reactions can be life-threatening. 5, 8
• There are no absolute contraindications to epinephrine in anaphylaxis, even in elderly patients with cardiovascular disease—the risk of death from anaphylaxis exceeds any risk from epinephrine. 1, 2