What is the management of anaphylaxis?

Management of Anaphylaxis

Immediately administer intramuscular epinephrine 0.01 mg/kg (maximum 0.3 mg in prepubertal children, 0.5 mg in adults) into the mid-outer thigh as soon as anaphylaxis is recognized—this is the only first-line treatment and delays in administration are associated with fatality. 1, 2

Immediate First-Line Treatment

Epinephrine is the cornerstone of anaphylaxis management and must never be delayed or substituted with antihistamines or bronchodilators. 1, 3

Epinephrine Administration

• Administer intramuscular epinephrine 0.01 mg/kg using 1:1000 concentration in the anterolateral thigh (maximum 0.3 mg in prepubertal children, 0.5 mg in adults) 4, 1, 2
• For children, use epinephrine auto-injector 0.15 mg if weight is 10-25 kg or 0.3 mg if ≥25 kg 1
• The intramuscular route in the lateral thigh is superior to other routes because it provides rapid absorption and higher epinephrine levels 5
• Repeat epinephrine every 5-15 minutes if symptoms persist or progress—there are no absolute contraindications to epinephrine in anaphylaxis 4, 1, 2

Immediate Supportive Measures

• Call emergency services (911/EMS) immediately 1
• Position patient supine with elevated lower extremities to prevent orthostatic hypotension and improve circulation to vital organs 4, 1
• If respiratory distress or vomiting is present, position patient for comfort 1
• Establish intravenous access and administer oxygen 6, 2

Subsequent Emergency Care (After Epinephrine)

Fluid Resuscitation

• Administer normal saline rapidly for volume replacement: 1-2 L in adults at 5-10 mL/kg in first 5 minutes; up to 30 mL/kg in first hour for children 4
• For graded responses: 500 mL for Grade II reactions, 1 L for Grade III reactions, escalating to 20-30 mL/kg for refractory cases 6, 2
• Up to 7 L of crystalloid may be necessary due to increased vascular permeability that can transfer 50% of intravascular fluid to extravascular space within 10 minutes 4

Airway Management

• Maintain airway patency—consider endotracheal intubation or cricothyroidotomy if laryngeal edema is severe and clinicians are adequately trained 4
• Administer supplemental oxygen, especially for prolonged reactions, pre-existing hypoxemia, or patients requiring multiple epinephrine doses 4

Second-Line Adjunctive Therapies (Never as Monotherapy)

Antihistamines

• Administer H1-antihistamine diphenhydramine 1-2 mg/kg or 25-50 mg parenterally only after epinephrine 4, 6, 2
• Consider H2-antihistamine ranitidine 50 mg IV in adults (1 mg/kg in children) diluted in 5% dextrose over 5 minutes 4, 6, 2
• The combination of H1 and H2 antihistamines is superior to H1 alone, but both have much slower onset than epinephrine 4

Bronchodilators

• For bronchospasm resistant to adequate epinephrine doses: administer nebulized albuterol 2.5-5 mg in 3 mL saline, repeat as necessary 4, 2

Corticosteroids

• Consider systemic corticosteroids for patients with history of idiopathic anaphylaxis, asthma, or severe/prolonged anaphylaxis 4, 6
• Administer IV methylprednisolone equivalent 1.0-2.0 mg/kg/day every 6 hours, or oral prednisone 0.5 mg/kg for less critical episodes 4
• Corticosteroids are not helpful acutely but may prevent biphasic or protracted reactions 4, 2

Management of Refractory Anaphylaxis

Escalating Epinephrine

• If inadequate response after 10 minutes, double the epinephrine bolus dose 6
• Consider epinephrine infusion (0.05-0.1 μg/kg/min) when more than three boluses have been administered 6, 2
• Prepare infusion by adding 1 mg (1 mL) of 1:1000 epinephrine to 250 mL D5W (concentration 4.0 μg/mL), infuse at 1-4 μg/min, increasing to maximum 10 μg/min 4

Additional Vasopressors

• For hypotension refractory to epinephrine and fluids: add norepinephrine infusion (0.05-0.5 μg/kg/min) or dopamine 2-20 μg/kg/min titrated to maintain systolic BP >90 mmHg 4, 6, 2
• Consider vasopressin 1-2 IU bolus with or without infusion (2 units/h) for persistent hypotension 6

Special Considerations

• For patients on beta-blockers with refractory symptoms: administer IV glucagon 1-5 mg (20-30 μg/kg in children, maximum 1 mg) over 5 minutes, followed by infusion 5-15 μg/min 4, 6
• Glucagon bypasses beta-receptor blockade and has positive inotropic and chronotropic effects 4

Cardiopulmonary Arrest During Anaphylaxis

• Initiate CPR and advanced cardiac life support immediately 4, 2
• Administer high-dose IV epinephrine rapidly: 1-3 mg (1:10,000 dilution) over 3 minutes, then 3-5 mg over 3 minutes, followed by 4-10 μg/min infusion 4
• For children: 0.01 mg/kg (0.1 mL/kg of 1:10,000 solution, maximum 0.3 mg) every 3-5 minutes 4
• Consider higher doses (0.1-0.2 mg/kg of 1:1000 solution) for unresponsive asystole or pulseless electrical activity 4
• Administer atropine and consider transcutaneous pacing for asystole/pulseless electrical activity 4
• Prolonged resuscitation efforts are encouraged—outcomes are better in anaphylaxis than other causes of arrest because patients are typically young with healthy cardiovascular systems 4

Critical Pitfalls to Avoid

• Never delay epinephrine administration—delayed injection is the primary factor associated with fatality 1, 3
• Never substitute antihistamines, corticosteroids, or bronchodilators for epinephrine—these are adjunctive only 1, 6, 2
• Never administer IV epinephrine in non-arrest situations without continuous hemodynamic monitoring due to risk of lethal arrhythmias 4
• IV epinephrine should only be used during cardiac arrest or in profoundly hypotensive patients who fail to respond to IM epinephrine and volume replacement 4, 2

Observation and Monitoring

• Observe all patients for minimum 6 hours in a monitored setting, as there are no reliable predictors of biphasic reactions 4, 1, 6
• Biphasic reactions (recurrence without re-exposure) can occur in up to 20% of cases 1
• Obtain serum tryptase levels if diagnosis is unclear: first sample at 1 hour, second at 2-4 hours, baseline at least 24 hours post-reaction 6

Post-Event Management

• Provide patient with two epinephrine auto-injectors and comprehensive training on self-administration 4, 1
• Provide written anaphylaxis emergency action plan detailing symptom recognition and treatment steps 1
• Refer all patients to an allergist-immunologist for diagnostic evaluation, identification of triggers, and long-term management 4, 1
• Consider medical identification jewelry 1