What is the appropriate management and treatment for a patient experiencing anaphylaxis?

Anaphylaxis Management

Inject intramuscular epinephrine 0.01 mg/kg (maximum 0.3 mg in prepubertal children, 0.5 mg in adults) into the mid-outer thigh immediately upon recognizing anaphylaxis—this is the only first-line treatment and delays in administration are directly associated with fatality. 1, 2, 3

Immediate Recognition and First Actions

Recognize anaphylaxis by sudden onset (minutes to hours) after allergen exposure with involvement of skin/mucosa (itching, hives, swelling) PLUS either respiratory compromise (throat tightness, stridor, wheeze, difficulty breathing) OR cardiovascular symptoms (hypotension, tachycardia, dizziness, collapse), or persistent gastrointestinal symptoms (vomiting, crampy abdominal pain). 1, 4

Call emergency services (911/EMS) immediately while preparing epinephrine. 2

Epinephrine Administration: The Critical First Step

Dosing and Route

• Administer epinephrine 1:1000 concentration (1 mg/mL) intramuscularly into the anterolateral thigh (vastus lateralis muscle) at 0.01 mg/kg, maximum 0.3 mg in prepubertal children and 0.5 mg in adults. 1, 2
• For autoinjectors: use 0.15 mg for children 10-25 kg, 0.3 mg for patients ≥25 kg. 2, 5
• The thigh is superior to deltoid or subcutaneous routes because it achieves higher and faster peak plasma levels (8±2 minutes vs 34±14 minutes subcutaneously). 5

Repeat Dosing

• Repeat epinephrine every 5-15 minutes if symptoms persist or progress—there are no absolute contraindications to epinephrine in anaphylaxis. 1, 2
• Approximately 6-19% of pediatric patients require a second dose; a third dose is rarely needed. 1

Common pitfall: Delaying epinephrine while administering antihistamines or bronchodilators is a major contributor to anaphylaxis fatalities. Epinephrine must come first. 2, 4, 3

Positioning and Supportive Care

• Position patient supine with legs elevated to prevent orthostatic hypotension and improve venous return to vital organs. 1, 2, 5
• If respiratory distress or vomiting is present, allow position of comfort but avoid standing, walking, or sitting upright. 1, 2
• Establish intravenous access and administer supplemental oxygen at 6-8 L/min. 1, 2

Fluid Resuscitation

Administer normal saline aggressively for volume replacement: 1-2 L in adults at 5-10 mL/kg in the first 5 minutes; up to 30 mL/kg in the first hour for children. 1, 2

• Anaphylaxis causes massive capillary leak that can transfer 50% of intravascular fluid to extravascular space within 10 minutes, potentially requiring up to 7 L of crystalloid. 2
• For Grade II reactions, start with 0.5 L bolus; for Grade III reactions, start with 1 L bolus, repeating as needed up to 20-30 mL/kg based on clinical response. 5

Second-Line Adjunctive Therapies (NEVER Before Epinephrine)

Antihistamines

• Administer H1-antihistamine diphenhydramine 1-2 mg/kg (maximum 25-50 mg) IV or IM ONLY after epinephrine. 2, 5
• Consider adding H2-antihistamine ranitidine 50 mg IV in adults (1 mg/kg in children) diluted in 5% dextrose over 5 minutes. 2
• Antihistamines treat only cutaneous symptoms and do NOT prevent or reverse cardiovascular collapse or airway obstruction. 5, 4

Bronchodilators

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

Corticosteroids

• Consider methylprednisolone 1-2 mg/kg IV every 6 hours or equivalent for patients with history of idiopathic anaphylaxis, asthma, or severe/prolonged anaphylaxis. 1, 2
• Corticosteroids are NOT helpful acutely but may prevent biphasic or protracted reactions occurring hours later. 1, 2

Management of Refractory Anaphylaxis

Escalating Epinephrine

• If inadequate response after 2-3 IM doses (10 minutes), consider epinephrine infusion at 0.05-0.1 μg/kg/min (1-4 μg/min in adults, maximum 10 μg/min). 2, 5
• Prepare by adding 1 mg (1 mL) of 1:1000 epinephrine to 250 mL D5W (concentration 4.0 μg/mL). 5

Alternative 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. 1, 2

Special Consideration: Beta-Blocker Patients

• Patients on beta-blockers may be resistant to epinephrine and require glucagon 1-2 mg IV to overcome beta-blockade. 5

Cardiopulmonary Arrest During Anaphylaxis

• Initiate CPR and ACLS immediately with high-dose IV epinephrine: 1-3 mg (1:10,000 dilution) over 3 minutes, then 3-5 mg over 3 minutes, followed by 4-10 μg/min infusion. 1, 2
• For children: 0.01 mg/kg (0.1 mL/kg of 1:10,000 solution) repeated every 3-5 minutes; consider higher doses (0.1-0.2 mg/kg of 1:1,000 solution) for unresponsive arrest. 1
• Prolonged resuscitation is encouraged in anaphylaxis as efforts are more likely to be successful than in other causes of cardiac arrest. 1

Observation and Monitoring

Observe all patients for minimum 6 hours in a monitored setting—there are no reliable predictors of biphasic reactions, which occur in up to 20% of cases. 1, 2, 5

• Patients with Grade III-IV reactions typically require ICU admission. 5
• High-risk patients (severe initial presentation, required >1 epinephrine dose) may require extended observation beyond 6 hours. 5

Common pitfall: Discharging patients too early after symptom resolution. Biphasic reactions can occur hours after apparent recovery without re-exposure to allergen. 2, 5

Discharge Requirements

Mandatory Prescriptions

• Provide TWO epinephrine autoinjectors (0.15 mg for 10-25 kg; 0.3 mg for ≥25 kg) with comprehensive training on self-administration. 2, 5, 4
• Include written, personalized anaphylaxis emergency action plan listing triggers, symptoms, and clear instructions. 5, 4

Follow-Up

• Refer ALL patients to allergist-immunologist for diagnostic evaluation, trigger identification, and long-term management including consideration of allergen immunotherapy (e.g., venom immunotherapy). 1, 2, 5

Tryptase Sampling (If Available)

• First sample at 1 hour after reaction onset, second at 2-4 hours, baseline sample at least 24 hours post-reaction for comparison. 5

Critical Safety Points

• There are no absolute contraindications to epinephrine in anaphylaxis, even in elderly patients with cardiac disease, complex congenital heart disease, or pulmonary hypertension. 5
• Never delay epinephrine to establish IV access—IM injection is faster and safer in the acute setting. 5
• Several anaphylaxis fatalities have been attributed to injudicious use of IV epinephrine; reserve IV route for refractory cases with continuous cardiac monitoring. 1, 5
• Fatal anaphylaxis is associated with adolescence, concomitant asthma (especially poorly controlled), and failure to inject epinephrine promptly. 1