What is the initial management for a patient experiencing anaphylaxis?

Initial Management of Anaphylaxis

Administer intramuscular epinephrine immediately at the first sign of anaphylaxis—this is the single most critical intervention that saves lives, and there is no absolute contraindication to its use in this setting. 1

Immediate First Steps (ABC Approach)

Epinephrine administration should never be delayed while considering other diagnoses or waiting for symptoms to worsen. 1

Primary Interventions (Simultaneous if team available):

• Position the patient supine with legs elevated to counteract hypotension (up to 50% of intravascular fluid can shift to extravascular space within 10 minutes). 1, 2

• Administer epinephrine intramuscularly into the lateral thigh immediately:

  • Adults: 0.3-0.5 mg (0.3-0.5 mL of 1:1000 solution) 1
  • Children ≥25 kg: 0.3 mg 3
  • Children 10-25 kg: 0.15 mg 3
  • In anesthetized patients: 50 mcg IV (0.5 mL of 1:10,000 solution) initially, with repeat doses as needed 1

• Call for emergency medical services immediately and note the time. 1

• Remove the triggering agent if identifiable (stop IV medications, remove latex, discontinue colloids). 1

• Establish airway and administer 100% oxygen. Intubate if necessary for airway compromise. 1

Secondary Interventions (After Epinephrine)

Fluid Resuscitation:

• Administer normal saline or lactated Ringer's solution rapidly via large-bore IV (large volumes often required due to massive fluid shifts). 1

Repeat Epinephrine Dosing:

• Repeat epinephrine every 5-10 minutes if inadequate response to initial dose. 1
• Consider continuous IV epinephrine infusion if multiple doses are required (epinephrine has a short half-life). 1
• Between 7-18% of patients require more than one dose of epinephrine. 1

Adjunctive Medications (Only AFTER epinephrine):

These are secondary interventions that should never delay epinephrine administration: 1, 4

• H1 antihistamine: Chlorphenamine 10 mg IV (adults) for urticaria and itching relief only. 1
• Corticosteroids: Hydrocortisone 200 mg IV (adults)—onset of action is 4-6 hours, so no immediate effect on acute anaphylaxis. 1, 4
• H2 antihistamine: May be added as adjunct. 5, 6
• Beta-2 agonists: For persistent bronchospasm (salbutamol infusion or inhaled if appropriate). 1

Refractory Hypotension:

• Consider alternative vasopressors (metaraminol) if hypotension persists despite epinephrine infusion. 1
• Glucagon may be needed for patients on beta-blockers who are refractory to epinephrine. 6

Critical Monitoring and Observation

• Observe for minimum 4-6 hours after symptom resolution for most cases. 5, 6, 2
• Extend observation or admit patients with severe reactions, cardiovascular comorbidity, those requiring multiple epinephrine doses, or those with poor self-management capability. 5
• Biphasic reactions occur in up to 20% of cases (8-12 hours after initial reaction, sometimes up to 72 hours), particularly with severe initial presentation, wide pulse pressure, unknown trigger, or drug triggers in children. 1, 5

Diagnostic Testing During Acute Phase

• Obtain serum tryptase levels if diagnosis is uncertain:
  • Initial sample as soon as feasible after resuscitation starts (do not delay treatment)
  • Second sample at 1-2 hours after symptom onset
  • Third sample at 24 hours or in convalescence for baseline comparison 1, 3, 6

Common Pitfalls to Avoid

• Never substitute antihistamines or corticosteroids for epinephrine—these are adjuncts only and do not prevent progression or biphasic reactions. 5, 4
• Do not delay epinephrine while considering differential diagnoses (vasovagal reaction, anxiety, asthma)—when in doubt, give epinephrine. 1
• Do not administer epinephrine subcutaneously—intramuscular lateral thigh injection provides faster, more reliable absorption. 1, 2
• Beware of bradycardia in 10% of anaphylaxis cases—tachycardia is typical but not universal, especially in patients on beta-blockers or with vagal reflexes. 1
• Remember that cutaneous signs may be absent in up to 20% of cases, particularly in rapidly progressive anaphylaxis with cardiovascular collapse. 1, 2

Mandatory Discharge Requirements

Before discharge from any healthcare facility:

• Prescribe TWO epinephrine autoinjectors with proper dosing and training on technique. 5, 3
• Provide written anaphylaxis emergency action plan detailing symptom recognition and step-by-step treatment. 5, 3
• Mandatory referral to allergist-immunologist for comprehensive trigger identification and long-term management. 5, 3
• Consider continuing adjunctive medications (H1/H2 antihistamines, corticosteroids) for 2-3 days post-discharge, though these do not reliably prevent biphasic reactions. 5