What are the diagnostic criteria and treatment for anaphylaxis according to the World Allergy Organization?

Diagnostic Criteria and Treatment for Anaphylaxis According to World Allergy Organization

Anaphylaxis must be diagnosed using established criteria and treated immediately with epinephrine as the first-line therapy to reduce mortality and morbidity.

Diagnostic Criteria

Anaphylaxis is diagnosed when any ONE of the following three criteria is fulfilled 1, 2:

1. Acute onset of illness (minutes to hours) with involvement of skin/mucosal tissue (e.g., generalized hives, itching, flushing, swollen lips/tongue/uvula) AND at least one of the following:

   • Respiratory compromise (e.g., dyspnea, wheeze, stridor, hypoxemia)
   • Reduced blood pressure or symptoms of end-organ dysfunction

2. Two or more of the following occurring rapidly after exposure to a likely allergen:

   • Skin/mucosal involvement
   • Respiratory compromise
   • Reduced blood pressure or associated symptoms
   • Persistent gastrointestinal symptoms (e.g., crampy abdominal pain, vomiting)

3. Reduced blood pressure after exposure to a known allergen:

   • Adults: Systolic BP <90 mmHg or >30% decrease from baseline
   • Children: Age-specific low systolic BP or >30% decrease from baseline

Clinical Presentation

• Cutaneous symptoms (urticaria, angioedema) are the most common manifestations but may be delayed or absent in rapidly progressive anaphylaxis 1
• The more rapidly anaphylaxis develops, the more likely it is to be severe and potentially life-threatening 1
• Symptoms may include 1, 3:
  • Skin: Flushing, pruritus, urticaria, angioedema
  • Respiratory: Dyspnea, wheeze, stridor, cough, hypoxemia
  • Cardiovascular: Hypotension, tachycardia, syncope
  • Gastrointestinal: Nausea, vomiting, diarrhea, abdominal cramps
  • Other: Lightheadedness, headache, feeling of impending doom, unconsciousness

Differential Diagnosis

Conditions that may mimic anaphylaxis include 1, 4:

• Vasodepressor (vasovagal) reactions - characterized by bradycardia, normal or increased blood pressure, cool/pale skin, absence of urticaria
• Panic attacks
• Acute anxiety/hyperventilation syndrome
• Myocardial dysfunction
• Pulmonary embolism
• Systemic mast cell disorders
• Foreign body aspiration
• Acute poisoning
• Hypoglycemia
• Seizure disorders

Treatment Algorithm

Immediate Management:

1. Administer epinephrine immediately as first-line treatment 1, 3

   • Intramuscular injection into anterolateral thigh
   • Adult dose: 0.3-0.5 mg (1:1000 solution)
   • Pediatric dose: 0.01 mg/kg up to 0.3 mg
   • May repeat every 5-15 minutes if symptoms persist

2. Place patient in appropriate position

   • Supine position with legs elevated for hypotension
   • Sitting position if respiratory distress

3. Administer oxygen if available 1

4. Establish IV access for fluid resuscitation 1, 5

   • Rapid infusion of crystalloids (1-2 L for adults)
   • For children: 20 mL/kg bolus

5. Secondary medications (should not delay epinephrine) 1

   • H1-antihistamines for urticaria/pruritus
   • H2-antihistamines as adjunctive therapy
   • Corticosteroids to prevent biphasic or protracted reactions
   • Inhaled beta-2 agonists for bronchospasm

6. Monitor vital signs continuously 1

Post-Acute Care:

1. Observation period of 4-10 hours depending on severity 5

2. Patient education 1, 2

   • Allergen avoidance
   • Recognition of symptoms
   • Proper use of epinephrine auto-injector
   • Anaphylaxis action plan

3. Referral to allergist-immunologist for comprehensive evaluation 1

4. Prescription for epinephrine auto-injector 1, 6

5. Medical identification (e.g., Medic Alert jewelry) 1

Special Considerations

• Risk factors for severe reactions 7:

  • Uncontrolled asthma
  • Cardiovascular disease
  • Beta-blocker or ACE inhibitor use
  • Previous severe reactions
  • Delayed epinephrine administration

• Biphasic reactions may occur 8-12 hours after initial symptoms resolve 1

• Laboratory tests (e.g., serum tryptase) have poor sensitivity in confirming anaphylaxis in the acute setting 2

• Medical facilities should have established protocols and appropriate equipment to manage anaphylaxis 1

Common Pitfalls to Avoid

1. Delaying epinephrine administration - associated with increased morbidity and mortality 1, 6

2. Relying solely on antihistamines - inadequate for treating anaphylaxis 2

3. Failure to recognize anaphylaxis without skin symptoms - cutaneous findings may be absent in up to 20% of cases 2

4. Discharging patients too early - observation is necessary until symptoms fully resolve 1

5. Inadequate follow-up - all patients should be referred to an allergist 1