What are the symptoms and treatment of anaphylaxis?

Symptoms and Treatment of Anaphylaxis

Anaphylaxis is an acute, life-threatening systemic reaction with varied mechanisms, clinical presentations, and severity that results from the sudden systemic release of mediators from mast cells and basophils, requiring immediate recognition and treatment with epinephrine as the first-line therapy. 1

Clinical Presentation of Anaphylaxis

Common Symptoms

• Cutaneous manifestations (most common, 80-90% of cases)

  • Urticaria and angioedema
  • Flushing
  • Pruritus
  • Swelling of eyelids, lips, and tongue 1, 2

• Respiratory symptoms (up to 70% of cases)

  • Dyspnea
  • Wheezing
  • Bronchospasm
  • Stridor
  • Laryngospasm
  • Upper airway swelling 1, 2, 3

• Cardiovascular symptoms

  • Hypotension
  • Tachycardia
  • Syncope
  • Chest pain
  • Cardiac arrhythmias 1, 2, 3

• Gastrointestinal symptoms (up to 40% of cases)

  • Nausea
  • Vomiting
  • Diarrhea
  • Abdominal cramps 1, 2

• Other symptoms

  • Lightheadedness
  • Headache
  • Feeling of impending doom
  • Unconsciousness
  • Uterine cramps
  • Involuntary voiding 1, 2

Important Clinical Considerations

• The more rapidly anaphylaxis develops, the more likely it is to be severe and potentially life-threatening 1, 2
• Cutaneous findings may be delayed or absent in rapidly progressive anaphylaxis 1, 2
• Death from anaphylaxis can occur within 30 minutes to 2 hours of exposure 2

Diagnostic Criteria

Anaphylaxis is diagnosed when any ONE of the following criteria is met:

1. Acute onset of illness with involvement of skin/mucosal tissue PLUS at least one of:

   • Respiratory compromise
   • 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

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 2

Differential Diagnosis

• Vasodepressor (vasovagal) reactions

  • Urticaria absent
  • Heart rate typically bradycardic (vs. tachycardia in anaphylaxis)
  • Bronchospasm generally absent
  • Blood pressure usually normal or increased
  • Skin typically cool and pale 1

• Other conditions to consider:

  • Acute anxiety/panic attack
  • Myocardial dysfunction
  • Pulmonary embolism
  • Systemic mast cell disorders
  • Foreign-body aspiration
  • Acute poisoning
  • Hypoglycemia
  • Seizure disorder 1, 2

Emergency Management Algorithm

Immediate Actions

1. Administer epinephrine immediately (first-line treatment)

   • Aqueous epinephrine 1:1000 dilution (1 mg/mL)
   • 0.2 to 0.5 mL (0.01 mg/kg in children, maximum 0.3 mg) intramuscularly into the vastus lateralis (anterolateral thigh)
   • Repeat every 5-15 minutes as necessary if symptoms persist 1, 2, 3

2. Position the patient appropriately

   • Supine with legs elevated for hypotension
   • Sitting for respiratory distress 2

3. Assess airway, breathing, circulation, and level of consciousness 1

4. Administer oxygen if available 1, 2

5. Establish IV access for fluid resuscitation

   • Crystalloids initially
   • Colloid volume substitutes for severe shock 1, 2

Secondary Interventions

1. Antihistamines (as adjunctive therapy)

   • H1-antihistamines for mild reactions
   • Consider combined H1 and H2 antagonists 1, 2

2. Corticosteroids

   • To prevent protracted or biphasic reactions
   • Limited value in acute treatment 1, 2

3. Inhaled beta-2 agonists

   • For bronchial symptoms or laryngeal edema 1, 2

Monitoring and Follow-up

1. Monitor vital signs continuously 2

2. Observe for biphasic reactions

   • Typically occur 8-12 hours after initial symptoms resolve
   • Extended observation (4-12 hours) based on severity and risk factors 1, 2

Post-Emergency Care

1. Prescribe epinephrine auto-injector 2, 4

2. Provide patient education

   • Recognition of symptoms
   • Proper use of epinephrine auto-injector
   • Anaphylaxis action plan 2

3. Recommend medical identification (e.g., Medic Alert jewelry) 1, 2

4. Refer to allergist-immunologist for comprehensive evaluation 1, 2

Common Pitfalls to Avoid

1. Delaying epinephrine administration

   • Associated with increased morbidity and mortality 2

2. Relying solely on antihistamines

   • Inadequate for treating anaphylaxis 2, 4

3. Discharging patients too early

   • Without adequate observation for biphasic reactions 2

4. Failing to recognize anaphylaxis without skin symptoms

   • Cutaneous findings may be absent in rapidly progressive cases 1, 2

5. Confusing anaphylaxis with vasovagal reactions

   • Check for bradycardia (vasovagal) vs. tachycardia (anaphylaxis) 1

Anaphylaxis requires immediate recognition and prompt treatment. The cornerstone of management is early administration of epinephrine, which should never be delayed for secondary interventions. All patients who have experienced anaphylaxis should be equipped with an epinephrine auto-injector and educated about its use.