What are the symptoms and treatment of an anaphylactic reaction?

Symptoms and Treatment of Anaphylactic Reaction

Anaphylaxis is a life-threatening, systemic allergic reaction characterized by multi-organ involvement including skin/mucosal tissue, respiratory system, cardiovascular system, and gastrointestinal system, requiring immediate treatment with epinephrine. 1

Diagnostic Criteria for Anaphylaxis

Anaphylaxis is highly likely when ANY ONE of these three criteria is met 1:

1. Acute onset (minutes to hours) involving skin/mucosal tissue (hives, itching, flushing, swollen lips/tongue/uvula) PLUS at least one of:

   • Respiratory compromise (dyspnea, wheezing, stridor, hypoxemia)
   • Reduced blood pressure or symptoms of end-organ dysfunction

2. Two or more systems rapidly affected after allergen exposure:

   • Skin/mucosal involvement
   • Respiratory compromise
   • Reduced blood pressure/end-organ symptoms
   • Persistent gastrointestinal symptoms

3. Reduced blood pressure after exposure to known allergen:

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

Signs and Symptoms by System

Cutaneous (occur in majority of cases)

• Flushing
• Pruritus (itching)
• Urticaria (hives)
• Angioedema (swelling)
• Important: 10-20% of anaphylaxis cases have NO skin manifestations 1

Respiratory (occur in up to 70% of cases)

• Upper airway: nasal congestion, rhinorrhea, throat pruritus, laryngeal edema, stridor, choking
• Lower airway: wheezing, cough, dyspnea, bronchospasm
• Hypoxemia

Cardiovascular (occur in up to 35% of cases)

• Dizziness
• Tachycardia
• Hypotension
• Hypotonia
• Syncope
• Cardiac arrhythmias

Gastrointestinal (occur in up to 40% of cases)

• Cramping abdominal pain
• Nausea
• Vomiting
• Diarrhea

Other symptoms

• Anxiety
• Mental confusion
• Feeling of impending doom
• Lethargy
• Seizures
• Unconsciousness
• Urinary/fecal incontinence 1

Time Course of Anaphylaxis

• Rapid onset: Usually within minutes of exposure to allergen
• Progression: Can evolve rapidly over minutes to several hours
• Fatal reactions: Can occur within 30 minutes to 2 hours of exposure 1

Reactions can follow three patterns:

1. Uniphasic: Single episode that resolves with treatment
2. Biphasic: Recurrence of symptoms 8-12 hours after initial resolution (occurs in 1-20% of cases)
3. Protracted: Persistent symptoms lasting hours to days 1

Treatment of Anaphylaxis

Immediate Interventions (First Priority)

1. Administer epinephrine immediately 1, 2

   • Dose: 0.01 mg/kg up to 0.5 mg in adults
   • Route: Intramuscular injection in the anterolateral thigh
   • Frequency: Can repeat every 5 minutes as needed
   • If self-administered autoinjector is available, the person should use it immediately 1

2. Activate emergency response system 1

3. Position patient appropriately

   • Supine position with legs elevated (unless respiratory distress)
   • Sitting position if respiratory distress

4. Assess and maintain airway, breathing, circulation

   • Provide supplemental oxygen if available
   • Establish IV access for fluid resuscitation if hypotensive

Secondary Interventions (After Epinephrine)

1. IV fluids for hypotension

   • Rapid infusion of normal saline

2. Adjunctive medications (should not delay epinephrine)

   • H1 antihistamines (e.g., diphenhydramine) 3
   • H2 antihistamines
   • Corticosteroids
   • Bronchodilators (for persistent bronchospasm)

3. Consider repeat dose of epinephrine

   • If no response to initial dose
   • If symptoms recur
   • Particularly if EMS arrival will exceed 5-10 minutes 1

Observation Period

All patients who receive epinephrine should be observed in a medical facility for at least 4-6 hours due to risk of biphasic reactions 1, 4.

Risk Factors for Severe Anaphylaxis

• Previous history of anaphylaxis
• Coexisting asthma
• Cardiovascular disease
• Mast cell disorders
• Delayed administration of epinephrine
• Peanut and tree nut allergies 5

Common Pitfalls in Anaphylaxis Management

1. Delayed epinephrine administration - This is the most common and dangerous error
2. Misdiagnosis - Confusing anaphylaxis with other conditions like vasovagal reaction, panic attack, or asthma
3. Inadequate observation - Discharging patients too early without monitoring for biphasic reactions
4. Improper epinephrine administration - Using wrong dose or route
5. Relying solely on antihistamines - These do not treat cardiovascular or respiratory symptoms effectively

Remember that anaphylaxis is a true medical emergency where rapid recognition and treatment with epinephrine can be life-saving. The severity of reactions can progress rapidly, and early intervention is critical to prevent mortality.