What is the initial management of a patient presenting with hives in the emergency department (ED)?

Initial Management of Hives in the Emergency Department

The initial management of hives (urticaria) in the emergency department should focus on prompt administration of antihistamines, assessment for anaphylaxis, and identification of potential triggers, with epinephrine reserved for cases with signs of anaphylaxis or angioedema with respiratory involvement. 1

Immediate Assessment and Treatment Algorithm

Step 1: Assess Severity and Airway Status

• Evaluate for signs of anaphylaxis:
  • Respiratory distress (stridor, wheezing, shortness of breath)
  • Hypotension or signs of shock
  • Involvement of multiple organ systems
  • Presence of angioedema affecting the airway

Step 2: Initial Management Based on Severity

For Isolated Urticaria Without Systemic Symptoms:

• First-line treatment: High-dose non-sedating H1 antihistamines 2
  • Examples: cetirizine 10-20mg, loratadine 10mg, or fexofenadine 180mg
• Consider adding H2 antihistamines for enhanced effect
  • Example: ranitidine 150mg or famotidine 20mg

For Urticaria with Angioedema or Signs of Anaphylaxis:

• Administer epinephrine immediately (0.3-0.5mg IM for adults, 0.01mg/kg for children) 3
• Place patient in recumbent position with elevated legs if hypotensive 1
• Establish IV access and initiate fluid resuscitation if needed
• Administer oxygen if hypoxic
• Monitor vital signs every 15 minutes until stabilized 4

Step 3: Second-Line Medications

• Systemic corticosteroids may be considered for:
  • Severe anaphylaxis
  • Significant generalized urticaria/angioedema
  • Prevention of late-phase responses 4
  • Dosing: prednisone 0.5-1mg/kg orally or methylprednisolone 1-2mg/kg IV 4

Observation and Discharge Planning

Observation Period:

• Patients with isolated urticaria: minimum 1-2 hours 4
• Patients with resolved mild symptoms: 2 hours after resolution 4
• Patients with angioedema or anaphylaxis: 4-6 hours after symptom resolution 4
• Patients with history of biphasic reactions: longer observation warranted 4

Discharge Criteria:

• Resolution or significant improvement of symptoms
• Stable vital signs
• No evidence of respiratory compromise
• Patient able to tolerate oral medications

Discharge Instructions:

1. Prescribe antihistamines for continued use at home for 3-5 days
2. For patients with anaphylaxis or severe reactions:
   • Prescribe epinephrine auto-injector 1
   • Provide emergency action plan
   • Educate on proper use of auto-injector
3. Advise avoidance of identified or suspected triggers
4. Recommend follow-up with primary care physician within 1 week
5. Refer to allergist/immunologist for:
   • Recurrent episodes
   • Identification of triggers
   • Consideration of immunotherapy if appropriate 1

Important Clinical Considerations

• Most new-onset urticaria in adults is post-infectious or idiopathic, not true allergic reactions 2
• Antihistamines, not systemic steroids, are the mainstay of therapy for isolated urticaria 2
• Epinephrine is indicated only for anaphylaxis or airway-threatening angioedema, not for isolated urticaria 2
• Biphasic anaphylactic reactions can occur up to 6 hours after initial symptoms 4
• Patients on beta-blockers may have reduced response to epinephrine 1

Laboratory Evaluation

• For isolated urticaria without systemic symptoms, laboratory testing is generally not required in the ED
• For suspected anaphylaxis, consider:
  • Serum tryptase within 1-3 hours of symptom onset 2
  • Basic metabolic panel if IV fluids administered
  • Consider CBC if infection suspected as trigger

By following this structured approach to the management of hives in the emergency department, clinicians can effectively treat symptoms, prevent progression to more serious conditions, and provide appropriate follow-up care to reduce the risk of recurrence and complications.