What is the best management for acute hypersensitivity reactions in the Emergency Room (ER)?

Management of Acute Hypersensitivity Reactions in the Emergency Room

The best management for acute hypersensitivity reactions in the ER is immediate administration of intramuscular epinephrine as first-line treatment, followed by airway assessment, fluid resuscitation, and adjunctive therapies based on symptom severity. 1

Initial Assessment and Immediate Actions

• Stop administration of any suspected triggering agent or medication immediately 1
• Assess and maintain the ABCs (Airway, Breathing, Circulation) while calling for medical assistance 1
• Position the patient appropriately: Trendelenburg for hypotension, sitting up for respiratory distress, recovery position if unconscious 1
• Maintain intravenous access and administer oxygen if needed 1

First-Line Treatment

• Administer epinephrine 0.2-0.5 mg (1 mg/mL) intramuscularly into the lateral thigh muscle for suspected anaphylaxis; may repeat every 5-15 minutes as needed 1, 2
• For pediatric patients, administer epinephrine at 0.01 mg/kg (1 mg/mL) intramuscularly to a maximum dose of 0.5 mL 1
• Do not delay epinephrine administration, as this increases risk of mortality and biphasic reactions 1

Fluid Resuscitation

• Administer normal saline 1-2 L IV at a rate of 5-10 mL/kg in the first 5 minutes 1
• For severe hypotension, give crystalloids or colloids in boluses of 20 mL/kg, followed by slow infusion 1

Adjunctive Treatments

• Administer H1 antihistamine: diphenhydramine 50 mg IV 1
• Administer H2 antihistamine: ranitidine 50 mg IV 1
• Give corticosteroids: methylprednisolone 1-2 mg/kg IV every 6 hours 1, 3
  • Note: Corticosteroids have no role in treating acute anaphylaxis due to slow onset but may help prevent prolonged reactions 1

Management of Specific Complications

For Hypotension Unresponsive to Epinephrine

• Consider vasopressors: dopamine 400 mg in 500 mL at 2-20 μg/kg/min 1
• Alternative: vasopressin 25 units in 250 mL of 5% dextrose water (0.1 U/mL) at 0.01-0.04 U/min 1

For Bradycardia

• Administer atropine 600 μg IV 1
• For patients on beta-blockers with refractory symptoms, administer glucagon 1-5 mg IV over 5 minutes 1

For Bronchospasm

• Consider salbutamol IV infusion or metered-dose inhaler if a suitable breathing system connector is available 1
• Consider IV aminophylline or magnesium sulfate for persistent bronchospasm 1

Post-Reaction Monitoring and Management

• Monitor vital signs until complete resolution of symptoms 1
• Observe for at least 6 hours after severe reactions or those requiring multiple doses of epinephrine 1
• Consider 24-hour observation for severe reactions due to risk of biphasic anaphylaxis 1
• Obtain blood samples for mast cell tryptase levels (optimally 15 minutes to 3 hours after symptom onset) 1

Special Considerations

• Distinguish between anaphylaxis and cytokine-release/hypersensitivity reactions, as management differs 1
• For cytokine-release reactions, consider slowing or temporarily stopping infusion rather than discontinuing completely 1
• Be aware that vasovagal reactions can mimic anaphylaxis but typically present with bradycardia rather than tachycardia and lack cutaneous manifestations 1
• For patients on beta-blockers with refractory cardiovascular effects, glucagon may be particularly helpful 1

Common Pitfalls to Avoid

• Delaying epinephrine administration while waiting for antihistamines or corticosteroids to take effect 1, 4
• Administering epinephrine intravenously instead of intramuscularly (except in cases of cardiovascular collapse) 1
• Failing to recognize early warning signs such as patients feeling odd or uncomfortable before a full reaction develops 1
• Underestimating the severity of reactions that initially appear mild but can rapidly progress 4
• Discharging patients too early without adequate observation for biphasic reactions 1