What is the treatment for protracted anaphylaxis?

Treatment of Protracted Anaphylaxis

Protracted anaphylaxis requires repeated doses of intramuscular epinephrine and, in severe refractory cases, intravenous epinephrine infusion, along with aggressive fluid resuscitation and prolonged observation or hospital admission. 1

Immediate Management

First-Line Treatment: Epinephrine

• Administer intramuscular epinephrine immediately at 0.3-0.5 mg (1:1000) for adults or 0.01 mg/kg for children (maximum 0.5 mg adults, 0.3 mg children) into the anterolateral thigh. 1, 2
• Repeat epinephrine every 5-15 minutes as needed if symptoms persist or progress—this remains first-line therapy over adjunctive treatments. 1, 3
• Do not delay epinephrine administration, as delay is associated with higher morbidity and mortality. 1

Transition to IV Epinephrine for Refractory Cases

• For protracted anaphylaxis unresponsive to repeated IM doses, transition to intravenous epinephrine infusion at 0.05-2 mcg/kg/min, titrated to achieve adequate blood pressure and symptom control. 1, 2, 4
• In cases of severe hypotension or cardiovascular collapse, administer IV epinephrine 0.05-0.1 mg (1:10,000 dilution) slowly, followed by continuous infusion at 5-15 mcg/min. 2, 3

Supportive Care

Volume Resuscitation

• Establish IV access immediately and administer crystalloid fluid bolus of 500-1000 mL for adults or 20 mL/kg for children. 2
• Rapid and aggressive volume expansion is mandatory in protracted anaphylaxis, as patients can develop profound intravascular volume depletion. 1

Patient Positioning and Oxygen

• Position patient supine with legs elevated (unless respiratory distress precludes this). 2, 3
• Provide supplemental oxygen and monitor oxygen saturation continuously. 2

Airway Management

• For persistent bronchospasm unresponsive to epinephrine, administer nebulized albuterol 2.5-5 mg in 3 mL saline. 2, 3
• Be prepared for advanced airway management if laryngeal edema or severe bronchospasm develops. 1

Adjunctive Medications (Second-Line Only)

Glucocorticoids

• Administer IV glucocorticoids specifically to prevent protracted anaphylaxis, though they have no role in acute symptom management due to delayed onset of action. 1
• Dosing: methylprednisolone 1-2 mg/kg IV every 6 hours or prednisone 0.5 mg/kg orally for less severe cases. 1
• Important caveat: Recent evidence shows glucocorticoids do not reliably prevent biphasic reactions, but they may have a role in protracted anaphylaxis given the prolonged inflammatory response. 1

Antihistamines

• H1 antihistamine: diphenhydramine 25-50 mg IV/IM (1-2 mg/kg in children). 2, 3, 5
• H2 antihistamine: ranitidine 50 mg IV for adults (1 mg/kg for children). 2
• Critical warning: Antihistamines address only cutaneous symptoms and should never delay or replace epinephrine. 1

Special Situations

Patients on Beta-Blockers

• If unresponsive to epinephrine, administer glucagon 1-5 mg IV (20-30 mcg/kg in children, maximum 1 mg) over 5 minutes, followed by infusion at 5-15 mcg/min. 1, 2, 3
• Monitor for nausea and vomiting with glucagon administration. 1

Vasopressor Support

• For hypotension refractory to epinephrine and fluids, consider dopamine infusion at 2-20 mcg/kg/min titrated to maintain systolic BP >90 mmHg. 1, 3

Observation and Monitoring

Duration of Observation

• Protracted anaphylaxis requires prolonged observation or hospital admission, as symptoms by definition persist beyond the typical timeframe. 1
• Standard anaphylaxis requires 4-6 hours observation, but protracted cases warrant extended monitoring until complete symptom resolution, often requiring intensive care unit admission. 1
• Patients requiring multiple epinephrine doses are at higher risk for protracted courses and should be observed longer. 1

Continuous Monitoring

• Monitor vital signs (blood pressure, heart rate, respiratory rate, oxygen saturation) continuously during acute phase. 2
• Keep patients under observation in a setting capable of managing anaphylaxis until symptoms have fully resolved. 1

Discharge Planning

• Provide epinephrine auto-injector prescription with demonstration of proper use. 1, 2, 3
• Educate on risk of recurrent reactions and when to use auto-injector. 1
• Refer to allergist-immunologist for comprehensive evaluation, trigger identification, and long-term management plan. 1

Common Pitfalls to Avoid

• Never substitute antihistamines or corticosteroids for epinephrine—this is the most common error and significantly increases risk of progression to life-threatening reaction. 1
• Do not use subcutaneous epinephrine instead of intramuscular, as absorption is delayed. 3
• Avoid administering IV epinephrine outside monitored settings except in cases of cardiovascular collapse. 3
• Do not discharge patients with protracted anaphylaxis after brief observation—these patients require extended monitoring. 1