What is the treatment for anaphylaxis due to wasp sting in individuals with a known allergy?

Treatment for Anaphylaxis Due to Wasp Sting in Individuals with Known Allergy

Immediate intramuscular epinephrine is the first-line treatment for anaphylaxis due to wasp sting in individuals with known allergies, and should be administered without delay. 1, 2, 3

Immediate Management

1. Administer epinephrine immediately:

   • Dose: 0.01 mg/kg (up to 0.3 mg) in children; 0.3-0.5 mg in adults depending on severity
   • Route: Intramuscular injection in the anterolateral thigh (achieves faster and higher plasma concentration than subcutaneous or arm injection)
   • Timing: Critical - delayed use can be ineffective or fatal 1
   • Repeat dosing may be required for persistent or recurrent symptoms

2. Remove stinger (if present):

   • Remove within first 10-20 seconds to prevent additional venom injection
   • Method: Flick or scrape away with fingernail
   • Avoid grasping the venom sac as this can inject more venom 1, 2

3. Supportive care:

   • Position patient appropriately (supine with legs elevated if hypotensive)
   • Establish IV access
   • Administer oxygen if needed
   • Monitor vital signs

4. Additional medications (only after epinephrine):

   • Antihistamines (H1 antagonists) for urticaria and pruritus
   • Corticosteroids to prevent biphasic or protracted reactions
   • β2-agonists for bronchospasm
   • IV fluids for hypotension 1, 4

Important Clinical Considerations

• Antihistamines and corticosteroids are NOT substitutes for epinephrine in anaphylaxis 1
• No contraindication to epinephrine in life-threatening anaphylaxis, even in patients with cardiovascular disease 1
• Observation period: Monitor for 4-12 hours after initial reaction to watch for biphasic reactions 2, 4
• Risk factors for severe reactions: Older age, cardiovascular disease, asthma, high baseline serum tryptase, short latency time after sting, and absence of skin symptoms 5

Long-term Management

1. Prescription for auto-injectable epinephrine:

   • All patients with previous systemic reactions should carry epinephrine auto-injectors
   • Educate patients and caregivers on proper administration technique 2, 6

2. Referral to allergist-immunologist for patients who have experienced systemic reactions to:

   • Evaluate risk of future reactions
   • Consider venom immunotherapy (VIT)
   • Provide education on sting avoidance 1, 2

3. Avoidance measures:

   • Remove nests near home
   • Avoid bright-colored clothing and strong scents
   • Wear protective clothing outdoors
   • Be cautious around food/beverages outdoors
   • Avoid walking barefoot 1, 2

4. Medical identification:

   • Consider medical ID bracelet or necklace 1

Common Pitfalls to Avoid

• Delaying epinephrine administration - this is associated with fatal outcomes 1, 2
• Relying on antihistamines or corticosteroids alone - these are adjunctive treatments only 1
• Poor patient education - many patients with venom allergies have incorrect ideas about after-sting behavior and improper technique with auto-injectors 6
• Inadequate follow-up - failure to refer to an allergist for long-term management and consideration of immunotherapy 1, 2
• Insufficient observation time - patients should be monitored for biphasic reactions 4

The evidence clearly demonstrates that prompt administration of epinephrine is the cornerstone of anaphylaxis management, with delayed use potentially leading to fatal outcomes. Long-term management should focus on prevention through education, avoidance strategies, and consideration of venom immunotherapy.