Hymenoptera Stings Treatment & Management

Prehospital care must assess severity immediately and provide immediate appropriate treatment, because the most endangered patients die within 30 minutes of a sting.

Local reactions can be life threatening if swelling occludes the airway. Initiate invasive measures to secure the airway if this occurs. Otherwise, the following local care measures suffice:

• Provide supplemental oxygen

• Diphenhydramine limits the size of the local reaction.

• Clean the wound and remove the stinger if present.

• Apply ice or cool packs.

• Elevate the extremity to limit edema.

Manage generalized reactions similarly to anaphylaxis, even in the absence of shock. Increased vascular permeability in anaphylaxis may result in transfer of 50% of the intravascular fluid into the extravascular space within 10 minutes. ^[1] Check airway and ventilatory status. Treatment should include an initial intravenous (IV) bolus of 10-20 mL/kg isotonic crystalloids in addition to diphenhydramine and epinephrine.

If the patient has not removed the stinger, it should be removed as soon as possible by the first caregiver on the scene. Delay increases venom load, so the fastest removal technique is the best. Pinching and traction is an acceptable technique.

EMT or self-administration of intramuscular or subcutaneous epinephrine should be initiated immediately in the event of severe reaction. Intramuscular epinephrine injections into the lateral thigh provide more rapid absorption and higher plasma epinephrine levels than intramuscular or subcutaneous injections administered in the arm. ^[1]

Epinephrine is the mainstay of treatment for anaphylaxis. Corticosteroids should be administered in severe cases of envenomation, with the caution that steroids do little to improve symptoms acutely and no definitive evidence exists that corticosteroids reduce recurrent or prolonged anaphylaxis. ^[17]

H2 blockers such as ranitidine and cimetidine may be given intravenously. ^[18] Administration of one of these medications combined with diphenhydramine is superior to diphenhydramine alone. ^[1]

In cases of refractory anaphylaxis, glucagon may be helpful if concomitant beta-blockers are preventing adequate response to epinephrine treatment. ^[1]

Vasopressors such as epinephrine or dopamine can be used to provide vascular support.

Patients developing respiratory arrest require ventilatory support.

Blood products may be required in the event of disseminated intravascular coagulation (DIC).

Repeated doses of epinephrine may be indicated for severe cases.

In the event of cardiopulmonary arrest due to anaphylaxis, intravenous epinephrine should be administered as a first-line agent. ^[1]

Consider further inpatient care for all patients with life-threatening reactions. Observe for sufficient duration to ensure symptoms do not rebound after initial treatment. Rebound phenomena may occur up to 12 hours after sting. Respiratory and circulatory support may be needed if secondary organ damage has occurred.

Refer all patients with generalized reactions to an allergist as soon as possible, because risk of fatal reaction is inversely related to length of time since the last sting.

Avoiding stings is vitally important for persons who are hypersensitive. Whenever these patients are outdoors, they should adhere to the following suggestions:

• Avoid using perfumes or hygiene products that include perfumes, as these may attract flying Hymenoptera.

• Avoid wearing bright colors.

• Avoid known hive or nest locations.

• Do not use noisy equipment such as lawn mowers, edgers, or blowers within 50 yards of beehives or 150 yards of Africanized bee colonies.

• Do not flail arms when confronted by bees or wasps because smashing one often incites others to sting.

Following severe reactions, individuals should be referred to an allergist/immunologist for potential immunotherapy and desensitization. Administration of venom-specific immunotherapy (VIT) is an established mode of treatment and offers long-term protection in 85-95% of cases. ^[3] New research on anti-immunoglobin (Ig) E antibody has shown promising results as a combination therapy for those unable to tolerate standard VIT. ^[3] A literature review and case report from 2014 suggest that adjunctive treatment with omalizumab can improve symptoms in patients with mastocytosis on VIT therapy. ^[19]

Guidelines on hymenoptera venom allergy immunotherapy have been issued by the European Academy of Allergy and Clinical Immunology. ^[20] They are summarized as follows:

• VIT recommended in adults with systemic sting reactions confined to generalized skin symptoms if quality of life is impaired
• VIT recommended in children and adults with detectable sensitization and systemic sting reactions exceeding generalized skin symptoms
• VIT not recommended in individuals with incidentally detected sensitization and no systemic symptoms
• Factors not considered a higher risk of adverse events are severe initial sting reaction, high skin-test reactivity, and high venom-specific IgE levels
• Pretreatment with H1 antihistamines recommended; reduces large local reactions and, to some extent, systemic adverse events
• Recommended VIT duration is at least 3 years; 5 years recommended in patients with severe initial sting reactions
• Lifelong VIT may be recommended in the following: (1) highly exposed patients with honeybee venom allergy, (2) patients with very severe initial sting reactions (Muller grade IV or grades III-IV, according to Ring and Messmer), and (3) patients with systemic adverse effects during VIT, as they are major risk factors for relapse
• All available diagnostic tests, including determination of venom-specific IgE, IgG, basophil activation testing response, and allergen-blocking capacity, are not capable of estimating the individual risk for relapse
• Most reliable method to evaluate effectiveness of VIT is sting challenges

Refer all patients with generalized reactions for allergy testing and desensitization, if indicated. Provide means to self-administer epinephrine and diphenhydramine to all patients with generalized reactions, and advise them to wear medic alert bracelets.

Continue treatment with steroids in the ED for 3-5 days. Continue administering antihistamines for at least 24 hours continuous dosing.

Cool sting sites for 12 hours. Keep extremities with stings elevated for 12 hours when development of edema may present difficulties.