What are the subsequent treatment options for a 54-year-old patient experiencing an allergic reaction after a wasp sting, post-administration of epinephrine (Epi)

From the Guidelines

For a 54-year-old experiencing an allergic reaction to a wasp sting after epinephrine administration, EMS should continue monitoring vital signs closely while preparing for potential second-phase reactions. After initial epinephrine, administer antihistamines such as diphenhydramine (Benadryl) 25-50mg IV/IM and consider H2 blockers like famotidine (Pepcid) 20mg IV, as suggested by the practice parameter update 2011 1. For respiratory symptoms, provide supplemental oxygen to maintain SpO2 >94% and consider albuterol nebulizer treatments (2.5mg in 3mL saline) for bronchospasm. If hypotension persists, establish IV access for fluid resuscitation with normal saline boluses (500-1000mL) and prepare for possible repeat epinephrine dosing (0.3-0.5mg IM, or 0.1mg IV push if severe shock) 1. Corticosteroids like methylprednisolone (125mg IV) or dexamethasone (10mg IV) should be given to prevent delayed or biphasic reactions.

During transport, continuously assess airway, breathing, circulation, and skin condition while obtaining a detailed history including timing of sting, onset of symptoms, medication allergies, and current medications. This comprehensive approach addresses both immediate symptoms and prevents potential deterioration, as anaphylaxis can be biphasic with symptoms returning after initial improvement. It is also crucial to identify the insect responsible for the sting reaction, as this information can be useful in establishing the diagnosis, prescribing treatment, and educating patients in avoidance measures 1.

Key considerations in the management of this patient include:

• Close monitoring of vital signs and preparation for potential second-phase reactions
• Administration of antihistamines, H2 blockers, and corticosteroids as needed
• Provision of supplemental oxygen and albuterol nebulizer treatments for respiratory symptoms
• Establishment of IV access for fluid resuscitation and potential repeat epinephrine dosing
• Continuous assessment of airway, breathing, circulation, and skin condition during transport
• Obtaining a detailed history of the patient's condition, including timing of sting, onset of symptoms, medication allergies, and current medications.

The patient should be referred to an allergist-immunologist for further evaluation and consideration of immunotherapy, as approximately 30% to 60% of patients with a history of systemic allergic reactions to an insect sting who have specific IgE antibodies detectable by means of skin or in vitro testing will experience a systemic reaction when re-stung 1.

From the FDA Drug Label

1 INDICATIONS & USAGE Adrenalin® is available as a single-use 1 mL vial and a multiple-use 30 mL vial for intramuscular and subcutaneous use. Emergency treatment of allergic reactions (Type I), including anaphylaxis, which may result from allergic reactions to insect stings, biting insects, foods, drugs, sera, diagnostic testing substances and other allergens, as well as idiopathic anaphylaxis or exercise-induced anaphylaxis.

INDICATIONS AND USAGE: Diphenhydramine hydrochloride in the injectable form is effective in adults and pediatric patients, other than premature infants and neonates, for the following conditions when diphenhydramine hydrochloride in the oral form is impractical Antihistaminic For amelioration of allergic reactions to blood or plasma, in anaphylaxis as an adjunct to epinephrine and other standard measures after the acute symptoms have been controlled, and for other uncomplicated allergic conditions of the immediate type when oral therapy is impossible or contraindicated.

For a 54-year-old patient experiencing an allergic reaction after being stung by a wasp, post epinephrine administration, the next steps in treatment may include:

• Monitoring for any signs of worsening symptoms or inadequate response to epinephrine
• Administration of diphenhydramine as an adjunct to epinephrine for amelioration of allergic reactions, if necessary 2
• Supportive care, such as maintaining a patent airway, breathing, and circulation, and administering oxygen if needed
• Transport to a medical facility for further evaluation and treatment, as anaphylaxis can be a life-threatening condition The primary goal is to ensure the patient's airway, breathing, and circulation are stable, and to provide additional treatment as needed to manage symptoms and prevent further complications 3.

From the Research

EMS Treatment for Allergic Reaction

• For a 54-year-old patient experiencing an allergic reaction after being stung by a wasp, the first line of treatment is epinephrine administration, as stated in 4, 5, 6, 7.
• According to 5, intramuscular epinephrine is the immediate treatment for all patients, while intravenous epinephrine should be used in patients in shock, either as a bolus or infusion, along with fluid resuscitation.
• As mentioned in 6, epinephrine should be administered intramuscularly into the anterolateral thigh as soon as the diagnosis is suspected, and antihistamines and corticosteroids are second-line medications that should never be given in lieu of, or prior to, epinephrine.

Post-Epi Administration

• After epinephrine administration, the patient should be monitored for any signs of biphasic reactions, as stated in 4, 5.
• According to 8, patients treated with prehospital epinephrine were less likely to have uncontrolled reactions, receive intravenous fluids in the emergency department, and be admitted after the reaction.
• As mentioned in 6, aggressive fluid resuscitation should also be used to treat the intravascular volume depletion characteristic of anaphylaxis, and patient observation and disposition should be individualized.

Additional Therapy

• Supplemental oxygen, intravenous fluids, antihistamines, and corticosteroids may be used as additional therapy, but should not delay the administration of epinephrine, as stated in 6.
• According to 8, the use of antihistamines may have a beneficial effect, while the use of corticosteroids in anaphylaxis should be revisited.
• As mentioned in 7, epinephrine is the drug of choice for anaphylaxis, and its therapeutic benefits exceed the risk when given in appropriate intramuscular doses.