What is anaphylaxis?

From the Guidelines

Anaphylaxis is a severe, potentially life-threatening allergic reaction requiring immediate treatment with epinephrine (adrenaline) at a dose of 0.3 mg intramuscularly for adults and children greater than 30 kg, and 0.15 mg intramuscularly for children 15 to 30 kg, as recommended by the 2015 American Heart Association and American Red Cross guidelines update for first aid 1.

Key Considerations

• Anaphylaxis involves 2 or more body systems and can be life-threatening, with symptoms including respiratory difficulty, cutaneous manifestations, cardiovascular effects, and gastrointestinal cramping and diarrhea 1.
• Epinephrine autoinjectors are the primary treatment for anaphylaxis, and individuals at risk should carry them at all times and wear medical identification.
• First aid providers should call 9-1-1 immediately when caring for a person with suspected anaphylaxis or a severe allergic reaction 1.

Administration and Follow-up

• Epinephrine should be administered via an auto-injector into the outer thigh muscle, and can be repeated every 5-15 minutes if symptoms persist.
• The patient should lie flat with legs elevated unless breathing is difficult.
• Secondary treatments include antihistamines and corticosteroids, but these should never replace epinephrine as the first-line treatment.

Prevention and Education

• Common triggers of anaphylaxis include foods, medications, insect stings, and latex.
• Individuals with a history of anaphylaxis should be educated on recognition and treatment of anaphylaxis, and should carry epinephrine auto-injectors at all times.
• Effective care for individuals at risk of anaphylaxis requires a comprehensive management approach involving families, allergic children, schools, camps, and other youth organizations, as well as confirmation of the trigger, discussion of avoidance of the relevant allergen, and education of supervising adults 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.

12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action Epinephrine acts on both alpha and beta-adrenergic receptors. 12. 2 Pharmacodynamics Through its action on alpha-adrenergic receptors, epinephrine lessens the vasodilation and increased vascular permeability that occurs during anaphylaxis, which can lead to loss of intravascular fluid volume and hypotension

Anaphylaxis Treatment: Epinephrine (IM) is indicated for the emergency treatment of anaphylaxis, a severe, life-threatening allergic reaction. The signs and symptoms of anaphylaxis include:

• Flushing
• Apprehension
• Syncope
• Tachycardia
• Thready or unobtainable pulse associated with hypotension
• Convulsions
• Vomiting
• Diarrhea and abdominal cramps
• Involuntary voiding
• Airway swelling
• Laryngospasm
• Bronchospasm
• Pruritus
• Urticaria or angioedema
• Swelling of the eyelids, lips, and tongue Epinephrine works by acting on both alpha and beta-adrenergic receptors to alleviate the symptoms of anaphylaxis, including bronchospasm, hypotension, and increased vascular permeability 2 2.

From the Research

Definition and Symptoms of Anaphylaxis

• Anaphylaxis is a life-threatening, multisystem allergic reaction that can cause airway, breathing, or circulatory compromise 3
• Symptoms of anaphylaxis are rapid in onset and can include urticaria, difficulty breathing, and mucosal swelling 4
• Anaphylaxis can manifest signs and symptoms related to the cutaneous, respiratory, cardiovascular, and gastrointestinal systems 5

Treatment of Anaphylaxis

• Epinephrine is the first-line treatment for anaphylaxis and should be administered intramuscularly as soon as the diagnosis is suspected 5, 3, 4
• Antihistamines and corticosteroids are second-line medications and should never be given in lieu of, or prior to, epinephrine 5, 6
• Aggressive fluid resuscitation should also be used to treat the intravascular volume depletion characteristic of anaphylaxis 5, 3
• Intravenous epinephrine should be used in patients in shock, either as a bolus or infusion, along with fluid resuscitation 3

Importance of Early Treatment

• Delayed epinephrine administration is a risk factor for fatal anaphylaxis 7, 6
• Early treatment with epinephrine is critical to prevent a potentially fatal outcome 5, 3, 4, 6
• Patients treated with prehospital epinephrine were less likely to have uncontrolled reactions, receive intravenous fluids in ED, and to be admitted after the reaction 7

Disposition and Observation

• Patient observation and disposition should be individualized, as there is no well-defined period of observation after resolution of signs and symptoms 5
• Mandatory observation periods are not necessary, because biphasic reactions are difficult to predict and may occur outside of typical observation periods 3, 4
• Patients should be monitored for a biphasic reaction (i.e., recurrence of anaphylaxis without reexposure to the allergen) for four to 12 hours, depending on risk factors for severe anaphylaxis 4