What is the initial treatment for a patient presenting with anaphylaxis (severe allergic reaction) characterized by hives and throat swelling?

From the Guidelines

The initial treatment for a patient presenting with anaphylaxis characterized by hives and throat swelling is immediate administration of epinephrine (adrenaline) via intramuscular injection, preferably in the mid-outer thigh, as it is the most effective way to rapidly reverse the life-threatening effects of anaphylaxis. The standard adult dose is 0.3-0.5 mg of 1:1000 (1 mg/mL) concentration, while children should receive 0.01 mg/kg (up to 0.3 mg) 1. This dose can be repeated every 5-15 minutes if symptoms persist. After epinephrine administration, the patient should be placed in a supine position with legs elevated unless they are experiencing respiratory distress.

Supplemental oxygen should be provided, and intravenous access established for fluid resuscitation with normal saline to combat hypotension 1. Secondary medications include antihistamines (such as diphenhydramine 25-50 mg IV/IM) and corticosteroids (such as methylprednisolone 125 mg IV), though these should not delay epinephrine administration 1. Epinephrine works rapidly to reverse the life-threatening effects of anaphylaxis by causing vasoconstriction, reducing airway edema, increasing cardiac output, and suppressing inflammatory mediator release from mast cells and basophils.

Some key points to consider in the management of anaphylaxis include:

• The importance of prompt epinephrine administration, as delayed use can be ineffective and even fatal 1
• The need for supplemental oxygen and fluid resuscitation to support the patient's cardiovascular and respiratory systems
• The role of antihistamines and corticosteroids as secondary treatments, which should not delay the administration of epinephrine
• The importance of observing patients for at least 4-6 hours after symptom resolution and prescribing an epinephrine auto-injector upon discharge.

It is also crucial to note that anaphylaxis can have a wide range of clinical manifestations, and the diagnosis and management must occur rapidly 1. The clinical criteria proposed by the National Institute of Allergy and Infectious Diseases (NIAID) continue to provide a helpful framework in approaching patients with acute allergic symptoms.

From the FDA Drug Label

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. The signs and symptoms associated with 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. The initial treatment for a patient presenting with anaphylaxis characterized by hives and throat swelling is epinephrine (IM), as it is indicated for the emergency treatment of allergic reactions, including anaphylaxis 2.

• Key symptoms of anaphylaxis include:
  • Airway swelling
  • Laryngospasm
  • Bronchospasm
  • Urticaria or angioedema
  • Swelling of the eyelids, lips, and tongue
• Epinephrine (IM) is the first-line treatment for anaphylaxis, and diphenhydramine (IV) may be used as an adjunct to epinephrine and other standard measures after the acute symptoms have been controlled 3.

From the Research

Initial Treatment for Anaphylaxis

The initial treatment for a patient presenting with anaphylaxis, characterized by hives and throat swelling, involves several key steps:

• Administration of intramuscular epinephrine into the lateral thigh, as it is the first-line treatment for any type of anaphylaxis 4, 5, 6, 7
• Removal of the trigger, if possible, to prevent further allergic reaction 5
• Supportive care for the patient's airway, breathing, and circulation, which may include early intubation for airway obstruction 5, 7
• Administration of adjunct medications, such as histamine H1 and H2 antagonists, corticosteroids, beta2 agonists, and glucagon, after epinephrine administration 5, 6

Use of Corticosteroids

Corticosteroids are frequently used in the emergency management of anaphylaxis, although there is no compelling evidence to support or oppose their use 8:

• They may reduce the length of hospital stay, but do not reduce revisits to the emergency department 8
• There is no consensus on whether corticosteroids reduce biphasic anaphylactic reactions 8
• Animal studies demonstrate that corticosteroids act through multiple mechanisms, with effects becoming evident 4 to 24 hours after administration 8

Monitoring and Disposition

Patients should be monitored for a biphasic reaction, which can occur within 4 to 12 hours, depending on risk factors for severe anaphylaxis 5:

• Mandatory observation periods are not necessary, as biphasic reactions are difficult to predict and may occur outside of typical observation periods 7
• Disposition depends on patient presentation and response to treatment, with some patients requiring hospital admission for further monitoring and treatment 7