What is the workup and treatment for a patient presenting with anaphylaxis?

From the Guidelines

The immediate treatment for anaphylaxis is intramuscular epinephrine (adrenaline) 0.3-0.5 mg (1:1000 concentration) for adults or 0.15 mg for children under 30 kg, injected into the mid-outer thigh, as recommended by the most recent guidelines 1. This can be repeated every 5-15 minutes if symptoms persist. Simultaneously, the patient should be placed in a supine position with legs elevated unless respiratory distress is present, and supplemental oxygen should be administered. Establish IV access for fluid resuscitation with normal saline (1-2 liters for adults) to counter hypotension. Second-line medications include H1 antihistamines (diphenhydramine 25-50 mg IV/IM), H2 blockers (ranitidine 50 mg IV), and corticosteroids (methylprednisolone 125 mg IV) to prevent biphasic reactions. For bronchospasm, nebulized albuterol (2.5-5 mg) may be given. Workup includes:

• Identifying and removing the trigger
• Monitoring vital signs continuously
• Obtaining serum tryptase levels within 3 hours of symptom onset Epinephrine is the cornerstone of treatment because it rapidly reverses the life-threatening effects of anaphylaxis by causing vasoconstriction, reducing mucosal edema, increasing cardiac output, and bronchodilation, as supported by recent studies 1. After stabilization, patients should be observed for 4-8 hours due to the risk of biphasic reactions and discharged with an epinephrine auto-injector, an action plan, and referral to an allergist, as recommended by the guidelines 1.

The risk factors for severe anaphylaxis include cardiovascular disease, asthma, older age, and additional coexisting, comorbid conditions, and medications and stinging insects are the leading triggers in adults, with foods and stinging insects the most frequently implicated triggers in children and adolescents 1. Biphasic anaphylaxis is a recurrence of anaphylaxis after appropriate treatment, and the estimated number needed to monitor with extended observation to be able to detect 1 episode of biphasic anaphylaxis before discharge would be 41 for patients with a more severe initial presentation of anaphylaxis and 13 for patients with multiple epinephrine doses, as reported in recent studies 1. The patient presenting with severe anaphylaxis and/or requiring more aggressive treatment should be considered for longer observation time for a potential biphasic reaction following complete resolution of signs and symptoms, and antihistamines and glucocorticoids are not reliable interventions to prevent biphasic anaphylaxis, as stated in the guidelines 1.

In terms of management, the allergist-immunologist has the training and expertise to obtain a detailed allergy history, coordinate laboratory and allergy testing, evaluate the benefits and risks of therapeutic options, and counsel the patient on avoidance measures, and consultation with an allergist-immunologist is recommended when the diagnosis is doubtful or incomplete, or when help is needed in evaluation and management of medication use or side effects, as recommended by the guidelines 1. The patient should be educated on anaphylaxis, including avoidance of identified triggers, presenting signs and symptoms, biphasic anaphylaxis, treatment with epinephrine, and the use of epinephrine auto-injectors, and they should be referred to an allergist, as stated in the guidelines 1.

Overall, the management of anaphylaxis requires a comprehensive approach, including prompt treatment with epinephrine, identification and removal of the trigger, monitoring of vital signs, and education on avoidance measures and the use of epinephrine auto-injectors, as supported by recent studies and guidelines 1.

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 workup for anaphylaxis involves identifying the signs and symptoms associated with the condition, such as:

• Flushing
• Apprehension
• Syncope
• Tachycardia
• Hypotension
• Convulsions
• Vomiting
• Diarrhea
• Abdominal cramps
• Involuntary voiding
• Airway swelling
• Laryngospasm
• Bronchospasm
• Pruritus
• Urticaria or angioedema
• Swelling of the eyelids, lips, and tongue Treatment involves emergency administration of epinephrine (IM) 2.

From the Research

Workup for Anaphylaxis

• The workup for anaphylaxis involves prompt recognition of symptoms, including urticaria, difficulty breathing, and mucosal swelling 3
• Serum tryptase levels can be obtained to reflect mast cell degranulation when the clinical diagnosis of anaphylaxis is not clear 3
• Identification of the trigger is crucial, with common triggers including medications, stinging insect venoms, and foods 3

Treatment of Anaphylaxis

• Epinephrine is the first-line treatment for anaphylaxis, administered intramuscularly in the lateral thigh 4, 3, 5
• Intravenous epinephrine can be used in patients in shock, along with fluid resuscitation 5
• Adjunct medications, such as histamine H1 and H2 antagonists, corticosteroids, beta2 agonists, and glucagon, can be considered after epinephrine administration 3
• Antihistamines may have a beneficial effect in anaphylaxis management, while the use of corticosteroids should be revisited 6

Management and Observation

• Patients should be monitored for a biphasic reaction, which can occur within 4 to 12 hours after the initial reaction 3
• Mandatory observation periods are not necessary, as biphasic reactions can be difficult to predict and may occur outside of typical observation periods 5
• An emergency action plan should be developed, and patients should be educated on avoidance of triggers and appropriate use of an epinephrine auto-injector 4, 3