EVALUATION AND TREATMENT OF ANAPHYLAXIS

For making the diagnosis and determining the intensity of the reaction to formulate the management strategy, the history and physical examination are essential.

1. Patient history

a) The cause of the anaphylaxis should be determined.

— Antibiotics including penicillin are a major source of negative medication responses. The majority of responses happen after parenteral administration as opposed to oral.

— Radiocontrast media cause anaphylactoid reactions at a rate of 0.22% for ionic (high osmolar) agents. The risk of death has been estimated to be 1 in 10,000 (0.01%). Nonionic (low osmolar) agents cause anaphylactoid reactions at a rate of 0.04%.

— Lidocaine and other local anesthetics rarely cause true allergic reactions, but many patients report “allergy to ‘caines’” because a variety of nonallergic reactions are associated with its administration.

b) The route and timing of exposure should be ascertained. The route may be by injection, ingestion, inhalation, or cutaneous absorption.

c) Other details that may be crucial for the evaluation and management of the case include previous reactions to the same substance and the severity of those reactions, underlying medical conditions like cardiovascular disease or pulmonary disease, current medications like beta-blockers, antihistamines, and corticosteroids, as well as medication allergies.

2. Laboratory testing (see Table)

DIFFERENTIAL DIAGNOSES OF ANAPHYLAXIS 

3. Radiography: A chest radiograph may reveal hyperinflation or atelectasis.

THERAPY

1. Prompt intervention is vital: 

a) Antigen exposure needs to be stopped, and vital signs need to be watched. At the first sign of the reaction, any intravenous antigen infusion should have been discontinued, and any topical medications should have been removed. Gastric lavage should be taken into consideration if the agent was recently consumed. 

b) Epinephrine is administered to prevent mediator release. It relaxes laryngeal and bronchial smooth muscle and supports blood pressure.

i) Side effects: Epinephrine may cause vomiting, hypertension, tremor, and tachydysrhythmia.

ii) Possible contraindications include cardiac ischemia, severe hypertension, and pregnancy. Glucagon can be substituted if epinephrine is contraindicated.

iii) Dosage and administration

— Epinephrine 0.1% (1:1,000 preparation). In patients with stable vital signs, epinephrine 0.1% is given subcutaneously or intramuscularly every 15 minutes as required. The dosage is 0.3 to 0.5 mL for adults and 0.01 mg/kg for children.

— Epinephrine 0.01% (1:10,000 preparation) is administered intravenously when there is significant airway compromise or shock. For adults, the dosage is 1 to 3 mL, administered slowly intravenously (or diluted in normal saline to 10 mL and administered via an endotracheal tube). Children receive 0.1 mg/kg by slow intravenous infusion.

c) Stabilization of airway, breathing, and circulation (ABCs)

i) The airway should be observed closely and supported as needed with endotracheal intubation or cricothyrotomy.

ii) High-flow oxygen should be administered.

iii) Blood pressure should be supported by placing the patient in a recumbent position, infusing intravenous fluids, and, if necessary, administering a continuous infusion of epinephrine.

d) Treatment of bronchospasm is with Beta agonists or nebulized epinephrine

e) Histamine receptor blockade

i) Histamine-1 receptors should be blocked with an antihistamine such as diphenhydramine (1 to 2 mg/kg intravenously, up to a total dose of 50 mg, initially and every 6 to 8 hours as needed, for adults and children).

ii) Histamine-2 receptors. Blocking the histamine-2 receptors with an agent such as cimetidine or ranitidine may also be advantageous.

f) Prevention of late-phase reactions: A corticosteroid (e.g., prednisolone, 1 to 2 mg/kg intravenously every 6 hours until conversion to oral medication) should be administered intravenously in an attempt to abort late-phase reactions.

g) Treatment of refractory anaphylaxis: In the presence of β- blockade, anaphylaxis may be particularly refractory to treatment, and glucagon (0.05 mg/kg administered as an intravenous bolus, followed by an infusion at a rate of 0.07 mg/kg/hour) may need to be employed.

2. Late-phase reactions may occur in the ensuing 6 to 48 hours. The treatment strategy for a late-phase reaction is the same as that for an initial reaction.