Anaphylaxis

Anaphylaxis is a dramatic, acute atopic reaction marked by the sudden onset of rapidly progressive urticaria and respiratory distress. A severe reaction may initiate vascular collapse, leading to systemic shock and, possibly, death.

Causes

Common causes of anaphylaxis include:

• Food
• Medication
• Insect stings
• Latex

Less common causes include:

• Food-Dependent Exercise-Induced Anaphylaxis
• Idiopathic Anaphylaxis

Symptoms

The following are the most common symptoms of anaphylaxis. However, each child may experience symptoms differently. Symptoms may include:

• tightness or swelling of the throat
• severe itching of the skin
• nausea and vomiting
• stomach pain
• heart failure
• irregular heart beats
• lowered blood pressure

The symptoms of anaphylaxis may resemble other medical conditions. Always consult your child's physician for a diagnosis.

Diagnostic tests

No tests are required to identify anaphylaxis. The patient's history and signs and symptoms establish the diagnosis. If signs and symptoms occur without a known allergic stimulus, other possible causes of shock, such as acute myocardial infarction, status asthmaticus, and heart failure, must be ruled out.

Skin testing may help to identify a specific allergen. Because skin tests can cause serious reactions, a scratch test should be done first in high-risk situations.

Treatment

Always an emergency, anaphylaxis requires an immediate injection of epinephrine 1:1 ,000 aqueous solution, 0.1 to 0.5 ml for mild signs and symptoms. If signs and symptoms are severe, repeat the dose every 5 to 20 minutes, as directed.

In the early stages of anaphylaxis, when the patient remains conscious and normotensive, give epinephrine I.M. or subcutaneously. Speed it into circulation by massaging the injection site. In severe reactions, when the patient is unconscious and hypotensive, give the drug I.V., as ordered.

Establish and maintain a patent airway. Watch for early signs of laryngeal edema (stridor, hoarseness, and dyspnea), which will probably require endotracheal tube insertion or a tracheotomy and oxygen therapy.

If cardiac arrest occurs, begin cardiopulmonary resuscitation. Assist with ventilation, closed-chest cardiac massage, and sodium bicarbonate administration, as ordered.

Watch for hypotension and shock. As ordered, maintain circulatory volume with volume expanders (plasma, plasma expanders, normal saline solution, and albumin), as needed. As prescribed, administer I.V. vasopressors, norepinephrine, and dopamine to stabilize blood pressure. Monitor blood pressure, central venous pressure, and urine output.

After the initial emergency, administer other medication, such as subcutaneous epinephrine, long-acting epinephrine, corticosteroids, and diphenhydramine I.V., for long-term management and aminophylline I.V. over 10 to 20 minutes for bronchospasm.

Prevention

The only way to prevent anaphylaxis is to avoid known allergens. Some of the most common include bee stings, fish and shellfish, penicillin, latex, certain vaccines, nuts and seeds, and certain food additives. If you have a history of anaphylaxis, you should wear a medical ID bracelet containing information on your allergies.

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