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Anaphylaxis
OVERVIEW: Anaphylaxis is an acute, systemic allergic reaction following exposure to an allergen in a sensitized person.
SIGNS AND SYMPTOMS: • Itching, flushing, rash, swelling
• Cough, difficult breathing
• Runny nose, congestion, noisy breathing
• Difficulty swallowing
• Nausea, vomiting, diarrhea, cramps, bloating
• Rapid heart rate, low blood pressure, shock, fainting
• Malaise, shivering
• Dilated pupils
CAUSES: • Allergic reaction following exposure to allergen
• Other anaphylaxis-like syndromes may have other causes.
• Some important causes of anaphylaxis are:
• Antibiotics (e.g., penicillin)
• Blood products
• Diagnostic chemicals
• Exercise
• Foods (e.g., peanuts, nuts, fish, shellfish, cow milk, eggs, soybean)
• Insect stings (e.g., honeybees, wasps, kissing bugs, deer flies)
• Latex rubber (condoms, gloves, catheters)
• Vaccines
SCOPE: • The incidence of anaphylaxis is unknown.
• Between 20,000 and 50,000 cases of anaphylaxis occur per year in United States.
• There are 3-7 anaphylaxis deaths per 10,000 people annually.
MOST OFTEN AFFECTED: Anaphylaxis affects all ages, males and females in equal proportion. Some allergies have a genetic predisposition.
RISK FACTORS: Previous anaphylaxis; history of allergies or asthma
DIAGNOSIS PHYSICAL EXAMINATION: • Signs and symptoms of allergic reactions
• Other conditions with similar signs should be investigated.
TESTS AND PROCEDURES: • Blood tests will be done to look for signs of inflammation or infection.
• Arterial blood may be obtained.
TREATMENT GENERAL MEASURES: • Treatment depends on the severity of the allergic reaction.
• Severe reaction requires first aid. Seek hospital care as quickly as possible.
• Maintain airway, breathing, and circulation as needed.
• If sting or bite is on arm or leg, apply constrictive band between sting and body (do not apply too tightly and loosen if uncomfortable).
• Individuals with swelling, rash, or mild breathing problems may be released from hospital when symptoms resolve; they are then managed on an outpatient basis.
• Moderate to severe anaphylaxis requires hospitalization, possibly mechanical breathing.
• Allergist may be consulted if the cause of anaphylaxis is unclear.
• Individuals with anaphylaxis from insect stings may benefit from desensitization immunotherapy.
ACTIVITY: Bed rest until anaphylaxis clears and patient is stable
DIET: Nothing by mouth until acute symptoms are controlled
MEDICATIONS COMMONLY PRESCRIBED DRUGS: • Epinephrine
• Antihistamine: diphenhydramine
• Cimetidine
• Corticosteroids
• Bronchodilators: inhaled beta-2 agonists, aminophylline
CONTRAINDICATIONS: Read drug product information.
PRECAUTIONS: Read drug product information.
DRUG INTERACTIONS: N/A
Other Drugs: N/A
FOLLOW UP PATIENT MONITORING: The person with acute anaphylaxis should be followed closely during treatment and for several hours after symptoms resolve. Symptoms can recur for up to 72 hours.
PREVENTION/AVOIDANCE: • Avoid drugs, foods that trigger allergic reaction.
• Carry a prefilled epinephrine syringe (bee sting kit); avoid areas where insect exposure is likely. Avoid wearing things that attract insects (e.g., perfumes, bright-colored clothing).
• Carry/wear medical alert identification about anaphylaxis-causing substance or event.
COMPLICATIONS: • Epinephrine
• Antihistamine: diphenhydramine
• Cimetidine
• Corticosteroids
• Bronchodilators: inhaled beta-2 agonists, aminophylline
WHAT TO EXPECT: • Anaphylaxis has a good outcome if treated immediately.
• The outcome is worse if medical care is delayed more than 30 minutes.
• Of individuals with anaphylaxis of unknown cause, 60% will not experience another episode after 2.5 years; most others have a decrease in the number of episodes.
• Allergy to one species of legume (e.g., peanuts) or one type of seafood (e.g., shrimp) does not mean that an allergy to all products in that category exists.
MISCELLANEOUS OTHER FACTORS: N/A
PEDIATRIC: N/A
GERIATRIC: Epinephrine may induce cardiac events in those with heart disease.
OTHERS: N/A
PREGNANCY: Epinephrine may induce blood flow to placenta, but may save life of mother and fetus.
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