Anaphylaxis

– An immediate, acute, systemic reaction resulting from an IgE-mediated antigen-antibody response that can range from mild to life threatening.

Causes and Incidence

The most common causes are insect stings, drugs, blood products, and parenteral enzymes. Anaphylaxis occurs in both sexes and across all age groups and races. Individuals with known allergies or previous sensitivity reactions are at greater risk.

Disease Process

Histamine, leukotrienes, and other mediators are released when the antigen agent reacts with the IgE (antibody) on the basophils and mast cells. This causes smooth muscle contraction and vascular dilation. Vasodilation and escape of plasma into tissues causes urticaria and angioedema and a decrease in plasma volume, leading to shock. The escape of fluid from the alveoli causes pulmonary edema and angioedema. A prolonged reaction can produce cardiac arrhythmias and cardiogenic shock.

Symptoms

Mild
Queasiness, anxiety, hives, itching, flushing, sneezing, nasal congestion, runny nose, cough, conjunctivitis, abdominal cramps, tachycardia.

Moderate
Malaise; urticaria; periorbital edema; pulmonary congestion; hoarseness; edema of the tongue, larynx, and pharynx; dysphagia; bronchospasm; dyspnea; wheezing; nausea; vomiting; diarrhea; hypotension; syncope; confusion.

Severe
Cyanosis, pallor, stridor, occluded airway, hypoxia, respiratory arrest, cardiac arrhythmia, circulatory collapse, seizures, incontinence, coma, death.

Potential Complications

Lack of timely and appropriate treatment results in shock, cardiac and respiratory collapse, coma, and death.

Diagnostic Tests

Clinical evaluation
Rapid development of above signs and symptoms after exposure to a likely offending agent.

Complete blood count
Normal or elevated hematocrit.

Blood chemistry
Normal until circulatory collapse.

Radiology
Normal or hyperinflation; edema.

Electrocardiogram (ECG)
Normal until hypoxemia develops.

Treatments

Treatment centers around immediate and aggressive management of emerging symptoms. Maintaining the airway and blood pressure is critical.

Surgery – Tracheostomy.

Drugs
Epinephrine and other drugs to counteract effects of mediator release and to block further mediator release; vasopressors to maintain blood pressure.

General
Maintenance of airway, suctioning; monitoring of vital signs; monitoring of blood gases for acidosis; IV volume replacement; ECG monitoring for dysrhythmias; instruction in prophylaxis for those at risk.

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