Caracteristicas Y Propiedades Fisicas De Los Metales

Part 10.6: Anaphylaxis
naphylaxis is a severe, systemic allergic reaction characterized by multisystem involvement, including the skin, airway, vascular system, and gastrointestinal tract. Severe cases may result in complete obstruction of the airway, cardiovascular collapse, and death. The term classic anaphylaxis refers to hypersensitivity reactions mediated by the subclass of antibodiesimmunoglobulins IgE and IgG. Prior sensitization to an allergen has occurred, producing antigen-specific immunoglobulins. Subsequent reexposure to the allergen provokes the anaphylactic reaction. Many anaphylactic reactions, however, occur without a documented prior exposure. Anaphylactoid or pseudoanaphylactic reactions display a similar clinical syndrome, but they are not immune-mediated. Treatmentfor the two conditions is similar.

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fatal reaction occurs within 10 to 15 minutes. Cardiovascular collapse is the most common mechanism.3–5 Foods. Peanuts, tree-grown nuts, seafood, and wheat are the foods most frequently associated with life-threatening anaphylaxis.6 Bronchospasm and asphyxia are the most frequent mechanisms.3–5

Signs and Symptoms
Consider anaphylaxis when responsesfrom 2 or more body systems (cutaneous, respiratory, cardiovascular, neurologic, or gastrointestinal) are noted; the cardiovascular and respiratory systems may not be involved. The shorter the interval between exposure and reaction, the more likely the reaction is to be severe. Signs and symptoms include the following:
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Pathophysiology
The inciting allergen binds to antigen-specific IgE thathas accumulated on previously sensitized basophils and mast cells. These cells almost immediately release a series of mediators, including histamines, leukotrienes, prostaglandins, thromboxanes, and bradykinins. When released locally and systemically, these mediators cause increased mucous membrane secretions, increased capillary permeability and leak, and markedly reduced smooth muscle tone inblood vessels (vasodilation) and bronchioles.
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Etiology
Any antigen capable of activating IgE can be a trigger for anaphylaxis. In terms of etiology, researchers generally list the following categories of causes: pharmacologic agents, latex, stinging insects, and foods. In up to 5% of cases the antigenic agent cannot be identified. Pharmacologic agents. Antibiotics (especially parenteralpenicillins and other -lactams), aspirin and nonsteroidal anti-inflammatory drugs, and intravenous (IV) contrast agents are the most frequent medications associated with life-threatening anaphylaxis. Latex. Much attention has focused on latex-induced anaphylaxis, but it is actually quite rare.1,2 A decade-long registry of anaphylactic deaths in England has not registered any latex-associateddeaths.3,4 Stinging insects. Fatal anaphylaxis has long been associated with stings from hymenoptera (membrane-winged insects), including ants, bees, hornets, wasps, and yellow jackets. Fatal anaphylaxis can develop when a person with IgE antibodies induced by a previous sting is stung again. A
(Circulation. 2005;000:IV-143-IV-145.) © 2005 American Heart Association. This special supplement toCirculation is freely available at http://www.circulationaha.org DOI: 10.1161/CIRCULATIONAHA.105.166568

Serious upper airway (laryngeal) edema, lower airway edema (asthma), or both may develop, causing stridor and wheezing. Rhinitis is often an early sign of respiratory involvement. Cardiovascular collapse is the most common periarrest manifestation. Vasodilation produces a relative hypovolemia.Increased capillary permeability contributes to further intravascular volume loss. The patient may be agitated or anxious and may appear either flushed or pale. Additional cardiac dysfunction may result from underlying disease or the development of myocardial ischemia from administration of epinephrine.3–5 Gastrointestinal signs and symptoms of anaphylaxis include abdominal pain, vomiting, and...