الفهرس 
Etiology and pathophysiology of anaphylaxisOnly 14 pages are availabe for public view
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Abstract
Anaphylaxis is an acute, potentially lethal, multi-system syndrome resulting from the sudden release of mast cell-, basophil-, and macrophage-derived mediators into the circulation.
Anaphylaxis can be classified as ”immunologic” or ”non-immunologic”. Immunologic anaphylaxis includes both IgE-mediated and IgG-mediated reactions, as well as immune complex/complement-mediated mechanisms. Non-immunologic anaphylaxis is caused by agents or events that induce sudden, massive mast cell or basophil degranulation, without the involvement of antibodies.
In humans, the predominant shock organs are the heart, lung, and vasculature. Fatalities are divided between circulatory collapse and respiratory arrest. Anaphylaxis is associated with myocardial depression, arrhythmias, and myocardial ischemia. Anaphylaxis may affect any part of the respiratory tract, causing bronchospasm and mucus plugging in the smaller airways, and laryngeal edema and asphyxiation in the upper airway.
Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death. There are three clinical criteria for the diagnosis of anaphylaxis, which reflect the different ways in which anaphylaxis may present. Anaphylaxis is highly likely when any ONE of the three criteria is fulfilled (criterion 1: acute onset of an illness (minutes to several hours) involving the skin, mucus membranes, or both and at least one of the following; respiratory compromise or reduced blood pressure — criterion 2: two or more of the following occurring rapidly (minutes to several hours) after exposure to a likely allergen for that patient; involvement of the skin, mucus membranes, or both – respiratory compromise – reduced blood pressure – persistent gastrointestinal symptoms and signs — criterion 3: reduced blood pressure after exposure to a known allergen for that patient).
Recognition is not always easy, because anaphylaxis can mimic many other disorders and can be variable in its presentation. Anaphylaxis may present with various combinations of as many as 40 potential symptoms and signs. Common disorders that mimic anaphylaxis include acute generalized urticaria, acute angioedema, acute asthma, syncope, and panic attacks or acute anxiety attacks.
Patients and healthcare professionals commonly fail to recognize and diagnose anaphylaxis in its early stages, when it is most responsive to treatment. In particular, there is a reluctance to diagnose anaphylaxis in the absence of hypotension, even though this sign is not required for the
diagnosis and occurs late or not at all.
Prompt recognition and treatment are critical in anaphylaxis. In fatal anaphylaxis, median times to cardiorespiratory arrest are 5 minutes in iatrogenic anaphylaxis, 15 minutes in stinging insect venom-induced
anaphylaxis, and 30 minutes in food-induced anaphylaxis. The amount of allergen is usually unremarkable (e.g., variable amounts of food, one insect sting, a normal dose of medication). Fatal anaphylaxis is unpredictable, although certain patients are at higher risk, such as those with concomitant asthma or cardiopulmonary disease.
The clinical diagnosis of anaphylaxis may or may not be confirmed by measurement of elevated concentrations of plasma histamine or serum or plasma total tryptase.
Epinephrine is life-saving in anaphylaxis. It should be injected as early as possible in the episode in order to prevent progression of symptoms and signs. There are no absolute contraindications to its use, and it is the treatment of choice for anaphylaxis of any severity.
The route of epinephrine administration depends upon the presenting symptoms. For patients who are not profoundly hypotensive, or in shock, or cardio-respiratory arrest, intramuscular injection into the mid-outer thigh as the initial route of administration is advised in preference to subcutaneous administration. Intravenous epinephrine is indicated for patients with profound hypotension, or symptoms and signs suggestive of impending shock, or those who do not respond to an initial intramuscular injection of epinephrine and fluid resuscitation. For these patients epinephrine is suggested to be administered by continuous slow intravenous infusion rather than by intermittent IV bolus.
Massive fluid shifts can occur in anaphylaxis, and all patients with orthostasis, hypotension, or incomplete response to epinephrine should receive large volume fluid resuscitation with normal saline. Normotensive patients should receive normal saline to maintain venous access in case their status deteriorates.
characteristics of unsuccessful treatment include delayed or no administration of epinephrine. Maintaining the patient in an upright position after collapse can lead to pulseless electrical activity and cardiac arrest (empty ventricle syndrome). Occasionally, victims succumb despite receiving prompt and appropriate treatment.
Patients successfully treated for anaphylaxis should be discharged with a personalized written anaphylaxis emergency action plan, an epinephrine autoinjector, written information about anaphylaxis and its treatment, and a plan for further evaluation.