Pediatric emergency medicine trisk 1672 1672
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platelet-activating factor (PAF), heparin, tryptase, and chymase. Although
elevated PAF, a proinflammatory phospholipid, and other mediators have been
associated with severe anaphylactic reactions, routine measurement is not
incorporated into clinical practice.
Nonimmunologic (i.e., non–IgE-mediated) anaphylaxis is caused by direct
stimulation of mast cells and basophils, which may occur after infusion of
hyperosmolar solutions (e.g., mannitol and radiocontrast media). Other potential
etiologies include ingestion of aspirin and other NSAIDs, or, after vigorous
exercise which may be preceded by ingestion of an allergenic food such as wheat
or shellfish. This is sometimes referred to as food-associated exercise-induced
anaphylaxis.
Clinical Considerations
Clinical Recognition
Although most symptoms develop within 30 minutes of allergen exposure, some
reactions may occur hours after the initial exposure. Anaphylaxis is a clinical
diagnosis and is highly likely when any one of the following three criteria are
fulfilled: (1) Sudden onset of skin (e.g., urticaria, periorbital erythema, pruritus,
flushing) and/or mucous membrane (e.g., oral/uvula swelling) changes in
combination with either (a) acute respiratory symptoms (e.g., wheezing, stridor,
or hypoxia) or (b) hypotension or signs of end organ dysfunction (e.g.,
syncope/incontinence); (2) sudden involvement of at least two organ systems
after exposure to a likely allergen (skin/mucosal, GI, respiratory, cardiovascular);
or (3) age-specific hypotension (or >30% decline in systolic blood pressure) after
exposure to a known allergen.
Among children with anaphylaxis, skin manifestations are usually, but not
uniformly present. Gastrointestinal symptoms are common and may include
nausea, vomiting, diarrhea, and abdominal pain. Mucosal involvement may
include lip and tongue swelling which could impair swallowing and ventilation.
Patients with mild upper airway edema may begin with throat discomfort or
pruritus which can progress to life-threatening upper airway obstruction with
stridor and respiratory distress. Similar to acute asthma exacerbations, children
with anaphylaxis may have bronchospasm and present with chest tightness,
cough, dyspnea, wheezing, and retractions.
Although hypotension is rare among patients with anaphylaxis (1% to 5%),
children with hypotension or wide pulse pressure may be at increased risk of
severe and biphasic reactions. Children may present in hypotensive shock,
develop life-threatening arrhythmias, or have electrocardiographic evidence of
