Anaphylaxis

Basics

Description

  • An acute, widely distributed form of shock that occurs within minutes of exposure to antigen in a sensitized individual
  • The overall rate of anaphylaxis appears to be increasing, especially in children
  • An overall incidence rate of about 50 per 100,000 person-years is estimated from current data:
    • Fortunately, case fatality rates are low for patients who make it to the ED (0.1–0.3%)
  • Involves release of bioactive molecules such as histamine, leukotrienes, and prostaglandins from inflammatory cells:
    • Mediator release results in increased vascular permeability, vasodilation, smooth-muscle contractions, and increased epithelial secretion
    • Physiologically, this is manifested in a decrease in total peripheral resistance, venous return, and cardiac output, as well as intravascular volume depletion

Etiology

  • IgE mediated:
    • Antibiotics, particularly penicillin family
    • Venoms, esp bee and wasp
    • Latex
    • Vaccines
    • Foodstuffs (shellfish, soybeans, peanuts, tree nuts, wheat, milk, eggs)
    • Monoclonal antibody therapeutics
  • Non-IgE mediated:
    • Iodine contrast media
    • Opiates
    • Vancomycin:
      • Usually can be prevented by reducing rate of infusion
    • Seminal fluid
    • Exercise

Pediatric Considerations
In children, foods are an important trigger for IgE-mediated anaphylaxis:
  • The most common foods to cause anaphylactic events are peanuts, tree nuts, fish, shellfish, milk, and egg, but any food can produce a reaction

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