Anaphylaxis

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

• The most common foods to cause anaphylactic events are peanuts, tree nuts, fish, shellfish, milk, and egg, but any food can produce a reaction