Anaphylactic, anaphylactoid, and related forms of shock.

Anaphylactic, anaphylactoid, and related forms of shock are true medical emergencies characterized by bronchial reactivity, airway edema, and hypovolemia. These reactions are attributed to the immunologic and nonimmunologic activation of mast cells and basophils, which results in the acute release of a variety of biochemical mediators that influence vascular tone and permeability. The therapeutic approach to these reactions is guided by the understanding of associated cellular and biochemical changes.