The Underlying Pathophysiologic Mechanisms of Anaphylactic Shock

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A Review of Causation, Presentation, and Treatment of Anaphylaxis in the Pre-Hospital Setting

This paper will explore the underlying pathophysiologic mechanisms of anaphylactic shock, how those mechanisms will affect the patient’s signs and symptoms, and what the EMT-B may do in the field to attempt reversing the effects of the body’s immune responses. Introduction Anaphylaxis is a life-threatening form of distributive shock that occurs when the body’s immune system reacts overwhelmingly and unjustifiably to an allergen.1 Anaphylaxis has a prevalence rate in the united states between 50 to 2000 episodes per 100,000 lifetimes, or as high as 2%.1 This paper will explore the underlying pathophysiologic mechanisms causing the
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On a second exposure, the IgE molecules cross-react to the allergen and cause the mast cells to dissolve, releasing histamine, leukotrienes, prostaglandins, and cytokines. As the allergen and antibodies enter the bloodstream, a cascade occurs causing an extensive reaction throughout the body. It is important to note that individuals do not experience symptoms during the initial sensitization process – the immune system “learns” the antigen so it may respond after the next exposure.2
The primary physiologic cause of anaphylactic shock is the body’s response to the histamine produced by the granulation of the mast cells. Histamine stimulates contraction of the smooth muscle in the respiratory tract, while simultaneously causing a relaxation in the smooth muscle of the circulatory system.3 As the blood vessels dilate, the amount of circulating blood becomes too small to fill the vessels. The vasodilation and overwhelming immune response additionally impact fluid availability as the antibodies trigger plasma to leave the circulatory space, causing widespread edema. This especially affects the respiratory system, further compounding the inability of the body to properly oxygenate tissue.3
Predicting the precise course of an allergic reaction is

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