Wilderness and Rescue Medicine 8th Edition

Chapter 8: Allergy and Anaphylaxis

The severe systemic allergic reaction known as anaphylaxis causes serious critical system prob- lems that require immediate treatment in the field. The medications used are an important part of your basic life support (BLS)/advanced life sup- port (ALS) tool kit. The emergency treatment for anaphylaxis should be memorized and rehearsed. This is a problem that will not wait for you to look it up in a book, or for an ambulance or helicopter to arrive.

Allergy Allergy is an abnormally vigorous formof immune response resulting in the release of the chemical histamine and other inflammatory mediators into blood and body tissues from white blood cells called mast cells. These white blood cells are responding to signals from antibodies that have attached themselves to a foreign molecule, bac- teria, or other allergen marking it for destruction. The histamine and other chemicals mediate vasodilation and bronchoconstriction , caus- ing swelling and lower airway constriction. These effects can be mild or severe, local or systemic. Onset can be nearly instantaneous or delayed by several hours. When the response remains localized to the area of antigen contact, it is called a local allergic reac- tion. The patient experiences localized vasodila- tion. This allows fluid to leak from capillaries into the extracellular space causing localized swelling and itching. Hay fever is an example of a local reaction affecting the mucous membranes of the nose and eyes. These effects explain the familiar symptoms: swollen mucous membranes, itchy eyes, and a runny nose.

General Principles

Allergy and Anaphylaxis

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Mechanism: • Antigen injected, ingested, inhaled, or absorbed • Antibody produced by the immune system marking the antigen for destruction by white blood cells • Histamine and other inflammatory chemicals released by white blood cells (mast cells) during the process

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Allergy and inflammation is a complicated process involving several chemical mediators and body responses. The actions of drugs used to treat it are equally complex and sometimes not well understood. Fortunately, a basic understand- ing of the important points is sufficient for field purposes.