Wilderness and Rescue Medicine 7th Edition Jeffrey Isaac, PA-C and David E. Johnson, MD

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Section I: General Principles

Obstruction to Infection The human body is full of hollow organs that store, transport, or excrete liquids of all types. These include sweat glands, intestines, bladder, and all the associated ducts. If the drainage from these organs is obstructed by swelling, deformity, or a foreign body, the accumulation and pressure causes inflammation and pain. If the obstruction lasts long enough, any bac- teria present can begin to grow out of control in whatever substance is trapped, and infection will develop. The most common example is the aver- age pimple. This is an infection in an obstructed sweat gland. Appendicitis is a more serious example of the same pattern. Many illnesses have their origins in obstruction, and their cures are in relieving it. Wounds also create cavities prone to obstruction and infection. Closing a wound with stables or sutures will obstruct drainage, which is part of the natural healing process. Infection becomes more likely, especially in wounds treated in less than ideal conditions. Ischemia to Infarction Ischemia is a localized problem of inadequate tissue perfusion, as opposed to the whole body problem with perfusion called shock. Blood flow is blocked by a clot, deformity, or swelling causing symptoms including pain, numbness and tingling, and impaired function. The chest pain of a heart attack, for example, is caused by ischemia of the heart muscle. Numbness of the hand, for example, can be caused by the deformity of a dislocated shoulder. Prolonged ischemia inevitably leads to infarc- tion, which is the term for tissue death. Some tissue, such as the brain, can die from just a few minutes of ischemia. The skin, however, can live for hours without adequate perfusion. Essentially, the more important an organ is to immediate survival, the more sensitive it is to the loss of perfusion.

General Principles

Ischemia to Infarction

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“Ischemia that you cannot fix will lead to infarction.”

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Ischemia can be complete or partial. It can develop from an internal problem such as a blood clot or compartment syndrome, or from exter- nal pressure such as a tight splint or lying on an unpadded backboard. The symptoms of ischemia are an early warning of the serious and permanent

problems caused by infarction. Anticipated Problem

Ischemia is just one example of a serious problem that can become an emergency if it cannot be fixed. A dislocated shoulder, for example, causes ischemia of tendons and muscle and represents a limb threatening problem. Fortunately, field reduction is often successful, avoiding any need for an urgent evacuation. The pattern of respiratory distress to respira- tory failure is another example of a serious pattern that will progress to an emergency if you can’t fix it. Other examples include compensated shock to decompensated shock; mild hypothermia to severe hypothermia; and local infection to sys- temic infection. Fortunately, you will learn how to fix or stabilize some of these serious problems, but it is equally important to know when you can’t. Recognizing the progression and gauging your ability to slow it down or reverse it, helps to simplify treatment and evacuation decisions and the sense of urgency surrounding them.