Wilderness and Rescue Medicine 8th Edition

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Wilderness and Rescue Medicine

confused early in the pattern of shock or respira- tory failure. The severity of the signs and symp- toms correlates well to the severity of the problem. Picture the brain like the layers of an onion with increasingly complex layers of function from the inside out. The basic physiological functions that control consciousness and heart and respiratory rates extend from the innermost layers in the brain stem. Higher brain functions such as speech, behavior, judgment, and problem solving are controlled by the outer layers of the brain. These outer layers are usually the first to be affected by a developing problem with oxygenation and perfu- sion, causing changes in mental status.

Swelling and Pressure Swelling is a common, generic response to injury and illness. Swelling can interfere with oxygen- ation and perfusion. Many of our emergency drugs and procedures are used to prevent and control swelling or reduce the associated prob- lems and risks. Swelling is caused by the accumulation of excess fluid in body tissues. It can develop quickly as blood escapes from ruptured arteries or slowly as serum oozes from damaged or inflamed capil- laries , causing the condition known as edema . It may be localized, such as the swelling of a sprained ankle, or systemic , such as the swelling of the whole body that occurs in allergic reactions. Swelling is bothersome when it causes pain, and dangerous when it causes problems with oxygen- ation and perfusion. Swelling that develops inside a restricted space, such as the skull or a muscle compartment, can result in enough pressure to restrict perfusion causing the condition known as ischemia . This is exactly what happens to the brain with the development of increased intra- cranial pressure due to head injury. It is also responsible for the damage caused by compart- ment syndrome that develops in the muscles of the lower leg or forearm. Swelling in the confined space of the upper airway can cause obstruction, whereas swelling lower in the respiratory system can cause lower airway constriction or fluid in the alveoli. Swelling can evolve over hours or days, or nearly instantly with severe internal bleeding.

General Principles

Mental Status And Level of Consciousness

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AVPU: A – Awake (describe mental status – oriented, confused, anxious, combative, lethargic, etc.) V – Verbal P – Pain U – Unresponsive

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“… a reliable and accessible field measurement of perfusion and oxygenation.”

© 2018 WMA

As critical system problems become more seri- ous, mental status worsens and the deeper layers of the brain begin to fail, causing a decrease in the level of consciousness. Students sometimes refer to this pattern as “peeling the onion.”The progres- sion can be reversed if the underlying problems are corrected. In the absence of shock or respiratory failure, changes in mental status can indicate a problem within the brain itself such as intoxication , infec- tion , or stroke . Again, the severity of the symp- toms correlates well to the severity of the problem. Being a little tipsy after a beer is not serious, but being unconscious after a night of drinking is. If the deeper layers of the onion stop working, the patient will stop breathing. Monitoring con- sciousness and mental status offers a reliable and accessible field measurement of the quality of oxygenation and perfusion.

General Principles

Swelling and Pressure

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Bleeding and Edema

Swelling

Pressure

Ischemia

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“Anticipating and controlling swelling is an essential part of emergency medical care.”

© 2019 WMA