Wilderness and Rescue Medicine 8th Edition

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Wilderness and Rescue Medicine

setting, oxygen is usually administered by nasal canula at a rate just adequate to reduce symptoms and maintain oxygenation of the brain. A flow rate as low as 0.25 liters per minute can make a dif- ference. Improved mental status and an increased oxygen saturation are a good indication of success. High-flow oxygen by mask is rarely necessary and may result in depletion of the supply before the mission is over. Vascular Shock With the loss of muscle tone in the arteries or the inflammation and dilation of capillaries due to injury or illness, the pressure exerted on the blood volume drops. The pattern of vital sign changes as the body compensates will include the typical increase in pulse and respiratory rate and reduc- tion in urine output. However, you may not see shell/core compensation as you do in volume shock because the blood vessels in the skin may be unable to constrict normally. This is where the appearance of vascular shock might differ from that of volume shock. Vascular shock is most commonly seen in the severe, systemic allergic reaction called anaphy- laxis. It can also be part of a syndrome caused by systemic infection (septic shock) or due to the loss of nervous system control in severe spinal cord injury. The result is the same: inadequate perfu- sion pressure in the circulatory system resulting in inadequate cellular oxygenation. Field Treatment of Vascular Shock Field treatment for vascular shock includes keep- ing the patient horizontal because the ability to compensate for the effects of gravity is impaired. Treat the cause if possible. Anaphylaxis, for exam- ple, can be reversed with injectable epinephrine (see the Allergy and Anaphylaxis chapter). If vaso- dilatation is not reversible with field treatment, as in spinal cord injury or infection, evacuation and IV fluid to expand blood volume and maintain perfusion are indicated. ALS providers may also use vasoactive medications like norepinephrine to temporarily boost perfusion pressure pending definitive treatment.

An awake and responsive patient is a sign of adequate perfusion pressure and a good target for fluid resuscitation in the field. If you can measure blood pressure, work toward a systolic reading of 90–100 mmHg. As with volume shock, hypother- mia is an anticipated problem in the wilderness setting.

General Principles

Vascular Shock Treatment Reverse vasodilation: • Medications for anaphylaxis • Vasoconstrictors and antibiotics for infection Increase fluid volume: • IV blood or electrolyte solutions • Oral electrolyte solutions or water and food

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PROP and Evacuation as Needed

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Cardiogenic Shock Cardiogenic shock is most often caused by myo- cardial infarction or cardiac dysrhythmia (i.e., heart attack), resulting in reduced cardiac output. Symptoms include chest pain or pressure accom- panied by the signs and symptoms of shock. The pattern of compensation will resemble that of volume shock, except that the heart rate may be very fast, slow, or irregular since abnormal heart function is the root of the problem. The symptoms of a heart attack may be very severe or quite subtle. Heart attack with the antici- pated problem of cardiogenic shock should be on your problem list whenever a patient complains of chest discomfort without an obvious mechanism of injury. This is especially true when the patient’s history includes several risk factors for coronary artery disease, such as smoking, obesity, hyperten- sion, or diabetes. Cardiogenic shock from trauma generally occurs when blood or fluid accumulates in the pericardial sack around the heart, inhibiting heart filling and reducing cardiac output. It can also develop because of poor function in a con- tused heart. It should be suspected or anticipated whenever a trauma patient complains of persis- tent chest pain. Cardiogenic shock from trauma