Wilderness and Rescue Medicine 8th Edition

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Section V: Environmental Medicine

medication, supplemental oxygen, and fluid to maintain hydration. For a short time under emer- gency circumstances a corticosteroid medication can be used to reduce the symptoms of cerebral edema. An example is the drug dexamethasone given by mouth or intramuscular injection.

General Principles

High - Altitude Cerebral Edema Mechanism: • C apillary dilation and leakage leading to increased ICP Signs and Symptoms: • Mild HACE (AMS) – mild headache, fatigue, nausea

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General Principles

Altitude Illness Prevention

• Moderate HACE – severe headache, vomiting

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• Severe HACE – brain failure (mental status changes, ataxia)

• Above 3 , 000 meters, ascend 300 – 1 , 000 meters per day • Rest days every 1 , 000 – 1 , 500 meters in ascent

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• Carry high, sleep low • Avoid CNS depressants • Stay hydrated and well fed • Be alert to early symptoms • Prophylactic medications

Treatment is largely symptomatic. Aspirin, ibu- profen, or other aspirin-like drugs reduce pain and may reduce cerebral edema. Hydration is important to kidney function, and the patient should avoid alcohol and narcotic medication that would depress respiratory drive. The prescription drug acetazolamide can be used to reduce symp- toms by maintaining a more normal blood pH.

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A portable hyperbaric chamber (e.g., Gamow bag) is another emergency treatment occasion- ally available through rescue teams or cached at popular climbing areas. This device can be used to increase the air pressure around the patient temporarily by about two pounds per square inch, simulating a descent of 1,000–2,000 meters. This may temporarily improve the patient’s condition, allowing a walk-out evacuation before debilitating symptoms return. The symptoms of moderate HACEmay improve with treatment and time. However, climbing part- ners or rescuers must be prepared for an emergen- cy descent if the patient’s condition worsens. The practitioner must also be alert to other anticipated problems such as hypothermia and volume shock from dehydration. Severe HACE is a serious critical system prob- lem. Fortunately, it rarely occurs below 4,000 meters in elevation. One of the common signs is ataxia (loss of muscle control, often seen as an inability to walk straight). The patient also exhib- its changes in level of consciousness and mental status that may range from mild to profound. Persistent vomiting and complete loss of appetite are common. The symptoms of severe HACE can be confused or mixed with those of other problems such as

HACE Medications

Acetazolamide (Diamox): • Prophylaxis 125mg q12h (5 mg/kg/day in 2 divided doses for kids)

• T reatment 250mg bid or tid Dexamethasone (Decadron):

• 8 mg loading dose, then 4 mg q 12 h for emergency treatment of moderate and severe sx (IM, SC or PO) • Prophylaxis for high altitude rescue teams Oxygen: • Titrate to patient response • 1 – 2 liters per minute may suffice

Ideally, a climber should not continue to ascend until symptoms have resolved. However, sched- ules often interfere with ideal prevention and treatment. Pushing through symptoms to a higher altitude or level of activity can make the situation much worse. Moderate HACE is increased ICP due to brain swelling. The patient shows early mental status changes and begins to vomit. The headache may not respond to NSAIDs. The ideal treatment is supplemental oxygen and an immediate descent of at least 300 meters. If the patient is trapped at altitude by weather or terrain, treatment in place includes rest, pain