Sunday, December 7, 2014

A lady is contemplating a trekking trip to Nepal at elevations between 2500 and 3000 m.

A lady is contemplating a trekking trip to Nepal at elevations between 2500 and 3000 m.
trekking Nepal

Five years ago, while skiing at Telluride (altitude, 2650 m), she recalls having headache, nausea, and fatigue within 1 day of arriving that lasted about 2–3 days.

All of the following are true regarding the development of acute mountain sickness in this patient EXCEPT:

A. Acetazolamide starting 1 day before ascent is effective in decreasing the risk.
B. Gingko biloba is not effective in decreasing the risk.
C. Gradual ascent is protective.
D. Her prior episode increases her risk for this trip.
E. Improved physical conditioning before the trip decreases the risk.

The answer is E. Whereas acute mountain sickness (AMS) is the benign form of altitude illness, high-altitude cerebral edema (HACE) and high-altitude pulmonary edema (HAPE) are life threatening. Altitude illness is likely to occur above 2500 m but has been documented even at 1500–2500 m. The acclimation to altitude includes hyperventilation in response to the reduced inspired PO2 initially followed by increased erythropoietin and 2,3-bisphosphoglycerate.

AMS is characterized by nonspecific symptoms (headache, nausea, fatigue, and dizziness) with a paucity of physical findings developing 6–12 hours after ascent to a high altitude. AMS must be distinguished from exhaustion, dehydration, hypothermia, alcoholic hangover, and hyponatremia.

The most important risk factors for the development of altitude illness are the rate of ascent and a history of high-altitude illness. Exertion is a risk factor, but lack of physical fitness is not. One protective factor in AMS is high-altitude exposure during the preceding 2 months. Children
and adults seem to be equally affected, but people greater than 50 years of age may be less
likely to develop AMS than younger people. Most studies reveal no gender difference in
AMS incidence.

Sleep desaturation—a common phenomenon at high altitude—is associated
with AMS. Gradual ascent is the best approach to prevent AMS. Acetazolamide or
dexamethasone beginning 1 day before ascent and continuing for 2–3 days is effective if
rapid ascent is necessary. A double-blind placebo-controlled trial demonstrated no benefit
on AMS from gingko biloba. Mild cases of AMS can be treated with rest; more serious
cases are treated with acetazolamide and oxygen.

Descent is therapeutic in all serious cases, including HACE and HAPE. Patients who have recovered from mild cases of AMS may reascend carefully after recovery; patients with HACE should not.


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