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4.
Nifedipine: The prophylactic administration of nifedipine is effective in
lowering pulmonary artery pressure and preventing high-altitude pulmonary edema in
HAPE-susceptible individuals. The prophylactic dose of nifedipine is 30 or 60 mg
(extended release formation) per day to be taken during the ascent phase of the expedition
and for three additional days at altitude.
Possible side-effects include those of orthostatic hypotension, although the drug is
very well tolerated in persons with normal cardiovascular function. Consider the use of
this drug as an adjunct to the most important preventive measure, gradual ascent.
5. Inhaled salmeterol: Effective in increasing fluid clearance from alveoli and
preventing HAPE. The dose studied is 125 micrograms inhaled twice daily, which is two
to three times the recommended dose for asthma. Potential side effects are those of
systemic beta-agonist adrenergic stimulation and include anxiety, tachycardia, and
tremor. There is less experience with the use of inhaled salmeterol as compared to
nifedipine for prophylaxis of HAPE. Both drugs could be used simultaneously but both
are considered as adjuncts to gradual ascent.
F.
Sedatives and Hypnotics: Medications to aid sleep at high altitude include
acetazolamide and benzodiazepines. Acetazolamide has the advantage of aiding
acclimatization by causing a metabolic acidosis with compensatory
hyperventilation, thus augementing the normal increased ventilation and
respiratory alkalosis that occurs during acclimatization. Acetazolamide also has
the advantage of eliminating sleep period breathing (Cheyne-Stokes) which is
universal above about 13,000 feet. Benzodiazepines are effective sleeping
medications at high altitude in persons who are healthy, but may be harmful in
those who have high altitude illness because suppressing respirations may lead to
worse hypoxemia during sleep and acceleration of high altitude illness.
III. GUIDELINES FOR ASSESSMENT AND TREATMENT
Ascending too quickly and not allowing time for acclimatization increases susceptibility
to high altitude illness. Descent is a treatment for all forms of high altitude illness, and
may be lifesaving for HAPE or HACE (category 1A recommendation). Mild forms of
AMS, however, usually resolve spontaneously in two to four days if ascent is halted,
making descent unnecessary. There are few studies of treatment of AMS, and these
guidelines reflect expert opinion more than well-controlled research studies. Treatment is
based on four principles: 1) stop ascent in presence of symptoms (do not go up unless
symptoms go away), 2) descend if there is no improvement or condition worsens, 3)
descend immediately if symptoms of HAPE or HACE are present, and 4) ill persons must
not be left alone or sent down alone.
A. Acute Mountain Sickness: Individuals with AMS have headache and at least one other
symptom of anorexia, nausea, vomiting, dizziness, lightheadedness, disturbed sleep, or
lassitude. There are no characteristic physical findings. Basic treatment is to descend or
to stop ascent and wait for improvement before proceeding. Continuing ascent in the
presence of symptoms is ill advised. After stopping the ascent, more advanced treatment
