Altitude Sickness

 

Adverse effects due to altitude can be seen at altitudes above 1,500 meters and are common above 2,500 meters.

(1) Rapid ascent without acclimatization can result in serious sickness.

(2) "Sleeping altitude" is an important consideration, as high altitude day travel with prompt return to low altitude is associated with a slow incidence of altitude sickness.

 

Disorders associated with high altitudes:

(1) acute mountain sickness: nausea, vomiting, headache (most common finding), fatigue, anorexia, dizziness and/or sleep disturbances

(2) high altitude cerebral edema

(3) high altitude pulmonary edema

 

Recommended rate of ascent to allow acclimatization:

(1) Nights should be spent no more than 300 meters above previous camp.

(2) If a camp is more than 300 meters above the previous, then subsequent camps should be located to keep the overall average ascent to less than 300 meters

(3) A day of rest should be interspersed every 2 or 3 days, or every 1000 meters of ascent.

(4) Some people may experience mountain sickness at this rate of ascent and should reduce the rate further.

(5) Others may be able to tolerate a more rapid rate of ascent.

 

Previous experience at high altitudes can serve as an imperfect guide to risk:

(1) Some people are more susceptible to altitude sickness than others, while others are more resistant.

(2) Variations in conditions or itinerary can make comparison between trips difficult.

 

Risk factors for altitude sickness:

(1) exertion

(2) presence of respiratory infection

(3) hypersensitive gag reflex

(4) extreme dizziness on hyperventilation

(5) short breath-holding time

 

Drug prophylaxis with acetazolamide, a carbonic anhydrate inhibitor:

(1) Therapy is begun 24 hours before ascents over 2500 meters.

(2) Regimens include 250 mg bid, or 500 mg qd with slow release formulation.

Syndrome	Treatment
mild	may respond to slowing or stopping ascent, analgesics and acetazolamide
moderate	require descent to lower altitude
severe	require oxygen, hyperbaric treatment and dexamethasone
pulmonary edema	additional medication, such as calcium channel antagonists