ENVIRONMENTAL EMERGENCIES■ Erythropoietin production is ↑within 2 hours of ascent →↑red cell mass
and↑O 2 carrying capacity.
■ ↑2,3-DPG→rightward shift of oxyhemoglobin dissociation curve →
improved O 2 release to tissues.
Acute Mountain Sickness
Develops several hours after arrival to altitude >8000 ft in nonacclimatized
individuals
SYMPTOMS/EXAM
■ Symptoms are similar to viral syndrome or hangover: Anorexia, headache,
nausea/vomiting, fatigue, weakness, insomnia.
TREATMENT
■ Usually self-limited and resolves with acclimatization in 24–48 hours.
■ No further ascent until symptoms abate
■ Descend if severe symptoms
■ Acetazolamide: To speed acclimatization (may start prior to ascent).
■ For symptomatic relief:
■ Supplemental O 2
■ Dexamethasone
■ Tylenol, aspirin
■ Avoid: All CNS and respiratory depressants (narcotics, alcohol, benzodi-
azepines).
High-Altitude Pulmonary Edema
HAPE is a form of noncardiogenic pulmonary edema. It typically occurs
2–4 days after arrival to high altitude.
PATHOPHYSIOLOGY
Pulmonary vasoconstriction →↑pulmonary hypertension → endothelial
damage and capillary leak.
TABLE 13.10. Altitude Classification and Pathophysiology
CLASSIFICATION ELEVATIONATTAINED(ft) PATHOPHYSIOLOGYModerate altitude 8000–10,000 ↓exercise performance
↑ventilation to ↑PO 2High altitude 10,000–18,000 Maximal SaO 2 < 90%
Maximal PaO 2 < 60 mmHg
HypoxemiaExtreme altitude > 18,000 Severe hypoxemia
Severe hypocapnia
Physiologic deterioration with timeBest prevention for all types of
high-altitude illness:
■Ascend slowly and spend
time at each altitude for
acclimatization.
■Avoid alcohol and other
sedatives.
■Avoid overexertion.
■Keep warm.The best definitive treatment
for all high-altitude
syndromes is immediate
descent.