High Altitude Sickness

Aka: High Altitude Sickness, Acute Mountain Sickness

II. Epidemiology: Prevalence

  1. Colorado ski resort: 25% of travelers
  2. Himalayas: 50% of travelers

III. Background: Barometric Pressure

  1. Sea level: 760 mmHg
  2. Sante Fe, New Mexico (7200 feet or 2194 meters): 582 mmHg
  3. Risk of Altitude Sickness starts at (8200 feet or 2500 meters): 560 mmHg
  4. Ski altitude (10,000 feet or 3048 meters): 522 mmHg
  5. Kala Pattar (18,187 feet or 5543 meters) : 375 mmHg
  6. Mount Everest (29,035 feet or 8849 meters): 249 mmHg

IV. Pathophysiology: Mechanism

  1. Hypobaric Hypoxemia results in paradoxical and maladaptive fluid retention
    1. Contrast with non-affected persons at altitude who experience diuresis
  2. Changes at altitude that may exacerbate comorbid illness
    1. Low partial pressure of oxygen
    2. Increased sympathetic tone
      1. Pulmonary artery Vasoconstriction
      2. Increased systemic vascular resistance

V. Risk Factors

  1. Rapid ascent
  2. Significant physical exertion
  3. Prior history of altitude sickness
  4. Traveling from low altitude
  5. Younger age
    1. Aside from comorbidity, older adults may be less affected by altitude

VI. Symptoms

  1. Common Symptoms
    1. Headache
    2. Malaise
    3. Anorexia
  2. Other Symptoms
    1. Fatigue
    2. Nausea or Vomiting
    3. Insomnia
    4. Dyspnea
    5. Dyspnea on Exertion
    6. Dry cough
    7. Irritable
    8. Decreased Urine Output

VII. Course

  1. Onset: 6-12 hours following high altitude ascent

VIII. Diagnosis

  1. Headache and
  2. One or more of the following
    1. Fatigue or weakness
    2. Dizziness or light headedness
    3. Gastrointestinal distress (Nausea, Vomiting, Anorexia)
    4. Sleep disturbance

IX. Differential Diagnosis

  1. Viral illness
  2. Hangover
  3. Exhaustion
  4. Dehydration
  5. Hypothermia
  6. Hypoglycemia
  7. Hyponatremia
  8. Medication: Sedative or hypnotic
  9. Carbon Monoxide Poisoning (e.g. cooking in tent)

X. Management

  1. Very mild symptoms may resolve spontaneously with acclimitization
  2. Immediate descent (at least 1000 feet or 300 meters) is most critical for moderate to severe symptoms
  3. Other measures for moderate to severe symptoms where descent is not immediately possible
    1. Supplemental Oxygen
    2. Acetazolamide 250 mg orally twice daily
    3. Dexamethasone 4 mg orally every 6 hours
    4. Gamow Bag (Portable Hyperbaric Chamber)
  4. Other measures
    1. Antiemetics (e.g. Zofran) for Nausea, Vomiting
    2. Acetaminophen or Ibuprofen for Headache

XI. Complications (0.1 to 4 percent Incidence)

  1. See Pathophysiology above
  2. Altitudes above 11,400 feet (3500 meters) are associated with a more complicated course
  3. High Altitude Pulmonary Edema (HAPE)
  4. High Altitude Cerebral Edema (HACE)

XII. Prevention

  1. Medication Prophylaxis
    1. Indications
      1. Travel to 11,000 feet in one day (or over 9,000 feet if history of prior altitude sickness)
    2. Acetazolamide (Diamox) 125 mg twice daily (FDA approved)
      1. Start 1 day or more before ascent
      2. Continue until acclimitization to the higheest sleeping altitude
      3. Up to 250 mg twice daily may be used (but 125 mg is typically sufficient)
    3. Dexamethasone 4 mg orally every 6-12 hours (not FDA approved)
      1. Alternative, in those who cannot take Acetazolamide
      2. Risk of rebound mountain sickness when discontinued
      3. Does not speed acclimitization, but does reduce symptoms
  2. General Pointers
    1. Recognize the symptoms of Acute Mountain Sickness
    2. Never ascend to sleep higher if you have symptoms
    3. Descend if symptoms do not resolve or worsen
    4. Never leave a person with altitude sickness alone
    5. Maintain hydration
    6. Avoid overexertion
    7. Avoid Alcohol and Sedatives
    8. For altitudes above 9800 feet
      1. Do not sleep >2000 feet (600 meters) higher than the night before
      2. Spend an additional day if ascent over 2000 feet
  3. Comorbid Conditions
    1. See Air Travel Restriction
    2. Patients with asymptomatic cardiopulmonary disease may ascend safely to at least 8200 feet (2500 meters)
    3. Conditions which absolutely contraindicate high altitude travel
      1. Severe Chronic Obstructive Pulmonary Disease (COPD)
      2. Uncontrolled Congestive Heart Failure (CHF)
    4. Conditions for which caution should be Exercised due to risk of exascerbation (emphasize acclimitization)
      1. Arrhythmias
      2. Coronary Artery Disease
      3. Hypertension
      4. Sickle Cell Anemia (splenic infarct risk increases above 4900 feet (1500 meters)
        1. Keep Supplemental Oxygen available

XIII. References

  1. (2018) Presc Lett 25(2)
  2. Candy and Contant in Herbert (2020) EM:Rap 20(3): 3-4
  3. Basnyat (2003) Lancet 361(9373): 1967-74 [PubMed]
  4. Fiore (2010) Am Fam Physician 82(9): 1103-10 [PubMed]
  5. Hackett (2001) N Engl J Med 345(2): 107-14 [PubMed]

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Related Studies

Ontology: Altitude Sickness (C0002351)

Definition (MSH) A morbid condition of ANOXIA caused by the reduced available oxygen at high altitudes.
Concepts Disease or Syndrome (T047)
MSH D000532
ICD10 T70.29
SnomedCT 157733006, 212948000, 212949008, 212950008, 212947005, 87284002, 42883007
English Altitude Sickness, Altitude Sicknesses, Sicknesses, Altitude, Altitude sickness, Sickness, Altitude, Hypobaropathy NOS, Illnesses-high altitude effect, hypobaric sickness, mountain sickness, mountain sickness (diagnosis), Mountain Sickness, Mountain Sicknesses, Sickness, Mountain, Sicknesses, Mountain, Altitude Sickness [Disease/Finding], Adverse effect;altitude, altitude sickness, effects of high altitude, high altitute sickness, altitude effects high, high altitude effects, Mountain sickness (disorder), Hypobaropathy NOS (disorder), Hypobaropathy, Mountain sickness, Alpine sickness, Anoxia due to high altitude, Illnesses due to high altitude effects, Effects of high altitude (disorder), Effects of high altitude, Anoxia due to high altitude (disorder), hypobaropathy, disease (or disorder); alpine, disease (or disorder); mountain sickness, effects of; high altitude, high altitude; effects, alpine sickness, Effects of high altitude, NOS, Mountain sickness [Ambiguous], Andes disease
Swedish Höjdsjuka
Czech výšková nemoc
Finnish Korkeustauti
Russian VYSOTNAIA BOLEZN', ВЫСОТНАЯ БОЛЕЗНЬ
Japanese 高山病, 山岳病, 高所病
Italian Male dell’altitudine, Mal di montagna
Polish Choroba wysokościowa
Norwegian AMS, Høydesyke
Spanish hipobaropatía, SAI, hipobaropatía, SAI (trastorno), Mal de las Alturas, Enfermedad de la Altura, anoxia secundaria a la altura (trastorno), anoxia secundaria a la altura, efectos de la altura (trastorno), efectos de la altura, enfermedad alpina, enfermedad de la montaña, hipobaropatía, Enfermedad de la Montaña, Mal de Altura
Dutch aandoening; Alpen, aandoening; bergziekte, gevolg; grote hoogte, grote hoogte; gevolgen, Hoogteziekte, Ziekte, hoogte-
French Mal de l'altitude, Mal des montagnes, Maladie de l'altitude
German Bergkrankheit, Höhenkrankheit
Portuguese Doença da Altitude, Doença das Montanhas
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Acute mountain sickness (C0238284)

Concepts Disease or Syndrome (T047)
SnomedCT 78590007
Italian Mal di montagna acuto
Dutch acute hoogteziekte, hoogteziekte acuut
German akute Bergkrankheit, Bergkrankheit akut
Portuguese Doença aguda das montanhas, Mal das montanhas agudo
Spanish Mal agudo de las grandes alturas, enfermedad aguda de la montaña, apunamiento, enfermedad aguda de la montaña (trastorno), enfermedad de Acosta, mal de las montañas (trastorno), mal de las montañas, soroche, Mal de montaña agudo
Japanese 急性高山病, ｷｭｳｾｲｺｳｻﾞﾝﾋﾞｮｳ
English Mountain sickness acute, acute mountain sickness, Acosta's disease, Acute mountain sickness, Soroche, Acute mountain sickness (disorder)
Czech Akutní horská nemoc
Hungarian Acut hegyi betegség, Akut hegyibetegség
French Mal des montagnes aigu
Derived from the NIH UMLS (Unified Medical Language System)

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