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| Altitude Sickness / Acute Mountain Sickness
Altitude Sickness, also known as Acute Mountain Sickness (AMS), is a condition that can affect individuals who ascend to high altitudes, typically above 8,000 feet (2,500 meters), too quickly. Complications include acute mountain sickness, high altitude pulmonary oedema, and high-altitude cerebral oedema. Management involves stopping ascent, allowing time for acclimatization, rest, and hydration.
About
- Occurs with rapid ascent to high altitudes above 2,500 meters.
- Increasing altitude leads to hypoxia and pulmonary vasoconstriction.
- Results in hypocarbia and alkalosis.
- Severe cases can develop into pulmonary and cerebral oedema.
Geography
- Ben Nevis, UK: 1,345 meters (Not typically seen)
- Matterhorn: 4,478 meters
- Mont Blanc: 4,807 meters
- Kilimanjaro: 5,895 meters
- Everest: 8,848 meters
Aetiology
- The physiological process underlying altitude sickness is an exaggerated vascular response to hypoxia.
- Acclimatization allows the body to make physiological adjustments at both the molecular and cellular levels.
Severity Factors
- Rate of ascent
- Height above sea level
- Length of stay at altitude
- Physical exertion at altitude
Risk Factors
- Rapid ascent and lack of acclimatization
- Altitude above 8,000 feet (2,500 meters)
- Dehydration and hypothermia
- High alcohol intake
- Excessive physical exertion in the first few days at altitude
- Previous history of anemia, altitude sickness, or pulmonary/cardiac conditions
Pathology
- Pulmonary oedema
- Protein-rich exudate and alveolar hemorrhages
- Alveolar hyaline hemorrhage
- Cerebral oedema
Types of Altitude Sickness
- High Altitude Pulmonary Oedema (HAPE): Fluid accumulates in the lungs, causing extreme breathlessness, coughing (sometimes with pink, frothy sputum), and cyanosis (bluish skin).
- High Altitude Cerebral Oedema (HACE): Swelling of the brain, leading to confusion, loss of coordination, and potentially coma.
Clinical Symptoms
- Acute Mountain Sickness: Can range from mild to severe.
- Headaches, nausea, vomiting, loss of appetite
- Insomnia, dizziness, confusion
- Fatigue, weakness, heavy legs
- Swelling of hands and face
- Breathlessness and irregular breathing
- Reduced urine output
- High Altitude Pulmonary Oedema (HAPE):
- Breathlessness, cough, haemoptysis, wheezing
- Tachycardia, hypotension, cyanosis
- Bilateral basal crackles on lung examination
- High Altitude Cerebral Oedema (HACE):
- Severe headache, confusion, ataxia
- Irritability, delirium, coma, seizures
- High Altitude Retinal Haemorrhage: Altered vision due to retinal bleeding.
Investigations
- FBC: Elevated haematocrit and hemoglobin
- ABG: Low oxygen levels (O₂) and low PCO₂
- ECG: Sinus tachycardia
- Chest X-ray (CXR): May show pulmonary oedema
Management
- Avoidance:
- First night sleeping altitude should not exceed 2,400 meters.
- Above 2,700 meters, limit daily ascent to 300 meters.
- Descend to lower altitude for sleeping if you ascend higher during the day.
- Move slowly ("pole-pole" technique on Kilimanjaro).
- Avoid alcohol, smoking, and sleeping pills.
- Drink 3-4 liters of water daily to prevent dehydration.
- Keep daypacks light (10-12 kg).
- Take Diamox (acetazolamide) after consulting a doctor.
- Inform others if you feel unwell and descend if symptoms worsen.
- Acute Mountain Sickness (AMS): Descent to lower altitude is mandatory. If immediate descent is not possible, low-flow oxygen, a portable hyperbaric chamber, or drug therapy can help.
- HAPE: Rapid descent, oxygen therapy, or hyperbaric oxygen. Nifedipine and sildenafil may be used.
- HACE: High-flow oxygen, descent, dexamethasone 8 mg four times a day (QDS) for cerebral oedema, and acetazolamide.
- Hyperbaric Chambers: Portable hyperbaric chambers simulate descent by increasing atmospheric pressure, temporarily relieving symptoms while awaiting actual descent.
References