Treatment and Prevention of Altitude Sickness (Acute Mountain Sickness)
The most effective prevention for altitude sickness is slow ascent (<400 m/day above 2,500m), while acetazolamide is the primary pharmacological preventive measure, and immediate descent is the definitive treatment for severe cases. 1
Understanding Altitude Sickness
Altitude sickness encompasses several conditions that occur due to hypobaric hypoxia at high altitudes:
Acute Mountain Sickness (AMS): Most common form
- Symptoms: Headache, nausea, vomiting, fatigue, dizziness, sleep disturbances
- Onset: Usually within 6-12 hours of ascent
- Risk increases above 2,500m
High-Altitude Cerebral Edema (HACE):
- Severe progression of AMS
- Symptoms: Severe headache unresponsive to analgesics, ataxia, altered mental status, coma
High-Altitude Pulmonary Edema (HAPE):
- Symptoms: Dyspnea, cough (initially dry, later with pink frothy sputum), chest tightness
- May occur with or without AMS symptoms
Risk Factors
- Rapid ascent (>300-400m/day above 2,500m)
- Previous history of altitude illness
- Home residence at low altitude
- Physical exertion before acclimatization
- Pre-existing cardiopulmonary conditions
- Women may have higher risk of AMS than men 1
- Sleep disturbances at altitude
Prevention Strategies
Non-Pharmacological Prevention
- Gradual ascent: Keep ascent rate <400m/day above 2,500m 1
- Rest days: Include a rest day for every 600-1200m gained 1
- Pre-acclimatization: For those with access to altitude facilities, 2 weeks with >8h/day at progressively increasing altitudes 1
- Avoid exertion: Minimize physical activity before acclimatization
- Adequate hydration: Maintain proper fluid intake
- Consider timing: For women, mid-luteal phase may be more appropriate for acute exposure to high altitude 1
Pharmacological Prevention
Acetazolamide:
- Dosage: 500mg/day (divided doses) 2
- Start 24 hours before ascent and continue for 2-3 days at altitude
- Mechanism: Induces metabolic acidosis, stimulating ventilation
For those with history of HAPE:
Treatment Approaches
Mild to Moderate AMS
- Rest and acclimatization: Stop ascent until symptoms resolve
- Analgesics: Ibuprofen for headache 3
- Acetazolamide: 500mg/day to speed acclimatization 2
- Adequate hydration
Severe AMS and HACE
- Immediate descent: Minimum 300m, mandatory for all cases 4
- Supplemental oxygen: If available, to maintain SpO2 >90%
- Dexamethasone: First-line treatment for severe AMS/HACE 2
- Portable hyperbaric chambers: When descent is not immediately possible
HAPE Treatment
- Immediate descent: Primary treatment 1
- Supplemental oxygen: To maintain SpO2 >90%
- Nifedipine: For pulmonary vasodilation when descent is delayed 2
- Minimal exertion: Patient should not exert themselves during descent
Special Considerations
Heart Failure Patients
- Travel to intermediate altitudes (~2,000m) is generally safe for patients with good exercise tolerance (NYHA class I-II) 1
- NYHA class III patients should consider supplemental oxygen during air travel 1
- NYHA class IV patients should avoid high altitude travel 1
- Diuretic therapy should be adjusted for potential hypoxic diuresis 1
Children
- Children with congenital heart disease may have increased pulmonary vascular resistance at altitude 1
- Children with history of HAPE should follow adult prevention protocols 1
- Symptoms in children include cough, exertional dyspnea, and reduced exercise performance 1
Common Pitfalls
- Delayed recognition: Symptoms may be attributed to fatigue, dehydration, or viral illness
- Continued ascent: Pushing through symptoms can lead to severe illness
- Inadequate preparation: Failing to allow time for acclimatization
- Overexertion: Physical activity before acclimatization increases risk
- Ignoring warning signs: Early symptoms should prompt cessation of ascent
- Inadequate monitoring: Regular assessment of symptoms is essential
By following these prevention and treatment strategies, the risk of altitude sickness can be significantly reduced, allowing for safer travel to high altitude destinations.