What are the prevention and treatment strategies for altitude sickness (Acute Mountain Sickness)?

Altitude Sickness: Prevention and Treatment Strategies

The most effective prevention strategy for altitude sickness is a slow ascent rate (less than 400 m/day above 2500m), combined with prophylactic acetazolamide (125-250 mg twice daily) starting 24 hours before ascent for those at higher risk. 1

Understanding Altitude Sickness

Altitude sickness, also known as Acute Mountain Sickness (AMS), occurs when individuals ascend too rapidly to high altitudes without proper acclimatization. It encompasses several conditions:

• Acute Mountain Sickness (AMS): Milder form with symptoms including headache, nausea, dizziness, fatigue, and insomnia
• High-Altitude Cerebral Edema (HACE): Severe progression of AMS with symptoms of severe headache, ataxia, and mental deterioration
• High-Altitude Pulmonary Edema (HAPE): Characterized by extreme fatigue, dyspnea, chest tightness, and potentially pink frothy sputum

Risk Factors

• Rapid ascent: Ascending faster than 300-600 m/day above 2500m 1, 2
• Gender: Women appear to have a higher risk of AMS 3, 1
• Previous history: Prior episodes of altitude sickness increase risk
• Physical condition: Poor physical fitness may increase risk
• Underlying conditions: Heart failure, anemia, and respiratory conditions increase susceptibility 3
• Menstrual cycle phase: Women may have better oxygenation during the luteal phase 3

Prevention Strategies

Non-Pharmacological Approaches

1. Gradual ascent:

   • Limit ascent to less than 400 m/day above 2500m 3, 1
   • Include a rest day for every 600-1200m gained 1

2. Pre-acclimatization:

   • For those with access to altitude facilities, 2 weeks with >8 hours/day at progressively increasing altitudes is beneficial 3
   • Particularly important for women due to higher AMS risk 3, 1

3. Adequate hydration and nutrition:

   • Maintain proper hydration
   • Women may require less increase in carbohydrate intake at altitude compared to men 3

4. Iron supplementation:

   • Consider for women before altitude exposure due to higher risk of iron deficiency 1

Pharmacological Prevention

1. Acetazolamide:

   • Dosage: 125-250 mg twice daily starting 24 hours before ascent 1
   • Mechanism: Increases ventilation and oxygenation by creating a mild metabolic acidosis
   • Contraindications: Kidney stones, sulfa allergy, severe hepatic/renal disease 1
   • Side effects: Paresthesias, altered taste, increased urination, dizziness 1

2. Dexamethasone:

   • Alternative for those who cannot take acetazolamide
   • 4 mg every 6 hours starting 48 hours before ascent 4
   • More effective for cerebral symptoms than respiratory symptoms

3. Nifedipine:

   • 20 mg extended-release every 8 hours for HAPE prevention 1
   • Particularly useful for those with previous HAPE episodes

Treatment Strategies

Mild to Moderate AMS

1. Stop ascent and rest:

   • Allow time for acclimatization
   • Avoid further ascent until symptoms resolve

2. Medication:

   • Acetazolamide: 250 mg twice daily 1, 2
   • Ibuprofen for headache 5
   • Avoid sedatives and alcohol

3. Oxygen supplementation:

   • If available, maintain oxygen saturation >90% 1

Severe AMS, HACE, or HAPE

1. Immediate descent:

   • Most effective treatment
   • Descend at least 300-600m as soon as possible 1, 6

2. Oxygen therapy:

   • Administer supplemental oxygen to maintain saturation >90% 1

3. Medication:

   • For HACE: Dexamethasone (8 mg initially, then 4 mg every 6 hours)
   • For HAPE: Nifedipine (10 mg initially, then 30 mg extended-release every 12-24 hours)

4. Hyperbaric therapy:

   • Portable hyperbaric chambers can be used when descent is not possible

Special Considerations

1. Heart failure patients:

   • Travel to intermediate altitudes (~2000m) is generally safe for those with good exercise tolerance at sea level 3
   • Diuretic therapy should be tailored to account for hypoxic diuresis 3

2. Women travelers:

   • Consider timing high altitude exposure during mid-luteal phase when hypoxic ventilatory response is higher 3
   • Perform hypoxic tolerance tests in follicular phase to assess risk 3

3. Post-ocular surgery:

   • Avoid air travel for 2-6 weeks after intraocular gas instillation 3

Monitoring and Follow-up

• Monitor for progression of symptoms
• Check for signs of HACE (ataxia, altered mental status)
• Monitor oxygen saturation if possible
• For those on acetazolamide, monitor for electrolyte imbalances and metabolic acidosis 1

By following these prevention and treatment strategies, the risk and severity of altitude sickness can be significantly reduced, allowing for safer travel to high-altitude destinations.