What are the recommendations for preventing and treating Acute Mountain Sickness (AMS) in individuals traveling to high altitudes?

Altitude Sickness Prevention and Treatment Recommendations

The most effective strategy for preventing Acute Mountain Sickness (AMS) is slow ascent (<400m/day above 2,500m), with rest days for every 600-1200m gained, combined with acetazolamide prophylaxis (125mg twice daily) starting 24 hours before ascent for those at higher risk. 1

Prevention Strategies

Non-Pharmacological Prevention

• Gradual Ascent:

  • Limit ascent to less than 400m/day when above 2,500m altitude 2, 1
  • Include a rest day for every 600-1200m gained in elevation 1
  • For those with access to altitude facilities, pre-acclimatization for 2 weeks with >8 hours/day at progressively increasing altitudes can be beneficial 1

• Hydration and Nutrition:

  • Maintain adequate fluid intake
  • Avoid alcohol consumption
  • Follow a high-carbohydrate, low-fat, low-salt diet 3
  • Women may require smaller increases in carbohydrate intake at altitude compared to men 2

• Timing for Women:

  • Consider timing altitude exposure during the luteal phase of the menstrual cycle, when hypoxic ventilatory response is higher 2, 1

Pharmacological Prevention

• Acetazolamide (First-line):

  • Dosage: 125mg twice daily starting 24 hours before ascent 1
  • For rapid ascents above 3,500m, higher doses (500-750mg/day) may be more effective 1, 4
  • Mechanism: Increases ventilation and oxygenation by creating a mild metabolic acidosis

• Dexamethasone (Alternative):

  • Use only for short-term prevention (2-3 days) due to side effects 1
  • Effective for treating cerebral symptoms but not routinely recommended as prophylaxis 3

Treatment of Altitude Sickness

Mild to Moderate AMS

• Stop ascent and rest at current altitude
• Acetazolamide: 250mg every 12 hours until symptoms resolve
• Analgesics for headache (ibuprofen or acetaminophen)
• Antiemetics for nausea/vomiting

Severe AMS or Progression to HAPE/HACE

• Immediate descent (mandatory for severe symptoms) 1
• Supplemental oxygen if available, particularly for severe symptoms 1
• Medications:
  • Dexamethasone for HACE
  • Nifedipine (20mg three times daily) specifically for HAPE when descent is impossible 1

Special Populations and Considerations

Cardiovascular Conditions

• Well-controlled hypertensive patients may reach altitudes >4000m with adequate medical therapy 1
• NYHA class I-II patients can generally travel to intermediate altitudes (~2,000m) safely 1
• NYHA class III patients should consider supplemental oxygen during air travel 1
• NYHA class IV patients should avoid high altitude travel 2, 1

Women-Specific Considerations

• Women may have higher risk of AMS than men 1
• Women exhibit lower vasoconstriction and greater hypoxia-induced vasodilation 2
• Training intensity may need to be decreased more in women than men during chronic altitude/hypoxic exposure due to potentially greater hypoxemia 2

Recognizing Altitude Sickness

AMS Symptoms

• Headache (primary symptom)
• Insomnia
• Anorexia and nausea
• Dizziness
• Fatigue

Warning Signs of Progression to HAPE/HACE

• HAPE: Persistent dry cough, shortness of breath at rest, frothy/pink sputum, extreme fatigue
• HACE: Ataxia, altered mental status, severe headache unresponsive to analgesics, vomiting

Common Pitfalls to Avoid

• Ascending too rapidly: Most common cause of altitude sickness
• Ignoring early symptoms: Can lead to progression to life-threatening conditions
• Overexertion: Intense exercise upon arrival at altitude increases risk
• Dehydration: Exacerbates symptoms and increases risk
• Continuing ascent with symptoms: Can lead to dangerous progression of illness

By following these evidence-based recommendations, travelers to high altitudes can significantly reduce their risk of developing altitude sickness and ensure safer experiences at elevation.