What is the recommended prophylaxis for high altitude sickness?

High Altitude Sickness Prophylaxis

For high altitude sickness prophylaxis, slow ascent is the first-line preventive measure (300-600 m/day above 2500m), with acetazolamide recommended as the primary pharmacological prophylaxis for those with risk factors or history of altitude sickness. 1

Risk Assessment and Prevention Strategy

Non-Pharmacological Prevention:

• Gradual ascent rate:
  • 300-600 m/day when above 2500m altitude
  • Include rest days for every 600-1200m gained 1
• Avoid vigorous exertion before acclimatization
• Delay further elevation gain if symptoms appear

Pharmacological Prophylaxis:

First-line medication:

• Acetazolamide:
  • Dosing: 250mg twice daily or 500mg slow-release once daily
  • Start before ascent and continue during ascent
  • Continue for 3-4 days after reaching terminal altitude 1, 2, 3

Alternative medications:

• Nifedipine:
  • Particularly for those with history of High Altitude Pulmonary Edema (HAPE)
  • Extended-release formulation
  • Start with ascent and continue for 3-4 days after arrival at terminal altitude 1, 4
• Dexamethasone:
  • 4mg four times daily
  • For short-term prevention only (≤2-3 days)
  • Not recommended for longer use due to side effects 1, 2
• Tadalafil or other PDE5 inhibitors:
  • Alternative for HAPE prevention 1, 4

Special Populations and Considerations

Individuals with prior HAPE:

• Higher risk (62% recurrence with rapid ascent to 4559m)
• Nifedipine is strongly recommended as prophylaxis 1, 4

Women-specific considerations:

• May have greater expiratory flow limitations during hyperventilation
• Respiratory muscle training prior to altitude exposure may be beneficial
• Consider iron supplementation before altitude exposure
• Potentially higher risk for Acute Mountain Sickness (AMS) 1

Heart failure patients:

• NYHA Class I-II: May safely reach altitudes up to 3500m with slower ascent
• NYHA Class III: May reach up to 3000m with caution
• NYHA Class IV/Unstable: Should avoid high altitude exposure 1

Recognition and Management of Altitude Illness

Acute Mountain Sickness (AMS):

• Symptoms: Headache, reduced appetite, nausea, fatigue, dizziness, poor sleep
• Treatment: Descent, oxygen, acetazolamide, dexamethasone for severe cases 5, 6

High Altitude Pulmonary Edema (HAPE):

• Symptoms: Cough, exertional dyspnea, reduced exercise performance
• Treatment: Immediate descent, supplemental oxygen, nifedipine 1, 4

High Altitude Cerebral Edema (HACE):

• Life-threatening condition requiring urgent intervention
• Treatment: Immediate descent, oxygen, dexamethasone 5, 6

Common Pitfalls to Avoid

• Inadequate acclimatization: The most common mistake is ascending too quickly
• Ignoring early symptoms: Early recognition and treatment prevents progression
• Overreliance on medications: Drugs should supplement, not replace, proper acclimatization
• Using dexamethasone long-term: Should be limited to short durations due to side effects
• Continuing ascent with symptoms: Delaying further ascent or descending when symptoms appear is crucial

Remember that individual susceptibility is the most important determinant for altitude illness, and those with prior episodes should be particularly cautious and consider prophylactic medication 4.