From the Guidelines
For individuals traveling to high altitude destinations, I strongly recommend a gradual ascent of no more than 1,000-1,500 feet per day once above 8,000 feet, with a rest day every 3,000 feet, to prevent altitude-related illnesses. This recommendation is based on the most recent and highest quality study available, which emphasizes the importance of gradual ascent in preventing high altitude retinopathy (HAR) and other altitude-related illnesses 1.
Key Recommendations
- Acetazolamide (Diamox) is the primary medication for prevention, taken at 125mg twice daily starting 24 hours before ascent and continuing for 48 hours after reaching your maximum altitude 1.
- For treatment of acute mountain sickness, increase the dose to 250mg twice daily 1.
- Dexamethasone can be used as an alternative at 4mg every 6 hours, particularly for those who cannot tolerate acetazolamide 1.
- Immediate descent is crucial for severe altitude illness.
- Stay well-hydrated, avoid alcohol, and maintain adequate calorie intake.
Special Considerations
- Individuals with pre-existing cardiovascular conditions should consult with their doctor before traveling to high altitude destinations, as they may need to take additional precautions or modify their medication regimen 1.
- Patients with coronary artery disease (CAD) should wait at least 6 months after an uncomplicated acute coronary syndrome (ACS) episode or revascularization before traveling to high altitude 1.
- Patients with heart failure (HF) should be cautious when traveling to high altitude, as they may be at increased risk for dehydration and electrolyte imbalances, and should carefully evaluate the use of diuretics such as acetazolamide 1.
Rationale
These recommendations work because acetazolamide acts as a respiratory stimulant by causing mild metabolic acidosis, which increases ventilation and oxygen levels 1. The body needs time to acclimatize by increasing red blood cell production and respiratory rate, which is why gradual ascent is so important for preventing potentially life-threatening conditions like high-altitude pulmonary edema (HAPE) or cerebral edema (HACE) 1.
From the Research
Altitude Medicine
- Altitude medicine involves the prevention and treatment of altitude-related illnesses, such as acute mountain sickness (AMS) and high-altitude pulmonary edema (HAPE) 2, 3.
- Acetazolamide is a commonly used medication for the prevention and treatment of AMS, and it works by inhibiting carbonic anhydrase, which helps to reduce the symptoms of AMS 3.
- However, the effectiveness of acetazolamide in preventing HAPE is still unclear, with some studies suggesting that it may not be effective in reducing the incidence of HAPE 2.
- Other medications, such as nifedipine and phosphodiesterase inhibitors, may also be effective in preventing HAPE, and may be considered as alternative treatments 4.
Mechanisms of Action
- Acetazolamide has several mechanisms of action, including the inhibition of carbonic anhydrase, which helps to reduce the symptoms of AMS 3.
- It also improves ventilation and reduces hypoxic pulmonary vasoconstriction, which can help to prevent HAPE 2, 4.
- Additionally, acetazolamide has been shown to improve sleep quality and reduce the risk of AMS, which can help to prevent HAPE 3.
Side Effects
- Acetazolamide can cause several side effects, including paraesthesias, taste disturbances, polyuria, and fatigue 5.
- The risk of these side effects can be dose-dependent, with higher doses of acetazolamide increasing the risk of paraesthesias and taste disturbances 5.
- However, the overall risk of side effects with acetazolamide is generally considered to be low, and it is often well-tolerated by patients 5.