From the Guidelines
The recommended prophylaxis for high altitude sickness includes gradual ascent, and for those with a history of HAPE, nifedipine is recommended, started with ascent and continued for 3 to 4 days after arrival at the terminal altitude, as it has been shown to reduce the incidence of HAPE in adults 1. When considering prophylaxis for high altitude sickness, it's crucial to differentiate between general prevention strategies and those specifically aimed at preventing High Altitude Pulmonary Edema (HAPE), a severe and potentially life-threatening condition.
- General preventive measures include gradual ascent, with some guidelines suggesting a rate of ascent of 300 to 600 meters per day, and including rest days as part of the ascent plan to allow for acclimatization 1.
- For individuals with a history of HAPE, pharmacological prophylaxis is considered, with nifedipine being a recommended option due to its efficacy in reducing the incidence of HAPE in adults, as demonstrated in a placebo-controlled RCT 1.
- Alternatives to nifedipine for HAPE prophylaxis may include PDE5 inhibitors, such as tadalafil, and dexamethasone, although these should be considered with caution due to potential side effects, such as severe acute mountain sickness associated with PDE5 inhibitors 1.
- It's also important to note that immediate descent to a lower altitude and administration of supplemental oxygen are critical components of therapy for individuals who develop HAPE, underscoring the importance of monitoring for symptoms and having a plan for emergency descent if necessary.
From the Research
High Altitude Prophylaxis
- The recommended prophylaxis for high altitude (HA) sickness includes a slow ascent, with a climbing rate of 300 to 600 m in one day, and spending at least nine or more nights at an altitude higher than 2500 m a.s.l. in the last 30 days before ascent 2.
- Pharmacological prophylaxis and treatment can be used if acclimatization is not possible, with acetazolamide being the drug of first choice for acute mountain sickness (AMS) prophylaxis 2, 3, 4, 5.
- Acetazolamide has been shown to be effective in preventing AMS, with a recommended dosage of 125 mg every 12 hours 5, or 250 to 500 mg 12 to 24 hours before ascent 2.
- Nifedipine is effective in preventing high-altitude pulmonary edema (HAPE), but not AMS, and should be taken in a dosage of 3 x 20 mg, beginning one day before climbing and continuing during climbing 2, 3, 6.
- Dexamethasone is also effective in preventing AMS, but its use is limited due to its euphoric effect 3, 4.
Prevention of High-Altitude Illness
- The risk of high-altitude illness (HAI) on rapid arrival to altitudes over 3350 m can range from 35% to nearly 50%, making it a significant risk for travelers 5.
- The use of prophylactic acetazolamide can help diminish the risk of HAI, and travel medicine practitioners should assess the risk of HAI and determine when it is appropriate to offer acetazolamide prophylaxis 5.
- Acetazolamide has been shown to be highly effective in preventing HAI, with a recommended dosage of 125 mg every 12 hours 5.