At What Height Do You Consider Preventative Treatment for Acute Mountain Sickness?

Patient Presentation
A 15-year-old male came to clinic for travel advice. He was traveling to the Andes Mountains for most of his trip. He was going to ~3000m altitude and would be acclimatizing there for a couple of days before going to ~3500 m hiking over 4 days. He then would be returning to sea level. He had hiked in the Rocky Mountains going to an altitude of 2500 m without acclimatization without any problems. The past medical history showed a broken forearm. The family history was non-contributory.

The pertinent physical exam showed normal vital signs and growth parameters of 25-50%. His examination was normal. The diagnosis of a healthy male was made. The Centers for Disease Control website was consulted for the recommendations for the countries he would be visiting and he was offered typhoid and yellow fever vaccine in addition to malaria prophylaxis. Because of the altitude, he and his parents also wanted to use acetazolamide for acute mountain sickness prevention. The physician discussed the need to stay hydrated and hike slowly. “Mom and Dad have been talking non-stop about how I have to tell them if I have a headache or feel sick to my stomach. I know it is important,” the teenager said. The parents also said that they had a guide and also a plan if someone in the group was having problems with mountain sickness and would need to descend.

Acute mountain sickness (AMS) is a well-known problem for some people who travel to high altitude, especially altitudes > 2500 m (~8200 feet). Symptoms include headache, nausea or emesis, shortness of breath, dizziness, fatigue, difficulty sleeping and poor appetite. The incidence in adults ranges from 25% at 2975 m to up to 75% at 5896 m. The incidence in children is less clear but it appears that children are more susceptible at 45% for 16-19 year olds for similar altitudes. Risk factors are numerous including age, gender, obesity, ascent rate, altitude for sleeping, previous exposure to high altitude, previous AMS, and history of cardiopulmonary disease. Different studies show physical fitness may or may not be a risk factor. One study of teenage children found for children 11-13 years old, male gender and increased body mass index increased the risk for AMS. This was for an ascent from 25 m to 3386 m over 3 days in Taiwan. Physical fitness was not associated with AMS occurrence in this study. AMS definitions for research and other purposes often use the Lake Louise AMS score which was created in 1991. It looks at presence of headache and at least 1 other symptom including gastrointestinal symptoms (i.e. anorexia, nausea or emesis), fatigue or weakness, dizziness or lightheadedness and difficulty sleeping. HACE (high altitude cerebral edema) and HAPE (high altitude pulmonary edema) severity are also defined. Criteria can be found here and here.

Children born and living in high altitudes have asymptomatic pulmonary hypertension that declines over time. Persistent patent ductus arterosus is higher in these children (delayed 3-4 days instead of usual 24 hours for those at lower levels). HAPE (high altitude pulmonary edema) can occur in these children who go to lower levels and return (re-entry). There are probably some genetic factors at play where the children who have long ancestry have lower incidences of pulmonary artery hypertension, but those without this long ancestry or newcomers have higher rates of pulmonary artery hypertension (Tibet vs Leadville Colorado 3100 m).

Learning Point
The mainstay of treatment for AMS is descent to a lower altitude. Mild forms of AMS may only need this treatment. Additional treatment may include oxygen, acetazolamide, dexamethasone, or hyperbaric oxygen. Acclimatization is one of the best ways to also help prevent AMS. For prevention for altitudes >2500 one may consider using acetazolamide by general convention as risks increase but AMS can occur at lower altitudes also. The optimal dosage is debated. A recent systematic review concluded that “The degree of efficacy of acetazolamide for the prevention of AMS is limited when the baseline risk is low, and there is some evidence of dose-responsiveness.” Dosages of 250 mg, 500 mg and 750 mg/daily are commonly used. Acetazolamide has potential side effects of polyuria, taste disturbance and parasthesias. Being well hydrated and moving slowly and paying attention to one’s exercise effort are always good general precautions.

Questions for Further Discussion
1. What other preventative advice would you give this patient?
2. What are your sources of advice for travel for your patients?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for this topic: Traveler’s Health

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Pollard AJ, Niermeyer S, Barry P, Children at high altitude: an international consensus statement by an ad hoc committee of the International Society for Mountain Medicine, March 12, 2001. High Alt Med Biol. 2001 Fall;2(3):389-403.

Anand IS, Wu T. Syndromes of subacute mountain sickness. High Alt Med Biol. 2004 Summer;5(2):156-70.

Niermeyer S. Going to high altitude with a newborn infant. High Alt Med Biol. 2007 Summer;8(2):117-23.

Penaloza D, Sime F, Ruiz L. Pulmonary hemodynamics in children living at high altitudes. High Alt Med Biol. 2008 Fall;9(3):199-207.

Wilson MH, Newman S, Imray CH. The cerebral effects of ascent to high altitudes. Lancet Neurol. 2009 Feb;8(2):175-91.

Kayser B, Dumont L, Lysakowski C, Combescure C, Haller G, Tramèr MR. Reappraisal of acetazolamide for the prevention of acute mountain sickness: a systematic review and meta-analysis. High Alt Med Biol. 2012;13:82-92.

Bradwell AR, Myers SD, Beazley M,; Birmingham Medical Research Expeditionary Society. Exercise limitation of acetazolamide at altitude (3459 m). Wilderness Environ Med. 2014 Sep;25(3):272-7.

Wu SH, Lin YC, Weng YM, The impact of physical fitness and body mass index in children on the development of acute mountain sickness: A prospective observational study. BMC Pediatr. 2015 May 8;15:55.

Rimoldi SF, Rexhaj E, Duplain H, Acute and Chronic Altitude-Induced Cognitive Dysfunction in Children and Adolescents. J Pediatr. 2016 Feb;169:238-43.

Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa