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Acute Mountain Sickness in Children
Abstract & Commentary
By Philip R. Fischer, MD, DTM&H, Dr. Fischer is Professor of Pediatrics, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN.
Dr. Fischer reports no financial relationships relevant to this field of study.
This article originally appeared in the February 2009 issue of Travel Medicine Advisor. It was edited by Frank Bia, MD, and peer reviewed by Mary-Louise Scully. Dr. Bia is Professor of Geographic and Laboratory Medicine, Co-Director, Tropical Medicine and International Travelers' Clinic, Yale University School of Medicine, and Dr. Scully works for Sansum-Santa Barbara Medical Foundation Clinic, Santa Barbara, CA. Dr. Bia is a consultant for Pfizer and Sanofi-Pasteur, and receives funds from Johnson & Johnson, and Dr. Scully reports no financial information relevant to this field of study.
Synopsis: More than one-third of children traveling to relatively high altitudes experience symptoms of acute mountain sickness, but symptoms are relatively mild and usually self-limited.
Source: Bloch J, et al. Prevalence and time course of acute mountain sickness in older children and adolescents after rapid ascent to 3450 meters. Pediatrics 2009;123:1-5.
Faced with limited data about acute mountain sickness in children who travelled rapidly to high altitudes, Swiss researchers studied symptoms in 48 children (ages 10-17, mean age 13) who traveled 2.5 hours from low altitude (568 meters) to 3,450 meters (approximately 11,200 feet). During the subsequent two days, 38% developed symptoms of mountain sickness; most of these became symptomatic during the first few hours at altitude. Symptoms were relatively mild and decreased over the days of the study; five of the subjects took acetaminophen for headache, but no further treatment was required. Bloch et al concluded that pharmacologic prophylaxis may not be needed.
Acute mountain sickness presents as headache, fatigue, abdominal discomfort, dizziness, and/or sleep difficulties in individuals who have ascended to high altitude. Several factors affect the risk of developing acute mountain sickness.
Previous experience suggests that children and adults are equally affected, but that adults older than 50 years are less likely to become symptomatic.1 Even among pre-verbal children, 22% had acute mountain sickness during their first few hours at an American ski resort at 3,488 meters elevation, while 20% of their adult companions developed symptoms.2 Nonetheless, a recent study showed that 92% of children, and only 25% of their parents, developed acute mountain sickness after ascending within 24 hours from sea level to 3,500 meters in Chile.3
The rate and extent of ascent affect the risk of symptoms, but it is difficult to predict an individual traveler's risk. Bloch et al identified 38% of their pediatric subjects as being symptomatic following ascent from 568 meters to 3,450 meters during 2.5 hours on a train. This is more than the 22% of pre-verbal children who became symptomatic during a 1.5 hour drive and brief gondola ride from 1,703 meters to 3,488 meters,2 but less than the 84% of adults who were symptomatic following a one-hour flight from 1,300 meters to 3,740 meters in the Himalayas.4 It is not always possible to compare results from different studies under different conditions to predict accurately the risk of acute mountain sickness for a specific traveler.
Not all childhood fussiness during vacations is due to high-altitude exposure. Several years ago, symptoms suggestive of acute mountain sickness developed in 28% of children at 2,835 meters and 21% of children vacationing at sea level.5 Traveling children might benefit from child-friendly scheduling, age-appropriate activity planning, and symptomatic care whether they are at high altitude or not.
Acetazolamide often is used to prevent altitude sickness in travelers, but this product is not approved for this indication by the US FDA for use in children younger than 12 years of age. Bloch et al suggest that preventive medication might not be needed in children since the symptoms were mild in their 48 subjects and diminished over two days. Alternatively, one might argue that acetazolamide is relatively safe when used for brief periods, and that avoiding a day of ill feelings is of great enough benefit to accept the small cost and risk of treatment. (Similarly, antibiotics routinely are used in travelers who develop diarrhea even though antibiotics are relatively safe, and travelers' diarrhea is usually mild and self-limited.) Rather than discourage the use of acetazolamide in children and adolescents, one might suggest that the use of the product be individualized based on personal risk-benefit considerations. Travelers with a previous history of acute mountain sickness are at greater risk of recurrent symptoms and likely would warrant preventive treatment. Pediatric travelers ascending rapidly, becoming active immediately upon arrival, and performing critically important tasks might also be provided appropriately with pharmacologic prophylaxis.
High-altitude pulmonary edema is much less common but much more severe than simple acute mountain sickness. Risk factors for high-altitude pulmonary edema in children include pre-existing viral upper respiratory infection6 and trisomy 21.7 It is likely that lower oxygen saturations are involved in triggering symptomatic altitude illness in these and other susceptible individuals. Even normal children have low oxygen saturations at high altitude; an oxygen saturation of 90% should be considered normal at 2,500 meters elevation and 85% is normal at 3,200 meters elevation.8 (New data suggest that the oxygen saturation in adult mountaineers breathing ambient air at 8,400 meters just after initiating a descent from the summit of Mount Everest is about 54%.9)
Children living long term at high altitude also face health risks, but several of these risks seem to be moderated by population-specific genetic factors.10 What else is new for high-altitude travelers? Travelers journeying between Golmud, China and Lhasa, Tibet now can enjoy the comforts of oxygen-supplemented train cars during their 14-hour voyage.11