Children at High Altitude

This is a summary of a report by an ad hoc committee of experts of the International Society for Mountain Medicine that met in March, 2001, and is used by permission. Many of the views expressed in this statement are extrapolated from adult data. New data, and local and individual circumstances should be considered when using the information to guide clinical recommendations for prevention and treatment of problems. Karl Neumann, MD, Editor, Wilderness Medicine Letter

Each year many thousands of lowland children travel to high altitude uneventfully. The majority of these pediatric ascents involve trips to mountain resorts, especially in North America and Europe. In addition, an increasing number of children are moving to reside with their families at high altitude as a result of parental occupation. While altitude travel is without incident for most, some of these children develop symptoms that may be attributed to altitude exposure. The particular risks of exposure of children to high altitude have not been thoroughly studied, and much of the advice must necessarily be extrapolated from adult data with due considerations of the influence of growth and development.

Some data, however, exist from smaller studies. The relative lack of prospective data or case studies, as compared to adults, probably reflects the relatively small number of children, resident at low altitudes, who are exposed to high altitude. There have been at least 291 cases of high altitude pulmonary edema (HAPE) reported in children in the literature, but many of these were in high altitude residents. In addition, members of the consensus group are aware of a number of anecdotes in which altitude may have been a contributing factor to significant illness and death. These cases include children with no underlying disease, children with a history of perinatal pulmonary disorders, children with respiratory infections, and children with underlying cardiac conditions.

The incidence of acute mountain sickness (AMS) in children seems to be the same as that observed in adults. The nature and incidence of HAPE may differ between children resident at low altitude who travel to high altitude and children resident at high altitude who return from travels near sea level. Lowland children probably have no increased risk of HAPE compared to adults. Children resident at high altitude are more likely than adults to develop re-entry HAPE. However, intercurrent viral infections may predispose to HAPE and such infections are statistically more frequent among young children.

There is no published information about the incidence of high altitude cerebral edema (HACE) in children and no case reports in the literature. There is very little information available that outlines risk factors for altitude illness specifically in children.

Symptoms and signs of acute altitude illness in children

At all ages (children and adults) the symptoms of altitude illness are non-specific and can be confused with unrelated variables such as intercurrent illness, dietary indiscretion, intoxication, or psychological factors associated with remote travel. However, when ascending with children, it is wise to assume that such symptoms are altitude-related and to take appropriate action, in addition to considering treatment for other possible causes.

In children under 3 years of age, travel to any new environment may result in alterations of sleep, appetite, activity, and mood. Differentiating behavioral changes caused by travel alone from changes caused by altitude illness is difficult. Because of variability in the developmental level of perception and expression, young children are not reliable reporters of symptoms of altitude illness, even when they can talk. Symptoms may appear as non-specific behavioral changes rather than specific complaints of headache or nausea. The typical symptoms of AMS in very young children include increased fussiness, decreased appetite and possibly vomiting, decreased playfulness, and difficulty sleeping. These symptoms usually begin 4 to 12 hours after ascent to altitude. A modification of the Lake Louise score has been developed that assesses the non-specific symptoms in very young children and may prove useful in the evaluation of preverbal children. However, at present this score has not been evaluated for routine use by parents or physicians in making decisions about management of children at high altitude. The score has been validated as having high inter-observer agreement when used by parents, and it may be helpful in educating parents about symptoms of AMS.

Some older children, particularly those in the age range 3 , 8 years old, and children with learning or communication difficulties may also be poor at describing their symptoms, making altitude illness difficult to recognize. In children 8 years and older, it is assumed that altitude illness will present in much the same way as it does in adults.

Prevention of acute altitude illness in children

It may be assumed that prevention principles of altitude illness in adults are also appropriate for children.

Graded ascent. Slow, graded ascent, allowing time for acclimatization, is helpful. An ascent rate of 300 meters per day above 2500 meters and a rest day every l000 meters has been recommended, but it is not clear whether a more cautious recommendation is more appropriate for children. In one report that recorded the change in heart rate and arterial oxygen saturation of children 7 , 9 years of age and their parents during a slow, graded ascent, children were found to acclimatize at least as well if not better than adults.

Drug prophylaxis. Drug prophylaxis to aid acclimatization in childhood usually should be avoided, as slower ascent achieves the same effect in most cases. In rare cases, where a rapid ascent is unavoidable, use of acetazolamide might be warranted. Prophylaxis may be indicated in a child with previous susceptibility to AMS. Side effects do occur with acetazolamide, such as paresthesias, skin rashes, and possible dehydration. Sulfa allergy is a contraindication.

Education. Children and their caretakers should be acquainted with the symptoms of AMS and its management prior to travel above 2500 meters. They should also know their childrenís reactions during travel, irrespective of altitude, to be capable of differentiating the two.

Emergency plan. A contingency plan should be at hand prior to travel by families going to remote altitude locations to ensure access to communications, prompt descent, and oxygen.

Group Travel. School expeditions are a popular educational experience for older children. It is essential that organizations planning school group expeditions to (sleeping) altitudes above 2500 meters plan an itinerary that allows graded ascent, rest days, easy descent, and a flexible itinerary in case of illness. Pre-expedition planning should include:

  • Assessment of past medical history for each child.
  • Education of parents, staff, and children about AMS and other expedition health hazards.
  • Wilderness first aid training for staff members and preparation of an appropriate first aid kit.
  • Emergency and evacuation planning, including means of communication in an emergency.
  • Medical and evacuation insurance (for all travelers).

Treatment of acute altitude illness in children

There are no studies of treatment of acute altitude illness in children. However, it seems appropriate to follow adult treatment algorithms with appropriate pediatric drug doses as outlined below.

It may be prudent to be more cautious in managing children with AMS and descend earlier after the onset of symptoms than would be the case for an adult, since the natural history of AMS in childhood is not well characterized. Descent, where possible, should involve minimal exertion, which might exacerbate symptoms, and, where practical, the child should be carried during descent.

Treatment of altitude illness in children

Acute Mountain Sickness (AMS)

Mild

     

  1. Rest (stop further ascent) or preferably descend until symptoms cease (particularly with younger children).

    2.  

  2. Symptomatic treatment, such as analgesics and anti-emetics.

Moderate (worsening symptoms of AMS despite rest and symptomatic treatment)

     

  1. Descent
  2. Oxygen
  3. Acetazolamide 2.5 mg/kg/dose p.o. 8-12 hours (maximum 250 mg per dose).
  4. Dexamethasone 0.15 mg/kg/dose p.o. every 4 hours.
  5. Hyperbaric chamber (only used to facilitate descent, which should be undertaken as

soon as possible). Symptomatic treatment, such as analgesics (acetaminophen, ibuprofen) and anti-emetics in appropriate pediatric doses. Use of aspirin is not recommended in young children, due to the association with Reyesí syndrome.

High Altitude Pulmonary Edema (HAPE)

  1. Descent
  2. Sit upright
  3. Oxygen
  4. Nifedipine 0.5 mg/kg/dose p.o. every 8 hours. The maximum dose is 40 mg.

    5. Nifedipine is necessary only in the rare case when response to oxygen and/or descent is unsatisfactory.

  5. Use of dexamethasone should be considered because of associated high altitude

    6. cerebral edema (HACE).

  6. Hyperbaric chamber (only used to facilitate descent, which should be undertaken as

soon as possible).

High Altitude Cerebral Edema (HACE)

  1. Descent
  2. Oxygen
  3. Dexamethasone 0.15 mg/kg/dose p.o. every 4 hours.
  4. Hyperbaric chamber (only used to facilitate descent, which should be undertaken as soon as possible).

Sudden Infant Death Syndrome (SIDS)

It is unclear whether exposure to high altitude invokes an increased risk of SIDS as there are conflicting reports. As at sea level, the risk of SIDS may be reduced by always laying the infant on its back to sleep and avoiding passive exposure to tobacco smoke. The possibility of an association warrants careful consideration of an ascent to altitude with a child younger than 1 year of age. There is also a theoretical risk and some evidence that exposure to altitude may interfere with the normal respiratory adaptation that occurs following birth.

Cold Exposure

Infants and small children are particularly vulnerable to the effects of cold because of their large surface area to volume ratio. The child who has to be carried during a hike is not generating heat through muscle activity and is at risk of hypothermia. Adequate clothing is essential to prevent misery, hypothermia and frostbite. The committee is aware of a number of cases of frostbite of extremities, including those necessitating amputations.

Sun Exposure

Reflection from snow and a thinner atmospheric layer at high altitude make the risk of solar ultraviolet radiation burns more likely than at sea level. Children are more likely to burn than adults if exposed to excess sun. Appropriate sun-block creams (UVA and B, SPF>30, applied before sun exposure), hats, long sleeves, and goggles are required to prevent sunburn and snowblindness.

Other factors to consider when traveling in the altitude environment with children

For many parents who carry their children into the mountains, the trip is an opportunity to relax away from their normal daily activities. However, a number of factors should be considered that may improve the enjoyment of such travel for the child and parents.

  • Boredom. Young children typically have a short attention span and will easily become bored after traveling relatively short distances. A stimulating itinerary should be carefully chosen.
  • Physical ability. Estimates of distances that young children might be expected to walk (at sea level) have been made but these are only guidelines that must be adjusted for each individual child. Children should only walk as long as they want to.
  • Food. Some young children are very poorly adaptable to changes in circumstances and refuse unfamiliar food. It is helpful to try out foods prior to altitude travel where possible. It is important to ensure an adequate food and liquid intake.
  • Hygiene: In remote treks, traveling with young infants may be particularly stressful for parents trying to maintain appropriate hygiene for their child.
  • Intercurrent illness: Gastroenteritis is probably no more common among child travelers than among adults. Children are more prone to develop severe, life-threatening dehydration with gastroenteritis. Supplies to make a safe oral rehydration solution (ORS) should be part of every medical kit.

Children with pre-existing illness

Children with certain underlying chronic medical conditions may be at increased risk of developing either an exacerbation of their chronic illness or an illness directly related to altitude such as HAPE. Little to no data exists for determining the risk for specific medical conditions such as cystic fibrosis or chronic lung disease of prematurity (bronchopulmonary dysplasia). However, by first possessing a knowledge of known risk factors for the development of altitude related illnesses and then assessing how each childís condition may affect his/her cardiopulmonary physiology in a hypoxic environment, one may be able to determine the relative risk of developing complications at altitude. For instance, both a relative lack of increased minute ventilation at altitude and pulmonary vascular overperfusion, such as is seen in individuals who lack a pulmonary artery, are risk factors for the development of HAPE.

It is, therefore, logical to believe that children with congenital heart defects resulting in overperfusion of the pulmonary vascular bed such as atrial and ventricular septal defects, unilateral absence of a pulmonary artery and patent ductus arteriosus would be at increased risk for the development of altitude related illnesses like HAPE. Similarly, children who have significant lung disease secondary to premature birth or cystic fibrosis and have elevated PaCO2 levels at sea-level may not be able to increase their minute ventilation when stressed by altitude and thus be at risk for illness at altitude. Children with Down Syndrome have a high incidence of both obstructive apnea and hypoventilation as well as congenital heart defects resulting in increased pulmonary blood flow. Perhaps these physiologic abnormalities contribute to the development of HAPE in children with Down Syndrome at relatively low altitudes.

Children with non-cardiopulmonary disorders may also be at increased risk for the development of illness at altitude depending on how the disorder responds to the stresses of altitude. For instance, a child with cortisol deficiency secondary to adrenogenital syndrome developed HAPE at moderate altitude as did two children with cancer who had recently finished chemotherapy. New onset or recurrent seizures in children who are no longer on medication may occur at an altitude as low as 2700 meters. In addition, children with sickle cell anemia appear to be at increased risk for sickling crises at altitude.

Above all, if one decides to travel to altitude with children with chronic medical conditions, special planning to ensure adequate supplies and for expedient evacuation is essential. This may mean avoiding isolated, backcountry areas.

Statement on special considerations for ascent to altitude with children

  • There are no data about safe absolute altitudes for ascent in children.
  • The risk of AMS is for ascents above about 2500 meters, particularly sleeping above 2500 meters.
  • Intercurrent illness might increase the risk of altitude illness.
  • Effects of longer-term (weeks) exposure to altitude hypoxia on overall growth and brain and cardiopulmonary development are unknown.

Location of travel

  • Most mountain tourist sites and ski resorts in industrialized countries are located at or below about 3000 meters and a majority of travelers to these sites will sleep at about 3000 meters or less. Acute mountain sickness is common at this altitude and there is probably a small risk of serious altitude illness. Once recognized, altitude illness is effectively managed with oxygen and/or descent in most cases. Ascents during tourist activities (cable car rides, travel on mountain roads, and ski trips), higher than the resort location, to about 4000 meters are usually brief (hours) and probably carry minimal additional risk. Longer trips above 3000 meters on foot or horseback should be undertaken with slow, graded, and cautious ascent to reduce the possibility of AMS.
  • Ascents made in remote mountain locations without rapid access to medical care should be undertaken with greater caution. Ascents with sleeping altitudes at or below 3000 meters carry a low risk of serious altitude illness, but when HAPE or HACE occur management can be more difficult than in developed areas. Higher ascents in this context should be undertaken with slow, graded ascent, rest (acclimatization) days, and careful emergency planning.

Length of altitude exposure

  • Ascents higher than 3000 meters that are prolonged for more than one day or require sleeping above 3000 meters increase the risk of AMS and should be undertaken cautiously with slow, graded ascent, built-in rest days, and with emergency planning.
  • In circumstances where the child is traveling above 2500 meters altitude because of parental occupation AND prolonged altitude residence is anticipated, slow graded ascent should be undertaken. For infants less than 1 year of age planning to reside permanently at altitude, some authorities recommend delaying ascent until beyond the first year of life because of the slight risk of subacute infantile mountain sickness* (SIMS) above 3000 meters. But this is usually impractical if parental separation is to be avoided. Therefore, after a careful physical examination before ascent and initial acclimatization to high altitude, the infant should be followed closely with respect to growth percentiles; pulse oximetry may be useful, especially during sleep; and the ECG should be monitored periodically for the development of right ventricular hypertrophy.

* SIMS is a rare but serious condition seen in infants of low altitude ancestry who are continuously exposed to altitudes over 3000 meters for more than a month. It involves right ventricular cardiac failure.

Wilderness Medicine Letter, Volume 19, Number 2, Spring 2002