Another key difference between the musculoskeletal systems of children and adults is that children have an open growth plate, or physis, at the ends of long bones. The physis connects the metaphysis to the epiphysis and consists of soft cartilaginous cells that have the consistency of rubber and act as shock absorbers (Figure 99-2). They protect the joint surfaces from suffering the grossly comminuted fractures seen in adults. However, because the growth plate is more vulnerable to injury than are the strong ligaments or capsular tissues that attach to the epiphysis, a true sprain in a child is rare. Any significant juxta-articular tenderness in a child should be assumed to be a growth plate injury and immobilized accordingly. Such an injury is most common at the ankle (lateral malleolus), knee (distal femur), and wrist (distal radius). Physeal fractures have been classified into five Salter–Harris groups (see Figure 99-2). Salter–Harris I and II fractures generally heal without complications. Salter–Harris III and IV fractures often require open reduction of displaced fractures to realign the joint and growth plates and to permit normal growth. A Salter–Harris V fracture has a poor prognosis; impaction and crushing of some or all of the growth plate may result in a bony bridge that inhibits further growth or causes unequal, angulated growth. Consequently, any significant injury, especially if it involves the growth plate, requires full evaluation in a medical facility.

FIGURE 99-2 Salter–Harris classification of physeal fractures (I to V).

Cardiovascular and Respiratory Systems

Basic physiologic parameters change greatly during the transitions from infancy to childhood to adulthood. Recognizing these differences is important to avoid unnecessary and potentially harmful interventions in healthy children, and to intervene aggressively when abnormal vital signs are truly present. For example, a blood pressure of 70/35 mm Hg, pulse rate of 160 beats/min, and respiratory rate of 50 breaths/min are considered ominous vital signs for an adult. However, these vital signs are normal in a 2-month-old infant. Although blood pressure readings may not be available in a wilderness setting, it is possible to assess the general appearance, work of breathing, respiratory rate, pulse, and peripheral circulation of an ill child. These observations can accurately predict how sick a child is. In general, infants and children have higher respiratory and heart rates and lower blood pressure than do adults. The normal values for various age groups are presented in Table 99-2. It is important to note that children can often maintain normal blood pressure in the face of significant fluid or blood losses. Once blood pressure drops, however, children can deteriorate very rapidly. Therefore, prompt and aggressive fluid resuscitation is essential when other signs of dehydration or volume loss (e.g., tachycardia, increased capillary refill time, cool extremities) are present.

TABLE 99-2 Age-Specific Resting Heart Rate and Respiratory Rate *

Age	Heart Rate (beats/min)	Respiratory Rate (breaths/min)
0-5 mo	140 ± 40	40 ± 12
6-11 mo	135 ± 30	30 ± 10
1-2 yr	120 ± 30	25 ± 8
3-4 yr	110 ± 30	20 ± 6
5-7 yr	100 ± 20	16 ± 5
8-11 yr	90 ± 30	16 ± 4
12-15 yr	80 ± 20	16 ± 3

* Mean rate, ± 2 SD.

Thermoregulation

Because environmental extremes are often encountered when traveling in wilderness areas, it is important to recognize that thermoregulation is less efficient in children than in adults. A number of physiologic and morphologic differences make children more susceptible than adults to heat illness. During exercise, children generate more metabolic heat per unit mass than do adults. Children also have lower cardiac output at a given metabolic rate, resulting in lower capacity to convey heat from the body core to the periphery. Because they have a larger surface area–to-mass ratio, children also gain heat more rapidly from the environment than do adults when ambient temperature exceeds skin temperature. In hot environments, cooling from conduction, convection, and radiation ceases to be effective, leaving evaporation (sweating) as the only effective means of heat dissipation. Unfortunately, children have a lower capacity for evaporative cooling, presumably because of decreased sweat volume, regional differences in sweat patterns, and a higher sweat point (the rectal temperature when sweating starts).⁴² Finally, children acclimatize to hot environments at a slower rate than do adults.

Children are also at greater risk for hypothermia. Their larger surface area–to-mass ratio causes them to cool more rapidly than adults in cold environments. Children also have less subcutaneous fat and, therefore, less body insulation. Infants, in particular, have an inefficient shivering mechanism. This makes them particularly vulnerable to cold environments because shivering is the primary means of generating extra heat when humans are cold.⁴ In general, humans are poorly adapted for cold environments and must rely on adaptive behavioral responses, such as seeking shelter and dressing appropriately, to maintain body heat. Infants and young children are not capable of these responses and must rely on caregivers to provide shelter and appropriate clothing.

Immunology and Infections

Children experience a greater number of infections than do adults. The average 1-year-old suffers six to eight infections per year, whereas the average adult has only three to four infections per year. Infections in children also tend to be more severe. The younger the child, the more likely it is that a given infection represents a first exposure to a pathogen. A first-exposure infection is more likely to cause fever and produce severe symptoms than reexposure, in which the infection is attenuated by antibodies produced from the first exposure. Young children are also less likely to have cross-reacting antibodies from previous infections with antigenically related organisms. When present, cross-reacting antibodies serve to attenuate the immunologic response to an infection, thereby mitigating symptom severity.

Many common respiratory or viral infections tend to produce more severe symptoms in children because of anatomic differences. The pediatric bronchioles, eustachian tubes, and larynx are narrower and, therefore, more easily obstructed by edema and mucus. This obstruction worsens symptoms, prolongs clearance of infection, and increases risk for secondary infection. Pertussis (whooping cough) is a classic example of the difference in severity of infection between children and adults. Nearly 20% of infants with pertussis have severe complications, such as apnea, pneumonia, seizures, or encephalopathy. In contrast, adult pertussis, although a common cause of chronic cough, is generally indistinguishable from a common cold.

Trauma

Blunt trauma is the leading cause of morbidity and mortality in children ages 1 to 18 years. Closed head injuries are responsible for 80% of pediatric trauma deaths.⁴⁴ Although pedestrian and motor vehicle accidents are the source of many of these injuries, falls and drowning are close behind. Children differ from adults in their susceptibility to injuries from blunt trauma, and the injuries themselves differ. By nature of their smaller size, children’s airways are more prone to obstruction, particularly by their relatively large tongues. Their rib cages are more pliable and hence provide less protection to the lungs and mediastinum. Similarly, the abdominal musculature in children is underdeveloped relative to adults, leaving the intra-abdominal organs more vulnerable to injury. Pelvic fractures are uncommon in children; when they do occur, they rarely result in life-threatening bleeding or genitourinary injury.

The cranium of younger children is softer and hence less protective of the underlying brain. Fortunately, open fontanelles in infants provide a limited pressure buffer for children with intracranial hemorrhage or swelling. The relatively large head size, loose ligaments, poor cervical muscular support, and underdeveloped facets result in a different pattern of cervical spine injuries in children than is seen in adults. Although cervical spine injuries in children are uncommon, when they occur, they tend to be higher in the cervical spine and may involve injuries not visible with conventional radiography or computed tomographic (CT) scanning—thus the acronym SCIWORA, for spinal cord injury without radiographic abnormality. The term SCIWORA is somewhat of a misnomer, however, for although these injuries are not visible on radiograph or CT scan, they can be visualized with magnetic resonance imaging.

General Considerations and Expectations

Children of different ages have different needs and abilities. Expectations regarding distances of travel, pace, and safety issues vary depending on age (Table 99-3). This section explores the key issues regarding wilderness travel with children of various ages and provides general expectations for each age group. A number of helpful books that discuss different aspects of wilderness activities with children are listed under Suggested Readings.

TABLE 99-3 Age-Specific Expectations for Wilderness Travel

Age	Expectation	Safety Issues
0-2 yr	Distance traveled depends on adults. Use child carriers	Provide “safe play area” (e.g., tent floor, extra tarp laid out), bells on shoes
2-4 yr	Difficult age; stop every 15 min, hike 1-2 miles on own	Dress in bright colors, teach how to use whistle
5-7 yr	Hike 1-3 hr/day, cover 3-4 miles over easy terrain, rest every 30-45 min	Carry whistle (three blows for “I’m lost”), carry own pack with mini first-aid kid and water
8-9 yr	Hike a full day with easy pace, cover 6-7 miles over variable terrain; if 1.2 m (>4 feet) tall, can use framed pack	As for 5-7 yr, plus teach map use and route finding, precondition by increasing maximal distances by <10%/wk, watch for overuse injuries, keep weight of pack <20% of bodyweight
10-12 yr	Hike a full day at moderate pace, cover 8-10 miles over variable terrain	As for 8-9 yr; expand route planning role, compass use
Teens	Hike 8-12 miles or more at adult pace; may see a decrease in pace or distance with growth spurt	As for 10-12 yr, but expand survival and wilderness first-aid knowledge.

First 2 Years

Equipment

Because infants and young children are not capable of extended hikes, they are typically transported in carriers. Most front carriers work well from infancy until an age when babies can sit fairly well, typically 6 to 9 months (Figure 99-3). It is important that a front carrier extend up high enough in the back to completely support a young baby’s head. Once a child is sitting well, back carriers are better (Figure 99-4). Back carriers function on the same principle as framed backpacks, redistributing the weight off the shoulders and onto the hips. Many back carriers are able to stand alone and can double as a highchair. Children must be strapped into back carriers, because it is easy for a child to be catapulted out of a carrier if the adult bends over or falls.

FIGURE 99-3 Infants in front carriers.

(Courtesy Judith R. Klein, MD.)

FIGURE 99-4 Toddlers in back carriers.

(Courtesy Judith R. Klein, MD.)

Sleeping bags are available for infants and toddlers. However, in a warm climate, a blanket can suffice, and, in a colder environment, an insulated snowsuit is often adequate. Avoid placing diaper-clad infants into a sleeping bag with an adult; accidents or a leaky diaper can create very unpleasant sleeping conditions. Children, including young infants, also need their own sleeping pads. Such pads protect them from hard, rough ground under the tent and insulate them from the cold ground.

Shoes for young children should protect their feet and allow for full range of movement. The best shoes for toddlers are lightweight and flexible. They need shoes that stay on well, because children can flip their shoes off while in a carrier. Velcro-strapped shoes stay on well and are easy to put on and take off. Because children often lose shoes, an extra pair should be included.

2 to 4 Years

Travel Expectations

Children 2 to 4 years old are the most challenging to take into the wilderness. Two-year-olds become easily frustrated and throw temper tantrums, often as a result of the collision between adult restrictions and their desires for independence and control. By 2 years of age, children are becoming too heavy to carry for prolonged periods, but they are still incapable of hiking long distances on their own. They are just gaining bladder and bowel control, and accidents are frequent. Despite these difficulties, wilderness trips with this age group can be successful with appropriate planning, preparation, and adjustment of expectations.

A key ingredient to successful wilderness trips with small children is to keep things slow, simple, and flexible. This is the age of independence and assertion. The children need to be given some control and allowed to set a pace. Adults should encourage young children to express their natural curiosity and enthusiasm for the outdoors by letting them stop to explore their surroundings. Parents can enjoy rediscovering nature through the eyes of their children by exploring rocks and tide pools and observing a caterpillar’s crawl. Parents should expect to stop at least every 10 to 15 minutes while hiking. If a diversion or a stimulus is needed to get the children hiking again, parents can begin a story or favorite song and continue it while hiking. With patience and plenty of time, parents can expect children in this age group to travel 1 to 2 miles under their own power over easy terrain.

Safety

Unfortunately, 2- to 4-year-olds are notorious for exploring their environment by either wandering off or by trying to become a backcountry gourmet. Young children must be watched closely and cautioned to keep wild mushrooms, plants, berries, and other inedible or toxic items out of their mouths. Children should be kept within sight at all times, as their desire to explore often defies good judgment and exceeds their physical abilities. Although attacks are rare, mountain lions may view small children as easy prey and can strike quickly. Parents should, therefore, discourage their children from wandering ahead unaccompanied. Toddlers should also be encouraged to step only where they can see (i.e., on top of logs rather than over them) to avoid any unsuspecting reptile or large insect.

When selecting campsites, dangerous features, such as steep drop-offs and fast, deep water, should be avoided. Children should be dressed in brightly colored clothing, so they are more easily located if they become lost (Figure 99-5). As children get older, they may carry a whistle to call for help when they are lost. The standard distress signal is three blows to indicate “I’m lost” or “I need help”; the response is two blows to indicate “help is coming.” Parents should teach children to stay put once they discover they are lost and wait to let help come to them. If children panic and start running when they realize they are lost, they increase the chance not only of getting injured but also of traveling farther from the family. The concept of “hug a tree” will be described later in the chapter.

FIGURE 99-5 Appropriate wilderness wear: brightly colored clothing and whistle.

(Courtesy Judith R. Klein, MD.)

Food

The diet of 2- to 4-year-olds is usually quite simple but very individual. They tend to have strong preferences and dislikes. Unfortunately, most children at this age do not care for the convenient “all-in-one-pot” cooking common around campfires. Foods should be tested at home first to be sure they are acceptable to the child. Nutritious snacks such as raisins, granola bars, bagels, nut butters, string cheese, and fruit bars can be packed. These snacks may become a child’s meal. Small children should not be given items on which they may choke, such as peanuts, grapes, hard candies, or hot dogs. At least one adult member should be trained in basic cardiopulmonary resuscitation (CPR) and know how to assist a choking child.

Toileting

Most children become toilet trained by the end of their third year. However, accidents are common and parents need to be prepared with extra dry clothing that is readily accessible. Children should be taught correct toileting procedure for the wilderness environment. Stools should be deposited at least 200 feet (60 m) from a water source, buried in a hole approximately 6 inches (15 cm) deep, and completely covered. Many families carry a special trowel for this purpose. Some groups staying in one location for more than a day dig a specific toileting trench, 12 to 18 inches (30 to 45 cm) deep, to be used multiple times. They then add enough dirt after each use to cover all waste. Children need help learning to squat over the trench and to bury their stools.

It may be years before children gain reliable nighttime bladder control. Cotton and down sleeping bags should be avoided because they lose their insulating abilities and take a long time to dry. Fortunately, many synthetic bags are available, with fills such as Polarguard, Quallofil, and Hollofil, which maintain warmth and loft when wet.

School Age (5 Years and Up)

Travel Expectations

Once children enter kindergarten, their abilities and attention span increase dramatically. This enables them to participate more actively in many outdoor activities. Children are hungry for knowledge and readily absorb information about nature and outdoor activities. They enjoy being included in initial planning, as well as in field activities, such as setting up camp, cooking, and cleaning up. School-age children can understand maps and often enjoy following their progress from one point to another. This is an ideal age to explain to them the rules of living in and traveling through wilderness areas. The examples and rules parents set for appropriate behavior in the wilderness at this age become lessons engraved for a lifetime.

When parents are planning hiking trips, it is important that they have appropriate expectations for children’s evolving abilities (see Table 99-3). Children enrolled in organized sports activities are likely to have greater endurance in the wilderness. A child’s hiking ability can be estimated by walks around the neighborhood or in a local park. If this practice becomes a routine, children become preconditioned, increase their endurance, and learn to pace themselves. More importantly, parents can learn what to expect and can test methods for motivating their children. It is better to underestimate than to overestimate a child’s ability. Parents should also remember that children, like adults, have good and bad days, so allowances should be made.

Safety

School-age children can learn to become more self-sufficient and in tune with their surroundings. They can be taught to recognize landmarks in their environment, so they are less likely to become lost. Such landmarks can be pointed out, and children should be encouraged to view their surroundings from different angles so that they can find their way back if they stray off. Children should periodically turn around so they can see where they came from, as well as where they are going. As children advance in school years, they can learn survival skills, such as how to maintain warmth, build shelters, secure food and water, and use a signal mirror, map, and compass. As with the previous age group, they should carry a whistle and know how to use it appropriately.

Equipment

Children like to feel important, capable, and independent. These feelings are enhanced if they are allowed to carry some of their own gear. Even 5-year-olds like to carry their own soft backpacks. Items they can carry in the packs include snacks, favorite small toy, extra clothing, sunscreen, small trash bag (excellent to wear for warmth/rain protection), and whistle. As a child grows, the contents of his or her backpack should reflect his or her increasing independence, with more self-care and survival items. In addition to the preceding items, children may wish to carry their own water bottle, mini first-aid kit (adhesive bandages, wipes, personal medication), insect repellent, and other survival items as they learn to use them. The maximal weight of these packs should be 20% of the child’s bodyweight until he or she has had significant backcountry experience and can comfortably carry more. Once children reach 4 feet (1.2 m) in height, they can be fitted for a framed backpack. Internal-frame backpacks tend to be more comfortable than external-frame packs. When a backpack is properly fitted, the waistband should rest at the hips and the shoulder strap should be adjusted so that the weight is carried on the hips, not on the shoulders. With a framed pack, children can carry even more of their own gear. However, the total weight should be gradually increased to allow the child to become comfortable with heavier loads and should not exceed 30% of the child’s bodyweight.

Environmental Illnesses

Dehydration

Children are at greater risk of dehydration than are adults. Because the surface area–to-mass ratio of a child is greater than that of an adolescent or adult, insensible fluid losses through the skin account for a larger percentage of total fluid losses as the size of the child decreases. In addition, the sodium concentration of children’s sweat is generally less than that of adults, leading to a greater relative free water loss. Infants are unable to report thirst, an important marker of fluid deficit, thereby increasing their risk of dehydration. Even once they become verbal, children are often preoccupied and fail to report or meet their need for fluids, even when water is freely available.

Symptoms

As little as a 2% decrease in bodyweight through fluid loss results in mildly increased heart rate, elevated body temperature, and decreased plasma volume. Water losses of 4% to 5% of bodyweight reduce muscular work capacity by 20% to 30%.⁴² Symptoms of dehydration include weakness, fatigue, nausea, vomiting, and, ultimately, lethargy. In a young child, the first sign may be irritability and loss of appetite. Dehydration also predisposes a child to other environmental hazards, such as hypothermia, hyperthermia, and acute mountain sickness.

Treatment

It is the caregiver’s responsibility to provide fluids and coax the child to drink frequently. For short (<2-hour) periods of activity, water is as efficacious a rehydration solution as are carbohydrate-electrolyte drinks.⁴² That being said, a small amount of juice or other sweetener diluted in a larger volume of water will often enhance the fluid intake of a child. Avoid undiluted juices or heavily sweetened drinks because they can worsen dehydration; the high carbohydrate load in these drinks promote an osmotic diuresis. A child eating a normal diet does not require electrolyte replacement unless sweating is prolonged or excessive. By closely monitoring a child’s urine output, fluid deficits can be recognized and promptly managed. A child with decreased urine output or dark, concentrated urine needs extra fluids.

Hypothermia

Children cool more rapidly than do adults because they have a relatively large surface area and often lack the knowledge and judgment to initiate behaviors that maintain warmth in a cold environment (see Chapter 5). In addition, they have a more difficult time, physiologically, maintaining body temperature in cold climates, predominantly because they do not shiver as effectively.⁴ As a result, parents participating in cold weather recreation with children should be able to recognize, treat, and preferably prevent hypothermia and frostbite.

Hypothermia is defined as core body temperature below 35° C (95° F). At this temperature, the body no longer generates enough heat to maintain body functions. The condition is considered mild when the core temperature is 33° to 35° C (91° to 95° F); moderate at temperatures between 28° and 32° C (82° and 90° F), and severe when it is less than 28° C (82° F). The signs and symptoms of hypothermia are listed in Table 99-4, although these may be quite variable. The most important clue to significant hypothermia is altered mental status. An infant may become lethargic and difficult to arouse. An older child may be shivering, stumbling, or appear confused. These signs merit prompt treatment for hypothermia. Of note, the presence or absence of shivering is not a reliable marker of the severity of hypothermia. Physicians should also caution parents that hypothermia can develop at moderate ambient temperatures if adverse climatic conditions are compounded by illness, fatigue, dehydration, inadequate nutrition, or wet clothing.

TABLE 99-4 Signs and Symptoms of Hypothermia *

Rectal Temperature		Signs and Symptoms
Mild	33°-35° C	Sensation of cold, shivering, increased heart rate, progressive incoordination in hand movements, developing poor judgment
Mild	(91°-95° F)
Moderate	28°-32° C	Loss of shivering, difficulty walking or following commands, paradoxical undressing, increasing confusion, decreased arrhythmia threshold
Moderate	(82°-90° F)
Severe	<28° C	Rigid muscles, progressive loss of reflexes and voluntary motion, hypotension, bradycardia, hypoventilation, dilated pupils, increasing risk of fatal arrhythmias, appearance of death
Severe	(<82° F)

* Data from adult subjects.

Prevention

When preparing for cold weather activities, children should dress in layers to allow clothing to be added or subtracted as necessary (Figure 99-6). This avoids excessive perspiration while maintaining warmth. An inner, wicking layer should be followed by a middle, insulating layer and, finally, by an outer, protective layer.

FIGURE 99-6 Layering of clothing for cold environments.

(Courtesy Judith R. Klein, MD.)

Because children generally avail themselves of any opportunity to get wet, clothing that maintains low thermal conductance when moist is particularly important. Conductive heat loss may increase fivefold in wet clothing and up to 25-fold if the child is completely immersed in water. Traditional wool retains warmth when wet because of its unique ability to suspend water vapor within the fibers; however, it is heavier than synthetics and takes much longer to dry. Cotton has a high thermal conductance that increases greatly when wet and is, therefore, a poor choice for wilderness activities in cold weather. Synthetic materials (polypropylene, Capilene, Thermax, Coolmax) wick moisture away from the skin and dry quickly, making them ideal for an inner layer. Finely woven merino wool also provides these same advantages as a wicking layer. The middle, insulating layer may incorporate wool, polyester pile or fleece, down, or similar materials. Finally, windproof and water-resistant outer garments (e.g., Gore-Tex) decrease heat loss from convection and keep children dry. Hats and mittens are also essential; the uncovered head of a child dissipates up to 70% of total body heat production at an ambient temperature of 5° C (41° F).⁴

Treatment

For the hypothermic child, field rewarming begins with limiting further exposure to the cold environment. Find immediate shelter for the child. Wet clothing should be removed, and the child’s head and neck should be protected from further heat loss. Place the child together with a normothermic person in a sleeping bag insulated from the ground to provide external warmth. Hot water bottles, insulated to prevent burns, may also be placed at the axillae, neck, and groin. If the child is alert, oral hydration with warm fluids containing glucose repletes glycogen and corrects dehydration, which frequently accompanies hypothermia. Signs of severe hypothermia dictate immediate evacuation as conditions permit. Rescuers should handle the victim gently to prevent precipitating arrhythmias.

Frostbite

Localized cold injury can result in frostbite (see Chapter 8). Predisposing factors include wet skin, constricting garments that hinder blood circulation, fatigue, dehydration, contact with cold surfaces, and wind. If skin temperature drops below 10° C (50° F), cutaneous sensation is generally abolished and injury may go unnoticed. Skin cooled to −4° C (25° F) freezes.

Frostbite has traditionally been divided into degrees of injury, much like burns. Determination of depth of injury should occur 24 to 48 hours after rewarming; prior to this, frostbitten skin generally appears hard and feels numb. Skin with superficial frostbite is typically swollen, pink or erythematous, painful, somewhat warm, and often blistered. Sites with deep frostbite are cooler, not edematous, pale, anesthetic, and do not have blisters or bullae. In children, frostbite that extends into bone may affect the growth plate and result in skeletal deformities.⁴ Verbal children will frequently report cold hands and feet, but adults should be vigilant about checking the extremities and noses/ears of nonverbal children, particularly those poorly visible in back carriers. A mirror, frequently used, can assist in this regard. Reports of small children developing frostbite and hypothermia while being carried on the backs of adults engaged in outdoor winter pursuits are not infrequent.

Treatment

All wet and constricting clothing should be removed and hypothermia treated aggressively. Rapid rewarming, the primary treatment for frostbite, should be initiated as soon as possible. This is best accomplished by immersion of the frostbitten area in water warmed to 40° to 42° C (104° to 108° F). This narrow temperature range maximizes rewarming speed while preventing thermal burn injuries. Thawing usually takes 30 to 45 minutes and is complete when the skin is soft and pliable. Field rewarming is indicated unless evacuation is imminent and rapid; however, great care should be taken to avoid refreezing. Refreezing causes far more damage than delayed thawing, because of the formation of ice crystals in connective tissue. Vigorous rubbing should also be avoided because it is ineffective and potentially harmful. After thawing, proper wound care is essential. Frostbitten sites should be kept clean, ruptured bullae should be debrided, and the area should be dressed in a bulky dressing. Oral ibuprofen and topical Aloe vera facilitate healing. Evacuation to a medical facility skilled in the management of frostbite is essential.

Hyperthermia

Families participating in wilderness activities in hot climates must take special precautions to avoid heat illnesses (see Chapters 10 and 11). Children do not tolerate the demands of exercise in the heat as well as adults. They generate more heat per kilogram and are less able to disperse heat from the core to the periphery. Parents planning wilderness ventures with children in hot climates can follow some simple guidelines for avoiding heat illness. The most obvious entails reducing the duration and intensity of activities under conditions of high climatic heat stress. The likelihood of heat illness depends on relative humidity, wind velocity, and radiant heat, as well as standard dry-bulb thermometer temperature. Figure 99-7 gives a rough guide for activity levels based on temperature and relative humidity.

FIGURE 99-7 Activity levels based on temperature and relative humidity.

Prevention

Children should be fully hydrated before prolonged exercise and actively encouraged to drink fluids at regular intervals.⁴² Infants and neonates are most vulnerable to heat illness. Under high climatic heat stress, infants fed undiluted cow’s milk or formula may develop marked salt retention and dehydration. They should be given extra water or dilute feedings. The lower osmolar load of breast milk appears to protect against heat illness and hypernatremia.

Because their mechanism of evaporative heat loss (sweating) is immature relative to that of an adult, children should be encouraged to engage in activities in the shade to maximize other means of dissipating heat, such as radiation (skin-to-air gradient). Also, because sweat evaporated from clothing contributes less to cooling than does sweat evaporated from skin, children should be changed out of sweat-soaked clothing and wear dry, lightweight, loose-fitting clothing. As exemplified by cultures that inhabit the desert (e.g., Bedouins of Saudi Arabia), full coverage and lightweight and light-colored clothing provide the most protection from the heat. Finally, children acclimatize to the heat more slowly than do adults, often taking 10 to 14 days to fully adapt. The intensity and duration of exercise should be gradually increased over this period.

Symptoms and Treatment

Early signs and symptoms of heat illness include flushing, tachycardia, weakness/lethargy, mild confusion, headache, and nausea. Vomiting often occurs in children. Sweating may be present or absent and should not be relied on as a clinical indicator of the severity of hyperthermia. If heat illness develops, children should be removed from obvious sources of heat, including direct sunlight, and have their clothing removed. Convective cooling can be increased in the field by vigorous fanning after spraying or sprinkling the victim with water. If available, ice packs or cold compresses placed on the groin, axillae, and scalp will aid cooling. Cool-water immersion is also a very effective means of rapid cooling if the child’s head position can be controlled. If the child is alert, dehydration should be corrected with oral fluids. Progression of symptoms or failure to respond to treatment mandates immediate evacuation.

Sun Damage

Hazards of overexposure to sunlight include sunburn, photoaging, skin cancer, and phototoxic and photoallergic reactions (see Chapter 14). Climatic changes such as global warming and ozone degradation have increased these hazards.⁵⁴ Preventing ultraviolet damage to skin should begin in childhood, as 50% to 80% of a person’s lifetime sun exposure occurs before 21 years of age.^25,⁴⁸ Adolescence is the period when children are most at risk. In one study, 83% of children 12 to 18 years old reported at least one sunburn per summer; 36% reported three or more sunburns per summer.²⁵ Recent evidence suggests that the risk of developing malignant melanoma increases significantly with the number of sunburns in childhood.¹⁹ This risk is even higher if a child is light-skinned with a propensity to burn rather than tan. Tolerance to sun exposure is determined by the amount of melanin in skin and ability of skin to produce melanin in response to sunlight. In general, children have lower melanin levels and thinner skin than do adults and are, therefore, at greater risk of sun damage.

The ultraviolet wavelengths UVA and UVB are principally responsible for the harmful effects of solar radiation. UVB is primarily responsible for suntan and sunburn and also promotes development of skin cancer and skin aging. UVB increases 4% for every 1000-foot (300-m) gain in elevation above sea level. Therefore, a backpacker at 10,000 feet (3050 m) will have a 40% increase in UVB exposure. UVA, which is 10 to 100 times more abundant than UVB, is only 0.001 as potent at inducing sunburn. It is also less affected than is UVB by changes in season or solar zenith angle. UVA is primarily responsible for photosensitivity reactions and solar urticaria. It also contributes to skin cancer and skin aging. A number of drugs often used in adolescence, such as tetracycline, vitamin A derivatives (Retin-A, Accutane), and nonsteroidal antiinflammatory drugs (NSAIDs), increase the risk of photosensitivity reactions and the need for UVA protection. Consequently, it is important to use sunscreens that protect against both UVA and UVB.

The harmful effects of ultraviolet radiation from the sun can be reduced if parents are educated regarding the dangers of sun exposure and encouraged to use sun-protective clothing and sunscreens early in their children’s lives. One study demonstrated 60% reduction in childhood sunburns with good parental role-modeling and sunscreen vigilance.⁴⁸ Regular use of sunscreen with sun protection factor (SPF) of at least 15 for the first 18 years of life reduces a person’s lifetime risk of developing nonmelanoma skin cancer by 78%.²⁷

Prevention

The most effective means of preventing sun damage is use of protective clothing and avoidance of excessive sun exposure. Midday hours, particularly around highly reflective surfaces (e.g., water, sand, snow), at high altitude and at the equator are the most dangerous in terms of quantity of ultraviolet exposure. Shady areas should be used for activities during these times. Hats with wide brims and neck drapes help to protect the face and neck from sun exposure (Figure 99-8). Clothing made from tightly woven fabrics is more protective than is clothing made from loosely woven fabric. For example, loosely woven fabrics, such as those used in most T-shirts, have an SPF of only 5. Most clothing loses more of its sun protective effect when wet. Several manufacturers are marketing high-SPF (25 to 50) protective clothing (http://www.coolibar.com; http://www.sunprotectiveclothing.com). This specialized clothing is cool and lightweight, dries quickly, and can maintain its full SPF capabilities when wet (Figure 99-8). Caution is advised on overcast days, because 80% of the sun’s rays still reach the earth even when the sun is not visible.²⁷ In addition, because clouds filter out heat from infrared rays, children feel more comfortable and tend to stay out longer, therefore increasing their overall UV exposure.

FIGURE 99-8 Child with appropriate sun wear: protective clothing, wide-brimmed hat, and sunglasses.

(Courtesy Judith R. Klein, MD.)

Proper eye protection is often overlooked in infants and young children. Excessive ultraviolet light, particularly during snow and water activities, can result in ultraviolet keratitis (see Chapter 28) with even brief exposures. Properly fitting sunglasses that transmit less than 10% of ultraviolet rays should be part of a child’s outdoor activity armamentarium (Figure 99-8). Side shields and polarizing lenses are particularly important in snow conditions.

Sunscreens

Sunscreens formulated with a variety of different agents to prevent UV damage to the skin include physical blocks, chemical blocks, and antioxidants. Physical blocks, such as zinc oxide and titanium dioxide, reflect ultraviolet light and do not penetrate the skin. Chemical blocks prevent ultraviolet light from entering skin, and are themselves absorbed into skin. Chemical blocks have ingredients that block UVB, UVA, or both. Agents that block UVB include PABA, cinnamates, salicylates, and anthranilates; those that block less potent UVA rays include avobenzone and the anthranilates. Benzophenones, oxybenzone, and the physical blocking agents protect against both UVA and UVB.²⁷ Antioxidants present in sunscreens include Vitamins C and E, resveratrol, and pomegranate. These agents help to repair skin damage. Sunscreens that combine protective ingredients with antioxidants are the most effective. The sun protection factor (SPF) is a measure of a sunscreen’s effectiveness. It is measured in terms of the minimal dose (in length of time) of UV radiation required to cause skin erythema. Sunscreens with SPF 30 or higher provide a superior degree of photoprotection and almost completely prevent cellular changes seen with sunburn.²⁷

Overall, there is little difference between child and adult sunscreens except for price. Parents should select sunscreens based on ingredients. Physical blocks are preferred for children because they are difficult to wash/rub off and do not degrade in the sun. Therefore, they do not need to be reapplied with as great frequency as do chemical sunscreens. Zinc oxide can be quite colorful, whereas titanium dioxide is colorless. Apply a thick coat of sunscreen at least half an hour before outdoor activity. Sunscreens must be applied in adequate quantity to provide the SPF indicated on the bottle.⁵¹ Select a sunscreen with an SPF of at least 15, but preferably greater than 30. Waterproof sunscreens are preferred if children are anywhere near water, because these products maintain efficacy for up to 80 minutes of water immersion. Sunscreens should be reapplied at least every 2 hours (or more frequently) during prolonged water immersion or excessive sweating. Cream and lotion sunscreens provide superior coverage to spray-on formulations because they can be applied evenly and in the quantities required to provide effective sun protection. Infants younger than age 6 months should be outfitted with hats and protective clothing and should placed in the shade. Sunscreens in this age group should be limited to small areas of skin only, because infant skin is thin and chemically sensitive.

Treatment

When sunburn occurs, the mainstays of treatment are cool compresses, topical antipruritics, and NSAIDs. Topical Aloe vera cream or gel often provides a soothing effect for an uncomfortable child. Further sun exposure should be avoided while the skin is healing. As always, prevention is superior to any treatment.

Drowning

According to the Centers for Disease Control, drowning (see Chapter 75) is the number two cause of injury-related death in children, resulting in more than 900 fatalities in children under 14 in 2005.⁶⁶ Of all deaths among children age 1 to 4 years in 2005, 30% were the result of drowning.⁶⁶ Those most at risk are unsupervised toddlers and male teenagers, in particular, those with inadequate swimming skills and poor judgment. Morbidity and mortality result from asphyxiation, hypothermia, and/or trauma.

If a child is pulled from the water after a submersion event, cervical spine precautions should be maintained unless the event is witnessed and no trauma has occurred. All children who have experienced a period of near-drowning should be transported to a hospital for observation, particularly if they demonstrate any sign of distress. If the child is apneic or pulseless, CPR should be initiated immediately and the child transported to an emergency care facility as quickly as possible. All wet clothing should be removed and rewarming initiated. Prognostic assessments based on the initial appearance of the child should not be made in the field, particularly in the setting of cold water immersion. The exception would be in a remote wilderness area, where transport and evacuation times may be extremely long. Survival with good neurologic outcome has been documented in children with prolonged (>40 minutes) submersion in cold water. The emphasis in the field should be on rapid rescue and immediate CPR.

Prevention

Preventive measures are critical to reducing the number of drowning and near-drowning incidents. Most importantly, children should be taught to swim at an early age and should learn to “read” the water and make appropriate judgments regarding water safety. They should be taught to swim with a buddy, particularly in moving and deep water. Young children should always be supervised by an adult skilled in CPR and water rescue. Use of a personal flotation device (PFD) is highly encouraged until the child is a strong swimmer capable of treading water for prolonged periods. Air or foam-filled toys, such as rings or noodles, should not be used in place of PFDs. Cold water, rapidly moving current, water hazards, or large waves should be approached with extreme caution and only by strong swimmers.

High-Altitude Illness

High-altitude illness (see Chapter 1) can be viewed as a continuum from acute mountain sickness (AMS) to life-threatening conditions such as high-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE). AMS usually develops within 24 hours of ascent. The incidence and severity of AMS depend on individual susceptibility, as well as rate of ascent and altitude attained. In one study, 37% of children who ascended rapidly to 3500 m (11,500 feet) developed AMS.⁶ Other studies have shown even higher incidences of AMS in children and have suggested that children are more susceptible to hypobaric hypoxia than are adults.⁴³

Symptoms

The cardinal symptoms of AMS are throbbing headache, anorexia, and malaise. Children are particularly prone to nausea and vomiting. Other symptoms include dizziness and fragmented sleep. Infants may display nonspecific findings such as irritability, poor feeding, and sleep disturbance. As AMS worsens, headaches become more severe and nausea and anorexia progress to vomiting. Dyspnea at rest and confusion/ataxia mark development of the life-threatening conditions HAPE and HACE, respectively.

Prevention

The safest and most effective method of preventing high-altitude illness is to allow for acclimatization via graded ascent. No precise, scientifically proved guidelines exist, given the markedly variable individual susceptibility to altitude illness. However, general recommendations for children (and adults) without altitude experience are listed in Box 99-1. After day trips to higher altitude, children should return to lower altitude to sleep in order to aid acclimatization. The sleeping altitude is particularly important with regard to development of symptoms. A high-carbohydrate diet and plenty of fluids can also help to reduce the risk of high-altitude illness.

BOX 99-1 Preventing High-Altitude Illness

• Avoid abrupt increases of greater than 500 m (1600 feet) in sleeping altitude per night above 2500 m (8000 feet).

• Spend 2 or 3 nights at 2500-3000 m (8000-10,000 feet) before ascending further

• Climb high, sleep low.

• Drink sufficient fluids.

• Eat high-carbohydrate foods.

• Avoid artificial sleep aids (e.g., diphenhydramine).

• Consider using prophylactic acetazolamide.

Acetazolamide has been convincingly shown to reduce the incidence of AMS in adults.²⁰ Pretreatment with this agent mimics the acclimatized state by inducing hyperchloremic metabolic acidosis, allowing for a compensatory increase in respiration. There are no published studies of its efficacy in children, but clinical experience suggests that it is beneficial. The primary indication for acetazolamide prophylaxis in children is a history of recurrent AMS despite graded ascent.⁴³ Acetazolamide is given at 5 mg/kg/day, in two divided doses, up to a maximum daily dosage of 250 mg. It should be started 24 hours before ascent and continued for 3 to 5 days while at maximal altitude. It can be discontinued once descent has begun. Side effects include nausea, mild somnolence, and paresthesias that can be particularly bothersome in children. Dexamethasone also prevents or reduces symptoms of AMS in adults, but its use is discouraged in the prevention of AMS in children, because it masks early symptoms of mountain sickness and thereby encourages continued ascent. Ginkgo biloba has also been studied recently as an herbal alternative to acetazolamide for the prevention of AMS; unfortunately, its efficacy is uncertain because of variability in commercially available gingko formulations.³⁶ Salmeterol, an inhaled long-acting β-agonist, has also been studied as a prophylactic agent against HAPE in adults, but it has not been evaluated in children.