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Heat-related illnesses

Illness related to heat covers a spectrum of complaints, from non life-threatening heat cramps to heat exhaustion to potentially fatal heatstroke.

In a recently published article by the CDC, of 3401 persons who died from a heat-related illness in the US from 1999 to 2003 and for whom age information was available, 7% were less than 15 years of age.

To avoid these medical problems, the importance of prevention and early recognition can not be overemphasized.

Are children at higher risk for heat-related illnesses than adults?

Children are more likely than adults to suffer from heat illness for several reasons, including:

  • fewer sweat glands meaning less sweat production (sweting is needed to lose heat)
  • greater heat production
  • have a body temperature that rises faster during dehydration
  • dependence on others to provide fluids and shade

Are there certain children at a particular risk for heat-related illnesses?


Certain children are particularly susceptible to heat illness and require special attention, including:

  • children younger than 2 years
  • young athletes
  • children who are obese or anorexic
  • children taking certain medications such as antihistamines or drugs of abuse (e.g., cocaine)
  • children with certain underlying medical conditions such as cystic fibrosis or diabetes insipidus

Is it dangerous to leave my child in a locked car for just a brief period of time?

  • In 2003 and 2004, an average of 39 children died from heat stroke each year in the US after being left unattended in a motor vehicle.
  • Previous studies have shown that on days where the outside air temperature has exceeded 86 degrees Fahrenheit, the internal temperatures of the vehicle quickly reached 134 to 154 degrees.

In 2005, an inciteful but alarming research study on heat stress in children from enclosed vehicles was published in the journal Pediatrics.

The purpose of this 2005 study was to see if and how fast the temperatures inside a car rise lower outside temperatures.

The study found the following:

  1. On clear sunny days with the outside air temperature was 72 degrees Fahrenheit, the internal temperature of a vehicle can reach 117 degrees within 1 hour, with 80% of the temperature rise occurring in the first 30 minutes.
  2. Cracking open windows is not effective in decreasing either how quickly the heat rises or the maximum temperature reached in a vehicle.

What causes heat-related illnesses?

The ability of the body to control temperature depends on many factors including:

  1. air temperature
  2. humidity
  3. wind
  4. clothing
  5. medication use
  6. medical conditions
  • Heat-related illness occurs when the body makes more heat  than it is able to lose.
  • For example, when humidity reaches 75% the surrounding air is so saturated that sweat can no longer evaporate (change from a liquid to a vapor), and the body has no means of heat loss left.
  • Increased heat production may be caused by exercise, febrile illness, and certain drugs and substances of abuse.
  • Factors that impair the body’s ability to release heat include heat-retaining clothing such as multilayer and occlusive garments, obesity, dehydration, and skin conditions such as extensive sunburn.
  • Other heated environments that are particularly hazardous to young children are saunas, whirlpools, and hot tubs.

 What are heat cramps?

  • Heat cramps, or muscle cramps, are brief, severe muscle contractions that most often affect the legs and abdomen.
  • Result from too much or too little fluid intake after a lot of sweating
  • Typically, they last for less than a minute, and a hard mass can be palpated in the affected muscle.
  • They may happen at the time of exercise or, more commonly, later when a person is relaxing or taking a shower.
  • Heat cramps themselves are not serious, but the pain may be severe enough to bring the patient to medical attention.

Most importantly, they may be a sign of impending heat exhaustion, especially if they occur during strenuous activity.

What is heat exhaustion?

  • A mild to moderate illness associated with dehydration and a core body temperature ranging from 38 to 40 degrees Celsius (100.4 to 104 Fahrenheit).
  • Symptoms include intense thirst, weakness, nausea/vomiting, confusion, anxiety, dizziness, fainting, and headache.
  • There are two types of heat exhaustion: water depletion, which is more common, and salt depletion.
  • Heat exhaustion caused by water depletion occurs when a child is working, playing, or exercising in a hot environment and does not stop to take in adequate fluids.
    Salt depletion occurs when the child drinks an adequate amount of water, but does not have enough salt replacement.

What is heatstroke?

  • Heatstroke is a life-threatening illness characterized by a core body temperature greater than 40° C (104.0° F) with central nervous system abnormalities (e.g., delirium, seizures, coma) and organ failure (e.g., heart, kidney).
  • It is classified as classic or exertional, although patients may have a combination of both types.
  • Classic heatstroke is seen most often in infants and children with an underlying medical problem or a current febrile illness. The process usually develops slowly, over days, typically during a heat wave.
    Exertional heatstroke commonly occurs in young athletes and military recruits, often at the start of the sport season or the beginning of boot camp, before the patient is adequately conditioned and acclimated.
  • Heatstroke is a life-threatening emergency and must be treated promptly and aggressively.

What is the treatment for heat-related illnesses?

For heat or muscle cramps:

  1. If they occur on a practice field or similar environment, the patient should be moved to a cool place and instructed to rest.
  2. He (or she) should be provided with plenty of cold fluids and salty foods but not with salt tablets.
    Salt tablets are gastric irritants and may lead to nausea and vomiting, which make heat illness worse.

For heat exhaustion:

It is important to recognize, however, that heat exhaustion can lead to heat stroke, so aggressive management is important.

  1. The child must be moved to a cool environment and instructed to rest.
  2. Mild heat exhaustion can be managed in your doctor’s office and treated with oral fluids and salty foods, provided the patient is not vomiting.
  3. More severe symptoms should warrant an ER visit so that lab test can be done and intravenous (IV) fluids can be given.
  4. The child should be instructed to rest and continue adequate fluid intake for 24 to 48 hours after discharge home.

For heat stroke:

Because this is a true medical emergency, a child with signs and symptoms consistent with heatstroke should be immediatedly taken to an ER.

Prior to transport to a hospital, the child should be placed in a cooler environment and have clothing removed, be doused with water and/or have ice packs placed under their arm and to the neck and groin area.

The hospital staff may manage your child in some of the following ways:

  1. Your child may be immersed in an ice water bath depending on the situation.
  2. Continuous monitoring of their body temperature will be done.
  3. Lab tests to check your child’s electrolytes and function of various organs.
  4. Intravenous fluids will be started.
  5. Your child will be admitted to the hospital, typically to an intensive care unit, for close monitoring.

How can heat-related illnesses be prevented?

  1. Your child should reduce the intensity of their activities when temperature and humidity are high. It is best to exercise in the early morning.
  2. To assess the environmental danger and determine when outside activity should be minimized or avoided, see the Heat Index Chart produced by the National Weather Service at http://www.srh.noaa.gov/bmx/tables/heat_index.html or listen out for your local weather forecast.
  3. At the beginning of a strenuous exercise program or after traveling to a hotter environment, a child should be allowed to acclimatize to the new regimen or environment.  Acclimatization should, ideally, occur over 10 to 14 days, once to twice a day, lasting 30 to 45 minutes each.When such a period is not possible, the length of time participants are allowed to participate in practice and competition should be limited.
  4. Children should also be well-hydrated before participating in activities, and periodic drinking should be enforced during activities. It is recommended that for every 20 minutes of exercise, a child weighing 40 kg should drink 5 oz of fluid and a 60-kg adolescent should drink 9 oz.
  5. Water is an acceptable beverage for events lasting less than one hour but, if the event is longer than an hour, fluids containing glucose and electrolytes must be provided.
  6. Clothing should be light-colored and lightweight.  It should also be limited to one layer to facilitate evaporation of sweat.  When clothing becomes saturated with sweat, the child should change into dry garments.
  7. Recognizing all forms of heat-related illness early and treating them aggressively, so that the patient does not progress along the continuum toward heatstroke, is crucial.
  8. Signs and symptoms of heat exhaustion are similar to those that may accompany viral illness, so it is imperative to be alert to the possibility of heat illness in the summer months.
  9. Please, DO NOT LEAVE KIDS IN CARS!
    KIDS AND CARS’ mission is to assure no child dies or is injured in a non-traffic, motor vehicle related event (see http://www.kidsandcars.org/).