Chapter 140

• Children are more susceptible to extremes of temperature because of a greater area-to-body mass ratio, higher metabolic heat per mass unit, and a diminished ability to dissipate body heat by evaporation.
• Heat-related illnesses comprise a continuum of conditions ranging from minor entities such as heat cramps to more serious conditions including heat exhaustion and heatstroke. Heatstroke is the most severe form of heat illness, with reported mortality between 17% and 80%
• Heat exhaustion is a syndrome of dizziness, postural hypotension, nausea, vomiting, headache, weakness, and, occasionally, syncope, which may be associated with normal temperature or moderate temperature elevation (39°C–41.1°C). One hallmark is the absence of mental status changes.
• Heatstroke is a state of complete thermoregulatory failure and is an immediately life-threatening entity requiring aggressive management. Patients with heatstroke present with disorientation, seizures, or coma. After assessment and stabilization of the airway, breathing, and circulation, cooling should be instituted immediately, usually by spraying the skin with room-temperature water and directing an electric fan onto the patient's skin.
• The core temperature defines the presence and severity of hypothermia. Most thermometers for routine clinical use will record a temperature down to only 34.4°C. Special glass or electronic thermometers are required for accurate measurement of temperatures in hypothermic patients.
• Shivering will often be present in the older child or adolescent but ceases by the time the temperature reaches 31°C. The skin is typically cold, firm, pale, or mottled, and localized damage due to frostbite may be present.
• In moderate-to-severe cases of hypothermia, active rewarming is started as soon as possible. Heated, humidified oxygen and intravenous fluids heated to 40°C have been shown to be safe and efficacious and are used from the beginning.
• Extracorporeal rewarming is the most rapid method of rewarming and is indicated in hypothermic cardiac arrest and with patients who present with completely frozen extremities. Using this technique, young, otherwise healthy people have survived deep hypothermia with no or minimal cerebral impairment.

The spectrum of heat illness varies from mild, self-limited problems, such as heat cramps, to major, life-threatening problems, such as heatstroke. The annual average number of deaths from heat illness in the United States for 1999 through 2003 was 688, almost doubled from previous decades.1 Infants are predisposed to the development of heat illness due to their poorly developed thermoregulatory systems.2 Older children and adolescents are susceptible to heat illness when they exercise vigorously under hot, humid conditions.3 Exercising children have a reduced ability to dissipate body heat because of a lesser sweating capacity.3 Adolescent zeal for competitive athletics, coupled with an often-held belief among the young in their invulnerability, can lead to serious heat illness. A major contributing factor is acclimatization.4 Acclimatization to a hot, humid environment allows the individual to perform harder and longer without developing heat illness.4 The rate of acclimatization for pediatric patients is much slower than that of adults. Full acclimatization takes 3 to 4 weeks, during which the individual must limit ...

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