Heat illness

Heat illness
Heat stroke
Classification and external resources
ICD-10 T67.0
ICD-9 992.0
DiseasesDB 5690
MedlinePlus 000056
eMedicine med/956
MeSH D018883
Heat exhaustion
Classification and external resources
ICD-10 T67.3- T67.5
ICD-9 992.3-992.5
DiseasesDB 5690
eMedicine emerg/236
MeSH D006359

Heat illness or heat-related illness is a spectrum of disorders due to environmental heat exposure. It includes minor conditions such as heat cramps, heat syncope, and heat exhaustion as well as the more severe condition known as heat stroke.[1] Heat stroke is defined as a body temperature of greater than 40.6 °C (105.1 °F) due to environmental heat exposure with lack of thermoregulation. This is distinct from a fever, where there is a physiological increase in the temperature set point of the body.

Treatment involves rapid mechanical cooling.



A number of heat illnesses exist including[2][3]:

  • Heat stroke - Defined by a body temperature of greater than 40.6 °C (105.1 °F) due to environmental heat exposure with lack of thermoregulation. Symptoms include dry skin, rapid, strong pulse and dizziness.
  • Heat exhaustion - Can be a precursor of heatstroke; the symptoms include heavy sweating, rapid breathing and a fast, weak pulse.
  • Heat syncope - Fainting as a result of overheating
  • Heat edema
  • Heat cramps - Muscle pains or spasms that happen during heavy exercise in hot weather.
  • Heat rash - Skin irritation from excessive sweating.
  • Heat tetany - Usually results from short periods of stress in intense heat. Symptoms may include hyperventilation, respiratory problems, numbness or tingling, or muscle spasms.[4]

Sign and symptoms

Heat stroke presents with a hyperthermia of greater than 40.6 °C (105.1 °F) in combination with confusion and a lack of sweating.[5]


Substances that inhibit cooling and cause dehydration such as alcohol, caffeine, stimulants, medications, and age-related physiological changes predispose to so-called "classic" heat stroke. Exertional heat stroke can happen in young people without health problems or medications, most often in athletes and military recruits.

Children and pets in cars

Children, elderly adults, or disabled individuals left alone in a vehicle are at particular risk of succumbing to heat stroke, even with windows partially open. As these groups of individuals may not be able to express discomfort verbally (or audibly, inside a closed car), their plight may not be immediately noticed by others in the vicinity. A stuffed toy or other child's toy is recommended for a parent or guardian to keep with himself or herself in the front seat as a reminder that at least one child is present. For larger groups, checking the van or bus for stragglers at the end of the trip is essential, complemented by other procedures such as a head count.[6]

Pets are even more susceptible than humans to heat stroke in cars, as dogs (the animals usually involved), cats and many other animals cannot produce whole body sweat. Non-guide dogs are prohibited from being brought into many establishments, and opening a vehicle window sufficiently may present an escape opportunity or bite hazard. Leaving the pet at home with plenty of water on hot days is recommended instead, or, if a dog must be brought along, tied up outside the destination and provided with a full water bowl.[7]

Between 1998 and 2011, at least 500 children in the United States died from being inside hot cars, and 75% of them were less than 2 years old. When the outside temperature is 70 degrees Fahrenheit, the temperature inside the car can exceed 120 degrees, even when the windows are partially open.[8]

Legal prosecution of parents in this situation varies greatly, even within the same jurisdiction. For example, in Mt. Laurel, New Jersey, after a college professor and a horse trainer each unintentionally killed their child in a hot car, the college professor was never prosecuted, but the horse trainer was sentenced to 20 years in prison.[9]

Among all child deaths in hot cars, slightly more than half occur because parents forget that the child is in the car, 18% happen after parents intentionally leave the child in a car without understanding how hot it can get, and 30% happen after the child had climbed into the car to play.[10]

Forgotten baby syndrome

Forgotten baby syndrome (FBS) is a pseudo-medical term for the danger of adult caregivers forgetting about the presence of a child and consequently subjecting the child to danger. In spite of the word "syndrome" this is not a recognized medical condition; however the term has achieved some currency in newspapers, magazines, blogs, and other popular media.[11][12]


The risk of heatstroke can be reduced by observing precautions to avoid overheating and dehydration. Light, loose-fitting clothing will allow perspiration to evaporate and cool the body. Wide-brimmed hats in light colours keep the sun from warming the head and neck and block the powerful radiation from hurting the eyes; vents on a hat will allow perspiration to cool the head. Strenuous exercise should be avoided during daylight hours in hot weather; so should remaining in enclosed spaces (such as automobiles). The temperature inside cars can reach 200°F (c. 93°C) at the right exterior temperature, sunlight, color of vehicle, and type of vehicle.[13] Temperatures that high without proper cooling could be dangerous and even fatal, especially with young children and pets.[14]

In environments that are not only hot but also humid, it is important to recognize that humidity reduces the degree to which the body can lose heat by evaporation. In such environments, it helps to wear light clothing such as cotton in light colors, that is pervious to sweat but impervious to radiant heat from the sun. This minimises the gaining of radiant heat, while allowing as much evaporation to occur as the environment will allow. Clothing such as plastic fabrics that are impermeable to sweat and thus do not facilitate heat loss through evaporation can actually contribute to heat stress.[15]

In hot weather people need to drink plenty of liquids to replace fluids lost from sweating. Thirst is not a reliable sign that a person needs fluids.[16] A better indicator is the color of urine. A dark yellow color may indicate dehydration. It is debated whether water or sports drinks are more effective to regain fluids; however, drinking only water without ingesting any salts will lead to a condition known as hyponatremia, or low sodium, which can cause sudden death from heart attack.[citation needed] By sweating and urination, humans lose salts, which need to be replaced along with fluids.[citation needed] The Occupational Safety and Health Administration in the United States publishes a heat stress Quick Card [17] that contains a checklist designed to help prevent heat stress. This list includes:

  • Known signs/symptoms of heat-related illnesses
  • Block out direct sun or other heat sources
  • Use cooling fans/air-conditioning; rest regularly
  • Drink sufficient water
  • Wear lightweight, light colored, loose-fitting clothes
  • Avoid alcohol, caffeinated drinks, or heavy meals


Treatment involves rapid mechanical cooling along with standard resuscitation measures.[18]

The body temperature must be lowered immediately. The patient should be moved to a cool area (indoors, or at least in the shade) and clothing removed to promote heat loss (passive cooling). Active cooling methods may be used: The person is bathed in cool water or a hypothermia vest can be applied. However, wrapping the patient in wet towels or clothes can actually act as insulation and increase the body temperature. Cold compresses to the torso, head, neck, and groin will help cool the victim. A fan or dehumidifying air conditioning unit may be used to aid in evaporation of the water (evaporative method).

Immersing a patient into a bathtub of cool (but not cold) water (immersion method) is a recognized method of cooling. This method requires the effort of 4-5 people and the patient should be monitored carefully during the treatment process. Immersion should be avoided for an unconscious patient, but if there is no alternative, the patient's head must be held above water. Immersion in very cold water is counterproductive, as it causes vasoconstriction in the skin and thereby prevents heat from escaping the body core.

Hydration is of paramount importance in cooling the patient. This is achieved by drinking water (oral rehydration). Commercial isotonic drinks may be used as a substitute. Intravenous hydration (via a drip) is necessary if the patient is confused, unconscious, or unable to tolerate oral fluids.

Alcohol rubs will cause further dehydration and impairment of consciousness and should be avoided.[clarification needed] The patient's condition should be reassessed and stabilized by trained medical personnel. The patient's heart rate and breathing should be monitored, and CPR may be necessary if the patient goes into cardiac arrest.

The patient should be placed into the recovery position to ensure that the airway remains open.


  1. ^ Lugo-Amador, NM; Rothenhaus, T, Moyer, P (2004 May). "Heat-related illness.". Emergency medicine clinics of North America 22 (2): 315–27, viii. PMID 15163570. 
  2. ^ Tintinalli, Judith (2004). Emergency Medicine: A Comprehensive Study Guide (6th ed.). McGraw-Hill Professional. p. 1186. ISBN 0071388753. 
  3. ^ http://www.nlm.nih.gov/medlineplus/heatillness.html
  4. ^ http://www.revolutionhealth.com/articles/heat-tetany/tw9489
  5. ^ McGugan EA (March 2001). "Hyperpyrexia in the emergency department". Emerg Med (Fremantle) 13 (1): 116–20. doi:10.1046/j.1442-2026.2001.00189.x. PMID 11476402. 
  6. ^ Extreme Heat Guide, Centers for Disease Control and Prevention (CDC)
  7. ^ http://www.paw-rescue.org/PAW/PETTIPS/DogTip_HotCars.php
  8. ^ Heat danger: 500th child dies in a hot car, Consumer Reports, June 3, 2011
  9. ^ Court outcomes vary when kids die in hot cars, Associated Press, 2011
  10. ^ More kids die in hot cars, half because parents forget them, USA Today, June 30, 2010
  11. ^ Weingarten, Gene (March 8, 2009). "Forgetting a child in the back seat of a hot, parked car is a horrifying, inexcusable mistake. But is it a crime?". Washington Post. http://www.washingtonpost.com/wp-dyn/content/article/2009/02/27/AR2009022701549.html. Retrieved May 2, 2010. 
  12. ^ "The Last Word: Forgotten Baby Syndrome". The Week. March 26, 2009. http://www.theweek.com/article/index/94741/The_last_word_Forgotten_baby_syndrome. 
  13. ^ http://phoenix.about.com/od/car/a/summercar.htm
  14. ^ "Avoiding Classic Heat Stroke", Institute for Good Medicine at the Pennsylvania Medical Society
  15. ^ Guyton, Arthur. (1976) Textbook of Medical Physiology. (5th ed). Philadelphia: W.B. Saunders.
  16. ^ Working in Hot Environments. National Institute for Occupational Safety and Health, 1992. NIOSH Publication No. 86-112. Accessed May 21, 2009.
  17. ^ http://www.osha.gov/Publications/osha3154.html
  18. ^ Tintinalli, Judith (2004). Emergency Medicine: A Comprehensive Study Guide (6th ed.). McGraw-Hill Professional. p. 1188. ISBN 0071388753. 

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