Heat illness
Encyclopedia
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.
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.
of greater than 40.6 °C (105.1 °F) in combination with confusion and a lack of sweating.
, 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.
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.
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.
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.
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.
s 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 newspaper
s, magazine
s, blog
s, and other popular media.
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.
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. 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. By sweating and urination, humans lose salts, which need to be replaced along with fluids.
The Occupational Safety and Health Administration in the United States publishes a heat stress Quick Card that contains a checklist designed to help prevent heat stress. This list includes:
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. 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.
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
Thermoregulation
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different...
. This is distinct from a fever
Fever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
, where there is a physiological increase in the temperature set point
Homeostasis
Homeostasis is the property of a system that regulates its internal environment and tends to maintain a stable, constant condition of properties like temperature or pH...
of the body.
Treatment involves rapid mechanical cooling.
Classification
A number of heat illnesses exist including:- Heat stroke - Defined by a body temperature of greater than 40.6 °C (105.1 °F) due to environmental heat exposure with lack of thermoregulationThermoregulationThermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different...
. 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 syncopeHeat syncopeHeat syncope is fainting as a result of overheating . It is another stage in the same process as heat stroke, it occurs under similar conditions, and it is not distinguished from the latter by some authorities...
- Fainting as a result of overheating - Heat edemaEdemaEdema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
- Heat crampsHeat crampsHeat cramps are muscle spasms that result from loss of large amount of salt and water through exercise. Heat cramps are associated with cramping in the abdomen, arms and calves. This can be caused by inadequate consumption of fluids or electrolytes. Frequently, they don't occur until sometime...
- Muscle pains or spasms that happen during heavy exercise in hot weather. - Heat rashRashA rash is a change of the skin which affects its color, appearance or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracked or blistered, swell and may be painful. The causes, and...
- Skin irritation from excessive sweating. - Heat tetanyTetany (medical sign)Tetany is a medical sign consisting of the involuntary contraction of muscles, which may be caused by disease or other conditions that increase the action potential frequency...
- Usually results from short periods of stress in intense heat. Symptoms may include hyperventilation, respiratory problems, numbness or tingling, or muscle spasms.
Sign and symptoms
Heat stroke presents with a hyperthermiaHyperthermia
Hyperthermia is an elevated body temperature due to failed thermoregulation. Hyperthermia occurs when the body produces or absorbs more heat than it can dissipate...
of greater than 40.6 °C (105.1 °F) in combination with confusion and a lack of sweating.
Causes
Substances that inhibit cooling and cause dehydration such as alcoholAlcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
, caffeine
Caffeine
Caffeine is a bitter, white crystalline xanthine alkaloid that acts as a stimulant drug. Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants...
, 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.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
Leash
A leash is a rope or similar material attached to the neck or head of an animal for restraint or control...
outside the destination and provided with a full water bowl.
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.
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.
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.
Forgotten baby syndrome
Forgotten baby syndrome (FBS) is a pseudo-medical term for the danger of adult caregiverCaregiver
Caregiver may refer to:* Caregiver or carer - an unpaid person who cares for someone requiring support due to a disability, frailty, mental health problem, learning disability or old age...
s forgetting about the presence of a child and consequently subjecting the child to danger. In spite of the word "syndrome
Syndrome
In medicine and psychology, a syndrome is the association of several clinically recognizable features, signs , symptoms , phenomena or characteristics that often occur together, so that the presence of one or more features alerts the physician to the possible presence of the others...
" this is not a recognized medical condition; however the term has achieved some currency in newspaper
Newspaper
A newspaper is a scheduled publication containing news of current events, informative articles, diverse features and advertising. It usually is printed on relatively inexpensive, low-grade paper such as newsprint. By 2007, there were 6580 daily newspapers in the world selling 395 million copies a...
s, magazine
Magazine
Magazines, periodicals, glossies or serials are publications, generally published on a regular schedule, containing a variety of articles. They are generally financed by advertising, by a purchase price, by pre-paid magazine subscriptions, or all three...
s, blog
Blog
A blog is a type of website or part of a website supposed to be updated with new content from time to time. Blogs are usually maintained by an individual with regular entries of commentary, descriptions of events, or other material such as graphics or video. Entries are commonly displayed in...
s, and other popular media.
Prevention
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. Temperatures that high without proper cooling could be dangerous and even fatal, especially with young children and pets.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.
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. A better indicator is the color of urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
. 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
Hyponatremia
Hyponatremia is an electrolyte disturbance in which the sodium concentration in the serum is lower than normal. In the vast majority of cases, hyponatremia occurs as a result of excess body water diluting the serum sodium and is not due to sodium deficiency. Sodium is the dominant extracellular...
, or low sodium, which can cause sudden death from heart attack. By sweating and urination, humans lose salts, which need to be replaced along with fluids.
The Occupational Safety and Health Administration in the United States publishes a heat stress Quick Card 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
Treatment involves rapid mechanical cooling along with standard resuscitation measures.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
Torso
Trunk or torso is an anatomical term for the central part of the many animal bodies from which extend the neck and limbs. The trunk includes the thorax and abdomen.-Major organs:...
, head, neck, and groin
Groin
In human anatomy, the groin areas are the two creases at the junction of the torso with the legs, on either side of the pubic area. This is also known as the medial compartment of the thigh. A pulled groin muscle usually refers to a painful injury sustained by straining the hip adductor muscles...
will help cool the victim. A fan or dehumidifying air conditioning
Air conditioning
An air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle...
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
Vasoconstriction
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...
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
Sports drink
A sports drink beverage is designed to help athletes rehydrate when fluids are depleted after training or competition. Electrolyte replacement promotes proper rehydration, which is important in delaying the onset of fatigue during exercise...
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. 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
Cardiac arrest
Cardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...
.
The patient should be placed into the recovery position
Recovery position
The recovery position refers to one of a series of variations on a lateral recumbent or three-quarters prone position of the body, in to which an unconscious but breathing casualty can be placed as part of first aid treatment.An unconscious person The recovery position refers to one of a series of...
to ensure that the airway
Airway
The pulmonary airway comprises those parts of the respiratory system through which air flows, conceptually beginning at the nose and mouth, and terminating in the alveoli...
remains open.