Heat stroke

Heat stroke generally presents with a hyperthermia of greater than {{convert|40.6|C|F}} in combination with disorientation.{{cite journal | vauthors = Epstein Y, Yanovich R | title = Heatstroke | journal = The New England Journal of Medicine | volume = 380 | issue = 25 | pages = 2449–2459 | date = June 2019 | pmid = 31216400 | doi = 10.1056/NEJMra1810762 | doi-access = free }}{{cite journal | vauthors = McGugan EA | title = Hyperpyrexia in the emergency department | journal = Emergency Medicine | volume = 13 | issue = 1 | pages = 116–120 | date = March 2001 | pmid = 11476402 | doi = 10.1046/j.1442-2026.2001.00189.x }} There is generally a lack of sweating in classic heatstroke, while sweating is generally present in exertional heatstroke.

Early symptoms of heat stroke include behavioral changes, confusion, delirium, dizziness, weakness, agitation, combativeness, slurred speech, nausea, and vomiting. In some individuals with exertional heatstroke, seizures and sphincter incontinence have also been reported. Additionally, in exertional heat stroke, the affected person may sweat excessively.{{cite web |url=https://www.cdc.gov/niosh/docs/2011-174/pdfs/2011-174.pdf |title=InfoSheet: Protecting Workers from Heat Illness |publisher=OSHA–NIOSH |date=2011 |access-date=February 10, 2015 |url-status=live |archive-url=https://web.archive.org/web/20150616084925/http://www.cdc.gov/niosh/docs/2011-174/pdfs/2011-174.pdf |archive-date=June 16, 2015 |df=mdy-all }} Rhabdomyolysis, which is characterized by skeletal muscle breakdown with the products of muscle breakdown entering the bloodstream and causing organ dysfunction, is seen with exertional heatstroke.

If treatment is delayed, patients could develop vital organ damage, unconsciousness and even organ failure. In the absence of prompt and adequate treatment, heatstroke can be fatal.{{cite book |author=Fauci, Anthony|title=Harrison's Principles of Internal Medicine |edition=17th |publisher=McGraw-Hill Professional |date=2008 |isbn=978-0-07-146633-2 |pages=117–121|display-authors=etal|title-link=Harrison's Principles of Internal Medicine }}

{{see also|Hyperthermia#Causes}}

Heat stroke occurs when thermoregulation is overwhelmed by a combination of excessive metabolic production of heat (exertion), excessive heat in the physical environment, and insufficient or impaired heat loss, resulting in an abnormally high body temperature. Substances that inhibit cooling and cause dehydration such as alcohol, stimulants, medications, and age-related physiological changes predispose to so-called "classic" or non-exertional heat stroke (NEHS), most often in elderly and infirm individuals in summer situations with insufficient ventilation.{{Cite web|title = Heat emergencies: MedlinePlus Medical Encyclopedia|url = https://www.nlm.nih.gov/medlineplus/ency/article/000056.htm|website = www.nlm.nih.gov|access-date = 2016-01-19|url-status = live|archive-url = https://web.archive.org/web/20160105060818/https://www.nlm.nih.gov/medlineplus/ency/article/000056.htm|archive-date = January 5, 2016|df = mdy-all}}

Young children have age specific physiologic differences that make them more susceptible to heat stroke including an increased surface area to mass ratio (leading to increased environmental heat absorption), an underdeveloped thermoregulatory system, a decreased sweating rate and a decreased blood volume to body size ratio (leading to decreased compensatory heat dissipation by redirecting blood to the skin).

Exertional heat stroke (EHS) can happen in young people without health problems or medications{{snd}} most often in athletes, outdoor laborers, or military personnel engaged in strenuous hot-weather activity or in first responders wearing heavy personal protective equipment. 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 cool itself by perspiration and evaporation. For humans and other warm-blooded animals, excessive body temperature can disrupt enzymes regulating biochemical reactions that are essential for cellular respiration and the functioning of major organs.

{{see also|Forgotten baby syndrome}}

When the outside temperature is {{convert|21|C|F}}, the temperature inside a car parked in direct sunlight can quickly exceed {{convert|49|C|F}}. Young children or elderly adults left alone in a vehicle are at particular risk of succumbing to heat stroke. "Heat stroke in children and in the elderly can occur within minutes, even if a car window is opened slightly."{{Cite journal|url = http://go.galegroup.com/ps/i.do?id=GALE%7CA116734855&v=2.1&it=r&p=AONE&sw=w&asid=5ea3436f092cfd2b9740e6d9a3b7d2e8|title = A primer on summer safety| vauthors = Meadows M |date = 2014|journal = Academic OneFile|access-date = January 18, 2016|url-status = live|archive-url = https://web.archive.org/web/20161005095654/http://go.galegroup.com/ps/i.do?id=GALE%7CA116734855&v=2.1&u=pcc&it=r&p=AONE&sw=w&asid=5ea3436f092cfd2b9740e6d9a3b7d2e8|archive-date = October 5, 2016|df = mdy-all}} As these groups of individuals may not be able to open car doors or to express discomfort verbally (or audibly, inside a closed car), their plight may not be immediately noticed by others in the vicinity. In 2018, 51 children in the United States died in hot cars, more than the previous high of 49 in 2010.{{Cite web|url=https://www.nsc.org/in-the-newsroom/2018-was-deadliest-year-on-record-for-hot-car-deaths|title=2018 was Deadliest Year on Record for Hot Car Deaths|website=National Safety Council|language=en-US|access-date=2019-07-08}}

Dogs are even more susceptible than humans to heat stroke in cars, as they cannot produce whole-body sweat to cool themselves. Leaving the dog at home with plenty of water on hot days is recommended instead, or, if a dog must be brought along, it can be tied up in the shade outside the destination and provided with a full water bowl.{{cite web |url=http://www.paw-rescue.org/PAW/PETTIPS/DogTip_HotCars.php |title=Dogs in Hot Cars |publisher=Partnership for Animal Welfare |access-date=February 11, 2015 |url-status=dead |archive-url=https://web.archive.org/web/20150210200108/http://www.paw-rescue.org/PAW/PETTIPS/DogTip_HotCars.php |archive-date=February 10, 2015 |df=mdy-all }}

The pathophysiology of heat stroke involves an intense heat overload followed by a failure of the body's thermoregulatory mechanisms. More specifically, heat stroke leads to inflammatory and coagulation responses that can damage the vascular endothelium and result in numerous platelet complications, including decreased platelet counts, platelet clumping, and suppressed platelet release from bone marrow.{{cite journal | vauthors = Hifumi T, Kondo Y, Shimizu K, Miyake Y | title = Heat stroke | journal = Journal of Intensive Care | volume = 6 | pages = 30 | date = 2018 | pmid = 29850022 | pmc = 5964884 | doi = 10.1186/s40560-018-0298-4 | doi-access = free }}

Growing evidence also suggests the existence of a second pathway underlying heat stroke that involves heat and exercise-driven endotoxemia.{{cite journal | vauthors = Lim CL | title = Heat Sepsis Precedes Heat Toxicity in the Pathophysiology of Heat Stroke-A New Paradigm on an Ancient Disease | journal = Antioxidants | volume = 7 | issue = 11 | page = 149 | date = October 2018 | pmid = 30366410 | pmc = 6262330 | doi = 10.3390/antiox7110149 | doi-access = free }} Although its exact mechanism is not yet fully understood, this model theorizes that extreme exercise and heat disrupt the intestinal barrier by making it more permeable and allowing lipopolysaccharides (LPS) from gram-negative bacteria within the gut to move into the circulatory system. High blood LPS levels can then trigger a systemic inflammatory response and eventually lead to sepsis and related consequences like blood coagulation, multi-organ failure, necrosis, and central nervous system dysfunction.

Heat stroke is a clinical diagnosis, based on signs and symptoms. It is diagnosed based on an elevated core body temperature (usually above 40 degrees Celsius), a history of heat exposure or physical exertion, and neurologic dysfunction. However, high body temperature does not necessarily indicate that heat stroke is present, such as with people in high-performance endurance sports or with people experiencing fevers.{{cite journal | vauthors = Laitano O, Leon LR, Roberts WO, Sawka MN | title = Controversies in exertional heat stroke diagnosis, prevention, and treatment | journal = Journal of Applied Physiology | volume = 127 | issue = 5 | pages = 1338–1348 | date = November 2019 | pmid = 31545156 | doi = 10.1152/japplphysiol.00452.2019 | doi-access = free }} In others with heatstroke, the core body temperature is not always above 40 degrees Celsius. Therefore, heat stroke is more accurately diagnosed based on a constellation of symptoms rather than just a specific temperature threshold. Tachycardia (or a rapid heart rate), tachypnea (rapid breathing) and hypotension (low blood pressure) are common clinical findings. Those with classic heat stroke usually have dry skin, whereas those with exertional heat stroke usually have wet or sweaty skin.

A core body temperature (such as a rectal temperature) is the preferred method for monitoring body temperature in the diagnosis and management of heat stroke as it is more accurate than peripheral body temperatures (such as an oral or axillary temperatures).

Other conditions which may present similarly to heat stroke include meningitis, encephalitis, epilepsy, drug toxicity, severe dehydration, and certain metabolic syndromes such as serotonin syndrome, neuroleptic malignant syndrome, malignant hyperthermia and thyroid storm.

The risk of heat stroke can be reduced by observing precautions to avoid overheating and dehydration. Light, loose-fitting clothes will allow perspiration to evaporate and cool the body. Wide-brimmed hats in light colors help prevent the sun from warming the head and neck. Vents on a hat will help cool the head, as will sweatbands wetted with cool water. Strenuous exercise should be avoided during hot weather, especially in the sun peak hours. Strenuous exercise should also be avoided if a person is ill and exercise intensity should match one's fitness level. Avoiding confined spaces (such as automobiles) without air-conditioning or adequate ventilation.{{Cite web |date=2022-08-16 |title=Tips for Preventing Heat-Related Illness Natural Disasters and Severe Weather |url=https://www.cdc.gov/disasters/extremeheat/heattips.html |access-date=2023-09-20 |website=www.cdc.gov |language=en-us}}{{Cite journal |last1=Gauer |first1=Robert |last2=Meyers |first2=Bryce K. |date=2019-04-15 |title=Heat-Related Illnesses |url=https://pubmed.ncbi.nlm.nih.gov/30990296 |journal=American Family Physician |volume=99 |issue=8 |pages=482–489 |issn=1532-0650 |pmid=30990296}}

During heat waves and hot seasons further measures that can be taken to avoid classic heat stroke include staying in air conditioned areas, using fans, taking frequent cold showers, and increasing social contact and well being checks (especially for the elderly or disabled persons).

In hot weather, people need to drink plenty of cool liquids and mineral salts 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.

Some measures that can help protect workers from heat stress include:{{cite web |url=http://www.osha.gov/Publications/osha3154.pdf |title=QuickCard: Protecting Workers from Heat Stress |publisher=OSHA |date=2014 |access-date=February 10, 2015 |url-status=live |archive-url=https://web.archive.org/web/20150117222652/https://www.osha.gov/Publications/osha3154.pdf |archive-date=January 17, 2015 |df=mdy-all }}

• Know signs/symptoms of heat-related illnesses.
• Block out direct sun and other heat sources.
• Drink fluids often, and before you are thirsty.
• Wear lightweight, light-colored, loose-fitting clothes.
• Avoid beverages containing alcohol or caffeine.

Treatment of heat stroke involves rapid mechanical cooling along with standard resuscitation measures.{{cite book |title=Emergency Medicine: A Comprehensive Study Guide | edition =6th |last=Tintinalli |first=Judith |year=2004 |publisher=McGraw-Hill Professional |isbn=0-07-138875-3 |page=1188 }}

The body temperature must be lowered quickly via conduction, convection, or evaporation. During cooling, the body temperature should be lowered to less than 39 degrees Celsius, ideally less than 38-38.5 degrees Celsius.

In the field, the person should be moved to a cool area, such as indoors or to a shaded area. Clothing should be removed to promote heat loss through passive cooling. Conductive cooling methods such as ice-water immersion should also be used, if possible. Evaporative and convective cooling by a combination of cool water spray or cold compresses with constant air flow over the body, such as with a fan or air-conditioning unit, is also an effective alternative.

In hospital mechanical cooling methods include ice water immersion, infusion of cold intravenous fluids, placing ice packs or wet gauze around the person, and fanning. Aggressive ice-water immersion remains the gold standard for exertional heat stroke and may also be used for classic heat stroke.{{cite journal | vauthors = McDermott BP, Casa DJ, Ganio MS, Lopez RM, Yeargin SW, Armstrong LE, Maresh CM | title = Acute whole-body cooling for exercise-induced hyperthermia: a systematic review | journal = Journal of Athletic Training | volume = 44 | issue = 1 | pages = 84–93 | date = 2009-01-01 | pmid = 19180223 | pmc = 2629045 | doi = 10.4085/1062-6050-44.1.84 }}{{cite journal | vauthors = Gagnon D, Lemire BB, Casa DJ, Kenny GP | title = Cold-water immersion and the treatment of hyperthermia: using 38.6°C as a safe rectal temperature cooling limit | journal = Journal of Athletic Training | volume = 45 | issue = 5 | pages = 439–444 | date = 2010-09-01 | pmid = 20831387 | pmc = 2938313 | doi = 10.4085/1062-6050-45.5.439 }} This method may require the effort of several people and the person should be monitored carefully during the treatment process. Immersion should be avoided for an unconscious person but, if there is no alternative, it can be applied with the person's head above water. A rapid and effective cooling usually reverses concomitant organ dysfunction.

Immersion in very cold water was once thought to be counterproductive by reducing blood flow to the skin and thereby preventing heat from escaping the body core. However, research has shown that this mechanism does not play a dominant role in the decrease in core body temperature brought on by cold water.{{Citation needed|date=April 2024}}

Dantrolene, a muscle relaxant used to treat other forms of hyperthermia, is not an effective treatment for heat stroke.{{cite journal | vauthors = Laitano O, Murray KO, Leon LR | title = Overlapping Mechanisms of Exertional Heat Stroke and Malignant Hyperthermia: Evidence vs. Conjecture | journal = Sports Medicine | volume = 50 | issue = 9 | pages = 1581–1592 | date = September 2020 | pmid = 32632746 | doi = 10.1007/s40279-020-01318-4 | s2cid = 220351326 }} Antipyretics such as aspirin and acetaminophen are also not recommended as a means to lower body temperature in the treatment of heat stroke and their use may lead to worsening liver damage.

A cardiopulmonary resuscitation (CPR) may be necessary if the person goes into cardiac arrest.

The person's condition should be reassessed and stabilized by trained medical personnel. And the person's heart rate and breathing should be monitored. IV fluid resuscitation is usually needed for circulatory failure and organ dysfunction and is also indicated if rhabdomyolysis is present. In severe cases hemodialysis and ventilator support may be needed.

In elderly people who experience classic heat stroke the mortality exceeds 50%. The mortality rate in exertional heat stroke is less than 5%.

It was long believed that heat strokes lead only rarely to permanent deficits and that convalescence is almost complete. However, following the 1995 Chicago heat wave, researchers from the University of Chicago Medical Center studied all 58 patients with heat stroke severe enough to require intensive care at 12 area hospitals between July 12 and 20, 1995, ranging in age from 25 to 95 years. Nearly half of these patients died within a year{{snd}} 21 percent before and 28 percent after release from the hospital. Many of the survivors had permanent loss of independent function; one-third had severe functional impairment at discharge, and none of them had improved after one year. The study also recognized that because of overcrowded conditions in all the participating hospitals during the crisis, the immediate care{{snd}} which is critical{{snd}} was not as comprehensive as it should have been.{{cite web |url=http://www.uchospitals.edu/news/1998/19980801-heatstroke-aim.html |title=Classic heat stroke during Chicago 1995 heat wave |publisher=University of Chicago Medicine |date=August 1, 1998 |access-date=July 22, 2012 |url-status=live |archive-url=https://web.archive.org/web/20120604114740/http://www.uchospitals.edu/news/1998/19980801-heatstroke-aim.html |archive-date=June 4, 2012 |df=mdy-all }}

In rare cases, brain damage has been reported as a permanent sequela of severe heat stroke, most commonly cerebellar atrophy.{{cite journal | vauthors = Bouchama A, Knochel JP | title = Heat stroke | journal = The New England Journal of Medicine | volume = 346 | issue = 25 | pages = 1978–1988 | date = June 2002 | pmid = 12075060 | doi = 10.1056/NEJMra011089 }}{{cite journal | vauthors = Bazille C, Megarbane B, Bensimhon D, Lavergne-Slove A, Baglin AC, Loirat P, Woimant F, Mikol J, Gray F | display-authors = 6 | title = Brain damage after heat stroke | journal = Journal of Neuropathology and Experimental Neurology | volume = 64 | issue = 11 | pages = 970–975 | date = November 2005 | pmid = 16254491 | doi = 10.1097/01.jnen.0000186924.88333.0d | doi-access = free }}

Various aspects can affect the incidence of heat stroke, including sex, age, geographical location, and occupation. The incidence of heat stroke is higher among men; however, the incidence of other heat illnesses is higher among women. The incidence of other heat illnesses in women compared with men ranged from 1.30 to 2.89 per 1000 person-years versus 0.98 to 1.98 per 1000 person-years.{{cite journal | vauthors = Alele F, Malau-Aduli B, Malau-Aduli A, Crowe M | title = Systematic review of gender differences in the epidemiology and risk factors of exertional heat illness and heat tolerance in the armed forces | journal = BMJ Open | volume = 10 | issue = 4 | pages = e031825 | date = April 2020 | pmid = 32265238 | pmc = 7245403 | doi = 10.1136/bmjopen-2019-031825 }}

Different parts of the world also have different rates of heat stroke.{{Medical citation needed|date=December 2021}}

During the 2003 European heatwave more than 70,000 people died of heat related illnesses, and during the 2022 European heatwave, 61,672 people died from heat related illnesses.{{cite journal |last1=Ballester |first1=Joan |last2=Quijal-Zamorano |first2=Marcos |last3=Méndez Turrubiates |first3=Raúl Fernando |last4=Pegenaute |first4=Ferran |last5=Herrmann |first5=François R. |last6=Robine |first6=Jean Marie |last7=Basagaña |first7=Xavier |last8=Tonne |first8=Cathryn |last9=Antó |first9=Josep M. |last10=Achebak |first10=Hicham |title=Heat-related mortality in Europe during the summer of 2022 |journal=Nature Medicine |date=July 2023 |volume=29 |issue=7 |pages=1857–1866 |doi=10.1038/s41591-023-02419-z|pmid=37429922 |pmc=10353926 |hdl=10230/58052 |hdl-access=free }}

In Slavic mythology, there is a personification of sunstroke, Poludnitsa (lady midday), a feminine demon clad in white that causes impairment or death to people working in the fields at midday. There was a traditional short break in harvest work at noon, to avoid attack by the demon. Antonín Dvořák's symphonic poem, The Noon Witch, was inspired by this tradition.

Heatstroke can affect livestock, especially in hot, humid weather; or if the horse, cow, sheep or other is unfit, overweight, has a dense coat, is overworked, or is left in a horsebox in full sun. Symptoms include drooling, panting, high temperature, sweating, and rapid pulse.

The animal should be moved to shade, drenched in cold water and offered water or electrolyte to drink.Horse and Hound, 'First Aid: Handling Heatstroke', 2/8/2004

• Hyperthermia
• Heat exhaustion
• Occupational heat stress

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• [http://www.medicinenet.com/heat_stroke/article.htm Heat stroke] on MedicineNet.com

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Category:Effects of external causes

Category:Medical emergencies

Category:Wikipedia medicine articles ready to translate

Category:Wikipedia emergency medicine articles ready to translate

Category:Thermoregulation