Heat stroke

Heat stroke generally presents with a hyperthermia of greater than in combination with disorientation. There is generally a lack of sweating in classic heatstroke, while sweating is generally present in exertional heatstroke. 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. ==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. 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). 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. 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. == Pathophysiology ==

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. Growing evidence also suggests the existence of a second pathway underlying heat stroke that involves heat and exercise-driven endotoxemia. 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. ==Diagnosis==

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. 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. ==Prevention==

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. 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). • Know signs/symptoms of heat-related illnesses. • Block out direct sun and other heat sources. • People should drink fluids often, even if they are not thirsty. • Wear lightweight, light-colored, loose-fitting clothes. • Avoid beverages containing alcohol or caffeine. ==Treatment==

Treatment of heat stroke involves rapid mechanical cooling along with standard resuscitation measures. The body temperature must be lowered quickly via conduction, convection, or evaporation. 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. ==Prognosis==

In elderly people who experience classic heat stroke the mortality exceeds 50%. In rare cases, brain damage has been reported as a permanent sequela of severe heat stroke, most commonly cerebellar atrophy. ==Epidemiology==

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. Different parts of the world also have different rates of heat stroke. 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. ==Society and culture==

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. ==Other animals==

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. == See also ==