Heat stroke is a life-threatening condition clinically diagnosed as a severe elevation in body temperature with central nervous system dysfunction that often includes combativeness, delirium, seizures, and coma. Classic heat stroke primarily occurs in immunocompromised individuals during annual heat waves.
Exertional heat stroke is observed in young fit individuals performing strenuous physical activity in hot or temperature environments. Long-term consequences of heat stroke are thought to be due to a systemic inflammatory response syndrome.
This article provides a comprehensive review of recent advances in the identification of risk factors that predispose to heat stroke, the role of endotoxin and cytokines in mediation of multi-organ damage, the incidence of hypothermia and fever during heat stroke recovery, clinical biomarkers of organ damage severity, and protective cooling strategies.
Risk factors include environmental factors, medications, drug use, compromised health status, and genetic conditions. The role of endotoxin and cytokines is discussed in the framework of research conducted over 30 years ago that requires reassessment to more clearly identify the role of these factors in the systemic inflammatory response syndrome.
We challenge the notion that hypothalamic damage is responsible for thermoregulatory disturbances during heat stroke recovery and highlight recent advances in our understanding of the regulated nature of these responses. The need for more sensitive clinical biomarkers of organ damage is examined.
Conventional and emerging cooling methods are discussed with reference to protection against peripheral organ damage and selective brain cooling.
Heat stroke or heatstroke, also known as sun-stroke, is a severe heat illness that results in a body temperature greater than 40.0 °C (104.0 °F), along with red skin, headache, dizziness, and confusion. sweating is generally present in exertional heatstroke, but not in classic heatstroke. The start of heat stroke can be sudden or gradual. Due to the possibility of multiple organ failure, heatstroke can be fatal. Common side effects headaches, and kidney failure.
Heat stroke occurs because of high external temperatures and physical exertion. It usually occurs under preventable prolonged exposure to extreme environmental or exertional heat. However, certain health conditions can increase the risk of heat stroke, and patients, especially children, with certain genetic predispositions are vulnerable to heatstroke under relatively mild conditions.
Drinking enough water and staying out of the heat are preventive measures. Treatment is by rapid physical cooling of the body and supportive care. Recommended methods include spraying the person with water and using a fan, putting the person in ice water, or giving cold intravenous fluids. Adding ice packs around a person is reasonable but does not by itself achieve the fastest possible cooling.
Heat stroke results in more than 600 deaths a year in the United States. Rates increased between 1995 and 2015. Purely exercise-induced heat stroke, though a medical emergency, tends to be self-limiting (the patient stops exercising from cramp or exhaustion) and fewer than 5% of cases are fatal. Non-exertional heatstroke is a much greater danger: even the healthiest person, if left in a heatstroke-inducing environment without medical attention, will continue to deteriorate to the point of death, and 65% of the most severe cases are fatal even with treatment.
Signs And Symptoms
- Heat stroke generally presents with a hyperthermia of greater than 40.6 °C (105.1 °F) in combination with disorientation. There is generally a lack of sweating in classic heatstroke while sweating is generally present in exertional heatstroke.
- Heat stroke can cause behavioral abnormalities, disorientation, delirium, lightheadedness, weakness, agitation, aggression, slurred speech, nausea, and vomiting as early signs. 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. Rhabdomyolysis, 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. If heatstroke is not treated promptly and appropriately, it can be lethal.
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).
Preventions
By taking care to prevent dehydration and overheating, one may reduce their risk of suffering from heat stroke. 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 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).
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. Dehydration could be indicated by a dark yellowish tint.
Some measures that can help protect workers from heat stress include:
- 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
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. 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.
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, the person’s head must be held above water. 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. Research has demonstrated, however, that this process is not primarily responsible for the drop in body temperature caused by cold water.
Heat stroke cannot be effectively treated with dantrolene, a muscle relaxant used to treat other kinds of hyperthermia. Aspirin and acetaminophen are examples of antipyretics, which are not advised for use in the treatment of heat stroke since they can increase liver damage.
Reevaluating and stabilizing the patient should be the responsibility of trained medical personnel. If someone has gone into cardiac arrest, they may need cardiopulmonary resuscitation (CPR); the patient’s respiration and heart rate should be continuously monitored 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.