Our climate is becoming hotter. Extreme heat is already responsible for hundreds of deaths every year. It’s a big environmental killer.
Heatstroke is an inability to adequately dissipate heat. It is a form of hyperthermia associated with a systemic inflammatory response that leads to multiorgan dysfunction syndrome (MODS), in which central nervous system (CNS) disorders (e.g., delirium, convulsion, and coma) predominate.
If the core temperature rises above 40.5℃, it can lead to heatstroke, which is a medical emergency, can occur suddenly and often kills.
It can be caused by
1.Severe heat exposure (classic heatstroke)
2.Strenuous work (exertional heatstroke).
HOW IS HEAT STROKE DIFFERENT FROM FEVER?
Hyperthermia is divided into two categories: pyrogenic (fever) and nonpyrogenic (heatstroke).
Pyrogenic hyperthermia is a result of the hypothalamus being reset to a higher point than normal.
A true fever is the body’s response when exposed to any endogenous pyrogens (cytokines released from cells of the immune system) or exogenous pyrogens (antigens associated with bacterial, viral, or parasitic infections, inflammation, neoplasia, and some medications). The hypothalamus’ “set point” is abnormally elevated.
Nonpyrogenic hyperthermia is caused by external or environmental factors, and the hypothalamus “set point” remains normal but the ability to regulate body temperature is lost.
WHAT HAPPENS TO THE THERMOREGULATOR-THE HYPOTHALAMUS?
The anterior nucleus in the hypothalamus plays an important role in cooling the body.
But severe heat exposure causes decreased mean arterial pressure (MAP) and increased intracranial pressure (ICP) which leads to decreased cerebral perfusion pressure (CPP = MAP – ICP), all of which lead to cerebral ischemia and hypoxia.
It leads to neuronal necrosis, apoptosis, and autophagy in the hypothalamus. Ischemic, hypoxic, and oxidative damage to the hypothalamus is involved in the pathogenesis of heatstroke.
HOW DO WE LOSE HEAT NORMALLY?
1. Transferring the heat to the cooler environment like blood vessels supplying blood to the skin dilate. This allows warmer blood to flow near the surface of the skin, where the heat can be lost to the air. That’s why some people’s skin looks redder in hot environments! But if the surroundings are hot these mechanisms are greatly reduced.
2. Evaporation (or sweat) is another way to lose heat from the body.
SYMPTOMS and SIGNS
Heatstroke can occur without any previous heat-related condition, such as heat exhaustion. Heatstroke signs and symptoms include:
• Fever of 104 degree F (40 degree C) or greater.
• Changes in mental status or behavior, such as confusion, agitation, slurred speech.
• Hot, dry skin or heavy sweating
• Nausea and vomiting
• Flushed skin
• Rapid pulse
• Rapid breathing
• Headache
• Fainting, which may be the first sign in older adults.
Two major findings—hyperthermia and CNS dysfunction (such as delirium, convulsion, or coma)—must be present for a diagnosis of heatstroke.
FIRST AID
Immediately move the person out of the heat, remove excess clothing, and the most important goal is to cool the core body temperature, preferable over 30-60 minutes, to 38 degree C.
While waiting for the ambulance to arrive:
• SOAK with any available water
• FAN vigorously by whatever means possible – improvise, e.g. use a clipboard, bin lid. When available, cool or ice water immersion is the most effective cooling means possible:
• IMMERSE the person up to the neck in a cool or ice bath
• COVER all of the body with ice water-soaked towels that are changed frequently as an alternative if a bath isn’t available but ice is. Cool, not cold, water soaking usually is the first step. Using cold water will cause vasoconstriction and thus reduce the ability to dissipate heat.
• Place ice packs or cool wet towels on the neck, armpits, and groin because these areas are rich with blood vessels close to the skin, cooling them can reduce body temperature.
• Do not give aspirin or acetaminophen. These medicines may cause problems because of the body's response to heatstroke. Let the person drink cool water to rehydrate if he or she is able. Don't give sugary, caffeinated, or alcoholic beverages to a person with heatstroke. Also avoid very cold drinks, as these can cause stomach cramps.
Begin CPR if the person loses consciousness and shows no signs of circulation, such as breathing, coughing, or movement.
It is early recognition and first aid in heat stroke that is critical to saving a life.
REFERENCES
Great article Tejaswi! Interesting to see what happens to the thermal regulation in the body in case of a heat stroke.