Heatstroke
Heatstroke is the most severe form of heat-related illness and is considered a medical emergency that requires immediate treatment. It occurs when the body’s core temperature rises to 40°C (104°F) or higher, and its natural cooling systems fail. Heatstroke can cause widespread organ damage, neurological dysfunction, and even death if not treated rapidly. Unlike heat exhaustion, where the body still sweats in an effort to cool itself, heatstroke typically presents with hot, dry skin due to the collapse of thermoregulatory mechanisms. Recognising and acting swiftly on the signs of heatstroke can mean the difference between recovery and fatality.
At the centre of the condition is thermoregulatory failure. Under normal circumstances, the body maintains a stable internal temperature through sweating and vasodilation—where blood vessels expand to release heat through the skin. When exposed to extremely high temperatures or when physical exertion overwhelms the body’s ability to cool itself, this system begins to break down. As a result, the body’s core temperature continues to rise uncontrollably, damaging tissues, enzymes, and organ systems along the way. Once the brain’s temperature-regulating centres are impaired, core temperature can climb even higher, accelerating the crisis.
Exertional and Non-exertional
There are two primary types of heatstroke: exertional and non-exertional (classic). Exertional heatstroke usually affects healthy individuals—such as athletes, military personnel, or labourers—who engage in intense physical activity in hot environments. It can develop rapidly, sometimes within an hour, particularly if the person is dehydrated or not acclimatised to the heat. Non-exertional heatstroke, on the other hand, typically affects older adults, infants, and people with chronic illnesses during heatwaves or in poorly ventilated environments. It develops more slowly, often over several days, but can be just as deadly.
Risk factors for heatstroke include high humidity, dehydration, wearing heavy or restrictive clothing, certain medications (such as diuretics, antihistamines, or beta-blockers), and underlying health conditions like cardiovascular disease, diabetes, or obesity. Age is another critical factor: both the very young and the elderly are less capable of thermoregulation and are more prone to rapid overheating.
Heatstroke
The pathophysiology of heatstroke involves a dangerous cycle of rising body temperature, systemic inflammation, and cellular injury. As core temperature increases, proteins begin to denature, cellular membranes break down, and enzymes cease to function properly. This triggers a systemic inflammatory response similar to sepsis, with the release of cytokines, clotting factors, and other chemicals that further damage the vascular and immune systems. Organs such as the brain, liver, kidneys, and heart are particularly vulnerable.
The brain is often the first to be affected. As internal temperature climbs, cerebral oedema (swelling), blood-brain barrier disruption, and oxidative stress lead to confusion, disorientation, seizures, or coma. Neurological symptoms are not only an early marker of heatstroke but also a major determinant of prognosis. In severe cases, survivors may experience lasting cognitive or motor deficits, making prevention and immediate treatment essential.
Medical Emergency
Importantly, heatstroke is a medical emergency that must never be managed passively or with home remedies. The speed at which temperature rises and causes damage means that every minute counts. Without rapid cooling, mortality rates are high, ranging from 10% to over 50% depending on the delay in intervention and the presence of organ failure. The goal is to lower the core temperature to below 38.9°C (102°F) as quickly as possible using aggressive, targeted methods.
Understanding the distinct clinical features and causes of heatstroke is the first step in preventing this highly dangerous condition. Awareness is particularly important in a world where climate change is increasing the frequency and intensity of heatwaves across many regions.
In summary, heatstroke is a life-threatening failure of the body’s ability to regulate its temperature. It can occur suddenly and without warning, especially during high-heat exposure or exertion. Recognising the early symptoms and initiating emergency treatment immediately are critical to preventing death or long-term disability. With early intervention, recovery is possible—but delays can be catastrophic.
