Heat stroke is a life-threatening heat illness involving severe overheating of the body and impaired brain function. Confusion, unusual behaviour, loss of coordination, seizures or unconsciousness can indicate that the heat load is already damaging vital functions. During military isolation, this directly threatens the ability to reach shelter, operate equipment or decide where to move. Suspected heat stroke requires immediate cooling; waiting for unconsciousness or a particular thermometer reading prolongs the damaging overheating.
Heat load and forms of heat stroke
Muscle work produces heat. The body carries it to the skin in the blood and releases it through processes including the evaporation of sweat. Core temperature rises when the body generates or absorbs more heat than it can dissipate. High humidity makes evaporation difficult; heavy or poorly ventilated clothing restricts heat exchange. Dehydration places additional strain on circulation and sweating. A fast march with a load and protective clothing can therefore become dangerous even in moderate outdoor temperatures.
Exertional heat stroke can develop rapidly during or after strenuous movement and can affect healthy, physically fit people. Exertional heat stroke, abbreviated EHS, is the term used in English-language military medicine. The British term severe exertional heat illness also describes this condition with impaired brain function. Lack of heat acclimatisation, illness and preceding fatigue increase the risk; physical fitness does not remove it.
Classic heat stroke chiefly results from prolonged exposure to environmental heat without substantial physical exertion. People with impaired cardiovascular capacity or heat dissipation are particularly vulnerable. Both forms can damage the brain, kidneys, liver and circulation. Their different origins do not change the urgency of cooling.
Recognition without waiting for a reading
Headache, nausea, unusual weakness or dizziness can occur with heat exhaustion. When heat stroke is suspected, changes in thinking and movement are particularly significant: someone gives inappropriate answers to simple questions, speaks unusually indistinctly, suddenly behaves irrationally or staggers. Such changes during or after heat stress require action as a severe heat emergency. A seizure or unconsciousness is already a serious deterioration, not a sign to await for confirmation.
The skin may be hot and dry, but a person with exertional heat stroke in particular may continue to sweat profusely. Sweat on the skin proves neither adequate evaporation nor a falling core temperature. A wet uniform is therefore no reason to dismiss confusion or staggering as ordinary exhaustion.
Reliable core-temperature measurement is part of medical assessment and the control of intensive cooling. Ear, forehead, mouth or skin measurements can under-read after exertion. Cooling begins on reasonable suspicion even when no thermometer is available. Confusion can also result from conditions such as low blood glucose or dangerously low sodium; excessive water intake can contribute to the latter. This prevents a reliable self-diagnosis and makes forcing large quantities of water into every collapsed person an unsafe response.
Self-aid before mental impairment
While the person can still think clearly and act, unusual heat symptoms must prompt an end to exertion. Put down the pack, use the nearest actually reachable shaded or cooler place, and open or remove heavy, unnecessary clothing. A long onward journey to a supposedly better rest site produces additional heat. An immediate enemy threat may still require a short move to the nearest usable protected position; cooling must resume there immediately. A shaded place with air movement helps heat dissipation, whereas a stuffy, hot enclosure can obstruct it.
Skin cooling must begin before complete collapse. A fully awake, oriented person who can swallow safely and is not vomiting may take small sips of available drinking water when thirsty. This addresses possible dehydration but does not replace heat loss through the skin. Once confusion, unsafe swallowing or loss of consciousness develops, dependable self-care is no longer possible.
Cooling with the means available
With limited water, wet as much exposed skin as possible and move air across it, for example by fanning with a light object. Spread the water with a hand or cloth and rewet the skin when it dries. Thin, light clothing can also be wetted if it stays on the body. When a larger supply is immediately available, more extensive dousing with cool water is possible. These measures transfer heat to the water and allow evaporation; briefly wetting only the head leaves much of the body surface unused.
The British sequence Shade, Strip, Spray, Fan, abbreviated S3F, brings these actions together: find shade, remove heavy clothing, wet the person and fan them. It is also the alternative when immersion is not immediately available or cannot be carried out safely. Very humid air reduces evaporative cooling, making direct contact with cool water more significant. Wet cloths must be cooled again or replaced when they become warm. A warm, wet covering left in place can retain heat. Available cold packs can supplement cooling at the neck, armpits and groin, but on their own they cover only small areas.
If there is no water at all, the remaining actions are to stop exertion, reduce direct solar heating, remove heavy layers and use an actually cooler place or available air movement. Fanning alone has limited effectiveness in very hot, humid air. If overheating and mental impairment continue, these limited measures do not reliably resolve the problem. Any immediately usable better cooling option must then be used; another stretch of marching does not replace the missing heat dissipation.
Water immersion and airways
Cooling large body areas in cool or cold water can remove heat particularly quickly. Cold-water immersion is the most effective clinical cooling method for exertional heat stroke. Its organised use includes helpers who support the person, protect the head and airway, and monitor temperature and condition. A prepared tub, sufficient water and such helpers cannot be presumed during isolation.
A person who is already weak or confused must not enter a body of water alone to cool down: loss of coordination or consciousness can lead to drowning. Even with a buddy present, the mere availability of water is insufficient. If the buddy cannot keep the head and airway safely above water at all times or respond immediately to deterioration, wet and cool the person outside the water. Searching for a tub or ice must not delay the start of this available cooling.
Buddy aid when consciousness is impaired
If a capable person is actually present, they take over cooling and observe responsiveness and breathing. Give nothing to drink to someone who is confused, unconscious or having a seizure; fluid can enter the airway. An unconscious person who is breathing normally is placed in the recovery position so the airway stays open and vomit can drain. Accessible skin areas can continue to be cooled in that position.
If normal breathing is absent, the resuscitation measures learned in first-aid training take priority. Water immersion would obstruct access to the airway and chest. Seizures, another collapse, increasing confusion or breathing problems require a renewed check of breathing and condition, and the most effective cooling that can safely continue under those circumstances. Someone alone with this deterioration cannot reliably monitor themselves or continue moving in an orderly way.
Care after initial cooling
Being able to answer clearly again does not establish that the kidneys, liver or blood-clotting system remain undamaged. Injury can become apparent after an initial improvement. The person should undertake no further strenuous activity; a buddy, if actually present, continues to monitor responsiveness and breathing. Apparent recovery from heat stroke is no basis for simply resuming the march.
Suspected heat stroke needs urgent medical care. If an available communication device reaches an actual recipient with treatment or transport resources, pass the location, suspected heat emergency, consciousness and breathing status, and the cooling in progress, and arrange the handover. Cooling continues during contact. If an actual pickup becomes possible, the available helper must continue cooling and protecting the airway during transfers and transport as far as the circumstances allow: an interruption in heat dissipation can cause core temperature to rise again.