How Do You Treat Heat Exhaustion in the Field?

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Understanding Heat Illness Spectrum Heat Exhaustion vs. Heat Stroke Heat exhaustion occurs when your body loses more fluid than it can replace, causing blood volume to drop and cardiovascular function to degrade. The body continues sweating, core temperature remains below 40°C (104°F), and cognitive function is intact though impaired. Heat exhaustion is uncomfortable and dangerous but reversible with treatment.
Heat stroke occurs when your body’s cooling mechanisms fail completely. Core temperature rises above 40°C and continues rising. The body stops sweating (or sweats profusely then stops). Cognitive function deteriorates rapidly — confusion, slurred speech, and unconsciousness develop. Heat stroke is immediately life-threatening and requires aggressive emergency treatment. The distinction is critical: treatment approaches differ significantly.
Early Warning Signs Pay attention to early signs of heat illness before serious symptoms develop. Light-headedness or dizziness while standing, weakness, nausea, and goosebumps despite heat all indicate heat stress. As heat exhaustion develops, these symptoms intensify: cold, clammy skin despite high air temperature; muscle cramps; weakness that prevents coordinated movement.
Recognize these signs in yourself and others. Heat-affected individuals may not report symptoms due to cognitive impairment or false confidence. Observe behavior changes: irritability, poor decision-making, loss of balance. If someone suddenly becomes quiet and unconcerned in dangerous heat, they may be developing heat stroke.
Treating Heat Exhaustion Immediate Response Protocol Move the affected person to shade immediately. Lie them flat with legs elevated slightly (unless vomiting, in which case position on their side). The goal is moving blood away from extremities back to central circulation and reducing the metabolic heat generation that comes with upright posture.
Remove excess clothing, but maintain sun protection. If heat exhaustion is progressing, remove layers to expose skin for cooling. However, don’t create sunburn exposure. The balance is maximizing heat loss while preventing additional sun damage.
Cooling Methods Apply cool water to the body if available. Wet clothing and allow evaporative cooling. In extreme situations, immerse the person in cool water if a water source is available. Evaporative cooling from water is the single most effective field cooling method. Wet the skin and expose it to air — the evaporation removes massive amounts of heat.
If no water is available, use sweat evaporation. Remove clothing (keeping sun-sensitive areas covered), keep the person still to prevent wind loss disruption, and allow their sweat to evaporate. This is less efficient than applying water but still effective.
Hydration Protocol Offer small sips of water (not large volumes). Small sips enter the stomach gradually and minimize the risk of vomiting. If water is scarce, offer just enough to support recovery without risking dehydration elsewhere in your group. If the person is vomiting, stop offering water — vomiting indicates fluid is not being retained and causes additional fluid loss.
Electrolyte drinks are ideal if available, but plain water works. In emergency situations, you may add small amounts of salt to water (1/4 teaspoon per liter), though this is controversial. Focus on water replacement first and foremost. Small, frequent sips every 5-10 minutes are better than periodic large volumes.
Monitoring Recovery Heat exhaustion recovery is relatively rapid once cooling begins. Within 15-30 minutes of appropriate treatment, cognitive function should improve and symptoms should decrease. The person should feel noticeably better. If improvement doesn’t occur or symptoms worsen, assume heat stroke is developing and escalate treatment aggressively.
Continue cooling and hydration for at least 30 minutes after initial symptom improvement. Return to activity only after the person feels genuinely recovered — weakness persists longer than other symptoms. Most importantly, once someone experiences heat exhaustion, their heat tolerance is compromised for days. Avoid further heat exposure that day and the following day.
Treating Heat Stroke (Medical Emergency) Recognizing Heat Stroke Progression Heat stroke symptoms escalate rapidly: confusion, poor coordination, slurred speech, rapid heart rate (typically 160+ bpm), and either profuse sweating or complete cessation of sweating. High body temperature is present though you may not have a thermometer to confirm it. The person may become unconscious.
The distinction from heat exhaustion is the cognitive deterioration. Heat stroke causes altered mental status — confusion about location, time, or identity; lack of concern despite dangerous conditions; aggressive or irrational behavior. This progression indicates core temperature has risen above 40°C and cellular damage is occurring.
Aggressive Field Cooling Heat stroke requires aggressive cooling immediately — every minute of delay increases the risk of permanent brain damage or death. If a water source is available, immerse the person in cool water if possible. If immersion is impossible, apply cool water continuously while moving the person to shade.
Remove all clothing except for sun protection on the face. Apply water to skin and allow evaporative cooling. Wet the head and face — significant heat loss occurs through the head. Use fans or create air movement to enhance evaporation. In extreme situations, apply ice or snow if available, though this is less ideal than cool water.
Hydration in Heat Stroke Do not offer water to an unconscious person — they cannot swallow and will aspirate the water. If the person is conscious but confused, offer small sips but prioritize cooling over hydration. If they’re vomiting, focus on cooling, not fluid intake.
Once the person recovers consciousness and is alert, begin small sips of water. Recovery from heat stroke is slower than heat exhaustion and more complete cooling is required. Even after consciousness returns, the person is dangerously vulnerable to recurrence.
Evacuation Necessity Heat stroke requires immediate medical evacuation. While you should treat heat stroke aggressively in the field, definitive recovery requires professional medical care. Core temperature may fluctuate for hours, and organ damage from extreme heat may not be immediately apparent. Attempt to get professional medical evaluation as soon as possible.
In remote areas, this may mean activating emergency response, signaling aircraft, or moving the person to a location where evacuation is possible. Do not attempt to wait out heat stroke in a remote camp — the risk of deterioration or recurrence is too high.
Prevention of Heat Illness Heat Acclimatization Exposure to heat over 10-14 days improves your body’s ability to handle heat. Sweat production increases while body temperature rises less during exertion. Your cardiovascular system becomes more efficient at managing core temperature. If possible, acclimatize yourself to hot conditions before requiring survival in heat.
Acclimatization is individual — some people acclimate faster than others. Genetics, fitness, and age all affect acclimatization rate. Even acclimatized individuals can develop heat illness in extreme conditions.
Hydration Management Drink water consistently rather than waiting until thirsty. Thirst is a late indicator of dehydration — by the time you’re thirsty, some dehydration has already occurred. In heat, drink 200-300 ml of water every 15-20 minutes during activity. This prevents the water deficit that leads to heat exhaustion.
Monitor urine color as a hydration indicator. Clear or pale yellow urine indicates adequate hydration. Dark yellow indicates dehydration. This simple check helps you maintain hydration without needing to measure water intake precisely.
Activity Management Avoid strenuous activity during the hottest hours (typically 11 AM to 4 PM). Shift activities to cooler morning and evening hours. If activity during heat is necessary, reduce intensity. Heat illness often develops in people who attempt to maintain normal pace in extreme heat — slowing down and taking frequent rests prevents the thermal overload.
Clothing and Protection Wear light-colored, loose-fitting clothing that allows evaporative cooling and reflects heat. A wide-brimmed hat provides sun protection and reduces radiant heating of the head. Long sleeves and pants protect from sunburn which increases body temperature. While this seems counterintuitive, the sunburn protection more than compensates for the extra clothing.
Apply sunscreen to all exposed skin. Sunburn prevents effective sweating and increases body temperature. Protecting your skin improves your heat tolerance and prevents additional thermal stress from solar radiation.
Special Populations and Heat Illness Elderly and Very Young People Older adults have reduced sweat production and less efficient cardiovascular regulation. Children have higher metabolic rates and generate more internal heat. Both populations are more susceptible to heat illness. Monitor them closely and treat heat stress aggressively at early signs rather than waiting for serious symptoms.
People on Medications Certain medications (stimulants, antihistamines, psychiatric medications) reduce sweating and increase heat susceptibility. If you’re aware of medication effects, plan additional cooling measures and hydration. Inform others in your group of specific vulnerabilities.
Prior Heat Illness History Someone who previously experienced heat stroke has increased risk of recurrence. Their heat tolerance is permanently reduced. Avoid exposing them to extreme heat and monitor closely for heat illness signs. Previous heat exhaustion increases risk of future episodes but doesn’t necessarily reduce heat tolerance permanently if adequate time passes between incidents.