Heat Stroke: Recognising It Early and Cooling Fast
Indian summers now routinely cross 45 degrees in large parts of the country, and heat kills more people in some years than most other natural hazards combined. Heat stroke is survivable when recognised and cooled fast, and the first 30 minutes determine the outcome.
The spectrum
Heat cramps. Painful muscle spasms during or after exertion in heat, from salt and fluid loss. Rest in a cool place, oral rehydration solution, gentle stretching.
Heat exhaustion. The body is struggling but temperature regulation still works:
- Heavy sweating, cool clammy pale skin
- Weakness, fatigue, dizziness, fainting
- Headache, nausea, vomiting
- Muscle cramps
- Fast weak pulse
- Temperature usually below 40 degrees
- Mental state is normal
Heat stroke. Regulation has failed. This is a medical emergency:
- Core temperature above 40 degrees
- Altered mental state: confusion, agitation, slurred speech, irritability, delirium, seizure, loss of consciousness
- Skin that is hot and often dry, though in exertional heat stroke the person may still be sweating. Dry skin is a classic sign but its absence does not exclude the diagnosis
- Rapid breathing, rapid pulse
- Nausea and vomiting
- Flushed skin
The single distinguishing feature is mental status. Confusion in a hot person is heat stroke until proven otherwise.
What to do for heat stroke
Call emergency services, then begin cooling immediately. Do not wait for the ambulance to start.
Cool first, transport second. Mortality rises with every minute above 40 degrees, and organ damage accumulates.
- Move to shade or an air-conditioned space
- Remove clothing
- Cold water immersion is the most effective method if available: a tub, a tank, any large container of cold water, up to the neck, keeping the head supported
- If immersion is not possible: continuously douse with cold water and fan vigorously. Evaporative cooling with constant water and moving air is the practical field method
- Apply ice packs or cold cloths to the neck, armpits and groin, where large vessels run close to the surface
- Keep going until the person is alert and cooler, or help arrives
- Do not give fluids by mouth to a confused or unconscious person, because of choking risk
- Do not give paracetamol or ibuprofen. They do not work here, because the problem is environmental heat gain rather than a raised thermostat, and they can worsen liver and kidney injury
- Do not use alcohol rubs
- Place an unconscious but breathing person on their side
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For heat exhaustion: rest in a cool place, remove excess clothing, cool with wet cloths and a fan, and give ORS in sips. If there is no improvement within 30 minutes, or any confusion develops, treat it as heat stroke.
Who is at highest risk
- Infants and young children, who have a higher surface-area-to-mass ratio and cannot remove themselves from heat
- Adults over 65, whose sweating and thirst responses are blunted
- Outdoor workers: construction, agriculture, delivery riders, traffic police, street vendors
- Athletes and anyone exercising in heat
- People with heart disease, diabetes, kidney disease, obesity
- People on certain medications: diuretics, anticholinergics, antihistamines, antipsychotics, beta blockers, some antidepressants, all of which impair sweating or fluid balance
- Alcohol users
- People living in poorly ventilated housing without cooling
- Pregnant women
- Anyone unacclimatised, including visitors, for whom the first few days carry the highest risk
Never leave a child or an animal in a parked vehicle, even briefly and even with windows cracked. Interior temperatures rise dangerously within minutes.
Prevention
Fluids. Drink before you are thirsty; thirst appears after dehydration has started. Use urine colour as the gauge, aiming for pale. Add ORS or salted drinks such as nimbu paani with salt, chaas or lassi during heavy sweating, since water alone replaces volume but not salt.
Avoid alcohol and limit very sugary drinks, which worsen dehydration. Coffee and tea in normal amounts are fine.
Timing. Avoid outdoor exertion between 11 am and 4 pm. Shift work to early morning and evening.
Clothing. Loose, light-coloured, breathable cotton. A wide-brimmed hat or cloth head covering. An umbrella is highly effective and underused.
Cooling. Cool showers, wet cloths on the neck, a fan with damp curtains. Note that above about 40 degrees a fan alone can increase heat gain in low humidity; combine it with water on the skin.
Shelter. Keep curtains closed on sun-facing windows during the day, ventilate at night, and use the coolest room in the house.
Acclimatisation. Build exposure gradually over 10 to 14 days when starting outdoor work or arriving in a hot region.
Workplaces should provide shade, water, scheduled rest breaks, and training in recognising the signs.
Check on people. The deaths cluster among older adults living alone. A daily call or visit during a heat wave is a meaningful intervention.
Afterwards
Heat stroke can cause kidney injury, liver injury, rhabdomyolysis where muscle breaks down and the urine turns dark, clotting abnormalities and lasting neurological damage. Anyone who has had heat stroke needs hospital assessment and monitoring even after cooling, and is at increased risk in future heat exposure.
This is general information. Heat stroke is a medical emergency; begin cooling immediately and call for emergency help at the same time.