HipotermiaPasso 2
Mantas térmicas
Why: leves e pequenas: ajudam a conservar o calor por cima das mantas secas.
Essential guide · Base level · 7 min
Essential guideBase level · open to all7 min read
Hypothermia, heatstroke and dehydration: first aid
Warming someone with hypothermia, cooling heatstroke fast and replacing water and salts safely — following the ERC, the CDC and Portugal's DGS.
Reviewed 1 Oct 2026
09·IToo cold, too hot
In 30 seconds
The essentials, in four points.
Core
In hypothermia, warm the centre of the body first — chest, neck, head and groin — with dry blankets or skin-to-skin. Remove wet clothing.
39 °C
In heatstroke, cool immediately: best is immersing the body in cool water up to the neck until the temperature drops below 39 °C. Call 112.
Sachets
For dehydration, use oral rehydration salts from the pharmacy, made up as the pack says. After exertion, sports drinks, skimmed milk or water.
CPR
If the person doesn't respond and isn't breathing normally, start CPR — even if they seem dead from cold.
01Why it matters
The body copes poorly outside its temperature — and the person affected is the last to notice.
Hypothermia, heatstroke and severe dehydration have one thing in common: they affect the brain. The person becomes confused, slow, sometimes agitated — and doesn't realise they're in danger. That's why the person beside them has to recognise the signs and act.
In Portugal, these don't only happen in the mountains: they happen to older people in cold houses in winter, to workers and athletes on hot days, and to anyone stuck outdoors during a storm or a blackout.
Hypothermia
Shivering, exhaustion, confusion, fumbling hands, slurred speech, drowsiness. In babies, red, cold skin and little energy.
Heatstroke
Very high temperature, confusion, agitation, disorientation, seizures or loss of consciousness. It's an emergency.
Dehydration
Thirst, dizziness, dry mouth, dark and strong-smelling urine. It can progress to heatstroke.
02Hypothermia
Shelter. Dry. Warm the core.
Step 1
Shelter
Get the person into a warm room or shelter. If that's not possible, protect them from the wind and insulate them from the cold ground with blankets, coats or a sleeping mat.
Step 2
Dry
Remove wet clothing and cover them with dry layers: blankets, duvets, an emergency blanket on top. Don't forget the head.
Step 3
Warm the core
Warm the chest, neck, head and groin first — skin-to-skin, under loose blankets. If fully awake, warm non-alcoholic drinks.
1
Call 112 if they're confused, very drowsy, or not improving.
2
Handle them gently and keep them lying down. Don't make them walk or exert themselves.
3
No alcohol. It makes you lose heat.
4
If they don't respond and aren't breathing normally, start CPR, even if they seem dead. The chances of recovering from cardiac arrest caused by mild to moderate hypothermia are very good.
03Heatstroke
Cool first. Everything else after.
Plate 09·J — Cooling heatstrokeFrom most to least effective
1
Call 112 straight away. Heatstroke can damage the brain, kidneys and heart.
2
Move the person to shade or somewhere cool and remove as much clothing as possible.
3
Cool with whatever you have: a bath or tank of cool water up to the neck; failing that, shower, wet towels all over and fanning, or ice at the armpits, groin and neck.
4
Don't give drinks to anyone who isn't fully awake.
5
If they don't respond and aren't breathing normally, start CPR.
04Dehydration
Replace water and salts, a little at a time.
1
Confused, very drowsy, fainted, or very high temperature?
Yes
Call 112It may be heatstroke. Cool immediately (section 03) and don't give drinks if they're not fully awake.
No
2
Diarrhoea or vomiting, or a baby, young child or older person?
Yes
Oral rehydration saltsPharmacy sachets, made up exactly as the pack says, given in sips. If in doubt, SNS 24: 808 24 24 24.
No
3
Sweated a lot from exertion or heat and has thirst, dizziness, dry mouth or dark urine?
Yes
Drink and restSports drinks or skimmed milk; failing that, water in regular amounts. No alcohol. Rest in the shade.
No
If they don't improveCall SNS 24 or see a doctor.
05Six costly mistakes
Cold, heat and dehydration myths — and what to do instead.
Myth
“Rubbing hands and feet warms someone who's frozen.”
With frostbite, rubbing damages the skin. Warm the core first and the fingers in warm water.
Myth
“A shot of brandy helps warm you up.”
Alcohol makes you lose heat. Warm non-alcoholic drinks, only for someone fully awake.
Myth
“A hot-water bottle or heater against the feet warms faster.”
Frozen, numb skin burns without feeling it. Warm the core first and the fingers in warm water, never near heat sources.
Myth
“In heatstroke, the key is giving lots of water.”
The key is cooling, now. And anyone who isn't fully awake gets nothing to drink.
Myth
“Home-made rehydration drink is the same as the pharmacy's.”
Recipes vary and it's easy to get the salt wrong. Use pharmacy sachets, made up as the pack says.
Myth
“Someone who looks dead from cold has no chance.”
In cardiac arrest from hypothermia, early CPR can save a life. Always start.
06Recommended equipment
What warms, cools and replaces.
Emergency blankets and oral rehydration salt sachets take up little space and make a big difference. A thermometer helps tell whether temperature is rising or falling.
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DesidrataçãoSecção 04
Sais de reidratação oral
Why: preparados exatamente como diz a embalagem. Também se vendem nas farmácias.
VigiarSecção 01
Termómetro digital
Why: para perceber se a temperatura está a subir ou a descer.
Quick card
Print it. Stick it in the first-aid kit.
Stick this sheet next to the others in this module, in the first-aid kit.
Cold and heat · K72 sheet
1Hypothermia: shelter, remove wet clothing, insulate from the ground.
2Warm chest, neck, head, groin. No alcohol.
3Frostbite: don't rub; warm water.
4Heatstroke: 112 + cool now, ideally in water.
5Dehydration: pharmacy rehydration salts, in sips.
6Unresponsive, not breathing normally: CPR.
09·I · k72plus.comEMERGENCY: 112
- European Resuscitation Council — Guidelines 2021: First aid — heatstroke cooling (1–26 °C until < 39 °C), post-exertion rehydration
- European Resuscitation Council — The ERC Guidelines 2025 on Resuscitation for Everyone — hypothermia and cardiac arrest, hyperthermia
- Resuscitation Council UK — First aid guidelines 2025 — insulate from the ground, immersion up to the neck
- CDC — Preventing hypothermia and frostbite — signs, warming the core, frostbite
- DGS — Heatwaves: recommendations for the public (in Portuguese)
Reviewed 1 Oct 2026 · Next review: Mar 2027 · Spotted a mistake? Tell us.
This guide does not replace a first-aid course or assessment by a health professional. In an emergency, call 112; for health questions in Portugal, SNS 24: 808 24 24 24.
