Hypothermia

First aid for hypothermia

1. Call 911 or your local emergency number for anyone confused, drowsy, unconscious or not shivering despite being cold.
2. Move the person out of the cold into a warm, dry place, or shelter them from wind.
3. Handle gently. Rough movement can trigger a dangerous heart rhythm in severe hypothermia. Keep them lying flat if possible.
4. Remove wet clothing and replace with dry layers, or cut clothes off to avoid jostling.
5. Insulate: wrap in blankets, sleeping bags or coats, covering the head and neck, with insulation underneath too.
6. Warm the core first: place warm (not hot) packs or bottles wrapped in cloth in the armpits, sides of the chest and groin. Skin-to-skin contact under blankets also helps.
7. Give warm, sweet, non-alcoholic drinks only if the person is fully alert and can swallow.
8. If not breathing normally, start CPR. Check breathing and pulse for up to a minute, because they can be very slow.

Stages of hypothermia

Standard thermometers often cannot read very low temperatures, so signs matter more than numbers outside a hospital. Doctors measure core temperature with special probes.

Symptoms

Early

• shivering
• cold, pale or bluish skin
• numb hands
• fast breathing
• tiredness
• clumsiness and fumbling
• slurred speech
• confusion and poor decision-making ("the umbles": stumbles, mumbles, fumbles, grumbles)

Later

• shivering stops
• drowsiness and very low energy
• weak, slow pulse
• slow, shallow breathing
• loss of consciousness

In babies

• bright red, cold skin
• very low energy and poor feeding

Causes and risk factors

• cold air, wind and rain, especially with wet clothing
• immersion in cold water, which removes heat many times faster than cold air
• older age: reduced ability to sense and respond to cold, chronic illness, medicines, and cold homes
• infants, who lose heat quickly
• alcohol and drugs, which widen blood vessels and impair judgment
• medical conditions: hypothyroidism, hypoglycemia, stroke, spinal cord injury, Parkinson's disease, dementia, malnutrition and sepsis
• medicines: sedatives, antipsychotics and some antidepressants
• exhaustion and dehydration in outdoor activities
• homelessness and inadequate heating

Hospital treatment

• careful monitoring of heart rhythm and core temperature
• passive rewarming for mild cases: blankets in a warm room
• active external rewarming: forced warm-air blankets
• active internal rewarming: warmed IV fluids, warm humidified oxygen, and in severe cases warmed fluid lavage of the chest or bladder
• extracorporeal rewarming: a heart-lung machine (ECMO or bypass) for cardiac arrest or severe instability

Not dead until warm and dead

People with severe hypothermia can appear dead but still recover. Cold protects the brain. Resuscitation is often continued until the person is rewarmed, and full recovery is possible even after prolonged CPR in some cases.

Complications

• dangerous heart rhythms and cardiac arrest
• frostbite and nonfreezing cold injury (trench foot)
• pneumonia
• kidney injury
• rewarming-related drops in blood pressure

Prevention

• dress in layers, with a hat, gloves and waterproof outer layer, and stay dry
• avoid cotton next to the skin in cold, wet outdoor activities
• eat and drink regularly during outdoor activities, and avoid alcohol
• check on older neighbors and relatives during cold weather, and keep homes at least about 18 to 20 °C (65 to 68 °F)
• wear a life jacket on boats, and know that cold water is dangerous even in spring and summer
• watch for early signs in companions, who may not notice their own confusion

Frequently asked questions

What are the first signs of hypothermia?

Early signs are shivering, cold and pale skin, fumbling hands, slurred speech, clumsiness and confusion. People often do not realize they are becoming hypothermic because their judgment is affected, so others need to watch for these signs.

What temperature is hypothermia?

Hypothermia is a core body temperature below 35 °C (95 °F). It is mild from 32 to 35 °C (90 to 95 °F), moderate from 28 to 32 °C (82 to 90 °F) and severe below 28 °C (82 °F).

How do you treat hypothermia at home?

Move the person somewhere warm, remove wet clothes, wrap them in dry blankets including the head, and warm the chest, armpits and groin with wrapped warm packs. Give warm sweet drinks only if they are fully alert. Call 911 if they are confused, drowsy or not shivering.

Can you get hypothermia indoors?

Yes. Older adults in cold homes, people with certain illnesses or on sedating medicines, and babies can develop hypothermia indoors, even at temperatures that feel only cool. Keeping homes adequately heated and checking on vulnerable people is important.

Why should you not rub someone with hypothermia?

Rubbing the arms and legs can push cold blood from the limbs toward the heart and trigger dangerous heart rhythms in severe hypothermia. It can also damage cold, fragile tissue. Gentle handling and warming the core is safer.