48 Fun Facts About Hypothermia

Hypothermia is defined as a core temperature about how many degrees Celsius below normal?

2 °C is the whole margin, from 37 down to 35, and it doesn't take a blizzard to lose it: rain, sweat or a dunking can chill a person that far on a merely cool day.

Which symptom of mild hypothermia typically stops once the condition becomes moderate?

Shivering is the body's own heater, so once it fades the temperature falls even faster. A cold person who stops shaking is getting worse, not better.

First-aiders are told to move a severely hypothermic person very gently because a jolt can trigger what?

A fatal heart rhythm: a deeply chilled heart is so irritable that a rough lift or a bumpy carry can tip it into ventricular fibrillation.

In 'paradoxical undressing', people dying of cold strip off their clothes, most likely because they suddenly feel what?

Burning hot is the leading theory. The tiny muscles that clamp the skin's blood vessels shut finally tire and let go, and warm blood surges back to the surface.

In 'terminal burrowing', or hide-and-die syndrome, where do people in the last stage of hypothermia crawl?

Small enclosed spaces, such as under a bed or behind a wardrobe. The German pathologists who named it saw a primitive brain-stem reflex, like a hibernating animal going to ground.

Polish doctors who revived a toddler from 12.7 °C in 2014 kept him for days in what?

An artificial coma followed for the two-year-old, who had slipped out of his grandmother's house on a freezing night and was found by police. When he woke, his surgeon called it a miracle.

Alcohol raises hypothermia risk partly by causing what effect in the skin's blood vessels?

Dilation brings warm blood up to the skin, so a drinker feels warmer while actually losing heat faster.

In cold water, what does the Heat Escape Lessening Position have a person awaiting rescue do?

Hug knees to chest: curling up shields the trunk and slows heat loss, while swimming burns energy and can shorten survival time.

Titanic officer Charles Lightoller wrote that diving into the 28 °F sea felt like a thousand what being driven into his body?

Knives, he wrote, and for a few moments he lost all grip of himself. Lightoller lived through the night by standing on an upturned lifeboat until rescue came.

Plunged into freezing seas, many victims die within the first couple of minutes from what?

Cold shock sets off uncontrolled gasping and a racing heart the instant skin meets the water, and one gasp taken under the surface can drown. Core temperature takes far longer to fall.

Sitting or lying on cold ground drains body heat by direct contact, a process known as what?

Conduction is heat passing straight into whatever the body touches. Water does it far faster than air, which is why a soaking chills a person so quickly.

Doctors can spot hypothermia from an extra hump called the Osborn wave on which hospital test?

An ECG heart trace shows the extra hump, nicknamed the camel-hump sign, and it grows taller as the patient gets colder.

Despite the old advice about hats, how does heat loss from an adult's bare head compare with other bare skin?

No greater: bare skin sheds heat at much the same rate wherever it is. The myth likely grew from 1950s military cold tests on men bundled up everywhere except the head.

Which everyday fabric do cold-weather guides warn against wearing next to the skin?

Cotton soaks up moisture and holds it, robbing the body of heat, while wool and synthetics such as polypropylene go on insulating even when wet.

Which of these does the UK National Health Service specifically warn against for a hypothermic person?

A hot bath is out, along with hot water bottles, heat lamps and alcohol: the NHS says to warm the person gently with dry clothes and blankets instead.

Because deep cold can mimic death, rescuers say a hypothermia victim is not dead until they are what?

Warm and dead: a chilled brain needs far less oxygen, so a person with no pulse and no breath can still come back. Doctors rewarm the body before they give up.

Doctors may stop trying to revive a hypothermia victim if a blood test shows sky-high levels of which mineral?

Potassium above 12 millimoles per litre is one of the few accepted reasons to stop, since a victim with no pulse is otherwise rewarmed before anyone gives up.

For some aortic and brain operations, surgeons chill a patient to about 20 °C so they can safely do what?

Stop all blood flow: with the heart halted and the brain all but silent, surgeons get a still field for half an hour or more. At normal temperature the brain would be damaged within minutes.

Which ancient general lost nearly half his men on a snowbound march during the Second Punic War?

Hannibal lost some 20,000 men crossing the Alps in 218 BC, yet the survivors went on to a string of victories over Rome in Italy, the greatest of them at Cannae.

Which microscopic animals can survive being frozen to about one degree above absolute zero?

Tardigrades, or water bears, shrivel into a dormant 'tun' in which they stop moving, breathing and doing almost anything else, then revive when conditions improve.

Bright red, cold skin is a warning sign of hypothermia in which group?

Babies lose heat faster than adults, and red, cold skin with very low energy is their warning sign, where an adult would fumble and slur words.

Anna Bågenholm, revived in 1999 after cooling to 13.7 °C under river ice, later took a job where?

The hospital that saved her took her on as a radiologist. She spent 60 days in intensive care and woke paralysed, yet recovered well enough to ski again.

Anna Bågenholm was skiing near Narvik in which country when she fell through the ice?

Norway's Arctic north was where the Swedish trainee surgeon had gone to work. The two friends skiing with her were doctors too, and they began CPR the moment she was pulled from the water.

Erika Nordby, Canada's 'Miracle Baby', survived wandering outdoors on a bitter February night in 2001 wearing only what?

A diaper was all the 13-month-old had on when her mother found her in the snow. Her heart had been still for about two hours before Edmonton doctors slowly warmed her back to life.

Doctors said hiker Mitsutaka Uchikoshi, found alive after 24 days on a Japanese mountain in 2006, had entered a state like what?

Hibernation was his doctor's word for it: his body had cooled to 22 °C and his organs had slowed while his brain stayed protected. Other experts doubted anyone could last that long without water.

After two trials in 2002, many hospitals began chilling unconscious patients to about 33 °C for a day after what?

Cardiac arrest starves the brain of oxygen, and the cooling was meant to limit the damage. A later trial found 36 °C did as well as 33, a hint that simply preventing fever is what helps.

Cooling caps are used during chemotherapy to prevent which side effect?

Hair loss is held off because the cold narrows the blood vessels in the scalp, so less of the drug reaches the hair roots. The caps help with some chemotherapy drugs but not all.

A classic early account of frostbite was written by the chief surgeon of whose army?

Napoleon's chief surgeon, Dominique Jean Larrey, saw cold injury on a mass scale during the 1812 invasion of Russia. He also invented the horse-drawn 'flying ambulance' that rushed the wounded off the battlefield.

Rescuers are told not to thaw a frostbitten foot in the field if there is any risk of what?

Refreezing does more damage than staying frozen: tissue that thaws and then freezes again is injured more extensively, so rewarming waits until the foot can be kept warm.

Even a strong swimmer without a life jacket will soon drown in icy water, because the cold makes them lose what?

Control of their limbs goes first: chilled arms and legs stop answering long before the body's core cools. That is why a life jacket, not swimming skill, keeps a person alive in cold water.

In 2007, trench foot struck mud-soaked crowds at which British festival?

Glastonbury was a days-long mud bath that year, and feet kept cold and wet for days are all the condition needs. Hikers and homeless people get it too, not just soldiers.

By the winter of 1917–18, British soldiers reduced trench foot partly by greasing their feet with what?

Whale oil was rubbed into dry feet to keep out the wet. Just as useful was pairing the men off, each answerable for the other's feet, since a soldier dried his socks more readily with a mate nagging him.

The wood frog, found north of the Arctic Circle, gets through winter by doing what?

Freezing solid: for months it has no heartbeat and takes no breath, while glucose pouring out of its liver keeps ice from forming inside the cells. In spring it thaws and hops away unharmed.

Which mammal sleeps through winter with its body cooled below freezing, to about −3 °C, yet never turns to ice?

Arctic ground squirrel: its body supercools to about −3 °C without freezing. Every two or three weeks, still asleep, it shivers for half a day to warm itself up, then sinks back into the cold.

Madagascar's dwarf lemur sleeps up to seven months in a tree hole, even in 30 °C heat, to escape what?

The dry season leaves little fruit, so the fat-tailed dwarf lemur gorges in the wet months, stores the fat in its tail and lives off it while it sleeps.

By 2006 Unilever was using a fish antifreeze protein, grown in yeast, to make some American brands of what?

Ice cream stays smooth because the protein stops ice crystals growing, the same trick that keeps the fish alive in freezing seas. Labels call it an ice structuring protein rather than antifreeze.

The crinkly foil blanket wrapped round marathon finishers was first developed by whom?

NASA had the metal-coated plastic film developed to shield spacecraft from extremes of heat and cold, which is why the foil wrap is sold as a space blanket.

The first wind chill index came from two explorers timing how fast water froze in the wind where?

Antarctica was where Paul Siple and Charles Passel hung cylinders of water outside their base and timed the freeze at each wind speed. Siple had first gone south as the Boy Scout chosen to sail with Admiral Byrd.

Newborn babies cannot shiver, so they keep warm by burning which tissue?

Brown fat, packed around a newborn's neck and shoulders, burns energy purely to give off heat. Its colour comes from iron-rich mitochondria, and most of it fades away as we grow up.

Minard's famous 1869 chart of the retreat from Moscow sets the army's shrinking numbers against a line showing what?

Falling temperature runs along the foot of the chart in degrees Réaumur, down to 30 below, about −38 °C. Of the 422,000 men it shows marching in, only 10,000 come back.

Whose short story 'To Build a Fire' depicts a man succumbing to cold in the Yukon?

Jack London wrote it twice: in the 1902 version for a youth magazine the man survives with scarred hands and a lesson learned, and only in the famous 1908 rewrite does he freeze to death.

Roughly half of US hypothermia deaths reported between 1999 and 2002 were people aged what?

65 or older made up 49% of the deaths, and nearly a quarter of all victims were in their own homes. The CDC says older bodies make less heat and are slower to notice the cold.

Chilblains are caused by repeated exposure of the skin to temperatures that are what?

Just above freezing, and damp with it: chilblains are a complaint of chilly, poorly heated homes in places like Britain rather than of truly frozen countries. The itchy patches usually clear within weeks.

Alaska topped the CDC's hypothermia death rates for 1999 to 2002, but which Sun Belt state also made the top four?

New Mexico ranked fourth, behind Alaska, Montana and Wyoming, and deaths were recorded in all 50 states. The CDC warns that high ground and big daily temperature swings carry a risk of their own.

Which is the fastest way for a hospital to rewarm a severely hypothermic patient?

Warming the blood outside the body, on an ECMO or heart-lung machine, can lift core temperature by several degrees an hour. The same machine keeps blood flowing if the heart has stopped.

The Swiss staging system, built for rescuers in the field, grades hypothermia according to what?

The presenting symptoms, from awake and shaking at stage one to apparent death at stage four, stand in for a core reading that rescuers on a mountainside can rarely take.

In hypothermia treatment, what does 'afterdrop' refer to?

It was seen in laboratory experiments and once raised fears about external rewarming, though recent studies have not backed those concerns.

In the first, mild stage of hypothermia, what does the heart rate do?

Speeds up: the heart beats faster at first as the body fights to make heat. Only as the core keeps cooling does it slow, reaching the 30s, about half its normal rate, by 28 °C.