| MadSci Network: Medicine |
Warm wishes Ian,
There are several excellent sites that deal extensively with hypothermia
and its complications and treatment. They are as follows:
The Search and Rescue Society of British Columbia http://www.sarbc.org/
JAMA http://www.hypothermia.org/jama.htm
The following article was taken from outdoor magazine and presents
a detailed description of every step of hypothermia from its inception
to its treatment and outcome. I hope you enjoy reading it as much as
I did.
Sincerely,
June Wingert RM(ASM)
Comparative Pathology Laboratory
Center For Comparative Medicine
Baylor College of Medicine
One Baylor Plaza
Houston, TX 77030
713-798-6591
fax 713-798-6595
As Freezing Persons Recollect the
Snow--First Chill--Then Stupor--Then the
Letting Go
The cold hard facts of freezing to death
By Peter Stark
When your Jeep spins lazily off the mountain road and slams
backward into a snowbank, you don't worry immediately about
the cold. Your first thought is that you've just dented your
bumper. Your second is that you've failed to bring a shovel. Your
third is that you'll be late for dinner. Friends are expecting you at
their cabin around eight for a moonlight ski, a late dinner, a sauna.
Nothing can keep you from that.
Driving out of town, defroster roaring, you barely noted the bank
thermometer on the town square: minus 27 degrees at 6:36. The
radio weather report warned of a deep mass of arctic air settling
over the region. The man who took your money at the Conoco
station shook his head at the register and said he wouldn't be
going anywhere tonight if he were you. You smiled. A little chill never
hurt anybody with enough
fleece and a good four-wheel-drive.
But now you're stuck. Jamming the gearshift into low, you try to muscle
out of the drift. The tires
whine on ice-slicked snow as headlights dance on the curtain of frosted
firs across the road.
Shoving the lever back into park, you shoulder open the door and step
from your heated
capsule. Cold slaps your naked face, squeezes tears from your eyes.
You check your watch: 7:18. You consult your map: A thin, switchbacking
line snakes up the
mountain to the penciled square that marks the cabin.
Breath rolls from you in short frosted puffs. The Jeep lies cocked
sideways in the snowbank like
an empty turtle shell. You think of firelight and saunas and warm food
and wine. You look again
at the map. It's maybe five or six miles more to that penciled square.
You run that far every day
before breakfast. You'll just put on your skis. No problem.
There is no precise core temperature at which the human body perishes
from cold. At Dachau's
cold-water immersion baths, Nazi doctors calculated death to arrive at
around 77 degrees
Fahrenheit. The lowest recorded core temperature in a surviving adult
is 60.8 degrees. For a
child it's lower: In 1994, a two-year-old girl in Saskatchewan wandered
out of her house into a
minus-40 night. She was found near her doorstep the next morning, limbs
frozen solid, her core
temperature 57 degrees. She lived.
Others are less fortunate, even in much milder conditions. One of
Europe's worst weather
disasters occurred during a 1964 competitive walk on a windy, rainy
English moor; three of the
racers died from hypothermia, though temperatures never fell below
freezing and ranged as high
as 45.
But for all scientists and statisticians now know of freezing and its
physiology, no one can yet
predict exactly how quickly and in whom hypothermia will strike--and
whether it will kill when it
does. The cold remains a mystery, more prone to fell men than women,
more lethal to the thin
and well muscled than to those with avoirdupois, and least forgiving to
the arrogant and the
unaware.
The process begins even before you leave the car, when you remove your
gloves to squeeze a
loose bail back into one of your ski bindings. The freezing metal bites
your flesh. Your skin
temperature drops.
Within a few seconds, the palms of your hands are a chilly, painful 60
degrees. Instinctively, the
web of surface capillaries on your hands constrict, sending blood
coursing away from your skin
and deeper into your torso. Your body is allowing your fingers to chill
in order to keep its vital
organs warm.
You replace your gloves, noticing only that your fingers have numbed
slightly. Then you kick
boots into bindings and start up the road.
Were you a Norwegian fisherman or Inuit hunter, both of whom frequently
work gloveless in the
cold, your chilled hands would open their surface capillaries
periodically to allow surges of warm
blood to pass into them and maintain their flexibility. This
phenomenon, known as the hunter's
response, can elevate a 35-degree skin temperature to 50 degrees within
seven or eight minutes.
Other human adaptations to the cold are more mysterious. Tibetan
Buddhist monks can raise the
skin temperature of their hands and feet by 15 degrees through
meditation. Australian aborigines,
who once slept on the ground, unclothed, on near-freezing nights, would
slip into a light
hypothermic state, suppressing shivering until the rising sun rewarmed
them.
You have no such defenses, having spent your days at a keyboard in a
climate-controlled office.
Only after about ten minutes of hard climbing, as your body temperature
rises, does blood start
seeping back into your fingers. Sweat trickles down your sternum and
spine.
By now you've left the road and decided to shortcut up the forested
mountainside to the road's
next switchback. Treading slowly through deep, soft snow as the full
moon hefts over a spiny
ridgetop, throwing silvery bands of moonlight and shadow, you think
your friends were right: It's
a beautiful night for skiing--though you admit, feeling the minus-30
air bite at your face, it's also
cold.
After an hour, there's still no sign of the switchback, and you've
begun to worry. You pause to
check the map. At this moment, your core temperature reaches its high:
100.8. Climbing in deep
snow, you've generated nearly ten times as much body heat as you do
when you are resting.
As you step around to orient map to forest, you hear a metallic pop.
You look down. The loose
bail has disappeared from your binding. You lift your foot and your ski
falls from your boot.
You twist on your flashlight, and its cold-weakened batteries throw a
yellowish circle in the
snow. It's right around here somewhere, you think, as you sift the snow
through gloved fingers.
Focused so intently on finding the bail, you hardly notice the frigid
air pressing against your tired
body and sweat-soaked clothes.
The exertion that warmed you on the way uphill now works against you:
Your exercise-dilated
capillaries carry the excess heat of your core to your skin, and your
wet clothing dispels it rapidly
into the night. The lack of insulating fat over your muscles allows the
cold to creep that much
closer to your warm blood.
Your temperature begins to plummet. Within 17 minutes it reaches the
normal 98.6. Then it slips
below.
At 97 degrees, hunched over in your slow search, the muscles along your
neck and shoulders
tighten in what's known as pre-shivering muscle tone. Sensors have
signaled the temperature
control center in your hypothalamus, which in turn has ordered the
constriction of the entire web
of surface capillaries. Your hands and feet begin to ache with cold.
Ignoring the pain, you dig
carefully through the snow; another ten minutes pass. Without the bail
you know you're in deep
trouble.
Finally, nearly 45 minutes later, you find the bail. You even manage to
pop it back into its socket
and clamp your boot into the binding. But the clammy chill that started
around your skin has now
wrapped deep into your body's core.
At 95, you've entered the zone of mild hypothermia. You're now
trembling violently as your
body attains its maximum shivering response, an involuntary condition
in which your muscles
contract rapidly to generate additional body heat.
It was a mistake, you realize, to come out on a night this cold. You
should turn back. Fishing into
the front pocket of your shell parka, you fumble out the map. You
consulted it to get here; it
should be able to guide you back to the warm car. It doesn't occur to
you in your increasingly
clouded and panicky mental state that you could simply follow your
tracks down the way you
came.
And after this long stop, the skiing itself has become more difficult.
By the time you push off
downhill, your muscles have cooled and tightened so dramatically that
they no longer contract
easily, and once contracted, they won't relax. You're locked into an
ungainly, spread-armed,
weak-kneed snowplow.
Still, you manage to maneuver between stands of fir, swishing down
through silvery light and
pools of shadow. You're too cold to think of the beautiful night or of
the friends you had meant
to see. You think only of the warm Jeep that waits for you somewhere at
the bottom of the hill.
Its gleaming shell is centered in your mind's eye as you come over the
crest of a small knoll. You
hear the sudden whistle of wind in your ears as you gain speed. Then,
before your mind can
quite process what the sight means, you notice a lump in the snow
ahead.
Recognizing, slowly, the danger that you are in, you try to jam your
skis to a stop. But in your
panic, your balance and judgment are poor. Moments later, your ski tips
plow into the buried log
and you sail headfirst through the air and bellyflop into the snow.
You lie still. There's a dead silence in the forest, broken by the
pumping of blood in your ears.
Your ankle is throbbing with pain and you've hit your head. You've also
lost your hat and a
glove. Scratchy snow is packed down your shirt. Meltwater trickles down
your neck and spine,
joined soon by a thin line of blood from a small cut on your head.
This situation, you realize with an immediate sense of panic, is
serious. Scrambling to rise, you
collapse in pain, your ankle crumpling beneath you.
As you sink back into the snow, shaken, your heat begins to drain away
at an alarming rate, your
head alone accounting for 50 percent of the loss. The pain of the cold
soon pierces your ears so
sharply that you root about in the snow until you find your hat and
mash it back onto your head.
But even that little activity has been exhausting. You know you should
find your glove as well,
and yet you're becoming too weary to feel any urgency. You decide to
have a short rest before
going on.
An hour passes. at one point, a stray thought says you should start
being scared, but fear is a
concept that floats somewhere beyond your immediate reach, like that
numb hand lying naked in
the snow. You've slid into the temperature range at which cold renders
the enzymes in your brain
less efficient. With every one-degree drop in body temperature below
95, your cerebral
metabolic rate falls off by 3 to 5 percent. When your core temperature
reaches 93, amnesia
nibbles at your consciousness. You check your watch: 12:58. Maybe
someone will come
looking for you soon. Moments later, you check again. You can't keep
the numbers in your
head. You'll remember little of what happens next.
Your head drops back. The snow crunches softly in your ear. In the
minus-35-degree air, your
core temperature falls about one degree every 30 to 40 minutes, your
body heat leaching out
into the soft, enveloping snow. Apathy at 91 degrees. Stupor at 90.
You've now crossed the boundary into profound hypothermia. By the time
your core
temperature has fallen to 88 degrees, your body has abandoned the urge
to warm itself by
shivering. Your blood is thickening like crankcase oil in a cold
engine. Your oxygen
consumption, a measure of your metabolic rate, has fallen by more than
a quarter. Your kidneys,
however, work overtime to process the fluid overload that occurred when
the blood vessels in
your extremities constricted and squeezed fluids toward your center.
You feel a powerful urge to
urinate, the only thing you feel at all.
By 87 degrees you've lost the ability to recognize a familiar face,
should one suddenly appear
from the woods.
At 86 degrees, your heart, its electrical impulses hampered by chilled
nerve tissues, becomes
arrhythmic. It now pumps less than two-thirds the normal amount of
blood. The lack of oxygen
and the slowing metabolism of your brain, meanwhile, begin to trigger
visual and auditory
hallucinations.
You hear jingle bells. Lifting your face from your snow pillow, you
realize with a surge of
gladness that they're not sleigh bells; they're welcoming bells hanging
from the door of your
friends' cabin. You knew it had to be close by. The jingling is the
sound of the cabin door
opening, just through the fir trees.
Attempting to stand, you collapse in a tangle of skis and poles. That's
OK. You can crawl. It's
so close.
Hours later, or maybe it's minutes, you realize the cabin still sits
beyond the grove of trees.
You've crawled only a few feet. The light on your wristwatch pulses in
the darkness: 5:20.
Exhausted, you decide to rest your head for a moment.
When you lift it again, you're inside, lying on the floor before the
woodstove. The fire throws off
a red glow. First it's warm; then it's hot; then it's searing your
flesh. Your clothing has caught fire.
At 85 degrees, those freezing to death, in a strange, anguished
paroxysm, often rip off their
clothes. This phenomenon, known as paradoxical undressing, is common
enough that urban
hypothermia victims are sometimes initially diagnosed as victims of
sexual assault. Though
researchers are uncertain of the cause, the most logical explanation is
that shortly before loss of
consciousness, the constricted blood vessels near the body's surface
suddenly dilate and
produce a sensation of extreme heat against the skin.
All you know is that you're burning. You claw off your shell and pile
sweater and fling them
away.
But then, in a final moment of clarity, you realize there's no stove,
no cabin, no friends. You're
lying alone in the bitter cold, naked from the waist up. You grasp your
terrible misunderstanding,
a whole series of misunderstandings, like a dream ratcheting into
wrongness. You've shed your
clothes, your car, your oil-heated house in town. Without this
ingenious technology you're simply
a delicate, tropical organism whose range is restricted to a narrow
sunlit band that girds the earth
at the equator.
And you've now ventured way beyond it.
There's an adage about hypothermia: "You aren't dead until you're warm
and dead."
At about 6:00 the next morning, his friends, having discovered the
stalled Jeep, find him, still
huddled inches from the buried log, his gloveless hand shoved into his
armpit. The flesh of his
limbs is waxy and stiff as old putty, his pulse nonexistent, his pupils
unresponsive to light. Dead.
But those who understand cold know that even as it deadens, it offers
perverse salvation. Heat is
a presence: the rapid vibrating of molecules. Cold is an absence: the
damping of the vibrations.
At absolute zero, minus 459.67 degrees Fahrenheit, molecular motion
ceases altogether. It is this
slowing that converts gases to liquids, liquids to solids, and renders
solids harder. It slows
bacterial growth and chemical reactions. In the human body, cold shuts
down metabolism. The
lungs take in less oxygen, the heart pumps less blood. Under normal
temperatures, this would
produce brain damage. But the chilled brain, having slowed its own
metabolism, needs far less
oxygen-rich blood and can, under the right circumstances, survive
intact.
Setting her ear to his chest, one of his rescuers listens intently.
Seconds pass. Then, faintly, she
hears a tiny sound--a single thump, so slight that it might be the
sound of her own blood. She
presses her ear harder to the cold flesh. Another faint thump, then
another.
The slowing that accompanies freezing is, in its way, so beneficial
that it is even induced at times.
Cardiologists today often use deep chilling to slow a patient's
metabolism in preparation for heart
or brain surgery. In this state of near suspension, the patient's blood
flows slowly, his heart rarely
beats--or in the case of those on heart-lung machines, doesn't beat at
all; death seems near. But
carefully monitored, a patient can remain in this cold stasis,
undamaged, for hours.
The rescuers quickly wrap their friend's naked torso with a spare
parka, his hands with mittens,
his entire body with a bivy sack. They brush snow from his pasty,
frozen face. Then one snakes
down through the forest to the nearest cabin. The others, left in the
pre-dawn darkness, huddle
against him as silence closes around them. For a moment, the woman
imagines she can hear the
scurrying, breathing, snoring of a world of creatures that have taken
cover this frigid night
beneath the thick quilt of snow.
With a "one, two, three," the doctor and
nurses slide the
man's stiff, curled form onto a table
fitted with a mattress
filled with warm water which will be
regularly reheated.
They'd been warned that they had a
profound
hypothermia case coming in. Usually such
victims can be
straightened from their tortured fetal
positions. This one
can't.
Technicians scissor with stainless-steel
shears at the
man's urine-soaked long underwear and shell pants, frozen together like
corrugated cardboard.
They attach heart-monitor electrodes to his chest and insert a
low-temperature electronic
thermometer into his rectum. Digital readings flash: 24 beats per
minute and a core temperature
of 79.2 degrees.
The doctor shakes his head. He can't remember seeing numbers so low.
He's not quite sure how
to revive this man without killing him.
In fact, many hypothermia victims die each year in the process of being
rescued. In "rewarming
shock," the constricted capillaries reopen almost all at once, causing
a sudden drop in blood
pressure. The slightest movement can send a victim's heart muscle into
wild spasms of ventricular
fibrillation. In 1980, 16 shipwrecked Danish fishermen were hauled to
safety after an hour and a
half in the frigid North Sea. They then walked across the deck of the
rescue ship, stepped below
for a hot drink, and dropped dead, all 16 of them.
"78.9," a technician calls out. "That's three-tenths down."
The patient is now experiencing "afterdrop," in which residual cold
close to the body's surface
continues to cool the core even after the victim is removed from the
outdoors.
The doctor rapidly issues orders to his staff: intravenous
administration of warm saline, the bag
first heated in the microwave to 110 degrees. Elevating the core
temperature of an average-size
male one degree requires adding about 60 kilocalories of heat. A
kilocalorie is the amount of
heat needed to raise the temperature of one liter of water one degree
Celsius. Since a quart of
hot soup at 140 degrees offers about 30 kilocalories, the patient
curled on the table would need
to consume 40 quarts of chicken broth to push his core temperature up
to normal. Even the
warm saline, infused directly into his blood, will add only 30
kilocalories.
Ideally, the doctor would have access to a cardiopulmonary bypass
machine, with which he
could pump out the victim's blood, rewarm and oxygenate it, and pump it
back in again, safely
raising the core temperature as much as one degree every three minutes.
But such machines are
rarely available outside major urban hospitals. Here, without such
equipment, the doctor must
rely on other options.
"Let's scrub for surgery," he calls out.
Moments later, he's sliding a large catheter into an incision in the
man's abdominal cavity. Warm
fluid begins to flow from a suspended bag, washing through his abdomen,
and draining out
through another catheter placed in another incision. Prosaically, this
lavage operates much like a
car radiator in reverse: The solution warms the internal organs, and
the warm blood in the organs
is then pumped by the heart throughout the body.
The patient's stiff limbs begin to relax. His pulse edges up. But even
so the jagged line of his
heartbeat flashing across the EKG screen shows the curious dip known as
a J wave, common to
hypothermia patients.
"Be ready to defibrillate," the doctor warns the EMTs.
For another hour, nurses and EMTs hover around the edges of the table
where the patient lies
centered in a warm pool of light, as if offered up to the sun god. They
check his heart. They
check the heat of the mattress beneath him. They whisper to one another
about the foolishness of
having gone out alone tonight.
And slowly the patient responds. Another liter of saline is added to
the IV. The man's blood
pressure remains far too low, brought down by the blood flowing out to
the fast-opening
capillaries of his limbs. Fluid lost through perspiration and urination
has reduced his blood
volume. But every 15 or 20 minutes, his temperature rises another
degree. The immediate
danger of cardiac fibrillation lessens, as the heart and thinning blood
warms. Frostbite could still
cost him fingers or an earlobe. But he appears to have beaten back the
worst of the frigidity.
For the next half hour, an EMT quietly calls the readouts of the
thermometer, a mantra that
marks the progress of this cold-blooded proto-organism toward a state
of warmer, higher
consciousness.
"90.4...
"92.2..."
From somewhere far away in the immense, cold darkness, you hear a
faint, insistent hum.
Quickly it mushrooms into a ball of sound, like a planet rushing toward
you, and then it becomes
a stream of words.
A voice is calling your name.
You don't want to open your eyes. You sense heat and light playing
against your eyelids, but
beneath their warm dance a chill wells up inside you from the sunless
ocean bottoms and the
farthest depths of space. You are too tired even to shiver. You want
only to sleep.
"Can you hear me?"
You force open your eyes. Lights glare overhead. Around the lights
faces hover atop uniformed
bodies. You try to think: You've been away a very long time, but where
have you been?
"You're at the hospital. You got caught in the cold."
You try to nod. Your neck muscles feel rusted shut, unused for years.
They respond to your
command with only a slight twitch.
"You'll probably have amnesia," the voice says.
You remember the moon rising over the spiky ridgetop and skiing up
toward it, toward
someplace warm beneath the frozen moon. After that, nothing--only that
immense coldness
lodged inside you.
"We're trying to get a little warmth back into you," the voice says.
You'd nod if you could. But you can't move. All you can feel is
throbbing discomfort
everywhere. Glancing down to where the pain is most biting, you notice
blisters filled with clear
fluid dotting your fingers, once gloveless in the snow. During the
long, cold hours the tissue froze
and ice crystals formed in the tiny spaces between your cells, sucking
water from them, blocking
the blood supply. You stare at them absently.
"I think they'll be fine," a voice from overhead says. "The damage
looks superficial. We expect
that the blisters will break in a week or so, and the tissue should
revive after that."
If not, you know that your fingers will eventually turn black, the
color of bloodless, dead tissue.
And then they will be amputated.
But worry slips from you as another wave of exhaustion sweeps in.
Slowly you drift off,
dreaming of warmth, of tropical ocean wavelets breaking across your
chest, of warm sand
beneath you.
Hours later, still logy and numb, you surface, as if from deep under
water. A warm tide seems to
be flooding your midsection. Focusing your eyes down there with
difficulty, you see tubes
running into you, their heat mingling with your abdomen's depthless
cold like a churned-up river.
You follow the tubes to the bag that hangs suspended beneath the
electric light.
And with a lurch that would be a sob if you could make a sound, you
begin to understand: The
bag contains all that you had so nearly lost. These people huddled
around you have brought you
sunlight and warmth, things you once so cavalierly dismissed as
constant, available, yours,
summoned by the simple twisting of a knob or tossing on of a layer.
But in the hours since you last believed that, you've traveled to a
place where there is no sun.
You've seen that in the infinite reaches of the universe, heat is as
glorious and ephemeral as the
light of the stars. Heat exists only where matter exists, where
particles can vibrate and jump. In
the infinite winter of space, heat is tiny; it is the cold that is
huge.
Someone speaks. Your eyes move from bright lights to shadowy forms in
the dim outer reaches
of the room. You recognize the voice of one of the friends you set out
to visit, so long ago now.
She's smiling down at you crookedly.
"It's cold out there," she says. "Isn't it?"
Peter Stark is a longtime contributor to Outside. He is the author of
Driving to Greenland
(Lyons & Burford) and is currently at work on a trilogy of travel
memoirs.
Illustrations by Christian Northeast
Copyright 1997, Outside magazine
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