My Page for Hypothermia Fundamentals...
Chuck Sutherland
has a fantastic Coldwater page as well.
Fern Usen compiled this page of information from various
sources and courteously supplied the text.
PREVENTION:
AVOID EXPOSURE
- STAY DRY.
When clothes get wet,
they lose about ninety percent of their insulating value. Wool loses
less as does many of the new synthetics. Cotton and wet down are
worthless.
- BEWARE OF THE WIND.
A slight breeze
carries heat away from bare skin much faster than still air. Wind drives
cold air under and through clothing. Wind refrigerates wet clothes by
evaporating moisture from the surface.
WIND MULTIPLIES THE PROBLEMS OF STAYING DRY. If you have been in the
water and you are wearing a T-shirt that is wet remove it and you will
retain more heat. Direct sunlight on the skin helps in the warming
process.
- UNDERSTANDING COLD.
Most
hypothermia cases develop in air temperatures between 30 and 50 degrees.
Most outdoor enthusiast simply can't believe such temperatures can be
dangerous. They fatally underestimate the danger of being wet at such
temperatures. Fifty degree water is unbearably cold. The cold that kills
is cold water running down your neck and legs, and cold water removing
body heat from the surface of your clothes.
TERMINATE EXPOSURE
If you can not stay dry and warm under existing weather conditions,
using the clothes you have with you, do whatever is necessary to be less
exposed.
- BE SMART ENOUGH TO GIVE UP REACHING THE DESTINATION,
OR WHATEVER YOU HAD IN MIND.
- Get out of the wind and rain.
Build a fire.
Concentrate on making your camp or bivouac as secure and comfortable as
possible.
NEVER IGNORE SHIVERING
Persistent or violent shivering is a clear warning that you are on the
verge of hypothermia.
GET OUT OF WATER & WIND AND BACK TO YOUR VEHICLE.
BEWARE OF EXHAUSTION
Make camp while you still have a reserve of energy. Allow for the fact
that exposure greatly reduces your normal endurance. You may think you
are doing fine when the fact that you are exercising is the only thing
preventing your going into hypothermia. If exhaustion forces you to
stop, however brief:
- Your rate of body heat production instantly drops by fifty percent or
more.
- Violent, incapacitating shivering may begin immediately.
- You may slip into hypothermia in a matter of minutes.
DETECT HYPOTHERMIA
If your group is exposed to WIND, COLD, OR WET, think hypothermia. Watch
yourself and others for the symptoms:
- Uncontrollable fits of shivering.
- Vague, slow, slurred speech.
- Memory lapses, or incoherence.
- Immobile, fumbling hands.
- Frequent stumbling.
- Drowsiness (to sleep is to die.)
- Apparent exhaustion. Inability to get up after a rest.
BE PREPARED
Pack a VHF radio and know how to use the emergency Channel 16 to call
for help.
Carry chemical hot packs and a thermometer in your first aid kit.
TREATMENT
The victim may deny he/she is in trouble. Believe the symptoms, not the
person. Even mild symptoms demand immediate treatment.
- Get the victim out of the wind and rain.
- Strip off all wet clothes.
- If the victim is only mildly impaired:
- Give him/her warm drinks. (only small amounts)
- Get him/her into dry clothes and a warm dry sleeping bag.
Well-wrapped warm thermoses placed in the crotch and under the
arms anywhere the main arteries are close to the surface of the
skin, will hasten recovery.
- If the patient is semi-conscious or worse:
- Try to keep him/her awake. (Do not give hot liquids by mouth.)
- Leave him/her stripped. Put him/her in a sleeping bag with
another person (also stripped) to transfer heat. If you can put
the victim between two donors, skin to skin contact is very
effective treatment.
- Warm the torso only. Not extremities.
- Transport the victim as soon as possible to the closest hospital for
monitoring. It takes a very long time to warm the inner core and only a
rectal hypothermia thermometer is long enough to find out what the inner
core temperature really is. DON'T DELAY!
HYPOTHERMIA IN WATER
Loss of body heat to the water, is a major cause of deaths in boating
accidents. Often the cause of death is listed as drowning; but, often
the primary cause is hypothermia. It should also be noted that alcohol
lowers the body temperature around two to three degrees by dilating the
blood vessels. Do not drink alcohol around cold water. The following
chart shows the effects of hypothermia in water:
|
WATER TEMPERATURE
|
EXHAUSTION
|
SURVIVAL TIME
|
|
32.5 degrees
|
Under 15 min
|
Under 15 to 45 min.
|
|
32.5 to 40
|
15 to 30 min
|
30 to 90 min.
|
|
40 to 50
|
30 to 60 min
|
1 to 3 hrs.
|
|
50 to 60
|
1 to 2 hrs
|
1 to 6 hrs.
|
|
60 to 70
|
2 to 7 hrs
|
2 to 40 hrs.
|
|
70 to 80
|
3 to 12 hrs
|
3 hrs. to indefinite
|
|
Over 80
|
Indefinite
|
Indefinite
|
NOTE: THIS MEANS THAT NOW, WITH WATER TEMPS AROUND 50f, YOU
HAVE BETWEEN 30 MINUTES & 3 HOURS SURVIVAL TIME. SCARED? YOU SHOULD
BE.
PFD's (personal flotation devices / better known as life jackets) can
increase survival time because of the insulating value they provide. In
water less than 50 degrees you should wear a wet suit or dry suit to
protect more of the body.
SOME POINTS TO REMEMBER:
- While in the water , do not attempt to swim unless to reach nearby
safety. Unnecessary swimming increases the rate of body heat loss. Keep
your head out of the water. This will increase your survival time.
- Keep a positive attitude about your rescue. This will increase your
chances of survival.
- If there is more than one person in the water, huddling is
recommended.
- Always wear your PFD. It won't help if you don't have it on.
BODY HEAT LOSS
The body loses heat in five ways: Respiration, Evaporation, Conduction,
Radiation and Convection. The body cools up to 25 times faster in water
than in air.
- RESPIRATION: Heat escapes when air is exhaled. This can be reduced by
covering the mouth and nose area with wool or any article of clothing.
- EVAPORATION: Perspiration evaporates from the skin and moisture from the
lungs contributes to heat loss by the body. Control the amount of
evaporation by wearing clothing that can be ventilated or taken off.
Wear clothing that will not absorb water, but will breathe. So you can
control the cooling effect of evaporation.
- CONDUCTION: Sitting on the ground, snow, touching cold equipment, or
being rained upon are all examples of how heat can be lost through
conduction. If you become wet a large amount of body heat is lost
rapidly. Perspiration or rain should never be allowed to saturate your
clothing which can reduce their insulating values.
Wear clothing that will keep you warm even if it is wet, such as wool or
some of the new synthetic materials (polypropylene, polorguard,
fiberfill, quollofil) have good wet characteristics. Sit on a
closed-cell insulating pad.
- RADIATION: Radiation causes the largest heat loss from uncovered skin,
particularly the head, neck, and hands. It is important to cover these
areas in keeping warm and preventing further heat loss.
- CONVECTION: The primary function of clothing is to keep a layer of warm
air next to the skin, but allows water vapor (perspiration) to pass
outward. The body continually warms this layer of air close to the body.
A wet suit uses this same theory, but when a person falls into the water
you are chilled for a few moments before the water next to your skin is
warmed by your body. A dry suit has less initial shock because water
does not get inside to start with so the clothing you wear under the dry
suit captures the air to retain your warmth. Heat is lost rapidly with
the slightest breeze unless you wear a nylon or gortex shell over your
clothing to prevent the warm air from being lost. The cooling effect of
wind chill is equal to that of much lower temperatures due to the
increased evaporation and convection. You must have wind protection and
good insulating value (dead air space) for your clothing to retain your
body heat at a safe level.
COLD WATER KILLS
Safety experts estimate that half of all drowning victims actually die
from the fatal effects of cold water, or hypothermia, and not from water
filled lungs. Loss of body heat is one of the greatest hazards to
survival when you fall overboard, capsize, or jump into the water. Cold
water robs the body of heat 25-30 times faster than air. When you lose
enough body heat to make your temperature subnormal, you become
hypothermic.
Sudden immersion in cold water cools your skin and outer tissues very
quickly . Within 10 or 15 minutes, your core body temperature (brain,
spinal cord, heart, and lungs) begins to drop. your arms and legs become
numb and completely useless.
You may lose consciousness and drown before your core temperature drops
low enough to cause death.
RULES OF 50
- - An average adult person has a 50/50 chance of surviving a 50 yard
swim in 50 degree F. water.
- - A 50 year old person in 50 degree F water has a 50/50 chance of
surviving for 50 minutes
BODY HOT SPOTS
Certain areas of your body are "hot spots" that lose large amounts of
heat faster than other areas. These "hot spots" need special protection
against heat loss to avoid hypothermia. The head and neck are the most
critical areas. The sides of the chest, where there is little fat or
muscle, are major areas of heat loss from the warm chest cavity. The
groin region also loses large amounts of heat because major blood
vessels are near the surface.
HOW COLD IS "COLD WATER"?
Cold water does not have to be icy... it just has to be colder than you
are to set water hypothermia in motion. A person who is wet, improperly
dressed and intoxicated can become hypothermic in 70 degree F weather.
The rate of body heat loss depends on water temperature, the protective
clothing worn, percent body fat and other physical factors, and most
importantly the way you conduct yourself in the water.
Note: Much of Alaska's waters are Very cold! Many of the larger bodies
of water, rivers, and all marine waters are in the low 40s (Fahrenheit).
Without a survival suit a person loses functional use of their limbs
within minutes. Unconsciousness soon follows.
Different activities in the water consume varying amounts of body heat.
The more energy (heat) you expend, the quicker your body temperature
drops, reducing your survival time. As shown below wearing a life jacket
(PFD) can add hours to your survival time.
Predicted Survival Time
(average adult in 50 degree F (10 C) water)
|
|
*Drown Proofing |
1 1/2 hours
| |
Swimming slowly |
2 hours
| |
Treading water |
2 hours
| |
Holding still |
2 3/4 hours
| |
**H.E.L.P. position |
4 hours
| |
Huddle |
4 hours
| |
Wearing a PFD |
7 hours
|
|
*drown proofing is a warm water survival technique:
to conserve energy you relax in the water and allow your head to submerge
between breaths. This technique is NOT recommended in cold water, since
about 50 % of heat loss is from the head.
|
|
|
**Heat Escape Lessening Position:
|
- arms folded across the chest
- ankles crossed
- thighs close together
- knees bent.
|
|
HOW TO SURVIVE IN COLD WATER
If you suddenly find yourself in the water don't panic! Calmly follow
the procedure below to increase your survival time.
Minimize body heat loss. This is the single most important thing you
should do. Take the following steps:
- Do not remove clothing, despite what you may have been told.
Instead, button, buckle, zip and tighten collars, cuffs, shoes and
hoods. Cover your head if possible. A layer of water trapped inside your
clothing will be slightly warmed by your body and help insulate you from
the colder water, slowing your rate of body heat loss. Put on a PFD if
available.
- Devote all your efforts to getting out of the water. Act quickly
before you lose full use of your hands and limbs. Climb onto a boat,
raft, or anything floating. Right a capsized boat and climb in. Most
boats will support you even if full of water. If you can not right a
capsized boat climb on top of the hull. The object is to get as much of
yourself out of the water as possible.
- Do not attempt to swim unless it is to reach a nearby boat, another
person, or a floating object on which you can climb or lean. Unnecessary
swimming "pumps" out warmed water between your body and your clothing
circulating new cold water to take its place. Unnecessary movement of
your arms and legs pumps warm blood to your extremities, where it cools
quickly, reducing your survival time by as much as 50%.
- If you can't get out of the water try one of the following survival
techniques:
- Heat Escape Lessening Position (H.E.L.P) hold knees to chest to protect
trunk of body from heat loss. Wrap arms around legs and clasp hands
together. Keep head up.
- Huddle, huddling together with 2 or more people will extend survival
time 50% longer than swimming or treading water.
- Remain as still as possible, however painful. Intense shivering and
severe pain are natural body reflexes in cold water which will not kill
you but heat loss will.
FIRST AID FOR HYPOTHERMIA
Any person pulled from cold water should be treated for hypothermia..
Your goal in treating hypothermia is to prevent further body cooling.
Severe cases call for rewarming by trained medical personnel. In all
cases, arrange to have the victim transported to a medical facility
immediately.
What To Do:
- Gently move the victim to warm shelter.
- Check breathing and heartbeat. In cases of hypothermia you should check
very closely for as long as two minutes.
- Start CPR if necessary.
- Remove victim's clothing with a minimum of movement, cut them away if
necessary. Lay victim in a level face up position with a blanket or
other insulation beneath them.
- Wrap victim in warm blankets, sleeping bag or other warm covering.
- If there will be a long delay before victim arrives at a medical
facility use the following rewarming techniques:
- Apply heating pads or hot water bottles (wrapped in a towel to prevent
burns) to the head , neck, chest, and groin.
- Do not apply heat to arms and legs or give them a hot
bath. This forces blood out through the cold extremities and back to the
heart, lungs and brain, which will further drop the core temperature.
This can cause "after drop" which can be fatal.
- Do not massage or rub the victim, rough handling may cause
cardiac arrest.
- Apply warmth by direct body to body contact. Have someone remove their
own clothes and lay next to victim skin to skin. Wrap both in blankets.
- If person is alert enough you can give them hot drinks. If they are
unconscious or stuporous do not give them anything to drink. Never give
alcoholic beverages.
COLD WATER DROWNING
Some apparent drowning victims may look dead, but may actually still be
alive! A phenomenon called the "mammalian diving reflex" can be
triggered by cold water. This reflex, common to whales, porpoises and
seals, shuts off blood circulation to most parts of the body except the
heart, lungs and brain and slows the metabolic rate. What little oxygen
remains in the blood is circulated where it is needed most. Do not
assume that a person who is cyanotic and who has no detectable pulse or
breathing is dead. Administer CPR and transport the victim to a medical
facility as quickly as possible for specialized rewarming and revival
techniques. Most the waters of Alaska are cold enough at any time of
year to trigger this reflex. People have been revived after having been
submerged for extended periods, some in excess of 45 minutes! So don't
give up.
THE WARNING SIGNS OF HYPOTHERMIA
These are some of the symptoms of hypothermia. A person who is suffering
from exposure (or extreme low temperatures) may demonstrate some or all
of these symptoms:
- Shivering (an early warning sign of hypothermia), which means the
body is trying to warm itself.
- Increased heart rate and faster breathing.
- Cold white hands and feet, which means that the body is diverting
blood from the person's extremities to try to keep the internal organs
warm.
- Irritable, irrational, and/or confused behavior. It is usually hard
for people who are suffering from these symptoms to recognize their own
condition, so you might have to spot it for them.
- Blue colored lips or skin (an indication the hypothermia is getting
severe.)
- Sometimes people with hypothermia will feel hot, and start removing
their protective clothing. (Don't let them do it.)
- Eventual unconsciousness.
SEVERE HYPOTHERMIA
- A victim of advanced hypothermia must be treated as a medical
emergency. If the victim is getting stiff and is either unconscious or
showing signs of clouded consciousness such as slurred speech or severe
loss of coordination, transport the patient to a medical facility where
aggressive re-warming can be safely initiated, or radio for help.
- Ordinarily, let the hospital re-warm a severely hypothermic person due
to physiological complications. However, on a trip, you will not likely
have immediate access to medical facilities. Wrap the person warmly and
transport to safety. Carry the victim as gently as possible, perhaps in
the kayak or canoe, to shelter. Jostling the patient may cause cardiac
arrest.
- Remove wet clothing. Place in a dry sleeping bag and join him or her
to maximize heat generation. Once shivering has stopped, the patient has
lost the ability to generate heat, so simply wrapping in a cold bag will
not help. He or she needs a gentle source of heat, like another human
body. Apply hot packs to the neck, armpits, sides, chest and groin. Keep
the head covered. Warm the victim's lungs by mouth-to-mouth breathing.
- Do not warm, rub or stimulate the severely hypothermic patient's
extremities. This may bring cold, stagnant blood from the body surface
to the body core, resulting in cardiac arrest. Hot drinks are also
dangerous as they draw warm blood away from vital organs. Nearly 3
gallons would be needed to raise core body temp 1 degrees C.
- Things to look out for as you re-warm a severely hypothermic person
include a condition called temperature afterdrop which occurs as the
body is re-warmed and cold blood from the extremities returns to the
body core, resulting in another 1-2 degrees C core temperature drop.
Acidosis occurs as the acid waste products from cell metabolism in the
extremities is returned to the heart, which may result in re-warming
shock. Both afterdrop and acidosis may precipitate cardiac arrest.
- Bystanders may be tempted to start CPR on a severe case as it is very
difficult in the field to distinguish between severe hypothermia and
cardiac arrest. But chest compressions or any other rough handling of a
severely hypothermic person are particularly likely to convert a slow,
low output heart rhythm into ventricular fibrillation, a form of heart
attack. Check for any body movement or respiratory effort, both of which
are lacking in a heart attack victim, and feel for a carotid pulse (in
the neck, to the side of the windpipe) for a full minute before
initiating CPR.
KNOW YOUR PADDLING PARTNERS - MANAGE RISK
- Susceptibility to hypothermia depends not only on the conditions of
exposure but also on body size.
- Children are considerably more susceptible than large adults.
- Older folks generally more than young.
- Thin people are more susceptible than fat.
- Men more so than women due to a generally smaller subcutaneous fat layer.
- Alcohol and drugs may impair shivering or dilate surface blood vessels,
thereby masking symptoms or interfering with blood shunting.
- Certain medical conditions may make a person particularly susceptible to
hypothermia, such as: hypothyroidism, in which too little thyroid
hormone (regulates cellular metabolic rate) is produced (older people);
diabetes (low blood sugar)
