Cold-Related Injuries #3

FUEL AND WATER REQUIREMENTS TO STAY WARM

How much food/fuel and water do we need on a daily basis, not only live, but to be able to maximize our performance?  Dehydration may not rapidly lead to death but, it will definitely decrease and impair normal physical and mental abilities.  So, to be at our best we have to stay well hydrated and well fed - fuel to burn.

NUTRITIONAL REQUIREMENTS = average of 2500 CALORIES/DAY

Carbohydrate = 4cal/gram 60%
    (200 - 400 grams/day = 1200 -1600 cal/day)
Fat   = 9cal/gram  10%
    (20 - 60 grams/days = 180 - 540 cal/day)
Protein = 4cal/gram  30%
    (30 - 55 grams/day  = 120 - 220 cal/day)

Number of calories required varies with activity:
Normal daily activity:  2000 - 2500 calories/day.
Winter outdoor sports:  3000 - 4000 calories/day
High altitude mountaineering:  4000 - 6000 calories/day.

HYDRATION REQUIREMENTS = average of 2 LITERS/DAY

Normal water losses per day:  
Insensible loss:   nl temp.    hot temp.     heavy exercise
Skin  =      350ml          350ml           350ml
Respiration  =      350ml          250ml           650ml
Sweating  =     100ml         1400ml         5000ml
Urination  =    1400ml         1200ml          500ml
Defecation  =      100ml         100ml           100ml
TOTALS        2300ml      3300ml        6600ml

Water requirements will vary with activity, sweat output, and altitude.
Exertional sweat loss is 1 - 3 liters/hour for up to 4 hours without replacement.
        (can lose up to 3 liters per hour for 4 hours = 12 liters or 3 gallons = 24 pounds)
Altitude has a very low vapor pressure = will lose 1 cup/hour via respirations.
            (or 24 cups/24 hours = 6 quarts or liters)                                                     
        
LIFE AT ALTITUDE:
O - 8000 feet  = normal elevations for humans to live within.
8000 - 14000 feet = upper limits of sustainable life.
14000 - 18000 feet (½ atmosphere) = high altitude, can visit.
18000 - 28000 feet very high altitude, constant negative deficit, the death zone.

More detailed information in the Jan/Feb 2004 issue of the Wilderness Medicine Newsletter.

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Cold-Related Injuries #2

THE HUMAN ANIMAL

How do we stay warm? How do we produce heat? How do we regulate our core temperature?

Heat Regulatory Mechanism:
We “evolved” in the tropics and subtropics.
Therefore, we have a very sensitive and efficient heat regulatory mechanism.
We are naked, hairless, with sweat glands.
All warm-blooded animals use the evaporation of water to cool. 
Humans sweat; the evaporation of water off the skin cools the skin and blood.
Fur-covered mammals & birds pant, evaporating water out of the lungs thus cooling the pulmonary circulation.

Heat Production and Heat Loss

Heat Production: 
Basal metabolism, we burn glucose as a fuel to produce heat.
Metabolic activity set by thyroid, can be increased 5x’s.
Exercise - muscle activity.
Voluntary or involuntary = shivering, increases up to 10x’s.

Heat Conservation: 
Vasoconstriction in the skin.
Piloerection - hair stands on end.
Abolition of sweating.
           
Heat Loss: 
Conduction:  Transfer of heat from one solid object to another. 
0% - 40%  depending upon the type of solid material
Convection:  Transfer of heat from a solid object into the air or water. 
0% - 40% depending upon air penetration
Radiation:   Transfer of heat by infrared radiation. 
5% - 80% depending upon surrounding temperature
Evaporation:  Transfer of heat by the evaporation of water. 
0% - 90% depending upon vapor pressure & moisture

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Cold-Related Injuries #1

FROSTBITE

We have just seen our first case of frostbite for this winter season.  An individual spent most of the night outside, barefoot, at about 20F.  They have a combination of superficial frostbite and immersion foot and may lose their toes– only time will tell.  Thus, we are inspired to produce several blogs that will deal with the recognition and management of Frostbite and the non-freezing cold injuires - Immersion Foot and Raynaud’s Disease. 

But first prevention:

WINTER WISDOM:  The Principles of Prevention of Hypothermia and Frostbite:
Know your personal limits and equipment.
Have proper-fitting clothing and boots.
Beware of tight-fitting boots or crampons.
Wear multiple layers, including socks.
Carry spare mittens and socks.
Control the rate of sweating.
Keep extremities WARM & DRY.
Keep the whole body warm, dry, well-fed, and well-hydrated.
Drink more than you think you need; do not rely on thirst to tell you to drink.
Carry and eat lots of carbohydrates; you burn glucose to stay warm.
React quickly to the very first signs of cold, numbness, or tissue changes.

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High Altitude Illness

Post #1 of 6:

The most recent issue of the Wilderness Medicine Newsletter, Nov/Dec 2006, is dedicated to the recognition and management of high altitude illnesses. To follow is a series of postings regarding high altitude illnesses, recognition, and management.

What is High Altitude?
The scientific consensus for the definitions of altitude are:

High altitude: 1500 - 3500m (5000 - 11500ft)
Very High Altitude: 3500 - 5500m (11500 - 18000ft)
Extreme High Altitude: above 5500m (18000ft)
18,000′ (5500m) is ½ atmosphere

What are the RISKS of HIGH ALTITUDE MOUNTAINEERING?

As you go Higher it gets COLDER & DRYER, less and less OXYGEN, and more and more UV LIGHT that combing to CAUSE:

Dehydration (exhale 250cc of water per hour or 6 liters per day)
Hypothermia (may need up to 6000 calories per day)
Frostbite (dehydration contributes to the risk of frostbite)
Snow blindness (UV light concentration increases 4% every 1000′)
Severe sunburn (UV light concentration increases 4% every 1000′)
Acute Mountain Sickness (signs of lack of acclimatization)
High Altitude Pulmonary Edema (wet lungs)
High Altitude Cerebral Edema (wet brain)

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Myth#13

Frozen Mythbusters: Myth #13 of 13.
There are a variety of myths regarding human response to cold exposure.  These myths are explained and debunked by Dr. Murray Hamlet, DMV, Dr. Gordon Giesbrecht, PHD, and Frank Hubbell, DO.  After posting the thirteen myths, a complete article  from the Wilderness Medicine Newsletter will be loaded for anyone interested in all the chilly little details.
Myth #13
           Exposing the patient to remove cold, wet clothing will cause a large drop in their core temperature.
           I have heard it stated many times that you cannot strip a person out of their cold, wet clothes in the field because this will cause their core temperature to plummet. This simply is not true. These patients are already vasoconstricted in the peripheral circulation, (i.e. the skin), so unless they are allowed to lie around naked for 10 minutes, they are not going to cool off. It is much more important for them to be dry and reinsulated with dry clothing than to remain cold and wet.
             I have heard it taught in the past that you should leave them wet, that they will warm the water next to their skin and will stop losing body heat, just like in a wet suit. First of all, you do continue to lose heat in a wet suit; it is just slower than without it. As long as these patients are damp, moist, or wet, they will continue to lose heat much more than if they are dry.
             Busted - Hypothermics have to be dry to be warm. Do not hesitate to strip them out of wet, moist, or damp clothing, right down to their bare skin, and then protect them with dry clothing or insulation.

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Myth#12

Frozen Mythbusters: Myth #12 of 13.
There are a variety of myths regarding human response to cold exposure.  These myths are explained and debunked by Dr. Murray Hamlet, DMV, Dr. Gordon Giesbrecht, PHD, and Frank Hubbell, DO.  After posting the thirteen myths, a complete article  from the Wilderness Medicine Newsletter will be loaded for anyone interested in all the chilly little details.
Myth #12
              There is no such thing as “after drop” while rewarming a hypothermia victim.
             Busted - Both Murray and Gordon have clearly shown in their research that we can anticipate that as the hypothermia victim is rewarmed, initially their core temperature will continue to drop another degree or more before they turn the corner and begin to rewarm. This is caused by blood-flow being re-established to the colder peripheral circulation. As this blood cools in the periphery and returns to the core, it will cause a temporary drop in core temperature.

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Myth#11

Frozen Mythbusters: Myth #11 of 13.
There are a variety of myths regarding human response to cold exposure.  These myths are explained and debunked by Dr. Murray Hamlet, DMV, Dr. Gordon Giesbrecht, PHD, and Frank Hubbell, DO.  After posting the thirteen myths, a complete article  from the Wilderness Medicine Newsletter will be loaded for anyone interested in all the chilly little details.
Myth #11
              The best way to rewarm a hypothermia victim is to place them naked in a sleeping bag with a warm naked rescuer so they can share body heat.
        

          Busted - The hypothermia victim is cold and vasoconstricted so they will not absorb heat through their pale, cold skin. The second problem occurs when the warm rescuer begins to overheat and sweat. They will now get the hypothermia victim damp which will increase heat loss.
            Remember, one very effective way to rewarm a mildly hypothermic victim (who is shivering vigorously) is to keep them shivering and harness the heat with adequate insulation. Concentrate your efforts on getting them dry and keeping them dry. Put them in a good thermal capsule, a hypothermia wrap, and feed them sickly sweet liquids to maintain blood sugar. If unconscious, do not try to feed them, and do your best to provide an external source of heat.

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Myth#10

Frozen Mythbusters: Myth #10 of 13.
There are a variety of myths regarding human response to cold exposure.  These myths are explained and debunked by Dr. Murray Hamlet, DMV, Dr. Gordon Giesbrecht, PHD, and Frank Hubbell, DO.  After posting the thirteen myths, a complete article  from the Wilderness Medicine Newsletter will be loaded for anyone interested in all the chilly little details.
Myth #10
             They are not dead until they are warm and dead.
             This is always an interesting statement that does require a certain amount of common sense. In other words, there are limits. If you pull someone out from under the ice after 18 hours or dig them out of an avalanche after 24 hours, there is no hope of resuscitation.
Always, always, always, keep the rescue team in mind. Do not put their lives at risk in a heroic, dramatic resuscitation effort when the chances of recovering are zero.
           Busted - It is a nice dramatic-sounding maxim, “not dead until warm and dead,” but if they are found dead and have been dead for a while, they will remain dead. Please, do not put the lives of others at risk to appear to be a hero. Remember, as Murray Hamlet says: “You’re never dead until you are warm and dead…unless you are cold and dead.”

This blog is powered by the Wilderness Medicine Newsletter, now celebrating 20 years of publication. The WMN is published and distributed online six times each year by TMC Books, and subscriptions cost as little as $10 per year. To find out more, or to subscribe online, click here.

Myth#9

Frozen Mythbusters: Myth #9 of 13.
There are a variety of myths regarding human response to cold exposure.  These myths are explained and debunked by Dr. Murray Hamlet, DMV, Dr. Gordon Giesbrecht, PHD, and Frank Hubbell, DO.  After posting the thirteen myths, a complete article from the Wilderness Medicine Newsletter will be loaded for anyone interested in all the chilly little details.
Myth #9  
           If a hypothermia victim is found pulseless and breathless, you should immediately begin CPR and access ACLS as soon as possible.
           There are several problems with this myth. The first: is the patient truly breathless and pulseless or simply in a metabolic icebox due to a low core temperature? The human body will continue to shiver, in an effort to rewarm itself, until its core temperature has dropped below 86ºF (30ºC), or until it runs out of blood sugar (fuel to burn) which typically takes many hours.
           As the core temperature drops below 90ºF (32ºC), shivering will occur in short bursts and slowly fail completely around 86ºF (30C). At this point patients go into a state of suspended animation, similar to a hibernating bear. Respirations slow to 3 - 6 per minute, the demand for O2 greatly decreases because of the slowed metabolism, and the heart rate also slows to about 40 beats per minute. Respirations, being very slow and shallow, are difficult to observe; the heart rate has slowed; blood pressure has dropped; and the blood is now 190% thicker than normal making it very hard to palpate a pulse and impossible to hear the heart valves close. So, the patients may appear breathless and pulseless when they are not. They will most likely be curled up into the fetal position to help protect core temperature. If you gently pull on their arm, it will slowly extend, and if you let it go, it will curl back in, because it takes life to contract a muscle.
              If you place a cardiac monitor on these folks, it will show a sinus bradycardia possibly with Osborn, “J” waves. Do not misinterpret this as pulseless electrical activity. The problem is simple: once you begin CPR, you will most likely cause ventricular fibrillation. The cold myocardium is very fragile and does not like to be jostled and bumped around.
              If they go into ventricular fibrillation, you have a major problem because it is very hard to defibrillate a cold heart through a cold chest wall. Additionally, no one knows how cardiac medications behave in these cold temperatures. All medication research is done at normal core temperature so we do not know how these drugs will react at subnormal core temperatures. Circulation is very poor at best, so any ACLS drugs given tend to first accumulate in the central circulation, then are released as a bolus causing a drug overdose as the patient approaches normal core temperature.
           Busted - Do not begin CPR unless you are certain that they are in asystole or ventricular fibrillation. Once you do start CPR, you have now set the clock to definitive care because if they are not there already, they will most likely go into ventricular fibrillation from the chest compressions.
           So, what should you do? First and foremost, DO NOT HURRY. Handle the patient gently as rough handling can precipitate ventricular fibrillation. Protect them from the environment, and place them in a hypothermia wrap. If conscious give them warm, sickly sweet fluids; if unconscious, do gentle, slow rescue breaths, one every 10 seconds. This will provide them with warm (98.6ºF/37ºC), moist (100%) air. Remember that the rescue breaths need to be long and slow as the chest wall is cold and slow to expand.

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Myth #8

Frozen Mythbusters: Myth #8 of 13.
There are a variety of myths regarding human response to cold exposure.  These myths are explained and debunked by Dr. Murray Hamlet, DMV, Dr. Gordon Giesbrecht, PHD, and Frank Hubbell, DO.  After posting the thirteen myths, a complete article from the Wilderness Medicine Newsletter will be loaded for anyone interested in all the chilly little details.
Myth #8
           Hypothermia is an absolute emergency.
           This is a typical mindset for both rescue as well as emergency department personnel. It is important for us to remember that hypothermic patients have normal physiology for their core temperature. They are very stable, if handled properly, and there is no need to hurry unnecessarily. In fact, rushing to do something is probably the worst thing to do.
          Busted - Hypothermia is a medical condition that needs to be treated properly to help these patients regain normal core temperature. But, it is not an emergency; time is on their side.

This blog is powered by the Wilderness Medicine Newsletter, now celebrating 20 years of publication. The WMN is published and distributed online six times each year by TMC Books, and subscriptions cost as little as $10 per year. To find out more, or to subscribe online, click here.