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Hypothermia. Malcolm Cunningham. Definition of Hypothermia. “A decrease in the core body temperature to a level at which normal muscular and cerebral functions are impaired” (Medicine for Mountaineering ). How we lose heat to the environment. Radiation Conduction
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Hypothermia Malcolm Cunningham
Definition of Hypothermia “A decrease in the core body temperature to a level at which normal muscular and cerebral functions are impaired” (Medicine for Mountaineering )
How we lose heat to the environment • Radiation • Conduction • water conducts heat away from the body 25 times faster than air • Stay dry = stay alive! • Convection • wind chill • Evaporation • sweating • insensible perspiration • respiration
Conditions Leading to Hypothermia • Cold temperatures • Improper clothing and equipment • Wetness particularly with wind • Fatigue, exhaustion • Dehydration • Poor food intake • No knowledge of hypothermia • Alcohol intake - causes vasodilatation leading to increased heat loss
Times & Places where Hypothermia is Possible • Above the bushline • Leaving the bush after a sweaty climb Rain with wind Snowing particularly driven wet and sleety snow • During and after river crossings • Extended in-river travel
Avoiding Hypothermia • Never wear cotton • Never wear jeans or cotton trousers • Wear wool, polyprop, pile or similar • Put on your parka early • Put on a hat • Put on gloves & overmittens • Put on overtrou – best over long-johns or pile • Have some food • If you’re cold warn your leader early • Look out for others • Choose your leader carefully
"-Umbles" stumbles, mumbles, fumbles, & grumbles which show changes in motor coordination and levels of consciousness
Mild Hypothermia • core temperature 37 – 35.6 oC • Shivering - not under voluntary control • Can't do complex motor functions (ice climbing or skiing) can still walk & talk • Vasoconstriction to periphery
Moderate Hypothermia • core temperature 35.6 – 33.9 oC • dazed consciousness • loss of fine motor coordination - particularly in hands - can't zip up parka, due to restricted peripheral blood flow • slurred speech • violent shivering • irrational behaviour • "I don't care attitude"
Severe Hypothermia • core temperature 33.9 - 30 oC and below (immediately life threatening) • Shivering ceases • Person falls to the ground, can't walk, curls up into a fetal position to conserve heat • Muscle rigidity develops • Skin is pale • Pupils dilate • Pulse rate decreases • at 32 oC the body shuts down all peripheral blood flow and reduces breathing rate and heart rate • at 30 oC the body is in a state of "metabolic icebox." Person looks dead but is still alive
Death from Hypothermia • Breathing becomes erratic and very shallow • Semi-conscious • Cardiac arrythmias develop, any sudden shock may set off Ventricular Fibrillation • Heart stops, death
Treating Mild - Moderate Hypothermia • reduce heat loss • add fuel & fluids • add heat
1. Reduce Heat Loss • additional layers of clothing • dry clothing • increased physical activity • shelter
2. Add Fuel & Fluids • give food • give hot liquids • avoid alcohol • avoid caffeine - a diuretic - causes water loss increasing dehydration
3. Add Heat Body to body contact. Get into a sleeping bag, in dry clothing with a person in lightweight dry clothing
Treating Severe Hypothermia • Reduce Heat Loss • Add Fuel & Fluids • Add Heat
1. Reduce Heat Loss • provide a shell of total insulation for the patient. Use multiple sleeping bags Include an aluminum "space" blanket to help prevent radiant heat loss • Make sure the patient is dry • has a polypropylene layer to minimize sweating on the skin • don't put him/her naked in a sleeping bag with another person.
2. Add Fuel & Fluids • Warm Sugar Water - for people in severe hypothermia, the stomach has shut down but can absorb water and sugars. Give a dilute mixture of warm water with sugar every 15 minutes. • Urination – bladder is fuller & body heat wasted on keeping it warm.
3. Add Heat • heat can be applied to transfer heat to major arteries - at the neck for the carotid, at the armpits for the brachial, at the groin for the femoral, at the palms of the hands for the arterial arch • use hot water bottles, warm rocks, towels, compresses • rescue breathing can increase oxygen and provide internal heat
Some Off-Track Principles 1. Always understand the lay of the land around you 2. Travel on ridges 3. When leaving the main range to go down a ridge: (a) study your map carefully and decide which ridge you will go down (b) before proceeding take time to confirm you are at the right place to startdown 4. Walk down the ridge on a compass bearing 5. Be aware of where the sun should be 6. Never, never go down a stream or a gully unless you know it 7. Ridges broaden at the bottom. Work hard to stay out of gullies 8. If you come to a Y climb out sideways to find another ridge 9. If you slip off the ridge climb straight back up, don’t sidle 10. If you’re on an old track it’s worth working hard to stay on it 11. In untracked rivers walk the flats and climb and sidle the gorges 12. BUT sidling is fraught. Check the map to see how to minimise problems (is there a terrace? Is there a shoulder to climb through at the collar bone?)