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Production of Heat
- 1. Exertion
- 2. Shivering
- 3. Food Ingestion
- 4. Fever
- 5. Cold Stress
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Impairments of Thermoregulation
- 1. Age extremes
- 2. malnutrition
- 3. sleep deprivation
- 4. fatigue - affects hypothal's ability to autoregulate temp
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Physical Responses to cold
- 1. peripheral vasocontriction - increases risk to freezing
- 2. hunting reflex - blood vessels relax every 3-5 minutes in a cyclic fashion to protect extremeties- genetically variable
- 3. cold-induced diuresis - more blood through kidneys, higher GFR....hypervolemia secondary to vasoconstriction. **risk of dehydration
- 4. cold air can lead to increased respiratory water loss = insensible loss
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Chilblains (pernio)
- cause: repeated exposure of bare skin to cold weather with high humidity
- symptoms: swollen, red, hot, tender, itchy skin
- treatment: warm with body heat, no rubbing or intense heat
- -rubbing with ice crystals- damage cells, so more important in frostbite
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Prevention of Chilblains
- 1. do not remove clothing after exertion in extreme cold environment
- 2. good gloves, no cotton clothing
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Cause of Hypothermia
Cause: prolonged exposure to body heat loss, can occur in warmer environments if pt is wet
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Hypothermia Pathophysiology
- Transmitted to hypothal via lateral spinothalamic tract to cause:
- 1. increase metabolic rate, bp, muscle tone
- 2. shivering -
- 3. tachnypea
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Clinical Signs of Hypothermia
- 1. mental status changes**
- 2. ataxia
- 3. paradoxical undressing
- 4. hypotension, bradycardia (nothing will work except warming to fix)
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Hypothermia Treatment - Mild
- 1. dry them
- 2. insulate them
- 3. passive warming
- 4. calories
- 5. warmed fluids
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Hypothermia - Moderate to Severe
- 1. ABCs
- 2. move pt as little as possible
- 3. prevent heat loss
- 4. body warming oreo
- 5. heat pack to neck, axilla, groin
- 6. volume resuscitation with warm fluids
- 7. warmed humidified 02
more active warming instead of passive
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Rewarming Techniques
- 1. Passive External
- 2. Active External - warmed blankets, oreo, water bath, hot packs
- 3. Active Internal - cardiopulmonary bypass...take out blood, warm, and put back in
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Hypothermia Prevention - C.O.L.D.
- C:lean
- O:avoid overheating
- L:loose, layers
- D:ry
-also hydration, nutrition, work-rest cycles
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Important Physiological Changes at different Temps (35, 33, 31, 29)
- 37.0:NormalTemp
- 36.0:IncreasedMetabolicRate,BP,muscletone
- 35.0:Maximumshiveringresponse
- 34.0:Poorjudgment,dysarthria,tachycardia
- 33.0:Ataxiaandapathy;tachypnea
- 32.0:Stupor
- 31.0:Extinguishedshiveringthermogenesis
- 30.0:Atrialfibrillation;poikilothermia
- 29.0:Decreasedventricularfibrillationthreshold
- 27.0:Lossofreflexesandvoluntarymotion
- 26.0:Majoracid-‐basedisturbances;areflexia
- 18.0:Asystole
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Cellular Phase of Frostbite
- - extracellular and intracellular ice formation
- - cell dehydration and shrinkage
- - abnorm intracell electrolytes
- - denaturing of lipid-protein complexes
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Four Pathologic Phases of Frostbite
- 1. Prefreeze: plasma leakage, vasospacicity
- 2. freeze-thaw: ice crystal formation
- 3. vascular stasis: dilation, stasis coag, shunting, same symptoms as prefeeze too
- 4. late ischemic phase: thrombosis and AV shunting, ischemia, gangrene, autonomic dysfunction
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fristnip, superficial, and deep frostbite
- - depends on tissue level, superficial heals on it's own, deep doesn't heal well.
- - deep freeze joints, no capillary refill
- - clear vs hemorrhagic blisters
- - edema vs, no edema
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Management of Frostbite
- 1. **prevent freeze thaw refreeze**
- 2. rapid rewarming*
- 3. unroof clear blisters
- 4. narcotics*
- 5. hydrotherapy
- 6. hyperbaric oxygen therapy* - increase p02
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Trenchfoot
- warm, cold, warm, cold
- vasoconstriction and ischemic tissue
- rest and narcotics
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Snow Blindness
- Cause: intense UV light from snow reflection
- -get out of sun, eye will heal
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