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Four Phases of cold water immersion physiologic response.
- 1. Cold Shock (0-2 min)
- 2. Functional Disability (2-15)
- 3. Hypothermia (>15-30)
- 4. Peri-Rescue Collapse
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Cold Shock Response
- cause: stimulation of truncal skin nerve endings. colder = stronger response
- reflex:
- 1. gasp
- 2. hyperventilation (results in 5)
- 3. hypertension
- 4. tachycardia (you get an andrenaline rush)
- 5. difficulty holding breath
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How to die from cold shock response.
- 1. drown from gasping underwater
- 2. faint from hyperventilation, then drown
- 3. tachycardia increasing cardiac work can result in cardiac arrest if you have heart problems
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Funtional Disability Physiology
- 1. difficulty swimming -- cold water more viscous, muscles cold
- 2. loss of manual dexterity because of numbing
- 3. muscle cramping
- 4. swimming increases rate of heat loss* - die faster
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Hypothermia Death
- cooling of central core temp in linear manner. really >30 min
- 1. go unconscious (drown)
- 2. cardiac arrest if you're out of water
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Hypothermia Physiology
- 1. peripheral vasoconstriction
- 2. brain (hypothal) sense cold = shiver
- 3. physical impairments
- 4. mental impairments (poor judgement)
- 5. cold-induced diuresis (more central blood volume(ANP))
- 3. core temp <35 deg C
- 4. every organ system effected ( like multiple trauma)
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Hypothermia Pathophysiology
- 1. dysrhythmia - really cold bradycardia, then cardiac arrest
- 2. hypotension
- 3. decreased metabolism
- 4. loss of shivering, muscles too cold...increased rate of cooling now
- 5. loss of consciousness
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Insulators and their effect on cooling rate.
- 1. air between clothing and skin
- 2. body fat
- - linear relationship between cooling rate and body fat. - heat lost proportional to surface area
- - amt of heat to lose proportional to weight
- -large fat people cool slower, adults slower than kids
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Classification of Hypothermia
- Mild - 32C-35C
- Moderate - 28-32
- --LOC, loss of shiver, dysrhythmmia
- Severe - <28
- --vital signs reduced or absent, cardiac arrest
- --may seem dead, but can't assume if hypothermic
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Don't Drownproof in cold water, HELP position
- because you immerse another 9% in cold water to remove more heat.
- HELP position: fetal position, reduce surface area for heat loss, protect some of the high heat loss areas (axilla, groin (not neck))
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Swim for shore?
- 1. it increases blood to arms, more heat loss
- 2. maybe, you need to consider a lot of factors
- -water temp, tide, distance, swimming ability, state of health, proximity of rescuers, signaling devices
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First Aid for Hypothermia
- 1. get them out
- 2. ABCs
- - may have really low pulse
- 3. be gentle - rough care cold cause cardiac arrest
- 4. remove clothing, protect from wind, vapor barrier
- 5. add heat if you have it
- 6. no eating and drinking - may cause aspiration
- 7. transport
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Pathophysiology of Drowning
- 1. aspiration of water
- 2. cough/ struggle to reach surface
- 3. laryngospasm
- 4. get hypoxemic
- -brain - LOC
- -muscles - laryngospasm stops, water gets in
- - heart - V. fib
- 5. reflex swallowing - lot of water in stomach, prone to vomiting
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Fresh vs Salt water
- Fresh - denature protein in alveoli, they collapse
- Salt - wash out surfactant, pulmonary edema and damage to alveolar-capillary membrane
V/Q mismatch in both, treatment the same!
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Drowing in Cold Water
- higher probability of resuscitation because:
- -ability of tissues to survive hypoxia is better in cold water
- -cooling of CNS, vital organs cools core temp.
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First Aid for drowning
- 1. ABCs
- 2. treat hypoxia - give 02
- 3. transport
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Take Home Messages from Studies
- 1. air is a good insulator of heat, water is a good conductor of heat. so get out of the water!
- 2. heat flow through head is not disproportionate, but cooling rate does accelerate due to increase surface area in contact with water
- 3. rough water is worse than calm water for hypothermia, more cold water contact, no warm water bubble
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