Erika Ball, RN, BSN
* Objectives:
* Understand the
physiology of
hypothermia
* EMS considerations for
the hypothermic
patient
* Mechanisms of heat
loss
Bledsoe, 2013.
* Clinical indications of
hypothermia
* Degrees of
hypothermia
* Treatment and
rewarming
* Other considerations in
hypothermia
* Temperature regulation:
* Happens in the hypothalamus
* The hypothalamus is the body’s
“thermostat”
* The body has thermo sensors in the skin
the mucosa, and in certain deeper
structures in the body
* The hypothalamus works as a regulator for
shivering and sweating, depending on the
environmental stimulus (excessive cold or
heat).
Bledsoe, 2013.
*There are two rates the temperature
regulation system effects:
*Basal Rate- the normal resting rate
for the CORE of the body (deep
internal temperature)
*Metabolic Rate- reactive
adjustment to the environment to
maintain a continual core
temperature
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*Normal body temperature is 98.6
o
o
F or 37 C
*Hypothermia definition:
*Decrease (unintentionally) in CORE
temperature greater than 3.5 degrees
from the basal temperature
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*
*Conduction
*Convection
*Radiation
*Evaporation
*Respiration
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*Conduction:
*Direct contact with a cooler object
*Heat loss happens in the direction of the
high temperature to the low
temperature
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*Convection:
*Air temperature causes heat loss
*Radiation:
* Infrared rays cause heat loss
* Infrared heat loss is always happening until
temperatures reach molecular standstill (called
absolute zero)
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*Evaporation:
* Water evaporation causes heat loss
* This phenomenon can happen from the skin or
water evaporating in the air as we breathe
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*Respiration:
* A combination of convection, radiation, and
evaporation occurs during the respiratory
process, causing further heat loss
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*
* Body composition
* Thermoregulatory response (shivering ability/ heat
production)
* Clothing/insulation
* Water or air temp and conditions
* Medications or intoxication
* Age
* Health
* Extended exposure
* Associated Injury
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* Mechanisms for heat conservation:
* Vasoconstriction of peripheral blood vessels
* Skin becomes pale and cool
* Goose bumps (unknown why this truly happens,
some speculate this is an evolutionary remnant*)
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* Hypothermia results from:
*Insufficient heating mechanisms
*Severe cold stress (exertion with cold
exposure)
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* Degrees of hypothermia:
* MILD: 95- 89.6 F
* Thermoregulatory mechanisms are still operating
fully
* MODERATE: 89.6- 82.4 F
* Effectiveness of thermoregulatory mechanisms
diminish until they fail
* SEVERE: Lower than 82.4 F
* Loss of consciousness
* No more shivering
* pH balance disrupted
* Susceptible to V Fib or asystole
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*
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*
1.Short-term
(Cold shock response)
2. Midterm
(Loss of performance)
3. Long-term
(development of hypothermia)
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*
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*
* Generally in water
* First 3-4 minutes of immersion (with head out of
the water)
* Peripheral vasoconstriction
* Panic
* Gasp reflex
* Hyperventilation
* Tachypnea
* Vagal cardiac arrest and subsequent drowning
(Polar bear plunge!!)
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* IF they survive the cold-shock, this is the next 30
minutes of progression
*
Neuromuscular activity and loss of motor control
* If the neuromuscular mechanisms fail, individual
can not execute survival procedures (grabbing life
preserver) and individual will drown
*
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* Development of hypothermia process
* Mild
* Moderate
* Severe
*
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* Shivering
* Lethargy
* Lack of coordination
* Pale cool skin
* Early stages witness rise in BP, heart rate, and
respiration
*
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* Shivering ceases
* Arrhythmias can occur
* Cardiac arrest
* Voluntary muscle control loss
* Hypotension
* Pulse and respirations become undetectable
*
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* Initial treatment:
* Remove any wet clothing
* Stop cooling process with blankets and elements
* Keep patient in supine to prevent further
hypotension
* Handle patient gently (skin is fragile)
* Establish cardiac rhythm
*
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* PR interval can become longer (1st degree
heart block)
* This progresses to a prolonged QRS and QT
* “J” waves, or Osborne waves, can occur under
a core temperature of 90 F
O
*
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* J waves are most frequent in leads II and V6
* These waves become larger in size as the patient’s
core temperature decreases
*
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*
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* Active rewarming:
* Mild hypothermia- external methods
* Blankets
* Heat packs (in axilla and groin)
* Mild Hypothermia- internal rewarming
* Warm IV fluids
* If the patient is still shivering, rewarming should
occur quickly
*
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* External:
* Warm blankets
* Heat packs (again, groin and axilla)
* Internal
* Warmed IV Fluid
* Warm, humidified oxygen
* Best done in the ER, where protocol exists for
slowly rewarming the patient
*
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* EMS should use caution in rewarming the
patient due to peripheral reflex dilation
* Patient’s rewarming sometimes causes a
hypotension and can precipitate V Fib
* This is why warm packs in the groin and axilla
warm the core rather than the extremities
*
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*
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Please Review!
* DO NOT give any drugs to these patients!
* Assess the pulse for a full 30-45 seconds
* May attempt defibrillation x1
*
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*
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*
* Morphine
* Binds with opioid receptors to produce narcotic
analgesia
* CNS depressant
* Causes peripheral vasodilation
* May be given in 5 mg increments for severe pain
(blood pressure permitting) for a dose of 5-10 mg
in hypothermia, at the discretion of the ECRN/
MD.
* Contraindications:
* Respiratory depression, shock, hypotension, known
sensitivity or allergy. Use with caution in bronchial
asthma, respiratory insufficiency, head trauma
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* Thank you for your time and attention!
* The 2014 CE calendar will be available early in
December!
* We welcome your suggestions!
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References
Bledsoe, B. 2013Prehospital management in the 21st
century.
Giesbrecht, G., 2013. Prehospital treatment of
hypothermia. Expedition Medicine.
Region VII Emergency Medical Service Systems
Standing Medical Orders, 2011
Bledsoe, 2013.