Erika Ball, RN, BSN

*Objectives:

*Understand the physiology of hypothermia

*EMS considerations for the hypothermic patient

*Mechanisms of heat loss

*Clinical indications of hypothermia

*Degrees of hypothermia

*Treatment and rewarming

*Other considerations in hypothermia

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*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).

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*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 98.6o

F or 37o

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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*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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1.Short-term

(Cold shock response)

2. Midterm

(Loss of performance)

3. Long-term

(development of hypothermia)

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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 90OF

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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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*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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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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*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

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