hypothermia

HYPOTHERMIAHYPOTHERMIA

TLO

• Given a simulated casualty, treat hypothermia in accordance with the references.

ELOs

• Define Hypothermia.• List the five mechanisms by which the body

loses heat.• Describe why patients with hypothermia

should be handled gently

Bonus ELO

• Identify the four criteria which distinguish mild hypothermia from severe hypothermia

HYPOTHERMIA

• Hypothermia is defined as when the body’s core temperature falls to

95 degrees F or less.

Battle of Stalingrad

• Germany lost the entire Sixth Army – thousands lost to combination of starvation and hypothermia

Fino-Russian War

• Russian to Finnish casualty rate – 10 to 1

• Russians poorly equipped – expected to take down Fins in less than 2 months

• Thousands dead from hypothermia and starvation

Hypothermia- Causes

• Increased heat loss• Decreased heat production

Heat Loss

• Conduction• Evaporation• Respiration• Convection• Radiation

Heat Loss

• Conduction– Search for poor conductors– Air– Foam– Fibrous Material (Wood,

Cork)– Use IsoMat for insulation –

for casualties– Allowing maximum loft on

sleeping bags– Thickness equals warmth

Heat Loss

• Evaporation– Enormous amount of heat

lost– Much energy spent

transforming liquid to gas– Insensible sweat- cold air

dry- skin must remain moist– “Comfortably cool”

minimize sweating– Mountain Pace– Vapor Barrier

Heat Loss

• Respiration– 0F:

• 18 calories/hr warming• 24 calories/hr

evaporation/moisturize• 1000 cal/day• Breathe through

mask/gaiter

Heat Loss

• Convection– Try to retain dead air– Chimney effect– Wind chill– Velcro Closures/Neck

Gaitor

Heat Loss

• Wind Chill– 40 F

• 10 MPH: 28F• 20 MPH: 18F• 30MPH: 13F

– 20 F• 10MPH: +4F• 20 MPH: -9F• 30 MPH: -18F

Heat Loss

• Radiation– Infrared energy lost– Radiant energy will

heat up clothing– Thick enough

insulating layer or opaque layers to retain heat

– Lightly colored clothing reflects more radiation back to body

Heat Production

• Heat Generation:– Nonshivering

Thermogenesis:• Increase in metabolism• Food intake

Heat Production

• Non Shivering Thermogenesis-– Activity

• Isometrics• Sleeping Bag Late

Night/Early Morning

Heat Production

• Shivering Thermogenesis- can increase metabolic rate by a factor of 20

• Disadvantages- – short lived– Absent below 90F core

temp– Blunted by alcohol

Military Risk Factors

• Starvation• Dehydration• Exhaustion• Exposure• Poor/Excessive

Clothing• Sweating• Trauma/Burns

Hypothermia: Diagnosis- Measurement

• Rectal or Esophageal Monitoring are the most accurate

• May not be able to expose the casualty to the elements

• Field Method- ungloved hand on skin of trunk and observe signs and symptoms

SIMPLIFY

• Distinguish moderate/severe from mild hypothermia

Mild Hypothermia

• Shivering present• Mental Impairment

– Complex tasks– Simple tasks

• Physical Impairment– Fine Motor Movements– Gross Motor Movements

• Will resolve with minimal intervention with field re-warming techniques

Severe Hypothermia

• Any one of the following conditions will constitute life threatening hypothermia:

• Core temperature less than 90 degrees F• Decrease in vital signs- heart rate,

respiratory rate• Loss of consciousness or severely altered

level of consciousness• Cessation of shivering

Mild Hypothermia

- Hypothermia which fails to meet any of the criteria of life threatening hypothermia

Severe Hypothermia

• Requires an extraordinary amount of heat in order to resuscitate a casualty with severe hypothermia

• Institute field re-warming techniques in order to preserve existing heat

• CASEVAC Immediately to a facility which can resuscitate the casualty!

Treatment

A COLD HEART IS AN IRRITABLE HEART

• If a casualty is determined to have severe hypothermia then handle them very gently as they are prone to fatal arrhythmias.

Treatment

• Take your time to properly move a casualty who may have life threatening hypothermia

Treatment

• Rough Ride

Treatment

• Smooth Ride (relatively)

Field Rewarming Techniques

• Remove wet clothing• Insulation/Vapor Barrier (1.5 C/hr, 2.7 F/hr)• Insulated Hot Water Bottles to Axilla/Groin• Person to person rewarming• Effective with mild hypothermia• Not effective with severe hypothermia –

only serves to maintain warmth not to re-warm

Severe Hypothermia – Hospital Rewarming Techniques

• Warmed IVF (1 L= 0.33 degrees C/hr, 0.6 F/hr)- Avoid Lactated Ringers

• Warmed Inspired, Humidified Oxygen• Lavages (3 degrees C/hr, 5.4 F/hr)• Extracorporal Blood Rewarming• Bair Hugger

Field Re-warming Don’ts

• No alcohol• Nothing by

mouth with severe hypothermia

• Water bath with extreme caution

BLS Treatment

• ABCD’s ( Degrees) – monitor for at least 60 seconds

• Difficult to monitor vital signs because of decreased respiratory rate, decreased heart rate, and vasoconstriction

Treatment

• Breathing– Cut respiratory rate to 6 bpm secondary to

decreased metabolic demands

Treatment

• Circulation– Chest compressions- be absolutely sure of your

findings

CPR

• NO ONE IS DEAD UNLESS…….

CPR

• …….THEY ARE WARM AND DEAD….

CPR

• UNLESS THEY ARE DEAD!• Do not initiate CPR if: - Core temperature is less than 50 degrees

- Patient is obviously frozen- eg ice formation in the airway - Chest wall is so stiff that it is incompressable

ACLS

• Active core rewarming techniques are the primary therapeutic modality in hypothermic victims in cardiac arrest.

ACLS

• Red Herrings– Shivering = Ventricular Fibrillation– Cold skin = Asystole

ACLS

• Ventricular Fibrillation • Attempt three progressive unsynchronized

shocks at 200, 300, 360Js. If no response then continue CPR and REWARM VICTIM. Reattempt counter shocks when core temp rises above 86 degrees F.

• Attempt successive counter shocks at 86, 88, 90 degrees F ……

ACLS

• ACLS drug protocols- be wary of the medications being sequestered due to poor metabolism, once casualty is rewarmed may be toxic

• Employ ACLS drug protocols above 92 degrees F – at longer intervals

Future Rewarming Techniques

• High temperature IV fluids ( 2-3C/hr)• Low frequency microwave radiation – 90-

100 watts ( 1C/ 6-7 minutes)• ThermoStat ( 13 C/hr)

Afterdrop

• Continued decrease of core temperature after patient has been removed from the cold and rewarming has begun.– Extremity rewarming releases peripheral

vasoconstriction.– Process of warmer core equilibrating with

colder peripheral tissues.– Greatest drop seen with acute hypothermia.

Considerations with Frostbite

• If treating hypothermia with frostbite, DO NOT begin RX for frostbite until core temperature is above 93°F otherwise at risk for afterdrop

• Remember your first priority is to re-warm the body core.

Considerations with Trauma

• Treat possible sites of blood loss (especially in the extremities) prior to rewarming

• Hypothermia and cold may help control hemorrhage

• Be careful of hypovolemia once patient has been re-warmed – keep patient supine and replenish fluids

A Paradox of Sorts

• Paradoxical Undressing• Skin temperature is the critical factor to the

physiological and behavioral responses

QUESTIONS?????