Hypothermia is defined as a core body temperature below 95°F. The body loses heat through conduction, evaporation, respiration, convection, and radiation. Patients with severe hypothermia below 90°F have decreased vital signs and lose the ability to shiver. They require gentle handling and slow rewarming in a medical facility using warmed IV fluids and oxygen. Mild hypothermia can often be treated in the field by removing wet clothes and adding insulation.

1. HYPOTHERMIAHYPOTHERMIA

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

3. ELOs
• Define Hypothermia.
• List the five mechanisms by which the body
loses heat.
• Describe why patients with hypothermia
should be handled gently

4. Bonus ELO
• Identify the four criteria which distinguish
mild hypothermia from severe hypothermia

5. HYPOTHERMIA
• Hypothermia is
defined as when the
body’s core
temperature falls to
95 degrees F or less.

6. Battle of Stalingrad
• Germany lost the
entire Sixth Army –
thousands lost to
combination of
starvation and
hypothermia

7. 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

8. Hypothermia- Causes
• Increased heat loss
• Decreased heat production

9. Heat Loss
• Conduction
• Evaporation
• Respiration
• Convection
• Radiation

10. 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

11. 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

12. Heat Loss
• Respiration
– 0F:
• 18 calories/hr warming
• 24 calories/hr
evaporation/moisturize
• 1000 cal/day
• Breathe through
mask/gaiter

13. Heat Loss
• Convection
– Try to retain dead air
– Chimney effect
– Wind chill
– Velcro Closures/Neck
Gaitor

14. Heat Loss
• Wind Chill
– 40 F
• 10 MPH: 28F
• 20 MPH: 18F
• 30MPH: 13F
– 20 F
• 10MPH: +4F
• 20 MPH: -9F
• 30 MPH: -18F

15. 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

16. Heat Production
• Heat Generation:
– Nonshivering
Thermogenesis:
• Increase in metabolism
• Food intake

17. Heat Production
• Non Shivering
Thermogenesis-
– Activity
• Isometrics
• Sleeping Bag Late
Night/Early Morning

18. Heat Production
• Shivering
Thermogenesis- can
increase metabolic rate
by a factor of 20
• Disadvantages-
– short lived
– Absent below 90F core
temp
– Blunted by alcohol

19. Military Risk Factors
• Starvation
• Dehydration
• Exhaustion
• Exposure
• Poor/Excessive
Clothing
• Sweating
• Trauma/Burns

21. 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

22. SIMPLIFY
• Distinguish
moderate/severe from
mild hypothermia

23. 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

24. 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

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

26. 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!

27. 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.

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

29. Treatment
• Rough Ride

30. Treatment
• Smooth Ride
(relatively)

31. 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

32. 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

33. Field Re-warming Don’ts
• No alcohol
• Nothing by
mouth with
severe
hypothermia
• Water bath
with extreme
caution

34. 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

35. Treatment
• Breathing
– Cut respiratory rate to 6 bpm secondary to
decreased metabolic demands

36. Treatment
• Circulation
– Chest compressions- be absolutely sure of your
findings

37. CPR
• NO ONE IS DEAD UNLESS…….

38. CPR
• …….THEY ARE WARM AND DEAD….

39. 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

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

41. ACLS
• Red Herrings
– Shivering = Ventricular Fibrillation
– Cold skin = Asystole

42. 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 ……

43. 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

44. 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)

45. 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.

46. 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.

47. 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

48. A Paradox of Sorts
• Paradoxical Undressing
• Skin temperature is the critical factor to the
physiological and behavioral responses

49. QUESTIONS?????