Hypothermia and Cold Weather Injuries

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HypothermiaandCold Weather Injuries

• Recognizing, Preventing and Treating

Shawn F. Kane, M.D. Kevin deWeber, MD, FAAFP
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Outline

• History
• Cold Injury v Heat Injury
• Definitions
• Physiology/Effects on Organ Systems
• Non-Freezing and Freezing cold injuries
• Treatment
• Field Management

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Historical Perspective

• French invasion of Russia in 1812. Baron de
  Larrey, chief surgeon, noted mental and physical
  hardships by Soldiers exposed to the cold
• Freeze-thaw-refreeze phenomenon.
• George Washington 10 of his troops perished in
  the winter of 1777-78 due to cold.

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Historical Perspective

• WWII 200,000 Allied and German troops suffer cold
  related injuries or deaths
• Korea 10 of all US fatalities were cold related.
• 1950 Battle of Chosin Reservoir. 30K UN troops
  held off and repelled 60K Chinese
• UN 2.5K KIA, 5K WIA, 7.5K Frostbite/cold
  weather injuries
• Chinese 25K KIA, 12.5K WIA, 30K Frostbite/cold
  weather injuries

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Cold Injury v Heat Injury

• Heat Injuries CDC 1999-2003. 3,442 deaths due
  to heat. Mean 688/yr
• Cold Injuries CDC 1999-2002. 4,407 deaths due
  to cold. Mean 689/yr
• 60/40 - underlying cause/contributing factor

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Definitions

• Accidental Hypothermia the unintentional drop
  in core body temperature to lt35C (95F)
• Intentional Hypothermia
• controlled cooling of core
• body temperature for
• specific medical
• indications (CVA, MI, TBI)

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DefinitionsTypes of Heat Loss

• Radiation dispersal of heat energy from
  uncovered skin to nearby objects
• gt50 of our heat loss
• Evaporation loss of heat via the transformation
  of liquid water into water vapor.
• 20-30 of heat loss
• Insensible heat loss can lead to dehydration if
  not accounted for.

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DefinitionsTypes of Heat Loss

• Conduction transfer of heat from one object to
  another through physical contact
• Conductivity of water is 23X that of air!!
• Immersion injury reduces body temp more rapidly
  than convective loss
• Convection loss of heat to the air moving next
  to the body
• Windy days
• Cycling, running

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Hypothermia Stages/Classifications

• Hypothermia of TRAUMA

• ACCIDENTAL

• MILD 32C 35C
• 90F - 95F
• MODERATE 28C 32C
• 82F 90F
• SEVERE lt28C
• lt82F
• 33-35(91-95), 31-32(88-90)
• lt31(lt88)

• MILD 34C 36C
• 93F - 97F
• MODERATE 32C 34C
• 90F - 93F
• SEVERE lt32C
• lt90F

Shivering
Reduced shivering
NO shivering
Jurkovich GJ. Surg Clin N AM 87(2007) 247-267
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Human Physiology

• Range of 34-40.5C(95-105F) to retain normal
  organ function
• Thermoregulatory drive is so important that it
  takes precedence over many other homeostatic
  functions
• Human body can compensate for hyperthermia better
  than hypothermia

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Heat Loss
Heat Gain
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Physiology/Effects on Organ Systems

• Initial effects mimic those of sympathetic
  stimulation
• Tremor
• Vasoconstriction
• Increased O2 consumption
• Increased Heart Rate
• Increased Minute Ventilation
• Continued cold exposure results in inability to
  compensate

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Physiology/Effects on Organ Systems

• Cardiovascular
• Initial tachycardia progresses to bradycardia
  starting at 34C
• CO initially increased despite a drop in BP
• 50 decrease in HR
• lt30C atrial fibrillation, bradycardia and
  ventricular dysrhythmias
• lt25C asystole
• At temperature lt30C decreased effects of
• cardiac medications

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Physiology/Effects on Organ Systems

• Cardiovascular
• Conduction system is VERY sensitive to decrease
  temperatures.
• PR interval, QRS and QT interval prolong as
  temperature decreases or stays below normal
• J or Osborn wave in 80 of hypothermic patients
• Bretylium is the only CV drug that works at
  decreased temperatures

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Osborn or J wave
Colder the temperature the larger the J wave
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Physiology/Effects on Organ Systems

• Respiratory
• Initially increased but becomes depressed at
  temperature lt33C
• Increased mucous production (bronchorrhea)
• Left shift in oxyhemoglobin curve impairing
  oxygen delivery

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Physiology/Effects on Organ Systems

• GI
• Ileus, bowel wall edema, shallow gastric ulcers
  (Wischnevskys Ulcers)
• Decrease hepatic function drug metabolism
• Hemorrhagic pancreatitis, elevated amylase
• RENAL
• Initial vasoconstriction contributes to diuresis
• Later loss of distal tubular water reabsorption
  due to dec ADH sensitivity and inc electrolyte
  excretion

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Physiology/Effects on Organ Systems

• HEME
• Cold platelets DO NOT work
• 34C 40 decrease in coagulation enzyme
  function
• Hemoconcentration
• 1C drop in temp ? 2 increase in hematocrit
• Normal hematocrit in moderate to severe
  hypothermia need to be concerned about blood
  loss.
• Decreased WBC function, increased infection
• risk

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Physiology/Effects on Organ Systems

• NEUROLOGICAL
• Decreased neural transmission
• Incoordination and cognition, numbness
• DTRs decrease and eventually flaccid paralysis
• lt32C amnesia
• 31C-27C lose consciousness
• paradoxical undressing

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Hypothermia

• Standard clinical thermometers and a false sense
  of security
• Only go down to 34C(94F) need low-reading
  rectal thermometers (lt32/90C/F)
• Best accuracy thermometer in place for 3 minutes
  at a depth of 10 cm
• Treat the patient clinically not the
  classification of hypothermia

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NOT DEAD UNTIL THEY ARE WARM AND DEAD(unless
they are really dead)
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Hypothermia Treatment

• RECOGNIZE THE CONDITION!
• Removal from nasty conditions
• Removal of wet clothing
• Handle with care (testy heart)
• Insulate and warm up

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Rewarming Methods

• External
• blankets
• hot water bottle
• heater
• another body
• Immersion
• Internal
• Warm IV fluids
• Warmed air

• Exercise is BAD
• Depletes glycogen, reduces shivering
• Increases heat loss

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Hypothermia in Sport

• High risk sports
• Water sports
• Running, cycling
• Alpine cold weather sports

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Mild Hypothermia in Sports91-95 F

• Remove from cold
• Insulate
• Warm, sweet drink
• No alcohol
• Minimal to mild activity if improving

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Moderate Hypothermia88-90 F

• Passive rewarming
• In field, no active rewarming until rectalT gt93F
• Monitor rectal temp
• Transport to ER for observation

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Severe Hypothermialt88 T

• Handle with care!
• Gentle passive rewarming only
• Transport immediately, ER?ICU

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Non-Freezing Cold Injuries(NFCI)

• A clinical syndrome defined as
• Injury to soft tissues of the extremities that
  result from prolonged cooling and/or constant
  exposure to wet/damp conditions.
• Peripheral nerves (then muscle) are most
  susceptible to cold related injuries.
• Sequelae to NFCI may arise immediately after the
  incident or may not demonstrate themselves for up
  to 18 months post exposure

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Non-Freezing Cold Injuries

• Wet

• Dry

• Trenchfoot
• Prolonged exposure to temps
• between 0-32C(32-60F) for hours
• to 3-4 days
• Swollen, edematous, numb foot
• Initially red then becomes pale and cyanotic
• Increased sensitivity to pain and infections

• Chilblains or Pernio
• Exposure to temps lt32C(60F)
• Bare skin exposed to dry environment
• Erythematous, tender, swollen, itchy and painful
  papules
• After rewarming inflamed, red and hot to the
  touch for hours

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Non-Freezing Cold Injuries

• Wet

• Dry

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Non-Freezing Cold Injuries(NFCI)

• Transient Sequelae
• Hyperhidrosis
• Hyperesthesia/Anesthesia of digits
• Dec ROM and joint swelling
• Edema
• Fat pad loss, transient muscle atrophy
• Pain from injury to peripheral nerves or small
  vessels as a result of ischemia

• Late Sequelae
• Hyperesthesia of distal digits
• Increased sensitivity to heat and cold
• Nail bed deformities
• Hyperhidrosis, hypohidrosis or anhidrosis
• Decreased proprioception
• Pain
• Loss of fibrocartilage in ear
• AVN, growth plate injuries

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Freezing Cold Injuries (FCI)

• A clinical syndrome of temporary or permanent
  tissue damage that results from the formation of
  extra/intracellular crystals due to prolonged
  exposure to sub-freezing temperatures
• Extent of damage can be superficial (frostnip) to
  full thickness (bones and muscles)
• Grade 1 through 4
• FCI composed of two parts immediate and
  reperfusion

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Freezing Cold Injuries (FCI)

• Reperfusion Injury

• Initial Freeze Injury

• RBC, WBC and platelet aggregation leads to patchy
  thrombosis in microcirculation
• Oxygen free radicals, prostaglandins and
  thromboxane worsen vasoconstriction and
  thrombosis
• MAJORITY of damage occurs during REWARMING

• Hyperosmolarity disrupts cell function
• Rapid freezing leads to intracellular crystals
  and immediate cell death
• Loss of pain sensation

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Freezing Cold Injuries (FCI)

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Cold Weather Injury Treatment

• Low index of suspicion in an athlete who
  complains of being cold during or after exercise
  with a change in sensorium.
• ABCs
• FIRST priority is to prevent further HEAT LOSS!
  (shelter from wet, cold, windy environments, dry
  off)

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Cold Weather Injury Treatment

• DO NOT thaw tissue if there is a risk of
  re-freezing
• DO NOT RUB the affected area
• Minimize motion, move horizontally to minimize
  cardiac irritability
• Safety of rescuers

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Rewarming

• PASSIVE involves the use of blankets to cover
  body and head to trap heat being lost.
• ACTIVE the application of outside heat to raise
  body temperature
• External heat blanket/forced hot air system
• Internal introduction of warm fluids into the
  body
• Warm IVF, body cavity lavage, extracorporeal

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NFCI and FCI TREATMENT

• RAPID rewarming is the goal. TrunkgtLimbs
• Immersion of limb in 40-42C (102-106F) water
  bath
• 30-45 minutes area appears flushed with good
  circulation when circulation is re-established
• Tetanus Toxoid
• Benzyl penicillin 600mg q6 for 48-72 hours
• Narcotic Pain Relief
• very painful!!!

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HFCI and FCI TREATMENT

• Dry skin to prevent maceration.
• Prevent further injury (prostaglandins)
• Serous blisters unroof topical aloe vera
• NSAIDS
• Prevent Thrombosis
• tPA a few studies demonstrate the benefit of
  tPA in preventing/minimizing amputations or the
  amount of amputated tissue

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TREATMENT
Amputation should be delayed 2-3 months
MRI/MRA Technetium 99m methylene diphosphonate
bone scan (triple phase 1 minute, 2 hours and
7 hours) as early as 48 hours after admission
may help identify viable (hibernating) tissue
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NFCI and FCI Sequelae

• Late Sequelae
• Hyperesthesia of distal digits
• Increased sensitivity to heat and cold
• Nail bed deformities
• Hyperhidrosis, hypohidrosis or anhidrosis
• Decreased proprioception
• Pain
• Loss of fibrocartilage in ear
• AVN, growth plate injuries

• Transient Sequelae
• Hyperhidrosis
• Hyperesthesia/Anesthesia of digits
• Dec ROM and joint swelling
• Edema
• Fat pad loss, transient muscle atrophy
• Pain from injury to peripheral nerves or small
  vessels as a result of ischemia

AMPUTATION IS THE ULTIMATE LONG-TERM SEQUELAE TO
A FCI
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How much do you amputate?
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FIELD PASSIVE REWARMING EQPT
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FIELD ACTIVE REWARMING EQPT
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Prevention of Cold Injuries

• Layered clothing
• Cotton BAD
• Wetsuits in water sports
• Adequate nutrition hydration
• Cancel events if too cold
• ACSM dry bulb lt-4F at coldest place

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Review

• Moderate hypothermia 91-95F
• Avoid active rewarming if lt93F in field
• Dry NFCI chilblains, pernio
• Wet NFCI trenchfoot
• Frostbite drain SEROUS blisters give Pcn,
  NSAID, Tetanus toxoid, pain meds
• Cancel events if low Temp lt-4F

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Questions