Temperature-Related Emergencies

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Temperature-Related Emergencies

• David A. Caro, MD

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Temperature-Related Emergencies

• Introduction
• Temperature Control/Physiology
• Mechanisms of Heat Dissipation
• Temperature Measurement

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Temperature-Related Emergencies

• Heat Illnesses
• Heat stress
• Heat exhaustion
• Heat stroke

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Temperature-Related Emergencies

• Cold Illnesses
• Frostbite
• Hypothermia

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IntroductionHeat Control Physiology

• Normal human temperature 96.8 to 100.4oF (36
  -37.8oC)
• Temperature can reach 104oF during strenuous
  exercise
• Preoptic Hypothalamus responsible for
  temperature control via thermoregulation

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Temperature Emergencies

• A rise in core temperature above the normal range
  (hyperthermia) or a decrease below the normal
  range (hypothermia) is the consequence of an
  imbalance between heat production and heat loss.

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Heat Production
Ambient Heat
Temperature
Heat Loss to environment
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Skin Receptors
Hypothalamus
Core Receptors
Thermoregulation
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Thermoregulation
Veins
Hypothalamus
Sweat Glands
Behavior
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Hot
Cold
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Introduction Heat
Dissipation Mechanisms

• Radiation - electromagnetic dissipation - 65
• Evaporation - transfer of heat to make liquid a
  gas - 25
• Convection - heat transferred to air and water in
  close proximity to skin - 8
• Conduction - direct heat transfer - 2

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Radiation
AIR
EM Radiation
The body at the higher temperature emits more
energy than the one at the lower temperature, and
the net transfer of energy (heat) is down the
temperature gradient.
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Convection
AIR MOVEMENT
SKIN
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Evaporation

• . For every ml of water evaporated from the
  surface of the skin, 0.58 Kcal are removed from
  the body.
• Insensible - skin, respiratory
• approximately 600 ml/day
• Sensible - sweat
• up to 3 liters/hr

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Temperature Measurement

• Axillary - most inaccurate
• TM - wide variability
• Oral - affected by ventilation
• Rectal
• Bladder, Esophageal, PA catheter - in ICU setting

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Heat Illnesses

• Heat Stress
• Heat Exhaustion
• Heat Stroke

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Heat Illness

• Heat Stress
• Heat Cramps
• Heat Tetany
• Heat Edema
• Heat Syncope
• Prickly Heat

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Heat Exhaustion

• Syndrome of weakness, fatigue, headache, nausea,
  vomiting, vertigo, orthostasis, and impaired
  judgement
• NO major CNS symptoms (seizures, coma)

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Heat Stroke

• Thermoregulatory Failure
• Profound CNS dysfunction
• Classic vs. exertional

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Heat Stroke

• CNS dysfunction
• CV dysfunction
• Hepatic dysfunction
• Renal failure
• Hematologic complications

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Heat stroke - Differential diagnosis

• meningitis
• encephalitis
• status seizures
• falciparum malaria
• thyroid storm
• medications

• DTs
• typhoid fever
• hypothalamic hemorrhage

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Heat stroke treatment

• ABCs
• Cooling
• remove from heat remove clothing
• spray water/fan
• ice packs/cooling blankets
• lavage (NG, bladder, thoracic)
• Dialysis/CP bypass

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Heat stroke treatment

• Benzos for seizures, shivering
• IV fluids
• replace deficits
• treat rhabdomyolysis
• Treat coagulopathy

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Cold Illnesses

• Hypothermia
• Frostbite

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Hypothermia

• 92-95oF - Mild
• 87-92oF - Moderate
• lt 87 oF - Severe

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Frostbite

• Spectrum - similar to burns
• Mild (analagous to 1o burn)
• Moderate (2o burn)
• Severe (3o burn to gangrene)

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Treatment - Mild Hypothermia

• Remove wet clothing replace with dry
  clothing/blankets
• Ambient warming
• Warmed oral fluids

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Treatment - Moderate Hypothermia

• Remove wet clothing replace with dry
• Monitor cardiac, respiratory status
• Radiant/heat blanket warming
• Warmed IV, oral fluids
• Warmed, humidified oxygen
• Warmed IV bags to groin, axillae ? immerse

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Treatment - Severe Hypothermia

• All of the above
• Careful movement may induce V Fib
• Intubate as needed
• Warmed NG, Foley lavage
• Warmed pleural/peritoneal lavage
• Dialysis, Bypass