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Thermoregulation

  1. Normally, body temperature is maintained within a very narrow range by an integrated thermoregulatory system that is centered in the _____________.
    hypothalamus
  2. What is poikilothermia?
    A state wherein body temperature tends to equilibrate with ambient temperature.
  3. When no measures are taken to maintain body temperature, this % of patients in the OR will be hypothermic
    >50%
  4. True or false: hypothermia is associated with morbid outcomes
    True
  5. What are the three general components of the thermoregulatory system?
    • afferent input 
    • central processing
    • efferent responses
  6. Where are thermoreceptors found?
    hypothalamus, other parts of the brain and spinal cord, deep visceral tissues, skin surface
  7. The thermoreceptors from this location contribute 80% of the information to the central thermoregulatory system:
    core and deep body tissues

    20% comes from the skin surface
  8. This mechanism of thermogenesis is not thought to occur in adult humans, but contributes significantly to heat production in neonates.
    Nonshivering thermogenesis
  9. When behavioral thermoregulation is inadequate and temperature EXCEEDS the set point, these two mechanisms come into play:
    vasodilatation and sweating
  10. This mechanism is triggered to conserve heat when temperature is below the set point (when behavioral thermoregulation is inadequate)
    vasoconstriction
  11. Does shivering produce, release, or conserve heat?
    Produce
  12. Basal metabolic energy appears as heat at the rate of:
    1kcal/kg/hr
  13. If all of the BMR heat were retained, the body temp would increase at this rate:
    1°C/hr
  14. These organs are major heat generators:
    liver, heart, skeletal muscle
  15. Heat dissipation occurs through these:
    skin and respiratory mucosal surfaces
  16. T/F: Muscle tension (tone) alone, in the absence of shivering, generates heat.
    True
  17. How do α1-adrenergic receptors contribute to thermoregulation?
    vasoconstriction →conserves heat
  18. How do α1-antagonists contribute to thermoregulation?
    block vasoconstriction (prevent heat conservation)
  19. T/F: α1-antagonists have an effect on shivering or metabolic heat production in response to cold.
    False
  20. What are the four mechanisms of heat loss?
    convection, conduction, evaporation, and radiation
  21. Describe convection:
    • occurs by moving air
    • 15% of heat loss
    • proportional to the square root of the air velocity
  22. This type of heat loss occurs by direct contact with a cooler material (cold mattress, IV solutions)
    conductive
  23. T/F: A large percent of heat is lost through conduction.
    False. 3%
  24. T/F: Evaporation is facilitated by humid atmospheres.
    False! it is hindered with increasing humidity
  25. How many mL of H2O are lost from the skin/lungs to evaporation each hour at room temperature?
    30mL
  26. 2/3 of evaporation is from the...
    skin
  27. 1/3 of evaporation is from the...
    lungs
  28. What is the major mechanism of heat loss?
    Radiation
  29. What is radiation?
    infrared electromagnetic waves travel from a warmer object to a cooler one
  30. T/F: Radiant heat loss increases with the amount of exposed surface.
    True. Also increases with the temperature differential.
  31. What makes up the thermal "core compartment?"
    chest, abdomen, pelvis, head
  32. What is the least accurate site of core-temp monitoring?
    skin
  33. Where are the most accurate sites for core-temp monitoring?
    • Pulmonary artery
    • Tympanic membrane
    • Esophagus
    • Nasopharynx
    • Oropharynx
  34. T/F: Temperatures in the rectum and bladder are quick in reflecting temperature changes.
    No. They are slow.
  35. T/F: Body temperature is constant throughout the day.
    False. 1°C Δ depending on time of day, also monthly variation in menstruating women
  36. Normal core temperature range?
    36.5-37.5
  37. Which component(s) of the thermoregulatory system are altered by general anesthetics?
    a)afferent pathway
    b)central control mechanism
    c)efferent responses
    all of them
  38. Which component(s) of the thermoregulatory system are altered by regional anesthetics?a)afferent pathway
    b)central control mechanism
    c)efferent responses
    a&c (afferent and efferent)
  39. What is the most effective drug to treat shivering?
    Meperidine (pethidine)
  40. In the first 30-60 minutes following general anesthesia, the body temperature decreases by this amount:
    • 1°C
    • heat flows from core to peripheral compartment because of vasodilation
  41. Core temperature continues to decrease for ____ hours of general anesthesia. (Then it plateaus–due to vasoconstriction)
    2-3
  42. Regional anesthesia is associated with less severe hypothermia than general anesthesia since the central thermoregulatory activity is not impaired in regional anesthesia.
    False. The same magnitude of hypothermia occurs. 

    In regional anesthesia, the efferent response are blocked, and vasoconstriction and shivering cannot occur below the level of the block (so heat loss continues, so NO PLATEAU PHASE).
  43. Name two protective effects of hypothermia:
    • brain protection
    • spinal cord protection
  44. T/F: There are more protective benefits of hypothermia than consequences.
    FALSE
Author
sjkckd
ID
212183
Card Set
Thermoregulation
Description
thermoregulation cards
Updated

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