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Endocrine - Troutmanm > Temperature Regulation > Flashcards

Temperature Regulation Flashcards

1
Q

Humans are….

A

homeothermic

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2
Q

What does homeothermic mean?

A

means we actively maintain our body temperature in a tight range usually 36.5-37.3

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3
Q

What happens when our core body temp is outside a set range?

A

the body activates mechanisms to bring it back to normal

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4
Q

T/F: Anesthesia disrupts temperature regulation mechanisms

A

True

Hypothermia and Hyperthermia have adverse consequences to our patients

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5
Q

Types of temp monitoring devices (8)

A 
Skin
Axilla
Rectum
Esophagus
Nasopharynx
External auditory meatus
Bladder catheter
PAC
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6
Q

How is the skin temp in relation to core temp?

A

may be 3-4°C lower than core body temperature

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7
Q

How is the axilla temp in relation to core temp?

A

usually 1°C lower than core body temperature

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8
Q

what other advantage does the esophageal temp probe have?

A

probe doubles as esophageal stethoscope

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9
Q

What does the nasopharynx temp reflect?

A

reflects brain temp

risk of epistaxis

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10
Q

What does the external auditory meatus temp reflect?

A

reflects brain temp

risk of TM rupture

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11
Q

Normothermia -
Hypothermia -
Hyperthermia -

A

Normothermia - core body temp 37.0°C +/- 1°

Hypothermia - core body temperature < 36°C

Hyperthermia - rise in core body temperature >38˚C

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12
Q

What is ambient temperature?

A

temperature of the surroundings

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13
Q

*** What mediates temperature regulation?

A

The ANTERIOR hypothalamus/preoptic nuclei mediates temperature regulation

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14
Q

*** What does the term “set point” mean?

A

Body attempts to maintain a certain temperature

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15
Q

What happens in the body when the temp drops below normal?

A

The nervous system signals dermal blood vessels to constrict and sweat glands to remain inactive (this conserves body heat)

If body temp continues to drop, nervous system signals muscles to contract involuntarily (muscle activity generates body heat)

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16
Q

What happens when the body temp rises above normal?

A

Nervous system signals dermal blood vessels to dilate and sweat glands to secrete –> body heat is lost to its surroundings

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17
Q

Hypothermia effects are extensive and worsen with

A

degree of hypothermia

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18
Q

*** Hypothermia consequences:

Vascular

A

vasoconstriction
hypoperfusion of tissues
pulse oximetry difficult

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19
Q

*** Hypothermia consequences:

Cardiac

A

Shivering increases oxygen consumption up to 300%, increased myocardial ischemia, increased cardiac morbidity, increase arrhythmias, Osborne or J wave (ST elevation), VF occurs @ 22-23°C, defib not successful below 30°C, should resuscitate until rewarmed; “not dead until they’re warm and dead”

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20
Q

*** Hypothermia consequences:

Pulmonary

A

pulmonary vascular resistance increases, ventilatory drive is depressed, carbon dioxide levels in blood decrease

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21
Q

*** Hypothermia consequences:

Renal

A

Cold diuresis

Decreases plasma volume

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22
Q

*** Hypothermia consequences:

Hepatic

A

Hepatic blood flow is decreased

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23
Q

*** Hypothermia consequences:

CNS

A

cerebral oxygen consumption decreases 7% for each 1°C decrease, MAC decreases 5-7%/°C, delayed emergence, drowsiness, confusion

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24
Q

*** Hypothermia consequences:

Hematologic

A

Impaired platelet function and decreased platelet count, activity of coagulation factors is suppressed

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25
Q

*** Hypothermia consequences:

Metabolism

A

reduced by 50% at 30°C, 60% at 25°C; Slows drug metabolism, prolongs neuromuscular blockade, delays emergence, prolongs elimination of inhaled agents, increased plasma concentrations of propofol and fentanyl

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26
Q

*** Hypothermia consequences:

Healing

A

Contributes to wound infection by directly impairing the immune system, vasoconstriction leading to poor tissue oxygenation

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27
Q

Hypothermia =

A

slow wake up

reduced drug metabolism and elimination

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28
Q

*** For every degree Celsius drop in temperature, MAC decreases 5-7%, what does this mean

A

more gas has to come off before the patient will wake up

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29
Q

Hypothermia results directly in a diminished state of

A

consciousness

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30
Q

T/F: Neuromuscular blockers will linger in cold patients

A

True

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31
Q

What does hypothermia do to infection?

A

increased infections

Decreased peripheral perfusion, decrease cutaneous perfusion

Less penetration of antibiotics to these areas

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32
Q

Hypothermia leads to decrease ____ activity and impairment in ____ function

A

phagocytic

neutrophil

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33
Q

The body is divided into 2 compartments - what does the peripheral compartment consist of?

A

limbs, skin, and subcutaneous tissue

has 1/3 of the body’s heat content

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34
Q

The body is divided into 2 compartments - what does the core compartment consist of?

A

major thoracic and abdominal organs and brain

holds 2/3 of the body’s heat content

35
Q

Core body temperature is maintained within a narrow temperature range

A

36.6-37.4°C

36
Q

Peripheral body temperature varies widely

A

0-40 °C

37
Q

The difference between core and peripheral body temperatures is maintained by

A

vasoconstriction

38
Q

What does blood flow from the core to the skin provide?

A

heat transfer

39
Q

The degree of heat conduction to the skin is controlled by what?

A

degree of vasoconstriction in the skin

40
Q

What is vasoconstriction controlled by?

A

sympathetic nervous system

41
Q

Heat production is the principal by product of

A

metabolism

42
Q

Heat production is increased by

A

exercise, shivering, non-shivering thermogenesis, hyper metabolic states (sepsis, thyroid storm), medications or hypothalamic lesions

43
Q

Normal basal heat production would increase a patients core body temp by ____ per hour if they were completely insulated from heat loss

A

1.2°C

44
Q

Shivering can increase heat production by

A

300%

45
Q

Under normal conditions body heat is preserved by

A

tonic peripheral vasoconstriction

46
Q

*** 4 ways heat is lost

A

Radiation
Conduction
Convection
Evaporation

47
Q

Explain radiation heat loss

A

Loss of heat to cool surroundings via electromagnetic energy

Major method of heat loss to environment
Accounts for 60% of heat loss

Also affected by exposed body surface area

48
Q

How is radiation heat loss determined?

A

Determined by temp difference between patient and environment

49
Q

Explain convention heat loss

A

Wind chill - layer of air next to skin moves and carries heat away from body

Can account for 25% of heat loss in OR’s with forced airflow

Degree depends on body surface area exposed and airflow

50
Q

Explain evaporation heat loss

A

Loss of heat with skin prep solutions and in major surgeries with open abdominal cavities

Normal respiration of inspired gases can account for evaporative losses
Inspired gases are usually dry and moderately cool increasing heat loss

51
Q

Explain conduction heat loss

A

Transfer of heat between adjacent surfaces (OR table)

Contributes <5% of heat loss

Affected by temperature
gradient

52
Q

T/F: one reason pts get cold during anesthesia is they have little clothing and insulation

A

True

53
Q

How is core temp maintained during anesthesia?

A

Core temperature is maintained by peripheral vasoconstriction

54
Q

What does anesthesia (general and regional) do to peripheral vasoconstriction?

A

inhibit peripheral vasoconstriction

55
Q

In the 1st hour after induction of anesthesia there is a ____ decrease in the core temp because of peripheral vasodilatation

A

1.0-1.5°C

56
Q

Basal Metabolic Rate decreases _____ with general anesthesia decreasing heat production in the next 2-3 hours

A

20-40%

57
Q

T/F: Initial heat losses slow as most significant and slow with anesthetic time

A

True

58
Q

T/F: Regional anesthesia (spinal or epidural) produce similar patterns of heat loss again because of vasodilation

A

True

59
Q

What are some things that contribute to hypothermia?

A

Cold rooms, cold IV solutions and prepping solutions and skin exposure

60
Q

One unit of refrigerated blood or one liter of room temp crystalloid decrease core body temp by

A

0.25°C

61
Q

Cutaneous heat loss is proportional to exposed body surface area and accounts for ___ of heat loss

A

90%

62
Q

What does GA promote?

A

vasodilatation, decreases metabolic rate/heat production, and decrease hypothalamic responsiveness to hypothermia

63
Q

Neuromuscular blockers prevent

A

shivering

64
Q

What population is heatless more pronounced in?

A

elderly and neonatal patients

65
Q

Basal Metabolic Rate decreases approximately ___ per year beyond age 30

A

1%

66
Q

What is diminished in neonatal and elderly patients that results in less vasoconstrictive heat conserving mechanisms

A

diminished autonomic neural functioning

67
Q

Why do neonates have more rapid heat loss to the environment?

A

Neonates have increased surface area to mass

68
Q

What can you do preoperatively to prevent hypothermia?

A

Warm environment
Insulate patient with blanket
Actively warm so that peripheral body temp is warm, avoid sweating

69
Q

What can you do intraoperatively to prevent hypothermia?

A 
Warm the Operating Room
Make sure the patient is insulated 
Forced air warming ASAP
Circulating water mattress
Heat and Moisture Exchanger
Cover exposed areas
Use warmed IV fluid and warmed blood products
Field irrigation with warmed fluids
Use low flow circuits
Heating Lamps for neonates (↑body surface area/volume ratio)
Cardiopulmonary bypass warming
70
Q

What can you do postoperatively to prevent hypothermia?

A

Forced air warming

Treatment of Post Op Shivering

71
Q

Postop shivering occurs in what percent of unwarmed patients after general anesthesia?

A

40%

72
Q

What physiologic effects happen from post-op shivering?

A

Causes dramatic increases in oxygen consumption and catecholamine release

3 times increase in myocardial events

73
Q

How does shivering occur?

A

Induced by cooling of preoptic region of hypothalamus which causes the involuntary

oscillatory muscular activity occurs to increase heat production

74
Q

What is the best way to treat post-op hypothermia/shivering?

A

PREVENTION

75
Q

What is the most commonly used agent for post operative shivering

A

Meperidine (Demerol)

Partially mediated by kappa opioid receptors

Decreases shivering threshold twice as much as vasoconstriction threshold

76
Q

Is hyperthermia common in the OR?

A

NO

causes must be investigated

77
Q

Causes of hyperthermia

A 
Malignant Hyperthermia
Sepsis/Infection
Thyrotoxicosis
Pheochromocytoma
Hypothalamic lesion, trauma, anoxia
Neuroleptic Malignant Syndrome
Transfusion Reactions
Medications
78
Q

How does infection/sepsis cause hyperthermia?

A

During bacteremia, pyogens cause release of interleukin one, increasing the set point for temperature in the hypothalamus

This leads to heat conservation (vasoconstriction) and increased heat production (shivering)

79
Q

How does malignant hyperthermia manifest?

A

Initially manifests as a hyper catabolic state with tachycardia, hypercapnia, muscle rigidity, tachyarrythmias, metabolic acidosis

80
Q

What is the treatment for malignant hyperthermia?

A

Treatment includes discontinuing triggering agents, administering dantrolene, active cooling, adequate hydration, and supportive care

81
Q

Preop measures for hyperthermia

A

acetominophen

82
Q

Intraop measures for hyperthermia

A 
Cooling the OR
Forced Air cooling
Cooled IV Fluids
Field irrigation with cold fluids
NG, bladder irrigation with cooled fluids
83
Q

Postop measures for hyperthermia

A

Forced air cooling

Endocrine - Troutmanm (7 decks)

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