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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
*** Hypothermia consequences: | Metabolism
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
26
*** Hypothermia consequences: | Healing
Contributes to wound infection by directly impairing the immune system, vasoconstriction leading to poor tissue oxygenation
27
Hypothermia =
slow wake up | reduced drug metabolism and elimination
28
*** For every degree Celsius drop in temperature, MAC decreases 5-7%, what does this mean
more gas has to come off before the patient will wake up
29
Hypothermia results directly in a diminished state of
consciousness
30
T/F: Neuromuscular blockers will linger in cold patients
True
31
What does hypothermia do to infection?
increased infections Decreased peripheral perfusion, decrease cutaneous perfusion Less penetration of antibiotics to these areas
32
Hypothermia leads to decrease ____ activity and impairment in ____ function
phagocytic neutrophil
33
The body is divided into 2 compartments - what does the peripheral compartment consist of?
limbs, skin, and subcutaneous tissue has 1/3 of the body’s heat content
34
The body is divided into 2 compartments - what does the core compartment consist of?
major thoracic and abdominal organs and brain holds 2/3 of the body’s heat content
35
Core body temperature is maintained within a narrow temperature range
36.6-37.4°C
36
Peripheral body temperature varies widely
0-40 °C
37
The difference between core and peripheral body temperatures is maintained by
vasoconstriction
38
What does blood flow from the core to the skin provide?
heat transfer
39
The degree of heat conduction to the skin is controlled by what?
degree of vasoconstriction in the skin
40
What is vasoconstriction controlled by?
sympathetic nervous system
41
Heat production is the principal by product of
metabolism
42
Heat production is increased by
exercise, shivering, non-shivering thermogenesis, hyper metabolic states (sepsis, thyroid storm), medications or hypothalamic lesions
43
Normal basal heat production would increase a patients core body temp by ____ per hour if they were completely insulated from heat loss
1.2°C
44
Shivering can increase heat production by
300%
45
Under normal conditions body heat is preserved by
tonic peripheral vasoconstriction
46
*** 4 ways heat is lost
Radiation Conduction Convection Evaporation
47
Explain radiation heat loss
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
How is radiation heat loss determined?
Determined by temp difference between patient and environment
49
Explain convention heat loss
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
Explain evaporation heat loss
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
Explain conduction heat loss
Transfer of heat between adjacent surfaces (OR table) Contributes <5% of heat loss Affected by temperature gradient
52
T/F: one reason pts get cold during anesthesia is they have little clothing and insulation
True
53
How is core temp maintained during anesthesia?
Core temperature is maintained by peripheral vasoconstriction
54
What does anesthesia (general and regional) do to peripheral vasoconstriction?
inhibit peripheral vasoconstriction
55
In the 1st hour after induction of anesthesia there is a ____ decrease in the core temp because of peripheral vasodilatation
1.0-1.5°C
56
Basal Metabolic Rate decreases _____ with general anesthesia decreasing heat production in the next 2-3 hours
20-40%
57
T/F: Initial heat losses slow as most significant and slow with anesthetic time
True
58
T/F: Regional anesthesia (spinal or epidural) produce similar patterns of heat loss again because of vasodilation
True
59
What are some things that contribute to hypothermia?
Cold rooms, cold IV solutions and prepping solutions and skin exposure
60
One unit of refrigerated blood or one liter of room temp crystalloid decrease core body temp by
0.25°C
61
Cutaneous heat loss is proportional to exposed body surface area and accounts for ___ of heat loss
90%
62
What does GA promote?
vasodilatation, decreases metabolic rate/heat production, and decrease hypothalamic responsiveness to hypothermia
63
Neuromuscular blockers prevent
shivering
64
What population is heatless more pronounced in?
elderly and neonatal patients
65
Basal Metabolic Rate decreases approximately ___ per year beyond age 30
1%
66
What is diminished in neonatal and elderly patients that results in less vasoconstrictive heat conserving mechanisms
diminished autonomic neural functioning
67
Why do neonates have more rapid heat loss to the environment?
Neonates have increased surface area to mass
68
What can you do preoperatively to prevent hypothermia?
Warm environment Insulate patient with blanket Actively warm so that peripheral body temp is warm, avoid sweating
69
What can you do intraoperatively to prevent hypothermia?
``` 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
What can you do postoperatively to prevent hypothermia?
Forced air warming | Treatment of Post Op Shivering
71
Postop shivering occurs in what percent of unwarmed patients after general anesthesia?
40%
72
What physiologic effects happen from post-op shivering?
Causes dramatic increases in oxygen consumption and catecholamine release 3 times increase in myocardial events
73
How does shivering occur?
Induced by cooling of preoptic region of hypothalamus which causes the involuntary oscillatory muscular activity occurs to increase heat production
74
What is the best way to treat post-op hypothermia/shivering?
PREVENTION
75
What is the most commonly used agent for post operative shivering
Meperidine (Demerol) Partially mediated by kappa opioid receptors Decreases shivering threshold twice as much as vasoconstriction threshold
76
Is hyperthermia common in the OR?
NO | causes must be investigated
77
Causes of hyperthermia
``` Malignant Hyperthermia Sepsis/Infection Thyrotoxicosis Pheochromocytoma Hypothalamic lesion, trauma, anoxia Neuroleptic Malignant Syndrome Transfusion Reactions Medications ```
78
How does infection/sepsis cause hyperthermia?
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
How does malignant hyperthermia manifest?
Initially manifests as a hyper catabolic state with tachycardia, hypercapnia, muscle rigidity, tachyarrythmias, metabolic acidosis
80
What is the treatment for malignant hyperthermia?
Treatment includes discontinuing triggering agents, administering dantrolene, active cooling, adequate hydration, and supportive care
81
Preop measures for hyperthermia
acetominophen
82
Intraop measures for hyperthermia
``` Cooling the OR Forced Air cooling Cooled IV Fluids Field irrigation with cold fluids NG, bladder irrigation with cooled fluids ```
83
Postop measures for hyperthermia
Forced air cooling

Endocrine - Troutmanm (7 decks)

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