temperature ppt notes Flashcards
Heat is a form of what?
energy (kinetic energy)
Heat can be transfered from a hotter substance to a colder one, but never what?
cold to hot
what is the measured thermal state of a substance whch quantifies the energy distribution among the molecules in a system?
Temperature
what properties of a substance change with temperature changes?
physical properties
what is the standard unit of temperature?
kelvin
K
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0 K= what C
0 C= what K
0 k = what
how do u convert C to K
-273.15 C
273 K
absolute 0
add 273.15
what is 1 calorie
the amt of heat needed to raise the temp of 1 g of h20 by 1 degree C
what occurs to kenetic energy during freezing and thawing
decreases when cools (freezing)
Increases when warms (thawing)
The majority of the body’s heat is locted where?
core
- brain
- thorax
- abdomen
since core temp is the gold standard where are some common sites to measure this
pulm artery
esophagus
rectum
bladder
tympanic
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metabolic rate increases by ___ - _____% for each degree C increase in core temp
6-7%
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CO increases by ________ per degree C
3L/min
the body compensates for excessive heat loss by what 2 ways
- decreasing rate of loss
- increasing rate of heat production
Heat is a product of what?
and thus heat can be increased by increasing what?
metabolism
metabolism
what is an effective way of increasing metabolism?
shivering
The down fall of shivering is an increase in O2 consumption by 400-500%, this emphesizes the importance of us doing what?
keeping out pt’s warm to prevent stressful increases in metabolism
What is non-shivering thermogenesis?
complex mechanism not involving ATP
triggers brown fat metabolism
what effects does Anesthesia have on thermoregulation
- general and regional anesthesia blunt the normal thermoregulatory mechanism
- Potent inhaled agents cause vasodilation and disrupt normal hypothalmic shivering regulation
- inhalation agents, propofol induction, vasodilating drugs, and regional anesthetics induce vasodilation
- regional- heat loss due to loss of sympathetic tone
The greatest decrease in core body temp occurs when during anesthesia
1st hour of operative time
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4 routes of heat loss
Radiation
Convection
Conduction
Evaporation
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most heat is lost from the body by what route
Radiation
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Burn pt’s lose the highest % of heat by what route
Evaporation
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What route is the transfer of heat energy by emission of infra-red radiation (energy) to the surrounding walls, equip, floor…etc
give ex
radiation
Heat just leaves your body
stop by placing a blanket on pt
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what type of heat loss is the transfer of thermal energy by heating air adjacent to the skin, it increases kinetic energy expands, becoming less dense and rises carrying heat away
give ex
Convection
air currents pass by and remove the heat, we literally blow it away
in pool and water finally gets warm then u move and it is cold again,
WHat type of heat loss is the loss of heat (transfer) by direct contact with a less hot substance
give ex
Conduction
when u sit in a chair and get up the chair is hot from your ass
the good thing is the heat can be maintained by the contact
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what type of heat loss is due to loss of latent heat of vaporization of moisture on the skin. Thi is limited by the gradient of skin H2O to atmospheric H2O difference
give ex
Evaporation
sweating
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What is the formula for evaporation
H20L+ Heat= H2OG
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What is Absolute humidity and how is it measured
the mass of water vapor in given volume of air
Grams (g)
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what is relative humidity? and how is it written?
The RATIO of the mass of water vapor in a giver volume of air to the mass required to saturate that given volume of air at the same temp
percent (%)
actual H2O vapor / Max. potential H2O saturation
why does relative humidity increase a the temperature falls?
b/c the saturate vapor pressure falls
Fully saturated air at 370C cantains how much water
44mg/L
How do we humidify gasses?
Foam noses
electrical humidifiers/ nebs
Soda lime
Moistened circuit
low dry gas flows
what are risk factors for perioperative hypothermia
age increased
GA
regional Anesthesia
ASA III or IV
trauma
Low body fat
Endocrin D/O
OR temp
abd cases OPEN
Cold fluids
Length
High gas flows
what is the #1 risk factor for periop hypothrmia
GA
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a temp of this causes what CV effects
**33-36oC
**32-33oC
<30oC
19-20oC
**Increased HR BP CO
**Decreased HR BP CO
bradycardia, v-fib
asystole
**important
Hypothermia of renal, at temp < 33oC can cause what
polyuria
Hypothermia effects of hematological system
HCT rises(from fluid shift interstitial)
increased coags (plt’s are sequestered in spleen and liver)
Methods of acheiving and maintaining perioperative normothermia
Circulating water matress
Heated humidifiers
*low fresh gas flows (decreases evaporation) 0.5-1 L/min
Metallic reflective blankets
heat and moister exchangers (artificial noses)
warm IV fluid
Ambient temp (increase room temp)
Forced air warming blankets (bair hugger)
The easiest way to prevent heat loss is to stop what?
radiation
More heat = more what?
kinetic energy
Where does heat start at?
cellular level with ATP
Heat is a product of what?
Metabolism
what is a d/o of hypermetabolism (rare)
MH
shivering increases O2 comsumption by how much
400-500%
Brown fat metabolism occurs in primarimy whom
babies and neonates
what is a great way you can reduce evaporation
use low gas flows
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fully saturated air at 370C contains how much water
44mg/L
(i also wrote 1g=ml i don’t know why or what it ment)
of the absolute humidity of gas in the lungs at 370C is 44mg/L what should happen if then is 350C
be less than 44
the relative humidity of gas in the lungs is always what
100%
970F is how much K
97-32 x 5/9=K
97-32=65
65 * 5=325
325/9=36.111111111
36.1+273.15=309.25 K
