Inhalation Agents Flashcards

1
Q

Potency is directly related to what?

A

lipid solubility

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2
Q

what provides a quantitative measure of lipid solubility (aka potency)

A

oil:gas partition coefficient

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3
Q

what is minimal alveolar concentration (MAC)?

A

the alveolar concentration of an inhalation agent at which 50% of patients do not move in response to skin incision or similar noxious stimuli

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4
Q

is MAC inversely or directly proportional to potency (lipid solubility)

A

inversely proportional

the lower the MAC the higher the potency

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5
Q
list the MAC's and put the following in order from least to most potent.
halothane 
Des
Sevo
iso
Enf
N20
A
N20- 104%
Des- 6.6%
Sevo-1.7%
Iso- 1.2 (1.15)%
Enf- 1.6 %
Hal- 0.75%

enflurane is the one exception

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6
Q

temp and solubility:

what happens to solubility of gas in a liquid as temp increases

A

decreases

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7
Q

temp and solubility:

the solubility of gas decreases in a liquid as temp increases. how does this apply to out pts

A

less inhalation agent will dissolve in blood if pt hyperthermic
more inhalation agent will dissolve in blood if pt hypothermic

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8
Q

Uptake and elimination:

what determines speed of onset and elimination

A

blood solubility

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9
Q

Uptake and elimination:

what provides a quantitative measure of blood solubility?

A

blood:gas partition coefficient

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10
Q

Uptake and elimination:

which inhalation agents have the faster uptake thus onset the one with a high or low blood:gas

A

low

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11
Q

Uptake and elimination:

what are the 3 determinants of brain uptake and induction speed? and explain how?

A
  • blood solubility- lower blood:gas faster onset
  • Alveolar ventilation- the greater the ventilation the faster uptake
  • Cardiac output- inversely related- decreased CO faster onset
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12
Q

Uptake and elimination:

old people with low CO will their IV inhalation be slow or fast? will there inhalation agent onset be slow or fast?

A

IV- slow

Inhalation agent- fast

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13
Q

Blood:gas partition coefficient:

agents with high blood solubility means they are more soluble where?

A

in blood

they prefer to be in the blood not gas

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14
Q

Blood:gas partition coefficient:

agents with low blood solubility means thay are more soluble where?

A

in gas

prefer to be in gas

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15
Q

Blood:gas partition coefficient:

explain the blood:gas partition coefficent for halothane 2.50 and then nitrous oxide 0.46

A

halothane 2.50:1 = 250:100 (250 molecules in blood and 100 in gas) - means the affinity (solubility) in blood is 2.5 x’s higher than the gas state

nitrous 0.46:1 = 46:100 (46 molecules in blood and 100 in gas)- means solubilty in blood is 0.46 x’s that in gas state)

aka nitrous oxide has a much faster onset than halothane

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16
Q

Blood:gas partition coefficient:

why is it that the lower the blood:gas the faster the onset

A

b/c the alveoli or the windows to the brain (AKA more in the alveoli=more in the brain), thus more in the gas phase the more in the alveoli

17
Q

what is the Blood:Gas:

N20

A

0.46

18
Q

what is the Blood:Gas:

des

A

0.42

19
Q

what is the Blood:Gas:

sevo

A

0.7

20
Q

what is the Blood:Gas:

iso

A

1.46

21
Q

what is the Blood:Gas:

enflurane

A

1.9

22
Q

what is the Blood:Gas:

halothane

A

2.5

23
Q

after 30 min, halothane will be how close in % to equilibration?

A

think 50%

but actual answer 58%

24
Q

after 30 min, isoflurane will be how close in % to equilibration?

A

think 70’s

actual answer 73%

25
Q

N20 is ___ x’s more soluble the N2

A

34 times

26
Q

what law explains why gas bubbles distend when N20 is turned on or collapse when N20 is turned off?

A

fick’s law of diffusion

27
Q

when N20 is turned on, distensible gas spaces expand and non-distensible gas spaces do what?

A

increase in pressure

28
Q

Concentration effect:

what is it similar to?

A

a loading dose

29
Q

Concentration effect:

explain it

A

the higher the concentration of anesthetic agent delivered, the faster the anesthesia is achieved.

30
Q

Concentration effect:

is also referred ti as what?

A

overpressuring

31
Q

2nd gas effect:

explain

A

2 anesthetics of varying onset speeds are administered together. a high concentration the fast anesthetic (N20) is administered with a slower (ISO). like the concentration effect w/a friend