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NUNA 681(pharm) > Uptake and Distribution- Pharmacokinetics of Volatile Agents > Flashcards

Uptake and Distribution- Pharmacokinetics of Volatile Agents Flashcards

1
Q

process of getting the anesthetic agent from the anesthetic machine to the patient’s CNS

A
  1. vaporizer
  2. circuit
  3. alveoli
  4. blood/arterial
  5. brain (CNS)
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2
Q

the series of partial pressure gradients to move agent through barrier to the CNS

A

PA—–Pa—–Pbr

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3
Q

partial pressure between alveolar and arterial equilibrate

A

quickly

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4
Q

arterial partial pressure equilibrate __ with the brain

A

rapidly

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5
Q

alveolar pressure don’t produce __ directly

A

unconsciousness

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6
Q

we use alveolar concentration as

A

a stand-in for CNS/brain concentration

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7
Q

fresh gas flow is determined by

A

the vaporizer and flowmeter settings

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8
Q

Fi (inspired gas concentration) is determined by

A

FGF rate, breathing-circuit volume, and circuit absorption

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9
Q

FA (alveolar gas concentration) is determined by

A

uptake, ventilation, and the concentration/second gas effect- concentrating agent and augmented inflow effect

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10
Q

Fa (arterial gas concentration) is affected by

A

ventilation/perfusion mismatching

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11
Q

a high inspired or inhaled partial pressure (PI) initially offsets

A

the impact of uptake and speeds induction (rise in PA and thus Pbr)

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12
Q

concentration effect

A

the higher the PI, the more rapidly the PA approaches the PI

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13
Q

second-gas effect

A

high volume uptake of one gas to accelerate the rate of increase of the PA of a concurrently administered “companion gas”

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14
Q

as equilibrium is achieved and uptake is slowed, the __ must be reduced to maintain a constant __

A

PI

Pbr

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15
Q

greater alveolar ventilation promotes

A

delivery of anesthetic agent to offset uptake

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16
Q

___ induction with greater alveolar ventilation

A

more rapid

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17
Q

__ induction with decreased alveolar ventilation

A

slower

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18
Q

the effect of increasing ventilation will be most obvious in raising the FA/FI for

A

more soluble anesthetics, as the are more subject to uptake

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19
Q

anesthetic agents impact their own uptake due to the

A

dose-dependent depressant effects on alveolar ventilation

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20
Q

if controlled ventilation is used there is potential for

A

overdose

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21
Q

time constant is

A

the time required for flow through a container to equal the volume of the container

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22
Q

time constant =

A

capacity (L) / flow (L/min)

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23
Q

time constant is the amount of time in minutes required for

A

a 63% turnover of gas within a container

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24
Q

application of time constant is in

A

the rate of alveolar rise in anesthetic concentration

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25
Q

time constant multiple 1

A

63%

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26
Q

time constant multiple 2

A

86%

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27
Q

time constant multiple 3

A

95%

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28
Q

time constant multiple 4

A

98%

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29
Q

time constant multiple 5

A

99.5%

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30
Q

vessel rich group receives __ of CO

A

75%

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31
Q

lean muscle receives __ of CO

A

19%

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32
Q

fat receives __ of CO

A

6%

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33
Q

vessel poor group receives __ of CO

A

0%

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34
Q

__ takes away from what is going to the alveoli

A

the volume of gas in the circuit

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35
Q

___ negates what the machine takes away from the alveoli

A

higher fresh gas flows (5-10 L/min)

36
Q

__ in the rubber/plastic components of breathing system slows the rise of the PA initially

A

solubility of an agent

37
Q

circle system allows

A

rebreathing of previously exhaled gas

38
Q

exhaled gas contains

A

lower concentration of agent during the initial uptake phase because some is taken out by the body

39
Q

the agent concentration coming in the fresh gas from the machine is

A

diluted down by mixing with the exhaled gas

40
Q

in non-rebreathing circuits, exhaled gas is

A

no rebreathed and high flow are required

41
Q

in non-rebreathing circuits, the concentration of agent in the circuit is

A

very close to the concentration set on the vaporizer dial

42
Q

in non-rebreathing circuits, is the gas is soluble in the material of the circuit or system, some agent will

A

be lost to these materials

43
Q

functional residual capacity is composed of

A

the residual volume and the expiratory reserve volume

44
Q

the larger the FRC, the __ the induction of the anesthetic agent

A

slower

45
Q

__ have smaller FRC than adults as a percent of TLV, more volume changed with

A

neonates

each respiration and faster induction with anesthetic agent than adults

46
Q

solubility is

A

blood:gas partition coefficient

47
Q

solubility definition

A

a distribution ratio describing how the anesthetic distributes itself between two phases at equilibrium (steady state)

48
Q

the lower the solubility, the __ the rate of rise of the PA toward the PI

A

faster

49
Q

partition coefficients are

A

temperatrue dependent

50
Q

decreased temperature causes

A

increased solubility

51
Q

increased temperature causes

A

decreased solubility

52
Q

the initial steep rise of FA/FI is due to

A

unopposed filling of the alveoli by ventilation

53
Q

CO (pulmonary blood flow) affects uptake by

A

carrying away agent from the alveoli and preventing the rise in PA

54
Q

increased CO leads to

A

greater uptake/removal of agent from the lungs and slowed induction

55
Q

the rate of increase of __ is affected more by CO

A

more soluble agents

56
Q

the increase in CO will __ induction and the rise in PA

A

slow

57
Q

during uptake, __ will remove the anesthetic agent that is delivered

A

the vessel rich group

58
Q

the mixed venous blood returning to the lungs has

A

a lower partial pressure of agent

59
Q

the gradient between the alveolar partial pressure and the venous blood is __ encouraging __

A

great

diffusion out of the alveoli

60
Q

as saturation of the VRG increase, ___ becomes smaller and the __ rises

A

gradient

PA

61
Q

arterial partial pressure is __ then ETgas

A

less

62
Q

___ enhances the difference in Pa and ETgas

A

right to left shunt

63
Q

lower Pa with

A

right to left shunt, especially with less soluble agents

64
Q

__ poorly estimates __, with right to left shunt

A

PA

Pa

65
Q

V/Q mismatch is seen with

A

bronchial intubation or right to left intracardiac shunt

66
Q

factors determining transfer of agent from arterial blood to brain

A
  1. brain:blood partition coefficient
  2. cerebral blood flow
  3. arterial to venous partial pressure difference
67
Q

vessel rich group includes

A
  1. brain
  2. heart
  3. kidney
  4. splanchnic
  5. liver
  6. endocrine
68
Q

muscle group contains

A

muscle and skin

69
Q

vessel poor group contains

A
  1. bone
  2. ligament
  3. cartilage
70
Q

rapid increase in FA/FI thats

A

faster induction

71
Q

to have faster accumulation/onset/wash-in you need

A
  1. higher FGF
  2. higher alveolar ventilation
  3. decrease FRC
  4. smaller time constant
  5. smaller amount of anatomic dead space
72
Q

to increase FA/FI decrease amount of uptake

A
  1. gas with lower solubility
  2. low CO
  3. difference between arterial pressure and venous pressure smaller
73
Q

to decrease rate of FA/FI meaning slower onset/build up

A
  1. decrease FGF
  2. decrease AV
  3. higher FRC
  4. higher time constant
  5. higher amount of anatomic dead space
74
Q

decrease FA/FI meaning slower induction with increased uptake

A
  1. higher solubility
  2. higher CO
  3. higher difference in Pa/Pv
75
Q

elimination generally =

A

reverse of uptake

76
Q

slower awakening with

A

higher soluble, longer duration of exposure, higher concentration

77
Q

elimination via

A

exhalation predominantly so increase alveolar ventilation

78
Q

factors associated with increased rate of recovery

A
  1. elimination of rebreathing
  2. high FGF
  3. low anesthesia-circuit volume
  4. low absorption by anesthesia circuit
  5. decreased solubility of agent
  6. high cerebral blood flow
  7. increased alveolar ventilation
79
Q

implication for rapid recovery

A
  1. airway protection/oxygenation
  2. rapid movement through the 0.1 MAC concentration that causes enhanced perception of pain
  3. return to normal CV function
  4. turnover more rapid
  5. quicker discharge from PACU
  6. quicker return to normal activities
80
Q

changes in compartments in elderly

A

decreases in lean body mass and increases in body fat

81
Q

volume of distribution in elderly

A

of central compartment is smaller (plasma volume)

for volatiles is larger (especially more lipid soluble agents)

82
Q

elderly clearance

A

decreased due to impaired pulmonary gas exchange

83
Q

elderly CO

A

reduced

84
Q

reduced CO in elderly leads to

A

reduced tissue perfusion, increased time constants, altered regional distribution of anesthetics

85
Q

does switching to a less soluble agent at the end of a case help?

A

no, it is additive or even synergistic effect regarding return to mental function

NUNA 681(pharm) (12 decks)

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