Exam2 IAs Flashcards

1
Q

Isoflurane 1 MAC

A

1.17%

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2
Q

Sevoflurane 1 MAC

A

1.80%

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3
Q

Desflurane 1 MAC

A

6.6%

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4
Q

Nitrous Oxide 1 MAC

A

104%

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5
Q

MAC

A

alveolar concentration at which 50% of subjects move in response to a noxious stimuli

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6
Q

Factors that increase MAC

A
CNS stimulants
alcohol abuser
young age (highest 6months)
hypernatremia
hyperthermia
hyperthyroidism
red haired females
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7
Q

Factors that decrease MAC

A

other drugs, elderly, electrolyte disturbance (hyponatremia), hypercarbic, hypothermic, hypoxic, pregnant, anemia

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8
Q

MAC fractions/multiples of inhalation agents are ______

A

additive

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9
Q

of MAC that prevents movement in 95% of patients on incision

A

1.3 MAC

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10
Q

Non-volatile anesthetics`

A

N2O

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11
Q

Volatile anesthetics

A

isoflurane, sevoflurane, desflurane

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12
Q

MACawake numeric value

A

1/3 MAC for most IAs

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13
Q

MACaware

A

concentration at which pt can remember events

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14
Q

MAC-BAR

A

average alveolar concentration which Blunts the Autonomic Response to a noxious stimuli (incision)

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15
Q

MAC-BAR is _____ compared to MAC

A

in excess

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16
Q

MAC-BAR50 for Sevo (combined with 66% N2O)

A

2.2

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17
Q

MAC-BAR50 for Sevo

A

2.2

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18
Q

MACaware is related to _____ not ________

A

amnesia not consciousness

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19
Q

MACaware numeric value

A

varies per patient

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20
Q

Pa measures?

A

partial pressure of agent in alveoli

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21
Q

______ is an indirect, yet reliable measure of Pbr

A

Pa

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22
Q

Fa

A

fractional concentration of anesthetic in the alveoli

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23
Q

Fi

A

fractional concentration of anesthetic in the inspired gas
OR
inspired concentration

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24
Q

cardiac output moves agent throughout body

A

distribution

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25
Q

evaluating uptake of inhaled anesthetics

A

Evaluating relationship between Fa and Fi

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26
Q

The faster Fa/Fi approaches _____ (#), the faster ______ will occur

A

1; induction

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27
Q

The less soluble the agent, the ____ the rate of rise (induction)

A

faster

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28
Q

Isoflurane Blood:Gas Partition Coeff.

A

1.46

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29
Q

Sevoflurane Blood:Gas Partition Coeff.

A

0.69

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30
Q

N2O Blood:Gas Partition Coeff.

A

0.46

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31
Q

Desflurane Blood:Gas Partition Coeff.

A

0.42

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32
Q

Factors that affect FA/FI

A

Solubility
Minute Ventilation and FRC
Cardiac Output
Anesthesia circuit characteristics

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33
Q

______ FRC will speed induction

A

decreased

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34
Q

________ is the most important factor in the rate of rise of the FA/FI

A

uptake

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35
Q

Uptake_______ the rate of rise of the Fa/Fi

A

slows

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36
Q

As cardiac output ______, Fa is lowered even more

A

increases

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37
Q

An increase in cardiac output will ______ uptake and _____ induction

A

increase uptake, slow induction

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38
Q

A _______ in cardiac output will ______ an inhalation induction

A

decrease; speed

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39
Q

Higher flow rates will ______ induction

A

speed up

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40
Q

Absorption of the circuit: if the circuit itself can absorb the anesthetic, ____ reaches the patient

A

less

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41
Q

Three factors of anesthesia circuit that effect induction speed

A
  1. fresh gas flows > 4LPM
  2. absorption by the circuit
  3. total circuit volume
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42
Q

Factors that increas speed of induction

A

Increased MV, fresh gas flow rate

Decreased agent solubility, CO, FRC, circuit volume

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43
Q

How do we know Fa?

A

exhaled concentrations by gas analyzer (mass spectrometry)

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44
Q

What is our most distal measurement?

A

Pa

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45
Q

Pa =

A

delivery into the alveoli (input) minus loss of drug into the blood (uptake)

46
Q

delivery into the alveoli

A

Input

47
Q

input depends on

A
  • inhaled partial pressure (Pi)
  • alveolar ventilation, FRC
  • anesthesia breathing machine characteristics
48
Q

A _____ Pi is required during initial administration of an anesthetic to offset the impact of uptake

A

high

49
Q

overpressure is related to which effect?

A

concentration

50
Q

All IAs produce _______ of ventilation

A

dose dependent depression

51
Q

Poorly soluble IAs

A

sevo
des
N20

52
Q

Intermediately soluble IAs

A

Iso

53
Q

increased solubility is _______ to the rate of rise of the Pa toward the Pi

A

inversely proportional

54
Q

ratio that describes how agent distributes between tissues at equilibrium

A

partition coefficients

55
Q

N2O contributes more to MAC in _______

A

Advanced age

56
Q

MAC is a form of

A

ED50

57
Q

Characteristics of the ideal anesthetic

A
Poorly soluble
Non-pungent
Non-flammable
Inexpensive
Easy to produce
Potent
Environmentally safe
No hepatic metabolism
Not a trigger for MH
Not emetogenic
58
Q

Average alveolar concentration permitting voluntary response to command

A

MACawake

59
Q

Pt responds to “Open your eyes!”

A

MACawake

60
Q

Pt responds to “Breathe!”

A

MACawake

61
Q

MACawake Isoflurane

A

38%

62
Q

MACawake Sevoflurane

A

0.6%

63
Q

MACawake Desflurane

A

2.2%

64
Q

MACawake N2O

A

64%

65
Q

The point at which patient loses the ability to learn

A

MACaware

66
Q

Which happens first:
A. Move and follow commands
B. Make memory

A

Move and follow commands

67
Q

Addition of _____ mcg/kg fentanyl reduces ______ by _____ %

A

1.5-3 mcg/kg fentanyl
MAC-BAR
50%

68
Q

MACawake concentrations of Sevo + N2O

A

Sevo 0.6%

N2O 60%

69
Q

MAC concentrations of Sevo + N2O

A

Sevo 1.8%

N2O 104%

70
Q

MAC-BAR concentrations of Sevo + N2O

A

Sevo 2.88%

Nitric - not possible

71
Q

Absorption of IAs

A

Uptake

72
Q

Uptake of IAs

A

Occurs when IAs move from alveoli into pulmonary capillary blood

73
Q

Principle objective of inhalation anesthesia

A

Achieve a constant and optimal brain partial pressure (as reflected by Pa or ET concentration via gas analyzer)

74
Q

Equilibrium occurs when

A

Partial pressure is equal in both phases

75
Q

% Body mass, % CO of vessel rich group

A

BM - 10%

CO - 75%

76
Q

% Body mass, % CO of Muscle group

A

50% BM

19% CO

77
Q

% Body mass, % CO of Fat Group

A

BM 20%

CO 5%

78
Q

% Body mass, % CO of vessel poor group

A

BM 20%

Blood flow 1%

79
Q

Pharmacokinetics of IAs

A
ADME
Absorption (uptake)
Distribution in body
Metabolism (minimal)
Elimination
79
Q

Uptake depends on

A
  1. Solubility of anesthetic in body tissues
  2. CO
  3. Alveolar to venous PP differences (A-vD)
79
Q

As the A-vD decreases what happens?

A

Rate of uptake into blood decreases

Pi should be decreased TO AVOID OVERDOSE

80
Q

What should you always do during the overpressure technique?

A

Keep your hand on the vaporizer to dial concentration back down

81
Q

Increasing alveolar ventilation will _____ the rate of rise of the Pa toward the Pi

A

Increase

82
Q

Hyperventilation hypothetically results in a ____ rate of rise of PBr

A

Delayed

D/t decreased CBF

83
Q

Effect of Spontaneous ventilation on induction

A

Delivery of IA is decreased as spontaneous ventilation is decreased; protective “negative feedback” loop

84
Q

Effect of mechanical ventilation on IAs

A

No decrease in ventilation as Pa approaches Pi

85
Q

Effect of high FGF during uptake

A
  1. Faster filling of the volume of anesthetic circuit (CO2 canister, breathing bag)
  2. Greater amount of Rx/time to replace gases taken up via alveoli
86
Q

Rubber/plastic parts of breathing circuit can take up anesthetic gases - how will this effect induction/emergence?

A
  1. Induction: slows rate of rise of Pa

2. Reverse gradients will delay the rate of the fall of Pa (delayed emergence)

87
Q

Solubilities of IAs in blood/tissues are denoted by

A

Ostwald Partition Coefficients

88
Q

Ostwald partition coefficient

A

Distribution ratio that describes how anesthetics distribute between 2 phases (partial pressures equilibriate, NOT CONCENTRATION) at 37degreeC at atmospheric pressure.

89
Q

Which is more soluble in blood - ISO or N2O?

A

ISO
(Iso has 1.5 molecules in blood for every molecule it has in alveolar gas; while N2O has 1 molecule in the blood for every 1/2 molecule in alveolar gas)

90
Q

Determine uptake into tissues and time necessary to do so

A

Tissue:Blood partition coefficients

91
Q

Time constant

A

Time to equilibration of PPs between blood and tissue phase

92
Q

Required for 95% equilibration of PPs between blood/tissue phase

A

3 time constants

93
Q

Pa:Brain equilibration requires _______ for IAs

A

5-15 minutes

94
Q

TC of Pa:Brain equilibration

A

TC = 2-5 minutes

95
Q

Changes in CO affect _____ soluble agents more

A

Highly

96
Q

Which agent has a rapid rise in Pa despite CO changes?

A

N2O

97
Q

A-vD

A

Alveolar to Venous partial pressure differences

Reflects tissue uptake of IAs

98
Q

A-vD is dependent on

A

Solubility of agent in tissues
Tissue blood flow
Arterial-tissue PP differences

99
Q

Concentration effect is a result of _____ uptake of the ____ gas leaves the _____ gas in the alveoli in ______ concentration

A

Concentration effect is a result of __Rapid___ uptake of the __1st__ gas leaves the ___2nd__ gas in the alveoli in __greater____ concentration

100
Q

If two gases are given and the second gas is O2, leftover in the alveolus, what occurs?

A

Hyperoxygenation

101
Q

Does percutaneous loss affect metabolism of IAs?

A

No

102
Q

Will underpressuring speed recovery?

A

No

103
Q

Will equilibrium be achieved in all tissues at conclusion of surgery?

A

No

104
Q

Time to recovery is longer for ____ soluble agents

A

More soluble agents

105
Q

How does the anesthetic circuit affect rate of recovery?

A

The absorbed anesthesia will return to the inspired flow and slow the rate of decrease of Pa

106
Q

Elimination of IAs depends on

A

Length of administration

Blood:Gas solubility of agent

107
Q

Initial decrease of anesthesia

A

<5 minutes

Does not vary with duration

108
Q

Initial phase of elimination is a function of

A

Alveolar ventilation

109
Q

Major differences in elimination for IAs

A

During final 20%