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Anesthesia Pharm > Inhaled Anesthetics > Flashcards

Inhaled Anesthetics Flashcards

1
Q

Nitrous oxide has ____ potency and _____ solubility

A

Low and Poor

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2
Q

What is the blood-gas partition coefficient?

A

A ratio of how soluble a substance is in blood compared to air.

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3
Q

If a gas has a blood-gas partition coefficient of 1.7 that means:

A

The gas is 1.7 times more soluble in blood than air at equilibrium

Since the drug is highly soluble, it will have a longer induction time

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4
Q

As the gas-blood partition coefficient increases, the MAC will generally ______

A

decrease

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5
Q

High Solubility = ____ induction

Low Solubility = ______ induction

A

High = Slow induction

Low = Fast induction

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6
Q

Fluorination increases ______ and decreases ______

A

Increases potency

Decreases flammability

This is why modern inhaled anesthetics are ethers but they are not flammable

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7
Q

What is MACBAR?

A

MAC required to block adrenergic response

It’s approximately 1.5 MAC

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8
Q

What is the MACAWAKE for Des/sevo/iso?

A

Approximately 0.33 MAC

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9
Q

When we say a gas has a MAC of 6%, it’s 6% of what?

A

It’s 6% of 1 ATM (760 mmHg)

So 6% is a partial pressure of 45.6mmHg

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10
Q

How will metabolic acidosis impact MAC?

A

decreases MAC

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11
Q

Acute alcohol use _____ MAC

Chronic alcohol use _____ MAC

A

Acute decreases

chronic increases

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12
Q

Will pregnant women have a higher or lower MAC?

A

Usually lower, because they have a higher level of circulating endorphins

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13
Q

How does serum sodium impact MAC?

A

Hypernatremia increases MAC

hyponatremia decreases MAC

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14
Q

In animals without brains, how is MAC impacted?

A

It isn’t, which suggests MAC is spinal cord mediated

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15
Q

Why does chronic meth use decrease MAC?

A

Depleted norepinephrine levels in the brain mean there’s less stimulation to overcome

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16
Q

Acute meth use will _____ MAC

A

increase

More norepinephrine stimulation to overcome

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17
Q

What is vapor pressure?

A

the pressure at which you have equal vaporization and condensation

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18
Q

What is the impact of pressure on vaporization?

A

Pressure reduces vaporization even at higher temperatures in which the substance would usually vaporize

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19
Q

What does it mean if a substance has a high vapor pressure?

A

That it really wants to vaporize

BECAUSE if it’s prone to vaporize, a lot more of its molecules will have to be vaporized before an equal number will begin condensing

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20
Q

What does high volatility mean?

A

That a substance really wants to evaporate

High volatility = high vapor pressure

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21
Q

When the vapor pressure is equal to the atmospheric pressure, you have reached:

A

the boiling point

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22
Q

Why don’t you have to adjust the dial for Sevo or Iso at altitude?

A

The percentage delivered at altitude is significantly higher than at 1 ATM, HOWEVER the partial pressure really isn’t

Since partial pressure is what we actually care about, there isn’t a huge need to adjust the dials

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23
Q

Why do you have to adjust Des at altitude, but not Iso or Sevo?

A

Unlike Sevo or Iso, Des is in a controlled, heated environment where it will always give off a set percentage

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24
Q

What determines how the rate of anesthetic onset?

A

The rate of rise of the partial pressure in the alveolus

NOT determined by how much of the anesthetic is absorbed in the blood

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25
Q

How does cardiac output influence rate of onset of inhaled anesthetics?

A

The more blood moving through the lungs, the higher the amount of solubility, which means onset will be slower

this means a high CO will increase the time it takes

A low CO will decrease the time it takes

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26
Q

The partial pressure in the lung is equal to the partial pressure in the ______

A

brain

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27
Q

What is the FA/FI curve representing?

A

How long it takes for the alveolar anesthetic concentration to equal the inspired anesthetic concentration

If I have the dial set to 2.1%, how long it takes for the exhaled concentration to reach 2.1%

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28
Q

What is the concentration effect?

A

Hypothetically, you would think that FA/FI would reach 1 at the same rate no matter what percentage we’re going for

If you give 6% it should take x amount of time for FA to reach 6%, and if we gave 60% it should take the same amount of time.

But it doesn’t. When you give a higher concentration of gas, the FA/FI reaches 1 much, much faster

Since Nitrous is the only gas we routinely use where we give large amounts, it’s the only gas effected by concentration

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29
Q

What is the metabolism rule of 2s?

A

Percent that is metabolized:

Halothane 20%

Sevo 2%

Iso 0.2%

Des 0.02%

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30
Q

In the CO2 absorber, Sevo can form _____ and Des can form ______

A

Sevo can form Compound A

Des can form carbon monoxide

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31
Q

What is the MAC of Sevo?

A

2%

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32
Q

What is the MAC of Des?

A

6.6%

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33
Q

What is the MAC of Iso?

A

1.15%

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34
Q

Why do inhalational agents drop the MAP?

A

Reduced SVR, NOT reduced CI

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35
Q

Volatile anesthetics are coronary vaso ______

A

dilators IN THE EPICARDIUM

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36
Q

What is coronary steal?

A

You’d think vasodilating the coronary vessels would be helpful in patients who have some blockages

BUT in those patients with partial blockages, they’re already vasodilated at the site of ischemia and vasoconstricted at other sites, allowing for increased flow through the partial occlusion

if you give an anesthetic agent, it vasodilates all the arteries, and the beneficial action of dilating the partially occluded artery decreases. You wind up stealing blood from the ischemic area.

DOES NOT HOLD UP IN THE RESEARCH

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37
Q

How do inhaled anesthetics impact the ECG?

A

Prolong QT

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38
Q

What do you do if a patient has a long QT at baseline?

A

Pretreat with beta blockers prior to anesthetizing

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39
Q

What effects on respiration do inhaled anesthetics cause?

A

Increased RR

Decreased Vt

Combination results in increased dead space, reducing alveolar ventilation

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40
Q

How do volatile anesthetics impact apneic threshold?

A

Increased

It will take a higher CO2 concentration in the arteries to spark apneic breathing mechanisms

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41
Q

What is the impact of volatile anesthetics on cerebral perfusion?

A

Increased

Blood flow goes up and metabolism goes down, which can cause increased ICP

Can be mitigated by increasing RR

42
Q
A

Sevo

43
Q

List the ethers

A

Des/Iso/Sevo

Enflurane

Methoxyflurane

Ether

44
Q

How can you identify an ether?

A

The ether bridge:

C - O - C

45
Q

List the alkanes

A

Halothane

Chloroform

46
Q

List the gases

A

Nitrous Oxide

Xenon

47
Q
A

Desflurane

48
Q
A

Isoflurane

49
Q

What effect does adding the Cl atom to Isoflurane have on its actions?

A

Increases potency by making the molecule heavier

increases blood and tissue solubility

50
Q
A

Halothane

The absence of an ether bridge and presence of a Bromine are dead giveaways

51
Q

Desflurane is fully flurinated. How does this impact its effect?

A

Decreased potency

Increased vapor pressure

Increased resistance to biotransformation

52
Q

What does it mean for a gas to be stable?

A

ability to resist being broken down and metabolized

53
Q

Des and Iso can become unstable in ______ producing ______

A

Desiccated soda lime

CO

54
Q

VAPOR PRESSURE

SEVO/DES/ISO/NITRO

A

Sevo: 157

Des: 669

Iso: 238

Nitrous: 38,770

55
Q

BOILING POINT

SEVO/ISO/DES/NITROUS

A

Sevo: 59

Iso: 49

Des: 22

Nitrous: -88

56
Q

BLOOD:GAS COEFFICIENT

SEVO/DES/ISO/NITROUS

A
57
Q
A

Nitrous

Des

Sevo

Iso

58
Q

The VRG contains which organs?

A

Brain

Heart

Liver

Kidneys

Endocrine Glands

59
Q

How does FRC effect wash in?

A

If your FRC is increased, that means there is more space to fill with gas, and the wash in will take longer

If your FRC is decreased, there is less space to fill with gas, and the wash in will be shorter

60
Q

HEPATIC BIOTRANSFORMATION

DES/SEVO/ISO/NITROUS

A
61
Q

Which anesthetic gases produce TFAs?

A

Primarily halothane (halothane hepatitis)

but also des and iso

Des and Iso are low in number, but since halothane hepatitis is immune mediated, if a patient had halothane hepatitis, they really should be re-exposed to any amount of TFAs

62
Q

What are the metabolites of Sevo, and what can they cause?

A

Free Fluoride Ions

Hypothetically they can cause high output renal failure that looks like DI

But there’s no evidence of this in humans

63
Q

What are the metabolites of Nitrous?

A

None. It isn’t metabolized in the body

64
Q

_______ accelerates the production of Compound A from Sevoflurane

A

Desiccated soda lime

65
Q

If a 40-year-old patient receives 1% Sevo (0.5 MAC) for 2 hours, what is the MAC - hrs?

A

2hours at 0.5 MAC = 1 MAC hour

66
Q

What are the FDA guidelines surrounding FGF with Sevo?

A

FGF should not be less than 1 L/min for up to 2 MAC hours

For more than 2 MAC hours, FGF should not be lower than 2 L/min

67
Q

Which P450 enzyme is primarily responsible for halogenated anesthetic metabolism in the liver?

A

CYP2E1

68
Q

The concentration effect is also known as:

A

overpressuring

the higher the concentration of anesthetic, the faster its onset of action

69
Q

What causes the concentration effect?

A
  1. The concentratingeffect: Nitrous oxide is WAAAAYYY more soluble in the blood than nitrogen, so more air is moving from the alveolus into the blood, and this causes the alveoli to shrink. Smaller alveoli means decreased FRC means faster rate of rise
  2. Augmented Gas Inflow Effect: Because gas is leaving the alveoli rapidly and reducing alveolar volume, air is sucked down from the upper airways into the alveoli to replace the lost gas. But this really only happens for the first breath or so
70
Q

What is the ventilation effect?

A

In spontaneously breathing patients, as you breathe in anesthetic gases, RR and Vt decrease, which in turn decreases the amount of gas inhaled

minimizes the risk of anesthetic overdose

71
Q

Does the second gas effect have more impact on sevo or iso? Why?

A

Iso

It produces more of an effect on agents that have higher solubility

72
Q

In a R to L shunt, the FA/FI of which agents are most effected?

A

The less soluble it is, the more it’s going to be effected (des is more effected than Iso)

73
Q

In R to L shunt, the rate of rise for inhaled anesthetics will be ______ and the rate of rise for IV anesthetics will be ______

A

decreased

increased

74
Q

List five examples of R to L shunts

A

Tet of Fallot

Eisenmenger’s Syndrome

Foramen Ovale

Tricuspid Atresia

Ebstein’s Anomaly

75
Q

How much more soluble than nitrogen is nitrous oxide?

A

34x

76
Q

What are the blood:gas solubility coefficients for nitrogen and nitrous oxide?

A

Nitrogen 0.014

Nitrous Oxide 0.46

77
Q

Why would it be unwise to give nitrous oxide to a long-term alcoholic?

A

Nitrous oxide causes Vit B12 deficiency

For people who already have some level of B12 deficiency, this can lead to megaloblastic anemia, neuropathy, and decreased DNA synthesis

78
Q

Which is inhibitory and stimulatory:

Opening of potassium channels

Opening of Sodium Channels

A

Opening potassium channels is inhibitory

Opening sodium channels is excitatory

79
Q

In the brain, the most important site of volatile anesthetic action is the:

A

GABA-A Receptor

80
Q

In the spinal cord, the most important site of volatile anesthetic action is:

A

Glycine receptor stimulation

NMDA receptor inhibition

Sodium Channel Inhibition

GABA-A ACTION IS NOT RESPONSIBLE FOR IMMOBILITY

81
Q

Inhaled anesthetics cause immobility at the ______

A

ventral horn of the spinal cord

82
Q

Who do inhaled anesthetics decrease MAP?

A

They decrease the amount of intracellular calcium in vascular smooth mm and cardiac myocytes → vasodilation and myocardial depression

83
Q

What effect do inhaled anesthetics have on an ECG?

A

Prolong QT because they impair potassium movement out of the cell during depolarization

This means the action duration is much longer, because the cell has a hard time repolarizing

Hence, the QT is prolonged

84
Q

Which volatile anesthetic decreases SVR the LEAST?

A

Sevo

85
Q

Coronary vasodilation is greatest with which anesthetic?

A

Iso

Then Des, then Sevo

86
Q

What effect does nitrous have on HR and BP?

A

Increases both because it activates the SNS

87
Q

The halogenated agents are broncho_______

A

dilators

88
Q

Which inhaled anesthetic impairs hypoxic ventilatory response the least?

A

Des

89
Q

Why do inhaled anesthetics impair hypoxic ventilatory drive?

A

We think it’s because when they’re metabolized they produce a reactive oxidative species that impairs the sensory cells of the carotid body

It makes sense, then, that Sevo (which undergoes the most metabolism) causes the most suppression of hypoxic respiratory drive, and Des (which undergoes the least metabolism) causes the least suppression

90
Q

Which anesthetic is ideal for patients with sleep apnea or emphysema?

A

These patients rely on hypoxic ventilatory drive

91
Q

Where are the carotid baroreceptors located?

A

the carotid sinus

92
Q

Where are the carotid chemoreceptors located?

A

The carotid body

93
Q

At what MAC is the response to hypoxia impaired?

A

O.1

BUT this MAC does NOT impair CO2

94
Q

What MAC is required to produce an isoelectric state?

A

1.5-2

95
Q

Motor Evoked Potentials (MEPs) monitor the _________

A

corticospinal tract

96
Q

Somatosensory Evoked Potentials (SSEPs) monitor the integrity of the ______

A

dorsal column

97
Q

The corticospinal tract is supplied by the _____ arteries

A

Anterior spinal

98
Q

The dorsal column is supplied by the ______ arteries

A

posterior spinal

99
Q

With EMPs, what are amplitude and latency?

A
100
Q

the best anesthetic technique to preserve evoked membrane potentials is:

A

TIVA without N2O

NOT KETAMINE

101
Q

What is the maximum MAC you can use if you’re monitoring EMPs?

A

0.5

Anesthesia Pharm (12 decks)

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