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Spr24 Pharm II > Inhaled Anesthetics Part 1 (Exam III) > Flashcards

Inhaled Anesthetics Part 1 (Exam III) Flashcards

1
Q

What is Boyle’s Law?
What application of this was mentioned in class?

A
  • At Constant temperature, Pressure and Volume of gas are inversely proportional
  • Bellows contract thus increasing circuit pressure → gasses flow from high pressure circuit to low pressure lungs.
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2
Q

What is Fick’s Diffusion Law (as is pertinent to inhaled anesthetics)?

A

Once air molecules enter alveoli, they move around randomly and begin to diffuse into the pulmonary capillaries.

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3
Q

What factors is diffusion dependent on?

A
  • Partial pressure gradient of the gas
  • Solubility of the gas
  • Thickness of the membrane
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4
Q

What is Graham’s Law of Effusion?

A

Process by which molecules diffuse through pores and channels without colliding. (smaller molecules effuse faster, depends on solubility)

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5
Q

Smaller molecules effuse faster dependent on ________.

A

solubility

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6
Q

Which diffuses faster CO₂ or O₂ ? Why?

A

CO₂ is 20x more diffusible due to solubility despite O₂ weighing less.

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7
Q

If PBrain is greater than PA then what we expect to be occurring?

A

This means the concentration gradient is moving towards the alveoli away from the brain.

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8
Q

What does the following equation mean?

PA ⇌ Pa ⇌ PBrain

A

This is comparing the partial pressure of volatile gas in the alveoli to the arterial blood to the brain.

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9
Q

What input factors affect the diffusion of volatile gas from the anesthetic machine to the alveoli?

A
  • Inspired partial pressure
  • Alveolar ventilation
  • Anesthetic system re-breathing
  • FRC
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10
Q

Which factors affect the uptake of anesthetic gas from the alveoli to the blood?

A
  • Blood:gas partition coefficient
  • Cardiac output
  • A-V pressure difference
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11
Q

How would a low cardiac output affect the diffusion of anesthetic gas from the alveoli to the pulmonary capillary blood?

A

↓CO = more time to diffuse across the alveolus

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12
Q

What factors affect the uptake of anesthetic gas from the arterial blood to the brain?

A
  • Blood:Brain partition coefficient
  • Cerebral blood flow
  • A-V partial pressure difference.
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13
Q

Gas goes from a ____ gradient to a ____ gradient in order to reach a steady state.

A

high; low

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14
Q

What is the concentration effect?

A

Higher the PI ⇒ PA reaches PI quicker

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15
Q

What does FE/FI mean?

A

FE/FI is the ratio of expired gas to inspired gas.

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16
Q

What concept is this chart conveying?

A

Concentration Effect: essentially, ↑concentration inspired gas = quicker rate of ↑PA

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17
Q

What is over-pressurization?

A
  • A large increase in PI to offset slow induction from highly soluble volatiles.
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18
Q

What would sustained delivery of over-pressurization result in?

A

Overdose

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19
Q

What gas does the second gas effect always apply to?

A

N₂O (nitrous oxide)

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20
Q

What is the second gas effect as it relates to anesthesia?

A
  • Uptake of N₂O accelerates a concurrently administered volatile gas.
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21
Q

How does N₂O create the second gas effect?

A

Rapid N₂O uptake hyper-concentrates second gas to create a high concentration gradient and increase uptake of second gas

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22
Q

Describe what is being depicted on the graph below.

A
  • This is the second gas effect of N₂O on halothane. Leads to quicker increase in halothane alveolar concentrations.
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23
Q

What cases would nitrous oxide not be utilized in?
Why?

A
  • Cases with an air-filled cavity
  • N₂O will diffuse into the cavity and fill it. (extent of damage dependent on the compliance of the cavity).
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24
Q

What specific cases are bad for the usage of N₂O?

A
  • Ear & eye
  • Open belly (stomach, intestines)
  • Lung
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25
Q

What factors affect the degree of pressure N₂O would exert on a cavity that it filled?

A
  • Partial pressure of N₂O
  • Blood flow to the cavity
  • Duration of N₂O administration
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26
Q

What would nitrous inhalation in a patient with pneumothorax do?

A

Expand the pneumothorax

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27
Q

What could N₂O on an intraocular case do?

A
  • Massively increase retinal artery pressure and cause permanent vision loss.
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28
Q

Decreased ______ from hyperventilation will decrease cerebral blood flow and limit induction speed.

A

PaCO₂

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29
Q

Describe the negative feedback cycle of volatile depressant effects

A

↑RR ⇒ quicker to brain ⇒ depressant effects ⇒ ↓RR ⇒ slower to brain ⇒ brain wakes up ⇒ ↑RR ⇒ REPEAT

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30
Q

What is the definition of solubility for anesthetic gasses?

A

Ratio of how inhaled gas distribute between two compartments at equilibrium (when partial pressures are equal).

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31
Q

If the temperature of blood increases then solubility ______.

A

decreases

hyperthermia ⇒ ↓Solubility

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32
Q

What does a low blood solubility mean for induction?

A

Less gas has to be dissolved = PA/Pa is rapid = rapid induction.

33
Q

What does a high blood solubility mean for induction?

A

More gas has to be dissolved = PA/Pa is slow = slow induction.

34
Q

What is being described in the graph below?

A

How quickly the inspired concentration of a gas equals the alveolar concentration, based on the solubility of the gas.

35
Q

What volatile gasses are intermediately soluble?

A
  • Halothane
  • Enflurane
  • Isoflurane
36
Q

What is the blood:gas partition coefficient of halothane?

A

Halothane = 2.54

37
Q

What is the blood:gas partition coefficient of Isoflurane?

A

Isoflurane = 1.46

38
Q

What volatile gasses are poorly soluble?

A
  • N₂O
  • Desflurane
  • Sevoflurane
  • Xenon
39
Q

What is the blood:gas partition coefficient of N₂O?

A

Nitrous = 0.46

40
Q

What is the blood:gas partition coefficient of Desflurane?

A

Desflurane = 0.42

41
Q

What is the blood:gas partition coefficient of Sevoflurane?

A

Sevoflurane = 0.69

42
Q

What occurs (in regards to our partial pressure gradients) during emergence from anesthesia?

A

Concentration gradient reverses.

PA ← Pa ← PBrain

43
Q

What helps decrease concentration of volatile anesthetic in PA and PBrain on emergence?

A

Continued uptake by Muscle/Fat if not already at equilibrium.

44
Q

What color coding does isoflurane have?

45
Q

What color coding does sevoflurane have?

46
Q

What color coding does desflurane have?

47
Q

Which volatile anesthetic would you anticipate as having the quickest recovery (in conjunction with MAC hours)?
Slowest?

A

Fastest recovery = desflurane
Slowest recovery = halothane

48
Q

What is 1 MAC?

A

Concentration at 1atm that prevents skeletal muscle movement in response to surgical stimulation in 50% of patients.

49
Q

Concentration at 1atm that prevents skeletal muscle movement in response to surgical stimulation in 99% of patients.

50
Q

What would ED99 be equivalent to in regards to MAC?

A

ED99 = 1.3 MAC

51
Q

What is MACawake?

A

0.3 - 0.5 MAC: partial awakeness and responsiveness.

52
Q

What is MACBAR?

A

1.7 - 2.0 MAC: Blunts autonomic responses. No SNS response at all, essentially an overdose.

53
Q

What patient are standardized MAC values based on?

A

30 - 55 y/o at 37°C at 1atm

54
Q

What is the MAC of N₂O?
What does this mean?

A

N₂O MAC = 104%. Can’t be used as sole anesthetic agent. (MAC can’t be reached without hyperbaric pressures)

55
Q

What is the MAC of Halothane?

56
Q

What is the MAC of Isoflurane?

57
Q

What is the MAC of Desflurane?

58
Q

What is the MAC of Sevoflurane?

59
Q

What are the two biggest factors that affect MAC?

A
  • Body temperature
  • Age
60
Q

At what age does MAC need peak?

61
Q

How much does MAC need decrease as one gets older?
Younger?

A

6% per decade.

↓% for older
↑% for younger

62
Q

What factors will increase MAC?

A
  • Hyperthermia
  • Excess Pheomelanin (redheads)
  • Drug-induced ↑ catecholamines
  • Hypernatremia
63
Q

What factors will decrease MAC?

Extensive list(11)

A

Essentially anything that slows metabolism

  • Hypothermia
  • Pre-op meds
  • Intra-op opioids
  • ⍺2 agonists (Dex, clonidine)
  • Acute EtOH
  • Pregnancy or Early post-partum
  • Lidocaine
  • PaO₂ < 38 mmHg
  • Mean BP < 40mmHg
  • Cardiac Bypass
  • Hyponatremia
64
Q

How does loss of consciousness occur with the use of volatile anesthetics?

A
  • Potentiation of GABA in the brain.
  • Potentiation of glycine in the brainstem.
65
Q

Which of these two liquids in enclosed containers has the higher vapor pressure?

A

Liquid B: more evaporative.

Vapor pressure is the pressure at which vapor and liquid are at equilibirum.

66
Q

What is Dalton’s law?

A
  • The sum of all partial pressures will equal the total pressure.
  • Ptotal = Pgas1 + Pgas2…
67
Q

What is Henry’s Law?

A

The amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid.

68
Q

What does Henry’s law mean in practice?

A

Henry’s Law is pertinent to overpressurization.

If partial pressure of a volatile doubles, then double the molecules will interact with Pa from the alveoli.

69
Q

Heat will _____ vapor pressure.

70
Q

Cold temperatures will _____ vapor pressure.

71
Q

A lower vapor pressure gas is inherently more volatile. T/F ?

A

False. ↑vapor pressure = ↑volatility

72
Q

What is the vapor pressure of halothane?

73
Q

What is the vapor pressure of Isoflurane?

A

238 torr (mmHg)

74
Q

What is the vapor pressure of Desflurane?

75
Q

What is the vapor pressure of Sevoflurane?

A

157 torr (or mmHg)

76
Q

What is the variable bypass on the anesthetic machine?

A

A way to dilute/concentrate the amount of anesthetic gas reaching the patient.

77
Q

What is the splitting ratio?

A

How much gas is being sent into the vaporizer

78
Q

What is the purpose of the wicks found in the vaporizing chamber below?

A

The wicks increase gas-liquid interface and improve vaporization.

79
Q

How does duration of anesthesia affect MAC?

A

It doesn’t change MAC

Spr24 Pharm II (32 decks)

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