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KM (Spring 2024) COPY of Anesthesia Pharm (Spring 2023) > *Inhaled Anesthetics Part 1 (Exam III) > Flashcards

*Inhaled Anesthetics Part 1 (Exam III) Flashcards

1
Q

What is the pharmacokinetics of Inhaled Anesthetics and the 3 components?

A

Uptake from alveoli into pulmonary capillary blood

  1. Distribution
  2. Metabolism
  3. Elimination via lungs

S3

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2
Q

What influences the pharmacokinetics of Inhaled Anesthetics?

A
  • ↓ lean body mass
  • ↑ fat
  • ↑ Vd for drugs (especially for more fat soluble)
  • ↓ clearance if pulmonary exchange is impaired
  • ↑ time constraints due to lower cardiac output

S3

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3
Q

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

A
  • Pressure and Volume of gas are inversely proportional (at a constant temperature)
  • Bellows contract thus increasing circuit pressure → gasses flow from high pressure circuit to low pressure lungs.

S4

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4
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.

S5

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5
Q

What factors is diffusion dependent on?

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

S5

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6
Q

Which patients have problems with diffusion (according to Dr. Kane)?

A

Pediatrics born with thicker surfaces or distance

S5

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7
Q

What is Graham’s Law of Effusion?

A

Process by which molecules diffuse through pores and channels without colliding.

S6

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8
Q

Smaller molecules effuse faster dependent on ________.

A

solubility

S6

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9
Q

Which diffuses faster CO₂ or O₂ ? Why?
Which would you expect to diffuse faster?

A

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

CO2 mol wt 44g ; O2 mol wt 32g

S6

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10
Q

When PA equals ___________, then the inhaled gas concentration equals the exhaled gas concentration and the patient is unconscious.

A

PBrain

S7

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11
Q

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

A

The patient should be waking up.
This means the exhaled gas is greater than the inhaled gas and the concentration gradient is moving towards the alveoli away from the brain.

S7

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12
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.

S7

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13
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

S8

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14
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

S8

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15
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

S8

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16
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.

S8

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17
Q

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

A

high; low

S8

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18
Q

What does PI mean?

A

Partial pressure of Inspired volatile gas
(or Inspired Pressure)

S10

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19
Q

How can gas be “forced” to the brain quicker?

A

By increasing PI.
This creates a higher gradient for the gas to flow from PA → Pa → PBrain

S10

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20
Q

What does FE/FI mean?

A

FE/FI is the ratio of expired gas to inspired gas
(Fraction of Inspired gas)

S11

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21
Q

What concept is this chart conveying?

A

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

S11

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22
Q

What is over-pressurization?

A

A large increase in PI so as to force gas from PA → Pa → PBrain much faster.

S12

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23
Q

What would sustained delivery of
over-pressurization result in?

A

Overdose

S12

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24
Q

What gas does the second gas effect always apply to?

A

N₂O (nitrous oxide)

S13

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25
Q

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

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

S13

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26
Q

How does N₂O create the second gas effect?

A

N₂O hyper-concentrates volatiles to create a high concentration gradient by being super-diffusible.

S13

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27
Q

Describe what is being depicted on the graph below.

A

This is the concentrating effect of N₂O on Halothane.

S14

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28
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).

S15

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29
Q

What specific cases are bad for the usage of N₂O?

A
  • Ear & eye
  • Open belly
  • Lung

in lecture

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30
Q

What factors affect the magnitude 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

S15

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31
Q

What would nitrous inhalation in a patient with pneumothorax do?

A

Expand the pneumothorax

S16

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32
Q

What could N₂O on an intraocular case do?

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

1 hour after administering N2O

S16

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33
Q

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

A

PaCO₂

S18

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34
Q

Dose dependent depressant effects of alveolar ventilation causes a ____ feedback loop

A

negative

S19

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35
Q

During spontaneous ventilation as input decreases due to ↓ventilation, volatile anesthesia is redistributed…

A

From tissue with high concentration (brain)
To tissue with low concentration (fat)
As brain concentration decreases ventilation increases

S19

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36
Q

What is the difference between Spontaneous vs Mechanical ventilation?

A

Patients don’t have the ability to equilibrate with mechanic ventilation so we have to alter the mechanical ventilator.

CHECK DICTATION

S19

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37
Q

What is the definition of solubility for anesthetic gasses?

A

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

S20

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38
Q

If the temperature of blood increases then solubility _________.

A

decreases

S20

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39
Q

What does a low blood solubility mean for induction?

A

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

S20

40
Q

What does a high blood solubility mean for induction?

A

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

S20

41
Q

What is being described in the graph below?

A

How quickly the inspired concentration of a gas equals the alveolar concentration of said gas.

S21

42
Q

What volatile gases are intermediately soluble?

A
  • Halothane
  • Isoflurane

S21

43
Q

What is the blood:gas partition coefficient of Halothane?

A

Halothane = 2.54 : 1

S22

44
Q

What is the blood:gas partition coefficient of Isoflurane?

A

Isoflurane = 1.46 : 1

S22

45
Q

What volatile gasses are poorly soluble (in order)?

A
  1. Desflurane
  2. N₂O
  3. Sevoflurane

S22

46
Q

What is the blood:gas partition coefficient of Desflurane?

A

Desflurane = 0.42 : 1

S22

47
Q

What is the blood:gas partition coefficient of N₂O?

A

Nitrous = 0.46 : 1

S22

48
Q

What is the blood:gas partition coefficient of Sevoflurane?

A

Sevoflurane = 0.69 : 1

S22

49
Q

What are the blood:gas solubilities of all the gasses we have to know for anesthesia pharm?

A

S22

50
Q

Differentiate between Blood:Gas partition coefficient vs Fat:Blood partition coefficient (accoriding to lecture).
What is an anesthetic implication due to the difference?

A

Blood:Gas Coefficient = affects going to sleep
Fat: Blood Coefficient = affects waking up

You can do any combination of gases based on solubility coefficient and comorbidity.

S22

51
Q

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

A

Concentration gradient reverses.

PA ← Pa ← PBrain

S24

52
Q

Emergence

What causes rapid washout of Inhaled Anesthetics from brain?

A
  • High cardiac output
  • Inhaled anesthetics not highly soluble in brain

Check dictation

S24

53
Q

What is emergence dependent on and why?

A

Length of anesthetic
due to:
* PI is zero (inhaled agent is turned off)
* Muscle/fat maybe not at equilibrium
* Muscle/fat continue to take up anesthetic (helps decrease PA and PBr)
-Remember VRG…

S24

54
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.

S24

55
Q

What color coding does Isoflurane have?

A

Purple

S25

56
Q

What color coding does Sevoflurane have?

A

Yellow

S25

57
Q

What color coding does Desflurane have?

A

Blue

S25

58
Q

Which anesthetic would you anticipate as having the quickest recovery?
Slowest?

A

Fastest recovery = Desflurane
Slowest recovery = Halothane

S26

59
Q

What is 1 MAC?

A

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

If I cut you, ur not gon’ move in 50% of the patients;
enough for others

S27

60
Q

What is 1.3 MAC?

A

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

S28

61
Q

What would ED99 be equivalent to in regards to MAC?

A

ED99 ≈ 1.3 MAC

S28

62
Q

What is MACawake?

A

0.3 - 0.5 MAC: partial awakeness and responsiveness.

S28

63
Q

What is MACBAR?

A

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

S28

64
Q

What factors are standardized MAC values based on?

A

30 - 55 y/o at 37°C at 1atm

REMEMBER THIS!!!!!

S28

65
Q

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

A

N₂O MAC = 104%.
Can’t be used as sole anesthetic agent.

S29

66
Q

What is the MAC of Halothane?

A

0.75%

S29

67
Q

What is the MAC of Isoflurane?

A

1.17%

S29

68
Q

What is the MAC of Desflurane?

A

6.6

S29

69
Q

What is the MAC of Sevoflurane?

A

1.8%

S29

70
Q

What are the two biggest factors that affect MAC?

A
  • Body temperature
  • Age

S30

71
Q

At what age does MAC peak?

A

1 y/o

S30

72
Q

How much does MAC need decrease as one gets older?

A

6% per decade.

S30

73
Q

What is the formula to determine how much MAC to give your patient?

A

1.3 x MAC % of the Inhaled Agent

If pt. > 55 y/o multiple # with 6% then subtract new number with OG #

If pt. < 30 y/o multiple # with 6% then add new number with OG #

discussed in lecture; S29

74
Q

What factors will increase MAC?

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

S31 - MEMORIZE THIS

75
Q

What factors will decrease MAC?

Extensive list

A

Essentially anything that slows metabolism

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

S32

76
Q

What factors does not change MAC?

A
  • Chronic alcohol abuse
  • Gender
  • Duration of anesthesia
  • PaCO2 15-95 mm Hg
  • PaO2 > 38 mm Hg
  • Blood pressure > 40 mm Hg
  • Hyper/hypokalemia
  • Thyroid gland dysfunction

S33 - MEMORIZE THIS

77
Q

Spinal immobility is caused by 3 pathways

A
  • Depress excitatory AMPA and NMDA (glutamate receptors)
  • Enhance inhibitory glycine receptors
  • Act on sodium channels

Check

S35

78
Q

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

A
  • Potentiation of GABAA in the brain.
  • Potentiation of glycine in the brainstem.

S36

79
Q

What is Partial Pressure?

A

A mixture of gases in a closed container exert a pressure on the walls

S38

80
Q

What is Dalton’s law?

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

S38

81
Q

What is Vapor Pressure

A

Pressure at which vapor and liquid are at equilibrium

S39

82
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.

S39

83
Q

What is Henry’s Law?

A

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

S40

84
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.

85
Q

Heat will _____ vapor pressure.

A

increase

S41

86
Q

Cold temperatures will _____ vapor pressure.

A

decrease.

S41

87
Q

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

A

False. ↑vapor pressure = ↑volatility

S41

88
Q

What is the vapor pressure of Halothane?

A

243

S41

89
Q

What is the vapor pressure of Enflurane?

A

175

S41

90
Q

What is the vapor pressure of Isoflurane?

A

238 torr (mmHg)

S41

91
Q

What is the vapor pressure of Desflurane?

A

669 torr

S42

92
Q

What is the vapor pressure of Sevoflurane?

A

157 torr (or mmHg)

S42

93
Q

What do the numbers on the right, bottom area show on the monitor?

A

The End Tidal and Fraction of Inspiration of a volatile gas (according to lecture)?

S43

94
Q

What is the variable bypass on the anesthetic machine?

A

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

S44

95
Q

What is the splitting ratio?

A

How much gas is being sent into the vaporizer

S44

96
Q

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

A

The wicks increase gas-liquid interface and improve vaporization.

S45

KM (Spring 2024) COPY of Anesthesia Pharm (Spring 2023) (103 decks)

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