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

*Inhaled Anesthetics Part 1 (Exam III) Flashcards

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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.

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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

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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.

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8
Q

Smaller molecules effuse faster dependent on ________.

A

solubility

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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

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18
Q

What does PI mean?

A

Partial pressure of Inspired volatile gas
(or Inspired Pressure)

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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
What is the second gas effect as it relates to anesthesia?
- Uptake of **N₂O accelerates a concurrently administered volatile gas**. ## Footnote S13
26
How does N₂O create the second gas effect?
N₂O hyper-concentrates volatiles to *create a high concentration gradient by* **being super-diffusible**. ## Footnote S13
27
Describe what is being depicted on the graph below.
This is the concentrating effect of N₂O on Halothane. ## Footnote S14
28
What cases would nitrous oxide **not** be utilized in? Why?
- 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). ## Footnote S15
29
What specific cases are bad for the usage of N₂O?
- Ear & eye - Open belly - Lung ## Footnote in lecture
30
What factors affect the magnitude of pressure N₂O would exert on a cavity that it filled?
- Partial pressure of N₂O - Blood flow to the cavity - Duration of N₂O administration ## Footnote S15
31
What would nitrous inhalation in a patient with pneumothorax do?
Expand the pneumothorax ## Footnote S16
32
What could N₂O on an intraocular case do?
- Massively increase retinal artery pressure and cause permanent vision loss. | 1 hour after administering N2O ## Footnote S16
33
Decreased __________ from hyperventilation will decrease cerebral blood flow and limit induction speed.
PaCO₂ ## Footnote S18
34
Dose dependent depressant effects of alveolar ventilation causes a ____ feedback loop
negative ## Footnote S19
35
During spontaneous ventilation as input decreases due to ↓ventilation, volatile anesthesia is redistributed...
From tissue with high concentration (brain) To tissue with low concentration (fat) As brain concentration decreases ventilation increases ## Footnote S19
36
What is the difference between Spontaneous vs Mechanical ventilation?
Patients don't have the ability to equilibrate with mechanic ventilation so we have to alter the mechanical ventilator. | CHECK DICTATION ## Footnote S19
37
What is the definition of solubility for anesthetic gasses?
Ratio of how inhaled gas distribution between two compartments at equilibrium (when partial pressures are equal). ## Footnote S20
38
If the temperature of blood increases then solubility _________.
decreases ## Footnote S20
39
What does a **low blood solubility** mean for induction?
Less gas has to be dissolved = PA → Pa is rapid = **rapid induction**. ## Footnote S20
40
What does a **high blood solubility** mean for induction?
More gas has to be dissolved = PA → Pa is slow = **slow induction**. ## Footnote S20
41
What is being described in the graph below?
How quickly the inspired concentration of a gas equals the alveolar concentration of said gas. ## Footnote S21
42
What volatile gases are intermediately soluble?
- Halothane - Isoflurane ## Footnote S21
43
What is the blood:gas partition coefficient of Halothane?
Halothane = 2.54 : 1 ## Footnote S22
44
What is the blood:gas partition coefficient of Isoflurane?
Isoflurane = 1.46 : 1 ## Footnote S22
45
What volatile gasses are poorly soluble (in order)?
1. Desflurane 2. N₂O 3. Sevoflurane ## Footnote S22
46
What is the blood:gas partition coefficient of Desflurane?
Desflurane = 0.42 : 1 ## Footnote S22
47
What is the blood:gas partition coefficient of N₂O?
Nitrous = 0.46 : 1 ## Footnote S22
48
What is the blood:gas partition coefficient of Sevoflurane?
Sevoflurane = 0.69 : 1 ## Footnote S22
49
What are the blood:gas solubilities of all the gasses we have to know for anesthesia pharm?
## Footnote S22
50
Differentiate between Blood:Gas partition coefficient vs Fat:Blood partition coefficient (accoriding to lecture). What is an anesthetic implication due to the difference?
**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. ## Footnote S22
51
What occurs (in regards to our partial pressure gradients) during emergence from anesthesia?
Concentration gradient reverses. PA ← Pa ← PBrain ## Footnote S24
52
# Emergence What causes rapid washout of Inhaled Anesthetics from brain?
* High cardiac output * Inhaled anesthetics not highly soluble in brain | Check dictation ## Footnote S24
53
What is emergence dependent on and why?
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… ## Footnote S24
54
What helps decrease concentration of volatile anesthetic in PA and PBrain on emergence?
Continued uptake by Muscle/Fat if not already at equilibrium. ## Footnote S24
55
What color coding does Isoflurane have?
Purple ## Footnote S25
56
What color coding does Sevoflurane have?
Yellow ## Footnote S25
57
What color coding does Desflurane have?
Blue ## Footnote S25
58
Which anesthetic would you anticipate as having the quickest recovery? Slowest?
Fastest recovery = Desflurane Slowest recovery = Halothane ## Footnote S26
59
What is 1 MAC?
*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 ## Footnote S27
60
What is 1.3 MAC?
Concentration at 1atm that prevents skeletal muscle movement in response to supramaximal, painful stimulation in 99% of patients. ## Footnote S28
61
What would ED99 be equivalent to in regards to MAC?
ED99 ≈ 1.3 MAC ## Footnote S28
62
What is MACawake?
**0.3 - 0.5 MAC**: partial awakeness and responsiveness. ## Footnote S28
63
What is MACBAR?
**1.7 - 2.0 MAC** Blunts autonomic responses. No SNS response at all, essentially an overdose. ## Footnote S28
64
What factors are standardized MAC values based on?
30 - 55 y/o at 37°C at 1atm | REMEMBER THIS!!!!! ## Footnote S28
65
What is the MAC of N₂O? What does this mean?
N₂O MAC = 104%. Can't be used as sole anesthetic agent. ## Footnote S29
66
What is the MAC of Halothane?
0.75% ## Footnote S29
67
What is the MAC of Isoflurane?
1.17% ## Footnote S29
68
What is the MAC of Desflurane?
6.6 ## Footnote S29
69
What is the MAC of Sevoflurane?
1.8% ## Footnote S29
70
What are the two biggest factors that affect MAC?
- Body temperature - Age ## Footnote S30
71
At what age does MAC peak?
1 y/o ## Footnote S30
72
How much does MAC need decrease as one gets older?
6% per decade. ## Footnote S30
73
What is the formula to determine how much MAC to give your patient?
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 # ## Footnote discussed in lecture; S29
74
What factors will increase MAC?
- Hyperthermia - Excess Pheomelanin (redheads) - Drug-induced ↑ catecholamines - Hypernatremia ## Footnote S31 - MEMORIZE THIS
75
What factors will decrease MAC? *Extensive list*
**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 ## Footnote S32
76
What factors does not change MAC?
* 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 ## Footnote S33 - MEMORIZE THIS
77
Spinal immobility is caused by 3 pathways
* Depress excitatory AMPA and NMDA (glutamate receptors) * Enhance inhibitory glycine receptors * Act on sodium channels | Check ## Footnote S35
78
How does loss of consciousness occur with the use of volatile anesthetics?
- Potentiation of GABAA in the brain. - Potentiation of glycine in the brainstem. ## Footnote S36
79
What is Partial Pressure?
A mixture of gases in a closed container exert a pressure on the walls ## Footnote S38
80
What is Dalton's law?
- The sum of all partial pressures will equal the total pressure. - Ptotal = Pgas1 + Pgas2... ## Footnote S38
81
What is Vapor Pressure
Pressure at which vapor and liquid are at equilibrium ## Footnote S39
82
Which of these two liquids in enclosed containers has the higher vapor pressure?
Liquid B: more evaporative. *Vapor pressure is the pressure at which vapor and liquid are at equilibirum.* ## Footnote S39
83
What is Henry's Law?
The amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid. ## Footnote S40
84
What does Henry's law mean in practice?
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
Heat will _____ vapor pressure.
increase ## Footnote S41
86
Cold temperatures will _____ vapor pressure.
decrease. ## Footnote S41
87
A lower vapor pressure gas is inherently more volatile. T/F ?
False. ↑vapor pressure = ↑volatility ## Footnote S41
88
What is the vapor pressure of Halothane?
243 ## Footnote S41
89
What is the vapor pressure of Enflurane?
175 ## Footnote S41
90
What is the vapor pressure of Isoflurane?
238 torr (mmHg) ## Footnote S41
91
What is the vapor pressure of Desflurane?
669 torr ## Footnote S42
92
What is the vapor pressure of Sevoflurane?
157 torr (or mmHg) ## Footnote S42
93
What do the numbers on the right, bottom area show on the monitor?
The End Tidal and Fraction of Inspiration of a volatile gas (according to lecture)? | S43
94
What is the variable bypass on the anesthetic machine?
A way to dilute/concentrate the amount of anesthetic gas reaching the patient. ## Footnote S44
95
What is the splitting ratio?
How much gas is being sent into the vaporizer ## Footnote S44
96
What is the purpose of the wicks found in the vaporizing chamber below?
The wicks increase gas-liquid interface and **improve vaporization**. ## Footnote S45

KM (Spring 2024) Anesthesia Pharm ** (101 decks)

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