APEX: Inhaled Anesthetics QUIZ Flashcards
1
Q
Which anesthetic is shown in the image below?
A
Sevoflurane
Easy way to remember is to count the Flouride atoms. Sevo has 7
2
Q
Anesthetics are categorized into three groups:
A
- Ethers
- Alkenes
- Gases
3
Q
What gases are considered Ethers?
Think: DIS
A
- Desflurane
- Isoflurane
- Sevoflurane
4
Q
What are some gases that exist in gaseous form?
A
- Nitrous oxide
- Xenon
5
Q
How many fluorine atoms are in the following halogenated gases:
- Halothane
- Isoflurane
- Sevoflurane
- Desflurane
A
- Halothane = 3
- Isoflurane = 5
- Desflurane = 6
- Sevoflurane = 7
6
Q
Does the chlorine atom in Isoflurane increase or decrease potency?
A
Increases potency
7
Q
What is the difference between Desflurane and Isoflurane’s chemical structure?
A
- The substitution of the fluorine atom in desflurane for the chlorine atom in isoflurane
- Leads to significant differences in their pharmacokinetic properties
8
Q
What is the potency of Sevoflurane compared to Desflurane?
A
Sevoflurane is ~ 3 times as potent as Desflurane.
9
Q
What is Vapor Pressure
A
- Is the pressure exerted by a vapor in equilibrium with its liquid or solid phase inside of a closed container
10
Q
What is boiling point?
A
- Is the temperature where matter transitions from a liquid state to a gas state.
- Open container
11
Q
When does boiling occur?
A
- When vapor pressure is equal to atmospheric pressure
12
Q
What does Dalton’s law of partial pressure says?
A
- The total gas pressure in a container is equal to the sum of the partial pressures exerted by each gas.
- P total = P1 + P2 + P3…
13
Q
Vapor pressure is less than?
A
Atmospheric pressure
In relation to Evaporation
14
Q
Boiling requires an open or closed container?
A
Open container
15
Q
↑ atmospheric pressure → ?
A
↑ boiling point
16
Q
↓ atmospheric pressure → ?
A
↓ Boiling point
17
Q
What is Partial Pressure?
A
- The pressure exerted by a vapor in equilibrium with its liquid or solid phase inside of a closed container
18
Q
What does Dalton’s law of Partial Pressures say?
A
- The total gas pressure in a container is equal to the sum of the partial pressure exerted by each gas.
19
Q
How is the depth of Anesthesia determined?
A
- By the partial pressure of an anesthetic gas agent in the brain.
- NOT the volume percent.
20
Q
Is Sevoflurane stable or unstable in hydrated soda lime?
A
Unstable
21
Q
Desflurane and Isoflurane can become unstable in desiccated soda lime and produce:
A
- Carbon monoxide
- Des > Iso
22
Q
What’s Sevo Vapor pressure?
A
157 mm Hg
23
Q
What’s Des vapor pressure?
A
669 mm Hg
24
Q
What’s Iso vapor pressure?
A
238 mmHg
25
What's Nitrous oxide vapor pressure?
38, 770 mmHg
26
What is the Boiling point (degrees C) of the following gases?
1. Des
2. Iso
3. Sevo
4. N2O
## Footnote
**Think: D-I-S order lowest to highest + N2O**
1. **D**es= 22 celcius
2. **I**so = 49 celcius
3. **S**evo = 59 celcius
4. **N**2O = -88 celcius
27
What is the Molecular weight (g) of Sevoflurane?
200 g
28
What is the Molecular weight (g) of Desflurane?
168 g
29
What is the Molecular weight (g) of Isoflurane?
184 g
30
What is the Molecular weight (g) of Nitrous oxide?
44 g
31
Do the following inhaled anesthetic gases require a Preservative?
1. Sevo
2. Des
3. Iso
4. N2O
No
32
Which inhaled anesthetic gases are the only ones stable in hydrated CO2 absorber?
## Footnote
**Think: D-I-N**
1. **D**es
2. **I**so
3. **N**2O
33
Which inhaled anesthetic gases are stables on Dehydrated Co2 absorber?
- Nitrous Oxide only!
34
What is the toxic By-product of Sevoflurane?
Compound A
35
What is the toxic By-product of Desflurane and Isoflurane?
- Carbon monoxide
- Des > Iso
36
In what kind of solvent Will a Polar solute will be more soluble?
- In a Hydrophilic solvent
37
In what kind of solvent Will a **Non-Polar solute will be more soluble**?
- In a Lipophilic solvent
38
What is gas solubility?
- The ability of the anesthetic agent to dissolve into the blood and tissues
39
How is solubility measure?
- The partition coefficient
- Describes the relative solubility of a solute in two different solvents
40
What are the Partition Coefficients of Sevo?
- Blood:gas = 0.65
- Brain:blood = 1.7
- Muscle:blood = 3.1
- Fat:blood = 47.5
- Oil:gas = 47
41
What are the Partition Coefficients of Desflurane?
- Blood:gas = 0.42
- Brain:blood = 1.3
- Muscle:blood = 2.0
- Fat:blood = 27.2
- Oil:gas = 19
42
What are the Partition Coefficients of Isoflurane?
- Blood:gas = 1.46
- Brain:blood = 1.6
- Muscle:blood = 2.9
- Fat:blood = 44.9
- Oil:gas = 91
43
What are the Partition Coefficients of Nitrous Oxide?
- Blood:gas = 0.46
- Brain:blood = 1.1
- Muscle:blood = 1.2
- Fat:blood = 2.3
- Oil:gas = 1.4
44
What does FA stand for?
* **Alveolar Gas Concentration**
* The partial pressure of the anesthetic inside the alveoli
45
What does FI stands for?
* **Inspired Gas Concentration**
* The concentration of the anesthetic exiting the vaporizer
46
The FA/FI Curve of inhalation agents- Recognize it!
47
Factors that influence the rate of anesthetic delivery to the alveoli:
- Setting the vaporizer
- Fresh gas flow
- Time constant of the delivery system
- Anatomic dead space
- Alveolar ventilation
- Functional residual capacity (FRC)
48
Factors that influence the **removal of anesthetic from the Alveoli**:
- Blood:gas solubility
- Partial pressure difference between the alveoli and the blood
- Cardiac output
49
What are the Determinants of Tissue uptake(absorption)?
- Tissue:blood solubility
- Tissue blood flow
- Partial pressure difference between arterial blood and tissue
50
What are the factors that **↑ Wash in**?
- ↑ FGF
- ↑ Alveolar ventilation
- ↓ FRC
- ↓ Time constant
- ↓ anatomic dead space
## Footnote
**Increased FA/FI = Faster onset curve push-up**
51
What are the factors that **↓ Uptake**?
- ↓ solubility
- ↓ Cardiac output
- ↓ Pa-Pv difference
## Footnote
**Increased FA/FI = Faster onset curve Pushed up**
52
What factors lead to **↓ Wash in**?
- ↓ FGF
- ↓ Alveolar filtration
- ↑ FRC
- ↑ Time constant
- ↑ Anatomic dead space
## Footnote
**Decreased FA/FI = Slower Onset Curve Pushed Down**
53
What factors lead to **↑ Uptake**?
* ↑ Solubility
* ↑ Cardiac output
* ↑ Pa-Pv difference
## Footnote
**Decreased FA/FI = Slower Onset Curve Pushed Down**
54
What percentage of body weight is accounted for by the **vessel-rich group**?
10%
55
Tissue uptake depends on:
- Tissue blood flow
- Solubility of the anesthetic in the tissue
- Arterial blood:tissue partial pressure gradient
56
Which organs are included in the Vessel-Rich Group?
- Heart
- Brain
- Kidneys
- Liver
- Endocrine glands
57
What percentage of cardiac output does VRG receive?
75%
58
What is the percentage of body mass of the muscle/skin group?
50%
59
What percentage of cardiac output does the muscle/skin group receives?
20%
60
What is the percentage of Body Mass of the **Vessel-Poor group**?
20%
61
What is the percentage of cardiac output receive by the **Vessel-Poor Group**?
< 1%
62
What is the percentage of cardiac output receive by the **Fat group**?
5%
63
What is the percentage of Body Mass of the **Fat group**?
20%
64
Which organs are included in the **Vessel-Poor Group**?
- Bone
- Tendon
- Cartilage
65
Which organs are included in the Muscle group?
- Skeletal muscle
- Skin
66
Which body group receives most of the anesthetic agent during induction and are the first to equilibrate with FA?
Vessel-Rich Group
67
What is the order of body group from first to last of anesthetic agent uptake?
1. Vassel-Rich Group
2. Muscle Group
3. Fat Group
4. Vessel-Poor Group
68
## Footnote
**Biotransformation THINK: DISH-N**
69
Inhaled anesthetics are eliminated from the body in three ways:
1. Elimination from the alveoli (primary mechanism)
2. Hepatic biotransformation (secondary mechanism)
3. Percutaneous loss ( minimal and not clinical significant)
70
By which system do Halogenated anesthetics undergo Hepatic Biotransformation?
- P450 system
71
What are the **metabolites produced by Desflurane and Isoflurane**?
**Trifluoroacetic Acid**
## Footnote
**Small risk of immune-mediated hepatic dysfunction**
72
What **metabolites** are produces by **Sevoflurane**?
**Free Fluoride Ions**
## Footnote
Theoritical risk of high output kidney failure
73
When expose to Soda Lime, **Sevoflurane generates**:
**Compound A**
## Footnote
Desiccated soda lime accelerates Compound A production.
74
When exposed to Desiccated Soda Lime, **Desflurane and Isoflurane generates**:
**Carbon monoxide**
75
You should remember "The rule of 2's" → (0.02, 0.2, 2, and 20) Additionally, you should notice that halogenated agents spell DISH
76
## Footnote
**Halothane only produces Trioflouroacetic Acid**
77
What percentage of Halothane goes under hepatic biotransformation?
20%
78
What is the metabolic by-product of Halothane metabolism?
- Trifluoroacetic acid (TFA)
79
High concentration of Trifluoroacetic acid (TFA) in the liver leads to:
**Halothane Hepatitis**
## Footnote
Liver is the primary mechanism for immune-mediated hepatic dysfunction (Halothane hepatitis)
80
Desflurane and Isoflurane are metabolized to:
- Inorganic fluoride ions
- Trifluoroacetic acid (TFA)
81
**Sevoflurane** is **NOT** metabolized to TFA, but its biotransformation does result in the liberation of:
**Inorganic Fluoride Ions**
82
83
Renal failure produced by Sevoflurane is characteristically unresponsive to:
Vasopressin
84
Signs of high output Renal failure include:
- Polyuria
- Hypernatremia
- Hyperosmalarity
- ↑ Plasma Creatine
- Inability to concentrate urine
85
Nitrous oxide is not metabolized by the ______
Body
86
What are the FDA's recomendations to prevent Compound A buildup?
- FGF of 1 L/min for up to 2 MAC-hr
- FGF of 2 L/min after 2 MAC-hr
- FGF rates < 1 L/min are not recommended
87
What is MAC-hr?
- Is Minimun alveolar concentration
- Prevents movement in response to a noxious stimulus 50% of subjects (MAC) after 1 hour.
88
Which P450 enzyme is chiefly responsible for halogenated anesthetic metabolism in the liver?
CYP2E1
89
What by-product of halothane metabolism has been implicated in causing halothane hepatitis?
Trifluoroacetic acid (TFA)
90
Which concept BEST explain why the rate of rise of FA/FI is faster for Nitrous Oxide than Desflurane?
Concentration effect
91
What factors alter the speed of anesthetic induction and emergence?
- Concentration effect
- Ventilation effect
92
What are the two components of Concentration effect?
1. Concentrating effect
2. Augmented Gas Inflow effect
93
How many more times is Nitrous Oxide more soluble in the blood than Nitrogen?
~ 34 times
94
The concentration effect only applies to which anesthesia phase?
**Induction**
95
The greater the alveolar ventilation, the ___________ the rate of rise of FA/FI
- the **GREATER** the rate of rise of FA/FI
96
How does the concentration effect affect the rate of rise on the FA/FI curve?
- The **higher the concentration** of inhalation anesthetic delivered to the alveolus the **faster its onset of action**
97
What is the ventilation effect?
- Changes in alveolar ventilation affect the rate of rise of FA/FI
98
What is the definition of **Second Gas Effect**?
* Describes the consequences of the concentration effect when a second gas is co-administered
* Administering one gas during anesthetic induction (N2O) will hasten the onset of a second gas (volatile agent)
## Footnote
**Hasten: Makes the process quicker**
99
What the definition of Diffusion Hypoxia?
- Movement of N2O from the tissue back into alveoli during emergence
100
Identify on the graph below which line of **Iso** is with and without Nitrous oxide.
101
What is the ranking of higher blood:gas solubility of inhaled anesthetics?
Iso > Sevo > Des
102
How many litters of Nitrous oxide can the body gas-containing areas absorb within the first two hours of administration?
Up to 30 L
103
Does the second gas effect have a more meaningful impact on Iso or Sevo? Why?
* It produces a more meaningful **benefit** with **agents of higher blood:gas solubility**
* **Iso > Sevo > Des**
104
What is the best way to mitigate diffusion hypoxia after nitrous oxide is discontinue?
- ↑ FiO2 for 3-5 min after d/c N2O
- It does not have to be 100% though
105
Which volatile agent is affected the MOST by a Right-to-Left cardiac shunt?
**Desflurane (blood:gas 0.42)**
## Footnote
A right-to-left cardiac shunt slows the speed of induction with a volatile agent. It takes longer for FA to equilibrate with FI.
Agents with slow solubility (Desflurane) are affected the most
Agents with high solubility (Isoflurane) are affected the least
106
How does Right-to-left shunt affects the onset of volatile and intravenous anesthetics?
- Slower induction with volatile agents
- Faster induction with an IV agent
107
How does Left-to-Right shunt affects the onset of volatile and intravenous anesthetics?
- No miningful impact on induction with volatile agents
- Slower induction with IV agents
108
What are some examples of Right-to-Left shunts?
- Tetralogy of Fallot
- Foramen ovale
- Eisenmenger's syndrome
- Tricuspid atresia
- Ebstein's anomaly
109
Which volatile agent is affected the **LEAST** by a Right-to-Left cardiac shunt?
**Isoflurane (blood:gas 1.46)**
110
Which anesthetic agent has a blood:gas solubility coefficient of 0.46?
Nitrous oxide
111
**Fluoromethyl 2,2,2-trifluoro-1-(trifluoromethyl) ethyl ether (Sevoflurane)**
112
**Full fluorination** of an anesthetic agent will **MOST likely reduce**:
- ↓ Potency
- ↓ Metabolism
113
Which anesthetic agents bear the closest chemical resemblance?
- Desflurane
- Isoflurane
114
The FA/FI curve of which anesthetic agent is **MOST significantly impacted by the concentration effect**?
**Nitrous oxide**
## Footnote
Higher the concentration of inhalation anesthetic delivered to the alveolus (FA), the faster its onset of action (this is also called over pressuring).
115
Which anesthetic agent undergoes the **GREATEST degree of elimination from the lungs**?
**Desflurane**
116
Which physiochemical reaction occurs when a liquid's vapor pressure equals atmospheric pressure?
Boiling
117
In which cells would the concentration of Sevoflurane be expected to rise the **FASTEST** during anesthetic induction?
Hepatocytes
118
Which factors have the MOST significant impact on anesthetic uptake into the blood?
1. Blood:gas solubility
2. Cardiac output
3. Partial pressure difference between the alveolar gas and mixed venous gas
119
The blood:gas partition coefficient MOST closely correlates with:
Speed of emergence
120
What is determined by the Partial Pressure (PP)?
Depth of Anesthesia
121
Which anesthetic gases are not affected by elevation?
- Sevoflurane
- Isoflurane
This is because the conventional variable bypass vaporizer automatically compensates for the elevation change.
122
Which Anesthetic gas uses the Tec 6 Vaporizer?
Desflurane
123
The Fa/FI curve allow us to predict :
The speed of induction
124
Low solubility =
Faster Onset
125
High solubility =
Slower Onset
126
What conditions increase FA/FI?
For FA/FI to increase, there must be:
* ↑ Wash in
* ↓ Uptake
127
What conditions **decrease FA/FI**?
For FA/FI to decrease, **there must be a reduced Wash in and/or increase uptake**
128
What is the ranking of potency for inhaled anesthetics from most to least (oil:gas)?
Iso > Sevo > Des
129
How does the addition of Chlorine atom affect Isoflurane's PK/PD profile
- ↑ Potency
- ↑ Blood:gas solubility
130
Carbon dioxide absorbent, as well as the liver, can transform volatile anesthetic into:
Toxic compounds
131
What is Gas Stability?
- Ability to resist to breakdown or metabolism
132
What are the four key physiochemical concepts of inhaled anesthetics?
1. Vapor pressure
2. Boiling point
3. Partial Pressure
4. Stability
133
What is Evaporation?
- Compound transition from its liquid state to a gaseous state.
- Below its boiling point.
## Footnote
**Vapor pressure is < atmospheric pressure**
134
An Anesthetic gas with LOW blood:gas solubility is less or more likely to be taken up into the blood?
**Is LESS likely to be taken up into the blood.**
135
An Anesthetic gas with **HIGH blood:gas solubility** is **less or more** likely to be taken up into the blood?
**Is MORE likely to be taken up into the blood**
136
Nitrous Oxide
137
The amount of anesthetic inside the Alveoli (FA) is a balance between:
Input and uptake into the blood
## Footnote
**Input: the setting in the vaporizer**
138
When administering a volatile anesthetic, we produce a state of anesthesia by:
- Building up partial pressure of anesthetic agent **inside the patient's brain and spinal cord** .
139
What is the surrogate to measure an anesthetic in the brain?
**Alveolar Partial Pressure (FA)**
## Footnote
**Alveolar partial pressure ~ Blood partial pressure ~ Brain partial pressure**
140
This term, creates a concentration gradient that pushes the anesthetic agent from the vaporizer towards the alveoli:
FI (Inspired Gas Concentration)
141
This term describes the anesthetic washes into the alveoli and establishes a partial pressure:
FA ( Alveolar Gas concentration)
142
This term describes the build up of anesthetic partial pressure inside the alveoli is being opposed by continues uptake of the agent into the blood:
Uptake
143
Nitrous oxide quickly diffuses to gas containing areas in the body, such as:
* GI tract
* Middle ear
144
What's the potency of Isoflurane compared to Sevoflurane?
- Isoflurane is **twice** as potent as Sevoflurane.
## Footnote
**Isoflurane is 5 times as potent as Desflurane**
145
How does Cardiac output influence the removal of inhaled anesthetic from the alveoli?
- ↑ CO → ↑ Uptake → ↓ FA (slower induction)
- ↓ CO → ↓ Uptake → ↑ FA (faster induction)
146
How does Cardiac Output affect the rate of induction of the IV agent?
- ↑ CO → Faster delivery to the brain (faster induction)
- ↓ CO → Slower delivery to the brain ( slower induction)
147
How does increased cardiac output affect the speed of an inhalation induction?
Induction is prolonged
148
Which electrolyte disorders affect MAC?
- MAC increase: ↑ Na+
- MAC decrease: ↓ Na+, ↑ Li+
- MAC is Unchanged by K+
149
During which procedures is SF6 (Sulfur Hexafluoride) placed over the retina?
- Retinal reattachment
- Vitrectomy
- Macular hole repair
150
How long is N2O avoided if the SF6(sulfur hexafluoride) bubble is placed?
- Avoid N2O 15 min before SF6 is placed
- Avoid N2O 7-10 days after SF6 is placed
N2O can expand SF6 bubble compromise retinal perfusion and cause permanent blindness.
151
How long is N20 avoided if a Pefluoropropane (CF38) bubble is placed?
- Avoid N2O 30 days if Perfluoropropane (CF38) after the bubble is placed.
152
Which anesthetic is Methyl isopropyl ether?
Sevoflurane
153
Which anesthetic is Methyl ethyl ether?
- Desflurane
- Isoflurane
154
How does endobronchial intubation affect the speed of an inhalation induction?
Induction is prolonged
