APEX: Inhaled Anesthetics QUIZ Flashcards
Which anesthetic is shown in the image below?
Sevoflurane
Easy way to remember is to count the Flouride atoms. Sevo has 7
Anesthetics are categorized into three groups:
- Ethers
- Alkenes
- Gases
What gases are considered Ethers?
Think: DIS
- Desflurane
- Isoflurane
- Sevoflurane
What are some gases that exist in gaseous form?
- Nitrous oxide
- Xenon
How many fluorine atoms are in the following halogenated gases:
- Halothane
- Isoflurane
- Sevoflurane
- Desflurane
- Halothane = 3
- Isoflurane = 5
- Desflurane = 6
- Sevoflurane = 7
Does the chlorine atom in Isoflurane increase or decrease potency?
Increases potency
What is the difference between Desflurane and Isoflurane’s chemical structure?
- The substitution of the fluorine atom in desflurane for the chlorine atom in isoflurane
- Leads to significant differences in their pharmacokinetic properties
What is the potency of Sevoflurane compared to Desflurane?
Sevoflurane is ~ 3 times as potent as Desflurane.
What is Vapor Pressure
- Is the pressure exerted by a vapor in equilibrium with its liquid or solid phase inside of a closed container
What is boiling point?
- Is the temperature where matter transitions from a liquid state to a gas state.
- Open container
When does boiling occur?
- When vapor pressure is equal to atmospheric pressure
What does Dalton’s law of partial pressure says?
- 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…
Vapor pressure is less than?
Atmospheric pressure
In relation to Evaporation
Boiling requires an open or closed container?
Open container
↑ atmospheric pressure → ?
↑ boiling point
↓ atmospheric pressure → ?
↓ Boiling point
What is Partial Pressure?
- The pressure exerted by a vapor in equilibrium with its liquid or solid phase inside of a closed container
What does Dalton’s law of Partial Pressures say?
- The total gas pressure in a container is equal to the sum of the partial pressure exerted by each gas.
How is the depth of Anesthesia determined?
- By the partial pressure of an anesthetic gas agent in the brain.
- NOT the volume percent.
Is Sevoflurane stable or unstable in hydrated soda lime?
Unstable
Desflurane and Isoflurane can become unstable in desiccated soda lime and produce:
- Carbon monoxide
- Des > Iso
What’s Sevo Vapor pressure?
157 mm Hg
What’s Des vapor pressure?
669 mm Hg
What’s Iso vapor pressure?
238 mmHg
What’s Nitrous oxide vapor pressure?
38, 770 mmHg
What is the Boiling point (degrees C) of the following gases?
- Des
- Iso
- Sevo
- N2O
Think: D-I-S order lowest to highest + N2O
- Des= 22 celcius
- Iso = 49 celcius
- Sevo = 59 celcius
- N2O = -88 celcius
What is the Molecular weight (g) of Sevoflurane?
200 g
What is the Molecular weight (g) of Desflurane?
168 g
What is the Molecular weight (g) of Isoflurane?
184 g
What is the Molecular weight (g) of Nitrous oxide?
44 g
Do the following inhaled anesthetic gases require a Preservative?
- Sevo
- Des
- Iso
- N2O
No
Which inhaled anesthetic gases are the only ones stable in hydrated CO2 absorber?
Think: D-I-N
- Des
- Iso
- N2O
Which inhaled anesthetic gases are stables on Dehydrated Co2 absorber?
- Nitrous Oxide only!
What is the toxic By-product of Sevoflurane?
Compound A
What is the toxic By-product of Desflurane and Isoflurane?
- Carbon monoxide
- Des > Iso
In what kind of solvent Will a Polar solute will be more soluble?
- In a Hydrophilic solvent
In what kind of solvent Will a Non-Polar solute will be more soluble?
- In a Lipophilic solvent
What is gas solubility?
- The ability of the anesthetic agent to dissolve into the blood and tissues
How is solubility measure?
- The partition coefficient
- Describes the relative solubility of a solute in two different solvents
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
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
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
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
What does FA stand for?
- Alveolar Gas Concentration
- The partial pressure of the anesthetic inside the alveoli
What does FI stands for?
- Inspired Gas Concentration
- The concentration of the anesthetic exiting the vaporizer
The FA/FI Curve of inhalation agents- Recognize it!
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)
Factors that influence the removal of anesthetic from the Alveoli:
- Blood:gas solubility
- Partial pressure difference between the alveoli and the blood
- Cardiac output
What are the Determinants of Tissue uptake(absorption)?
- Tissue:blood solubility
- Tissue blood flow
- Partial pressure difference between arterial blood and tissue
What are the factors that ↑ Wash in?
- ↑ FGF
- ↑ Alveolar ventilation
- ↓ FRC
- ↓ Time constant
- ↓ anatomic dead space
Increased FA/FI = Faster onset curve push-up
What are the factors that ↓ Uptake?
- ↓ solubility
- ↓ Cardiac output
- ↓ Pa-Pv difference
Increased FA/FI = Faster onset curve Pushed up
What factors lead to ↓ Wash in?
- ↓ FGF
- ↓ Alveolar filtration
- ↑ FRC
- ↑ Time constant
- ↑ Anatomic dead space
Decreased FA/FI = Slower Onset Curve Pushed Down
What factors lead to ↑ Uptake?
- ↑ Solubility
- ↑ Cardiac output
- ↑ Pa-Pv difference
Decreased FA/FI = Slower Onset Curve Pushed Down
What percentage of body weight is accounted for by the vessel-rich group?
10%
Tissue uptake depends on:
- Tissue blood flow
- Solubility of the anesthetic in the tissue
- Arterial blood:tissue partial pressure gradient
Which organs are included in the Vessel-Rich Group?
- Heart
- Brain
- Kidneys
- Liver
- Endocrine glands
What percentage of cardiac output does VRG receive?
75%
What is the percentage of body mass of the muscle/skin group?
50%
What percentage of cardiac output does the muscle/skin group receives?
20%
What is the percentage of Body Mass of the Vessel-Poor group?
20%
What is the percentage of cardiac output receive by the Vessel-Poor Group?
< 1%