Inhalation Anesthetics Flashcards
Which anesthetic gases are ethers?
Des, Iso, Sevo, enflurane, Methoxyflurane, Ether
Which anesthetic gases are alkanes?
halothane and chloroform
Which anesthetic gases are simply gases?
N2O, cyclopropane, and xenon
Name that gas
Describe the structure of Iso.
5 fluorine atoms and 1 chlorine atom
Describe the structure of Des.
6 fluorine atoms
Describe the structure of Sevo.
7 fluorine atoms (sevo seven)
Which anesthetic gases have chiral carbons?
Des and Iso
How does the chlorine atom affect Iso?
increases potency, blood and tissue solubility
Name that compound!
What is the difference in the chemical structure of iso and Des?
the chlorine atom is replaced with a flourine atom
What is the full fluorination of desflurane do?
decrease potency which increases MAC
increases vapor pressure
decreased metabolism
How does fluorination affect the physical characteristics of halogenated agents?
decreases potency
What anesthetic agents contains Bromine (Br)?
halothane
What is vapor pressure?
Pressure exerted by a vapor in equilibrium with its liquid or solid phase inside of a closed container
Vapor pressure is directly related to ____.
temperature
Will water boil at a higher or lower temperature at high altitude?
lower temperature due to reduced atmospheric pressure
What is partial pressure?
the fractional amount of pressure that a single gas exerts with a gas mixture
What law states that total gas pressure is equal to the sum of partial pressures exerted by each individual gas?
Dalton
What determines the depth of anesthesia?
the partial pressure of the anesthetic gas in the brain, not what you set the vaporizer to.
At elevation like Denver, is your delivered Volume % set on the vaporizer dial, higher or lower due to the altitude?
Lower, leading to underdosing
How do you calculate partial pressure of a particular gas?
Vol% x total gas pressure
What is the partial pressure of 6% Des at sea level?
What is the partial pressure of 6% Des at 620 atm?
- 06 x 760 = 45.6 mmHg
0. 06 x 620 = 37.2 mmHg
What are the vaporizer pressure of: Sevo Des Iso N2O
Sevo: 157
Des: 669
Iso: 238
N2O: 38,770
What is the boiling point of: Sevo: Des: Iso: N2O:
Sevo: 59
Des: 22
Iso: 49
N2O: 88
What is the molecular weight of: Sevo: Des: Iso: N2O:
Sevo: 200
Des: 168
Iso: 184
N2O: 44
What is the preservative of: Sevo: Des: Iso: N2O:
They dont have preservatives
What gases are stable in hydrated CO2 absorber? Sevo: Des: Iso: N2O:
Des:
Iso:
N2O:
What gases are stable in dehydrated CO2 absorber? Sevo: Des: Iso: N2O:
Only N2O.
Sevo, Des, and Iso are UNSTABLE in DEhydrated CO2 absorber
What are the toxic byproducts of: Sevo: Des: Iso: N2O:
Sevo: compound A
Des: CO
Iso: CO
N2O: none
What is solubility?
the tendency of a solute to dissolve in a solvent
“gas to dissolve in the blood”
Will a non polar or polar solute be more soluble in a hydrophilic solvent?
polar
Will a non polar or polar solute be more soluble in a lipophilic solvent?
non polar
What gas law describes the solubility of gases in solution?
Henry
How do we measure solubility?
partition coefficient
What is the blood:gas partition coefficient?
the relative solubility of an inhalation anesthetic in the blood vs. in the alveoli when the partial pressures of the two compartments are equal
What is the BLOOD : GAS PARTITION COEFFICIENT (λ) equation?
λ = Anesthetic dissolved in the blood /Anesthetic inside the alveoli
What are the blood:gas partition coefficients of: Sevo: Des: Iso: N2O:
Sevo: 0.65
Des: 0.42
Iso: 1.46
N2O: 0.46
What are the brain:blood partition coefficients of: Sevo: Des: Iso: N2O:
Sevo: 1.7
Des: 1.3
Iso: 1.6
N2O: 1.1
What are the muscle:blood partition coefficients of: Sevo: Des: Iso: N2O:
Sevo: 3.1
Des: 2
Iso: 2.9
N2O: 1.2
What are the fat:blood partition coefficients of: Sevo: Des: Iso: N2O:
Sevo: 47.5
Des: 27.2
Iso: 44.9
N2O: 2.3
What are the oil:gas partition coefficients of: Sevo: Des: Iso: N2O:
Sevo: 47
Des: 19
Iso: 91
N2O: 1.4
What is FA a function of?
rate of delivery to alveoli
rate of removal from alveoli
What determines anesthetic gas delivery to alveoli?
vaporizer setting, time constant of delivery system, anatomic dead space, alveolar ventilation, FRC
What determines the removal of anesthetic gas from alveoli?
solubility of anesthetic in the blood, Cardiac output, pressure gradient between alveolar gas and mixed venous blood
How are anesthetic gases delivered to the body?
enters the blood and CO distributes it to the body
Rank the gases from fasted to slowest induction. Sevo: Des: Iso: N2O:
N2O fastest
Des
Sevo
Iso slowest
What is FA and FI?
FA is partial pressure of gas in the alveoli
FI is anesthetic exiting the vaporizer
Concentration of an agent inside the ____ is proportional to its concentration inside the ____ and this is proportional to the anesthetic inside the ____.
Concentration of an agent inside the alveoli is proportional to its concentration inside the blood and this is proportional to the anesthetic inside the brain.
How does low gas solubility affect onset of anesthesia?
low solubility causes less uptake in the blood, increases the rate of rise leading to faster equilibrium of FA/FI leading to faster onset
How does high gas solubility affect onset of anesthesia?
high solubility causes more uptake in the blood, decreases the rate of rise leading to slower equilibrium of FA/FI leading to slower onset
What factors increase wash in of anesthetic gas leading to faster onset?
high FGF, high alveolar ventilation, Low FRC, low time constant, low Vd
What factors decrease uptake of anesthetic gas leading to faster onset?
low solubility, low CO, low Pa-Pv difference
What factors decrease wash in of anesthetic gas leading to slower onset?
low FGF, low alveolar ventilation, high FRC, high time constant, high Vd
What factors increase uptake of anesthetic gas leading to slower onset?
high solubility, high CO, high Pa-Pv difference
For each tissue type, what is uptake dependent on?
Tissue blood flow, Solubility of the anesthetic in the tissue, Arterial blood : tissue partial pressure gradient
What percentage of CO and body mass does the vessel rich group receive?
75% CO
10% body mass
What percentage of CO and body mass does muscle and skin consist of?
20% CO
50% body mass
What percentage of CO and body mass does the fat consist of?
5% CO
20% body mass
What percentage of CO and body mass does the vessel poor group consist of?
<1% CO
20% body mass
What does the vessel rich group consist of?
heart, brain, kidneys, liver, endocrine glands
What are the three ways inhaled anesthetics are removed from the body?
from alveoli, hepatic biotransformation, percutaneous loss
What percentage of hepatic biotransformation is responsible for metabolizing Des, Iso, and Sevo?
rule of 2’s
Des 0.02%
Iso 0.2%
Sevo 2%
How are anesthetic gas metabolized in the liver?
P450 system by CYP 2E1
What are metabolites of Des and Iso?
inorganic fluoride ions and triflouracetic acid (TFA)
What is the cause of halothane hepatitis?
TFA
What are signs of high output renal failure as a result of sevo metabolism?
polyuria, hypernatremia, hyperosmolarity, increased plasma creatinine, & inability to concentrate urine
Which anesthetic gas creates compound A when exposed to soda lime?
Sevo
What explains why Nitrous have a high blood:gas partition coefficient than Desflurane but a faster onset?
concentration effect
What is the concentratION effect?
the higher the concentration of gas delivered to the alveolus, the faster its onset of action. Only w/ N2O