inhaled anesthetics 1 Flashcards

1
Q

name this agent and how many atoms

A

sevoflurane (7 fluorine atoms)
fluoromethyl 2,2,2 trifluoro 1 trifluoromethyl ethyl ether

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2
Q

in an atmospheric temperature, the ethers and alkane exist as

A

liquids

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3
Q

name the ethers (R-O-R)

A

desflurane
isoflurane
sevoflurane
enflurane
methoxyflurance
ether

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4
Q

name the alkanes (R-H)

A

halothane
chloroform

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5
Q

name the gases

A

nitrous oxide
cyclopropane
xenon

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6
Q

name this agent and how many atoms

A

desflurane
difluoromethyl 1,2,2,2 tetrafluoroethyl ether
6 fluorine atoms

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7
Q

name this agent and how many atoms

A

isoflurane
5 fluorine atoms + 1 chlorine atoms
1 chloro 2, 2, 2, trifluoroethyl difluoromethyl ether
the addition of a chlorine atom increases potency as well as blood and tissue solubility

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8
Q

which anesthetic agents have chiral carbons

A

desflurane and isoflurane

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9
Q

which anesthetic agent does not have a chiral carbon

A

sevoflurane

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10
Q

desflurane full fluorination has the following effects

A

decreased potency (and decreased oil:gas solubility)–> increased MAC
increased vapor pressure (decreased intermolecular attraction) –> requires heated vaporizer
increased resistance to biotransformation (decreased metabolism) –> decreased trifluoroacetate makes an immune mediated hepatitis extremely unlikely

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11
Q

name this agent and its atoms

A

halothane
2 bromo 2 chloro 1, 1, 1, trifluoroethane
(presence of a bromide atom and lack of an ether bridge are dead giveaways)

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12
Q

name its agent

A

nitrous oxide

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13
Q

definition of vapor pressure
vapor pressure is directly proportional to

A

pressure exerted by vapor in equilibrium with its liquid or solid phase inside of a closed container
temperature (increased vapor pressure, increased temperature)

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14
Q

vapor pressure is less than

A

atmospheric pressure

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15
Q

boiling occurs when

A

vapor pressure equals atmospheric pressure

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16
Q

atmospheric pressure is directly proportional to

A

boiling point
increased atmospheric pressure, increased boiling point

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17
Q

daltons law of partial pressure

A

the sum of total gas pressure in a container is equal to the sum of partial pressures exerted by each gas

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18
Q

partial pressure of particular gas equation

A

vol% x total gas pressure
ex) 6% desflurane at sea level delivers a total partial pressure of 45.6mmHg (.06 x 760mmHg)

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19
Q

two inalational agents that become unstable in desiccated soda lime and what they can produce

A

desflurane and isoflurane –> can produce carbon monoxide (des more than iso)

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20
Q

sevoflurane
vp
bp
molecular weight (g)
preservative
stable in hydrated CO2 absorber
stable in dehydrated CO2 absorber
toxic byproduct

A

vp 157
bp 59
molecular weight (g) 200
preservative no
stable in hydrated CO2 absorber no
stable in dehydrated CO2 absorber no
toxic byproduct compound A

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21
Q

desflurane
vp
bp
molecular weight (g)
preservative
stable in hydrated CO2 absorber
stable in dehydrated CO2 absorber
toxic byproduct

A

vp 669
bp 22
molecular weight (g) 168
preservative no
stable in hydrated CO2 absorber yes
stable in dehydrated CO2 absorber no
toxic byproduct carbon monoxide

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22
Q

isoflurane
vp
bp
molecular weight (g)
preservative
stable in hydrated CO2 absorber
stable in dehydrated CO2 absorber
toxic byproduct

A

vp 238
bp 49
molecular weight (g) 184
preservative no
stable in hydrated CO2 absorber yes
stable in dehydrated CO2 absorber no
toxic byproduct carbon monoxide

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23
Q

nitrous oxide
vp
bp
molecular weight (g)
preservative
stable in hydrated CO2 absorber
stable in dehydrated CO2 absorber
toxic byproduct

A

vp 38,770
bp -88
molecular weight (g) 44
preservative no
stable in hydrated CO2 absorber yes
stable in dehydrated CO2 absorber yes
toxic byproduct none

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24
Q

blood: gas partition coefficient=

A

anesthetic dissolved in blood / anesthetic inside alveolus

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25
Q

describe low blood: gas solubility

A

less likely to be taken up by blood
as a result, more agent is available to exert a partial pressure in the alveoli and brain

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26
Q

describe high blood: gas solubility

A

more likely to be taken up by blood
less of the agent is available to exert a partial pressure in the alveoli and brain

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27
Q

blood: gas partition coefficient of sevoflurane

A

0.65

28
Q

blood: gas partition coefficient of desflurane

A

0.42

29
Q

blood: gas partition coefficient of isoflurane

A

1.46

30
Q

blood: gas partition coefficient of N2O

A

0.46

31
Q

first gas on Fa/Fi curve and order from top to bottom

A

N2O
desflurane
sevoflurane
isoflurane
halothane

(shows when FA will = FI)
plateau is steady state

32
Q

FA (uptake) is dependent upon 2 things

A

delivery from anesthesia machine to alveoli
rate of transfer from alveoli to blood

33
Q

what are factors in delivery from anesthesia machine to alveoli for FA

A
  1. setting on the vaporizor
  2. time constant on the delivery system
  3. anatomic dead space
  4. alveolar ventilation
  5. volume of the FRC
34
Q

what are factors in rate of transfer from alveoli to blood for FA

A
  1. Blood:Gas solubility
  2. CO
  3. Pa-Pv difference
35
Q

factors that increase wash in for gas

A

high FGF
high alveolar ventilation
low FRC
low time constant
low anatomic dead space

36
Q

factors that decrease wash in for gas

A

low solubility
low CO
low Pa-Pv difference

37
Q

Fi=

A

concentration of anesthetic leaving the vaporizor

38
Q

FA=

A

partial pressure of anesthetic inside the alveoli

39
Q

surrogate for concentration of inhaled anesthetic in the brain

A

FA
alveolar partial pressure ~ blood partial pressure ~ brain partial pressure

40
Q

solubility of anesthetic gas in relation to onset

A

low solubility –> decreased uptake into blood –>increased rate of rise –> faster equilibration of FA/Fi–> faster onset

high solubility–> increased uptake into blood –> decreased rate of rise —> slower equilibration of FA/Fi–> slower onset

41
Q

factors that decrease wash in for gas

A

low FGF
low alveolar ventilation
high FRC
high time constant
high anatomic dead space

42
Q

factors that increase wash in for gas

A

high solubility
high CO
high Pa-Pv difference

43
Q

Name the 4 tissue groups
how much CO each receives
% body mass
organs included in each group

A
44
Q

rate of anesthetic uptake into the tissues is dependent upon

A
  1. tissue BF
  2. solubility coefficient (solubility of anesthetic in tissue)
  3. arterial blood: tissue partial pressure gradient
45
Q

the vessel rich group consists of (5)

A

heart, brain, kidneys, liver, endocrine gland

46
Q

first group to equilibrate with FA

A

vessel rich group

47
Q

inhaled anesthetics are eliminated from the body in 3 ways

A
  1. elimination from alveoli (primary mechanism)
  2. hepatic biotransformation (secondary mechanism, P450 system)
  3. percutaneous loss (minimal and not clinically significant)
48
Q

hepatic biotransformation % of each gas from least to most

A

N2O: 0.004%
Desflurane 0.02%
Isoflurane 0.2%
Sevoflurane 2-5%
Halothane 20%

49
Q

byproduct of halothane

A

trifluoroacetic acid (TFA), responsible for halothane hepatitis

50
Q

metabolic byproducts of desflurane and isoflurane

A

inorganic fluoride ions and TFA

51
Q

metabolic byproducts of sevoflurane

A

inorganic fluoride ions. maybe responsible for high output renal failure that does not respond to vasopressin.

52
Q

is N2O metabolized in the body

A

nah

53
Q

what do desflurane and isoflurane produce in desiccated soda lime

A

carbon monoxide

54
Q

what does sevoflurane produce in hydrated OR desiccated soda lime

A

compound A

55
Q

minimum FGF with sevo per the FDA

A

minimum FGF 1L/min for up to 2 MAC hours and 2L/min after 2 MAC hours
FGF <1L/min are not recommended at any time

56
Q

define the concentration effect

A

the higher the concentration of anesthetic delivered to the alveolus, the faster the onset on action (also called over pressuring)
temporarily reduces alveolar volume
only applies to induction

57
Q

nitrous oxide is ______ times more soluble in the blood than nitrogen

A

34x

58
Q

describe the concentrating* effect

A

explains why nitrous oxide achieves the fastest rate of FA/Fi even though desflurane is soluble in the blood. The sheer volume of nitrous oxide movement more than compensates for the difference in blood solubility

59
Q

define ventilation effevt

A

the greater the alveolar ventilation, the greater the rate of rise for FA/Fi

60
Q

difference between concentration effect and second gas effect

A

concentrating effect deals with single gas while second gas effect is when N2O is co administered

61
Q

how does the second gas effect work

A
  1. when N2O and the second gas are introduced into the alveolus, rapid uptake of N2O causes alveoli to shrink temporarily
  2. reduction of alveolar volume and augmented tracheal inflow causes a relative increase in concentration of second gas (ex: iso)
  3. pp of alveolar O2 also increases as alveolus shrinks. this is also a transient effect
  4. end result: alveolar concentration of other gases is higher than if they were administered alone
62
Q

gas containing areas of body can absorb how many liters of N2O within the first two hours of administration?

A

30L

63
Q

define diffusion hypoxia

A

when you shut off N2O, N2O that has accumulated in the body transfers to the alveoli for elimination in the first 1-5 min. can temporarily dilute alveolar O2 and CO2 concentrations leading to diffusion hypoxia and hypocarbia (reduced stimulus to breathe)

64
Q

in the presence of right to left shunt (bypassing lungs), which agents will be most affected

A

agents with lower solubility will be most affected
desflurane is affected the most with the lowest B:G partition coefficient (.42) and isoflurane is affected the least because it has the highest B:G partition coefficient (most soluble)

65
Q

in the presence of left to right shunt, how is FA/Fi affected

A

it isn’t

66
Q

in the presence of left to right shunt, how is IV induction affected

A

slower IV induction (recirculated in lungs)