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PMI > 3. Inhalational Anesthetics > Flashcards

3. Inhalational Anesthetics Flashcards

1
Q

apneic threshold

A

highest blood CO2 level at which a pt can remain apneic if holding their breath

IOW: how high their CO2 can climb before they have to take a breath

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2
Q

high apneic threshold

A

pt who can hold breath longer
have less drive to breathe

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3
Q

low apneic threshold

A

pt who cant hold breath as long
have more drive to breathe

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4
Q

what can raise the apneic threshold

A

volatile agents
narcotics
propofol
versed

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5
Q

how do anesthetics raise apneic threshold

A

suppress pts drive to breathe
it will take higher CO2 to stimulate breathing

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6
Q

what lowers the apneic threshold

A

pain

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7
Q

how does pain lower apneic threshold

A

stimulates respirations (faster RR)
difficult to hold breath while in pain

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8
Q

Steps to get pt to spontaneously ventilate prior to wakeup

A
  1. Reverese muscle paralysis (if necessary)
  2. allow pt CO2 to increase
    - slow RR
    - allow them to go completely apneic
  3. pt begins to breath when apneic threshold is reached
    - aka - when the CO2 is high enough
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9
Q

hypoxic drive

A

lowest oxygen level at which the pt can no longer remain apneic

*makes pts w/high CO2 (smokers) breathe

  • if pt is holding breath, lowest level of O2 that a pt can tolerate before they have to take breath
  • O2 level is stimulating pt breathing
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10
Q

hypoxic drive level (normal pt)

A

PaO2 ~ 60mmHg
SpO2 = 90%

  • if CO2 didnt stimulate breathing, a normal pt could hold their breath until SpO2 dropped to 90%
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11
Q

do smokers have high or low CO2 levels?

A

high

decrease alveolar gas exchange
decrease exhalation
increase CO2

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12
Q

what stimulates breath in healthy pts

A

hypercarbia»hypoxia
high CO2»low O2

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13
Q

what stimulates breath in pts w/lung disease

A

hypoxia»hypercarbia
low O2»high CO2

*less responsive to CO2 increase

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14
Q

apneic threshold and hypoxic drive correlation

A

inverse

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15
Q

central chemoreceptors

A

responsible for apneic threshold

respond to change in [H+] in CSF which is determined by PaCO2

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16
Q

peripheral chemoreceptors

A

responsible for hypoxic drive

respond to changes in PaO2

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17
Q

Primary reasons volatile agents are given

A
  1. prevent movement (non-paralyzed pts)
  2. prevent anesthetic awareness (all pts)
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18
Q

is pt ready for surgical incision?

A
  1. is pt going to move?
  2. is pt going to remember?
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19
Q

is it easier to prevent movement or awareness during surgery?

A

awareness is easier than movement

*takes more VA to keep someone STILL than it does to keep them ASLEEP

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20
Q

if we give enough inhalational agent to keep someone STILL…

A

its impossible for them to have awareness

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21
Q

if we only need the agent to prevent awareness and not movement

A

we dont need to give as much agent

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22
Q

2 ways to prevent MOVEMENT

A
  1. give paralytics
  2. give high enough concentration of volatile agent
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23
Q

why would you give a paralytic, even if the surgeon doesnt require one?

A

to keep the pt still withouth having to keep them as deeply anesthetized

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24
Q

higher concentration of volatile agent can make __________ more likely

A

hypotension

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25
Q

Minimum Alveolar Concentration (MAC)

A

minimum alveolar concentration of an exhaled gas that will prevent movement in 50% of pts during incision

*a pt is 50% likely to move if they are exhaling the MAC percentage of agent

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26
Q

< 1 MAC means

A

more than 50% likely to move

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27
Q

> 1 MAC means

A

less than 50% likely to move

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28
Q

1 MAC Desflurane

A

6%

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29
Q

1 MAC Sevoflurane

A

2%

30
Q

1 MAC Isoflurane

A

1.2%

31
Q

1 Mac Nitrous Oxide

A

105%

32
Q

most potent volatile agent

A

Isoflurane

33
Q

lease potent volatile agent

A

Desflurane

34
Q

what does MAC tell us clinically?

A

how much volatile agent we need to give in order to prevent someone from moving

35
Q

inspiratory concentration

A

concentration of agent in the machine/inspiratory limb of the circuit

36
Q

inspiratory concentration matches

A

concentration of the agent selected on the vaporizer dial

37
Q

expiratory concentration
“end tidal”

A

concentration of agent that the pt is actually exhaling

38
Q

which concentration do we care about for MAC values?

A

expiratory
(et)

39
Q

expiratory concentration ____ inspiratory concentration

A

et less than in

40
Q

MAC values reflect

A

potency

41
Q

pts are less likely to move when breathing a ______percentage of agent

A

higher percentage (MAC value)

42
Q

MAC Awake

A

0.4 MAC

43
Q

MAC Awake is needed to

A

prevent awareness w/o surgical incision

44
Q

prevent awareness during surgery w/narcotics/paralytics

A

0.8 MAC

45
Q

prevent awareness during surgery w/o narcotics/paralytics

A

1 MAC

46
Q

how much MAC will prevent movement in 95% of pts

A

1.3 MAC

47
Q

0.4 MAC Sevo

A

0.8%

48
Q

0.4 MAC Iso

A

0..48%

49
Q

0.4 MAC Des

A

2.4%

50
Q

0.8 MAC Sevo

A

1.6%

51
Q

0.8 MAC Iso

A

0.96%

52
Q

0.8 MAC Des

A

4.8%

53
Q

1.3 MAC Sevo

A

2.6%

54
Q

1.3 MAC Iso

A

1.56%

55
Q

1.3 MAC Des

A

7.8%

56
Q

when do you look at RR for guaging pt readiness for incisions?

A

spontaneously ventilating pts only

57
Q

SV pt w/high RR

A

might not be anesthetized enough to tolerate incision w/o moving

need more narcotic/volatile agent

58
Q

SV pt w/low RR

A

more likely to tolerate an incision w/o moving

59
Q

DECREASE MAC requirement

A

we dont need to give as high of a concentration to achieve same effect

60
Q

7 factors that DECREASE MAC requirement

A

Pregnancy
Blood (hypoxia, hypercarbia, anemia, hypotension)
IV anesthetics
Old age
Temperature (hypothermia and mild hyperthermia)
Acute alcohol intoxication
Signs of Infection (sepsis)

61
Q

how much does MAC decline w/age?

A

4-6% each decade
decline starts before age 40

62
Q

how does pregnancy decrease MAC req?

A

pregnancy is a high progesterone state
progesterone is sedative and decreases reqs by up to 40%

63
Q

hypotension MAP that decreases MAC

A

<40mmHg

64
Q

INCREASE MAC requirement

A

we have to give more of the agent to have same effect

65
Q

4 factors that INCREASE MAC requirements

A

Young (peds pt)
Hot
Salty
Alcoholics

66
Q

Young

A

sevo - highest MAC req is from 0-1 mo
others - highest MAC req is 6 mo

67
Q

Hot

A

extreme hyperthermia (<42C)
burn injury

68
Q

Salty

A

hypernatremic pts

69
Q

Alcoholics

A

Chronic alcohol abuse

70
Q

do thyroid conditions impact MAC values?

A

nope :)

71
Q
A

PMI (18 decks)

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