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Sp: PMI > 7. Inhalational Induction / Emergence > Flashcards

7. Inhalational Induction / Emergence Flashcards

1
Q

Inspired Concentration
(Fi)

A

concentration of volatile agent in the anesthesia machine/inspiratory tubing of the circuit

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2
Q

Fi monitor observation

A

in SEVO

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3
Q

alveolar concentration
(Fa)

A

concentration of volatile agent in the alveoli

concentration of agent in the expiratory tubing of the circuit

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4
Q

Fa vs Fi relationsip

A

Fa < Fi

body is absorbing some VA

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5
Q

Fa monitor observation

A

end tidal sevo concentration

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6
Q

Fa:Fi ratio

A

how concentrated the alveoli are (Fa) compared to how concentrated the machine is (Fi)

[lungs] < [machine]

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7
Q

Fa:Fi ratio for induction

A

<1

concentration in lungs (Fa) will always be lower than the concentration in machine (Fi) when VA is turned on

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8
Q

When does Fa:Fi approach 1

A

as the blood gets saturated w/agent
diffusion of agent from lung to blood slows
[lung] increases close to [machine]

concentration of VA in lungs builds up over time

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9
Q

inhalational induction mechanism

A
  1. volatile agent turned on
  2. [machine] increases (Fi)
  3. [alveoli] increases (Fa)
  4. agent diffuses from alveoli to blood
  5. agent from blood diffuses into brain (tissues)
  6. [brain] sufficiently high = pt asleep
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10
Q

inhalational induction speed depends on:

A
  1. lung to blood diffusion speed
  2. blood to brain diffusion speed
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11
Q

Faster diffusion of agent into blood

A

faster build up of [lung]
greater [lung]:[blood] gradient
faster diffusion into blood
faster induction

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12
Q

Slower diffusion of agent into blood

A

slower build up of [lung]
smaller [lung]:[blood] gradient
slower diffusion into blood
slower induction

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13
Q

desflurane blood solubility

A

low blood solubility

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14
Q

low blood solubility

A

slow diffusion of agent into blood
faster buildup of [lung]
– high initial [lung]

fast diffusion from blood into brain
– low [blood]

high [lung]: low [blood] = lrg conc gradient
== faster diffusion into blood

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15
Q

low blood solubility summary

A

faster buildup in lungs
greater [lung]:[blood] gradient
faster diffusion into blood
faster diffusion into brain
faster inhalational induction

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16
Q

isoflurane blood solubility

A

high blood solubility

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17
Q

high blood solubility summary

A

slower buildup in lungs
smaller [lung]:[blood] gradient
slower diffusion into blood
slower diffusion into brain
slower inhalational induction

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18
Q

high blood solubility

A

fast initial diffusion into blood
slow buildup in lungs
–low initial [lung]

slow diffusion from blood into brain
– high [blood]

low [lung] : high[blood] = sm conc gradient
== slower diffusion into blood

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19
Q

low cardiac output inhalational induction speed

A

[lung] rises more quickly
[blood] rises more quickly

faster diffusion into blood and brain

faster inhalational induction

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20
Q

high cardiac output inhalational induction speed

A

[lung] rises slowly
[blood] rises slowly

slower diffusion into blood and brain

slower inhalational induction

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21
Q

low cardiac output induction

A

inhalational: fast
IV: slow

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22
Q

high cardiac output induction

A

inhalation: slow
IV: fast

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23
Q

minute ventilation and inhalational induction

A

increase MV
increase inhalational induction speed

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24
Q

minute ventilation

A

RR X TV

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25
Q

increase TV

A

more surface area for gas exchange
increase MV
increase inhalational induction

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26
Q

increase RR

A

constantly replenish alveoli w/more volatile agent
increase inhalational induction

27
Q

FRC

A

volume of air in the lungs at end of normal expiration

28
Q

low FRC (inhalational induction)

A

less space in alveoli
higher volatile agent [lung]
faster inhalational induction

29
Q

pediatric inhalational induction speed

A

faster due to low FRC

30
Q

high FRC (inhalational induction)

A

more space in alveoli
lower volatile agent [lung]
slower inhalational induction

31
Q

factors that cause Fa (agent [lung]) to build up quickly (4)

A

low blood solubility of agent
low cardiac output
high minute ventilation
low FRC

32
Q

Fa:Fi curve

A

depicts how fast the Fa:Fi ratio approaches 1

33
Q

Fa:Fi curve steep slope

A

agent builds up quickly in lungs
lower blood solubility = faster induction

34
Q

Fa:Fi curve gradual slope

A

agent builds up more slowly in lungs
higher blood solubility = slower induction

35
Q

why is N2O curve steeper than Des?

A

N2O is given in much higher concentrations (25-75%) compared to Des at 6-8%

higher concentrations lead to faster buildup in lungs (Fa)

36
Q

Ways to speed up inhalational induction (4)

A
  1. higher percentage of agent
  2. higher fresh gas flow (FGF)
  3. choose agent w/lowest blood solubility
  4. decreased circuit volume
37
Q

FGF affect on induction speed

A

increasing FGF allows machine dead space to fill more quickly

38
Q

Factors for Faster Inhalational induction (8)

A
  1. faster buildup in alveoli
  2. lower blood solubility of agent
  3. higher % on vaporizer
  4. higher FGF
  5. smaller anesthesia circuit volume
  6. lower cardiac output
  7. higher minute ventilation
  8. low FRC (including peds)
39
Q

Factors for slower inhalational induction

A
  1. slower buildup of agent in alveoli
  2. higher blood solubility of agent
  3. lower % on vaporizer
  4. lower FGF
  5. large circuit volue
  6. higher cardiac output
  7. lower minute ventilation
  8. higher FRC
40
Q

O2 consumption of awake normothermic 70kg male

A

250 mL/min

41
Q

how much is O2 consumption reduced under GA in most pts?

42
Q

minimum FGF for adults

A

0.5L/min

ensures circuit has adequate pressure

43
Q

low FGF advantages

A
  1. cost effective (preserves agent)
  2. preserves trachea heat/moisture
  3. preserves CO2 bsorber
  4. preserves pt body temo
44
Q

low FGF disadvantages

A
  1. slower inhalational induction
  2. slower emergence
45
Q

high FGF advantages

A
  1. faster inhalational induction
  2. faster emergence
46
Q

high FGF disadvantages

A
  1. expensive (agent wasted)
  2. dries out pt airway (moisture/heat loss)
  3. accelerates drying out of CO2 absorber
47
Q

low flow wizard

A

tells how much flow is req to get job done
- TV, RR, uptake, leaks
saves $$
preserves pt temp
helps detect leaks in system

48
Q

wakeup aka

A

recovery
emergence

49
Q

groups of tissues that the volatile agents impact

A

vessel rich
muscle
fat

50
Q

vessel rich group

A

75% of CO

brain
heart
liver
kidney
endocrine

quick on
quick off

51
Q

muscle rich group

A

20% CO

skin
muscle

52
Q

fat group

A

5% CO

slow on
slow off

53
Q

which tissues are volatile agents most soluble in?

54
Q

wakeup mechanism

A
  1. vaporizer off (FGF up)
  2. agent [machine] and [lungs] decr
  3. agent diffuses from blood to lungs
  4. agent [blood] decreases
  5. agent diffuses from tissues to blood
  6. when agent [fat] low enough, [blood] and [brain] will be low enough for wakeup
55
Q

to decrease the agent concentration in machine and lungs faster, what can you do?

A

increase FGF rate

56
Q

low blood solubility: emergence

A

faster

agent wants to get out of blood
diffuses more quickly into lungs

57
Q

high blood solubility: emergence

A

slower

agent wants to stay in blood
diffuses slower into lungs

58
Q

factors that cause slower wakeup (13)

A
  1. older age
  2. obesity (more agent in fat)
  3. long sx times (more agent in fat)
  4. sx w/higher [agent] (more agent in fat)
  5. high blood solubility volatile agent
  6. higher dose narcotics
  7. lower FGF (emergence)
  8. lower minute ventilation (emergence)
  9. closed APL valve (emergence)
  10. higher FRC
  11. lung disease
  12. low CO
  13. hypothermia
59
Q

low FGF rate

60
Q

high FGF rate

A

10-15 L/min

61
Q

how does a closed APL valve slow down emergence?

A

more rebreathing of agent

62
Q

pediatrics emergence

A

faster than adults

peds have higher % blood flow to vessel rich group

lower % blood flow going to fat

faster on
faster off

63
Q

factors in pediatric faster emergence

A
  1. higher minute ventilation (faster RR)
  2. lower FRC
  3. higher % BF to vessel rich (less to fat)

Sp: PMI (18 decks)

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