Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ANESTHESIA PHARM 2 > INHALED ANESTHETICS I > Flashcards

INHALED ANESTHETICS I Flashcards

1
Q

what the body does to the drug

A

pharmacokinetics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

pharmacokinetics ADME

A

Absorption
Distribution
Metabolism
Elimination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

the depth of general anesthesia depends on what?

A

the partial pressure (or gas fraction) exerted by the inhalational agent in the pt’s brain.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

describe how arterial blood partial pressure, alveolar partial pressure, and inspired gas affect brain partial pressure

A

partial pressure of inspired gas (I) affects alveolar (A) partial pressure affects arterial (a) blood partial pressure affects brain (br) partial pressure
VAPORIZER –> CIRCIUT (PI) LUNGS (PA) BLOOD (Pa) BRAIN (Pbr)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

define time constants for inhalational anesthetics

A

TC = volume (capacity)/ flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

why do we turn flows way up in the beginning of the case?

A

reduce time constants
* if volume of the circuit it 6L, and we crank flows up to 12L/min, 1TC = 30sec, so 1.5min to get 95% change in sevo concentration in lungs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

define solubility

A

relative affinity of an anesthetic for two phases (and therefore the partitioning of that anesthetic between the two phases) at equilibrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

is solubility for inhaled anesthetics good or bad? why?

A

bad. slows things down

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

define equilibrium for inhaled anesthetics

A

no difference in partial pressures – partial pressure of two phases is the same between alveoli and lungs (not concentration)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

define partial pressure in a mixture of gases

A

in a mixture of gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how can we increase the partial pressure of inspired agent?

A

increase concentration, increase fresh gas flows (or both), decrease the volume of the circuit (fixed volume), decrease the absorption by the machine/plastics (again, fixed), or wait.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

define alveolar partial pressure (PA)

A

actual pressure inside the lungs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is the goal of agent delivery?

A

drive the alveolar partial pressure (PA) into equilibrium with the inspired partial pressure (PI) (PA/PI = 1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

why is alveolar partial pressure (PA) not static?

A

agent is constantly being absorbed into pulmonary blood flow

*PA = input into the alveoli – uptake into the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how do we increase alveolar partial pressure?

A

increase the amount of agent that is taken into the lungs/ partial pressure of inspired agent

  • increase ventilation (minute ventilation)
  • increase concentration of gas inspired
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

define minute ventilation

A

the volume of gas inhaled or exhaled per minute

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what number do we use to measure partial pressure of agent in the brain?

A

ET gas concentration as a measure of PA (at equilibrium, the alveolar partial pressure should measure the partial pressure of the brain)

18
Q

what are the two ways to increase initial concentration and uptake?

A

1) concentration effect (increase ventilation/ increase concentration)
2) 2nd gas effect

19
Q

define concentration effect

A

impact of the inspired partial pressure of the agent (PI) to increase the rate of rise of the partial pressure of the alveolus (PA)

20
Q

demonstrate concentration effect

A
  • start with 20% gas concentration delivered (20ml gas in a total of 100ml)
  • 50% of gas absorbed into pulmonary circulation
  • concentration of gas remaining in alveoli is 11% (10ml gas in a total of 90ml)
  • by increasing initial concentration to 80%, remaining concentration increases to 67% (40ml of 100ml absorbed, leaving 40ml gas in 60ml total
21
Q

define 2nd gas effect

A

high volume of uptake of one gas accelerates the rate of increase of the PA of the companion gas
* if the uptake of gas A > uptake of gas B, when delivered together, gas A increases the rate of uptake of gas B

22
Q

when is the 2nd gas effect most/ least effective?

A

2nd gas effect is most effective in the first couple of breaths; after that, the effect is negligible

23
Q

on an everyday basis, in what situations is the 2nd gas effect most effective/ most used?

A

inhalational induction of kids

24
Q

PA = ?

A

PA = PI – uptake

25
Q

what affects the uptake of anesthetic agent?

A

solubility, cardiac output, alveolar – venous difference
* UPTAKE = SOLUBILITY * CO * (PA – PV)
(gas dissolved in blood; does not affect PA)

26
Q

define solubility

A

relative affinity of inhaled anesthetic for two phases at equilibrium

27
Q

how does solubility of agent affect PA/PI?

A
  • increasing solubility of agent increases uptake, decreases PA/PI rise, therefore slowing down induction
  • decreasing solubility of agent decreases uptake, increases PA/PI rise, therefore speeding up induction
    • UPTAKE = SOLUBILITY * CO * (PA – PV)
  • ** if PA = PI – uptake, and solubility increases uptake, PA decreases as uptake increases, therefore PA/PI rise is slowed
28
Q

which agent has high solubility (blood/gas partition coefficient) and thus slower induction rate?

A

halothane (2.4), isoflurane (1.4)

29
Q

which agents have low solubility (blood/gas partition coefficient) and thus faster induction rate?

A

desflurane (0.42), nitrous oxide (0.47), sevflurane (0.65)

30
Q

describe how the blood/gas partition coefficient relates to induction

A

the blood/gas coefficient describes how much more agent is needed in the blood to force equilibrium between blood and alveolus. the less soluble a substance is in the blood, the less is necessary in the circulation to force equilibrium in the alveolus because the undissolved gas is taken up by the alveoli more quickly and you’re loosing less to the blood

31
Q

how does cardiac output affect PA/PI?

A

(just the same as solubility) – * increasing cardiac output introduces more “clean” blood (no dissolved agent) to alveolar/vessel interface, thus decreasing the concentration of dissolved agent, requiring more agent to reach partial pressure equilibrium

  • *UPTAKE = SOLUBILITY * CO * (PA – PV)
  • ** if PA = PI – uptake, and CO increases uptake, PA decreases as uptake increases, therefore PA/PI rise is slowed
32
Q

does cardiac output have a greater effect on soluble or insoluble agents?

A

soluble agents

33
Q

what affects tissue uptake of anesthetic gases?

A

TISSUE UPTAKE = TISSUE SOLUBILITY * TISSUE BLOOD FLOW * (PARTIAL PRESSURE OF BLOOD – PARTIAL PRESSURE OF SPECIFIC TISSUE)

34
Q

why do we use end-tidal agent volumes as a measurement of how much agent is being exposed to the brain?

A

because not only are you loosing agent to dissolution in blood, but fat and muscle also on the way to the brain.

35
Q

why do (alveoli and) vessel-rich groups experience such quick agent upload/offload times?

A

vessel-rich groups receive 75% of total cardiac output.

  • tissue uptake is directly proportional to cardiac output.
    • therefore, VRGs upload and offload agent (equilibriate) faster
36
Q

why does muscle experience such slow agent upload/offload times?

A

although muscle comprises 50% of body mass, it only receives 19% of CO
* tissue uptake is directly proportional to cardiac output.

37
Q

why does fat experience such slow agent upload/offload times?

A

fat (20% body mass) only receives 6% of cardiac output.

  • tissue uptake is directly proportional to cardiac output.
    • therefore, fat tends to not absorb an excessive amount of agent (could never reach equilibrium)
38
Q

how do we get rid of anesthetic gases?

A
  • EXHALATION
    • hepatic biotransformation (mostly halothane)
  • ** transcutaneous loss (to the skin)
39
Q

what is the difference in tissue partial pressures during induction vs recovery?

A
  • induction – all tissues have zero partial pressure

* recovery – varying tissue partial pressures (dependent on muscle mass, obesity – thus the art in emergence)

40
Q

what physical/physiologic factors can change agent pharmacokinetics?

A
  • age
  • lean muscle
  • body fat
  • hepatic function (not so much)
  • pulmonary gas exchange
  • cardiac output

ANESTHESIA PHARM 2 (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions