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Dr. Eger Inhaled Anesthesia Lectures (Anes Pharm Exam 3) > Ch5 Anesthetic Pharmacokinetics > Flashcards

Ch5 Anesthetic Pharmacokinetics Flashcards

1
Q

What is anesthetic pharmacokinetics?

A

The study of how anesthetics move into, within, and out of the body.

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2
Q

What do alveolar (FA) and inspired (Fi) concentrations represent?

A

FA is the concentration of anesthetic in the alveoli and Fi is the concentration of anesthetic being delivered.

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3
Q

What is the time constant in anesthetic pharmacokinetics?

A

The time to a 63% change in concentration, calculated from system capacity and flow.

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4
Q

What is the normal functional residual capacity (FRC) for an adult patient?

A

Approximately 2 liters.

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5
Q

What is the normal alveolar ventilation for an adult patient?

A

About 4 liters per minute.

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6
Q

How does solubility affect anesthetic uptake?

A

Higher solubility leads to greater uptake and more opposition to effective ventilation.

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7
Q

What are the three main factors determining anesthetic uptake?

A
  • Solubility
  • Cardiac output
  • Arterial-venous partial pressure difference
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8
Q

True or False: Desflurane is a poorly soluble anesthetic.

A

False.

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9
Q

What is the effect of high solubility anesthetics?

A

They have slower induction and recovery times.

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10
Q

What is the primary reason for slower rise in FA for anesthetics compared to oxygen?

A

Uptake of anesthetics opposes effective ventilation.

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11
Q

What is the concentration effect in anesthesia?

A

The phenomenon where higher concentrations of one anesthetic can increase the uptake of another.

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12
Q

What is the second gas effect?

A

The increased rate of uptake of a second anesthetic due to the presence of a first anesthetic, often nitrous oxide.

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13
Q

Fill in the blank: The time constant for the lungs is _______.

A

half a minute.

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14
Q

What is diffusion hypoxia?

A

A condition caused by the rapid diffusion of nitrous oxide out of the bloodstream, leading to decreased oxygen levels.

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15
Q

Which anesthetics provide faster recovery times?

A
  • Desflurane
  • Sevoflurane
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16
Q

What is the clinical implication of nitrous oxide’s high solubility?

A

It can expand gas-containing cavities, affecting areas like the inner ear and lungs.

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17
Q

How does combining anesthetics affect costs and recovery?

A

It can decrease costs and speed emergence but may not always provide benefits.

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18
Q

What are the characteristics of highly vascular tissues in relation to anesthetic uptake?

A

They equilibrate quickly with anesthetics.

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19
Q

What is the impact of obesity on recovery from anesthesia?

A

Obese patients may have faster recovery due to the limited capacity of fat reservoirs.

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20
Q

What is the significance of arterial-venous partial pressure differences?

A

They determine the difference between alveolar and venous anesthetic concentrations.

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21
Q

True or False: Isoflurane is a poorly soluble anesthetic.

A

False.

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22
Q

What is the role of pre-medication with opioids like fentanyl in anesthesia?

A

It can reduce the perception of anesthetic pungency.

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23
Q

Fill in the blank: Anesthetic solubility affects the difference between _______ and _______ partial pressures.

A

alveolar; venous.

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24
Q

What is the anesthetic solubility of Lean tissues like the brain and fat?

A

Desflurane and nitrous oxide are similar in blood and Lean tissue solubility but differ significantly in fat solubility.

Desflurane is 10 times more soluble in fat than nitrous oxide.

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25
What is the average solubility comparison among desflurane, isoflurane, and sevoflurane?
Fluorine is about twice as soluble as desflurane, isoflurane is about twice as soluble as sevoflurane, and sevoflurane is about twice as soluble as isoflurane. ## Footnote This hierarchy indicates the relative anesthetic potency and uptake rates.
26
What are the four tissue groups based on their time constants?
1. Vessel Rich Group 2. Muscle Group 3. Fat Group 4. Vessel Poor Group ## Footnote Each group has different capacities and time constants affecting anesthetic uptake.
27
What tissues are included in the vessel rich group?
Brain, liver, kidneys, heart, and intestines. ## Footnote These tissues make up about 9% of body mass yet receive three-quarters of cardiac output.
28
How long does it take for the vessel rich group to equilibrate to 98% concentration?
2 to 4 minutes for initial uptake to 98% equilibrium, which takes 8 minutes for full saturation. ## Footnote After 8 minutes, the uptake narrows rapidly.
29
What is the time constant for the muscle group compared to the vessel rich group?
The muscle group has a time constant of 30 to 60 to 90 minutes, which is significantly longer than that of the vessel rich group. ## Footnote This reflects its larger volume and lower flow relative to the vessel rich group.
30
What characterizes the vessel poor group?
Poorly perfused tissues such as bones, ligaments, tendons, and cartilage, which have essentially zero perfusion and thus negligible anesthetic uptake. ## Footnote They make up nearly a quarter of body mass but do not contribute to anesthetic uptake.
31
What does the shape of the anesthetic concentration curves indicate?
An initial rapid rise indicates the unopposed effect of ventilation driving alveolar concentration, while subsequent curves reflect the uptake by different tissue groups. ## Footnote This is influenced by time constants and solubility.
32
True or False: Induction of anesthesia is most rapid with high solubility anesthetics.
False. ## Footnote Other factors, such as pungency, also affect induction speed.
33
What is the significance of pungency in anesthetics?
Pungency can limit the use of certain anesthetics, like desflurane, for induction due to respiratory irritation. ## Footnote Pungency varies at different MAC levels.
34
Fill in the blank: The anesthetic with the least pungency and suitable for rapid induction is _______.
sevoflurane. ## Footnote It is often used for one-breath induction due to its low solubility and absence of pungency.
35
What factors determine the rate of recovery from anesthesia?
1. Solubility 2. Alveolar ventilation 3. Metabolism 4. MAC ratio ## Footnote These factors influence both elimination and washout rates.
36
Why is a rapid recovery from anesthesia desirable?
To avoid hyperalgesia, which can occur at concentrations around 0.1 MAC. ## Footnote Rapid recovery minimizes the risk of increased pain perception post-anesthesia.
37
What is the MAC ratio for nitrous oxide?
Approximately 60%. ## Footnote This ratio influences the required elimination rate for recovery.
38
What is the MAC ratio for sevoflurane?
Approximately 33%. ## Footnote This indicates the need for greater elimination compared to nitrous oxide for recovery.
39
What anesthetic is metabolized and can affect recovery time?
Halothane. ## Footnote Its metabolism may lead to quicker recovery compared to non-metabolized anesthetics.
40
What concentration of propofol is needed to reach an awake state?
19 or 20% ## Footnote This indicates the need for a reduction in propofol concentration for recovery.
41
What is hyperalgesia and at what concentration does it occur?
Hyperalgesia occurs at about 0.1 MAC. ## Footnote This concentration leads to an increase in pain experimentally.
42
Why is rapid recovery from anesthesia important?
* Patient's ability to maintain airway * Cost reduction * Faster room turnover times ## Footnote Faster recovery allows more efficient use of operating room resources.
43
Which anesthetic shows the most rapid decrease in alveolar concentration during elimination?
Desflurane ## Footnote Followed by sevoflurane and isoflurane.
44
How does recovery from sevoflurane compare to halothane in children?
Recovery is shorter with sevoflurane than halothane. ## Footnote This is particularly evident for emergence from anesthesia.
45
What is a common side effect of rapid recovery with sevoflurane?
Increased agitation on wake up. ## Footnote This can be attenuated with narcotics.
46
What factor contributes to prolonged recovery in obese patients?
Fat acts as a reservoir for anesthetic. ## Footnote However, fat near highly perfused tissues can delay recovery.
47
What was the finding of Juvenis' study regarding recovery after anesthesia in obese patients?
Awakening after desflurane was 6 minutes, while after isoflurane it was more than twice that time. ## Footnote Propofol also showed slower recovery compared to desflurane.
48
What is the impact of solubility on recovery from anesthesia?
Poorly soluble anesthetics clear from the lungs more rapidly. ## Footnote This means they have less impact on recovery time.
49
Why might combining anesthetics be beneficial?
* Decrease costs * Speed emergence ## Footnote Combining a poorly soluble agent with a more cost-effective agent can optimize recovery.
50
What is the influence of the anesthetic circuit on recovery?
* Volume of the circuit * Absorption by components * Flow through the circuit ## Footnote These factors determine how anesthetic is delivered and cleared.
51
What does rebreathing during anesthesia do?
It helps maintain concentration of anesthetics. ## Footnote Rebreathing exhaled gas can lower the concentration of anesthetic delivered.
52
What is the result of using low flow rates in anesthesia?
Increased cost and potential for reduced anesthetic concentration. ## Footnote Low flows can affect both inspired and alveolar concentrations.
53
What is the expected time to achieve a specific alveolar concentration of isoflurane at low flow rates?
It will take longer due to the low flow rate and solubility of isoflurane. ## Footnote The solubility affects how quickly the anesthetic can be cleared from the body.
54
What is the goal of heating the flow at one liter per minute in the study?
To observe the uptake of isoflurane at a constant delivered concentration of 1.5% ## Footnote The ultimate goal is to achieve an alveolar concentration of approximately 1.2%.
55
What was the initial alveolar concentration achieved after 31 minutes of isoflurane delivery?
About 25 to 30% of the delivered concentration ## Footnote The delivery concentration was 1.5%, while the inspired concentration was significantly lower.
56
What happens to the alveolar concentration when using a less soluble anesthetic?
The alveolar concentration will increase ## Footnote This is due to lower solubility leading to less uptake.
57
What is the delivered concentration set for SIBO fluorine in the experiment?
Approximately 2.8% ## Footnote This is just over a MAC (minimum alveolar concentration) of 1.2 to 1.3.
58
What is the significance of the inspired concentration relative to the delivery concentration for SIBO fluorine?
The inspired concentration is much higher than for isoflurane ## Footnote The alveolar concentration is about 50% of the delivery concentration.
59
What is the predicted alveolar concentration for the delivered concentration of 8% of death strain?
Approximately 5.6% ## Footnote This is about 70% of the delivered concentration.
60
What is the relationship between the flow rate and control of anesthesia?
Better control is achieved at higher flow rates with a low solubility anesthetic ## Footnote This relates to the solubility and delivery concentration required.
61
How does the solubility of an anesthetic affect its cost?
More soluble anesthetics require a higher delivery concentration, increasing costs ## Footnote It's the delivery concentration that incurs costs, not the inspired or alveolar concentrations.
62
What is a key difference between nitrous oxide and potent inhaled anesthetics?
Nitrous oxide has a MAC above one atmosphere, typically around 105% ## Footnote This requires delivery at high concentrations.
63
What effect does nitrous oxide have on gas-containing cavities in the body?
It can expand these cavities, particularly if they contain poorly soluble gases ## Footnote This includes gases like nitrogen.
64
What is diffusion hypoxia?
A phenomenon where the outpouring of nitrous oxide dilutes other gases in the lungs ## Footnote This can affect oxygen levels during elimination.
65
What two phenomena result from the large volume uptake of nitrous oxide during induction?
Concentration effect and second gas effect ## Footnote These phenomena illustrate the rapid rise of alveolar concentrations.
66
Does the second gas effect significantly influence elimination with nitrous oxide?
No, it has a trivial effect on elimination ## Footnote The effect is much more pronounced during induction.
67
What is a clinical concern related to the distension of the endotracheal tube cuff after nitrous oxide administration?
It can lead to tracheal mucosal ischemia ## Footnote This is due to the cuff becoming distended from nitrous oxide diffusion.
68
What happens to the inner ear during nitrous oxide administration?
Pressure can increase due to the non-compliant nature of the space ## Footnote This can lead to complications like barotrauma.
69
Fill in the blank: The inspired concentration relative to the delivery concentration for isoflurane is _____ .
far below the delivery concentration
70
True or False: The delivery concentration of an anesthetic directly affects its cost.
True ## Footnote Higher delivery concentrations lead to increased costs.

Dr. Eger Inhaled Anesthesia Lectures (Anes Pharm Exam 3) (8 decks)

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