Anesthetics UPTAKE

Question 1

What are 3 major factors affecting UPTAKE and DISTRIBUTION?

Answer 1

a. Solubility of the inhalation anesthetic agent
b. Patient’s cardiac output
c. partial pressure difference of the gas between the alveoli and pulmonary vein

Question 2

What is the solubility of gas determined by

Answer 2

Blood-Gas partition Coefficient

Question 3

What does the B/G partition Coefficient describes

Answer 3

Affinity of gas to blood

Question 4

Isoflurane B/G partition coefficient of 1.4 , what does that mean?

Answer 4

At equilibrium, the isoflurane concentration in the
blood would be 1.4 times the concentration in the gas (alveolar) phase. By definition, the PARTIAL PRESSURE OF THE AGENT IN BLOOD AND GAS ARE IDENTICAL AT EQUILLIBRIUM but the blood would contain more isoflurane.

Question 5

What is the relationship of B/G partition coefficient to blood solubility? How does it affect delivery of anesthetics?

Answer 5

The higher the coefficient number, the more soluble the anesthetic agent will be BLOOD at equilibrium.
Anesthesia onset will be DELAYED

Question 6

What determines anesthesia, is it the amount of drugs in blood or the partial pressure of inhalation agent in the brain?

Answer 6

Partial pressure of inhalation agent in the (blood) and brain determines ANESTHESIA

Question 7

What is the B/G Partition coefficient of Desflurane?

Answer 7

0.45

Question 8

What is the B/G Partition coefficient of Nitrous?

Answer 8

0.47

Question 9

What is the B/G Partition coefficient of Sevoflurane?

Answer 9

0.65

Question 10

What is the B/G Partition coefficient of Isoflurane?

Answer 10

1.4

Question 11

What is the B/G Partition coefficient of Enflurane?

Answer 11

1.8

Question 12

A high partition coefficient means that

Answer 12

it takes more time to FILL the TANK, meaning that it will take time for the partial pressure to get high enough to induce anesthesia.

Question 13

Is the FA/FI for high partition coefficient gas high or low? How does that affect the onset of anesthesia?

Answer 13

Low , because the gas dissolve quickly in the BLOOD , which delays onset of anesthesia?

Question 14

Uptake of soluble inhalation agents can be increased also by what?

Answer 14

by anesthetic overpressuring, that is, delivering a concentration of inspired gas two to four times the MAC

Question 15

The rate of rise of Fa/Fi over time for most agents correlates_______with the relative solubility of the anesthetic agents.

Answer 15

inversely

Question 16

Explain how an increase in Cardiac Output affects FA/FI?

Answer 16

As cardiac output increases, more blood travels through the lungs, thereby removing more anesthetic from the gas phase and resulting in a lower FA and a slower rate of FA increase

Question 17

What has the MOST PRONOUNCED effect on the uptake of more soluble anesthetic?

Answer 17

Changes in Cardiac Output (CO)

Question 18

What determines DELIVERY to the tissue? Explain how it relates to what happening to the FA/FI?

Answer 18

• Alveolar-VENOUS anesthetic gradient
• As the alveolar-venous anesthetic gradient approaches 0 means that TISSUES ARE SATURATED, means that UPTAKE OF ANESTHETIC IN BLOOD has stopped and FA/FI should be approaching UNITY or be closer to 1

Question 19

CO mostly affect

Answer 19

SOLUBLE AGENTS

Question 20

Explain how a decrease in CO affect FA/FI?

Answer 20

Less blood flow to the lungs, less anesthetics TAKEN UP by the lungs, Alveolar concentration is achieved quicker.

Question 21

For Less soluble anesthetic, the rate of Fa/Fi increase is rapid and does not depend on ________.

Answer 21

Cardiac Output

Question 22

With highly soluble agents, a potentially dangerous

positive feedback exists. Explain.

Answer 22

Anesthetic-induced cardiac depression decreases uptake, increases alveolar concentration, and further depresses
cardiac output.

Question 23

Vessel RICH group received _____%of CO

Answer 23

75% of CO

Question 24

Muscle group received ____-%of CO

Answer 24

19%

Question 25

Explain the path when anesthetic agent are delivered?

Answer 25

The anesthetic agent in the blood first go to the vessel- rich tissues (lungs, heart, brain) Then after blood returns to the lungs, depending on its blood-gas partition coefficient, it has the same partial pressure that it had on leaving the lungs. As the gradient for the uptake of anesthetic approaches 0, less agent is taken up, and alveolar concentration rises

Question 26

FA/FI and children, explain.

Answer 26

Children have greater perfusion of the vessel rich
group than do adults, GREATER CO to Fa/Fi rises more rapidly in children, so anesthesia is achieved more rapidly in these patients.
IN CHILDREN IT’S the OPPOSITE, CO increase FA/FI