Exam 2: Uptake / Distribution of Inhalation Agents

Question 1

Uptake =

Answer 1

ƛ * Q * (A-v)

Solubility * CO * difference in alveolar/venous partial pressures

Question 2

For IAs, blood is an:

Answer 2

inactive reservoir

Question 3

Higher blood-gas coefficient means:

Answer 3

Agent is more soluble

More agent in blood = less in alveoli/brain

Question 4

Another name for blood-gas partition coefficient:

Answer 4

Oswaldt Solubility Coefficient

Question 5

Brain-level activity of a highly vs. minimally soluble IA:

Answer 5

Highly soluble: low brain activity

Minimally soluble: high brain activity

Question 6

Effect of solubility on induction and emergence:

Answer 6

Less soluble = faster induction/emergence

More soluble = slower induction/emergence

Question 7

Five partial pressure gradients between vaporizer and end-target tissue:

Answer 7

Vaporizer and inflow
Inflow and circuit
Circuit and alveoli
Alveoli and blood
Blood and tissues

Question 8

Impact of HCT on B/G coefficient:

Answer 8

↓ HCT = ↓ B/G coefficient
Dropping HCT from 21 –> 43 drops B/G coefficient by 20%
D/t less binding sites in the blood

Question 9

FA vs. FI:

Answer 9

FA = alveolar concentration
FI = inspired concentration

Question 10

FD = FI when:

Answer 10

High flow rate with no re-breathing

Question 11

Make these changes to ventilation to ↑ uptake:

Answer 11

↓ TV, ↑ rate

Question 12

PA of volatile anesthetic is determined by (4):

Answer 12

PI (inhaled partial pressure)
Alveolar ventilation
Breathing circuit
FRC

Question 13

Normal VA:

Answer 13

4L/min

Question 14

Solubility’s effect on the rate at which FA approaches FI:

Answer 14

Least soluble = fastest rate of matching FA to FI

Question 15

Describe the FA/FI curve:

Answer 15

First rise: VRG uptake
First knee: VRG at equilibrium
Second rise: MG uptake
Second knee: MG at equilibrium
Third rise: FG/VPG uptake (very slow)

Question 16

Solubility’s effect on the rate of rise of FA/FI curve:

Answer 16

Less soluble = faster rate of rise

Question 17

Overpressure is:

Answer 17

The use of high FD to increase the speed of FA=FI equilibration

Question 18

Effect of CO on induction speed:

Answer 18

↑ CO = ↓ induction speed

Question 19

Tissue uptake equation:

Answer 19

Uptake = tissue/blood coefficient * flow * (a-t)

Question 20

The coefficient that most influences FA/FI rise:

Answer 20

Blood-gas

Question 21

The coefficient that most influences the FA/FI tail:

Answer 21

Tissue-gas

Question 22

MAC is:

Answer 22

Minimum alveolar concentration; ED50 of inhaled anesthetics. The concentration that will produce absence of movement in 50% of the population.

Question 23

↑ ventilation will have more of an effect on FA/FI curve for this type of agent:

Answer 23

Highly soluble agent

Question 24

Effect of both ↑ ventilation and ↑ CO:

Answer 24

↑ ventilation has more effect (to speed induction) than ↑ CO does (to slow it)

Question 25

If only one lung is intubated, what is the effect on the rise in FA and rise in Pa?

Answer 25

FA rises faster than if the ETT was in the trachea

However, loss of uptake from unventilated lung leads to overall depressed ↑ in Pa

Question 26

Type of gas that will washout fastest:

Answer 26

Least soluble

Question 27

N2O is ____x as soluble as nitrogen:

Answer 27

34x

Question 28

Places that N2O can diffuse into during surgery:

Answer 28

ETT cuff
Bowel obstruction
Pneumothorax/pneumocephalus
Inner ear
Ophtho procedures using gas bubbles
Air embolus