Lecture 7 Formulas

Question 1

Blood-Gas Partition Coefficient of N2O

Answer 1

0.47 L/L

Question 2

Water-Gas Partition Coefficient of N2O

Answer 2

0.39L/L

Question 3

Oil-Blood Partition Coefficient of N2O

Answer 3

2.98L/L

Question 4

Ostwald Solubility Coefficient

Answer 4

Volume of Gas which dissolves in one unit volume of liquid at a specific temperature.
It is independent of pressure

Question 5

Solubility of Oxygen in Plasma

Answer 5

0.0031 ml/(mmHg x dL)

Question 6

Oxygen Content Equation

Answer 6

1.36 ml O2/(gm Hb) x Hb (gm/dL) x SaO2/100 + 0.0031 ml O2/(mmgHg x dL) x PaO2 (mmHg)

Question 7

Pharmacokinetics of Inhalational Anesthetics

Answer 7

Uptake = Solubility x Cardiac Output x Pa-Pv

Question 8

MAC Definition

Answer 8

Minimum Alveolar Concentration in percent, at equililbrium, at one atmosphere, at which 50% of test subjects will not respond to noxious stimuli.

Question 9

MAC Sevoflurane

Answer 9

For 20 yo = 2.6% and decreases by 0.2% per decade.

Question 10

Uptake Order

Answer 10

Inspired Gas, Alveolar Gas, Vessel Rich Group, then Muscle Group, then Fat Group

Question 11

Sevo vs Des Emergence

Answer 11

Sevoflurane and desflurane ultimately have the same rate of coming off, with des only beating it by maybe a couple minutes.

Question 12

Second Gas Effect

Answer 12

When using N2O, it dissolves so rapidly into the blood that the alveoli actually shrinks. This causes a higher partial pressure of agent in the alveoli (in our example 30% greater). It works for the first couple breaths until the blood is fully saturated.

Question 13

Agent Details

Answer 13

Halothane: Vapor Pressure 243mmHg, MAC 0.75%
Isoflurane: Vapor Pressure 238mmHg, MAC 1.15%
Desflurane: Vapor Pressure 664mmHg, MAC 6-7.25%
Sevoflurane: Vapor Pressure 160mmHg, MAC 1.6-2.6%

Question 14

Desflurane Vaporizer

Answer 14

Measured Flow Vaporizer
Tec 6 vaporizer which heats desflurane to 39C at 2 atm
Relies on back pressure and fresh gas flow through the fixed restrictor and agent flow through the variable resistor

Question 15

Henry’s Law

Answer 15

At a particular temperature the amount of a given gas dissolved in a given liquid is directly proportional to the partial pressure of the gas in equilibrium with the liquid.