Pharmacology 2

Front 1

FD

FI

Back 1

Fraction delivered from the Vaporizer
Partial pressure of agent in the inspiratory limb (concentration in circuit)

Front 2

FA

Fa

Pbr

Back 2

Partial pressure of agent in the alveoli

Partial pressure of agent in arterial
blood

Partial pressure of agent in brain

Front 3

How is FA determined?

Back 3

FA= FI (delivery)- uptake (loss)

Front 4

What factors is input dependent on?

Back 4

1) FI- inspired partial pressure of agent
2) Characteristics of the anesthetic breathing system (length of circuit/deadspace, rubber components in system, fresh gas flow)
3. Alveolar ventilation

Front 5

What factors is uptake dependent on?

Back 5

1. Solubility of the agent
2. Cardiac output
3. Alveolar to venous partial pressure difference

Front 6

What factors speed the onset of anesthetic?

Back 6

1. Increase concentration of agent
2. Increase fresh gas flow
3. Use low solubility agent
4. Overpressure technique (although may be offest by decreased circulation to brain)

Front 7

Define the concentration effect.

Back 7

When an initially high FI offsets the impact of uptake and therefore accelereates the induction of anesthesia as reflected by the rate of rise of the PA

Front 8

Define absorbtive atelectasis?

Back 8

If a gas with a low blood: gas solubility (Nitrous) rapidly leaves the alveoli, they can collapse if there is nothing left behind

Front 9

Whose law does the concentration effect demonstrate?

Back 9

Fick's Law- If you have a high concentration of agent that wants to diffuse down its concentration gradient and leave the alveoli to enter the blood, it will exit and pull more agent down into the alveoli as it does

Front 10

The rate of rise of the FA/FI ratio is a way of describing:

Back 10

How fast the drug reaches equilibrium

Front 11

Define the second gas effect:

Back 11

The ability of a large volume uptake of one gas to accelerate the rate of rise of a concurrently administered second gas- as the first gas diffuses out of the alveoli because of its large concentration gradient, it concentrates the second gas in a smaller volume (increases its relative partial pressure)

Front 12

The second gas effect is the opposite of:

Back 12

Diffusion hypoxia

Front 13

The effects of alveolar ventilation on the rate of rise of anesthetic are more pronounced for ________ agents

Back 13

Soluble

Front 14

Does hyperventilation work to increase the Pbr?

Back 14

Not necessarily- hyperventilation will increase the partial pressure of gas, but may be offset by the decreased delivery to the brain caused by vasoconstriction and decreased cerebral blood flow (from low PaCO2)

Front 15

The solubility of agents is defined by the ________ and is _______ dependent

Back 15

Partition coefficient and is temperature dependent (37 degrees unless otherwise stated)

Front 16

Define the partition coefficient:

What does a blood:gas partition coefficient of 2 mean?

Back 16

Distribution ration describing how the inhaled anesthetic distributes itself between the two phases at equuilibrium.

There is twice as much gas disolved in blood as in the gas phase at equilibrium

Front 17

What is the MAC, blood:gas partition coefficient, and percent metabolized of isoflurane?

Back 17

Iso: Mac 1.15, blood gas coefficient 1.4, 0.2% metabolized

Front 18

What is the MAC, blood:gas partition coefficient, and percent metabolized of Sevoflurane?

Back 18

Sevo: Mac 2, blood gas coefficient 0.6, and percent metabolized is 3-5%

Front 19

What is the MAC, blood:gas partition coefficient, and percent metabolized of Desflurane?

Back 19

Des Mac: 6.6%, Blood gas coeffiicient 0.42, percent metabolized 0.02%

Front 20

What is the MAC, blood:gas partition coefficient, and percent metabolized of Nitrous?

Back 20

MAC 105%, blood gas coefficient 0.47, percent metabolized=0

Front 21

What does a high blood solubility mean?

What does a low blood solubility mean?

Back 21

A large amount of anesthetic must be dissolved in blood before equilibrium is reached with the gas phase; low blood solubility means that a small amount of anesthetic needs to be dissolved in blood before equilibrium is reached with the gas phase

Front 22

What effect does a low hematocrit have on blood gas solubility?

Back 22

It decreases the blood gas solubility- there is less hemoglobin for the anesthetic to bind to and decreases the effect of this physiologically inactive reservoir- so the drug will have a greater response

Front 23

What effect does a recent fatty meal have on blood gas solubility?

Back 23

It increases the blood gas solubility by 20-25% because anesthetics are very lipid soluble- this decreases the effectiveness of the agent or requires more to acheive the same effect

Front 24

What is a time constant? How many time constants are required to acheive equilibrium?

Back 24

Time constant is the time required to achieve a 63% change in concentration between tissue and arterial blood

Front 25

What is the tissue: blood coefficient?

Back 25

A calculated value representing the amount of anesthetic that can be dissolved in each tissue divided by the tissue blood flow

Front 26

Maintaining the pressure of anesthetic in the alveoli for ______ minutes assures that the anesthetic has had time to equilibrate with the brain because of the ________ coefficient

Back 26

15 minutes; tissue: blood coefficient (at least 3 time constants)

Front 27

What partition coefficient parallels MAC? What is the formula?

Back 27

oil:gas partition coefficient parallels MAC; formula is 150/oil:gas coefficient=MAC

Front 28

Nitrous is ______ times more soluble than Nitrogen, which means that it can difuse into airfilled spaces ______ than Nitrogen can diffuse out. What does this cause?

Back 28

34 times more soluble; diffuses into air filled spaces much faster than Nitrogen can diffuse out. This causes increased volume if there is a compliant wall, or increased pressure if there is a rigid wall

Front 29

Name some examples of when Nitrous use is contraindicated

Back 29

Pneumothorax, 10 weeks following air bubble insertion into eyes for retinal detatchment surgery, pneumocephaly, air embolism, intestinal gas, middle ear infection, pulmonary hypertension (increases pulmonary vascular resistance)

Front 30

The magnitude of volume of pressure change caused by Nitrous diffusion into air filled spaces is determined by what 3 factors?

Back 30

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