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Pharmacology #1 > Module B-1 (gases) > Flashcards

Module B-1 (gases) Flashcards

1
Q

Cerebral vasculature response to CO2

A

Hypocapnia-vasoconstrict
Hypercarbia-vasodilate

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2
Q

Sevoflurane
-MAC
-B/G coefficient
-oil/gas coefficient

A

2%
0.6
50

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3
Q

Isoflurane

-MAC
-B/G coefficient
-oil/gas coefficient

A

1.15%
1.4
99

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4
Q

Nitrous oxide

-MAC
-B/G coefficient
-oil/gas coefficient

A

105%
0.47
1.4

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5
Q

Desflurane

-MAC
-B/G coefficient
-oil/gas coefficient

A

5.8%
0.42
18.7

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6
Q

Factors that increase MAC

A

Hyperthermia
Hypernatremia
Increase in CNS activity (drug induced)
Chronic alcohol abuse

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7
Q

Factors that decrease MAC

A

Hypothermia
Increased age
Preoperative sedatives
Alpha-2 agonists
Pregnancy
Acute alcohol
Hyponatremia
Hypotension

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8
Q

MAC

A

Minimum Alveolar Concentration
Analogous to ED50- given in volume% needed to produce lack of movement with surgical stimulation

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9
Q

Blood/Gas solubility coefficient

A

Higher the solubility the higher the coefficient
-this means more gas is bound in blood and not being utilized at effect site

Isoflurane is 1.4 and nitrous is 0.47, which has faster induction??

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10
Q

Pros/Cons of manipulating minute ventilation

A

Pro: faster Ve (minute ventilation)= faster induction

Con: faster Ve= drop in PaCO2= cerebral perfusion and slower drug delivery to brain

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11
Q

Overpressuring

A

Similar to a loading dose
Initially administering a higher concentration of gas than would be needed to maintain anesthesia

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12
Q

Second Gas Effect

A

A high volume first gas (N20) accelerates the rate of rise of a second gas (Isoflurane)

N2O changes the concentration of gases in the alveoli-facilitating diffusion into blood

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13
Q

Cardiac output and induction speed

A

High CO slows rise in alveolar concentration because it rapidly removes drug

PA=Pbrain

Drug is rapidly distributed to the tissues and more slowly to the brain

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14
Q

Oil/Gas solubility coefficient

A

Lipid solubility of an anesthetic gas
-ability to access CNS
-indicator of potency

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15
Q

Hypothermia

A

Solubility and potency both increase- negate each other

Slowed recovery- decreased perfusion and increased tissue capacity or anesthetics

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16
Q

Diffusion hypoxia

A

With abrupt discontinuation of nitrous, it floods the alveoli-displacing normal respiratory gases during a rapid exit from the body
1-5 minutes post discontinuation
-admin 100% 02 to negate this effect

17
Q

Obesity considerations with inhaled anesthetics

A

Higher ratio of fat to lean mass leads to a larger reservoir for anesthetics to accumulate. Using anesthetic with low tissue:blood coefficient like desflurane can mitigate
-rate of induction should not be impacted

18
Q

Fractional mass

A

Ratio for mass of a substance to the total mass of the mixture

O2 is 21% or 0.21 of normal air

19
Q

Daltons Law

A

Partial pressures of a gases in a mixture are independent from one another

Ptotal=P1+P2+P3…

20
Q

Henry’s Law

A

Concentration of gas= Partial Pressure x solubility coefficient

Think: Mixture of gas and liquid- the pressure is the same in both phases but the concentration changes based on the gas solubility

21
Q

How do we know the level of anesthetic in the brain??

A

At equilibrium:

Brain =Arterial =Alveolar partial pressure

Easily measured via end tidal sampling

22
Q

Factors that influence Anesthetic Transfer

A

Machine
drug
Ventilation
Tissue

23
Q

Where can anesthetic be lost in the “breathing system”

A

Absorption in plastic components
CO2 absorbents theoretically degrade anesthetic

24
Q

Factors that lead to faster induction/higher concentration in alveolus- machine factors

A

Higher concentration (set on machine)
Lower circuit absorption
Lower circuit volume
Higher Fresh Gas Flow

25
Q

Why is nitrous so high on the Fa/Fi curve?

A

It has a low blood/gas coefficient but it is also given in much higher concentrations than our other anesthetics

26
Q

Fastest to slowest induction based on Blood/gas coefficient

A

Desflurane 0.42
Nitrous oxide 0.47
Sevoflurane 0.6
Isoflurane 1.4

Ether is 14! Holy fuck

27
Q

Prolonged emergence in hypothermic patients

A

Gas solubility in liquids is inversely proportional to temperature

-think boiling water
-cold humans=more soluble gases

28
Q

Why not nitrous?

A

It’s propensity to fill airspaces in the body and equipment via diffusion
-pneumos will worsen

29
Q

Functional Residual Capacity

A

Volume of gas present in the lungs at end expiration during normal tidal breathing

30
Q

Impact of FRC on anesthesia onset

A

Large FRC dilutes concentration of anesthetic- slower onset time

31
Q

Left to right shunt

A

Blood recirculates through the lungs, less impact on IA concentration

32
Q

Right to left shunt

A

Returning Venous blood bypasses the lungs-

Soluble anesthetics can partially compensate because they are taken into the blood more easily

Problematic for insoluble gases

33
Q

Oil:gas & MAC relationship

A

The higher the coefficient the lower the MAC because it is a more potent drug (requiring less)

34
Q

% hepatic biotransformation of IA’s in order

A

No Nitric Oxide 0.004
Dick Desflurane 0.02
Is Isoflurane 0.2
Salacious Sevoflurane 2-5

Pharmacology #1 (15 decks)

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