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Anesthesia MM/TL > Inhalational Anesthetics principals > Flashcards

Inhalational Anesthetics principals Flashcards

1
Q

What is methoxyflurane?

A

A potent halogenated anesthetic with high solubility and low vapor pressure

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2
Q

How was methoxyflurane metabolized?

A

50% by cytochrome P450 into nephrotoxic compounds

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3
Q

What was prolonged anesthesia with methoxyflurane associated with?

A

Vasopressin resistant, high output renal failure

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4
Q

What are the effects of enflurane?

A

Depressed myocardial contractility
Increased CSF
Decreased CSF output
Seizures

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5
Q

What is the ultimate effect of inhalation all anesthetics?

A

Therapeutic tissue concentration in the brain

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6
Q

What is the inspired gas concentration determined by?

A

The fresh gas flow rate
Breathing circuit volume
Circuit absorption

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7
Q

What is the concentration of a gas directly proportional to?

A

It’s partial pressure

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8
Q

Why is the alveolar partial pressure of a gas important?

A

Because it determines the partial pressure of anesthetic in the blood and ultimately the brain.

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9
Q

What is the relationship between uptake and alveolar concentration?

A

The greater the uptake, the greater the difference between inspired and alveolar concentration and SLOWER rate of induction.

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10
Q

What 3 factors affect anesthetic uptake?

A

Solubility in the blood
Alveolar blood flow
The difference in partial pressure between alveolar gas and venous blood.

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11
Q

What does it mean if something is less soluble?

A

Means that it is not taken up in the blood as avidly, meaning that the alveolar concentration will be higher and induction much faster (nitrous oxide)

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12
Q

What is the partition coefficient?

A

The ratio of the concentrations of the anesthetic gas in each of two phases at steady state

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13
Q

What is the blood/gas coefficient of nitrous oxide?

A

0.47 so the blood has 47% capacity of nitrous oxide as alveolar gas

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14
Q

What is the blood/gas coefficient of halothane?

A

2.4

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15
Q

If the blood/gas coefficient is bigger, what does this mean for the anesthetic’s solubility and uptake by the pulmonary circulation?

A

It means it is more soluble and has higher uptake in the pulmonary circulation meaning that the alveolar partial pressure will take awhile to rise, thereby causing slower induction

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16
Q

What is alveolar uptake(blood flow) equal to?

A

Cardiac output

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17
Q

What are the first organs to reach steady state and why?

A

Brain, heart, liver, kidney, and endocrine because they have the high blood flow

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18
Q

How can you increase the alveolar concentration?

A

By increasing the concentration of inspired gas

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19
Q

What is augmented inflow effect?

A

The absorbed gas has be replaced by an equal volume of the mixed gas to prevent alveolar collapse

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20
Q

What is the second gas effect?

A

A high concentration of one gas will augment its own uptake and another volatile anesthetic (nitrous oxide does this)

21
Q

How does ventilation affect the alveolar partial pressure?

A

It will increase it by constantly replacing anesthetic that is being taken up

22
Q

What does VQ mismatch doe to alveolar partial pressure?

A

It increases it, thus making onset faster for soluble agents

23
Q

What happens with the elimination of nitrous oxide?

A

It diffuses so fast that oxygen and co2 are diluted causing a diffusion hypoxia?

24
Q

How do you treat diffusion hypoxia?

A

By administering 100% oxygen for 5-10 minutes after stopping nitrous oxide

25
Q

How are inhalational agents cardio protective?

A

They open the K ATP channel, preventing the influx of calcium and reducing ROS. Therefore reducing ischemia-reperfusion injury

26
Q

What protective property does Xenon have?

A

An anti-apoptotic effect that may be secondary to its inhibition of calcium ion influx following cell injury

27
Q

What happens to MAC as you age per decade?

A

The MAC decreases by 6% regardless of volatile anesthetic

28
Q

What is a MAC of 1.3 correlated with in any of the volatile anesthetics?

A

Prevention of movement in 95% of patients

29
Q

What is a Mac of 0.3-0.4 associated with?

A

Awakening

30
Q

What factors decrease MAC?

A 
Temperature (hypo or hyperthermia)
Old
Acute alcohol intoxication
Hypoxemia
Hypercapnia
Hypotension
Hypercalcemia
Hyponatremia
Pregnancy
31
Q

What factors increase Mac?

A 
Hypernatremia
Cocaine
Ephedrine
Chronic alcohol use
Young age
Temperature over 42 Celsius
32
Q

What is the principal mechanism by which halothane decreases blood pressure?

A

By decreasing cardiac output

33
Q

How do isoflurane, sevoflurane, and desflurane decrease blood pressure?

A

Through decreasing SVR

Cause dose dependent changes in arterial bp, SVR, and co

34
Q

Which anesthetic is metabolized to hexafluoroisopropanolol?

A

Sevoflurane

35
Q

How is sevoflurane metabolized to hexafluoroisopropanolol ?

A

Through p450 enzymes

36
Q

How are desflurane, isoflurane, and sevoflurane mainly eliminated?

A

Unchanged when exhaled out of the lungs

37
Q

What is the order of volatile that undergoes liver metabolism from greatest to least?

A

Halothane > sevoflurane > isoflurane > desflurane

38
Q

What enzyme family is responsible for volatile metabolism in the liver?

A

P450 (CYP2E1)

39
Q

What do desflurane and isoflurane get metabolizes to in the liver?

A

Trifluoroacetic acid

40
Q

What does Trifluoroacetic acid do?

A

Binds hepatocellular proteins and acts as a happen –> immune response

41
Q

What is a rare complication from isoflurane or desflurane?

A

Hepatic necrosis and liver failure from subsequent exposure after immune response on first exposure

42
Q

What 2 types of liver injury are associated with halothane?

A
  1. Mild form : free radical formation by reductive metabolism (CYP2A6 and CYP3A4) (under conditions of hypoxia or decreased flow
  2. Oxidative metabolism and the immunologic response from TFA
43
Q

What does the rate of rise of the FA:Fi ratio depend on?

A

The blood gas solubility
The inspired concentration of gas

Therefore the speed at which the alveolar anesthetic (FA) equilibration with that being delivered to the lungs (Fi).

44
Q

How much inactivation of methionine synthetase do you get from nitrous oxide at 70% for 46 minutes?

A

50%

45
Q

What does halothane do to catecholamines effects on the heart?

A

Sensitized the heart to them so causes arrhythmias

46
Q

Which inhalational agents will have a longer induction with one-lung ventilation

A

Desflurane and nitrous oxide because they have the lowest blood/gas solubility.

One lung ventilation creates a shunt. Less blood is there to take the volatile to the brain. The less soluble agents will just stay in the ventilated lung

47
Q

When cardiac output is doubled what happens to the rate of rise of FA/Fi of a soluble agent?

A

It will slow the rate of rise

48
Q

What happens to rate of rise for insoluble agents in a shunt?

A

Slow the rise

Anesthesia MM/TL (36 decks)

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