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FA2 Anesthesiology > Lecture 8 9/10/24 > Flashcards

Lecture 8 9/10/24 Flashcards

1
Q

Which halogenated ethers are most commonly used in vet med?

A

-isoflurane
-sevoflurane

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2
Q

What are the characteristics of an ideal anesthetic?

A

-chemically stable
-non-flammable
-environmentally friendly
-inexpensive
-easy delivery
-potent
-low solubility
-minimal metabolism
-minimal toxicity
-minimal side effects
-analgesia

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3
Q

Which state are modern inhalants in?

A

vapors

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4
Q

What are the physiochemical properties of solubility?

A

-dissolved concentration in liquid
-net movement of gas into liquid until equilibrium
-temperature dependent

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5
Q

What are the physiochemical properties of partial pressure?

A

-pressure the gas exerts to escape from solution
-each gas exerts a pressure
-mixture of gases = partial pressure the same for individual gases

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6
Q

How do anesthetics travel?

A

via partial pressure gradient

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7
Q

What is the gas partition coefficient?

A

-concentration ratio of anesthetic in gas vs liquid or between two tissues
-describes capacity of particular solvents/tissues to dissolve anesthetic gas

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8
Q

Why is the gas partition coefficient important?

A

it provides means of predicting speed of induction, recovery, and change in depth

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9
Q

How does rate of rise of alveolar partial pressure relate to solubility?

A

inversely proportional

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10
Q

Why do highly soluble anesthetics take a longer time to rise in alveolar partial pressure?

A

because the anesthetic is rapidly taken up by the blood and held there

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11
Q

What does P-alveolar represent?

A

P-CNS

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12
Q

Why do poorly soluble anesthetics have a quick rise in alveolar partial pressure?

A

the gas passes through the blood and right into the brain

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13
Q

Why is a low blood:gas partition coefficient desirable?

A

it leads to faster induction and recovery

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14
Q

What are the characteristics of the oil:gas partition coefficient?

A

-ratio of anesthetic in oil compared to gas at equilibrium
-more lipid soluble = more rapidly taken up by brain

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15
Q

How does oil:gas partition coefficient relate to potency?

A

direct correlation

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16
Q

What is the primary goal of inhalant anesthetic delivery?

A

ensure adequate partial pressure of anesthetic in the CNS to produce CNS depression and general anesthesia

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17
Q

What is important about the pathway in the body that anesthetic inhalants follow?

A

they do not go to the liver or kidneys; there is no hepatic or renal metabolism

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18
Q

What are the characteristics of inhalant uptake?

A

-PA rapidly equilibrates with arterial partial pressure (Pa)
-Pa rapidly equilibrates with Pbrain
-PA useful indicator of brain partial pressure

19
Q

Which factors affect inhalant uptake?

A

-delivery to the alveoli
-uptake by the blood

20
Q

What aspects of inspired inhalant concentration impact delivery to the alveoli?

A

-vaporizer setting
-fresh gas flow
-volume of the anesthesia circuit
-type of anesthetic circuit
-rubber and plastic in the circuit

21
Q

How can the inspired concentration be increased?

A

-increase vaporizer setting
-increase fresh gas flow
-decrease volume of anesthesia circuit
-changing plastic vs. rubber content

22
Q

What is the overpressure technique?

A

using high O2 setting and high vaporizer setting to start anesthesia in order to achieve a quick rise in alveolar concentration

23
Q

What are the characteristics of alveolar ventilation?

A

-improving alveolar ventilation leads to more rapid induction
-want to decrease dead space ventilation

24
Q

Which factors impact blood uptake of inhalant anesthetics?

A

-solubility
-cardiac output
-alveolar to venous anesthetic partial pressure gradient

25
Q

What are the characteristics of solubility?

A

-more soluble = slower rise in anesthetic conc.
-inversely related to potency

26
Q

How does low cardiac output affect uptake?

A

-more rapid rise in alveolar conc.
-less uptake from alveoli to oppose input
-blood becomes concentrated with drug quickly

27
Q

How does high cardiac output affect uptake?

A

-slower rise in alveolar conc.
-increased capacity of blood to hold anesthetic

28
Q

What is the driving force of inhalant uptake and elimination?

A

-partial pressure gradient
-larger gradient = more uptake and longer time to achieve desired PA

29
Q

What are the characteristics of potency?

A

-amount of drug needed to achieve general anesthesia
-inversely related to MAC

30
Q

What is MAC?

A

alveolar concentration that prevents gross, purposeful movement in 50% of patients in response to noxious stim.

31
Q

What are the MAC values for isoflurane and sevoflurane?

A

iso: 1.3
sevo: 2.3

32
Q

How is MAC determined?

A

-using Palveolar expired conc.
-without other drugs
-in healthy animals

33
Q

Which animals have a variation from the standard MAC values?

A

cats - MAC values for iso and sevo are about 0.3 higher

34
Q

Why is MAC important?

A

-anesthetic requirement
-compare agents
-evaluate pharmacologic effects
-want to set vaporizer around MAC value

35
Q

What are the theories behind how inhalant anesthetics work?

A

-modulation of ion channels**
-decreased neuronal excitability
-inhibition of action potential
-enhanced inhibitory synaptic transmission

36
Q

What are the sites of action for inhalant anesthetics?

A

-brain
-spinal cord

37
Q

What are the advantages of using inhalants?

A

-tailored to individual
-rapid changes in depth
-minimal metabolism

38
Q

What are the primary goals of using inhalants?

A

achieve muscle relaxation and hypnosis

39
Q

What are the disadvantages of using inhalants?

A

-necessary equipment
-airway management
-waste gases
-side effects

40
Q

What are the effects of inhalants?

A

-dose dependent hypotension
-decreased ventilatory response to CO2
-dose dependent hypoventilation
-unconsciousness
-decreased cerebral metabolic rate of O2
-increased cerebral blood flow
-increased intracranial pressure
-decreases in renal blood flow and glomerular filtration rate

41
Q

Why is it important to pre-medicate when using inhalants?

A

side effects are dose dependent, so we can reduce the dose of inhalants when pre-medicating

42
Q

What are the characteristics of malignant hyperthermia?

A

-genetic mutation of ryanodine receptor
-use of inhalants can result in hyperthermia, muscle rigidity, increased EtCO2, hypocalcemia, and hyperkalemia
-reversed with dantrolene
-very poor prognosis; nearly always fatal

43
Q

When is trace gas exposure most likely to occur?

A

-vaporizer filling
-leaks
-recovery

FA2 Anesthesiology (23 decks)

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