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Pharmacology & Anesthesiology > Inhalant General Anesthetics > Flashcards

Inhalant General Anesthetics Flashcards

1
Q

Nitrous oxide does not cause unconsciousness… why is it used?

A

Excellent analgesic and alleviates anxiety; can also reduce amount of hydrocarbon anesthetic needed

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2
Q

all inhalant anesthetics by the early 1950s had at least one of what two major drawbacks

A

1) explosive when administered with oxygen
2) produce toxic metabolites

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3
Q

how do we reduce the flammability of a hydrocarbon

A

by substituting their hydrogen for a halogen

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4
Q

halothane-oxygen mixtures are explosive/non-explosive

A

non-explosive

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5
Q

in general, hepatic and renal toxicity are directly related to the extent at which an inhalant is

A

metablolized

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6
Q

what are the main inhalants used in veterinary medicine today

A
  • isoflurane
  • sevoflurane
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7
Q

the TI of all hydrocarbons ranges from

A

2-4

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8
Q

why do we not use newer inhalant anesthetics?

A

they offer little or no advantage over iso or have serious drawbacks

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9
Q

To be both safe and effective, general anesthetics must (2)

A

inhibit cerebrocortical activity while maintaining brainstem function

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10
Q

the safety of general anesthetics is dependent on

A

the extent to which CVS and respiratory functions are impaired at concentrations required to maintain unconsciousness

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11
Q

what is the MOA of inhalant anesthetics

A

not fully understood, but involves GABA facilitation

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12
Q

how is inhalant anesthetic absorbed and eliminated

A

absorbed into blood from lungs; eliminated mainly be exhalation

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13
Q

depth of anesthesia is proportional to:

A

partial pressure of the anesthetic

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14
Q

what is partial pressure

A

the physical pressure exerted by one gas (in a mixture of gases) within a container

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15
Q

how do highly soluble gases influence partial pressure and overall effect

A

highly soluble -> move slowly in tissues (because they form bonds) -> weak partial pressure and weak effect

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16
Q

how fast do highly soluble gases get absorbed and eliminated

A

absorbed quickly; eliminated slowly

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17
Q

rate of onset and recovery depends on

A

partial pressure

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18
Q

how do poorly soluble gases influence partial pressure and overall effect

A

move rapidly in tissues -> high partial pressure -> high overall effect

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19
Q

how fast do poorly soluble gases get absorbed and eliminated

A

slowly absorbed; quickly eliminated

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20
Q

will a high or low soluble anesthetic render a patient unconscious more quickly (assuming a high concentration gradient to force the anesthetic into the tissue)

A

low soluble (because it has a higher partial pressure)

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21
Q

will a patient recover more quickly if given an anesthetic with high or low solubility

A

low

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22
Q

how do we overcome the problem of getting a poorly soluble inhalant anesthetic drug into the body

A

by creating a high concentration gradient between the capillaries and alveoli

23
Q

what is the blood gas parturition coefficient

A

the relative solubility of drug in tissues vs alvgeolar gas

24
Q

what is the BGPC for:
- sevoflurane
- isoflurane

A

sevoflurane: 0.68
isoflurane: 1.4

25
Q

how can we determine the concentration of anesthetic that is present in the brain

A

multiply the concentration of inhalant anesthetic being delivered by the BGPC

26
Q

the BGPC for isoflurane is 1.4, what does this mean?

A

the concentration of iso in the tissues is 1.4x the concentration in the alveolar air

or

if you administer 1% iso, the concentration in tissues is 1.4%

27
Q

the onset of unconsciousness and recovery are fast with __________ drugs and slow with __________ drugs

A

poorly-soluble; highly-soluble

28
Q

how do we utilize the concentration of anesthetic in the inspired air to induce a patient more quickly

A

can increase (so more enters tissue with each breath) and then decrease once the patient is unconscious

29
Q

T/F we can control the inspired anesthetic concentration using a precision vaporizer

A

T

30
Q

how does ventilation rate impact the concentration of anesthetic in the brain

A

the faster the patient breathes, the faster the anesthetic is delivered to and absorbed from the lungs

31
Q

what are 2 factors that influence inhalant anesthetic delivery to the brain that we cannot readily control

A

1) pulmonary blood flow
2) pulmonary/venous concentration gradient

32
Q

what are 3 factors that influence drug delivery to the brain that we can readily control

A

1) BGPC
2) concentration of anesthetic in the inspired air
3) ventilation rate

33
Q

inhalant anesthetics are eliminated mainly by

A

exhalation

34
Q

what are 3 factors that influence the elimination of an inhalant anesthetic

A

1) solubility in tissues
2) respiratory rate
3) pulmonary blood flow

35
Q

what effect do inhalant anesthetics have on thermoregulation

A

depress -> cause some degree of hypothermia

36
Q

halothane has ~25-40% metabolism, isoflurane has ~0.2% metabolism and sevoflurane has ~3-5% metabolism

place the drugs in order of most to least toxic

A

halothane, sevoflurane, isoflurane

37
Q

metabolites of inhalant anesthetic metabolism are usually damage to what organs

A

liver and kidney

38
Q

what are 3 harmful metabolites of inhalant anesthetics

A

1) trifluoroacetic acid
2) Br-
3) Cl-

39
Q

what is used to compare potency of inhalant anesthetics

A

MAC

40
Q

what is MAC50

A

concentration of anesthetic in the inspired air that will prevent 50% of patients from feeling a painful stimulus

41
Q

the MAC for very potent drugs would be relatively (high/low)

A

low

42
Q

what is used to control the vaporizer setting

A

MAC50

43
Q

The MAC95 value is about _____% higher than MAC50, so in unpremedicated patients you should set the vaporizer at ____x MAC to start, then adjust

A

30-40%; 1.3x

44
Q

what do we set the vaporizer to in premedicated patients to start

A

MAC50 value

45
Q

lines in what species are susceptible to malignant hyperthermia

A

pigs, dogs and humans

46
Q

malignant hyperthermia is caused by mutations in the

A

skeletal muscle calcium release channel (RYR)

47
Q

what happens to mutated calcium release channels when exposed to halogenated hydrocarbons

A

uncontrolled muscle contraction

48
Q

how do we treat malignant hyperthermia

A

dantrolene

49
Q

why is it important to change out soda lime regularly when using iso as the inhalant anesthetic

A

it forms CO when exposed to desiccated CO2 absorbents

50
Q

what is a drawback of iso that is only important when the patient is not being stimulated

A

dose-dependent drop in blood pressure

51
Q

what is isoflurane’s only real drawback

A

pungent odour

52
Q

is it better to use isoflurane or sevoflurane on reptiles and amphibians

A

sevoflurane (because they can hold their breath for over 20 min)

53
Q

what happens to sevoflurane when exposed to CO2 absorbents

A

releases Compound A, which is nephrotoxic

Pharmacology & Anesthesiology (22 decks)

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