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Anesthesia Fast Facts > Inhaled Anesthetics > Flashcards

Inhaled Anesthetics Flashcards

1
Q

Has a MAC of 104

A

Nitrous Oxide

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2
Q

Has a MAC of .75

A

Halothane

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3
Q

Has a MAC of 1.63

A

Enflurane

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4
Q

Has a MAC of 1.17

A

Isoflurane

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5
Q

Has a MAC of 6.6

A

Desflurane

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6
Q

Has a MAC of 1.80

A

Sevoflurane

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7
Q

In what anesthetic is a preservative necessary?

A

Halothane

contains 0.01 (w/w) thymol as a preservative

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8
Q

Has a sweet odor?

A

Nitrous Oxide

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9
Q

Is not stable in soda lime absorbent?

A

Halothane & Sevoflurane

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10
Q

Blood:Gas partition coefficient of 0.46

A

Nitrous Oxide

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11
Q

Blood:Gas partition coefficient of 2.54

A

Halothane

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12
Q

Blood:Gas partition coefficient of 1.90

A

Enflurane

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13
Q

Blood:Gas partition coefficient of 1.46

A

Isoflurane

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14
Q

Blood:Gas partition coefficient of 0.42

A

Desflurane

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15
Q

Blood:Gas partition coefficient of 0.69

A

Sevoflurane

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16
Q

669 Vp @ 20C

A

Des

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17
Q

157 Vp @ 20C

A

Sevo

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18
Q

238 Vp @ 20C

A

Iso

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19
Q

243 Vp @ 20C

A

Hal

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20
Q

SVP Hi-Se

A

Hal & Iso ~ 240

Sevo & Enf ~ 160

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21
Q

immobilizing effects of IAs involves action on the _____

sedation/hypnosis/amnesia involves actions _______

A

spinal cord

supraspinal - brain and brainstem

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22
Q

Unconsiousness

A

glutamate blockade

-cortex, thalamus, brainstem

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23
Q

Amnesia

A

GABAa

-amygdala, hippocampus

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24
Q

Analgesia

A

NMDA, K2p & AMPA

-spinothalamic tract

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25
Q

Immobility

A

Glycine receptors

-spinal cord central pattern generators

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26
Q

SVP of an inhaled anesthetic depends on?

A

Temperature

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27
Q

Time constants

A

type of measurement used to determine time to reach equilibration of anesthetic gas between PA and Pbrain

  • 1 TC = 63% equilibration
  • 3 TC = 95%
  • 4 TC = 98%
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28
Q

How to calculate Time Constants

A

the capacity of the system (L)
/
total flow to the system (L/min)

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29
Q

Recovery depends on?

A
  • solubility, tissue uptake, duration of admin

aka: context-sensitive half time

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30
Q

Effects of a R>L & L>R shunt on Pa of inhaled anesthetics

A

Right to Left (volatile): slower induction

Left to Right (volatile): little effect on induction

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31
Q

Inhaled anesthetics with increased context sensitive half time?

A

Halothane and Isoflurane after administration > than 30 min - 1hr.

Des and Sevo only minimally

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32
Q

MAC is a measure of?

A

Potency

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33
Q

MAC values for multiple co-administered anesthetics are:

A

Additive

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34
Q

MAC values administered with opioids are:

A

Synergistic

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35
Q

VA that causes the most airway irritation?

A

Des

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36
Q

Increases incidence of arrhythmias?

A

Halothane

-due to decreasing threshold at which catecholamines will cause ventricular ectopy

dysrhythmias occur H > I > D&S

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37
Q

metabolism can lead to hepatotoxicity when using?

A

Halothane

All around bad for the liver:
halothane hepatitis, hepatocyte hypoxemia, decreased hepatic artery blood flow, and metabolized to a protein that may produce liver injury

38
Q

CO toxicity is most likely using?

A

Desflurane

-caused by rxn of CHF2 and the strong bases present in the absorbents

39
Q

IA general effects: Neuro

A
  • decrease CMRo2

- increase CBF, increase ICP

40
Q

IA general effects: Pulm

A
  • increase RR and decrease TV, rapid shallow breathing
  • bronchodilation & decreased airway resistance
  • depress hypercapnia and hypoxia response
41
Q

IA general effects: CV

A

-decrease SVR via vasodilation (but preserve CO via reflex increase in HR)

42
Q

An abrupt and large increase in the delivered concentration of this IA may produce transient increase SBP and HR

A

Des

-has the most SNS activity

43
Q

IA associated with nephrotoxic Compound A

A

Sevo

-no evidence that it produces a level that is nephrotoxic

44
Q

IA general effects: OB

A

-all decrease uterine blood flow and uterine contractility (cause uterine relaxation)

45
Q

IA speculated role in spontaneous abortions?

A

N20

46
Q

Max levels of trace gas in atmosphere

A

Halogenated alone: 2 ppm
Nitrous alone: 25 ppm

Combo: Nitrous 25 ppm + Halogenated 0.5 ppm

47
Q

IA general effects: Renal

A

-decrease renal blood flow, GFR, urine output

48
Q

IA general effects: Hepatic

A

-decrease hepatic blood flow and O2 delivery

49
Q

the anesthetic with the possible complication: inhibits methionine synthetase

A

N20

50
Q

the anesthetic with the possible complication: metabolism results in free fluoride ions in the blood

A

sevo

51
Q

the anesthetic with the possible complication: may result in junctional rhythm or AV nodal dissociation at higher mac doses

A

iso

dysrhythmias occur H > I > D&S

52
Q

contraindicated in trauma pts with rib fractures

A

n2o

53
Q

best for inhalation inductions

A

sevo

54
Q

may cause HTN and Tachy d/t SNS stimulation

A

des

55
Q

Contraindicated in neurosurgery

A

high dose inhalation anesthesia > 1 MAC

-increases ICP

56
Q

VAs cause a rise in arterial CO2 levels because they slow down the respiratory rate? T/F

A

false

-decreased TV increased RR
“panting”
-decrease in alveolar min. ventilation

57
Q

Sevo in an Iso vaporizer, would the actual output be more or less than what it is set at?

A

Less

Sevo has a lower SVP so the output would be lower

58
Q

What primarily determines mechanical dead space in a Mapelson circuit?

A

the FGF rate

59
Q

What breathing circuit system has complete rebreathing?

A

Closed circuit system

60
Q

Which Mapelson circuit has no bag and no APL valve?

A

E

61
Q

Best IA for liver failure pts?

A

Isoflurane

62
Q

Which of the volatile agents has the least effect on intracranial pressure?

A

Des
Iso
Sevo

-all the modern inhaled anesthetics

63
Q

Of the volatile agents which has the greatest potentiation of neural muscular junction blockade?

A

Des

64
Q

Metabolism plays an important role on the rate of rise of FA/FI during induction of anesthesia for which volatile anesthetics?

A

NONE

65
Q

VA effects on neuromonitoring

A

EEG - dose-dependent changes in Hz, initially increases, then Hz lowers with higher amplitude, then burst suppression, then isoelectic

SSEP: decreases amplitude and increases latency

MEP: very sensitive to depression by volatile anesthetics. Use TIVA if able.

66
Q

T/F VAs enhance ischemic preconditioning

A

True

exposure to a single/brief episode can confer a protective effect on the myocardium against reversible or irreversible injury with a subsequent prolonged ischemia insult - works via mitochondrial ATP sensitive K+ channels

67
Q

SNS stimulation, order VAs most to least

A

Des > Iso > Sevo > Hal

N2O also increases SNS stimulation

68
Q

Gas that increases PONV

A

N20

69
Q

These patient factors affect pharmacokinetics of VAs

A
  • aging
  • decrease in lean body mass
  • increase in body fat
  • impaired pulmonary exchange
  • reduced CO

-opposite effects in very young

70
Q

2nd gas effect

A

ability of high volume uptake of one gas to accelerate the uptake of a second gas due to the resulting higher concentration of the 2nd gas in a smaller lung volume

71
Q

Concentration effect

A

the greater the inspired concentration (Fi) the greater the rate of rise (Fa/Fi)

72
Q

What is the relevance of oil:gas coefficients?

A
  • they parallel anesthetic requirements

- MAC is calculated as = 150 / the o:g

73
Q

rate of rise VS solubility

A

Inversely proportional

The more soluble the agent is the slower the rate of rise of PA/Pi (because the blood absorbs more of the agent)

74
Q

Diffusion Hypoxia

A

Occurs when inhalation of nitrous oxide is discontinued abruptly which reverses partial pressure gradients which causes N2O to leave the blood and rapidly reenter alveoli - which results in dilution of PaO2 available for arterial blood to absorb resulting in arterial hypoxemia

75
Q

What is MAC

A

Minimal alveolar concentration: The concentration of the gas in the lungs that is needed to prevent movement (motor response) in 50% of subjects in response to surgical incision (noxious) stimulus

76
Q

Rank MAC values from High to Low

A 
N2o 104
Xenon 63-71
Des 6.6
Sevo 1.8
Enflurane 1.63
Iso 1.17
Hal 0.75
77
Q

MAC required for immobility

A

2.5-4x MAC (which is a lot)

78
Q

MAC BAR

A

“Blunt Autonomic Responses” = BAR

Typically 30-50% greater than MAC

1.3-1.5 MAC or for Sevo 2x MAC

79
Q

Things that affect the pressure of inspired gas and uptake

A
  1. CO
  2. Blood:Gas solubility
  3. (PA - PV) = Alveolar to venous partial pressure gradient mm Hg (% gas)
  4. Bp = barometric pressure mmHg
80
Q

Why is the uptake of VAs faster in infants?

A
  1. higher alveolar ventilation
  2. smaller FRC
  3. greater proportion of CO to VRG (brain)
  4. IAs are less soluble in infants bc they have a higher water content
81
Q

How does Henry’s Law apply to uptake of anesthetics?

A

At 37C, the amount of gas that dissolves into the blood is directly proportional to the partial pressure of the gas in contact with the blood.

Think higher partial pressure = higher concentration gradient

82
Q

What is the Meyer-Overton Correlation

A

potency of an anesthetic agent is proportional to lipid solubility as measured by its oil-gas partition coefficient

83
Q

Which anesthetics blunt autoregulation of cerebral vasculature?

A
  • at 1 MAC halothane blunts autoregulation
  • des and sevo do not alter autoregulation
  • des may at >1.5 MAC)
84
Q

the anesthetic with the possible complication: emergence delirium in peds

A

Sevo

85
Q

T/F VAs induce coronary vasodilation?

A

True

86
Q

What is the apneic threshold?

A

the highest arterial carbon dioxide tension at which a pt remains apneic

it is approximately 4 or 5 mm Hg less than resting arterial carbon dioxide tension achieved during spontaneous ventilation

ex: pt will spont breath at Co2 of 55 but won’t at 51.

87
Q

What is a possible complication of the bronchodilator effects of VAs?

A

Inhaled anesthetic agents inhibit HPV (hypoxic pulmonary vasoconstriction) which is a reflex vasoconstriction in the pulmonary circulation in response to a low regional partial pressure of oxygen to reduce V/Q mismatching

VAs could worsen V/Q mismatching if vascular beds are vasldilated

Usually negligible

88
Q

the anesthetic with the possible complication: MH

A

-halothane is the most potent trigger of MH, but all VAs can trigger MH

  • Xenon can be given safely to a pt with MH
  • N2o does NOT trigger MH
89
Q

Metabolism of Des in a dry Co2 absorber can produce?

A

can create CO

90
Q

Biotransformation of ____ produces Free Fluoride Ions

A

Sevo - but no evidence of renal failure

91
Q

T/F: VAs enhance the activity of succinylcholine but NOT non-depolarizing NMBs?

A

False

They enhance both and cause dose related skeletal muscle relaxation

92
Q

N2o effects on pulmonary vasculature

A

-increases pulmonary vascular resistance and should be avoided in patients with pulmonary HTN

Anesthesia Fast Facts (24 decks)

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