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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
Immobility
Glycine receptors | -spinal cord central pattern generators
26
SVP of an inhaled anesthetic depends on?
Temperature
27
Time constants
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%
28
How to calculate Time Constants
the capacity of the system (L) / total flow to the system (L/min)
29
Recovery depends on?
- solubility, tissue uptake, duration of admin | aka: context-sensitive half time
30
Effects of a R>L & L>R shunt on Pa of inhaled anesthetics
Right to Left (volatile): slower induction Left to Right (volatile): little effect on induction
31
Inhaled anesthetics with increased context sensitive half time?
Halothane and Isoflurane after administration > than 30 min - 1hr. Des and Sevo only minimally
32
MAC is a measure of?
Potency
33
MAC values for multiple co-administered anesthetics are:
Additive
34
MAC values administered with opioids are:
Synergistic
35
VA that causes the most airway irritation?
Des
36
Increases incidence of arrhythmias?
Halothane -due to decreasing threshold at which catecholamines will cause ventricular ectopy dysrhythmias occur H > I > D&S
37
metabolism can lead to hepatotoxicity when using?
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
CO toxicity is most likely using?
Desflurane -caused by rxn of CHF2 and the strong bases present in the absorbents
39
IA general effects: Neuro
- decrease CMRo2 | - increase CBF, increase ICP
40
IA general effects: Pulm
- increase RR and decrease TV, rapid shallow breathing - bronchodilation & decreased airway resistance - depress hypercapnia and hypoxia response
41
IA general effects: CV
-decrease SVR via vasodilation (but preserve CO via reflex increase in HR)
42
An abrupt and large increase in the delivered concentration of this IA may produce transient increase SBP and HR
Des -has the most SNS activity
43
IA associated with nephrotoxic Compound A
Sevo -no evidence that it produces a level that is nephrotoxic
44
IA general effects: OB
-all decrease uterine blood flow and uterine contractility (cause uterine relaxation)
45
IA speculated role in spontaneous abortions?
N20
46
Max levels of trace gas in atmosphere
Halogenated alone: 2 ppm Nitrous alone: 25 ppm Combo: Nitrous 25 ppm + Halogenated 0.5 ppm
47
IA general effects: Renal
-decrease renal blood flow, GFR, urine output
48
IA general effects: Hepatic
-decrease hepatic blood flow and O2 delivery
49
the anesthetic with the possible complication: inhibits methionine synthetase
N20
50
the anesthetic with the possible complication: metabolism results in free fluoride ions in the blood
sevo
51
the anesthetic with the possible complication: may result in junctional rhythm or AV nodal dissociation at higher mac doses
iso dysrhythmias occur H > I > D&S
52
contraindicated in trauma pts with rib fractures
n2o
53
best for inhalation inductions
sevo
54
may cause HTN and Tachy d/t SNS stimulation
des
55
Contraindicated in neurosurgery
high dose inhalation anesthesia > 1 MAC -increases ICP
56
VAs cause a rise in arterial CO2 levels because they slow down the respiratory rate? T/F
false -decreased TV increased RR "panting" -decrease in alveolar min. ventilation
57
Sevo in an Iso vaporizer, would the actual output be more or less than what it is set at?
Less Sevo has a lower SVP so the output would be lower
58
What primarily determines mechanical dead space in a Mapelson circuit?
the FGF rate
59
What breathing circuit system has complete rebreathing?
Closed circuit system
60
Which Mapelson circuit has no bag and no APL valve?
E
61
Best IA for liver failure pts?
Isoflurane
62
Which of the volatile agents has the least effect on intracranial pressure?
Des Iso Sevo -all the modern inhaled anesthetics
63
Of the volatile agents which has the greatest potentiation of neural muscular junction blockade?
Des
64
Metabolism plays an important role on the rate of rise of FA/FI during induction of anesthesia for which volatile anesthetics?
NONE
65
VA effects on neuromonitoring
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
T/F VAs enhance ischemic preconditioning
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
SNS stimulation, order VAs most to least
Des > Iso > Sevo > Hal N2O also increases SNS stimulation
68
Gas that increases PONV
N20
69
These patient factors affect pharmacokinetics of VAs
- aging - decrease in lean body mass - increase in body fat - impaired pulmonary exchange - reduced CO -opposite effects in very young
70
2nd gas effect
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
Concentration effect
the greater the inspired concentration (Fi) the greater the rate of rise (Fa/Fi)
72
What is the relevance of oil:gas coefficients?
- they parallel anesthetic requirements | - MAC is calculated as = 150 / the o:g
73
rate of rise VS solubility
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
Diffusion Hypoxia
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
What is MAC
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
Rank MAC values from High to Low
``` N2o 104 Xenon 63-71 Des 6.6 Sevo 1.8 Enflurane 1.63 Iso 1.17 Hal 0.75 ```
77
MAC required for immobility
2.5-4x MAC (which is a lot)
78
MAC BAR
"Blunt Autonomic Responses" = BAR Typically 30-50% greater than MAC 1.3-1.5 MAC or for Sevo 2x MAC
79
Things that affect the pressure of inspired gas and uptake
1. CO 2. Blood:Gas solubility 3. (PA - PV) = Alveolar to venous partial pressure gradient mm Hg (% gas) 4. Bp = barometric pressure mmHg
80
Why is the uptake of VAs faster in infants?
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
How does Henry's Law apply to uptake of anesthetics?
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
What is the Meyer-Overton Correlation
potency of an anesthetic agent is proportional to lipid solubility as measured by its oil-gas partition coefficient
83
Which anesthetics blunt autoregulation of cerebral vasculature?
- at 1 MAC halothane blunts autoregulation - des and sevo do not alter autoregulation - des may at >1.5 MAC)
84
the anesthetic with the possible complication: emergence delirium in peds
Sevo
85
T/F VAs induce coronary vasodilation?
True
86
What is the apneic threshold?
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
What is a possible complication of the bronchodilator effects of VAs?
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
the anesthetic with the possible complication: MH
-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
Metabolism of Des in a dry Co2 absorber can produce?
can create CO
90
Biotransformation of ____ produces Free Fluoride Ions
Sevo - but no evidence of renal failure
91
T/F: VAs enhance the activity of succinylcholine but NOT non-depolarizing NMBs?
False They enhance both and cause dose related skeletal muscle relaxation
92
N2o effects on pulmonary vasculature
-increases pulmonary vascular resistance and should be avoided in patients with pulmonary HTN

Anesthesia Fast Facts (24 decks)

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