Volatile Anesthetics Flashcards

1
Q

Advantages of Ether:

A

Moved through anesthesia stages reliably

Maintained cardiac output and blood pressure

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2
Q

Disadvantages of Ether:

A

Extremely flammable and explosive, strong emetic properties, airway irritant

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3
Q

What is halogenation? What is the advantage?

A

A chemical reaction that incorporates a halogen atom (fluoride, bromide, chloride, iodine) into a molecule.
Advantage: increases stability, non-flammable

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4
Q

Halothane: Stored in_____, preserved with _____.

A

amber bottles, thymol-makes it sticky.

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5
Q

Advantages of Halothane:

A

Coronary artery vasodilator, non-pungent, non-irritating to respiratory mucosa (Good for inhalation induction), bronchodilator, low PONV, preferred for Tetralogy of Fallot

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6
Q

Disadvantages of Halothane:

A

Strongest myocardial depressant of all gases, induced arrhythmias, hepatic effects (decreased blood flow causes cell dysfunction), halothane hepatitis

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7
Q
Type 1 vs Type 2 Halothane Hepatitis:
Cause:
Onset:
Labs:
Symptoms:
A

Type 1: mild, from metabolization, genetic factors, reduced liver oxygenation. Onset: with hours Labs: mild elevations in liver enzymes S/S: jaundice
Type 2: severe, , from antibody immune response, binds to hepatocytes, massive necrosis. Onset: high fever 3-14 days after, Labs: elevated bilirubin, elevated liver labs, S/S: high fever, rash, eosinophilia, jaundice, nausea and vomiting, encephalopathy.
50-80% mortality rate with encephalopathy

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8
Q

Advantages of Methoxyflurane:

A

mild hemodynamic effects, profound muscle relaxant, does not sensitize myocardium to catecholamines, powerful analgesic

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9
Q

Disadvantages of Methoxyflurane:

A

VERY metabolized (up to 50%), produces free fluoride ions, can cause renal failure, hepatoxicity, pungent

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10
Q

Methoxyflurane
MAC:
B:G:
What does that mean?

A

0.16% SUPER potent. Have to be very careful.

10-14, high blood solubility, slow onset. Can leech into system/hoses.

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11
Q

What is Penthrox?

A

Used historically during labor for analgesia. Used in Australia for emergencies, “green whistle”, penthrane inhaler

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12
Q

Advantages of Enflurane:

A

non-flammable, colorless, non-irritating, stable, can be used in any vaporizer, no impurities, low PONV, rapid induction (compared to ether and methoxyflurane), hemodynamic stability, bronchodilator

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13
Q

Disadvantages of Enflurane:

A

Produces free fluoride ions (damages kidneys), Ethrane shakes, increases CSF and resistance to CSF flow, can cause EEG to look like tonic clonic seizures

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14
Q

Cyclopropane is stored in _____

A

Orange cylinders as a pressurized liquid

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15
Q

Cyclopropane:
MAC:
B:G:

A
  1. 2%

0. 55 (fast induction)

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16
Q

Advantages of cyclopropane:

A

non-irritating, blood pressure stability, increased cardiac ouput, no hepatic effects, B:G 0.55 (fast induction), rapid recovery, no delirium

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17
Q

Disadvantages of cyclopropane:

A

powerful respiratory depressant, bronchoconstrictor, pro-arrhythmic, pro-emetic, EXPLOSIVE

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18
Q

Xenon limitation to use:

A

Cannot be manufactured-must be extracted from air. Makes it very expensive and limited quantities

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19
Q

Xenon:
MAC:
B:G

A

71%

.11 (VERY QUICK)

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20
Q

Xenon advantages:

A

minimal side effects: little to no cardiac depression, maintains cerebral autoregulation, extremely insoluble, no diffuse hypoxia (like N20 can have), NOT a trigger for malignant hyperthermia
Administered with 30% oxygen for surgical anesthesia

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21
Q

Disadvantages of Xenon:

A

Cost, limited availability, increases cerebral blood flow by 30% (not good for neuro), slight increase in PONV, increases pulmonary resistance

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22
Q

What is MAC?

A

Minimum Alveolar Concentration. A measure of potency. The concentration at which 50% of the population will not move in response to surgical stimuli. Inversely related to potency and lipid solubility. As MAC goes up, potency goes down and lipid solubility goes down.

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23
Q

What is the MAC of isoflurane?

A

1.2

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24
Q

What is the MAC of sevoflurane?

A

1.9

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25
Q

What is the MAC of desflurane?

A

6

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26
Q

What are things that increase MAC?

A

increased catecholamines, chronic ETOH use, young age

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27
Q

What are things that decrease MAC?

A

age, hypothermia, CNS depressants, hypotension, hypoxia, pregnancy, hypercarbia, acute ETOH use.

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28
Q

What is MAC awake?

A

50% of people will response. Usually about 1/3 of MAC

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29
Q

What is MAC BAR?

A

Block Adrenergic Response. Blocks response to incision, 1.1-1.5 MAC

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30
Q

What is the Meyer-Overton Hypothesis and what is the flaw?

A

The potency of anesthetics relates to their lipid solubility. Flaw: not all anesthetics are lipid soluble.

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31
Q

What is Mullin’s Critical Volume hypothesis? What is the flaw?

A

CNS cell membranes expand with general anesthetic agents, this distorts channels responsible for membrane potentials. Flaw: does not account for stereo-selectivity

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32
Q

What are the 4 determinants of uptake:

A
  1. inspired concentration (MAC)
  2. partial pressure (alveolar gradient)
  3. solubility (B:G)
  4. blood flow (cardiac output)
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33
Q

What is uptake?

A

Rate of accumulation of a drug in various tissues

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34
Q

What is Henry’s Law?

A

amount of gas that will go into a solution is proportional to the partial pressure of that gas.

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35
Q

How do temperatures affect partial pressure?

A

Lower temperatures cause more gas to dissolve, causing slower induction.

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36
Q

What is a blood gas coefficient?

A

describes the blood solubility of a gas. The more soluble the gas is in blood compared to air, the more it binds to plasma proteins and the higher the coefficient.

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37
Q

What is the B:G of Desflurane?

A

0.42

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38
Q

What is the B:G of N20?

A

0.46

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39
Q

What is the B:G of Sevoflurane?

A

0.65

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40
Q

What is the B:G of Isoflurane?

A

1.42

41
Q

What is the B:G of Enflurane?

A

1.9

42
Q

What is the B:G of Halothane?

A

2.5

43
Q

How does cardiac output affect induction?

A

increased CO pulls more gas out of alveoli, reduces alveolar partial pressure and slows induction time.

44
Q

What is the MAC of nitrous oxide?

A

104

45
Q

What is the MAC of halothane?

A

.7

46
Q

What is an Oil:Gas coefficient?

A

Measures the affinity for tissues to uptake an inhaled anesthetic. Measure of potency. Directly related to potency. Inversely related to MAC

47
Q

Who used Nitrous for painless dentistry?

A

Horace Wells

48
Q

Who coined the term “laughing gas”

A

Humphrey Davy

49
Q

Who is recognized as the founder of nitrous for analgesia/anesthetic?

A

Horace Wells

50
Q

_____ is heated to 250 degrees to form nitrous oxide

A

Ammonium nitrate

51
Q

Which gas is not a trigger for malignant hyperthermia?

A

Nitrous oxide

52
Q

What is the molecular weight of Nitrous?

A

44g/mole

53
Q

What is the MAC of nitrous?

A

104

54
Q

Nitrous is stored in ____ cylinders.

A

Blue

55
Q

How do you know how full a nitrous cylinder is?

A

The WEIGHT, not the pressure.

56
Q

What is the B:G of nitrous?

A

0.47

57
Q

What is the O:G of nitrous?

A

1.4

58
Q

Which receptors does nitrous act on? Agonist or antagonist?

A

NMDA receptors, antagonist

59
Q

Must use a minimum of ____ FiO2 to avoid hypoxia with nitrous.

A

0.25%

60
Q

Explain Ficks Law of Diffusion or the concentration effect.

A

The amount of N20 diffusing from the alveoli into the blood from nitrous is MUCH HIGHER than the amount of N2 that normally diffuses across from air. This causes the alveoli to shrink, thus further concentrating the amount of N2O in the alveoli. The diffusion gradient remains high, and nitrous quickly diffuses into the blood.

61
Q

Almost all of N2O is excreted through the ____

A

lungs

62
Q

Explain diffusion hypoxia.

A

When the nitrous is turned off, the N20 diffuses from the blood to the alveoli so rapidly, the alveolar size increases, thus diluting out the PaO2 and PaCO2.

63
Q

How can you avoid diffusion hypoxia?

A

Administer 100% oxygen for 3-5 minutes after turning off the nitrous.

64
Q

What are some contraindications for nitrous use?

A

PONV, pulmonary HTN, gas bubble in eye for retinal detachments, pnemothorax, bowel obstruction

65
Q

How does nitrous affect the kidneys?

A

Decreased renal blood flow, decreased urine output

66
Q

How does nitrous affect neuro?

A

Increased cerebral metabolic demand, increased cerebral blood flow, increased ICP

67
Q

What does nitrous inactivate in the blood, which interacts with vitamin B12? What does it cause?

A

Methionine synthetase, thymidylate synthetase. Causes pernicious anemia, bone marrow suppression, peripheral neuropathy

68
Q

What is the risk of giving nitrous to somebody with a vitB12 deficiency?

A

Blocks enzyme methionine synthetase (which is required for folate metabolism and myelin production). results in polyneuropathy.

69
Q

Who is at risk to have a vit B12 deficiency?

A

anemia, ETOH use, strict vegan diet, recreational use of N2O, gastric bypass, gastritis with PPI use

70
Q

How would you identify the chemical structure of isoflurane?

A

It has a Chloride ion.

71
Q

What is the chemical name of isoflurane?

A

Methylethyl Ether

72
Q

What are the cardiac implications of isoflurane?

A

**Coronary steal. Increased HR, decreased BP and SVR

73
Q

What are the respiratory implications of isoflurane?

A

Mildly pungent, not great for induction, bronchospasm

74
Q

What are the renal implications for isoflurane?

A

Decreased renal blood flow (more than sevo or des)

75
Q

What are the neuro implications of isoflurane?

A

Increased ICP, lowers seizure threshold

76
Q

What are 3 severe medication interactions with isoflurane?

A

droperidol (long QT), norepi/epi (irritability), MAOI’s (labile BP)

77
Q
Isoflurane:
MAC
BG
OG
VP
MW
Met
A
MAC: 1.2
BG: 1.46
OG: 91
VP: 238
MW: 184.5
Met: 0.2%
78
Q
Desflurane:
MAC
BG
OG
VP
MW
Met
A
MAC: 6.6
BG: 0.42
OG: 19
VP: 667
MW: 168
Met: 0.02%
79
Q

How do you identify the chemical structure of desflurane?

A

All Fluoride ions

80
Q

What is the chemical name of Desflurane?

A

Methylethyl ether

81
Q

What are the cardiac implications of Desflurane?

A

**increased HR, a predictable decreased in SVR with dose, Increased PA, no sensitivity to epi

82
Q

What are the respiratory implications of Desflurane?

A

very irritating to the airway, laryngospasm, coughing

83
Q

What are the neuro implications of Desflurane?

A

**Marked decreased in cerebral metabolic demand, increase in ICP, and CBF.

84
Q

What are the musculoskeletal implications of Desflurane?

A

decreased muscle tone. Synergistic effect with muscle relaxants (ED 95 of succinycholine decreased by 30%)

85
Q

What are some advantages of Desflurane?

A

quick on/off, muscle relaxant, minimal metabolism

86
Q

What are some disadvantages of Desflurane?

A

Low potency, respiratory irritant, tachycardia, decreased SVR, potent greenhouse gas

87
Q
Sevoflurane:
MAC
BG
OG
VP
MW
Met
A
MAC: 2
BG: .63
OG: 53
VP: 157
MW: 200
Met: 2-5%
88
Q

How do you identify the chemical structure of Sevoflurane?

A

7 fluoride atoms (sevo-7)

89
Q

What is the chemical name of Sevoflurane?

A

Methylisopropyl ether

90
Q

What are the cardiac implications of Sevoflurane?

A

Less effect on cardiac than Iso and Des. Mild decrease in contractility

91
Q

What are the respiratory implications of Sevoflurane?

A

Best gas on the respiratory system. Good for induction.

92
Q

What are the hepatic implications of Sevoflurane?

A

maintains flow, low chance of toxicity

93
Q

What are the renal implications of Sevoflurane?

A

Slight increase in renal flow, does produce some inorganic fluoride ions

94
Q

What are the neuro implications of Sevoflurane?

A

linked to seizures with high MAC. Slight increase in CBF and ICP. Not used much for neuro procedures.

95
Q

What are the musculoskeletal implications of Sevoflurane?

A

profound muscle relaxant. Can intubate without a neuromuscular blocking drug.

96
Q

Which volatile gas is used the most for peds?

A

Sevo

97
Q

Which volatile gas is not used in cath lab/conduction procedures?

A

Des

98
Q

What is the name of the byproduct from Sevo? How do you avoid complications from it?

A

Compound A-byproduct of the CO2 absorber. Nephrotoxic.

Don’t have too low of flows, keep it greater than 1L