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Anesthesia Pharm (Spring '24) - C > Lecture 12 (Exam 3 Inhaled Anesthetics Part 2) > Flashcards

Lecture 12 (Exam 3 Inhaled Anesthetics Part 2) Flashcards

1
Q

What are the four functions of the anesthesia circuit?

A
  1. Delivers O2
  2. Delivers inhaled drugs
  3. Maintain temperature/ humidity
  4. Removes CO2 and exhale drugs
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2
Q

What three types of circuits?

A
  1. Rebreathing (Bain)
  2. Non-rebreathing (Self-inflating Bag Valve Mask - Ambu Bag)
  3. Circle System
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3
Q

What kind of circuit is used when transporting an intubated patient to ICU?

A

Bain Circuits

They are very portal and minimalistic

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4
Q

What circuit is used in anesthesia machines?

A

Circle System

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5
Q

When fresh gas enters the circle system from the fresh gas inlet and goes towards the inspiratory limb. Why can’t gas flow backward?

A

There is an inspiratory unidirectional valve that prevents the backward flow of gas.

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6
Q

From the inspiratory limb, where will gas flow next?

A

Gas will flow into the Y-piece and end up in the ETT or LMA.

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7
Q

Expired gas will go back through the ________ and travel toward the expiratory limb and through the expiratory unidirectional valve.

A

Y-piece

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8
Q

Where will gas go after leaving the expiratory unidirectional valve?

A

Gas will either go toward the ventilator or into the reservoir bag.

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9
Q

What is high-flow inhalation anesthesia?

What are some downsides to high-flow anesthesia?

A

Fresh gas flow (FGF) exceeds minute ventilation.
High flow allows providers to make rapid changes in anesthetics (induction) and prevents rebreathing.

Wasteful and cool/dries delivered volume.

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10
Q

What is low-flow inhalation anesthesia?

What are some downsides to low-flow anesthesia?

A

Fresh gas flow (FGF) less than minute ventilation. Low cost, conserves gas, less/cooling, and drying.

A very slow change in anesthesia

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11
Q

Factors that contribute to the price/cost of anesthesia.

A

Cost of liquid/ml
Vol % of anesthetic delivered - Potency
Fresh gas flow rate

Desflurane is expensive, often refilled d/t MAC at 6.6%

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12
Q

How do volatile anesthetics cause bronchodilation?

A

Relax airway smooth muscle by blocking VG Ca2+ channels. Depletion of Ca2+ in SR.

For bronchodilation to occur, there needs to be an intact epithelium. Inflammatory processes and epithelial damage will result in no bronchodilation (asthma).

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13
Q

A patient without a history of bronchospasm will not see baseline pulmonary resistance change with ____ to ___ MAC of volatile anesthetics.

A

1 to 2 MAC

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14
Q

For a patient with a history of bronchospasm which volatile gas will be most beneficial for bronchodilation?

Which gas will worsen bronchospasm for smokers?

A

Sevoflurane (best bronchodilator)

Desflurane

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15
Q

What are the 3 best anesthetic gases to use if you do not want to encounter respiratory resistance?

A
  1. Sevoflurane (best choice)
  2. Halothane
  3. Isoflurane
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16
Q

What are the neuromuscular effects of volatile anesthetics?

A

Dose-dependent skeletal muscle relaxation, not paralysis. Although, they do potentiate the depolarizing and non-depolarizing NMBD (nAch receptors at NMJ and enhance glycine in the spinal cord).

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17
Q

What gas has no effect on skeletal muscles?

A

Nitrous Oxide

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18
Q

What is ischemic preconditioning?

A

If the heart recognizes brief periods of ischemia before being subjected to longer periods of ischemia, the heart is able to prepare itself for the longer period of ischemia.

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19
Q

Ischemic precondition is mediated by _______.
Increase protein kinase C activity phosphorylates _____________ channels. This will lead to the production of reactive oxygen species and lead to better regulation of vasculature tone.

A

Adenosine
ATP-sensitive K+ channel

ATP-sensitive K+ channels in the heart will slow down HR. ROS production will cause vasoconstriction.

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20
Q

Ischemic preconditioning can occur with __________ MAC.

A

0.25

Barely turning on the vaporizer.

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21
Q

What are the benefits of ischemic preconditioning?

Clinically, when can ischemic preconditioning be useful?

A

Prevents “reperfusion injury”
Do not see as many cardiac dysrhythmias.
Less contractile dysfunction.

Clinically apparent in delaying MI for PTCA or CABG.

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22
Q

How will volatile anesthetics affect CNS activity?

A

Dose-dependent decrease in CMRO2 and cerebral activity.

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23
Q

At ______ MAC, wakefulness changes to unconsciousness.

What MAC will there be burst suppression?

What MAC will there be electrical silence?

A

0.4

1.5

2.0

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24
Q

Rank the 3 volatiles in relation to decreasing CMRO2 and cerebral activity.

A

Isoflurane, sevoflurane, and desflurane all have equal effects on CNS activity.

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25
Q

Which volatiles have anticonvulsant activity?

Which volatiles have pro-convulsant activity?

A

Des, Iso, and Sevo

Enflurane (pro-convulsant) - especially above 2 MAC or PaCO2< 30 mmHg

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26
Q

How will volatile anesthetics affect somatosensory evoked potentials (SSEP) or motor evoked potentials (MEP)?

How is this a problem?

A

A dose-related decrease in amplitude and increase in latency (drawn out) with a 0.5 to 1.5 MAC.

Harder to discern whether or not there is damage to the spinal cord.

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27
Q

What is SSEP?

A

There will be a stimulation to a periphery (foot), and response will be measured in the brain to ensure adequate neurotransmission up the spinal cord.

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28
Q

What is MEP?

A

There will be a stimulation of the brain and response will be measured in the periphery (foot/arm) to ensure adequate transmission down the spinal cord.

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29
Q

How do you prevent the negative effects on SSEP and MEP monitoring when using volatiles?

A

Do not use more than 0.5 MAC if you are monitoring SSEP or MEP for spinal cases.

Instead, use 0.5 MAC of volatile with 60% of N2O or IV anesthetic (propofol, precedex).

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30
Q

How do volatile anesthetics affect CBF?

A

Increase CBF d/t decrease cerebral vascular resistance. This can result in an increase in ICP.

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31
Q

At what MAC will there be an onset of CBF increase?

A

Above 0.6 MAC
Can occur within minutes despite the lack of BP change.

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32
Q

What is the best volatile anesthetic to use for a patient with a known increase ICP?

Which volatile will have the greatest vasodilatory effect?

A

Sevoflurane has the least vasodilatory effect. (not shown in graph)

Halothane will have the greatest vasodilatory effect resulting in the greatest increase in CBF.

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33
Q

Autoregulation maintains cerebral blood flow relatively constant between ____ and ______ mm Hg mean arterial pressure

A

60 to 160 mmHg

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34
Q

How do volatile anesthetics affect the autoregulation of cerebral blood flow?

A

Dose-dependent loss of autoregulation.

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35
Q

Autoregulation will be lost by what MAC with Halothane.
What MAC for Sevoflurane?
What MAC for Isoflurane?
What MAC for Desflurane?

A

Halothane: 0.5 MAC
Sevo: 1 MAC (Best at preserving autoregulation)
Iso: 0.5-1.5 MAC
Des: 0.5 -1.5 MAC

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36
Q

What is the volatile of choice for neuro anesthetics?

A

Sevoflurane can preserve autoregulation up to 1 MAC.

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37
Q

Which patients are at the most risk of increased ICP from volatiles?

A

Patients with space-occupying lesions and tumors are at the most risk.

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38
Q

How does hyperventilation decrease ICP?

A

Inducing hypocapnia via hyperventilation reduces PaCO2, which will cause vasoconstriction in the cerebral arterioles decreasing ICP.

Short-term fix for increasing ICP (15 mins)

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39
Q

At what MAC will there be an increase ICP?

How much will ICP increase?

A

0.8 MAC

Increase by 7 mmHg.

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40
Q

How do volatile anesthetics affect respiration?

A

A dose-dependent increase in rate and decrease in tidal volume.

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41
Q

How do volatile anesthetics cause respiratory depression?

A

Direct depression of medullary ventilatory center.
Interference with intercostal muscles.

Rate change insufficient to maintain minute ventilation, there will still be alteration in PaCO2 that indicates respiratory depression.

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42
Q

At what MAC will there be apnea?

A

1.5 to 2.0 MAC

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43
Q

Hypoxic responses are mediated by the _________.

How do volatile anesthetics affect hypoxic responses?

A

Carotid bodies

Blunt hypoxic response

44
Q

There will be a 50-70% depression in hypoxic response with ______ MAC.

100% depression at ______ MAC

A

0.1 MAC

1.1 MAC

45
Q

Which gasses will blunt the hypoxic response?

A

All volatiles including nitrous.

46
Q

What are the effects of volatiles on hypercarbic response?

A

Dose-dependent blunting of hypercarbic response.

47
Q

Which gasses will not blunt the hypercarbic response?

A

Nitrous does not increase PaCO2.
A great substitution for part of MAC.

48
Q

Intrapulmonary arteries constrict in response to alveolar hypoxia, diverting blood to better-oxygenated lung segments to optimize V/Q matching. What is this process called?

A

Hypoxic Pulmonary Vasoconstriction

49
Q

When the alveoli have not been ventilating for ________ minutes. HPV will kick in and reduce the blood flow to the poorly ventilated area by ________%.

A

When the alveoli have not been ventilating for 5 minutes. HPV will kick in and reduce the blood flow to the poorly ventilated area by 50%.

50
Q

How do volatile anesthetics affect HPV?

A

A dose-dependent decrease in HPV response.

51
Q

There will be a 50% depression in HPV at ______ MAC.

A

2 MAC

52
Q

How do volatile anesthetics cause myocardial depression?

A

Inhibits calcium entry, and alters SR function. There will be a decrease in contractility, SV, and CO (Halothane Hearts). The decrease in MAP is primarily d/t decrease in SVR.

53
Q

What gas will not cause cardiac depression?

A

Nitrous

54
Q

How do volatile anesthetics affect heart rate?

A

A dose-dependent increase in HR.

55
Q

Sevoflurane will see a HR increase at a MAC greater than ________.

A

1.5 MAC

Iso and Des will require a lower MAC for HR increase

56
Q

What happens to HR with desflurane overpressurization?

A

A significant increase in HR (60 bpm to 140 bpm).

57
Q

Even though volatile anesthetics tend to increase heart rate we don’t usually see it in the OR. Why is that?

A

The patient is usually on other medications that will help offset the tachycardia.

Examples:
Pre-op meds: BZD
Opioids
Beta-blockade
Vagolytic administration

58
Q

What is the effect of the volatile anesthetic on cardiac output?

A

A dose-dependent decrease in CO (offset by a mild increase in HR for most volatiles).

59
Q

What is the effect of nitrous on CO?

A

Mild increase in CO.

60
Q

Which volatile anesthetic will have the largest decrease in the cardiac index?

A

Halothane

61
Q

Which gas has a proarrhythmic effect?

A

Nitrous

62
Q

Which volatile anesthetic will be used in an ablation case?

A

Sevoflurane will not increase the refractoriness of accessory pathways. This will be the best gas to use if you want to evaluate if the ablation was successful.

In actual settings, general anesthetics will not be used in ablation cases. Sedation cases.

63
Q

Immune effect of volatile anesthetics.
What will be activated?
What will be suppressed?

A

Activation of the autonomic nervous system.
Activation of the Hypothalamic-Pituitary-Adrenal Axis.
There will be an increase in catecholamines, ACTH, and cortisol.

Suppression of monocytes, macrophages, and T-cells

64
Q

Some studies suggest GA compared to neuraxial have increase _____- and increase ________.

A

metastasis
mortality

65
Q

How do volatile anesthetics affect hepatic blood flow?

A

Total hepatic blood flow and hepatic artery flow are maintained.

Volatiles dilate the portal vein which will increase blood flow.

66
Q

At what MAC will the portal vein flow increase?

A

1 to 1.5 MAC.

(Iso, Des, Sevo)

67
Q

Which gas will decrease hepatic flow and decrease oxygen delivery?

A

Halothane
Halothane Hepatitis

68
Q

Hepatotoxicity occurs when there is inadequate _______ of hepatocytes.

A

oxygenation

Decrease blood flow, will lead to enzyme induction, increasing O2 demand.

69
Q

Type I Hepatotoxicity related to volatile gas:
Occurs in _____% of patients.
________ (length) after exposure.
Direct effects or free radicals.
Symptoms:

A

Type I Hepatotoxicity related to volatile gas:
Occurs in 20% of patients.
1-2 weeks after exposure.
Direct effects or free radicals.
Symptoms: Nausea, lethargy, fever

70
Q

Type II Hepatotoxicity related to volatile gas:
Less common
_________(length) after exposure.
High mortality rate d/t ________ and ________
Immune-mediated response against hepatocytes will present with ______ and _______.

A

Type II Hepatotoxicity related to volatile gas:
Less common
1 month after exposure.
High mortality rate d/t acute hepatitis and hepatic necrosis
Immune-mediated response against hepatocytes will present with fever and eosinophilia.

71
Q

Volatile anesthetics are metabolized through P450 to ___________ metabolites.

What gas is the exception?

A

Acetyl Halide

Sevoflurane
Metabolized to Vinyl Halide, metabolite does not cause antibody formation.

72
Q

When volatile anesthetics are oxidized by P450 to acetyl halide metabolite. The metabolites are capable of causing ___________.

A

antibody reaction

Most likely in patients sensitized by halothane and enflurane

73
Q

What is the best volatile anesthetic to give for someone with severe liver disease?

A

Sevoflurane

74
Q

What are the renal effects of volatile anesthetics?

A

A dose-dependent decrease in RBF, GFR, and U/O. This is not related to r/t vasopressin but CO.

Make sure patients are preoperatively hydrated
Like the heart, the kidneys can also be preconditioned

75
Q

Nephrotoxicity is caused by _________.

A

Fluoride metabolites.

Volatile anesthetics have fluoride in them

76
Q

Fluoride metabolites causes ______, _______, and ______.

A

Hyperosmolarity
Hypernatremia
Increase Creatinine

77
Q

Which volatile anesthetic causes the worst nephrotoxicity?

A

Methoxyflurane

70% metabolized, removed from the market

78
Q

No clinical data to demonstrate ____________ is a risk at low fresh gas flow to humans.

A

Compound A

79
Q

How can you tell if your CO2 absorbent has been desiccated (dried) or used up?

A

There will be a rise in ET CO2.

80
Q

How can Sevoflurane spontaneously combust?

A

Sevo can react with the desiccated absorbent and Baralyme (composition of absorbent) to produce methanol and formaldehyde. If heat is added to this product, Sevo can combust.

Water is added to sevoflurane to inhibit the production of methanol and formaldehyde. Check the temperature of the absorbent canister.

81
Q

How is MH diagnosed?

A

Caffeine contracture test

82
Q

What are the triggers of MH?

A

All volatile anesthetics and succinylcholine

83
Q

MH produces a hypermetabolic state of skeletal muscles that can lead to _____, _____, and ______.

A

Excessive release of calcium
Muscle ridgidity
Rhabdomyolysis

84
Q

Sx of MH

A

Increase body temp
Increase CO2 production
Increase O2 consumption

85
Q

MH has a ____% mortality if untreated.

A

80

86
Q

Tx for MH

A

Dantrolene
-Blocks intracellular Ca2+ release

Supportive care for rhabdo

87
Q

All volatile anesthetics can cause PONV.

If GA is given with two triggering agents (volatile and opioids) ___________% of patients will experience PONV.

Nitrous will cause >_____% of patients to experience PONV.

A

25-30%

50%
(Stay below 0.5 MAC)

88
Q

Metabolic Effects:
What deficiency can be caused by N2O?

A

B12 deficiency
Developing fetus at risk

Make sure to use a scavenging system with pregnant mothers (first trimester) and avoid giving N2O

89
Q

Metabolic Effects:
What does N2O suppress?

A

Megaloblastic bone marrow suppression will result from being exposed to N2O for more than 24 hours or cumulative exposure.

90
Q

Metabolic Effects:
N2O can increase ________ levels.

A

plasma homocysteine

Associated with low levels of B vitamins
Associated with increased levels of atherosclerosis
Can increase myocardial events

91
Q

What are the effects of volatile anesthetics on obstetrics?

A

A dose-dependent decrease in uterine smooth muscle contractility.

This can be useful for a retained placenta stuck in the patient.

Volatile anesthetics can worsen blood loss in uterine atony.

92
Q

Which gas has no effect on uterine contractility but can increase analgesia without opioids/BZD.

A

Nitrous

93
Q

Halothane is a halogenated ________.
Halthothane is compatible with ____________.
Smells _______and ________.
________ potency and _______ solubility.

A

Alkane
Inhalation Induction
Sweet and non-pungent
High potency and intermediate solubility

94
Q

Pros of Halothane:

Cons of Halothane:

A

Pros: Low N/V, non-flammable

Cons: Catecholamine-induced arrhythmias, hepatic necrosis, pediatric brady-arrhythmias, decomposes to HCl acid (thymol preservative added).

95
Q

Isoflurane is an isomer of _______.
Isoflurane is highly _______ and highly _____.
Isoflurane is not good for __________.

A

Enflurane
Highly pungent and highly potent
Inhalation induction

96
Q

Pros of Isoflurane:

Cons of Isoflurane:

A

Pros: Resistant to metabolism, unlikely to cause organ toxicity, Isoflurane is stable (no deterioration after 5 years).

Cons: Distillation is complex and expensive to purify

97
Q

Desflurane (Suprane) is a fluorinated _______.
Identical to __________ except that F is substituted for Cl-.
Desflurane has decrease _______ and ________
Desflurane has high ________.

A

methyl ethyl ether.
Identical to isoflurane
decrease solubility and decrease potency
high vapor pressure

98
Q

Which volatile anesthetic is the most pungent?

A

Desflurane (Suprane)

It will cause coughing, salivation, breath-holding, and laryngospasm.

99
Q

Over-pressurizing desflurane will cause ________ stimulation.

A

SNS

100
Q

Desflurane will degrade to _______ if the absorbent is dehydrated.

A

carbon monoxide

Desflurane degrades to carbon moxide the most > Enflurane > Isoflurane > Sevoflurane

101
Q

Sevoflurane (Ultane) is a fluorinated _________.
_______ Solubility
Smells _______
Least ________ of modern volatiles

A

Methyl Isopropyl Ether
Low Solubility
Smells sweet and non-pungent
Least airway irritation

102
Q

Sevoflurane is metabolized to __________
Sevoflurane is least likely to form ________

A

inorganic fluoride
carbon monoxide

103
Q

________ is not usually used as a sole anesthetic.

A

Nitrous Oxide
(Unable to deliver 1 MAC, need 104% which is impossible)

104
Q

N2O has ________ solubility and _______potency.
N2O does not produce __________ relaxation.
N2O smells ________.

A

Low solubility, low potency
no skeletal relaxation
Sweet-smelling, odorless

105
Q

Pros of N2O.

Cons of N2O.

A

Pros:
Good analgesia
2nd gas effect

Cons:
N/V >50% of patients
Increase Pulmonary Vascular Resistance
Neonates may increase right to left shunt
Jeopardize arterial oxygenation
Contraindicated in Bowel, Globes, Ear, Lung procedures

106
Q

What cardiac dysrhythmias can be presented with volatile anesthetics?

A

Prolonged QT interval in healthy patients d/t inhibition of potassium currents.

Potentially increase risk of Torsades.

Anesthesia Pharm (Spring '24) - C (20 decks)

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