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Inhalational Anesthetics Flashcards

1
Q

What is the MOA of nitrous oxide?

A

NMDA receptor antagonist

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2
Q

What does NO do to myocardial contractility?

A

Depresses it

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3
Q

What does NO do to sympathetic nervous system?

A

Stimulates it so increases BP, CO, and HR because of the release of catecholamines.

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4
Q

What does NO do to the pulmonary vasculature?

A

Increases its resistance so causes increase in right ventricular end diastolic pressure

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5
Q

What does NO do to the respiratory system?

A

Increases the respiratory rate and decreases the tidal volume as a result of CNS stimulation.
It decreases hypoxia drive mediated by the carotid body chemoreceptors

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6
Q

What are the effects of NO in the CNS?

A

It increases CBF –> mild elevation in ICP

It increases CMRO2 (oxygen consumption in the brain)

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7
Q

What does NO do to muscle relaxation?

A

Actually causes skeletal muscle rigidity

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8
Q

What does NO do to renal system?

A

Decreases renal blood flow by increasing renal vascular resistance, decreasing GFR and UOP

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9
Q

What does the use of NO increase the risk of postoperatively?

A

PONV by activation of the CTZ

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10
Q

How is NO eliminated?

A

Thru exhalation

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11
Q

What enzyme does NO inhibit?

A

It irreversibly oxidizes the cobalt atom in vitamin B12 so it affects every vitamin b12 pathway.

  • myelin synthesis (methionine synthase), DNA synthesis (thymidylate synthase)

CAN CAUSE MEGALOBLASTIC ANEMIA AND PERIPHERAL NEUROPATHIES

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12
Q

Is NO teratogenic?

A

Yes

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13
Q

How does NO modulate the immune response?

A

It affects chemotasis and motility of PMNs

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14
Q

What are the contraindications to using NO

A

Pneumothorax, air embolism, SBO, pneumocephalus, tympanic membrane grafting (diffuses into air containing cavities due to solubility increasing the pressure within the cavity)
Pregnancy

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15
Q

What does NO do with other gases?

A

Decreases the MAC
Attenuated the circulatory and respiratory effects of volatile anesthetics
Potentials neuromuscular blockade

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16
Q

What are the effects on CV with isoflurane?

A

Increase in heart rate due to mild stimulation of beta receptors (no change in cardiac output)

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17
Q

What does isoflurane do to coronary arteries?

A

It dilates them

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18
Q

What are the respiratory effects of isoflurane?

A

Bronchodilates
Irritates the upper airway reflexes
Fall in minute ventilation

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19
Q

What does isoflurane do to the CNS?

A

Increases CBF and ICP at MAC greater than 1 (reversed by hyperventilation)

Reduces CMRO2

At MAC 2 it produces and electrically silent EEG

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20
Q

What does isoflurane do to muscles?

A

Relaxes them

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21
Q

What does isoflurane do to the renal system?

A

Decreases renal blood flow and therefore GFR and UOP

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22
Q

What is isoflurane metabolized to?

A

Trifluoroacetic acid

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23
Q

Can isoflurane trigger malignant hyperthermia?

A

Yes

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24
Q

What’s the difference between desflurane and isoflurane?

A

Desflurane has a fluorine atom instead of a chlorine atom

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25
Why does desflurane cause rapid induction and emergence?
It's low solubility
26
What is the blood/gas partition coefficient of desflurane?
0.42
27
What is the vapor pressure of desflurane?
High
28
What ar the cardiovascular effects of desflurane?
Cardiac output is maintained by mild beta stimulation With increased dose it causes a decline in SVR Increased CVP and pulmonary artery pressure
29
What do rapid increases in desflurane concentration lead to ?
Transient increases in heart rate, BP and catecholamines levels
30
What drugs attenuate the heart effect of desflurane with rapid increases in dosage?
Fentanyl Clonidine Esmolol
31
What does desflurane due to tidal volume?
Decreases it
32
What does desflurane do to respiratory rate?
Increases it
33
What do volatile anesthetics do to respiratory drive?
Decreases the ventilatory response to increasing PaCO2
34
Why is desflurane a poor choice as an induction agent?
It causes airway irritation | Can cause laryngospasm
35
What does desflurane do to the CNS.
``` Increases CBF Increases CBV Vasodilator cerebral vasculature Increases ICP Decreases CMRO2 ```
36
What does desflurane do to an EEG?
Increases the activity initially and then as anesthesia depends the EEG slows.
37
What is the neuromuscular effects of desflurane?
It is associated with dose-dependent decrease in the response to train of four and tetanus peripheral nerve stimulation
38
What is desflurane degraded by and into
Barium hydroxide lime, Sodium hydroxide, Potassium hydroxide Into carbon monoxide
39
How do you minimize the risk of carbon monoxide poisoning in degraded desflurane?
Dispose of dried out absorbent or use calcium hydroxide instead
40
What are the contraindications to using desflurane?
Severe hypovolemia Malignant hyperthermia Hypertension
41
What does desflurane do to nondepolarizing neuromuscular blocking agents?
Potentiates them
42
Can epinephrine be used with desflurane?
Yes, desflurane does not sensitize the myocardium to arrythmogenic effects of Epi
43
How are sevoflurane and desflurane similar in structure?
They are both halogenated with fluorine
44
What is the blood/gas coefficient of sevoflurane?
0.65
45
Why is sevoflurane a better choice for induction than des?
No pungent, so not irritating to the upper airways and also reaches high alveolar concentration quickly
46
What is desflurane associated with in the pediatric population?
Delirium
47
What is the vapor pressure of sevo?
Modest | Can use a conventional variable bypass vaporizer
48
What are the effects of sevo on the CV system?
Depresses myocardial contractility SVR and arterial blood pressure declines, but less than with iOS and des Decreases CO because it does not increase HR
49
What does sevo do to the EKG?
Prolongs QT
50
What does sevo do to the respiratory system?
Depresses respiration
51
What does sevo do to the bronchioles?
Dilates them - can reverse bronchospasm
52
What are the CNS effects of sevo?
Increase in CBF and ICP | Decrease in CMRO2
53
What happens to auto regulation at high levels of sevo?
It is impaired, so CBF will decrease during hemorrhagic hypotension
54
What does sevo do to the portal vein?
Decreases its flow
55
What does sevo do to the hepatic artery?
Increases its flow
56
Why should sevo be avoided in renal impairment?
It can be metabolized by the liver or degraded to fluoride or compound A which are nephrotoxic
57
How does compound A accumulate?
``` With increases in respiratory gas temperature Low flow anesthesia Dry barium hydroxide High sevo concentration Long anesthetic duration ```
58
What measures should you take to decrease the likelihood of renal injury by compound A?
Keep fresh gas flows at least 2L/min in long anesthetic cases
59
What does sevo do to NMBA?
Potentials them
60
What are the contraindications of sevo?
Severe hypovolemia Malignant hyperthermia high ICP
61
What is Xenon?
An inert gas that does not form chemical bonds
62
What is the MOA of Xenon?
It inhibits glycine binding at its receptor thereby inhibiting NMDA
63
What are the effects of Xenon on the organ systems?
Nothing
64
What does Xenon protect against?
Neuronal ischemia
65
What is the MAC of isoflurane?
1.2
66
What is the vapor pressure pf isoflurane?
240
67
What is the MAC of sevoflurane?
2.0
68
What is the vapor pressure of sevoflurane?
160
69
What is the MAC of Des?
6
70
How does renal failure occur from fluoride ions?
Direct fluoride ion toxicity to the collecting ducts which inhibits ADH effect so it is a high-output vasopressin resistant renal failure
71
Why doesn't sevoflurane cause fluoride associated renal failure?
The accumulation of fluoride ions decreases as soon as the gas is stopped due low blood and tissue solubility
72
What do volatile anesthetics do to the heart?
Depress the SA node and cause junction all rhythm Mild dose dependent decrease in myocardial contractility due to inhibition of L-type and T-type calcium channels and inhibition of sodium-calcium exchangers resulting in overall decrease of intracellularly calcium
73
How does nitrous increase cardiac output?
By stimulation of the sympathetic nervous system
74
How does isoflurane cause direct coronary vasodilation?
Activation of ATP-sensitive potassium channels Inhibition of calcium influx through calcium channels --> Reduction in calcium accumulation Reduced calcium release by sarcoplasmic reticulum
75
How much anesthetic vapor is in 1 ml of liquid volatile?
200 ml at room temperature
76
What does nitric oxide do?
Decreases pulmonary vascular resistance and off loads the RH. Inhibits platelet aggregation Increases cGMP so causes smooth muscle relaxation
77
Which vessels does nitric oxide primarily dilate?
Arterioles
78
What is the MOA of sevo, iso, Des?
They potentiate GABA receptors and glycine Produce immobility by effects in the spine Amnesia by effects on hippocampus, amygdala, cerebral cortex Block nociceptive info going up the afferents to cerebral cortex
79
Which inhalational anesthetic potentiates NMBs the most?
Desflurane (by 60% in healthy patients)
80
How do inhalational anesthetics potentiate NMB effect?
Directly: By relaxing skeletal muscle, especially when > 1 MAC Indirectly: unknown mech, maybe central alpha adrenergics
81
Which inhalational anesthetic does NOT provide skeletal relaxation?
NO
82
Which class of NMBDs do inhalational anesthetics work more synergistically with?
The amino steroids: roc, vec, pan
83
How much do isoflurane and sevoflurane augment NMBs?
40%
84
Why does nitrous oxide have a faster rate of rise than desflurane?
Concentration effect
85
What happens to the rate of inhalational induction in a right to left cardiac shunt?
It slows because there is less pulmonary blood flow and the anesthetic rich blood is mixing with the anesthetic poor blood
86
What happens to the rate of inhalational induction with a left to right cardiac shunt?
Stays the same

Anesthesia MM/TL (36 decks)

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