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volatiles Flashcards

1
Q

What 3 factors will affect the uptake of volatile anesthetics from the alveoli to the blood?

from old pharm class

A
  1. Blood: gas partition coefficient
  2. Cardiac output
  3. Alveolar-to-Venous partial pressure differences
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2
Q

What 3 factors will affect the uptake of volatile anesthetics from the arterial blood to the brain?

from old pharm class

A
  1. Brain:blood partition coefficient
  2. Cerebral blood flow (dependent on CO)
  3. Arterial-to-Venous partial pressure difference
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3
Q

How does the use of N2O during anesthetic induction hasten onset of a second gas (volatile)?

A

rapid uptake of N2O will cause alveolus to shrink. the reduction in alv volume and augmented tracheal inflow on next breath causes a relative increase in concentration of second gas. This increases alveolar ventilation and augments FA.

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4
Q

Hyperventilation will cause a decrease in ____ which will decrease cerebral blood flow (vasoconstriction) and limit the speed of induction.

A

PaCO2

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5
Q

Differentiate between spontaneous ventilation and mechanical ventilation.

A

Spontaneous ventilation has a dose-dependent depressant effect on alveolar ventilation (negative feedback loop). As input decreases d/t decreased ventilation the volatile redistributes from tissue w/ high concentration (brain) to tissues w/ low concentration (fat). As brain concentration decreases, ventilation increases.

When mechanical ventilation, the body is not able to provide a negative feedback loop. The ventilator will continue to administer molecules at a set rate.

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6
Q

Solubility is temperature dependent. If the temperature of the blood increases, solubility ____.

A

Decreases
so the volatile will not want to stay in the blood, it will want to go into the brain = Faster induction

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7
Q

If blood solubility is high, a large amount of volatile anesthetics must be dissolved. How will this affect induction?

A

The anesthetic agent wants to stay in the blood and induction is prolonged.

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8
Q

What is the Blood:Gas Partition Coefficient of Halothane?

A

2.54

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9
Q

What is the Blood:Gas Partition Coefficient of Desflurane?

A

0.42

This means that desflurane is not very soluble and does not want to stay in the blood. Fast induction, fast emergence.

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10
Q

Which one has the lowest solubility?

A. Desflurane
B. Sevoflurane
C. Isoflurane

A

Desflurane will have the lowest solubility followed by Sevo and then Iso.

This means that people will go to sleep and wake up faster from desflurane.

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11
Q

Halothane has a Blood: Gas Partition Coefficient of 2.54. What does that mean?

A

When the relative ratio is the same (when solubility equals out). There is 2.54 times more Halothane in the blood than in the gas compartment. This means that halothane is VERY soluble, it likes to stay in the blood. The blood will hold a lot of halothane. Slow induction and slow emergence.

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12
Q

What is the Blood: Gas Partition Coefficient of Isoflurane?

A

1.46

most soluble in blood = SLOWEST ONSET!

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13
Q

What is the Blood: Gas Partition Coefficient of sevoflurane?

A

0.69

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14
Q

What is the Blood: Gas Partition Coefficient of Nitrous Oxide?

A

0.46

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15
Q

How _________ the gas is determines how soon the gas will be turned off for emergence.

A

soluble.

Less soluble turn gas (desflurane) will be turned off toward the end of surgery. More soluble gas (isoflurane) will be turned off sooner.

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16
Q

What is the value for MACawake

A

0.3 - 0.5 MAC

Patient will be able to respond to touch and sound, there will be protective airway reflexes.

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17
Q

What is the value for MACbar

A

1.7 - 2.0 MAC

BAR- Blunt Autonomic (Adrenergic) Responses.

At MACbar there will be no SNS response to intubation.

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18
Q

What are the two biggest factors that alter MAC?

A

Body Temperature
Age- 6% per decade (under 30, above 50)

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19
Q

Factors that increase MAC.

A

Hyperthermia
Excess pheomelanin production (red-heads)
Drug-induced increase in catecholamine levels
Hypernatremia

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20
Q

Factors that decrease MAC.

A

Hypothermia
Pre-op Meds (BZD), intraop opioids
Alpha-2 agonist (precedex, clonidine)
Acute EtOH ingestion
Pregnancy
Post partum (12-72 hours)
Lidocaine
PaO2 < 38 mmHg
Mean BP < 40 mmHg
Cardiopulmonary Bypass
Hyponatremia

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21
Q

There will be a loss of consciousness by the inhibitory transmission of GABA in the ____ and especially the ____.

A

Brain and RAS

There will be potentiation of glycine activation in the brainstem.

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22
Q

Anesthesia affects spinal immobility by depressing excitatory ____ and ____ receptors.

Spinal immobility is also affected by enhancing inhibitory ____ and acts on sodium channels to block the release of ____.

A

AMPA
NMDA
glutamate receptors

Spinal immobility is also affected by enhancing inhibitory glycine and acts on sodium channels to block the release of glutamate.

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23
Q

What is the pressure that would be exerted by one of the gases in a mixture if it occupied the same volume on its own?

A

Partial Pressure

Sum of the partial pressures = total pressure (Dalton’s Law)

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24
Q

The pressure at which the vapor and liquid are at equilibrium.

A

Vapor Pressure

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25
Q

The ratio of by-pass gas/gas through the vaporizer compartment.

A

Splitting Ratio

26
Q

What kind of vaporizer increases the gas-liquid interface and improves the efficiency of vaporization?

A

Flow-over vaporizer

27
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
28
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.

29
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

30
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).

31
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

32
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

33
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

34
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.

35
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).

36
Q

How do volatile anesthetics affect CBF?

A

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

37
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.

38
Q

What is the volatile of choice for neuro anesthetics?

A

Sevoflurane can preserve autoregulation up to 1 MAC.

39
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)

40
Q

At what MAC will there be an increase ICP?

How much will ICP increase?

A

0.8 MAC

Increase by 7 mmHg.

41
Q

At what MAC will there be apnea?

A

1.5 to 2.0 MAC

42
Q

Hypoxic responses are mediated by the ____.

How do volatile anesthetics affect hypoxic responses?

A

Carotid bodies (peripheral chemoreceptors)

Blunt hypoxic response

43
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.

44
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.

45
Q

At what MAC will the portal vein flow increase?

A

1 to 1.5 MAC.

(Iso, Des, Sevo)

46
Q

Fluoride metabolites causes ____, ____, and _____.

A

Hyperosmolarity
Hypernatremia
Increase Creatinine

47
Q

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

A

There will be a rise in ET CO2.

48
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.

49
Q

What happens if you intubate with Vecuronium and you give Rocuronium for maintenance?

A

The two non-depolarizing NMBDs can potentiate each other and prolong the duration of the recovery period.

50
Q

The cardiovascular effects of non-depolarizing NMBD are due to what 3 factors?

A
  • Release of histamine
  • Effects on cardiac muscarinic receptors
  • Effects on nAChRs at autonomic ganglia
51
Q

What non-depolarizing NMBD has the same dose for ED95 and ANS stimulation (tachycardia)?

A

Pancuronium (sympathomimetic) will result in tachycardia at the ED95 dose. This can be offset by giving a narcotic.

Be mindful in administering pancuronium in patients with coronary artery disease, aortic stenosis, cardiac issues, etc…

52
Q

what is the MAC of CO2?

53
Q

how do you speed up equilibrium of blood:gas (Fa/Fi ratio)?

A
  • concentration effect
  • second gas effect
  • decreased CO
  • increase alveolar Vm and inc FGF
  • decrease FRC
54
Q

MAC of desflurane (Suprane)

55
Q

MAC of sevoflurane (Ultane)

56
Q

MAC of isoflurane (Forane)

57
Q

MAC of halothane

58
Q

MAC of N2O

59
Q

what is the MOA of volatiles in the brain?

A

GABAa agonist
—–increased frequency/duration of Cl- pore opening
—–inhibits NT
release presynaptically to decrease membrane potential post-synaptically

60
Q

what is the MOA of volatiles in the SPINAL CORD to produce immobility in ventral horn?

A
  • glycine-R stimulation
  • NMDA-r inhibition
  • Na+ channel inhibition
  • K+ channel potentiation

so NOT d/t GABAa!!!

Clinicals (10 decks)

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