volatiles

Question 1

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

from old pharm class

Answer 1

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

Question 2

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

from old pharm class

Answer 2

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

Question 3

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

Answer 3

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.

Question 4

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

Answer 4

P_aCO2

Question 5

Differentiate between spontaneous ventilation and mechanical ventilation.

Answer 5

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.

Question 6

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

Answer 6

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

Question 7

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

Answer 7

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

Question 8

What is the Blood:Gas Partition Coefficient of Halothane?

Answer 8

2.54

Question 9

What is the Blood:Gas Partition Coefficient of Desflurane?

Answer 9

0.42

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

Question 10

Which one has the lowest solubility?

A. Desflurane
B. Sevoflurane
C. Isoflurane

Answer 10

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.

Question 11

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

Answer 11

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.

Question 12

What is the Blood: Gas Partition Coefficient of Isoflurane?

Answer 12

1.46

most soluble in blood = SLOWEST ONSET!

Question 13

What is the Blood: Gas Partition Coefficient of sevoflurane?

Answer 13

0.69

Question 14

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

Answer 14

0.46

Question 15

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

Answer 15

soluble.

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

Question 16

What is the value for MAC_awake

Answer 16

0.3 - 0.5 MAC

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

Question 17

What is the value for MAC_bar

Answer 17

1.7 - 2.0 MAC

BAR- Blunt Autonomic (Adrenergic) Responses.

At MACbar there will be no SNS response to intubation.

Question 18

What are the two biggest factors that alter MAC?

Answer 18

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

Question 19

Factors that increase MAC.

Answer 19

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

Question 20

Factors that decrease MAC.

Answer 20

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

Question 21

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

Answer 21

Brain and RAS

There will be potentiation of glycine activation in the brainstem.

Question 22

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 ____.

Answer 22

AMPA
NMDA
glutamate receptors

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

Question 23

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?

Answer 23

Partial Pressure

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

Question 24

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

Answer 24

Vapor Pressure

Question 25

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

Answer 25

Splitting Ratio

Question 26

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

Answer 26

Flow-over vaporizer

Question 27

What are the four functions of the anesthesia circuit?

Answer 27

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

Question 28

What is high-flow inhalation anesthesia? What are some downsides to high-flow anesthesia?

Answer 28

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.

Question 29

What is low-flow inhalation anesthesia? What are some downsides to low-flow anesthesia?

Answer 29

Fresh gas flow (FGF) less than minute ventilation. Low cost, conserves gas, less/cooling, and drying. A very slow change in anesthesia

Question 30

How do volatile anesthetics cause bronchodilation?

Answer 30

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).

Question 31

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

Answer 31

1 to 2 MAC

Question 32

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

Answer 32

Sevoflurane (best bronchodilator) Desflurane

Question 33

At ____ MAC, wakefulness changes to unconsciousness. What MAC will there be burst suppression? What MAC will there be electrical silence?

Answer 33

0.4 1.5 2.0

Question 34

How will volatile anesthetics affect somatosensory evoked potentials (SSEP) or motor evoked potentials (MEP)? How is this a problem?

Answer 34

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.

Question 35

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

Answer 35

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).

Question 36

How do volatile anesthetics affect CBF?

Answer 36

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

Question 37

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

Answer 37

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

Question 38

What is the volatile of choice for neuro anesthetics?

Answer 38

Sevoflurane can preserve autoregulation up to 1 MAC.

Question 39

How does hyperventilation decrease ICP?

Answer 39

Inducing hypocapnia via hyperventilation reduces PaCO2, which will cause vasoconstriction in the cerebral arterioles decreasing ICP. *Short-term fix for increasing ICP (15 mins)*

Question 40

At what MAC will there be an increase ICP? How much will ICP increase?

Answer 40

0.8 MAC Increase by 7 mmHg.

Question 41

At what MAC will there be apnea?

Answer 41

1.5 to 2.0 MAC

Question 42

Hypoxic responses are mediated by the ____. How do volatile anesthetics affect hypoxic responses?

Answer 42

Carotid bodies (peripheral chemoreceptors) Blunt hypoxic response

Question 43

What cardiac dysrhythmias can be presented with volatile anesthetics?

Answer 43

Prolonged QT interval in healthy patients d/t inhibition of potassium currents. Potentially increase risk of Torsades.

Question 44

How do volatile anesthetics affect hepatic blood flow?

Answer 44

Total hepatic blood flow and hepatic artery flow are maintained. Volatiles **dilate the portal vein** which will increase blood flow.

Question 45

At what MAC will the portal vein flow increase?

Answer 45

1 to 1.5 MAC. (Iso, Des, Sevo)

Question 46

Fluoride metabolites causes ____, ____, and _____.

Answer 46

Hyperosmolarity Hypernatremia Increase Creatinine

Question 47

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

Answer 47

There will be a rise in ET CO2.

Question 48

How can Sevoflurane spontaneously combust?

Answer 48

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.*

Question 49

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

Answer 49

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

Question 50

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

Answer 50

* Release of histamine * Effects on cardiac muscarinic receptors * Effects on nAChRs at autonomic ganglia

Question 51

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

Answer 51

**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...*

Question 52

what is the MAC of CO2?

Answer 52

200%

Question 53

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

Answer 53

* concentration effect * second gas effect * decreased CO * increase alveolar Vm and inc FGF * decrease FRC

Question 54

MAC of desflurane (Suprane)

Answer 54

6.6%

Question 55

MAC of sevoflurane (Ultane)

Answer 55

1.8%

Question 56

MAC of isoflurane (Forane)

Answer 56

1.2%

Question 57

MAC of halothane

Answer 57

0.75%

Question 58

MAC of N2O

Answer 58

104%

Question 59

what is the MOA of volatiles in the **brain**?

Answer 59

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

Question 60

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

Answer 60

* glycine-R stimulation * NMDA-r inhibition * Na+ channel inhibition * K+ channel potentiation ## Footnote so NOT d/t GABAa!!!