Volatile Anesthetics

Question 1

How does halothane cause adverse effects on the liver?

Answer 1

Halothane decreases hepatic blood flow by increasing hepatic artery vascular resistance. One risk is the development of halothane hepatitis.

Question 2

T or F: the most significant cause of fluoride toxicity is thought to be production of inorganic fluoride from intrarenal metabolism of methoxyflurane.

Answer 2

True

Question 3

T or F: Inhalational agents cause an increase in latency and decrease in the amplitude of response on SSEP monitoring and can mimic changes seen during episodes of neurologic dysfunction.

Answer 3

True- one should limit inhalational anesthetics to less than 0.5 MAC.

SSEPs are performed to asses intraoperative neuronal pathway dysfunction.

Question 4

T or F: one of the effects of volatile anesthetics on ventilation include an increase in respiratory rate and a decrease in tidal volume that results in maintenace of near-normal minute ventilation.

Answer 4

True

Question 5

T or F: while under volatile anesthesia, gas exchange progressively worsens with increasing anesthetic concentrations and PaCO2 rises. This occurs despite minute ventilation being maintained, because dead-space ventilation increases compared to alveolar ventilation due to the decrease in tidal volume.

Answer 5

True

Question 6

T or F: volatile anesthetics blunt the hypoxic respiratory drive and the hypercarbic respiratory drive.

Answer 6

True

Question 7

T or F: nitrous oxide increases CBF, ICP, and CMRO2.

Answer 7

True

Question 8

T or F: nitrous oxide potentiates neuromuscular blockade.

Answer 8

True

Question 9

T or F: nitrous oxide is associated with significant PONV.

Answer 9

True

Question 10

T or F: halothane is metabolized to trifluoroacetic acid.

Answer 10

True

Question 11

T or F: halothane causes a dose-dependent reduction in MAP 2/2 cardiac depression.

Answer 11

True

Question 12

T or F: When using SEVOFLURANE, there is the risk of accumulating compound A with increased respiratory gas temperature and low flow anesthesia.

Answer 12

True- use flows of at least 2L/min

Question 13

T or F: More than other volatiles, desflurane is dessicated by carbon dioxide absorbent (particularly barium hydroxide lime, but also sodium and potassium hydroxide) into clinically significant levels of carbon monoxide (can be visible by ABG).

Answer 13

True

Question 14

T or F: rapid increases in concentration levels of isoflurane and desflurane can lead to transient tachycardia and high blood pressure.

Answer 14

True- more seen with des than iso

Question 15

T or F: at 2 MAC of isoflurane, electrical silence on EEG is demonstrated.

Answer 15

True

Question 16

T or F: of the volatiles, isoflurane is the only one shown to demonstrate coronary vasodilation.

Answer 16

True- this is why we use isoflurane in cardiac cases! Desflurane and halothane have a smaller affect on coronary vasodilation, sevoflurane does not demonstrate coronary vasodilation.

Question 17

What is the order of least to most metabolism of the following volatile agents?

desflurane
isoflurane
sevoflurane
halothane

Answer 17

desflurane –> isoflurane –> sevoflurane –> halothane

Question 18

T or F: isoflurane, desflurane, and sevoflurane preserve hepatic blood flow, but halothane decreases hepatic blood flow.

Answer 18

True- Isoflurane is a vasodilator of the hepatic circulation and provides beneficial effects on hepatic oxygen delivery. In patients with 1.5% end-tidal isoflurane, total hepatic blood flow and hepatic artery blood flow were maintained while portal vein flow was increased.

In addition, administration of 1 MAC of isoflurane plus nitrous oxide demonstrated increases in hepatic blood flow and hepatic venous oxygen saturation. Similar to isoflurane, hepatic blood flow is maintained during administration of sevoflurane and desflurane. In contrast, administration of halothane decreases hepatic blood flow.

Question 19

T or F: the partial pressure of most anesthetic vapors is dependent on temperature, not barometric pressure, and in an extremely cold environment more anesthetic vapor may be required. What is the exception to this rule?

Answer 19

True- halogenated vapors are delivered at a constant potency at constant temperature irrespective of altitude.

Desflurane is the exception to this rule, as even small changes in both temperature and barometric pressure will affect vaporizer output. The desflurane Datex-Ohmeda vaporizer requires manual adjustments of the concentration control dial at altitudes other than sea level to maintain constant partial pressure of anesthetic.

Remember: partial pressure is the important parameter physiologically, not the concentration delivered.

Question 20

What is the vapor pressure of desflurane at room temperature? What is the partial pressure to which desflurane is heated?

Answer 20

Vapor pressure at room temperature is 660 mmHg.

Partial pressure to which it is heated is 1500 mmHg in order to ensure a consistent concentration of desflurane released from the vaporizer independent of changes in barometric pressure or temperature.

Question 21

What is the vapor pressure of the volatile anesthetic agents, from least to greatest?

Answer 21

methoxyflurane (23)
sevoflurane (160)
enflurane (172)
isoflurane (240)
halothane (243)
desflurane (669)

Question 22

T or F: if a vaporizer is filled with a volatile anesthetic that has a greater saturated vapor pressure, a higher than expected concentration would be delivered from that vaporizer.

Answer 22

Isoflurane and halothane in a sevoflurane or enflurane vaporizer would lead to a higher than expected concentration that would be delivered from the vaporizer.

Question 23

T or F: if a vaporizer is filled with a volatile anesthetic that has a lower saturated vapor pressure, a lower than expected concentration would be delivered from that vaporizer.

Answer 23

True- consider this if you place sevoflurane/enflurane into an isoflurane or halothane vaporizer.

Question 24

T or F: A reduction in cardiac output will have less effect on the rate of change to the Fa/Fi ratio for a poorly soluble agent than for a highly soluble agent. Therefore, conditions that lower the cardiac output will increase the alveolar anesthetic concentrations more when using anesthetics that have a greater solubility.

Answer 24

True:

The blood-gas partition coefficients for the commonly used anesthetic gases include the following:

Isoflurane, 1.46
Sevoflurane, 0.65
Desflurane, 0.42
Nitrous oxide, 0.46
Compared to sevoflurane, desflurane, and nitrous oxide, isoflurane has the largest blood-gas partition coefficient, is the least soluble anesthetic gas, and would have the lowest impact on the rate of change to Fa/Fi during conditions that result in decreased cardiac output.

Question 25

T or F: halothane and isoflurane depress SA node automaticity and make AV node refractory.

Answer 25

True

Question 26

Vapor pressure of methoxyflurane

Answer 26

23

Question 27

Vapor pressure of sevoflurane

Answer 27

160

Question 28

Vapor pressure of enflurane

Answer 28

172

Question 29

Vapor pressure of isoflurane

Answer 29

240

Question 30

Vapor pressure of halothane

Answer 30

243

Question 31

Vapor pressure of desflurane

Answer 31

660