Volatile Anesthetics Flashcards
How does halothane cause adverse effects on the liver?
Halothane decreases hepatic blood flow by increasing hepatic artery vascular resistance. One risk is the development of halothane hepatitis.
T or F: the most significant cause of fluoride toxicity is thought to be production of inorganic fluoride from intrarenal metabolism of methoxyflurane.
True
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.
True- one should limit inhalational anesthetics to less than 0.5 MAC.
SSEPs are performed to asses intraoperative neuronal pathway dysfunction.
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.
True
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.
True
T or F: volatile anesthetics blunt the hypoxic respiratory drive and the hypercarbic respiratory drive.
True
T or F: nitrous oxide increases CBF, ICP, and CMRO2.
True
T or F: nitrous oxide potentiates neuromuscular blockade.
True
T or F: nitrous oxide is associated with significant PONV.
True
T or F: halothane is metabolized to trifluoroacetic acid.
True
T or F: halothane causes a dose-dependent reduction in MAP 2/2 cardiac depression.
True
T or F: When using SEVOFLURANE, there is the risk of accumulating compound A with increased respiratory gas temperature and low flow anesthesia.
True- use flows of at least 2L/min
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).
True
T or F: rapid increases in concentration levels of isoflurane and desflurane can lead to transient tachycardia and high blood pressure.
True- more seen with des than iso
T or F: at 2 MAC of isoflurane, electrical silence on EEG is demonstrated.
True
T or F: of the volatiles, isoflurane is the only one shown to demonstrate coronary vasodilation.
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.
What is the order of least to most metabolism of the following volatile agents?
desflurane
isoflurane
sevoflurane
halothane
desflurane –> isoflurane –> sevoflurane –> halothane
T or F: isoflurane, desflurane, and sevoflurane preserve hepatic blood flow, but halothane decreases hepatic blood flow.
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.
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?
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.
What is the vapor pressure of desflurane at room temperature? What is the partial pressure to which desflurane is heated?
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.
What is the vapor pressure of the volatile anesthetic agents, from least to greatest?
methoxyflurane (23) sevoflurane (160) enflurane (172) isoflurane (240) halothane (243) desflurane (669)
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.
Isoflurane and halothane in a sevoflurane or enflurane vaporizer would lead to a higher than expected concentration that would be delivered from the vaporizer.
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.
True- consider this if you place sevoflurane/enflurane into an isoflurane or halothane vaporizer.
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.
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.
T or F: halothane and isoflurane depress SA node automaticity and make AV node refractory.
True
Vapor pressure of methoxyflurane
23
Vapor pressure of sevoflurane
160
Vapor pressure of enflurane
172
Vapor pressure of isoflurane
240
Vapor pressure of halothane
243
Vapor pressure of desflurane
660
