Gases Equilibration and Partial Pressure in Anesthesia

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What is the driving force for movement of anesthetic agent into the blood?

Alveolar to mixed venous partial pressure difference

How does increasing cardiac output affect the rate of rise of the anesthetic agent FA/FI?

Slows down the rise of FA/FI

What factor decreases the volume in the volume/flow equation, resulting in a shorter time constant for the rise of FA/FI?

Decreased FRC

How does overpressurization affect the rate of rise of the anesthetic agent FA/FI?

Speeds up the rise of FA/FI

What is clinically insignificant with volatiles but makes a difference with agents given in high concentrations like nitrous oxide?

Concentration effect

Which factor initially produces a rapid change in PA-PV, resulting in a rapid reduction in PA-PV and a greater change in FA/FI?

Increased alveolar to mixed venous partial pressure difference

What is typically described as the ratio of FA/FA0?


Why does the washout of anesthetic happen much more rapidly with desflurane, sevoflurane, and N2O?

Due to decreased solubility

What is required for emergence during recovery from anesthesia?

80-90% reduction in FA

During the washout of nitrous oxide, what can potentially worsen due to hypoxia?

Respiratory drive

What happens during Stage II of anesthesia described in Miller's stages?

Eyelash reflex reappears

What is the main factor that leads to washout of large volumes of nitrous oxide causing diffusion hypoxia?

Reduction in alveolar partial pressures of oxygen

What is the main reason why washout of less-soluble inhaled anesthetics is more rapid than that of more-soluble agents?

Faster diffusion across alveoli to blood

How does the vapor pressure of a volatile anesthetic relate to temperature?

Is directly proportional to temperature

What does the boiling point of an anesthetic indicate?

The energy required for conversion to vapor

What is the function of an anesthetic vaporizer?

To allow transfer of the anesthetic to the vaporizer without atmospheric exposure

At equilibrium, what is true about the partial pressure of inhaled anesthetics in alveoli, blood, and CNS (central nervous system)?

They are all equal

Why can anesthetizing concentrations of volatile anesthetic be rapidly achieved in the CNS?

Rapid delivery and removal from lungs compared to metabolism and redistribution effects

What is the relationship between the rate of induction of inhaled anesthetic and the ratio of FA to FI?

They are directly proportional

How is FA defined in the context of measuring the concentration of inhaled anesthetic in the brain?

FA = PA/Pbarometric

Which formula represents how the concentration of a substance in a given volume approaches that of the flow entering it according to first-order kinetics?

FI = FFGO(1-e-T/τ)

What does the time constant (τ) represent in the context of volume and flow?

It represents volume divided by flow

In the example given with a flow rate of 2 l/min and a volume of 8 liters, how long would it take to achieve a 95% change in concentration based on the time constant?

12 minutes

What is the most effective method mentioned to increase the rate of rise of FA/FI?

Decrease the time constant by increasing the flow rate

How does respiratory depression impact the rate of rise of FA?

Decreases the rate of rise of FA

What effect does reducing cardiac output have on the rate of rise of FA/FI?

Increases the rate of rise of FA/FI

What is a consequence of cardiovascular depression related to high concentrations of volatile agents?

Increases the alveolar partial pressure

What occurs when there is a right-to-left shunt in terms of FA and arterial partial pressure?

Increase in FA and decrease in arterial partial pressure

What is the impact of metabolic pathways being rapidly saturated for inhalation anesthetics?

Minimal metabolism of the drug

How are the pharmacokinetics of inhalational agents best described according to the text?

5 compartment model

Learn about how gases equilibrate based on partial pressure and not concentration in anesthesia. Understand the concept of partial pressure and its role in the exchange of gases between alveoli and blood. Explore the relationship between solubility in blood and the rate at which partial pressures equalize.

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