3 Mar 25 Inhaled Anesthetics Pt 1 Flashcards
What are the two main laws discussed in relation to inhaled anesthetics?
Boyle’s law and Fick’s law
Boyle’s law relates pressure and volume at constant temperature, while Fick’s law deals with diffusion of gases.
Define the concentration effect in inhaled anesthetics.
Higher inspired concentrations lead to faster induction
This effect is significant in achieving rapid anesthesia.
What is the second gas effect?
Using nitrous oxide to enhance the potency of other anesthetics
This effect accelerates the induction process.
What are MAC values?
Minimum Alveolar Concentration values indicating the concentration needed to prevent movement in response to a stimulus
MAC values vary between anesthetics and are influenced by patient factors.
How does solubility affect the onset and offset of anesthetics?
Higher solubility leads to slower onset and offset
Desflurane has a faster onset and offset compared to isoflurane and sevoflurane.
Fill in the blank: According to _______ law, pressure and volume are inversely proportional at constant temperature.
Boyle’s
What is the primary factor affecting the diffusion of gases according to Fick’s law?
Partial pressure gradient, solubility of the gas, and thickness of the membrane
These factors determine how easily gases can diffuse into the bloodstream.
True or False: Higher temperatures increase the likelihood of anesthetics leaving the blood.
True
What does the blood-gas partition coefficient indicate?
How anesthetics distribute into different body compartments at equilibrium
It is crucial for understanding the pharmacokinetics of anesthetics.
What is the impact of nitrous oxide on body regions with different compliance?
It can cause expansion in compliant areas like the gut while causing pain in rigid areas like the inner ear
This is due to nitrous oxide’s diffusibility.
What is the significance of end-tidal exhaled gas?
It helps measure the partial pressure of anesthetics in the alveoli, which correlates with brain pressure
This is essential for assessing anesthesia depth.
List the factors that influence MAC values.
- Age
- Body temperature
- Patient characteristics
These factors must be considered for effective anesthesia management.
What role do vaporizers play in anesthesia?
They convert liquid anesthetics to gas form for patient inhalation
Proper use of vaporizers is critical for effective anesthesia delivery.
What is the function of flow meters in anesthesia machines?
Controlling the flow of fresh gas to the vaporizer
They help ensure accurate delivery of anesthetic concentrations.
Fill in the blank: The process of waking up from anesthesia is called _______.
emergence
What is the relationship between solubility and emergence from anesthesia?
Lower solubility leads to faster emergence
Desflurane allows quicker recovery compared to isoflurane and sevoflurane.
Explain how cardiac output affects anesthetic uptake.
Higher cardiac output may reduce the time for gas molecules to enter the bloodstream
Slower cardiac output allows more gas to be absorbed.
What is the concentration effect in relation to inhaled anesthetics?
The concentration effect impacts the inspired pressure on the rate of rise in alveolar pressure
A higher concentration of anesthetic in the alveoli leads to a faster rise in its concentration in the bloodstream and ultimately the brain.
How does increasing the inspired pressure of a volatile anesthetic affect the rate of sleep induction?
The higher the inspired pressure, the more rapidly the alveolar pressure approaches the inspiratory pressure
This concentration effect can lead to a quicker onset of anesthesia.
What is the role of cardiac output in the uptake of volatile anesthetics?
Cardiac output can be adjusted to increase or decrease the uptake and distribution of volatiles
Vasodilation can decrease preload and slow down cardiac output.
What is the process of how inhaled anesthetics lead to sleep?
Inhaled anesthetics move from the vaporizer to the inspiratory limb, to the lungs, to the blood, and finally to the brain
This pathway is crucial for achieving anesthesia.
Fill in the blank: The higher the concentration of anesthetic in the alveoli, the _______.
faster the rise into the pulmonary vessels
What is over pressurization in the context of anesthesia?
A large increase in the inspired fraction of anesthetic
This technique can induce sleep rapidly but must be managed carefully to avoid side effects.
What is the second gas effect?
The use of a high volume of gas, such as nitrous, to accelerate the uptake of another gas
This effect enhances the concentration of the second gas in the alveoli.
How does nitrous oxide enhance the concentration effect of another anesthetic?
Nitrous oxide is very diffusible, allowing it to leave the alveoli quickly, thus concentrating the other anesthetic
This can lead to faster induction of anesthesia.
What happens to the volume change in the gut when nitrous oxide is administered?
Nitrous can cause a significant increase in volume due to its diffusibility into air-filled spaces
This can complicate surgical procedures if not managed properly.
True or False: The compliance of the walls in gas-filled spaces affects pressure changes when nitrous is administered.
True
If the walls are compliant, pressure changes minimally; if not compliant, pressure changes significantly.
What is the impact of nitrous on retinal repairs in surgical patients?
Permanent vision loss can occur after prolonged exposure to nitrous during surgery
This emphasizes the need for careful selection of anesthetics based on the procedure.
What can increase the speed of induction of anesthesia?
Increasing respiratory rate and input of anesthetic
Both factors enhance the inspired pressure and thus the uptake of anesthetics.
What effect does increased respiratory rate have on induction speed?
Increases induction speed by increasing inspired pressure relative to alveolar pressure.
What happens to the respiratory rate and cardiac output as a person goes to sleep?
Both respiratory rate and cardiac output usually slow down.
How does the body respond to high concentrations of volatile anesthetics during induction?
The body slows the rate of induction as it perceives sufficient anesthetic effect.
What is solubility in the context of anesthetics?
A ratio of how the anesthetic is distributed into different compartments at equilibrium.
What happens to the solubility of gases as temperature increases?
More gas leaves the blood and enters the brain or fat.
What is the blood gas partition coefficient for desflurane?
0.42.
How does solubility affect the speed of going to sleep?
Lower solubility results in faster induction and awakening.
What is the blood fat partition coefficient for desflurane?
27.
Fill in the blank: If a gas is poorly soluble, it __________ to leave the blood and go to the brain.
wants
True or False: Higher blood gas coefficients generally indicate quicker recovery from anesthesia.
False.
What can happen when turning off a volatile anesthetic?
Gas can redistribute from fat back to the brain, potentially causing drowsiness.
What is the blood gas partition coefficient for isoflurane?
1.46.
In which type of patient would you prefer to use desflurane over isoflurane?
In morbidly obese patients undergoing gastric bypass surgery.
What is the primary method for waking a patient from anesthesia?
Turning off the anesthetic gases.
What does emergence from anesthesia depend on?
Length of anesthetic and solubility in blood versus fat.
What happens to the amount of anesthetic in the blood when a patient is waking up?
It decreases as the anesthetic is eliminated.
What is the blood gas partition coefficient for sevoflurane?
0.69.
Fill in the blank: If the solubility of a gas is high, it __________ to go to the brain.
likes to stay in the blood
What is the significance of the blood fat partition coefficient?
Indicates how much anesthetic can be sequestered in fat.
What is a common outcome after surgery when patients regain consciousness?
They often take a nap due to residual anesthetic in fat.
What is the blood fat partition coefficient for isoflurane?
44.9.
What does a higher blood fat partition coefficient imply about an anesthetic?
It is more likely to be sequestered in fat and can affect recovery time.
True or False: All volatile anesthetics have the same recovery time.
False.
What happens to the timing of volatile anesthetics when the inspired pressure is turned to zero?
The vaporizer is completely off.
This highlights the importance of managing anesthetic gases during patient transport.
Which volatile anesthetic is considered the fastest for wake-up?
Sevoflurane.
Halothane and isoflurane wake-up times increase considerably compared to sevoflurane.
What is MAC in the context of anesthesia?
Minimal alveolar concentration.
It is the concentration at one atmosphere that prevents skeletal muscle movement in response to supramaximal stimuli in 50% of patients.
What is the typical MAC value for desflurane?
6.6%.
This is the concentration necessary to achieve the desired anesthetic effect.
What MAC value is generally required to prevent movement in 98% of patients?
1.3 MAC.
This is used to ensure that the majority of patients remain still during surgical procedures.
At what MAC value will a patient begin to respond to stimuli during recovery?
0.3 to 0.5 MAC.
At this point, the patient may open their eyes or respond to a sternal rub.
What factors can increase MAC requirements?
- Hyperthermia
- Younger age
- Redheads
- Pheochromocytomas
- Hypernatremia.
These factors can lead to an increased need for volatile anesthetics.
What factors can decrease MAC requirements?
- Hypothermia
- Synergistic medications
- Alpha-2 agonists
- Alcohol ingestion
- Pregnancy
- Severe hypoxia
- Low blood pressure.
These conditions generally reduce the amount of anesthetic needed.
How does aging affect MAC values?
Every decade, MAC decreases by approximately 6%.
Older patients typically require less anesthetic.
What is the significance of the vaporizer’s color coding?
Ensures that the correct anesthetic is used and prevents cross-filling of vaporizers.
Each volatile anesthetic has a specific color that corresponds to its container and vaporizer.
What is the typical MAC for isoflurane?
1.15%.
This value is crucial for anesthetic dosing.
What happens to autonomic reflexes at 1.7 to 2 MAC?
Autonomic reflexes are blunted.
At this depth of anesthesia, blood pressure and heart rate responses are diminished.
What is the recovery time for isoflurane after 2 hours of anesthesia?
About 30 minutes.
This contrasts with faster-acting agents like sevoflurane.
True or False: Chronic alcohol abuse affects MAC values.
False.
The body adapts to chronic alcohol use, resulting in a new normal for anesthetic requirements.
What is the impact of hypothermia on volatile anesthetic requirements?
Decreases MAC requirements.
Patients who are hypothermic may require less anesthetic to achieve the desired effect.
What is the role of GABA in anesthesia?
It acts as an inhibitory neurotransmitter affecting loss of consciousness.
Most volatile anesthetics enhance GABAergic activity.
What is the purpose of vaporizers in anesthesia?
Vaporizers hold liquid anesthetics and convert them to gas form for delivery to patients.
What is the relationship between vapor pressure and temperature?
Vapor pressure increases with temperature.
Define partial pressure.
Partial pressure is the pressure exerted by a single gas in a mixture of gases.
What is Dalton’s Law?
Dalton’s Law states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of each gas.
What is the typical composition of room air in terms of nitrogen and oxygen?
Room air is approximately 79% nitrogen and 21% oxygen.
Fill in the blank: The total of all partial pressures in a compartment must equal _______.
100%
How does altitude affect vaporization?
Vaporization changes with altitude unless machines are programmed to accommodate hydro pressure.
What happens to the vapor pressure of a substance when it is heated?
Heating increases the vapor pressure.
True or False: The vaporizer must be set correctly to vaporize the correct gas.
True
What is the significance of the term ‘MAC’ in anesthesia?
MAC refers to the minimum alveolar concentration needed to prevent movement in 50% of patients.
What is the role of oxygen in the anesthesia process?
Oxygen is used to ensure patients are well-oxygenated during and after anesthesia.
What does the term ‘end-tidal’ indicate in anesthetic monitoring?
End-tidal refers to the concentration of a gas exhaled at the end of expiration.
What is a splitting valve in a vaporizer?
A splitting valve controls the ratio of fresh gas flow into the vaporizing chamber and bypassing it.
Fill in the blank: The higher the flow rate through the vaporizer, the _______ the contact time with the liquid anesthetic.
lower
What is the difference between a flow-over vaporizer and a wick vaporizer?
A wick vaporizer has increased surface area for evaporation compared to a flow-over vaporizer.
What is the function of the control dial on a vaporizer?
The control dial adjusts the concentration of gas delivered to the patient.
How do vaporizers prevent the wrong vapor from being used?
Vaporizers are designed with specific shapes that prevent cross-filling between different vaporizers.
What is the significance of the term ‘vapor pressure’?
Vapor pressure is the pressure exerted by a vapor when it is in equilibrium with its liquid.
What does MAC stand for in pharmacodynamics?
Minimum alveolar concentration
MAC is defined as the concentration at 1 atm that prevents skeletal muscle movement in response to supramaximal, painful stimulation in 50% of patients.
What is the MAC value for nitrous oxide?
104
This indicates the minimum alveolar concentration required for nitrous oxide.
At what age does MAC peak?
1 year old
This is significant in understanding the variability of anesthetic requirements across different ages.
What factors can alter MAC?
- Body temperature
- Age (6% decrease per decade)
- Hyperthermia
- Hypothermia
- Preoperative medications
- Acute alcohol ingestion
- Pregnancy
- Lidocaine
- Cardiopulmonary bypass
- Hyponatremia
- Chronic alcohol abuse
- Gender
- Duration of anesthesia
These factors can significantly influence anesthetic requirements.
What does the term ‘washout’ refer to in the context of inhaled anesthetics?
Rate of decrease in Pbr
Washout occurs when the inhaled agent is turned off, affecting how quickly the anesthetic leaves the brain.
What is the vapor pressure of desflurane?
669 torr
This high vapor pressure indicates that desflurane is more volatile compared to other anesthetic agents.
What is Boyle’s Law?
Pressure and volume of gas are inversely proportional at constant temperature
This principle is important in understanding the behavior of gases in anesthesia.
What is the concentration effect?
The impact of PI on the rate of rise of PA
A higher inspired concentration (PI) of a volatile anesthetic leads to a more rapid increase in alveolar concentration (PA).
What is the significance of Fick’s Diffusion Law in anesthesia?
Describes the diffusion of gas into pulmonary capillary blood
It considers factors like partial pressure gradient, gas solubility, and membrane thickness.
Fill in the blank: The ______ is a ratio of how the inhaled anesthetic distributes between two compartments at equilibrium.
Solubility
Solubility is crucial for understanding how anesthetics behave in the body.
What is the primary mechanism of action of volatile anesthetics in the brain?
Inhibitory transmission of GABA
This mechanism is crucial for the loss of consciousness during anesthesia.
True or False: The concentration effect and second gas effect are the same.
False
While both involve the uptake of anesthetics, they refer to different mechanisms.
What is the purpose of vaporizers in anesthesia?
Change liquid to vapor and add vapor to fresh gas flow
Vaporizers are essential for delivering volatile anesthetics in a controlled manner.
What happens to anesthetic gases during positive pressure ventilation?
Gases flow from high pressure to low pressure
This principle is important in ensuring that anesthetics are effectively delivered to the lungs.
What does ‘PA’ refer to in the context of anesthesia?
Alveolar pressure
PA is an important indicator of the depth of anesthesia and recovery.
List the factors that influence the uptake of inhaled anesthetics.
- Partial pressure gradients
- Alveolar ventilation
- Anesthetic machine to alveoli
- Blood: gas partition coefficient
- Cardiac output
- A-v partial pressure difference
- Cerebral blood flow
These factors determine how quickly anesthetics are absorbed and distributed in the body.
What is the vapor pressure of halothane?
243 torr
This indicates its volatility compared to other anesthetics.
What does the term ‘second gas effect’ refer to?
Uptake of a high-volume gas (N2O) accelerates a concurrently administered companion gas
This effect enhances the uptake of the second gas due to increased concentration gradients.
