Inhalation Anesthesia 1 Flashcards
Naming of covalent bonds is based on what?
How many bonds they share
1 Bond between Carbons is called what?
Alkane
2 Bonds between carbons is called what?
Alkene
3 bonds betweehn carbons is called what?
Alkyne
How are ethers chemically unique?
Two or more carbons surrounding an oxygen
All inhalation agents have no more than how many carbon atoms?
4
What chemical structure property will effect how well the drug produces immobility?
The length of the molecule.
Longer than 4-5 carbons/bond it will lose some of its effect
Describe the shape and relationship of length to diameter of inhalation agents:
Shape is spherical/cylindrical with a length less than 1.5 times the diameter.
What is the only modern inhaled anesthetic that is not a halogenated hydrocarbon?
Nitrous Oxide
What is the only Aliphatic used today?
Halothane
What group does isoflurane, desflurane, sevoflurane, and enflurane belong to?
They are all Ethers
What is halogenation?
The addition of fluorine (F), chlorine (Cl), bromine (Br), or iodine (I) replaces one or more of the carbon atoms in the chemical structure.
How is potency changed when an agent is halogenated?
Potency increases when lower atomic mass atom is exchanged with a higher atomic mass atom.
How are arrhythmogenic properties changed when an agent is halogenated?
Arrhythmogenic properties are increased when the agent is more halogenated (more substitutions)
How is flammability effected with halogenation?
Flammability is reduced when substituting hydrogens with halogens.
How is chemical stability effected with halogenation?
Chemical stability is increased when hydrogens are substituted with halogens.
Which inhaled anesthetic strongly resists biodegradation? and why?
Deflurane; because it’s only halogen is fluorine
Which group in the Periodic Table of Elements are the halogens from?
Group 17
What is unique about the physical properties of all elements in Group 17?
At STP, this group contains elements that are in all three states of matter (solids, liquids, gases)
Which anesthetic gas has Bromine as a halogen?
Halothane
How many fluorine does Enflurane have?
6
How many fluorine does sevoflurane have?
7
How many fluorine does desflurane have?
6
How many fluorine does isoflurane have?
5
Which anesthetic gas has the only degradation rate of 5-8%
Sevoflurane
Does increasing or decreasing the number of fluorine atoms on an anesthetic molecule slow biodegradation?
Increasing slows it.
Ex: Desflurane
Why is Halothane not being used actively anymore?
1:35,000 Hepatic injury
What are the pharmacokinetics of inhaled anesthetics in order chronilogically?
- Uptake (absorption phase).
- Biotransformation (Metabolic Phase).
- Elimination (excretion phase)
Of all the inhaled drugs we administer, which two are the only “true gases”?
N20 and O2.
All other agents are vapors or volatile liquids
Are inhaled anesthetics ionized or non-ionized?
Non-ionized
What is the desired site of action for inhaled anesthetics?
The Central nervous system
Define general anesthesia:
Induce and sustain a state of unconsciousness, amnesia, analgesia, immobility.
Do inhaled anesthetics eliminate pain?
No; do not have much effect on pain itself. They attenuate the stress response of painful stimuli (HR and BP). Can potentiate other analgesic medications
As lipid solubility decreases, what happens to potency?
It decreases. They are directly proportional.
What law is associated with lipid solubility and potency relationship?
Meyer-Overton Rule
How can inhaled anesthetics be reversed/eliminated?
By application of pressure via a gradient. Administering 100%.
As body temperature increases, what happens to anesthetic requirement?
Increases anesthetic requirement.
What is the current hypothesis on inhaled anesthetic pharmacodynamics?
They work via diverse mechanisms at diverse sites of action.
According to the current theory, what are the two main anatomical sites of action for inhaled anesthetics?
Supraspinal (brain) and spinal
How much drug to cause effects of amnesia, unconsciousness, immobility, and sedation?
Least amount drug needed for amnesia.
Then sedation.
Then unconsciousness.
Most drug needed for immobility.
What does the oil:gas coefficient tell us about an inhaled anesthetic?
How well the drug dissolves in a lipid which is a measure of potency. Higher the oil:gas coefficient, the higher the potency.
What does the blood:gas coefficient tell us about an inhaled anesthetic?
How easily the drug dissolves in blood which is a measure of how quickly the drug will get to brain. The higher this number, the slower it takes for the brain to see it.
How do inhaled anesthetics produce anesthesia?
Enhancing the function of inhibitory ion channels and by blocking the function of excitatory ion channels.
What does enhancing of inhibitory ion channels do to the neuron?
It leads to hyperpolarization.
What does blocking the function of excitatory ion channels prevent?
Prevents depolarization of the neuron by preventing passage of positive charges into the neuron.
What are the two inhibitory ion channels?
Glycine and GABA
Which inhibitory ion channel affects immobility and is located in spinal cord?
Glycine
Which inhibitory ion channel is associated with hypnosis?
GABA
Where are the GABA sites located?
In between the Alpha1 and Beta2
What is an example of an excitatory channel?
Glutamate.
Ligand gated receptors NMDA
Is immobility measurable?
Yes; through MAC
How is immobility achieved with inhaled anesthetics?
Activation of descending noradrenergic pathways. Activation of these pathways inhibit nociceptive input in the dorsal horn of the spinal cord.
How is amnesia achieved with inhaled anesthetics?
Supraspinal structures such as the amygdala, hippocampus, and cortex are considered highly probable targets of inhaled anesthetics.
Does amnesia have a reliable measure?
No; there is no definitive way to ensure amnesia.
At equilibrium of anesthetic gas, what is the PP of the lung in relation to the blood and the brain?
The Lung PP equals the Blood PP which equals the Brain PP
Does a highly blood soluble drug get eliminated faster or slower?
Faster
ex: Nitrous Oxide
Define Vapor pressure:
At equilibrium, the pressure exerted by the molecular collisions of the gas against the container walls.
Is vapor pressure directly or inversely proportional to temperature?
It is directly proportional to temperature.
For any mixture of gases in a closed container, each gas exerts a pressure proportional to its fractional mass. This is called its {blank}?
Partial pressure
What is Dalton’s Law?
The sum of the partial pressures of each gas in a mixture of a gases equals the total pressure of the entire mixture
What is Henry’s Law?
The relationship of concentration of a gas with which the solution is in equilibrium
Which Law applies to the movement to equilibrium?
Henry’s Law
Which law applies to the PP of gases?
Dalton’s law
Ptotal=Pgas1+Pgas2+Pgas3 is a representation of what?
Dalton’s Theory of partial pressures.
What is the solubility coefficient?
For any gas in equilibrium with a liquid, a certain volume of that gas dissolves in a given volume of liquid.
What is MAC of Nitrous Oxide?
104%
What is MAC of sevoflurane?
2.2%
What is MAC of desflurane?
6.0%
What is MAC of isoflurane?
1.15%
The concentration of each gas in a mixture of gases in solution depends on two things: what are they?
- Its partial pressure in the gas phase in equilibrium with the solution.
- Its solubility within that solution
What is the most direct measurement of the Brain’s amount of an inhaled anesthetic?
End Tidal Percentage of the gas.
Do inhaled anesthetics equilibrate based on their concentration or their partial pressures in each tissue?
Partial pressures
Which inhaled anesthetic can be used for very large patients because it does not get “stuck” in the fat reservoirs?
Desflurane
Distribution of cardiac output to different tissues:
Vessel-rich group, muscle, fat?
Vessel-rich group 10% body mass and 75% CO.
Muscle is 50% body mass and 19% CO. Fat is 20% body mass and 6% CO
Fractional volume definition:
In the gas phase, fractional concentration (% by volume) is equal to the partial pressure divided by ambient pressure.
