Inhalation Anesthesia Part 1 - Quiz 4 Flashcards
What is the chemical structure of all commonly used Inhalation Agents?
Ethers or Aliphatic Hydrocarbons w/ no more than 4 Carbon atoms.
Why is the size of the Inhalation Agent molecules significant?
If too big, it loses its Lipid Solubility
Length is < 1.5x the diameter
What are the Physical Properties of Modern Inhaled Anesthetics?
Halogenated Hydrocarbons
Except: Nitrous Oxide
Which Gas is this?
Halothane
What gas is this?
Isoflurane
What Gas is this?
Desflurane
What Gas is this?
Sevoflurane
What characteristics are effected with halogenation of organic compounds?
(adding {F], [Cl], [Br], or [I])
Potency
Flammability
Chemical Stability
Arrhythmogenic Properties
What happens as you add more fluorine atoms to an anesthetic molecule?
Slowing of Biodegradation
What are the only “true gases” of inhaled anesthetics?
N2O & O2
The rest are Vapors of Volatile Liquids
What chemical properties & Physical properties make anesthetic gases lipid soluble?
Non-Ionized & Low Molecular Weight
What is the Goal of Inhaled Anesthesia and how how is that goal accomplished?
Produce anesthetic state by establishing partial pressure of an agent in lungs that then equalizes w/ the brain & spinal cord.
What is the “MAC” value in regards to inhaled anesthetics?
MAC = Minimal Alveolar Concentration
It is the minimal concentration of vapor in the alveoli needed to prevent movement in 50% of patients in response to surgical stimulation.
What is the definition of General Anesthesia?
A drug’s capacity to induce & sustain a state of
Unconsciousness
Amnesia
Analgesia
Immobility
What is a property that Anesthetic gases do not have?
Pain Properties
What is the Meyer-Overton Rule?
Lipid Solubility is directly proportional to Potency
How can an Anesthetic Gas be reversed?
Reversal achieved with Application of Pressure
How would a Reduction of Body Temperature affect anesthetic requirement?
↓Body Temp = ↓Anesthetic Requirement
How is MAC% related to Potency & Lipid Solubility?
MAC% is inversely related to Potency & Lipid Solubility
The more Potent the agent, the less MAC
What is the MAC% of N2O?
104
How are Inhaled Anesthetics thought to work?
Enhances Inhibitory Ion Channels & Block Function of Excitatory Ion Channels
What happens when Inhibitory Channels are Enhanced?
Hyperpolarization via Chloride Influx via GABA or Glycine receptors
or
or Potassium Efflux
How is Immobility achieved with Anesthetic Gases?
Activates Descending Noradrenergic Pathways from brainstem and Blocks Input in Dorsal Horn
Immobility is measurable by MAC
In an anesthetic molecule, if the carbon chain exceeds 4-5 carbons, what happens?
Loss of Immobility
What are the structural targets that are involved in the Amnestic effects fo anesthesia?
Amygdala
Hippocampus
Cortex
In terms of delivery, What are the factors that determine Inspired Gas Concentration?
Fresh Gas Flow Rate
Circuit Volume
Circuit Absorption
What factors determine Alveolar Gas Concentration?
- Uptake
- Ventilation
- Concentration Effect
- Second Gas Effect
- Augmented Inflow effect
When is Equilibrium of Anesthetic Gas achieved?
When partial pressures are equal in the alveoli, blood, and CNS
Palveoli = Pblood = PCNS
What are the factors that contribute to Anesthetic Gas Equilibrium?
- Inhaled Gas moves quickly to and from lung, blood, & CNS
- Plasma and tissue dont absorb the gas
- Minimal Gas metabolism, excretion, and redistribution
In a container, how is vapor pressure related to the volume of the Liquid?
As long as there is liquid in the container, Vapor Pressure is independent of the volume of the liquid
What is Henry’s Law?
Relationship of Concentration of a Gas in a solution to the Partial Pressure of the Gas
In Anesthesia, gases equilibrate based on what?
Partial Pressures, not Concentration
How is the rate of Gas Uptake related to Blood Solubility?
Speed of Uptake & Elimination from brain is inversely related to Blood Solubility
What is a Aliphatic Compound?
Hydrocarbon Compound containing carbon & hydrogen in straight chains, branched or non-aromatic rings
The _____ blood-soluble the gas, the _____ the onset of action of the gas
The Less blood-soluble the gas, the faster the onset of action
Vice Versa
List in order the rate of onset from fastest to slowest for N2O, Des, Sevo, Isoflurane, Enflurane
Desflurane > N2O > Sevo > Isoflurane > Enflurane
What is the MAC% for Desflurane?
6%
What is the MAC% for Sevoflurane?
2%
What is the MAC% for Isoflurane?
1.4%
What is the λoil:gas for N2O?
1.4
What is the λoil:gas for Desflurane?
19
What is the λoil:gas for Sevoflurane?
51
What is the λoil:gas for Isoflurane?
98
What is the λblood:gas for N2O?
0.47
What is the λblood:gas for Desflurane?
0.45
Wht is the λblood:gas for Sevoflurane?
0.65
What is the λblood:gas for Isoflurane?
1.4
