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Anesthesia Lecture 2 Questions

Terms in this set (20)

Where do local anesthetics exert their pharmacological action?
A) Axoplasm
B) Nerve Membrane
C) Myelin Sheath
Nerve Membrane
- within the sodium channel = tertiary amines
- outer surface of the sodium channel
- at the activation gates
- at the inactivation gates
Local anesthetics have their primary effects during which phase of impulse conduction?
A) Resting Potential
B) Depolarization
C) Repolarization
Depolarization
- this involves the movement of Na into the nerve cell (blocked by LA's)
Uncharged LA molecules are called:
Base
Charged LA molecules are called
Cation
Which form of the anesthetic molecule can diffuse through the membrane?
Base (uncharged)
Which form of the anesthetic molecule can bind to the receptor site in the sodium channel?
Cation (charged)
Why do we care how much base / cation we have?
The ratio of base:cation determines the effectiveness of our anesthetic.
What is the relationship between pKa and the base:cation ratio?
* low pKa --> more base --> faster onset
* high pKA --> less base --> slower onset
"KNOW THIS FOR EXAM"
What can make the extracellular tissue acidic?
Anesthetic with vasoconstrictor (due to sodium bisulfite)
Inflammation / Infection
Note: More acidic = slower onset
A LA causes a burning sensation when injected and has a slower onset time compared to other types of LA's. Does this anesthetic have a vasoconstrictor?
Yes! The burning is due to the acidic pH (which also causes the slower onset time)
What is the greatest barrier to the penetration of LA?
Perineurium
LA potentcy is controlled by what physical property
Lipid solubility (more lipid soluble = effectivity at lower concentrations)
LA duration is controlled by what physical property
protein binding (improved binding = improved duration)
LA vasoactivity controls what two clinical effects? I.E. why are the 2 main reasons vasoconstrictors are used ?
Potency and duration (drug availability - vasoconstrictor used to decrease vasoactivity)
LA onset is controlled by what physical property
pKa (low is fast)
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