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26 Cards in this Set

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What activity does an LA have when its base component is charged?
Channel blocking activity
(Note: this is done WITHIN the channel)
What activity does an LA have when its base component is uncharged?
Diffusion activity
Where are ester derived LAs metabolized?
In plasma
Where are amide derived LAs metabolized?
In the liver
What is the mechanism of LAs?
Block fast Na channels
How does acidosis affect LAs?
Reduces the efficacy of LAs
Reduced the amount that can diffuse into cells
What can cause local acidosis that would compromise LA function?
Infection

Repeated injection of LAs
(LAs are HCl salts, use up buffering capacity)
How are axons preferentially targeted by LAs?
Distal areas anesthetized later and recover earlier

Rapidly firing > slowly firing
Myelinated > unmyelinated
Smaller > Larger

SO, pain fibers are blocked first
Why are LAs often mixed with Epi or phenylephrine?
To provide local vasoconstriction
Delays the diffusion of the LA
How do LAs affect the CV system?
Class I anti-arrhythmic effects
(Note: may be exacerbated by presence of Epi)

Vasodilation --> hypotension

Sympathetic block is a concern w/ spinal anesthesia
How do low doses of LAs affect the CNS?
Sedation
How do high doses of LAs affect the CNS?
Convulsions
Which type of LA more commonly causes hypersensitivity?

Ester or Amide
Ester
Which LAs are suitable for injection (5)?
Procaine
Tetracaine

Lidocaine
Mepivacaine
Bupivacaine

Essentially, all BUT benzocaine
Which LA is used in ophthalmology?
Tetracaine
Which LA has low solubility in water and is used only topically?
Benzocaine
Which LAs are ester-derived?
Procaine
Tetracaine
Benzocaine
Which LAs are amide derived?
Lidocaine
Mepivacaine
Bupivacaine
Onset and duration of Procaine
Slow onset
Short duration
How dose tetracaine compare to procaine?
10x more potent

Slower onset
Longer duration
How does lidocaine compare to procaine?
2-3x more potent

More rapid onset
MEDIUM duration
Which LA is effective without a vasoconstrictor?
Mepivacaine
Which LA is useful in elderly pts. w/ CV disease?
Mepivacaine
(beneficial that it doesn't need a vasoconstrictor)
Which has a longer duration of action?

Lidocaine of Mepivicaine
Mepivicaine
(Note: it is only a little longer (20%), still qualifies as medium)
Which LA is useful in continuous epidrual anesthesia?
Bupivacaine
How does bupivicaine compare to procaine?
10x more potent (like tetracaine)

Long DOA