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26 Cards in this Set
- Front
- Back
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What activity does an LA have when its base component is charged?
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Channel blocking activity
(Note: this is done WITHIN the channel) |
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What activity does an LA have when its base component is uncharged?
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Diffusion activity
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Where are ester derived LAs metabolized?
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In plasma
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Where are amide derived LAs metabolized?
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In the liver
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What is the mechanism of LAs?
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Block fast Na channels
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How does acidosis affect LAs?
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Reduces the efficacy of LAs
Reduced the amount that can diffuse into cells |
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What can cause local acidosis that would compromise LA function?
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Infection
Repeated injection of LAs (LAs are HCl salts, use up buffering capacity) |
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How are axons preferentially targeted by LAs?
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Distal areas anesthetized later and recover earlier
Rapidly firing > slowly firing Myelinated > unmyelinated Smaller > Larger SO, pain fibers are blocked first |
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Why are LAs often mixed with Epi or phenylephrine?
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To provide local vasoconstriction
Delays the diffusion of the LA |
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How do LAs affect the CV system?
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Class I anti-arrhythmic effects
(Note: may be exacerbated by presence of Epi) Vasodilation --> hypotension Sympathetic block is a concern w/ spinal anesthesia |
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How do low doses of LAs affect the CNS?
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Sedation
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How do high doses of LAs affect the CNS?
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Convulsions
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Which type of LA more commonly causes hypersensitivity?
Ester or Amide |
Ester
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Which LAs are suitable for injection (5)?
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Procaine
Tetracaine Lidocaine Mepivacaine Bupivacaine Essentially, all BUT benzocaine |
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Which LA is used in ophthalmology?
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Tetracaine
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Which LA has low solubility in water and is used only topically?
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Benzocaine
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Which LAs are ester-derived?
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Procaine
Tetracaine Benzocaine |
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Which LAs are amide derived?
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Lidocaine
Mepivacaine Bupivacaine |
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Onset and duration of Procaine
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Slow onset
Short duration |
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How dose tetracaine compare to procaine?
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10x more potent
Slower onset Longer duration |
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How does lidocaine compare to procaine?
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2-3x more potent
More rapid onset MEDIUM duration |
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Which LA is effective without a vasoconstrictor?
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Mepivacaine
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Which LA is useful in elderly pts. w/ CV disease?
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Mepivacaine
(beneficial that it doesn't need a vasoconstrictor) |
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Which has a longer duration of action?
Lidocaine of Mepivicaine |
Mepivicaine
(Note: it is only a little longer (20%), still qualifies as medium) |
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Which LA is useful in continuous epidrual anesthesia?
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Bupivacaine
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How does bupivicaine compare to procaine?
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10x more potent (like tetracaine)
Long DOA |
