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Basics Principles of Anesthesia > Local Anesthetic Pharmacology > Flashcards

Local Anesthetic Pharmacology Flashcards

1
Q

How have local anesthetics improved over the years?

A

Become less toxic and faster working

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2
Q

What is a primary determinant of intrinsic potentcy and duration of LAs?

A

lipid solubilty

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3
Q

Do LAs have a greater affinity to lipid membranes?

A

yes

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4
Q

Why is it advantageous for LAs to have a greater affinity to lipid membranes?

A

They have a greater proximity to their sites of action

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5
Q

The ______ the LA remains in membrane vicinity the _____ likely it will be to effect its action on the ______ channel

A

The LONGER the LA remains in membrane vicinity the MORE likely it will be to effect its action on the NA+ channel

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6
Q

What does a greater lipid solubility and duration of action on site do to LA toxicity? Increases or decreases it?

A

INCREASES toxicity

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7
Q

What are 2 examples of low lipid solubility LAs?

A

Procaine
Chloroprocaine

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8
Q

What are 3 examples of intermediate lipid solubility LAs?

A

Lidocaine
Mepivcacaine
Prilocaine

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9
Q

What are 3 examples of high lipid solubility LAs?

A

Bupivacaine
Ropivacaine
Tetracaine

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10
Q

______ is related to the the extent to which the LA remains in the vicinity of the nerve

A

DURATION

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11
Q

How does the administration of vasoconstrictors prolong the effect of LAs?

A

the vasoconstriction prevents vascular uptake

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11
Q

What 3 factors determine how long an LA remains in the vicinity of the nerve?

A
  • Lipid solubiilty
  • The degree of vascularity of the tissue
  • The presence of vasoconstrictors
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12
Q

What is the structural classification of cocaine and chlorprocaine?

A

Ester

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13
Q

Is the onset of cocaine and chlorprocaine, lidocaine, mepivacaine: slow, moderate or fast?

A

Fast

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14
Q

What is the structural classification of lidocaine, mepivacaine, bupivacaine, & ropivacaine?

A

Amide

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15
Q

Is the onset of bupivacaine, & ropivacaine: slow, moderate or fast?

A

Moderate

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16
Q

Which LA is the longest acting?

A

Bupivocaine

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17
Q

Which LA is the shortest acting?

A

chloroprocaine

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18
Q

Compare the 1/2 life: Ropiv vs Bupiv

A

Bupiv 1/2 life > Ropiv 1/2 life

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19
Q

Are LAs weak acids or weak bases?

A

weak bases

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20
Q

What is pKa?

A

the pH at which the ionized and non-ionized forms are present in equal amounts

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21
Q

Once equilibrium is reached between the base and the charged forms, which form binds to the LA binding site?

A

charged, ionized

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22
Q

The ______ cation is responsible for the neural blockade

A

IONIZED

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23
Q

What 2 factors influence time of onset?

A

pKa
diffusibility

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24
Q

What 2 factors affects the LAs ability to cross the cell membrane?

A

molecular weight
liposolubility of the molecule

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25
Q

Do LAs have approximately the same molecular weight?

A

Yes

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26
Q

The diffusibility of LAs molecules from the injection site depends on its _______ since LAs have approximately the same weight

A

HYDROPHLICITY

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27
Q

Which LA form is more lipid soluble, ionized or nonionized?

A

nonionized

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28
Q

Which LA form can cross the cell membrane more readily, ionized or nonionized?

A

nonionized

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29
Q

What factor affects the speed of onset?

A

drug pKa

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30
Q

The pKa affects how rapidly the drug ______

A

IONIZES

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31
Q

The concentration of ______ drug available for diffusion across the cell membrane determines blockade

A

FREE

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32
Q

In acidic solutions, molecules of weak bases are in their ionized or unionized state? How does this change in basic solutions?

A

ionized
unionized

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33
Q

In acidic solutions, molecules of weak acids are in their ionized or unionized state? How does this change in basic solutions?

A

unionized
ionized

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34
Q

Ester LAs are hydrolyzed by _____ - an enzyme?

A

PLASMA CHOLINESTERASE

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35
Q

Do esters have a shorter or longer elimination half life?

A

shorter

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36
Q

Are true allergies to LAs commons or rare?

A

Rare

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37
Q

Are allergies more common with ester LAs or amide LAs?

A

Esters

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38
Q

What causes the allergic reaction to ester LAs?

A

their metabolism to PABA

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39
Q

What does PABA stand for?

A

Para aminobenzoic Acid

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40
Q

Can allergic reactions to PABA cause urticaria? Anaphylaxis?

A

Yes

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41
Q

How is PABA formed?

A

during the metabolism of methlyparaben preservative

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42
Q

Order these ester LA metabolism rates from rapid, intermediate, slow: Chloroprocaine, Tetracaine, Procaine?

A

Chloroprocaine (rapid) > Procaine (Intermediate) > Tetracaine (slow)

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43
Q

The varying amide LA metabolism rates is due to which types of enzymes?

A

microsomal

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44
Q

Compared to ester LAs, do amide LAs have a faster or slower metabolism rate?

A

slower

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45
Q

Do amide LAs showcase sustained plasma concetrations?

A

Yes

46
Q

Which is more likley to cause systemic toxicity, ester or amide LAs? Why?

A

Amide LAs because their cumulative effect is greater than that of esters

47
Q

Order these amide LA metabolism rates from rapid, intermediate, slow: Lidocaine & Mepivacaine, Prilocaine, Bupivacaine

A

Prilocaine (rapid) > Lidocaine & Mepivacaine (intermediate), Bupivacaine (rapid)

48
Q

What 3 factors does LA dosing depend on?

A
  • Injection technique
  • place of injection
  • addition of additives
49
Q

What is max dosing WITHOUT epi in mg of chloroprocaine - for all block sites?

A

800 mg

50
Q

What is max dosing WITH epi in mg of chloroprocaine - for all block sites?

A

1000 mg

51
Q

What is max dosing WITHOUT epi in mg of lidocaine - for all block sites?

A

300 mg

52
Q

What is max dosing WITH epi in mg of lidocaine - for all block sites?

A

500 mg

53
Q

What is max dosing WITHOUT epi in mg of prilocaine - for all block sites?

A

600 mg

54
Q

Do you use prilocaine WITH epi?

A

No

55
Q

What is max dosing WITHOUT epi in mg of mepivacaine - for all block sites?

A

400 mg

56
Q

What is max dosing WITH epi in mg of mepivacaine - for all block sites?

A

500 mg

57
Q

What is max dosing WITHOUT epi in mg of bupivacaine - for subq and peripheral block sites?

A

175 mg

58
Q

What is max dosing WITHOUT epi in mg of bupivacaine - for epidural block sites?

A

170 mg

59
Q

What is max dosing WITH epi in mg of bupivacaine - for all block sites?

A

225 mg

60
Q

What is max dosing WITHOUT epi in mg of ropivacaine - for subq and epidural block sites?

A

200 mg

61
Q

What is max dosing WITHOUT epi in mg of ropivacaine - for peripheral block sites?

A

250 mg

62
Q

Do you use ropivacaine WITH epi?

A

No

63
Q

Majority of LA block site onset is fast, which 2 LAs have moderate epidural onset times?

A

Bupivacaine
Ropivacaine

64
Q

If a patient has low plasma pseudocholinesterase, what can this do to the concentration & effect of chloroprocaine? What could this result in?

A
  • increase the concentration of the LA > prolonged effect
  • increased risk for LAST
65
Q

Does chloropracaine have a quick onset?

A

Yes

66
Q

Is chloropracaine least toxic in epidural?

A

Yes

67
Q

Does chloropracaine have metabolites? Does this impair subsequent dosing of epidural?

A

Yes

68
Q

What are the 2 active compounds lidocaine metabolizes to?

A

MEGX & GX

69
Q

Does lidocaine go through hepatic metabolism?

A

Yes

70
Q

Does lidocaine have tachyphylaxis - reduced effects at higher doses?

A

Yes

71
Q

Does adding epinephrine to LA doses prolong duration? What does it cause?

A

Yes, causes vasoconstriction which inhibits the vasodilation effect - keeps the medication at site of injection longer

72
Q

What condition is seen with subarachnoid injection of lidocaine?

A

Transient Neurological Symptoms (TNS)

73
Q

What is the post injection onset time of TNS?

A

4-12 hrs

74
Q

Which LA has a high lipid solubility?

A

Bupivacaine

75
Q

Is bupivacaine an excellent sensory blockers? Why?

A

Yes, because it has high lipid solubility

76
Q

Does bupivacaine have high or low frequency of tachyphylaxis?

A

Low

77
Q

Which dose of bupivacaine has irreversible cardiotoxic effects if injected intravascularly? Is it still on the market?

A

0.75%, no

78
Q

Match the enantiomer to ropivacaine or bupivacaine: S-enantiomer & R enantiomer?

A
  • Ropivacaine = S-enantiomer
  • Bupivacaine = R-enantiomer
79
Q

Is ropivacaine less or more cardiotoxic than bupivacaine? Why?

A

Less because it has an S-enantiomer

80
Q

Does ropivacaine have less or more motor blockade than bupivacaine? What percent?

A

Less, 20%

81
Q

Does ropivacaine result in progressive motor blockade?

A

No

82
Q

What are the 2 reasons for adding epi to LA solution?

A
  • cause vasoconstriction at the site which prolongs drug concentration
  • marker for IV injeciton
83
Q

Will the block persist after the A1 adrenergic agonist effect on bloodflow dissapates?

A

Yes

84
Q

Does epinephrine and other A1 adrenergic agonist increase the intraneural concentration of LAs?

A

Yes

85
Q

What is the most common dose of epinephrine for an epidural?

A

1:200,000

86
Q

What is the most common mg dose of epinephrine for a spinal?

A

0.2 mg

87
Q

Does epi prolong lidocaine and tetracaine?

A

Yes

88
Q

Does epi prolong lipid soluble agents like bupivacine?

A

No

89
Q

If 1:200,000 epi is given IV accidentally, can the HR increase? How many beats? What about the BP? By what percent of BBs?

A

Yes
- HR can increase 30 beats
- BP can increase 10-20% on BBs

90
Q

Should you mix epi in an LA solution for a digital block ( finger, wrist, ankle, etc)?

A

NO, will cause problematic vasoconstriction

91
Q

Can bicarb increase the pH closer to the pKa of the LA?

A

Yes

92
Q

Does bicarb affect the speed of onset of ropivacaine?

A

No

93
Q

What % bicarb is typically added to 10 ml LA solutions? How many mEq/ml is that?

A
  • 8.4%
  • 1 mEq/ml
94
Q

What class is clonidine?

A

A2 adrenergic agonist

95
Q

Clonidine has central _____brain stem & _____ action

A

Clonidine has central BRAIN STERM & PERIPHERAL action

96
Q

Does clonidine enhance intrathecal and epidural labor analgesia?

A

Yes

97
Q

Is analgesic effect more potent when clonidine is administered neuraxially with certain LAs? Does it prolong spinal anesthesia?

A

Yes

98
Q

Individuals on this medication often have clonidine added to their LA?

A

Those on Subutex

99
Q

What are the 2 most common intrathecal (spinal) opioids?

A

Fentanyl
Morphine

100
Q

Are fentanyl and sufentanil highly lipid soluble? What is their onset?

A

Yes, 5-10 mins

101
Q

Is morphine highly lipid soluble? What is spinal its onset?

A

No, it is hydrophobic. 30-60 min

102
Q

Is hydropmorphone highly lipid soluble? What is spinal its onset?

A

No, it is hydrophobic. 30-60 min

103
Q

What are the 3 most common epidural opioids?

A

Fentanyl
Morphine
Sufentanil

104
Q

Do the 3 most common epidural opioids have early systemic uptake?

A

Yes

105
Q

What is the dermatomal spread for fentanyl and sufentanil - how many?

A

5-6

106
Q

What is the the epidural onset of fentanyl and sufentanil?

A

5-10 min

107
Q

What is the the epidural onset of morphine?

A

1-1.5 hrs

108
Q

Does morphine have an early or late rostral flow?

A

Late

109
Q

What is rostral flow?

A

How the anesthetic moves upward in the spinal column toward the head after being injected into the epidural or subarachnoid (intrathecal) space

110
Q

Does adding dexamethasone to LA nerve blocks prolong duration of analgesia?

A

Yes

111
Q

Is dexamethasone a potent, synthetic corticosteroid? Is it more or less potent than prednisone?

A

Yes, it is 7x more potent than prednisone

112
Q

Is dexamethasone FDA approved fro perineural administration?

A

No

Basics Principles of Anesthesia (6 decks)

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