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Pharmacology > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

1
Q

Lightheaded ness, oral parenthesis, tinnitus, muscular twitching

A

5-10mcg/ml

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2
Q

Would you give propofol if signs of CV compromise?

A

No bc propofol drops BP more

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3
Q

High tissue protein binding with distribution

A

Remains in neural tissues longer

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4
Q

What is prilocaine and benzocaine metabolized to?

A

O-toluidine (methemiglobinemia)

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5
Q

What does pKa determine with LA?

A

Partially determines the speed of onset

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6
Q

Respiratory effects of IV infused lidocaine or systemic toxicity

A

Depressed hypoxia drive (response to low PaO2)

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7
Q

Dissociation from binding site impacted by:

A

Molecule size, charge, and lipophilicity

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8
Q

1-5mcg/ml

A

Analgesia

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9
Q

Are myelinated or unmyelinated more sensitive to LA block?

A

Myelinated axon

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10
Q

Does lipid solubility or protein binding have a greater impact to duration of action?

A

Protein binding

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11
Q

When does LA gains access during VG Na+ state?

A

Open/activated state

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12
Q

PK absorption of mucous membranes

A

Provides minimal barriers

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13
Q

What impacts the duration of action for LA?

A

Lipid solubility and protein binding

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14
Q

What does increasing lipophilicity do?

A
  • increasing LA potency
  • slower onset
  • delay absorption into systemic circulation
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15
Q

Vasoconstrictors with epinephrine?

A

Prolonged duration of action and reduced peak serum concentration

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16
Q

What does lipophilicity favor?

A

Entry of LA molecule into the cell membrane

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17
Q

Is less lipid soluble more or less potent?

A

Less potent so faster onset

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18
Q

How are esters metabolized?

A

Hydrolysis by plasma esterases (pseudocholinesterase) into inactive metabolites

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19
Q

How does methylene blue treatment work?

A

Reduces metHb to Hb in 20-60min

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20
Q

What kind of pH does epinephrine containing LA have?

A

Acidic pH

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21
Q

How long are amides metabolized?

A

Longer elimination half-life

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22
Q

What are amides metabolized by?

A

Hepatic CYP 450 enzymes

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23
Q

Do smaller molecules dissociate from Na channels more or less rapidly?

A

More

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24
Q

What increases the risk of accumulation of unmetabolized drug and systemic toxicity?

A

Amide metabolism

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25
Q

LAST at risk

A

Neonates and infants (increase free fraction)
Elderly
Pregnancy - women in labor

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26
Q

cardiovascular depression

A

> 25mcg/ml

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27
Q

What does peak serum concentration correlates with?

A
  • LA concentration
  • region administrated
  • protein binding
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28
Q

How fast does esters metabolism occurs?

A

Within minutes

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29
Q

Major CV toxicity requires how much local anesthetic blood concentration

A

3x the required to produce seizures

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30
Q

Lipid solubility distribution

A

More slowly

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31
Q

Who is most at risk for methemiglobinemia?

A

Neonate

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32
Q

What other channel blockade may contribute?

A

Potassium channel

33
Q

Are phasic blocks stronger or weaker in sensory than motor nerves?

A

Stronger

34
Q

If more lipid soluble, what will happen with duration of action?

A

More slowly diffuse from a lipid rich environment to aqueous blood stream

35
Q

Treatment of LAST

A

Lipid emulsion

-early administration of 20% IV lipid emulsion

36
Q

Onset and action with mixing LA

A

Fast onset and long acting (lidocaine and bupivacaine)

37
Q

What kind of pKa and pH will have the greater amount of non-ionized (neutral) form that more readily permeates the nerve cell membrane?

A

pKa closest to physiologic pH (7.4)

38
Q

When is the greatest effect of LA?

A

When most of nerve fibers are firing

39
Q

What kind of distribution do you get from injection at target/local site

A

Distribution within that compartment

40
Q

CC/CNS low ratio

A

More cardiotoxic (bupivacaine)

41
Q

Which LA agent is the only exception to pKa closest to physiologic pH will have fast onset?

A

Chloroprocaine

42
Q

Structure activity relationship of lipophilic region-aromatic region

A

Onset
Potency
Duration of action

43
Q

What is the minimum of nodes that must be blocked to prevent AP propagation?

A

3

44
Q

LA esters drugs name?

A

All names have 1 i

45
Q

2 general intent of local anesthetics

A
  1. Produce local or regional effect

2. Avoid systemic effects

46
Q

What is methemiglobinemia?

A
  • reduced O2 carrying capacity
  • reduced Fe2+ combines with O2
  • oxidized to Fe3+ state
47
Q

What 4 factors effect pharmacokinetic?

A
  1. Molecule size
  2. % ionionized
  3. Lipid solubility
  4. Serum/tissue protein binding
48
Q

Do sensory or motor nerves fire at increased rates?

A

Sensory nerves

49
Q

What 2 structures affect activity relationship?

A

Amino-ester
Amino-aside
-linkage aromatic ring to the hydrocarbon chain

50
Q

Nerves with higher baseline firing rates will demonstrate greater blockade vs nerves with lowering firing rates

A

Phasic block

51
Q

What kind of pH do LA’s have?

A

Weak bases and high pKa

52
Q

Is some degree of lipid solubility needed for cross membrane to site of action?

A

Yes to some degree

53
Q

What is used to treat methemiglobinemia?

A

Methylene blue

54
Q

Extreme lipophilicity favors what kind of binding and duration of action?

A
  • continued binding

- increases duration of action

55
Q

Treatment of LA toxicity for seizures?

A

Benzodiazepines

56
Q

Are smaller or larger axon diameter more sensitive to LA action?

A

Smaller

57
Q

PK absorption with intact skin

A

Requires high concentration of lipid soluble agent for permeation and analgesia

58
Q

What is the exception to esters metabolism?

A

Cocaine metabolized by liver

59
Q

Potency of LA action (3):

A
  1. Correlates with lipid solubility
  2. Increased by adding large alkyl groups
  3. No single measure to compare potency
60
Q

Coma, respiratory arrest

A

15-25mcg/ml

61
Q

Structure activity relationship of hydrophilic amine group

A

3 or 4 amine depending on PKA &pH

62
Q

What kind of charge can pass through membrane

A

Neutral (nonionized) LA

63
Q

CC/CNS high ratio

A

Greater safety margin bc recognizes earlier presenting CNS before CV collapse ensures (lidocaine, mepivacaine)

64
Q

Structure activity relationship of ester or amide linkage

A

Hydrolysis - duration of action

65
Q

Local anesthetic systemic toxicity (LAST)

A

1/3 begin with CNS and progress to CVS

-occurs immediately following LA injection

66
Q

LA amides drug name?

A

All names have 2 i’s

67
Q

Onset of LA action depends on (6):

A
  1. Lipid solubility
  2. Ease of diffusion through connective tissue
  3. Charged form
  4. Epi added
  5. pH of tissue
  6. pKa
68
Q

Duration of action for LA

A
  • correlates with potency and lipid solubility
  • rate of dissociation from Na channel
  • correlated with tissue protein binding
69
Q

Distribution from systemic distribution?

A

2 compartment

  • initial phase (organs of high blood flow)
  • brain and heart, liver, kidneys
  • delayed absorption from adipose phases
70
Q

What kind of PK distribution correlate with toxicity risk?

A

Cmax and time to Cmax

71
Q

Onset and duration of transient neurological symptoms after spinal anesthesia

A

Onset 6-36hrs

Lasts 1-7days

72
Q

Highest to lower peak concentrations with vascularity?

A

IV>tracheal>intercostal>caudal>Paracervical>epidural>brachial plexus>subarachnoid/femoral>subcutaneous

73
Q

Conduction of nerve impulse through non-myelinated nerve fiber requires what?

A

More LA exposure for similar block in myelinated axon

74
Q

What is the minimum concentration that will block nerve impulses conduction impacted by?

A
  • fiber size, type, myelination
  • pH
  • frequency of nerve stimulation
  • electrolyte concentration (less K+ and more Ca+)
75
Q

When is distribution the greatest?

A

Both lipid solubility and protein binding are high

76
Q

MOA of local anesthetics

A

Inhibit VG Na+ channels

77
Q

Do you use max dose when you combine LA?

A

No because toxicity is additive

78
Q

Seizures, unconsciousness

A

10-15mcg/ml

Pharmacology (14 decks)

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