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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
LAST at risk
Neonates and infants (increase free fraction) Elderly Pregnancy - women in labor
26
cardiovascular depression
>25mcg/ml
27
What does peak serum concentration correlates with?
- LA concentration - region administrated - protein binding
28
How fast does esters metabolism occurs?
Within minutes
29
Major CV toxicity requires how much local anesthetic blood concentration
3x the required to produce seizures
30
Lipid solubility distribution
More slowly
31
Who is most at risk for methemiglobinemia?
Neonate
32
What other channel blockade may contribute?
Potassium channel
33
Are phasic blocks stronger or weaker in sensory than motor nerves?
Stronger
34
If more lipid soluble, what will happen with duration of action?
More slowly diffuse from a lipid rich environment to aqueous blood stream
35
Treatment of LAST
Lipid emulsion | -early administration of 20% IV lipid emulsion
36
Onset and action with mixing LA
Fast onset and long acting (lidocaine and bupivacaine)
37
What kind of pKa and pH will have the greater amount of non-ionized (neutral) form that more readily permeates the nerve cell membrane?
pKa closest to physiologic pH (7.4)
38
When is the greatest effect of LA?
When most of nerve fibers are firing
39
What kind of distribution do you get from injection at target/local site
Distribution within that compartment
40
CC/CNS low ratio
More cardiotoxic (bupivacaine)
41
Which LA agent is the only exception to pKa closest to physiologic pH will have fast onset?
Chloroprocaine
42
Structure activity relationship of lipophilic region-aromatic region
Onset Potency Duration of action
43
What is the minimum of nodes that must be blocked to prevent AP propagation?
3
44
LA esters drugs name?
All names have 1 i
45
2 general intent of local anesthetics
1. Produce local or regional effect | 2. Avoid systemic effects
46
What is methemiglobinemia?
- reduced O2 carrying capacity - reduced Fe2+ combines with O2 - oxidized to Fe3+ state
47
What 4 factors effect pharmacokinetic?
1. Molecule size 2. % ionionized 3. Lipid solubility 4. Serum/tissue protein binding
48
Do sensory or motor nerves fire at increased rates?
Sensory nerves
49
What 2 structures affect activity relationship?
Amino-ester Amino-aside -linkage aromatic ring to the hydrocarbon chain
50
Nerves with higher baseline firing rates will demonstrate greater blockade vs nerves with lowering firing rates
Phasic block
51
What kind of pH do LA’s have?
Weak bases and high pKa
52
Is some degree of lipid solubility needed for cross membrane to site of action?
Yes to some degree
53
What is used to treat methemiglobinemia?
Methylene blue
54
Extreme lipophilicity favors what kind of binding and duration of action?
- continued binding | - increases duration of action
55
Treatment of LA toxicity for seizures?
Benzodiazepines
56
Are smaller or larger axon diameter more sensitive to LA action?
Smaller
57
PK absorption with intact skin
Requires high concentration of lipid soluble agent for permeation and analgesia
58
What is the exception to esters metabolism?
Cocaine metabolized by liver
59
Potency of LA action (3):
1. Correlates with lipid solubility 2. Increased by adding large alkyl groups 3. No single measure to compare potency
60
Coma, respiratory arrest
15-25mcg/ml
61
Structure activity relationship of hydrophilic amine group
3 or 4 amine depending on PKA &pH
62
What kind of charge can pass through membrane
Neutral (nonionized) LA
63
CC/CNS high ratio
Greater safety margin bc recognizes earlier presenting CNS before CV collapse ensures (lidocaine, mepivacaine)
64
Structure activity relationship of ester or amide linkage
Hydrolysis - duration of action
65
Local anesthetic systemic toxicity (LAST)
1/3 begin with CNS and progress to CVS | -occurs immediately following LA injection
66
LA amides drug name?
All names have 2 i’s
67
Onset of LA action depends on (6):
1. Lipid solubility 2. Ease of diffusion through connective tissue 3. Charged form 4. Epi added 5. pH of tissue 6. pKa
68
Duration of action for LA
- correlates with potency and lipid solubility - rate of dissociation from Na channel - correlated with tissue protein binding
69
Distribution from systemic distribution?
2 compartment - initial phase (organs of high blood flow) - brain and heart, liver, kidneys - delayed absorption from adipose phases
70
What kind of PK distribution correlate with toxicity risk?
Cmax and time to Cmax
71
Onset and duration of transient neurological symptoms after spinal anesthesia
Onset 6-36hrs | Lasts 1-7days
72
Highest to lower peak concentrations with vascularity?
IV>tracheal>intercostal>caudal>Paracervical>epidural>brachial plexus>subarachnoid/femoral>subcutaneous
73
Conduction of nerve impulse through non-myelinated nerve fiber requires what?
More LA exposure for similar block in myelinated axon
74
What is the minimum concentration that will block nerve impulses conduction impacted by?
- fiber size, type, myelination - pH - frequency of nerve stimulation - electrolyte concentration (less K+ and more Ca+)
75
When is distribution the greatest?
Both lipid solubility and protein binding are high
76
MOA of local anesthetics
Inhibit VG Na+ channels
77
Do you use max dose when you combine LA?
No because toxicity is additive
78
Seizures, unconsciousness
10-15mcg/ml

Pharmacology (14 decks)

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