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Anesthesiology > Local Anesthetic Agents > Flashcards

Local Anesthetic Agents Flashcards

1
Q

The reversible block of the generation and propagation of the action potential in neural tissue is known as what?

A

Local anesthetic

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2
Q

Transient loss of what 3 functions can be seen with local anesthetics?

A
  • Sensory
  • Motor
  • Autonomic
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3
Q

Local anesthetics target what?

A

Axons of A and C fibers (sensory nerves)

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4
Q

Which are more prone to hydrolysis, amide or ester links?

A

Ester

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5
Q

Which have a shorter duration of action, anesthetics with amide or ester links?

A

Ester

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6
Q

What are 4 examples of local anesthetics with esters?

A
  • Cocaine
  • Procaine
  • Tetracaine
  • Benzocaine
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7
Q

What are 6 examples of local anesthetics with amides?

A
  • Lidocaine
  • Prilocaine
  • Mepivacaine
  • Bupivacaine
  • Ropivacaine
  • Levo-bupivacaine
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8
Q

Where do local anesthetics act?

A

Site of injection.

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9
Q

Slow absorption into systemic circulation is usually desired with what?

A

Local anesthetics

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10
Q

What are 3 factors increasing systemic absorption?

A
  • High dosage
  • Increased blood flow at site of injection
  • Vasodilation
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11
Q

Which remains at the receptor site longer, the cationic or non-charged form?

A

Cationic

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12
Q

Which is able to rapidly penetrate membranes, the cationic or non-charged form?

A

Non-charged

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13
Q

What effect does pka have on onset?

A
  • High pka has slow onset.

- Low pka has fast onset

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14
Q

Which has a faster onset, procaine or lidocaine?

A

Lidocaine

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15
Q

Which has a faster onset, lidocaine or mepivacaine?

A

Mepivacaine

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16
Q

Which local anesthetic has the slowest onset?

A

Procaine

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17
Q

Which has a faster onset, mepivacaine or bupivacaine?

A

Mepivacaine

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18
Q

An infection can have what effect on the internal environment?

A

Make it acidic.

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19
Q

Increased protein binding has what effect on duration of action?

A

Increased duration

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20
Q

Which has a higher percentage of protein binding, procaine or lidocaine?

A

Lidocaine

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21
Q

Which has a higher percentage of protein binding, lidocaine or mepivacaine?

A

Mepivacaine

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22
Q

Which has a higher percentage of protein binding, mepivacaine or bupivacaine?

A

Bupivacaine

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23
Q

How is lipid solubility related to potency?

A

Positively

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24
Q

What effect does lipid solubility have on onset and duration?

A

Slower onset and longer duration

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25
Q

How does perfusion affect systemic absorption?

A

Highly perfused area leads to faster systemic absorption.

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26
Q

What are 2 examples of highly perfused areas?

A
  • Mucus membranes

- Intercostal muscles

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27
Q

What are 3 examples of poorly perfused areas?

A
  • Tendons
  • Dermis
  • Fat
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28
Q

What are 2 examples of vasoconstrictors?

A
  • Epinephrine

- Phenylephrine

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29
Q

What can lead to reduced blood perfusion?

By how much?

A
  • Vasoconstrictors

- 30%

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30
Q

T/F: Vasoconstrictors enhance the concentration of available drug in the premises of neuronal tissue.

A

True

31
Q

What effect do vasoconstrictors have on duration of action?

A

Increase it.

32
Q

What effect do vasoconstrictors have on analgesia?

A

Prolonged analgesic effects.

33
Q

What are 2 advantages of epinephrine?

A
  • Reduces systemic absorption of local anesthetics

- Reduces risks of systemic toxicity induced by local anesthetics

34
Q

What is a disadvantage of epinephrine?

A

Potential for life-threatening arrhythmias

35
Q

Where are amides metabolized?

Excreted?

A
  • In the liver by cytocrome P450

- Kidneys

36
Q

Where might amides accumulate?

A

Liver

37
Q

Where are esters metabolized?

Excreted?

A
  • In plasma by pseudocholinesterase

- Kidneys

38
Q

What effect do local anesthetics have on nerve conduction?

A

Prevent sodium channels opening in neuronal axons, thus maintaining fully polarized state and blocking nerve propagation.

39
Q

Action potentials are conducted along what part of the axon?

A

Ranvier nodes

40
Q

Where do local anesthetics act on the axon?

A

Ranvier nodes

41
Q

How many nodes of Ranvier need to be blocked in order for a local anesthetic to be effective?

A

2-3 nodes of Ranvier

42
Q

T/F: Local anesthetics are only capable of blocking sensory nerves.

A

False - They are capable of blocking all nerves, not only sensory nerves.

43
Q

Local anesthetics may cause what due to the blockade of motor neurons?

A

Muscle paralysis

44
Q

Local anesthetics may cause what 2 things due to the blockade of autonomic nerves?

A
  • Vasodilation

- Hypotension

45
Q

Which type of fibers are more susceptible to local anesthesia?

A

Smaller non-myelinized fibers

46
Q

Which type of fibers are less susceptible to local anesthesia?

A

Larger myelinized fibers

47
Q

Is a blockade by local anesthetics more or less marked at higher frequencies of depolarization?

A

More marked

48
Q

What type of nerves have a higher firing rate?

Why?

A
  • Sensory nerves

- More susceptible

49
Q

What effects does firing rate have on susceptibility?

A
  • Higher firing rate means more susceptible

- Slower firing rate means less susceptible

50
Q

Which have a higher firing rate, small or large diameter fibers?

A

Small diameter

51
Q

Which fibers get blocked earlier or with low concentrations of local anesthetics?

A

Small diameter sensory nerves

52
Q

Some local anesthetics can be used as what?

What are 2 examples of these?

A
  • Antiarrhythmic agents

- Lidocaine and procaine

53
Q

Some local anesthetics can cause what at high doses?

what are 2 examples of these?

A
  • Lethal arrhythmias

- Bupivacaine and ropivacaine

54
Q

What are 3 effects local anesthetics can have on cardiac cells?

A
  • Suppress re-entrant ventricular arrhythmia
  • Increase ventricular fibrillation threshold
  • Decrease automaticity
55
Q

What is the progression of toxicity for local anesthetics seen in the CNS?

A

First sedation, followed by tonic-clonic seizures, coma

56
Q

What effect do local anesthetics have on the respiratory system?

A

Depression

57
Q

What are 3 effects local anesthetics have on the CV system?

A
  • Bradycardia
  • Arrhythmias
  • Hypotension
58
Q

What are 4 possible toxic effects that can be seen with local anesthetics?

A
  • Tissue irritation
  • Allergic reactions
  • Methemoglobinemia
  • Apoptosis
59
Q

In which species can methemoglobinemia be more of a problem with local anesthetics?

A

Cats

60
Q

What is the order of presentation for most amide type of local anesthetic toxicity?

A
  • CNS signs
  • Respiratory system depression
  • Cardiovascular system depression
61
Q

Which drug is the exception to the normal order of presentation of local anesthetic toxicity?
What is the difference?

A
  • Bupivacaine

- Causes cardiovascular depression first

62
Q

What are 2 examples of isomers of bupivacaine that have less cardiac toxicity?

A
  • Ropivacaine

- Levo-bupivacaine

63
Q

A toxic dose of local anesthetic can cause side effects when injected how?

A

Rapidly IV

64
Q

What is considered to be a toxic dose of lidocaine?

A

8 mg/kg

65
Q

Do not inject more than what dose of lidocaine in a dog?

A cat?

A
  • 4 mg/kg

- 2 mg/kg

66
Q

What is considered to be a toxic dose of bupivacaine?

A

4 mg/kg

67
Q

Do not inject more than what dose of bupivacaine in a dog?

A cat?

A
  • 2 mg/kg

- 1 mg/kg

68
Q

T/F: Dogs are more sensitive to local anesthetics than cats.

A

False - Cats more more sensitive than dogs.

69
Q

Always do what before injecting a local anesthetic?

A

Aspirate to check for accidental IV needle placement. Look for blood.

70
Q

Allergic reactions are mainly seen with what type of local anesthetic?

A

Ester-type

71
Q

What is a possible sign of methemoglobinemia?

A

Pulseox will be about 85% due to significant hypoxia

72
Q

Cats are more prone to develop methemoglobinemia with which 2 local anesthetics?

A
  • Prilocaine

- Benzocaine

73
Q

What are 3 forms of supportive care that can be used for local anesthetic toxicity?

A
  • CV and/or respiratory support
  • Steroid for allergies
  • Anti-epileptic drugs
74
Q

What is one possible specific treatment for local anesthetic toxicity?

A

Lipid emulsion

Anesthesiology (19 decks)

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