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aNeuro Exam 2- Lindsey's > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

1
Q

Local anesthetics are weak _____ and are partially ionized at pH 7.4.

A

bases

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2
Q

What form of the anesthetic binds to the Na+ channel pore?

A

both, but the cationic form has a stronger affinity

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3
Q

How does the local anesthetic reach its binding site?

A

via the intracellular pore entrance

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4
Q

Local anesthetics have a ____ structure, typically consisting of 1. a lipophilic aromatic portion; 2. an intermediate alkyl chain; 3. a hydrophilic amine portion.

A

tripartite

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5
Q

Name the toxin:

  • one of the most potent toxins known
  • found in marine dinoflagellates (red tide)
  • binds to and blocks the extracellular entrance of voltage-gated Na+ channels –> death by paralysis of respiratory muscles
A

saxitoxin (STX)

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6
Q

What is the advantage of nerve block anesthesia?

A

large body regions can be anesthesized

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7
Q

What can local anesthetic toxicity cause?

A
  • convulsions
  • respiratory depression
  • arrhythmias
  • arterial dilation
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8
Q

When can local anesthetics reach their binding sites?

A

when the channel is open BUT they are also able to traverse the plasma membrane in the neutral form

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9
Q

Name 3 topical anesthetics.

A
  1. lidocaine
  2. tetracaine
  3. cocaine
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10
Q

How are amide local anesthetics terminated?

A

in the liver

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11
Q

Which local anesthetics are used in intravenous regional anesthesia/Bier’s Block?

A

lidocaine

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12
Q

Virtually all local anesthetics end in -_____.

A

-caine

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13
Q

Why are amide-linked local anesthetics contraindicated in pts with hepatic insufficiency?

A

the drug is only metabolized by the liver

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14
Q

Why is it important that local anesthetics are in the charged and neutral forms in the body?

A

the neutral forms can enter the cell in spite of a closed Na+ channel but the cationic form binds to the Na+ channel pore with a much higher affinity

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15
Q

Name 3 infiltration anesthetics.

A
  1. lidocaine
  2. procaine
  3. bupivacaine
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16
Q

Local anesthetics have a tripartite structure, typically consisting of 1. ______; 2. an intermediate alkyl chain; 3. a hydrophilic amine portion.

A

a lipophilic aromatic portion

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17
Q

What is a disadvantage of epidural anesthesia?

A

plasma level are high and can lead to toxicity

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18
Q

What opens Na+ channels?

A

membrane depolarization

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19
Q

What determines speed of conduction blockade in local anesthetics? Why?

A

pKa; lower pKa increases lipid solubility and tissue penetrance by increasing the fraction of local molecules that are uncharged –> enter membranes more readily

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20
Q

The intermediate chain in local anesthetics can either be an ____ or ____ moiety.

A

ester; amide

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21
Q

What determines the duration of action of local anesthetics? Why?

A

protein-binding capacity; it maintains the free concentration of anesthetic at an effective concentration for a longer period of time

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22
Q

What is use-dependent block?

A

the more the channel is open, the greater degree of local anesthetic binding and block; with more depolarization, the size of the inwards current decreases

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23
Q

What is a disadvantage of topical anesthetics?

A

the drug enters circulation

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24
Q

Name the toxin:

  • one of the most potent toxins known
  • found in Pufferfish, newts, and frogs
  • binds to and blocks the extracellular entrance of voltage-gated Na+ channels –> death by paralysis of respiratory muscles
A

tetrodotoxin (TTX)

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25
Q

What is epidural anesthesia?

A

injection of local anesthetic just outside the dura of the spinal canal

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26
Q

What are the disadvantages of infiltration anesthesia?

A
  • large doses are needed
  • absorption into circulation
27
Q

What can be used as an alternative anesthetic in pts allergic to amide and ester local anesthetics?

A

high dose promethazine

28
Q

Is the fractional block greater in small diameter or large diameter axons? Why is this important?

A

small; therefore pain sensation is the first functionality lost

29
Q

What is EMLA cream?

A

a mixture of lidocaine and prilocaine that exists as an oil at room temp and can thereby penetrate the skin

30
Q

What protein do local anesthetics bind to?

A

α-1 acid glycoprotein (only amide anesthetics)

31
Q

What is infiltration anesthesia?

A

injection of drug into tissue w/o consideration of the underlying nerves

32
Q

Which is the only local anesthetic that produces local vasoconstriction? How?

A

cocaine; it blocks NE reuptake

33
Q

What is saxitoxin (STX)?

A
  • one of the most potent toxins known
  • found in marine dinoflagellates (red tide)
  • binds to and blocks the extracellular entrance of voltage-gated Na+ channels –> death by paralysis of respiratory muscles
34
Q

Where does conduction block occur?

A

in smaller diameter, myelinated axons

35
Q

Local anesthetics have a tripartite structure, typically consisting of 1. a lipophilic aromatic portion; 2. an intermediate alkyl chain; 3. ______.

A

a hydrophilic amine portion

36
Q

What is nerve block anesthesia?

A

injection of a high conc of local anesthetic near a peripheral nerve or nerve plexus

37
Q

How do local anesthetics work?

A

block voltage-gated Na+ channels in peripheral nerves

38
Q

What happens in allergies to local anesthetics?

A

PABA is produced –> hypersensitivity

39
Q

Local anesthetics increase the stability of the _____ to prolong the refractory period.

A

inactivated state of the channel

40
Q

In local anesthetics, the names of the _____ have a single “I” whereas the names of the _____ have two “i’s.”

A

esters = 1 I amides - 2 i’s

41
Q

Local anesthetics block conduction in small diameter, myelinated and unmyelinated axons, such as the ____ fibers that signal pain sensation.

A

C

42
Q

What is intravenous regional anesthesia/Bier’s Block?

A

when blood is squeezed out of the limb or part of the body and a tourniquet placed, followed by injection of local anesthetic via a catheter

43
Q

This is injection of drug into tissue w/o consideration of the underlying nerves.

A

infiltration anesthesia

44
Q

What is tetrodotoxin (TTX)?

A
  • one of the most potent toxins known
  • found in Pufferfish, newts, and frogs
  • binds to and blocks the extracellular entrance of voltage-gated Na+ channels –> death by paralysis of respiratory muscles
45
Q

Where is the only place that blockade of APs can occur?

A

nodes of Ranvier

46
Q

Local anesthetics have a tripartite structure, typically consisting of 1. a lipophilic aromatic portion; 2. ______; 3. a hydrophilic amine portion.

A

an intermediate alkyl chain

47
Q

This is injection of a high conc of local anesthetic near a peripheral nerve or nerve plexus.

A

nerve block anestheisa

48
Q

What makes a local anesthetic more potent?

A

higher lipid solubility

49
Q

What is the binding site for local anesthetics?

A

the water-filled pore of the Na+ channel

50
Q

What is spinal anesthesia?

A

injection of anesthetic into the CSF

51
Q

What is the definition of local anesthesia?

A

loss of sensation in an area of the body

52
Q

Which kinds of anesthetics have longer durations of actions?

A

the amides

53
Q

Which local anesthetics are used for spinal anesthesia?

A
  • lidocaine (short)
  • bupivacaine (intermediate)
  • tetracaine (long lasting)
54
Q

Which vasoconstrictor often is added to local anesthetics?

A

epi

55
Q

How are ester local anesthetics terminated?

A

they’re hydrolyzed by an esterase (pseudocholinesterase) and by the liver

56
Q

Since block is use-dependent, unblock is _____.

A

also use-dependent

57
Q

Which local anesthetics are used in epidurals?

A
  • lidocaine (short)
  • bupivacaine (longer)
  • low conc bupivacaine + fentanyl for labor
58
Q

What does local anesthetic binding to its site cause?

A

physical obstruction of Na+ ion flow through the Na+ channels, preventing membrane depolarization and terminating APs

59
Q

How come cocaine analogs are safer than cocaine?

A

they are unable to block catecholamine reuptake

60
Q

Local anesthetics block ____ and ____ of nerve impulses (APs) by blocking the voltage-gated Na+ channels.

A

initiation; conduction

61
Q

Name 2 nerve block anesthetics.

A
  1. lidocaine (short duration)
  2. bupivacaine (longer duration)
62
Q

Where does excretion of local anesthetics occur?

A

in the kidney

63
Q

Why are vasoconstrictors added to local anesthetics?

A
  • to prolong duration of conduction blockade
  • reduce blood flow to the area (limit absorption)
  • prevent toxicity

aNeuro Exam 2- Lindsey's (23 decks)

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