Exam 11: Local Anesthetics Flashcards Preview

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Flashcards in Exam 11: Local Anesthetics Deck (33):
1

Which part of local anesthetics' structure is important for their entry into the axon?

Lipophilic domain

2

Which part of local anesthetics' structure is important for their action at Na+ channels?

Hydrophilic domain

3

What are the two types of local anesthetics?

Amides (lidocaine)
Esters (procaine)

4

How are Amide local anesthetics metabolized?

Liver (microsomal enzymes)

5

How are Ester local anesthetics metabolized?

Plasma cholinesterase

6

How do the half-lives of Amides compare to Esters?

Amides have longer half-lives because they're metabolized by liver enzymes as opposed to Esters, which are metabolize by cholinesterase in the plasma

7

Which chemical form of local anesthetics enters the cell?

Unprotonated (LA)

8

Which chemical form of local anesthetics is "active" in inhibiting the Na_ channels?

Protonated (LAH+)
Intracellular pH is lower than extracellular

9

What is the order of neuron sensitivity to nerve block?

Most to least sensitive:
C (pain)
B (autonomics)
A' (pain/temp)
A (motor)
A+ (motor)

10

How can you numb an entire limb?

Intravenous regional anesthesia
Put a tourniquet on and inject LA IV
Only useful up to 2 hours

11

Spinal vs Epidural: Which needs more LA

Epidural

12

Spinal vs Epidural: Which is more intense of a block?

Spinal

13

3 Advantages of Epidural over spinal anesthesia

1. Not limited to below L2
2. No dural puncture = no post-dural puncture headache
3. You can leave a catheter in for long-term pain reduction and fine tune the dosage from there

14

Purpose of giving Epinephrine injection with local anesthetics

Causes vasoconstriction and decreasing absorption
Prolongs duration of effect and reduces the amount of LA needed

15

2 cautions with epinephrine injection

1. Can cause vasodilation at skeletal muscle beds, increasing toxicity
2. Dont use it at peripheral sites (nose, fingers, scrotum, ears)

16

Where can local anesthetics distribute?

Everywhere (cross BBB)
Amides are taken up in fat, brain, kidney, liver, muscle, gut.
Esters are metabolized too fast to be redistributed

17

What does CSF lack?

Cholinesterase

18

Local anesthetic side effects at low doses

Sleepiness, dizziness, restlessness
Lidocaine can cause euphoria

19

Local anesthetic side effects at high doses

Nystagmus, shivering, CNS depression, respiratory failure, convulsions

20

Treatment for local anesthetic toxicity

Benzos and barbiturates

21

Only local anesthetic with intrinsic vasoconstrictive properties

Cocaine
the rest are vasodilators

22

Which local anesthetic is the most cardiotoxic?

Bupivacaine

23

Which 2 local anesthetics can cause methemoglobinemia?

Prilocaine
Benzocaine

24

2 Amide Local Anesthetics

Lidocaine
Bupivacaine
Ropivacaine
Articaine

25

2 Ester Local anesthetics

Benzocaine
Cocaine

26

What is the most widely used Local Anesthetic today?

Lidocaine

27

Lidocaine

Amide Local anesthetic
Widely used (including spinals, epidurals, IV)
Excellent diffusions and penetration

28

Bupivacaine

Amide Local Anesthetic
Long Duration of Action!!!
Not recommended for IV injection due to cardiotoxicity

29

Caution with Bupivicaine

Dont inject IV
Cardiotoxic

30

Ropivacaine

New Amide local anesthetic
Useful for procedures where you don't want motor block (labor anesthesia) because it's less lipophilic than bupivacaine
Reduced CNS/Cardio toxicity
Pure enantiomer

31

Articaine

Amide Local Anesthetic
Safer than prilocaine because it metabolized by plasma carboxyesterase (less metabolized in liver)

32

Benzocaine

Ester local anesthetic
Used topically (skin/mucus membranes)
FDA warning for use in children due to methemoglobinemia

33

Cocaine!!!

Topical use only
Only Local anesthetic with inherent vasoconstrictive action
No need to co-administer with epi, this could increase toxicity