EXAM #3: LOCAL ANESTHESIA Flashcards Preview

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Flashcards in EXAM #3: LOCAL ANESTHESIA Deck (39):
1

What are the types of local anesthesia?

1) Topical
2) Perineural Infiltration
3) Nerve Block
4) Spinal Block
5) Epidural block

2

What is the difference between a spinal block and an epidural block?

Spinal= injection into subarachnoid space
- More reliable
- Irreversible

Epidural= injection into the extradural space
- Less reliable
- More reversible

3

Outline the path of a pain signal to the brain.

1) Nociceptor
2) Sensory afferent
3) Dorsal horn
4) Spinothalamic tract
5) Somatosensory cortex

4

What is the result of blocking Na+ channels on primary sensory afferents?

Inhibition of firing i.e. less pain signals going to the brain

5

What is the difference between protonated and non-protonated LAs?

- Non-protonated (LA) are more lipophilic
- Protonated (LAH+) binds to the Na+ receptor and inhibits it

6

What are the three sites of action on a Na+ channel?

1) Extracellular side of receptor
2) Intracellular side of receptor*
3) Embed in the lipid bilayer and disrupt the geometry of receptor--impedes function*

****Most drugs do a combination of these two*****

7

What are the two broad categories of local anesthetics?

Amides
Esters

8

What two portions of amides and esters are conserved?

Aromatic ring
Tertiary amine

9

What is the difference between amides and esters?

Intermediate chain of the chemical structure

10

What is the mnemonic for telling the difference between amides and esters?

Amides= 2x "i"
Esters= 1x "i"

11

Generally, is the important clinical difference between the amides and esters?

Amides= longer half-life/ duration of action

Esters= short half-life/ duration of action

12

Why is there a difference in metabolism between amides and esters?

- Amides are metabolized in the liver
- Vs. esters that are metabolized in the blood

13

What enzyme metabolizes esters?

Butyrylcholinestersase

14

What is Cm?

Minimum anesthetic concentration: minimum concentration for a standard block

15

What is the relationship between fiber size and Cm?

Bigger fiber= bigger Cm

16

List the order in which nerve fibers will be blocked.

1) B
2) C
3) A-d
4) A-g
5) A-b
6) A-a

17

What is the effect of pH on Cm?

Increased pH= decreased Cm

18

What is the effect of Ca++ on Cm?

Increased Ca++ = Increased Cm

19

What is the effect of vasoconstrictors in local anesthesia?

Reduction in local blood flow will:
1) Increase duration of action
2) Reduce systemic absorption

20

What drug is used as a common vasoconstrictor in local anesthesia?

Epi

21

What areas should NOT be injected with epi as a vasoconstrictor in local anesthesia?

1) Digits
2) Toes
3) Earlobes
4) Nose
5) Penis

22

What is the most important factor that will affect the reversal of local anesthesia?

Absorption into general circulation

23

What enzyme metabolizes amides?

CYP p450

24

How will the half life of an amide change in a patient with liver disease?

Increased half-life/ duration of action

25

What is an important clinical factor to remember about Esters and allergies?

- The inactive metabolite of esters is "PABA"
- PABA is prone to allergic reaction

26

Is there cross-reactivity between amides and esters in terms of allergic reactions?

No, if allergic to one you can give the other

27

Which class of local anesthetics are less prone to systemic toxicity?

Esters b/c they are metabolized in the blood

28

Which local anesthetic is associated with systemic toxicity/ cardiac toxicity that leads to complete cardiac collapse and death?

Bupivicaine

29

What is the treatment for LAST or Local Anesthetic Toxicity?

IV lipid emulsion that functions as a "lipid sink" to absorb lipophilic toxin

30

List the amides.

Lidocaine
Bupivicaine
Ropivacaine
Articaine

31

List the esters.

Cocaine
Procaine
Tetracaine
Benzocaine
Chloroprocaine

32

What local anesthetic can be given topically and injected?

Lidocaine

33

What is the reference standard for local anesthesia?

Lidocaine

34

What drug is used most often as a spinal anesthetic for epidural infusion/ post-op pain?

Bupivacaine

35

What is Articaine indicated for?

Analgesia in dentistry

36

What is cocaine indicated for?

Topical anesthesia for ENT procedures

37

What is the clinical use of Benzocaine?

This drug has enhanced lipid solubility and is used as a topical anesthetic

38

What is the clinical indication for Chloroprocaine?

Epidural agent for labor
- Lower risk of systemic toxicity
- Lower risk for fetal exposure

39

What is Exparel-Liposome?

Encased bupivacaine that can be used for up to 72 hours of post-op pain relief

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