EXAM #3: LOCAL ANESTHESIA Flashcards Preview

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

What are the types of local anesthesia?

A

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

2
Q

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

A

Spinal= injection into subarachnoid space

  • More reliable
  • Irreversible

Epidural= injection into the extradural space

  • Less reliable
  • More reversible
3
Q

Outline the path of a pain signal to the brain.

A

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

4
Q

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

A

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

5
Q

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

A
  • Non-protonated (LA) are more lipophilic

- Protonated (LAH+) binds to the Na+ receptor and inhibits it

6
Q

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

A

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
Q

What are the two broad categories of local anesthetics?

A

Amides

Esters

8
Q

What two portions of amides and esters are conserved?

A

Aromatic ring

Tertiary amine

9
Q

What is the difference between amides and esters?

A

Intermediate chain of the chemical structure

10
Q

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

A
Amides= 2x "i" 
Esters= 1x "i"
11
Q

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

A

Amides= longer half-life/ duration of action

Esters= short half-life/ duration of action

12
Q

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

A
  • Amides are metabolized in the liver

- Vs. esters that are metabolized in the blood

13
Q

What enzyme metabolizes esters?

A

Butyrylcholinestersase

14
Q

What is Cm?

A

Minimum anesthetic concentration: minimum concentration for a standard block

15
Q

What is the relationship between fiber size and Cm?

A

Bigger fiber= bigger Cm

16
Q

List the order in which nerve fibers will be blocked.

A

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

17
Q

What is the effect of pH on Cm?

A

Increased pH= decreased Cm

18
Q

What is the effect of Ca++ on Cm?

A

Increased Ca++ = Increased Cm

19
Q

What is the effect of vasoconstrictors in local anesthesia?

A

Reduction in local blood flow will:

1) Increase duration of action
2) Reduce systemic absorption

20
Q

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

A

Epi

21
Q

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

A

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

22
Q

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

A

Absorption into general circulation

23
Q

What enzyme metabolizes amides?

A

CYP p450

24
Q

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

A

Increased half-life/ duration of action

25
Q

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

A
  • The inactive metabolite of esters is “PABA”

- PABA is prone to allergic reaction

26
Q

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

A

No, if allergic to one you can give the other

27
Q

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

A

Esters b/c they are metabolized in the blood

28
Q

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

A

Bupivicaine

29
Q

What is the treatment for LAST or Local Anesthetic Toxicity?

A

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

30
Q

List the amides.

A

Lidocaine
Bupivicaine
Ropivacaine
Articaine

31
Q

List the esters.

A
Cocaine 
Procaine 
Tetracaine 
Benzocaine
Chloroprocaine
32
Q

What local anesthetic can be given topically and injected?

A

Lidocaine

33
Q

What is the reference standard for local anesthesia?

A

Lidocaine

34
Q

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

A

Bupivacaine

35
Q

What is Articaine indicated for?

A

Analgesia in dentistry

36
Q

What is cocaine indicated for?

A

Topical anesthesia for ENT procedures

37
Q

What is the clinical use of Benzocaine?

A

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

38
Q

What is the clinical indication for Chloroprocaine?

A

Epidural agent for labor

  • Lower risk of systemic toxicity
  • Lower risk for fetal exposure
39
Q

What is Exparel-Liposome?

A

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

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