37: Local Anesthetic Agents

Question 1

loss of sensation limited to a local area or region of the body

Answer 1

local anesthesia

Question 2

drug that blcoks generation and propagation of nerve impulse that results in reversible, regional loss of function

Answer 2

local anesthetic

Question 3

advantages and disadvantages of perineural infiltration v. nerve block

Answer 3

• perineural requires larger amounts of drug
  + perineural is easy to do
• nerve block requires more skill
  + less drug used in nerve block

Question 4

injection of agent into CSF in lumbar subarachnoid space to reach the roots of spinal nerves that supply specific region

Answer 4

spinal block

more reliable than epidural, but time limited

Question 5

injection of agent into extradural space and blockade of the nerve root as it passes through the space

Answer 5

epidural block

not time limited, can be used 4-7 days post op

Question 6

primary MOA of local anesthetics

Answer 6

blockade of voltage-gated sodium channels

Question 7

site of action of most clinically used drugs =

Answer 7

intracellular receptor and membrane expansion

Question 8

“caine” =

Answer 8

local anesthetic

Question 9

caine with two “i” in name =

Answer 9

amides

esters usually only have one i

Question 10

t or f: all local anesthetics are acids

Answer 10

false

all local anesthetics are weak bases

Question 11

most active form at sodium receptor =

form important for lipid penetration of membranes =

Answer 11

cationic form

uncharged base

Question 12

smaller and more lipophilic local anesthetics are…

Answer 12

more potent
have faster rate of interaction with sodium channels
have longer duration of action

Question 13

which of the two categories of local anesthetics is metabolized in the liver and has a longer-half life (longer duration of action)?

Answer 13

amides

esters are metabolized in the plasma and have a short duration of action

Question 14

minimum anesthetic concentration Cm =

Answer 14

minimum concentration of drug for standard block

this is a relative standard of potency

Question 15

increasing fiber size —> _______ Cm

Answer 15

increasing

smallest fibers are most sensitive and myelinated nerves are more sensitive than non-myelinated

Question 16

increasing pH —> ________ Cm

Answer 16

decreasing

Question 17

____ frequency nerves are more sensitive to anesthetics

Answer 17

higher

Question 18

increasing Ca2+ concentration –> ______ Cm

Answer 18

increasing

Question 19

why would you use a vasoconstrictor such as epinephrine with anesthetics?

Answer 19

vasoconstrictors reduce local blood flow and reduce systemic absorption and reduce toxicity, increased duration of action

**never inject LA with vasoconstrictor into areas with end arterioles (digits, toes, ear lobe, penis)

Question 20

most important factor affecting the reversal of local anesthesia

Answer 20

absorption into circulation

Question 21

drugs with _____ protein binding produce less toxicity

Answer 21

little

Question 22

esters are metabolized in the plasma via ______ into ______

Answer 22

BChE

PABA * prone to allergic reactions

Question 23

what is the treatment for LAST local anesthetic toxicity

Answer 23

intravenous lipid emulsion aka IntraLipid

forms a lipid sink to absorb circulation lipophilic toxin

Question 24

which anesthetic can be given topically AND by injection?

Answer 24

lidocaine

Question 25

most common epidural going to C-section when total motor block also desired

Answer 25

2% lidocaine

Question 26

toxicity of lidocaine

Answer 26

potential for transient neurological symptoms TNS with spinal administration- pan and/or increased sensitivity to touch

Question 27

clinical use for bupivacaine

Answer 27

• agent of choice for epidural infusion used for labor analgesia and postoperative pain
• excellent spinal anesthetic

Question 28

clinical use for articaine

Answer 28

dental anesthetic

Question 29

current use for cocaine

Answer 29

topical anesthetic for ENT procedures

Question 30

topical only anesthesia due to enhanced lipid solubility

Answer 30

benzocaine

Question 31

clinical use for chloroprocaine

Answer 31

used as epidural agent for labor anesthesia (especially cesarean section) due to lower risk of systemic toxicity or fetal exposure

Question 32

encased bupivicaine that provides relief for up to 72 hr post op given as single dose injectio

Answer 32

exparel-liposome

Question 33

lidocaine + prilocaine

Answer 33

EMLA eutectic mixture of local anesthetics

used as topical anesthetic on intact skin

Question 34

tetracaine + adrenalin + cocaine =

Answer 34

TAC

topical used in pediatric emergency rooms

Question 35

neurolytic agents are not reversible and achieve a permanent local anesthesia. what are their uses?

Answer 35

permanent block in terminal cancer or some other chronic condition

ethyl alcohol and phenol