Local anesthetics

Question 1

Mech of Local anesthetics

Answer 1

Bind reversibly to a site within the pore of Na+ channels in nerves thus blocking ion movement through the pore

Question 2

locally, act on any part of the nervous system and any nerve fiber ____________action potential responsible for nerve conduction

Answer 2

reversibly blocking

Question 3

Topical application of anesthetic

Answer 3

for skin, mucous, ulcerated surface or opthalmic to produce anesthesia of cornea and conjunctiva

Question 4

Local infiltration of anesthesia

Answer 4

local injection of an agent into tissues irrespective of the course of cutaneous nerves
`provides regional anesthesia around sites of injection

Question 5

injection of a local anesthetic around indi nerves or nerve plexuses that lead to operative site

Answer 5

Nerve block anesthetics

Question 6

injection into the cerebrospinal fluid in the lumbar space

Answer 6

spinal anesthesia

Question 7

local injection into the epidural space in the sacral, thoracic, lumbar, or cervical regions

Answer 7

Epidural anesthesia

Question 8

Locals work directly on nerve cells to block their ability to

Answer 8

conducnt impulses

Question 9

What fiber types do locals work on?

Answer 9

every type

Question 10

Locals work by blocking action potential propagation on
______ neurons, eliminate pain sensation
- completely reversible; no nerve damage

Answer 10

nociceptic

Question 11

Local anesthetics bind directly to voltage-dependent ______channels

Answer 11

sodium

Question 12

Locals bind to a site on the _____ side of the Na channel (segment 6 in domain IV)

Answer 12

intracellular

Question 13

What form do local anesthetics bind in?

Answer 13

bind in the cationic form, but must reach their site of action by penetrating the nerve
sheath and axonal membrane in the unionized species

Question 14

All local anesthetics are

Answer 14

all weak bases

–uncharged in its protonated form so it can diffuse through epineurium and travel thorugh membrane

Question 15

Locals will inhibit voltage gated Na channels
effect on rate of depolarization?
On height of AP?
On rise of AP?

Answer 15

slow depolarization
reduces height of AP
reduces size of AP

Question 16

Locals will inhibit voltage gated Na channels
effect on axonal condution
on propagation of AP
on threshold potential

Answer 16

slow axonal conduction
prevents propagation
increaes threshold potential

Question 17

What happens to the RMP d/t local anesthetics

Answer 17

NO CHANGE!!! voltage gated Na play no role in RMP

Question 18

When do local anesthetics get into channel?

Answer 18

get into channel when its opened

Question 19

what state do local anesthetics prefer to bind in?

Answer 19

higher affinity in the inactive channel over the unopened channel

Question 20

degree of block by local anesthetic depends on

Answer 20

the frequency of nerve stimulation and the resting membrane potential

Question 21

______nerves much less sensitive to block compared to one that is repetitively stimulated

Answer 21

resting

Question 22

nerves with more positive membrane potential more sensitive to block… occurs because:

Answer 22

1) gain access to the channel binding site more easily when the channel is open
2) have higher affinity for the inactivated channel than for resting channels

Question 23

When channel is in resting state it is

Answer 23

inactive and open

Question 24

______form binds to the channel but________ form penetrates into the nerve; thus, alterations in the extracellular pH can influence efficiency

Answer 24

charged

uncharged

Question 25

sites of inflammation or infection have lower pH; local anesthetic is in the _______ form and therefore less diffusion across membranes producing less effective block

Answer 25

ionized

Question 26

Why are vasoconstrictors given with local anesthetics?

Answer 26

decreases rate of vascular absorption, increases the depth of anesthesia less systemic absorption so less toxicity and increases the maximal dose that can be given

Question 27

in general, autonomic fibers, small non-myelinated C fibers (pain sensation), and small myelinated Aδ fibers (pain and temp) are blocked before

Answer 27

larger myelinated Aδ, Aβ, and Aα fibers (mediating postural, touch, pressure, and motor information)

Question 28

Order of pain block | recovery is in reverse

Answer 28

``` pain cold warmth touch deep pressure motor ```

Question 29

Toxicity of locals: | interfere with the function of organs that:

Answer 29

have conduction or transmission of impulses (CNS or muscles)

Question 30

Systemic toxic rnx are related to high conc of local anesthetic in:

Answer 30

circulation

Question 31

what type of injection can result in irreversible damage

Answer 31

intraneuronal

Question 32

What enantiomer is the least toxic

Answer 32

S-enatiomer

Question 33

We see CNS _____ first then at higher doses we see _____

Answer 33

CNS stimulation | then depression

Question 34

Why do we see CNS depression in local anesthetics

Answer 34

depression of cortical inhibitor neurons: see restlessness, tremors and convulsions

Question 35

At higher doses of anesthetics we see

Answer 35

drowsiness, general depression, respiratory depression, potential respiratory arrest

Question 36

Death from local anesthetics is related to

Answer 36

severe toxicity caused by respiratory depression