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Flashcards in Local anesthetics Deck (36)
1

Mech of Local anesthetics

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

2

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

reversibly blocking

3

Topical application of anesthetic

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

4

Local infiltration of anesthesia

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

5

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

Nerve block anesthetics

6

injection into the cerebrospinal fluid in the lumbar space

spinal anesthesia

7

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

Epidural anesthesia

8

Locals work directly on nerve cells to block their ability to

conducnt impulses

9

What fiber types do locals work on?

every type

10

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

nociceptic

11

Local anesthetics bind directly to voltage-dependent ______channels

sodium

12

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

intracellular

13

What form do local anesthetics bind in?

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

14

All local anesthetics are

all weak bases
--uncharged in its protonated form so it can diffuse through epineurium and travel thorugh membrane

15

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

slow depolarization
reduces height of AP
reduces size of AP

16

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

slow axonal conduction
prevents propagation
increaes threshold potential

17

What happens to the RMP d/t local anesthetics

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

18

When do local anesthetics get into channel?

get into channel when its opened

19

what state do local anesthetics prefer to bind in?

higher affinity in the inactive channel over the unopened channel

20

degree of block by local anesthetic depends on

the frequency of nerve stimulation and the resting membrane potential

21

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

resting

22

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

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

23

When channel is in resting state it is

inactive and open

24

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

charged
uncharged

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

ionized

26

Why are vasoconstrictors given with local anesthetics?

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

27

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

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

28

Order of pain block
(recovery is in reverse)

pain
cold
warmth
touch
deep pressure
motor

29

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

have conduction or transmission of impulses (CNS or muscles)

30

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

circulation

31

what type of injection can result in irreversible damage

intraneuronal

32

What enantiomer is the least toxic

S-enatiomer

33

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

CNS stimulation
then depression

34

Why do we see CNS depression in local anesthetics

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

35

At higher doses of anesthetics we see

drowsiness, general depression, respiratory depression, potential respiratory arrest

36

Death from local anesthetics is related to

severe toxicity caused by respiratory depression