Exam5- Local Anesthetics

Question 1

local anesthetics vs analgesic drugs

Answer 1

analgesic= specifically inhibit nociceptive pathway
local= non-secific inhibitors of neuronal conduction

Question 2

afferent nociceptors

Answer 2

=Adelta and C fibers

-conduct thermal , intense mechanical, and chemical stimulation to a second order neuron or brain

Question 3

Local Anesthetic Mechanism of Action

Answer 3

block voltage gated Na+ channels on nerve membranes

=stops generation and conduction of action potentials

Question 4

locals will more readily reach their sites of action when they are in ___ form

Answer 4

LIPID SOLUBULE (UNCHARGED)

Question 5

all locals are strong/weak acids/bases?

Answer 5

WEAK BASES

Question 6

pH of all locals are between ___ and ____

Answer 6

7.5 and 9.5

Question 7

physiological pH =

Answer 7

7.4

Question 8

most of the drug will begin it its protonated/non protonated form

Answer 8

protonated
drug pH = 7.5 - 9.5
physiological pH = 7.4

Question 9

pKa = pH at___

Answer 9

equilibrium of BH+ and B

Question 10

when pH= 7.4 base is protonated/nonprotonated

Answer 10

BH+

Question 11

when pH>pKa there is more ___

Answer 11

B

Question 12

lidocaine has a pKa of

Answer 12

7.9

Question 13

the closer pKa is to physiological pH the ____ the onset of the drug.

Answer 13

faster

Question 14

fiber diameter/myelination affects___

Answer 14

susceptibility to local anesthetic

• larger nerves are less susceptible to block than smaller nerves
• myelinated nerves are less susceptible than non-myelinated n.

Question 15

firing frequency and susceptibility to locals

Answer 15

locals bind active channels more readily than resting channel

Question 16

position of fiber affects its susceptibility to locals….

Answer 16

superficial fibers are more easily reached ∴ more susceptible

Question 17

pain and temperature neuron fiber type

Answer 17

delta

Question 18

pain and temp neuron diameter

Answer 18

2-5um ∴ easy to target

Question 19

order of nerve function loss:

Answer 19

sympathetic
pain 
cold
warm 
touch 
motor

Question 20

critical length hypothesis

Answer 20

in order to be effective the field of action of a local anesthetic must include at least 3 nodes of Ranvier

Question 21

axon size and number of nodes ranvier

Answer 21

larger axons= less nodes
small axons= more nodes
∴smaller axons are more susceptible to locals bc there are more nodes within a given nerve block field

Question 22

amide locals list

Answer 22

lidocaine 
mepivacaine
prilocaine
bupivacaine
articaine
ropivacaine

Question 23

ester locals list

Answer 23

cocaine
procaine
tetracaine
benzocaine
proparacaine

Question 24

amides or esters are metabolized in blood

Answer 24

esters
-readily hydorlyzed by esterases in blood into PABA
PABA= common allergy

Question 25

amide metabolism

Answer 25

cytochrome p450 in liver ∴ have a longer duration of action than esters -cause less allergic reactions than esters

Question 26

ester vs amide pKa

Answer 26

esters usually have a higher pKa | ∴ slower onset and shorter duration

Question 27

amides with short duration of action

Answer 27

prilocaine and lidocaine

Question 28

amides with intermediate duration of action

Answer 28

mepivacaine | articaine

Question 29

amides with long duration of action

Answer 29

ropivacaine

Question 30

three routes of local administration

Answer 30

1. topical 2. infiltration/nerve block 3. epidural/spinal

Question 31

____ are commonly used for topical applicaiton

Answer 31

binzocaine | tetracaine

Question 32

___ are commonly used for infiltration

Answer 32

``` licocaine mepivacaine prilocaine articaine bupivacaine (all amides) ```

Question 33

all locals except cocaine are vaso____

Answer 33

dilators

Question 34

locals that are the least vasodilators

Answer 34

mepivacaine prilocaine ∴ don't need to be delivered with a vasoconstrictor

Question 35

vasoconstrictors benefits

Answer 35

1. prolong the duration of anesthesia by preventing diffusion from the site of action 2. limit systemic toxicity of local anesthetics 3. reduce blood loss for surgical procedures

Question 36

epinephrine hydorcholide

Answer 36

most common with local injection | only targets alpha-1 receptors

Question 37

levonordefrin hydrochloride

Answer 37

less common | selective alpha-1 receptor agonists

Question 38

alpha-1 agonists should be used with caution w/___

Answer 38

patients with cardiovascular disease because they cause hypertension **ALWAYS avoid delivery into systemic circulation and only administer via infiltration when necessary at the lowest dose possible

Question 39

locals and MAO oxidase inhibitors

Answer 39

-can increase the effects potentially resulting in a hypertensive crisis

Question 40

lidocaine

Answer 40

=most commonly used local anesthetic - common prep= 2% lidocaine hydrochloride with 1:100,000 epinephrine - safe for kids - inexpensive

Question 41

articaine properties

Answer 41

similar to lidocaine

Question 42

bupivacaine properties

Answer 42

prolonge duration of action

Question 43

mepivacaine properties

Answer 43

very little vasodilation | doesn't require a vasoconstrictor

Question 44

prilocaine properties

Answer 44

doesn't require a vasoconstrictor

Question 45

benzocaind

Answer 45

=ester used in dentistry -used topically as a numbing agent (no longer via infiltration)

Question 46

one cartridge=___ ml

Answer 46

1.8ml

Question 47

2% =___ mg/ml | =___ mg/cartridge

Answer 47

20mg/ml | =36mg/cartridge

Question 48

1:10000 epi=___ ug/ml | =___ug/cartridge

Answer 48

10ug/ml | =18ug per cartridge

Question 49

EMLA

Answer 49

Eutectic mixture of local anesthetics =2.5%prilocaine and 2.5% lidocaine -for pain and itching

Question 50

LMX-4

Answer 50

=liposomal formulation of 4% lidocaine | -for pain and itching

Question 51

topical locals for pain and itching

Answer 51

EMLA LMX-4 tetracaine benzocaine

Question 52

ophthalmology locals

Answer 52

proparacaine -for ocular proceudres repeated administration=corneal damage/blindness

Question 53

locals for minor lacerations

Answer 53

=topical analgesics with epinephrine TAC= tetracaine, adrenalin/epi, cocaine LET= lidocaine, epinephrine, tetracaine

Question 54

locals for surgical wounds

Answer 54

pre-surgical infilatration

Question 55

locals for major lacerations

Answer 55

pack with agents soaked with TAC or LET

Question 56

digital injury locals

Answer 56

DO NOT USES EPINEPHRINE you can use digits form ischemia!!!!

Question 57

induced nerve block

Answer 57

administered into space around spinal column, below L1 1. epidural space = epidural block 2. subarachnoid space =spinal block 3. paravertebral region= paravertebral block (more diffuse)

Question 58

epidural anesthesia

Answer 58

- between L3 and L4 through ligament flavor - most commonly ropivacaine - bupivacaine is also used but is more cardiotoxic (arrhythmias)

Question 59

systemic toxicity of local anesthetic

Answer 59

CNS: excitation initially then severe toxicity = seizures Cardiovascular: decreased conduction, arrhythmias hypotension, reduced autonomic activity Hemoblobin: prilocaine is metabolized in the liver and then converts hemoglobin to methemoglobin

Question 60

PABA

Answer 60

paraaminobenzoic acid | =metabolite of ESTER anesthetics