Local Anesthetics

Front 1

local anesthetic mechanism of action?

Back 1

cationic form interacts with open sodium channels on inner surface of axon to block Na+ flow into axon thereby decreasing impulse conduction

Front 2

what is potency of local anesthetics related to?

Back 2

lipid solubility

Front 3

what determines duration of conduction block caused by local anesthetics?

Back 3

protein binding capacity (affinity): higher protein binding capacity associated with longer duration of action

Front 4

major determinant of onset of conduction block due to local anesthetic?

Back 4

pKa: nonionic form is associated with penetration of nerve cell membrane so most local anesthetics have pKa from 7.7-9.0

Front 5

vascular effects of local anesthetics and exception?

Back 5

all except cocaine are associated with vasodilation

Front 6

what is the effect of vasodilation of local anesthetic actions?

Back 6

decreased duration of action and prolonged onset time

Front 7

determinants of toxicity of local anesthetics?

Back 7

plasma and blood concentrations, total concentration, free concentration, ionization

Front 8

what determines plasma and blood concentrations, total concentration, and free concentration of local anesthetics?

Back 8

protein binding

Front 9

what is consequence of ionization to toxicity of local anesthetics?

Back 9

nonionic form involved in CNS penetration, ionic forms CNS toxic

Front 10

toxicity is directly related to what?

Back 10

lipid solubility

Front 11

how does site of action affect toxicity?

Back 11

the more vascular the site of injection, the more readily uptake can occur and more sudden and intense cns toxic effects will be

Front 12

what is added to many local anesthetics to prolong action?

Back 12

vasoconstrictors: epinephrine, ephedrine, phenylephrine

Front 13

possible side effects of adding vasoconstrictor to local anesthetic?

Back 13

HTN, tachycardia, cardiac arrhythmia, ischemia

Front 14

effect of cardiac toxicity of local anesthetics?

Back 14

direct myocardial depressant actions

Front 15

bupivacaine and etidocaine toxic effects on heart related to?

Back 15

highly lipid soluble and specific binding to cardiac conduction system

Front 16

toxic effect caused by prilocaine and mechanism?

Back 16

methemoglobinemia due to prilocaine oxidation of ferrous form of Hb to ferric form

Front 17

how can methemoglobinemia be reversed?

Back 17

methylene blue

Front 18

when is methemoglobinemia considered serious?

Back 18

relatively benign except in cases where oxygen transport is an important issue (particularly in children)

Front 19

when tissue toxicity with local anesthetics?

Back 19

related to concentration; at sufficient concentration are directly cytotoxic to nerve cells; narrow therapeutic index

Front 20

generally what are allergies to local anesthetics related to?

Back 20

methylparaben, an added preservative

Front 21

how are ester type local anesthetics metabolized and resulting half life?

Back 21

plasma cholinesterases thus have very short half lives (<1min)

Front 22

when is metabolism of ester type local anesthetics decreased?

Back 22

in patients with genetically atypical cholinesterase

Front 23

how are amide type local anesthetics metabolized and resulting half life?

Back 23

hepatic N-dealkylation and hydrolysis with half life of minutes

Front 24

when is metabolism of amide type local anesthetics decreased?

Back 24

in patients with liver disease or decreased hepatic blood flow

Front 25

which nerves are more easily anesthetized?

Back 25

those that are used most often or have been recently stimulated (more open Na+ channels)

Front 26

which nerves are less sensitive to effects of local anesthetics?

Back 26

resting nerves

Front 27

clinical uses of local anesthetics?

Back 27

surface, infiltrative, field block , nerve block, IV regional, spinal, epidrual anesthesia

Front 28

which are ester local anesthetics?

Back 28

procaine, cocaine, tetracain, chloroprocaine, benzocaine

Front 29

cocaine?

Back 29

ester; slow onset, short duration with unique characteristic of being a vasoconstrictor

Front 30

procaine?

Back 30

ester; slow onset, very short blood half-life and short duration of action due to extremely poor protein binding

Front 31

chloroprocaine?

Back 31

ester; rapid onset of action, short plasma half-life

Front 32

tetracaine?

Back 32

ester; slow onset, very short plasma half0life, long duration with limited systemic toxicity; generally used for spinal anesthesia

Front 33

amide local anesthetics?

Back 33

lidocaine, mepivacaine, bupivacaine, etidocaine, prilocaine, dibucaine, ropivacaine

Front 34

most commonly used local anesthetic in US?

Back 34

lidocaine

Front 35

lidocaine?

Back 35

amide; rapid onset with intermediate duration; used for topical, iv regional, spinal, epidural anesthesia; (15-20 min action)

Front 36

prilocaine?

Back 36

amide; rapid onset, intermediat duration and very low toxicity; metabolism to metabolit is associated with methemoglobinemia; used for infiltration and epidural anesthesia

Front 37

what is lidocaine and prilocaine cream used for?

Back 37

topical anesthesia in children: circumcision, intramuscular injections, heel lancing

Front 38

mepivacaine?

Back 38

amide; rapid onset, intermediate duration, intermediate toxicity; used for infiltration, epidural, spinal anesthesia; often with epi so need to be aware if epi is added or not

Front 39

bupivacaine?

Back 39

amide; slow onset, long duration, highly toxic (respiratory acidosis, hypoxia, cardiac toxicity); used for infiltration, epidural, spinal anesthesia

Front 40

etidocaine?

Back 40

amide; virtually identical clinically to bupivacaine; used for infiltration, epidural, spinal anesthesia

Front 41

dibucaine?

Back 41

amide; intermediate onset of very long duration, considerable potency, very high toxicity

Front 42

articaine?

Back 42

newest local anesthetic; very high lipid solubility so great penetration; become the local anesthetic of choice in most countries into which it has been introduced