Anesthetics - Local

Question 1

amide local anasthetics

Answer 1

lidocaine, prilocaine, bupivacaine

Question 2

ester local anesthetics

Answer 2

procaine, tetracaine

Question 3

MOA of local anesthetics

Answer 3

voltage-gate sodium channel block; drug has preference for activated & inactivated states so frequency of nerve depol is important in allowing binding

Question 4

describe the differential blockade

Answer 4

small myelinated & non-myelinated fibers are most sensitive (B & C fibers) while large myelinated fibers are least sensitive (A)

Question 5

describe the chemistry of the local anesthetics

Answer 5

Majority are weak bases with Pka ~ 8 (therefore at extraneural pH of 9, 10:1 of base will be non-ionized & at intraneural pH of 7, 10:1 will be ionized)

Question 6

describe the anatomical distribution of local anesthetics

Answer 6

Anesthetic runs proximal to distal & recovery runs proximal to distal

Question 7

describe systemic toxicity of local anesthetics

Answer 7

tinnitus, metallic taste, oral numbness, seizures

Question 8

which drugs can cause methemoglobinemia

Answer 8

prilocaine > benzocaine

Question 9

how do you treat methemoglobinemia

Answer 9

∙ IV methylene blue as antidote

∙ or ascorbic acid

Question 10

which is more potent and more cardiotoxic

Answer 10

bupivacaine

Question 11

which are SA

Answer 11

procaine (slow onest & short duration)

Question 12

which are intermediate acting

Answer 12

lidocaine, prilocaine (rapid onset)

Question 13

which are LA

Answer 13

bupivacaine, tetracaine (slow onset)

Question 14

describe metabolism & elimination of amides

Answer 14

hepatic metabolized & renal elimination – metabolism affected by CV status, liver dz, toxemia of pregnancy, cimetidine, volatile anesthetics, b-blockers

Question 15

reversal agent for vasoconstrictor

Answer 15

phentolamine (non selective alpha antagonist)

Question 16

describe metabolism & elimination of esters

Answer 16

non-specific esterase enzymes & renal elimination – metabolism affected by liver dz, pregnancy, chemo & atypical enzyme activity

Question 17

what causes the differences in onset & duration

Answer 17

Differences in onset & duration from lipid solubility, dissociation constant, chemical linkage & protein binding

Question 18

topical use only

Answer 18

benzocaine

Question 19

what is the purpose of giving with vasoconstrictor

Answer 19

remove concentration gradient and prevent systematization

Question 20

use for mucosal membranes

Answer 20

benzocaine

Question 21

DDIs for vasoconstrictors

Answer 21

possible with BB, TCAs, halothane, HTN, heart block, cerebral vascular insufficiency

Question 22

which is useful for post op analgesia

Answer 22

bupivacaine

Question 23

AE of benzocaine

Answer 23

methemoglobinemia

Question 24

describe baricity

Answer 24

Baricity = density compared to CSF. Drug distribution depends of baricity and patient orientation. ↑solution temperature = ↑spread (due to ↓viscosity).

Question 25

if a spinal block is given with a dextrose infusion, will it have more effect at the same level, superior or inferior to the injection point

Answer 25

inferior (increased density)