Local Anesthetics

Question 1

cocaine
procaine
chloroprocaine
tetracaine
benzocaine

Answer 1

esters:

hydrolysis by plasma and tissue cholinesterase

higher allergy incidence - cross allergy to all esters

shorter acting

Question 2

lidocaine
prilocaine
ropivacaine
bupivicaine
articaine
mepivacaine

Answer 2

amides

metabolized by liver CYP1A2 CYP3A4

low allergy incidence - no cross allergy

longer acting - more lipophilic and protein bound

Question 3

general structure of local anesthetic

Answer 3

hydrophilic (quaternary amine)

lipophilic (benzene ring)

intermediate chain

Question 4

local anesthetic ionization

Answer 4

hydrophilic side can become ionized

need to be non-ionized to pass through cell membrane, then need to ionize to attach to Na channel receptor

Question 5

local anesthetic pKa tells _____

Answer 5

onset time

the closer to 7.4, the faster the onset

Question 6

addition of epinephrine

Answer 6

decreased absorption into systemic circulation

decreased onset time and peak plasma concentration

increased motor and sensory blockage, duration, and area

Question 7

procaine

Answer 7

1%
14 mg/kg

short

Question 8

chloroprocaine

Answer 8

3%

11 mg/kg (14)

Question 9

tetracaine

Answer 9

1%
1 mg/kg

long

Question 10

cocaine

Answer 10

4%
3 mg/kg (topical)
200 mg total

*high toxicity, use only as topical
blocks reuptake of epinephrine

Question 11

lidocaine

Answer 11

1% or 2%
4 mg/kg (7)

medium

Question 12

mepivacaine

Answer 12

2%
4 mg/kg (7)

medium

Question 13

prilocaine

Answer 13

3%
7 mg/kg (8.5)

medium

Question 14

bupivicaine

Answer 14

0. 75% - not allowed in US
1. 5 mg/kg (3.2)

**binds preferentially to cardiac receptors

long

Question 15

ropivicaine

Answer 15

0.75%
3 mg/kg (3.5)

long

Question 16

local anesthetic - ion trapping

Answer 16

trapped in acidic locations - fetal pH lower, in acidosis trapper in brain

give with CO2, lowers pH in nerve cell thereby ionizing anesthetic once in cell

give with bicarbonate, more non-ionized to transport into cell

Question 17

local anesthetic toxicity

Answer 17

1. lightheadedness, tinnitus, circumoral and tongue numbness
2. visual disturbances
3. muscular twitching
4. convulsions
5. unconsciousness
6. coma
7. respiratory arrest
8. CVS depression

usually occurs within first 5 minutes

Question 18

local anesthetic toxicity treatment

Answer 18

1. airway management
2. benzos for seizures
3. during CPR: small doses of epi, no vasopressin or calcium channel/beta blockers
4. lipid emulsion therapy: 1.5 ml/kg 20% bolus, infusion 0.25 ml/kg/min for 10 minutes — if not stable, repeat bolus, increase infusion to 0.5

Question 19

tumescent anesthesia

Answer 19

used by plastic surgeons - 35-55 mg/kg of lidocaine with epinephrine for liposuction, 28 mg/kg for others

monitor for 12-16 hours

Question 20

max dose of epinephrine

Answer 20

3-4 mcg/kg

Question 21

epinephrine metabolism

Answer 21

• monoamine oxidase

- roughly 20 minutes