Local Anesthetics

Question 1

influences distribution and excretion

Answer 1

protein binding

Question 2

influences redistribution and intrinsic LA potency

Answer 2

lipid solubility

Question 3

racemic mixtures

Answer 3

mepivacaine (50:50 mixture of enantiomers)

bupivacaine (50:50 mixture of enantiomers)

Question 4

MOA of local anesthetics (LA’s)

Answer 4

Bind to voltage-gated Na+ channels and block Na+ current, therefore reducing excitability of tissues (cardiac, neuronal, CNS)

Question 5

LAs are weak (acids/bases) that have pKa values (above/below) physiologic pH

Answer 5

LAs are weak bases that have pKa values above physiologic pH

Question 6

Potency depends on

Answer 6

lipid solubility

Question 7

Onset depends on

Answer 7

pKa and ionization

Question 8

metabolism of esters

Answer 8

• hydrolyzed by pseudocholinesterase

- which = short plasma half-life

Question 9

metabolism of amides

Answer 9

• liver metabolism (therefore hepatic blood flow and function are important!!)

Question 10

systemic toxicity is more likely in (amides/esters)

Answer 10

amides

Question 11

fibers most sensitive to blockade

Answer 11

B fibers - SNS

• small fibers
• myelinated fibers

Question 12

Duration depends on

Answer 12

protein binding

Question 13

What concept is analogous to ED50 for LAs?

Answer 13

mimimum effective concentration (Cm) is the concentration of LA that is required to block conduction

Question 14

What are the 3 possible configurations of the voltage gated Na+ channel?

Answer 14

activated - open

inactivated - closed

rested - closed

Question 15

Order of loss of nerve sensations

Answer 15

1. Autonomics
2. Pain
3. Cold
4. Warmth
5. Touch
6. Pressure
7. Vibration
8. Proprioception
9. Motor function

Question 16

potentially can cause methemoglobinemia

Answer 16

prilocaine

Question 17

treatment of methemoglobinemia

Answer 17

methylene blue 1-2 mg/kg IV (max dose 8mg/kg)

Question 18

LA toxicity of combinations are (additive/synergistic)

Answer 18

additive

Question 19

Maximum Dose: Lidocaine

Answer 19

Alone: 300 or 4.5 mg/kg

with Epi: 500 or 7 mg/kg

Question 20

Maximum Dose: Bupivacaine

Answer 20

Alone: 175 or 2.5 mg/kg

with Epi: 200 or 2.8 mg/kg

Question 21

highest to lowest protein binding

Answer 21

bupi > ropi > mepiva > lido > procaine > 2-chloroprocaine

Question 22

Local anesthetics primarily block which channels?

Answer 22

voltage gated sodium channels

Question 23

Immediate treatment of local anesthetic induced convulsions with?

Answer 23

supplemental oxygen therapy
support of ventilation
intralipid 100ml
midaz as needed