Local Anesthetics

Question 1

What classes of nerve fibers are myelinated?

Answer 1

A and B

Question 2

What are the fastest nerves to block?

Answer 2

myelinated and small

Question 3

What nerve class represents the sympathetics?

Answer 3

B (preganglionic sympathetics)

Question 4

What is the function of C fibers?

Answer 4

visceral pain (unmyelinated)

Question 5

What are the 4 functions of A fibers?

Answer 5

1) motor (alpha)
2) tactile, proprioception (beta)
3) muscle tone (gamma)
4) pain, cold temp (delta)

Question 6

What is the rank order of the fastest nerve types to block?

Answer 6

symps > sensory > motor

Question 7

What are the 3 stages of the sodium channel gate?

Answer 7

1) resting
2) open
3) inactivated

Question 8

Define frequency dependent blockade?

Answer 8

local anesthetics preferentially bind inactivated and open states rather than resting (want M open)

Question 9

What is the name of the local anesthetic binding site?

Answer 9

R

Question 10

What are the two molecular classes of anesthetics?

Answer 10

1) amides (2 i’s in the name. Ex: Lidocaine)

2) esters (1 i in the name. Ex: cocaine)

Question 11

True or false: binding occurs on the cytoplasmic side of the receptor?

Answer 11

TRUE (R site)

only uncharged can get thru

Question 12

What determines the onset time of local anesthetics?

Answer 12

pH and pKa (why given with sodium bicarb a lot)

Question 13

What determines the potency of LAs?

Answer 13

lipid solubility

Question 14

What determines the duration of LAs?

Answer 14

protein binding

Question 15

What are 2 adjuncts given with LAs?

Answer 15

1) epinephrine (used for vasoconstriction - keeps the drug in the neighborhood for drugs that vasodilate - not helpful for drugs that are protein bound)
2) alpha 2 agonists

Question 16

What is the only LA that can be used IV?

Answer 16

lidocaine

Question 17

What is an indication of neuraxial anesthesia?

Answer 17

surgery at chest or below

Question 18

What is the main difference between a spinal and epidural block?

Answer 18

spinal: drug deposited at L3-L5
epidural: any level, site of action is nerve roots (more targeted)

Question 19

What are the cardiovascular effects of neuraxial anesthesia?

Answer 19

bradycardia (unopposed vagal stim since you block symps)

Question 20

What are the 4 factors that absorption depeneds on?

Answer 20

1) vascularity 
(ICNB > caudal > epidural > brachial plexus > sciatic)
2) props of durg
3) props of patient
4) addition of vasoconstrictos

Question 21

How are esters eliminated?

Answer 21

plasma cholinesterase

Question 22

How are amides eliminated?

Answer 22

liver

Question 23

Do you give more or less drug when combining it with epi?

Answer 23

MORE

Question 24

What drug is NOT ok to use to treat arrhythmias?

Answer 24

lidocaine

Question 25

What is a specific therapy for toxicity of LAs?

Answer 25

intralipid (creates a sink that LA can be sequestered into)