Mod 1 - Local Anesthetics & Loco-Regional Techniques 8/18

Question 1

what do local anesthetics do?

Answer 1

reversibly block generation/propagation of electrical impulses in nerves (sensory & motor blockade)

Question 2

what was the first local anesthetic ever?

what was the first synthetic derivative of cocaine in 1904?

Answer 2

cocaine

procaine

Question 3

when was lidocaine developed?

Answer 3

1943, WW2

Question 4

local anesthetics are used for 1 procedures, to (inc./dec.) systemic drugs in anesthetized animals, and also has benefits in the 2 period.

Answer 4

1. awake
   dec.
2. recovery

Question 5

what are local anesthetics MOA?

Answer 5

reversibly bind to & inactivate Na+ channels
- Na+ influx needed for depolarization of nerve & propagation of impulses along nerve
- nerve can’t depolarize b/c no Na+ influx
- sensation in area lost

Question 6

what are the two basic classes of local anesthetics?

Answer 6

1. amino amides
2. amino esters

Question 7

amino esters are metabolized in the 1. they are (stable/unstable) in solution and are more likely to cause 2 reactions.

Answer 7

1. plasma
   unstable
2. allergic hypersensitivity

Question 8

amino amides are metabolized in the 1. they are (stable/unstable) in solution. Pro tip: all amino amides have 2.

Answer 8

1. liver
   stable
2. the letter “i” twice in their name

Question 9

(lipid/water) solubility is an important characteristic of local anesthetics because it is directly related to ?.

Answer 9

lipid
potency

Question 10

(inc./dec.) lipid solubility leads to faster nerve penetration & blockade of ? channels.

Answer 10

inc.
Na+

Question 11

The more firmly the local anesthetic binds to the protein of the Na+ channel, the (shorter/longer) the duration of action.

Answer 11

longer

Question 12

local anesthetics exist in what 2 forms?

which form is capable of diffusing across nerve membranes to block Na+ channels?

Answer 12

1. ionized
2. non-ionized

non-ionized = faster onset time

Question 13

a dec. in pH shifts the equilibrium between the ionized form of a local anesthetic and the non-ionized form toward the ? form.

what does this cause?

Answer 13

ionized

slower onset of action

Question 14

all local anesthetics (except cocaine) are vaso(constrictors/dilators).

if this inc., then there is (faster/slower) absorption and therefore (shorter/longer) duration of action

Answer 14

vasodilators

faster
shorter

Question 15

you must block a minimum of ? Nodes of Ranvier consecutively to get an adequate loss of sensation.

Answer 15

3

Question 16

lidocaine
- (fast/mod/slow) onset
- (short/mod/long) duration
- can cause ? when injected
- IV CRI (inc./dec.) MAC, (inc./dec.) intestinal motility
- can treat what heart condition?

Answer 16

fast
mod
irritation
dec.
inc.
vtach

Question 17

T/F - cats can metabolize lidocaine well over time.

Answer 17

false!

Question 18

bupivacaine
- (fast/mod/slow) onset
- (short/mod/long) duration
- popularly used in ?
- there is more of a risk of ?
- do NOT give (route)
- can cause ?

Answer 18

slow
long
epidurals
toxicity
IV
intra-articular chondrotoxicity

Question 19

what are 5 dose-dependent complications of local anesthetics?

Answer 19

1. neurotoxicity
2. cardiotoxicity (esp. bupivacaine)
3. allergic reaction
4. methemoglobinemia
5. nerve & muscle injury (due to repeated injections)

Question 20

what can we give IV to a patient if we are worried about local anesthetic toxicity?

Answer 20

IV lipids - acts like sponge & collects anything lipophilic for excretion

Question 21

what is the most used technique involving local anesthetics that is used in vet medicine?

Answer 21

epidural administration of local anesthetics

Question 22

what is the goal of an epidural?

Answer 22

regional analgesia w/o losing motor function

Question 23

what are 4 advantages of an epidural?

Answer 23

1. simple & quick
2. improve peri-op analgesia
3. MAC/drug-sparing effects
4. ideal for C-sections (b/c no effect on offspring)

Question 24

what are 4 disadvantages of an epidural?

Answer 24

1. risk of motor dysfunction
2. Horner’s syndrome (if used on face)
3. urinary retention (drug choice)
4. must use aseptic technique!

Question 25

what is the gold standard for local anesthetic administration?

Answer 25

ultrasound-guided nerve blocks

Question 26

T/F - anesthesia is benign.

Answer 26

False - always comes with a risk
- modern techniques & drugs help make it as safe as possible