Local Anesthetics

Question 1

how are local anesthetics classified

Answer 1

by bond between hydrocarbon and lipophilic portion

ester -CO-

amide -NHC-

Question 2

MoA of local anesthestics

Answer 2

blocaks voltage-gated Na channels in neuronal cell membrane

slows rate of depolarization

Question 3

which fibers are blocked first

Answer 3

smaller diameter fibers

less myelination

sympathetic, pain

Question 4

T/F with brachial plexus block motor fibers are blocked first

Answer 4

True

motor fibers are on periphery of nerve trunk and sensory fibers in center

Question 5

local anesthestics are weak acids/bases

Answer 5

bases

acidic tissues (infection) increase ionized portion which is inactive

Question 6

what are potency, onset and duration affected by

Answer 6

pK

protein binding

lipid solubility

Question 7

lower pK (closer to tissue pH) →

Answer 7

faster onset

Question 8

higher protein binding →

Answer 8

longer duration of action

Question 9

higher lipid solubility→

Answer 9

higher potency

Question 10

why add bicarbonate

Answer 10

faster onset and prolonged duration

less sting on injection

Question 11

toxicity is

Answer 11

additive

Question 12

toxicity

Answer 12

methemoglobinemia

neurotoxicity

chondrotoxicity

systemic

Question 13

what caused severe methemogloinemia in and was discontinued in vet med

Answer 13

benzocaine + tetracaine

laryngeal spray for intubation

Question 14

T/F preservative-free versions should be used for epidural and spinal anesthesia

Answer 14

True

Question 15

what is the first sign of cardiovascular collapse with bupivacaine

Answer 15

death

Question 16

systemic toxicity with lidocaine

Answer 16

depression/sedation, twitching, seizures THEN cardiovascular signs

Question 17

which has the worst resuscitation rate after toxic dose in dogs

Answer 17

bupivacaine

50/50

Question 18

when do allergic reactions most commonly occur

Answer 18

procaine in Procaine Penicillin G (PPG)

less common with amide anesthetics

Question 19

goals of locl anesthesia

Answer 19

Provides analgesia before, during, and after procedure

May allow decreased dose of systemic drugs (MAC-sparing)

Decreased hypotension and other adverse effects of general anesthesia

Prevents central sensitization

Important part of multimodal anesthesia

Question 20

oder of nerve blockade

Answer 20

B fibers

A-δ and C fibers

A-γ

A-β

A-α

Question 21

types of regional anesthesia

Answer 21

• *intravenous regional (IVRA)**
• *peripheral** - individual nerve, plexus, intercostal, paravertebral

central (neuraxial) - epidural, spinal

Question 22

bier block

Answer 22

intravenous regional anesthesia

tourniquet placed→local anesthetic injected into peripheral vein→released into systemic circulation when tourniquet removed (Lidocaine only)

limit procedure: 60-90 min

Question 23

T/F epidural anesthesia and spinal anesthesia are the same thing

Answer 23

False

Epidural - space between dura and vertebrae

spinal - space between dura and spinal cord, containing CSF

Question 24

epidural contraindications

Answer 24

CHINAS

coagulopathy, hypovolemia, infection at injection site, neoplasia at injection site, anatomy, sepsis

Question 25

main adverse effect

Answer 25

hypotension

block of sympathetic trunk → decreased vascular tone

Question 26

tools for local anesthesia

Answer 26

palpation

nerve locator

ultrasound