Exam 2 Local Anesthetics

Question 1

Order of Nerve blockade

Answer 1

Generally, smaller diameter fibers and those with less myelination are blocked first

1st= sympathetic, 2nd= pain

Exception: Brachial plexus block

Question 2

Which fibers are associted with pain?

Answer 2

A-δ(delta) and C fibers

Question 3

Structure activity of local anesthetics

Answer 3

All are weak bases –pK~7.7 –9

Question 4

Potency, onset, and duration are affected by 3 things

Answer 4

1) pK -> low pK = faster onset
2) Protein binding -> high protein binding -> longer DOA
3) Lipid solubility -> high lipid solubility -> higher potency

Question 5

Which amide drug has a fast onset and ONLY local anesthetic that may be given IV or used for intravenous regional anesthesia?

Answer 5

Lidocaine

Question 6

Which amide drug has analgesic effect?

Answer 6

Lidocaine

Question 7

Which amide drug has the HIGHEST cardiovascular toxicity?

Answer 7

Bupivacaine

Question 8

Which amide drug is used for nerve block, intra-articular (common in large animal)?

Answer 8

Mepivacaine

Question 9

Where is the fastest absorption site?

Answer 9

Fastest absorption with intercostal blocks

-Highest peak plasma concentration

Question 10

Which ester drug has the fastest onset?

Answer 10

Procaine

Question 11

____ should be used for epidurals and spinal anesthesia

Answer 11

Preservative-free versions

Question 12

With ____, first sign is cardiovascular collapse -> death

Answer 12

Bupivacaine

Question 13

Spinal ______ seems to be the worst neurotoxicity

Answer 13

Spinal Lidocaine

Question 14

_____ used for equine lameness diagnosis IA

Answer 14

Mepivacaine

Question 15

What to avoid when treatment of arrest secondary to LA?

Answer 15

Avoid lidocaine, Ca-channel blockers, Beta blockers, vasopressin

Question 16

Allergic reactions:

most common occurs with?

treat with?

Answer 16

most common occurs with procaine

treat with epinephrine

Question 17

Where does the spinal cord end:
Dogs -> ?
Cats -> ?
Horses, ruminants, pigs -> ?

Answer 17

Dogs -> L6-L7
Cats -> L7-S3
Horses, ruminants, pigs -> mid-sacrum

Question 18

Epidural contraindications

Answer 18

(CHINAS)
Coagulopathy
Hypovolemia
Infection at injection site
Neoplasia at injection site
Anatomy (inability to palpate landmarks)
Sepsis

Question 19

Main adverse effect of local anesthetic

Answer 19

Hypotension
-Block of sympathetic trunk -> decreased vascular tone

Question 20

Which of the following treatments would be most appropriate for local anesthetic toxicity?

a) Lidocaine
b) Propanolol
c) Lipid emulsion
d) Vasopressin
e) Diltiazem

Answer 20

c) Lipid emulsion