Local anaesthetics and dental blocks

Question 1

Describe the mechanism of action of local anaesthetics

Answer 1

Mechanism of action – ionised charged form interacts with receptors
The receptor for LA s is located within the pore of the Na+ channel close to the cytoplasm and only the ionised, charged form of the LA can interact with Rc

Question 2

What are the different types of LAs?

Answer 2

amides or esters
Amides broken down by liver e.g., lidocaine
esters broken down by plasma cholinesterases e.g., procaine

Question 3

Give examples of different local anaesthetics?

Answer 3

Procaine
Lidocaine
Bupivacaine
Mepivacaine
Proparacaine

Question 4

Fill in the table

Answer 4

Question 5

Give examples of how local anaesthetics can be given in practice

Answer 5

Question 6

What can be used to prolong to action of LAs?

Answer 6

vasoconstrictors (adrenaline)
- can be risky in areas such as digits, teat etc. (loss of blood supply)

Question 7

What LA is given before a canine castration?

Answer 7

Pre-incisional block
Intra-testicular block

Question 8

What are the different ways LA can be given in an ovariohysterectomy?

Answer 8

Direct infiltration of the mesovarium ligament
Lavage of the peritoneal cavity with local anaesthetic
Skin and subcut tissues at incision site also blocked

Question 9

What type of LA is this?

Answer 9

retro bulba anaesthesia

Question 10

What types of LA is shown here?

Answer 10

Lumbosacral (L) & sacrococcygeal (R) epidurals

Question 11

What are the indications of Lumbosacral & sacrococcygeal epidurals?

Answer 11

Tail amputations
Surgeries of the penis or perineal region
Perineal relaxation for puppy/kitten delivery

Question 12

What dental block is being performed here and what area does it provide analgesia for?

Answer 12

Rostral maxillary (infraorbital)
Provides analgesia for rostral maxillary soft tissues (NOT TEETH/BONE)

Question 13

Label these nerves

Answer 13

Question 14

Which nerve innervates the teeth and bone adjacent to the teeth within the maxilla?

Answer 14

Superior alveolar nerve (SAN)

Question 15

What methods are there to block the maxilla?

Answer 15

Caudal maxillary dental block (intra or extra orally)

Question 16

What dental block is being shown here?

Answer 16

Mandibular block

Question 17

What is IVRA?

Answer 17

intra-venous regional analgesia

Question 18

Describe IVRA

Answer 18

Catheter inserted into vein going to foot
De-sanguinate limb with vetwrap
Place tourniquet proximally and tighten
Remove vetwrap
Inject lidocaine into catheter
Remove catheter and prep for surgery

Question 19

What block is this?

Answer 19

Bier block

Question 20

What is the function of a soaker catheter?

Answer 20

Long catheter with small fenestrations to bathe large area in LA

Question 21

How can nerve blocks be done most accurately?

Answer 21

Using a nerve locator

Question 22

In what situation can a LA be given into a vessel?

Answer 22

IV lidocaine (NO ADRENALINE)
- decreases opioid use
- decreases MAC
- avoid in cats

Question 23

What is the benefit of peripheral nerve blocks over epidurals?

Answer 23

reduced risk of urine retention
reduced post-op opioid consumption

Question 24

How is a patient with local anaesthetic toxicity supported?

Answer 24

intra-lipids
support airways
support seizures
identify and support arrhythmias