Small Animal Nerve Blocks

Question 1

What is important to consider about using local anaesthetics?

Answer 1

Narrow therapeutic window
Easy to overdose
Need to be careful when doing multiple blocks

Question 2

Where is local anaesthetic injected?

Answer 2

Close proximity to nerves
NOT in blood vessels

Question 3

What local anaesthetics are used in small animals?

Answer 3

Lidocaine
Bupivacaine - not licensed but longer duration

Question 4

How do local anaesthetics work?

Answer 4

Interact with sodium channels - inhibit influx of sodium ions, preventing AP propagation

Question 5

How can local anaesthetic be administered?

Answer 5

Topically - skin, eyes, mucous membranes
Injection
Regional nerve blocks - epidural

Question 6

What are some commonly used blocks in SA medicine?

Answer 6

Intercostal block
Peribulbar block
Epidural
Intratesticular
Brachial plexus block
Ring block
IVRA
RUMM block

Question 7

What is an intercostal block and when is it used?

Answer 7

Walk needle off the back of a rib, aspirate then inject
Useful for rib fractures

Question 8

What is a peribulbar block and when is it used?

Answer 8

Needle inserted just above eye
Blocks the ciliary nerves, CN III and VI,
Does not block optic nerve
Used for eye surgery

Question 9

What is a retrobulbar block and when is it used?

Answer 9

Includes desensitisation of optic nerve
Used for enucleation surgery
Use curved needle torch around globe of eye

Question 10

What is an epidural and when is it used?

Answer 10

Inject between L7 and S1 into epidural space
Used in tail amputation

Question 11

What is a brachial plexus block and when is it used?

Answer 11

Provides analgesia to distal of elbow
Inject medial to shoulder joint, parallel to vertebral column towards costo-chondral junction

Question 12

What is a Ring block and when is its used?

Answer 12

Simple generic anaesthesia method
inject LA in horizontal plane around area to anaesthetise
Can be used in many surgeries
Not always effective

Question 13

What is IVRA and when is it useful?

Answer 13

Intravenous Regional Anaesthesia
Cannula in vein of distal limb
Desanguinate limb
inflate cuff around proximal part of limb (tourniquet)
Inject LA into cannula
ONLY use lidocaine
Used for distal limb surgery

Question 14

What is a RUMM block?

Answer 14

Radial, Ulnar, Medial Musculocutaneous Block
Inject proximal to elbow on lateral and medial side of humerus
Useful for distal limb surgery

Question 15

What is a soaker catheter?

Answer 15

Similar to cannula but longer and fenestrated
Insert under skin and inject LA
Leaks out over long period of time - regional anaesthesia

Question 16

How can you improve accuracy when injecting LA?

Answer 16

Use nerve locator
Use ultrasound probe - can visualise needle

Question 17

How does a nerve locator work?

Answer 17

Hollow needle through which a current is passed
If needle is in proximity to a nerve it causes muscle to twitch
Bigger the twitch the closer to the nerve

Question 18

IVRA Prodecure

Answer 18

1. Prep leg
   
   2. Place cannula in vein in distal limb
   3. Densanguinate limb
      ○ Wrap vet wrap from toes upwards
   4. Inflate cuff around proximal part of limb
   5. Can inject LA into cannula
      ○ Must be lidocaine
   6. Diffuses to have regional anaesthesia