Farm Animal Nerve Blocks

Question 1

How common is use of local anaesthesia in farm animals?

Answer 1

Very - most surgeries are done standing using nerve blocks
○ Flank surgery
○ Foot surgery
○ Eye surgery
○ Teat surgery
○ Perineal surgery Perineal surgery

Question 2

What blocks could you use for flank surgery?

Answer 2

Line block
Inverted L block
Paravertebral block

Question 3

How would you carry out a line block?

Answer 3

• 18g 1.5 needle
• Infiltrate at various depths
• Skin and muscle layers
• All the way down incision site
• Repeated needle sticks on either side
• Lots of adrenaline around incision site is not ideal
  (Farm LAs come infused with adrenaline)

Question 4

How would you carry out an inverted L block?

Answer 4

(7 block)
* Trying to block nerves that supply flank
* 18g 1.5 needle
* Infiltrate at various depths in 7 shape around incision site
* Skin and muscle layers

Question 5

How would you carry out a paravertebral block?

Answer 5

Better option than line and 7 block
* Better option of the 3
* Same nerves but closer to outflow from spine
○ T13
○ L1
○ L2
* 6th lumbar transverse process is small and hidden behind tuber coxae
* Inject long spinal needle down and hit transvers process
* Walk needle forward off cranial edge of transverse process
○ Inject deep and superficial
Cranial to L1 = block T13
Back of L1 = block L1
Back of L2 = L2
* Manage to anesthetise peritoneum

Question 6

What blocks would you use for foot surgery?

Answer 6

Local infiltration
Ring block
IVRA

Question 7

How would you carry out a local infiltration block?

Answer 7

Simplest option
Used for removing masses when nerve supply appears to be infiltrating around
Not sufficient for digit amputation

Question 8

How would you carry out a ‘ring’ block?

Answer 8

• Medication of local infiltration
  
  • Infiltrate circumferentially around top of hoof
  • Varying depths of injection
    Not always effective

Question 9

How would you carry out IVRA

Answer 9

Intravenous Regional Anaesthesia
Same as in SA
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
Diffuses to have regional anaesthesia

Question 10

What nerve blocks would you use for eye surgery?

Answer 10

Local infiltration ‘ring’ block
Retrobulbar block
Peterson block
Auricopalpebral block

Question 11

How would you carry out a local infiltration ‘ring’ block for eye surgery

Answer 11

Used for eye lid surgery
Inject around periphery of eyelids
Animal will till blink - this only blocks sensory
Use in combo with auriculopalpebral block

Question 12

How would you carry out a retrobulbar block?

Answer 12

Used in enucleation - anaesthetises optic nerve
Curved needle around globe

Question 13

What is a Peterson block?

Answer 13

Produces anesthesia of the eye and orbit
Immobilization of the globe
Produces almost complete anesthesia of the lateral aspect of the head except for the eyelids
Spinal needle directed from the notch between the zygomatic arch and supraorbital bone toward the back of the eye
Direct needle straight in until the mandibular ramus is touched
Redirect the needle toward the back of the globe

Question 14

What is an auricopalpebral block?

Answer 14

Motor block only, use in combination with local infiltration ring
Prevents blinking
Inject subcut at crest of rostral zygomatic arch
(branch of facial nerve)

Question 15

What nerve blocks can be used for teat surgery?

Answer 15

Ring block around teat
IVRA - tourniquet at top of teat
Paravertebral/epidural - can’t fully rely on this
Local infiltration for mass removal

Question 16

How do you perform a paravertebral or epidural block?

Answer 16

• Caudal paravertebral - Just L3
  ○ Anesthetises front 2 teats
  
  • Epidural
    ○ Anaesthetises back 2 teats
    ○ Sacrococcygeal space

Question 17

What nerve block would you use for perineal surgery?

Answer 17

Caudal epidural
Between 1st and 2nd coccygeal vertebrae