Locoregional Nerve Blocks- Large Animal Flashcards
What species are auriculopalpebral blocks performed in?
Equine and bovine
T/F: Auriculopalpebral blocks are sensory blocks ONLY.
False- only motor blocks, eyelids and cornea remain sensitive
Where is the injection placed for an auriculopalpebral block in a horse?
Most dorsal point of the zygomatic arch
Which muscle is paralyzed with auriculopalpebral blocks?
Obicularis oculi
What does the supraorbital block effect?
Sensory to middle 2/3 of upper eyelid and palpebral motor
Where is a supraorbital block injection placed?
Supraorbital foramen
What is a supraorbital block used for?
Placement of sub-palpebral lavage catheter
Is an equine retrobulbar block the same procedure as in small animal?
Yes
Where is an infraorbital block placed?
At the exit of the infraorbital canal
What area does an infraorbital block effect?
Exit of canal: Sensory to the upper lip and nose
Inside canal: teeth rostral to first molar, maxillary sinus, roof of nasal cavity
What does a mental nerve block do?
Desensitize the lower lip
Why are caudal epidurals used in horses?
Because you don’t want to lose hindlimb motor function.
What are some indications for a caudal epidural?
- Control of rectal tenesmus
- Obstetric procedures
- Tail amputation, rectovaginal fistura repairs
- Hindlimb procedures and pain
Where are caudal epidurals placed?
First coccygeal space- first movable joint when tail is manipulated
Should LAs be used in equine epidurals?
They can, but must limit spread cranially
Lidocaine 2% 6-8mL usually sufficient in an adult horse
Can Alpha-2 agonists be used in equine epidurals?
Yes, more commonly used (xylazine and detomidine)
May cause systemic effects
Can morphine be used in equine epidurals?
Yes- provides analgesia without risk of motor junction impairment
Often mixed with detomidine
Should epidural catheters be used with local anesthetics in horses?
No- motor blockade
How much lidocaine should be injected into the testicle for a castration?
Enough so that it feels firm- usually around 20mL
Does a testicular injection provide cutaneous analgesia?
No
When is inta-articular morphine typically used?
Analgesia and anti-inflammatory post-arthroscopy
What is a peterson block?
Similar block as retrobulbar but is more difficult to perform.
What nerves does a peterson block effect?
Oculomotor, trochlear, abducens, trigeminal
T/F: Both retrobulbar and peterson blocks prevent blinking for several hours.
True- eyes should be lubricated and animals should be kept out of the sun/dust/wind until motor function returns
Which nerves should be blocked for dehorning in cattle and goats?
Cattle- cornual branch of zygomaticotemporal
Goats- cornual branch of zygomaticotemporal and cornual branch of intratrochlear
What are the techniques for a ruminant flank laparotomy?
Infiltration- Line block or inverted L block
Regional- proximal or distal paravertebral
What is a line block?
Injecting LA subcutaneously along the incision line
What is an inverted L block?
Injections of idocaine into the area dorsocaudal to the last rib and ventrolateral to lumber transverse processes
Is the LA injected along the incision line in an inverted L block?
No
what are some other names for a proximal paravertebral thoracolumbar block?
Farquharson, hall, or cambridge technique
Which nerves are effected in a proximal paravertebral thoracolumbar block?
Dorsal and ventral branches of T13-L2
Where is the injection placed in a proximal paravertebral thoracolumbar block?
3-5cm from dorsal midline
What are signs of a successful proximal paravertebral thoracolumbar blockade?
- Analgesia of skin
- Increase skint temp
- Spinal scoliosis towards desensitized side
What are some disadvantages of a proximal paravertebral thoracolumbar block?
- Technically difficult
- Scoliosis may impair incision closure
- Risk of penetrating great vessels
- Loss of motor control if LA migrates to femoral
Which nerves are effected by a distal paravertebral thoracolumbar block?
Dorsal and ventral branches of T13-L2 also transverse of L1, L2, and L4
What are the advantages of a distal paravertebral thoracolumbar block versus proximal?
Lack of scoliosis and less risk of damaging blood vessels
What are the disadvantages of a distal paravertebral thoracolumbar block?
Larger amount of local anesthetic and may be less effective
What kinds of animals are lumbosacral epidurals used in?
Immature cattle, small ruminants, camelids, and pigs
What drugs are used in lumbosacral epidurals for large animals?
Alpha-2 agonists
T/F: Local anesthesia can be done on the teat to treat lacerations or other injuries.
True- ring blocks, inverted IV blocks, teat cistern infusion, IVRA
Which nerves are blocked in order to anesthetize the udder?
Paravertebral block of L1-L3 or high caudal/LS epidural
What kind of blocks are done to anesthetize the feet?
Ring block or IVRA
