MSAT: Bovine Med Flashcards
What is the Cornual Block?
- The horn and skin around the horn is innervated by the cornual branch of the ophthalmic division of the trigerminal nerve. (Sensory)
It runs below the front crest to the base of the horn.
It is superficial: Only covered by skin and thin layer of the frontalis muscle.
Halfway between the lateral canthus of the eye and base of the horn
–> 2.5cm below the base of the horn bud
NOTE: The corneal artery and vein are close to the site of the block.
Method:
1. Restrain animal with halter
2. Clean injection site with chlorhexidine swabs
3. Injection is made under the skin at 30 degree angle directed towards the horn.
4. Draw back plunger to make sure needle is not intravascular
5. Inject 5-10mL of anaesthetic solution in an arc below the edge of the frontal bone
6. Massage injection site to disperse the anaesthetic solution
Purpose: Dehorning/debudding, horn injuries
Needle: 18-20 1-1.5”, 10-20mL syringe
Volume: 5-10mL 2% lignocaine
Onset: 5-10 minutes
Duration: Drooping of the upper lid.
What is the auriculopalpebral nerve block?
Runs from the base of the ear along the dorsal border of the zygomatic arch
Past and Ventral of the eye
*Halfway between lateral canthus and base of the ear
Method:
- Restrain animal with halter
- Clean injection site with chlorhexidine swabs
- Insert needle in front of base of ear at the end of zygomatic arch.
Advanced until it lies at the dorsal border of the arch
- Deposit 10-15mL of anaesthetic to the site
Purpose: Examine eyeball: used to keep the eye open. For surgery of the orbit.
Reduce eyeball movement before Peterson’s
May be used in combination with topical anaesthetic to remove foreign bodies from the cornea or conjunctival sac
For injecting medication into the bulbar subconjunctiva
*IT ONLS BLOCKS MOTOR FUNCTION. And only effects lower eyelid.
Line block of upper eyelid separately may be needed
Needle: 18-20G 1-1.5” 10-20mL syringe 2% lignocaine
Volume: 5-10mL
Onset: 5-10 minutes
Check: Drooping of eyelid
What is the Peterson Eye block?
Desensitises the cranial nerves (occulomotor, trochlea, abducens and trigerminal). Sensory + motor function for all structures of the eye EXCEPT the eye lids.
Place needle in the notch formed by the supraorbital process cranially, the zygomatic arch ventrally and the coronoid process caudally.
Where supraorbital process joins the zygomatic arch
Method:
1. Restrain + Clean
2. Inject 5mL of anaesthetic into the notch using 20-21 G 1” needle
3. Place a 18-9 G 4” spinal needle into the anaesthetised area as far rostrally and ventrally as possible
Insert needle horizontal and slightly caudal until it hits anterior edge of the coronoid process of the mandible. (2.5-5cm below skin)
Needle is gently manipulated rostrally until it “walks” off the anterior edge of the coronoid process.
4. Continue advancing the needle until it strikes the bony orbit of the eye. (7.5-10cm depth)
Draw back syringe to ensure that the ventral maxillary artery has not been penetrated.
5. Inject 30-40mL of local anaesthetic solution at, above, below and cranially to the area around the orbital foramen
–> Inject as you pull out. Redirect and go in again (make little pockets0
Purpose: Examine/proptose eyeball, eye surgery. For traumatic injuries + neoplastic lesions.
Needle: 20-21 G 1” needle, 5-10mL syringe
18-19 4” spinal needle, 30mL syringe
25-35mL 2% lignocaine
Onset - 5-10 minutes
Check: mild proptosis, mydriasis, no corneal block
What is the retrobulbar/4 point block
Motor + sensory anaesthesia
Method:
1. Restrain with halter
2. Inject through the eyelids, both dorsally and ventrally. At medial and lateral canthi
3. Slightly curved, 18-19 G 4” spinal needle is directed towards apex of the orbit. Behind the globe.
Inject 40mL of anaestehtic solution, divide 10 mL per site
If not adequately blocked: a line of block of the upper and lower eyelids using 20-21 G 1.5” long needle from lateral canthus to medial canthus. Using 5.0mL of anaesthetic solution per eyelid.
Purpose: Eye enucleation
Needle: Curved 18-19 G 4” spinal needle
Volume: 40-60mL, 10-15 per site
Onset: 5-10 minutes
Check: Mild proptosis, mydriasis, no corneal block
How to do intravenous regional anaesthesia of the distal limb?
Sensory and Motor block
Most commonly the cephalic vein on the metacarpus OR
lateral saphenous vein on the metatarsus
Alternatives:
- Dorsal common digital vein III
- Any venous plexus on the dorsal or palmar/planter aspect of the limb. Exactly in the midline and 2-3cm below the fetlock joint. (At level of proximal interphalangeal joint)
- Administer anaesthetic solution close to surgical site.
- Administer into one vein to provide anaesthesia of the entire area distal to the tourniquet
Sensory and motor
Method:
- Affected limb restrained
- Tourniquet placed distal to the carpus in the forelimb or tarsus in the hindlimb.
–> Consists of stout rubber tubing, a ‘bungy’ or narrow strip of inner tube
- Engorged veins palpated distal to the tourniquet. Clip and scrub area
- 20-30mL of 2% lignocaine solution is injected into the vein
Onset: 5-10 minutes, lasts as long as tourniquet is in place
After release: 5-10 minutes before normal sensation + motor function
Purpose: For digital surgical procedures
How to lift the leg for foot blocks?
- Put belly strap
- Clip one side, hooks on the outside but the ropes go on the inside
- Throw rope to the other side
- Clip on other side - Lift the leg
- Put the strap with 2 metal things on top
- Big head to the top –> Clip
- Have someone give tail jack on SAME SIDE OF LEG, person tying stand on opposite side and reaches over so no kick.
- Put strap over top of hock
- Clippy things clip onto thing above hock
- Pull - Tying off
- 3 throws
- Tie –> Loop around then put end through loop - Tornique: Tie just below tarsus
How to interdigital nerve block?
Only two sites to anesthetise the interdigital region and axial aspects of the claws of both fore and hind limbs.
SITE 1: dorsal midline, 2-3cm distal to fetlock joint and 2-25.cm deep
10mL of 2% lignocaine injected while withdrawing needle
SITE 2: Palmar/plantar midline, 2-3cm distal to accessory digits and 2-25cm deep, 10mL injected
*plantar midline straight down
- Need to see blood
Purpose: removal of interdigital hyperplasia and painful procedures of the interdigitial space, includes trimming of axial wall cracks
Needle: 19-20G, 1-1.5” 10-20mL syringe
20mL 2% lignocaine
Onset: 5-10 minutes
Duration 1: hour
Note: Not appropriate for abaxial aspects of the digits thus not for claw amputation
Lateral Digital Nerve Block:
- Press Fetlock nubs down
- Can see it
- Stab into blood
How to do an epidural nerve block?
Used for obstetric manipulations, surgical procedures involving the tail, perineum, anus, rectum, vulva and vagina. Caudal aspects of the thighs
Densities all of these but without loss of motor control of the hind limbs.
- The epidural nerve block results from deposition of anaesthesia between the dura mater and periosteum of the spinal cord (epidural soace)
Desensitises the caudal nerve roots.
Common sites:
- Sacrococcygeal (high caudal epidural block)
- Intercoccygeal (low caudal epidural block)
- Lumbosacral space (lumbar epidural block) infrequently used
Locate:
Pump tail up and down to see articulation
Caudal to the sacrum: First intercoccygeal space
Space is larger and easier to detect
Sacrococcygeal space: virtually immobile
Material:
- 19-20 G x 1-1.5” needle, 5-10mL syringe
4-6mL 2% lignocaine
Method:
1. Restrain area + clip selected area over base of the tail. Scrub
2. Needle is inserted perpendicular to the skin surface, in the midline
3. Place a few drops of anaesthetic solution into the epidural space
4. Advance the needle (direct it slightly cranially), until the solution is drawn into the epidural space by negative pressure. (Hanging drop technique)
5. Slowly inject 4-6mL of local anaesthetic. Provides caudal anaesthesia without causing hindlimb ataxia/paralysis
*Should be little resistance to injection.
Onset: 1-2 minutes, duration: 1-2 hours
Another method:
- Hear air being sucked in as needle enters epidural space
- Lack of resistance technique: Minimal resistance following proper placement of needle in epidural space. Can draw in air to see if it will go down easily.
*aspirate or allow a few seconds for bleeding before epidural injection as to not inject into venous sinus or subarachnoid space
Infection at injection site: Permanent paralysis of tail, perineal skin and udder.
Sign of success: Tail is floppy. Sensory innervation is lost. Anal sphincter relaxes
What is inverted L-block
Motor + Sensory?
Spinal nerves innervating the skin + muscles of the flank run in a slightly caudo-ventral direction.
Inverted L is a Non-specific regional block
For anaesthesia of paralumbar fossa + abdominal wall: Local anaesthetic solution is deposited in an inverted ‘L’. Runs caudal from last 13th rib to ventral to the transverse processes of lumbar vertebrae.
*Block encloses the incision site as all nerves entering the area are blocked.
Material:
18-19 G x 1.5” needle, 20mL syringe or vaccinating gun (5mL)
80-100mL 2% lignocaine
Method:
1.Restrain, locate landmarks, clip _ scrub
2. Deposit a bleb of local anaesthetic solution in the corner of the inverted ‘L’. Caudal to the last rib and ventral to the transverse process of the 1st lumbar vertebrae
3. Advance the full length of the needle under the skin in a caudal direction, while injecting small amounts of anaesthetic solution as the needle is advanced.
4. Move along the line just ventral to transverse processes of the lumbar vertebrae. Reinsert needle at the end of the first bleb.
Continue infiltrating small amounts of anaesthetic solution along the dorsal branch of the inverted ‘L’ until desired length is reached
5. Return to the starting point and continue parallel just caudal to the last rib.
To infiltrate into deeper tissues: More anaesthetic solution injected along the previously anaesthetised ‘L’.
This time, needle is inserted perpendicular to skin to advance to deeper tissues
Success: Complete anaesthesia of the area ventral and caudal to the inverted ‘L’
How to do a paravertebral block?
Motor + Sensory?
Allows for complete desensitisation of abdominal wall + peritoneum
Used for surgery of the GIT: Rumenotomy, abomasopexy, c-section
Spinal nerves: T13, L1 & L2 innervate an area bound by the last 13th rib, tuber coxae + the transverse processes of the first 3 lumbar vertebrae
Innervates skin, muscle + peritoneum
Landmarks:
- First palpable transverse process in front of tuber coxae is LT5. Count forwards from LT5 to find LT2
Fat cows: LT1 not easily palpable
To find it measure distance between LT2 to LT3, same as LT2 to LT1.
Injections:
Inject 5-6cm away from the dorsal midline
- to block T13 the injection point is the cranial edge of L1
- to block L1 –> Caudal edge of L1
- to block L2 –> Caudal edge of L2
Materials:
- 18-19 G 1.5” needle, 10-20mL syringe
18 G 4” spinal needle, 20mL syrine
80mL 2% lignocaine
Method:
1. Restrained, clip + scrub
2. Locate landmarks, Mark needle insertion points + scrub again
3. Using 18-19 G needle make a 2mL bleb of local anaesthetic solution at caudal edge of LT2. 5-6cm away from dorsal midline
4. Redirect needle so that it is perpendicular to LT2 and inject a further 3mL into underlying fascia + muscle
5. Remove needle and insert spinal needle into desensitised area perpendicular to transverse process. Inject small amounts of anaesthetic solution as the needle is advanced
6. When needle hits caudal edge of LT2, withdraw slightly and walk off the caudal edge and perforate the intertransverse ligament. Should not be possible to aspirate.
7. Inject 10mL of solution below the ligament
8. Withraw the needle 1cm and inject a further 5mL above the ligament.
9. Repeat process to block L1 by injecting off caudal edge of L1
10. Repeat to block T13 by injecting cranial edge of L1
Onset 5-10 minutes
Duration 90 minutes
Signs of success:
- Increased temp of the skin over the flank due to vasodilation (over injected side)
- Analgesia of the skin, muscles + peritoneum of the paralumbar fossa
- Scoliosis of the spin towards desensitised side due to paralysis of paravertebral muscle
