Local Anesthetic Agents 3 Flashcards
What are 5 examples of blocks that can be used for local anesthesia of the flank?
- Inverted L block
- Incisional block
- Epidural
- Proximal paravertebral block
- Distal paravertebral block
The objective of a proximal paravertebral block is to block which 3 nerves?
T13, L1, L2
Where is the site of needle insertion for a proximal vertebral block?
5 cm from midline and transversely in line between 2 dorsal spinous processes
What gauge and length needle is used for a proximal paravertebral block?
- 16 or 18 g
- 12-15 cm
To block the ventral branch in a proximal paravertebral block, how much local anesthetic is given?
To block the dorsal branch?
- 15 mL below intertransverse ligament
- 5 mL above ligament & leveled with dorsal surface of transverse processes
What are 4 advantages of a proximal block of infiltrative analgesia?
- Wide & uniform area of analgesia & muscle relaxation
- Incision site not disrupted
- Infiltrative block may take 45 min to desensitize area
- Faster technique
What are 4 disadvantages of a proximal block of infiltrative analgesia?
- Technically difficult (obese cattle)
- Scoliosis dye to back muscle paralysis (makes closure more difficult)
- Vital structures (aorta & vena cava)
- Loss of motor control in pelvic limb (caudal migration)
How do you find the site to give the first injection in a distal paravertebral block?
- Find last rib then vertebrae just behind it.
Which 3 nerves are done in a distal paravertebral block?
Which nerve is purposefully skipped?
- L1, L2, L4
- L3
How much local anesthetic is given in a distal paravertebral block?
How is it given?
- 10-20 mls 2% lidocaine then withdraw needle short distance dorsal & caudal to transverse process & inject additional 5 ml
- injected in a fan-shaped infiltration ventral to each process.
What are 4 advantages of a distal paravertebral block?
- Lack of scoliosis
- Lack of risk of penetrating major blood vessels
- Minimal weakness in pelvic limb
- Minimal ataxia
What are 2 disadvantages of a distal paravertebral block?
- Larger doses of anesthetic
- Variations in efficiency (nerves may follow variable anatomic pathways)
What are 4 examples of equine cranial blocks?
- Supraorbital
- Auriculopalpebral
- Infraorbital
- Mental
Infraorbital nerve blocks provide anesthesia where?
What are 2 examples of indications for this?
- Anesthesia of upper lip & nose
- Suturing of nasal laceration, placement of nose ring in cattle
Where does an infraorbital nerve block desensitize?
Entire anterior half of face from foramen rostrally.
How can you find the location to give an infraorbital nerve block in a horse?
Feel for the bony lip of the infraorbital foramen.
Where is the location of the infraorbital foramen?
1/2 the distance & 2.5 cm dorsal to a line connecting the nasomaxillary notch & rostral end of the facial crest.
Which muscle needs to be displaced when giving an infraorbital nerve block?
Levator nasolabialis muscle
Where is the injection given for an infraorbital nerve block?
How much anesthetic is used for a horse?
Perineurally at bony lip of infraorbital foramen using 10 mL of local anesthetic.
How do you locate the infraorbital foramen in cattle?
Rostral to facial tuberosity on a line extending from nasomaxillary notch to 2nd upper premolar
How much local anesthetic is given in cattle?
20-30 mL
What are 4 examples of what auriculopalpebral blocks are used for in horses and cattle?
- Examination of eye
- Treatment of eye
- Foreign body removal
- Minor ocular surgery
The blockade of the auriculopalpebral nerve causes what?
Akinesia of eyelids (loss of voluntary movement)
Does an auriculopalpebral block desensitize the eyelids?
No, only paralyzes them.
Where is an auriculopalpebral block given in a horse?
2.5 cm, 20 g needle inserted about 2 cm ventral to most dorsal point of zygomatic arch.
How much local anesthetic is given in an auriculopalpebral block in a horse?
2.5 mL into dorsal border & another 2.5 mL as needle is withdrawn.
Where is an auriculopalpebral block given in cattle?
Along dorsal edge of zygomatic arch. Feel groove about 5-7 cm caudal to notch formed by zygomatic arch & temporal process of malar.
How much local anesthetic is given in an auriculopalpebral block in cattle?
5 mL
What is the most commonly desensitized nerve in the head of a horse?
Supraorbital nerve
What are 2 indications for a supraorbital nerve block?
- Ophthalmic examination
- Anesthesia to upper eyelid
What are 2 indications for Peterson & Retrobulbar blocks?
- Enucleation of eyeball
- Removal of tumors from eye/eyelids
Where is the point of injection for a Peterson technique block?
Notch formed by supraorbital process cranially, zygomatic arch ventrally, coronoid process of mandible caudally.
What size needle is used for a Peterson technique block?
10 or 12 cm, 18 g
What are 4 nerves blocked in a Peterson technique block?
- Oculomotor
- Trochlear
- Abducens
- Trigeminal
What other type of nerve block must be done with a Peterson technique block?
Why?
- Auriculopalpebral block
- Paralyze the eyelids
What are 2 potential complications of a Peterson technique block?
- Penetration of turbinates
- Injection into optic nerve meninges
What are the sites of needle placement in a retrobulbar block?
Upper & lower lids or lateral & medial canthi. Deflect globe, insert into orbital apex until wall of bony orbit is felt.
How is local anesthetic administered in a retrobulbar block?
Inject small increments as needle is advanced.
What are 4 potential complications of a retrobulbar block?
- Penetration of globe
- Damage to optic nerve
- Injections into meninges
- Oculocardiac reflex
What are 3 advantages to the Peterson technique block?
- Safer & more effective
- Less edema & inflammation
- Minimized risk of orbital hemorrhage, penetration of globe, damage to optic nerve, risk of injection into optic
What are 2 disadvantages to the Peterson technique block?
- Requires more skill
- Does not paralyze eyelids without additional nerve block
How many nerves are blocked in a cornual block in cattle?
In goats?
- One
- Two
Which nerve is blocked in both cattle and goats in a cornual nerve block?
Cornual branch of zygomaticotemporal
Which nerve is blocked in goats but not in cattle in a cornual nerve block?
Cornual branch of infratrochlear
An intravenous regional block is also known as what?
Bier block
Can an intravenous regional block be used in a front leg, back leg or both?
Both
Intravenous regional blocks are good for procedures not expected to take longer than what amount of time?
What are 2 examples of procedures?
- 90 minutes
- Biopsies, small mass removals
How is an intravenous regional block given?
Injecting local anesthetic IV after isolating the limb from rest of body by a tourniquet.
How long is an intravenous regional block present?
As long as tourniquet is present.
How does the local anesthetic get into the surrounding tissue with an intravenous regional block?
Diffuses through blood vessels into surrounding tissue.
What should be given first before administering an intravenous regional block?
Sedation
Where is the tourniquet placed?
Proximal or distal to elbow
When should the tourniquet be removed and how?
Slowly within 90 minutes
What are 2 vessels that can be used in the front leg of cattle for an intravenous regional block?
- Dorsal metacarpal vein
- Radial vein
Which vessel is used in the hind leg of cattle for an intravenous regional block?
Saphenous vein
What is a block that may be used with castration?
Where is it administered?
- Intratesticular block
- Directly into testicle
What does not get desensitized with an intratesticular block?
Scrotum
