Local Anesthesia

Question 1

Onset and duration of lidocaine

Answer 1

Onset: 3-5 minutes
Duration: 1-2h

Question 2

T/F: Lidocaine has a longer duration than bupivacaine

Answer 2

False - bupivacaine is 4-6h, lidocaine is 1-2h

Question 3

__________ is the most important motor block when performing an ocular exam

Answer 3

Auriculopalpebral

Question 4

When is it helpful to add in sensory blocks to the eye?

Answer 4

Minor surgical eyelid procedures so they can’t feel us suturing them up

Question 5

Why is it important to use a short acting drug (lidocaine) when blocking motor innervation to the eyelid?

Answer 5

Need them to blind to keep tear film - don’t want anesthetized for too long so wouldn’t use something like bupivacaine

Question 6

What block will block most sensory innervation to the upper eyelid?

Answer 6

Supraorbital - inject in and over supraorbital foramen

Question 7

Aside from the supraorbital nerve, what other nerves can be blocked to inhibit sensory innervation?

Answer 7

Lacrimal - temporal canthus, 25% upper lid
Infratrochlear - nasal canthus
Zygomaticofacial - lower lid

Question 8

Infraorbital I provides analgesia to

Answer 8

Upper lip and nose

Question 9

Infraorbital II provides anesthesia to

Answer 9

Teeth to 1st molar, maxillary sinus, roof of nasal cavity, skin to medial canthus

Done by actually threading needle into infraorbital foramen (not well tolerated by standing horses)

Question 10

Blocking maxillary nerve provides anesthesia to

Answer 10

All upper teeth, sinuses, and nasal cavity

Question 11

Mandibular block will anesthetize

Answer 11

All mandibular structures, lateral canthus, mandibular cheek teeth

Question 12

You want to block just the lower incisors for a dental procedure. What block can you do?

Answer 12

Mental II

Question 13

Name some indications for an epidural

Answer 13

• Procedures involving rectum, vagina, perineum, urethra, and bladder
• Obstetric manipulations
• Analgesia of stifles and hocks
• Intraoperative

Question 14

When might an epidural be contraindicated?

Answer 14

• Infection @ puncture site
• Sepsis
• Uncorrected hypovolemia, anticoagulation
• Anatomic abnormalities

Question 15

Describe the location of the epidural space

Answer 15

Within spinal canal outside the visceral layer of the dura matter
Not the subarachnoid space

Question 16

T/F: lumbosacral epidurals are more commonly used in horses than caudal

Answer 16

False - Special equipment and very strict aseptic technique required for LS. Caudal is more common b/c it is simpler and doesn’t require any special equipment

Question 17

Define the landmarks for LS subarachnoid

Answer 17

1-2cm caudal to a line drawn from the cranial edge of tuber sacral and dorsal midline

Question 18

Define landmarks for caudal epidural

Answer 18

Palpate Co1-Co2 as the first midline depression caudal to the sacrum
First movable coccygeal articulation when the tail is raised and lowered

Question 19

When might you consider an epidural catheter?

Answer 19

Repeat dosing
Very painful conditions that require continuous epidural analgesia

Question 20

What can you combine with local anesthesia to prolong analgesia?

Answer 20

Alpha-2 agonists

Biggest consideration is that you will see systemic effects

Question 21

Why might opioids be used in an epidural?

Answer 21

Inhibition of pain transmission
Minimal motor nerve blockade, minimal dose requirements, few side effects

Question 22

T/F: You can use both PF or regular morphine in horses.

Answer 22

True - PF is better for repeated administration, but regular morphine is good for one time use

PF is more expensive and requires a larger volume