Exam 1 - Equine Nerve Blocks

Question 1

how can you avoid potential complications associated with nerve blocks?

Answer 1

proper restraint of the horse decreases the likelihood of needle breakage

proper prep of the site - avoid infecting synovial structures

Question 2

when should you use diagnostic anesthesia in an equine lameness case?

Answer 2

to identify painful region when either obvious pathology is lacking or there is more than one lesion present

to direct diagnostics & imaging

Question 3

which medication used for nerve blocks is least safe for joints?

Answer 3

bupivacaine - chondrotoxic

Question 4

how should you prep a patient for a regional nerve block?

Answer 4

quick prep - chlorohex/betadine for 3-5 minutes

removes surface debris

Question 5

what nerves are blocked by a PD block?

Answer 5

palmar/plantar digital nerves

Question 6

how do you place your needle for a PD nerve block when taking into consideration the neurovascular bundle?

Answer 6

vein is most lateral

artery is middle

nerve is medial

Question 7

where are your landmarks for a PD nerve block?

Answer 7

feel for the neurovascular bundle above the hoof cartilages

insert the needle distally about 1cm above the hoof cartilages

Question 8

what structures are reliably anesthetized by a PD block?

Answer 8

navicular bone, navicular bursa, navicular apparatus, DDFT, frog, 1/3-1/2 sole, parts of the PIP/DIP, & skin

Question 9

what is the benefit of performing a midpastern PD block?

Answer 9

allows for desensitization of the entire foot including the PIPJ

Question 10

what nerves are desensitized by an abaxial sesamoid block?

Answer 10

palmar digital nerves at or near the proximal sesamoid bones

Question 11

what structures are anesthetized by the abaxial sesamoid block?

Answer 11

everything in the PD block

DIPJ, PIPJ, distal sesamoidean ligaments, dorsal branches of the suspensory ligament, DDFT, SDFT, & +/- MCP joint

Question 12

what landmarks are used for an abaxial sesamoid block?

Answer 12

palpate the neurovascular bundle at the abaxial border of each proximal sesamoid bone

direct the needle distally at this level

Question 13

if doing a palmar/plantar PD block, what region do you expect to block? what else was potentially blocked?

Answer 13

palmar/plantar 1/3-1/2

most of the foot

Question 14

if doing a palmar/plantar PD block including the dorsal branches, what region do you expect to block? what else was potentially blocked?

Answer 14

from coronary band distal

same as PD

Question 15

if doing a abaxial sesamoid block, what region do you expect to block? what else was potentially blocked?

Answer 15

from proximal pastern distal

complete foot, pastern region, & fetlock joint

Question 16

what nerve block is being done in this photo?

Answer 16

PD nerve block

Question 17

what nerve block is being done in this photo?

Answer 17

abaxial sesamoid block

Question 18

what block is being done in the photo? what are your landmarks?

Answer 18

coffin (DIP) joint

thumbs width above the coronary band & thumbs width off dorsal midline to either side to find a depression adjacent to the extensor tendon where the needle is inserted either medially or laterally angling to the opposite coroner of the foot

Question 19

what is blocked in a DIP joint block?

Answer 19

coffin joint, parts of the coffin bone, collateral ligaments of the coffin joint, impar ligament, & navicular bone

overtime, it diffuses out to block the navicular bursa & caudal port of the foot (coffin bone & soft tissue structures in the heel)

Question 20

what is blocked in a navicular bursa block? what are the landmarks used?

Answer 20

navicular bursa, navicular bone, & caudal portions of the heel

spinal needle is inserted between the heel bulbs parallel to the sole of the foot

Question 21

what is blocked in a PIP block? what are the landmarks used?

Answer 21

pastern, & with time diffuses out & also as a PDN block

find the widest part of the long pastern bone & aim the needle slightly below it

Question 22

what nerves are blocked in a low 4 point? what are the landmarks used?

Answer 22

medial & lateral palmar & palmar metacarpal/metatarsal nerves

immediately distal to the distal ends (buttons) of metacarpal II & IV for the palmar metacarpal/metatarsal nerves & 1cm proximal for the palmar nerves

Question 23

what structures are blocked in a low 4 point?

Answer 23

entire fetlock & all structures distal to it but may miss some skin on the dorsal fetlock

Question 24

what structures are blocked in a high 4 point?

Answer 24

deep structures of the metacarpus & all structures distal to the block with the exception of the origin of the interosseus m.

Question 25

what nerves are blocked in a high 4 point? what are the landmarks used?

Answer 25

medial & lateral palmar & palmar metacarpal/metatarsal nerves same as low 4 point but performed just distal to the carpus

Question 26

what nerves are blocked in a lateral palmar block? what are the landmarks used?

Answer 26

lateral palmar nerve proximal to its deep branch & medial and lateral palmar metacarpal nerves medial to the accessory carpal bone

Question 27

what structures are blocked in a lateral palmar?

Answer 27

origin of the interosseus m. & other deep structures of the palmar metacarpus/metatarsus

Question 28

what nerve block is pictured here?

Answer 28

low 4 point

Question 29

what nerve block is pictured here?

Answer 29

high 4 point

Question 30

what sort of anesthetic agent would you use to perform a lameness exam & why?

Answer 30

mepivicaine - provides moderate duration of activity (~2 hours), rapid onset, ~10 minutes, & relatively non-irritating lidocaine is used if you want it to wear off faster but may be more irritating bupivacaine is used for long lasting blocks - treating laminitis or pain control

Question 31

how would you block out the entire foot?

Answer 31

abaxial sesamoid nerve block - check for sensation at the dorsal coronary band to make sure the entire foot is blocked

Question 32

what are 2 blocks you could use to block the fetlock?

Answer 32

low 4 point & fetlock joint block

Question 33

what block would you use to block out the suspensory ligament?

Answer 33

regional infiltration, high 4 point, or lateral palmar

Question 34

how would you evaluate a horse for bone spavin?

Answer 34

inject the tarsometatarsal +/- distal intertarsal joints

Question 35

what are 2 ways you could block the tibiotarsal joint?

Answer 35

intra-articular block or tibial & peroneal nerve blocks

Question 36

there are 3 joint pouches in the stifle - do you need to block all 3 separately?

Answer 36

usually the medial femorotibial & femoropatellar joints communicate but only 1 in 4 lateral femorotibial joints communicate with the femoropatellar joint

Question 37

there are 3 joint pouches in the carpus - do you need to block all 3 separately?

Answer 37

intercarpal & carpometacarpal joints communicate

Question 38

there are joint pouches associated with the hock in the horse - do you need to block all 3 separately?

Answer 38

sometimes the tarsometatarsal & distal intertarsal joints communicate proximal intertarsal & tibiotarsal joints usually communicate

Question 39

what risks are associated with local anesthetic procedures?

Answer 39

local irritation & swelling risk of creating a septic joint hemorrhage breaking a needle off