Exam 1 - Equine Nerve Blocks Flashcards
how can you avoid potential complications associated with nerve blocks?
proper restraint of the horse decreases the likelihood of needle breakage
proper prep of the site - avoid infecting synovial structures
when should you use diagnostic anesthesia in an equine lameness case?
to identify painful region when either obvious pathology is lacking or there is more than one lesion present
to direct diagnostics & imaging
which medication used for nerve blocks is least safe for joints?
bupivacaine - chondrotoxic
how should you prep a patient for a regional nerve block?
quick prep - chlorohex/betadine for 3-5 minutes
removes surface debris
what nerves are blocked by a PD block?
palmar/plantar digital nerves
how do you place your needle for a PD nerve block when taking into consideration the neurovascular bundle?
vein is most lateral
artery is middle
nerve is medial
where are your landmarks for a PD nerve block?
feel for the neurovascular bundle above the hoof cartilages
insert the needle distally about 1cm above the hoof cartilages
what structures are reliably anesthetized by a PD block?
navicular bone, navicular bursa, navicular apparatus, DDFT, frog, 1/3-1/2 sole, parts of the PIP/DIP, & skin
what is the benefit of performing a midpastern PD block?
allows for desensitization of the entire foot including the PIPJ
what nerves are desensitized by an abaxial sesamoid block?
palmar digital nerves at or near the proximal sesamoid bones
what structures are anesthetized by the abaxial sesamoid block?
everything in the PD block
DIPJ, PIPJ, distal sesamoidean ligaments, dorsal branches of the suspensory ligament, DDFT, SDFT, & +/- MCP joint
what landmarks are used for an abaxial sesamoid block?
palpate the neurovascular bundle at the abaxial border of each proximal sesamoid bone
direct the needle distally at this level
if doing a palmar/plantar PD block, what region do you expect to block? what else was potentially blocked?
palmar/plantar 1/3-1/2
most of the foot
if doing a palmar/plantar PD block including the dorsal branches, what region do you expect to block? what else was potentially blocked?
from coronary band distal
same as PD
if doing a abaxial sesamoid block, what region do you expect to block? what else was potentially blocked?
from proximal pastern distal
complete foot, pastern region, & fetlock joint
what nerve block is being done in this photo?
PD nerve block
what nerve block is being done in this photo?
abaxial sesamoid block
what block is being done in the photo? what are your landmarks?
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
what is blocked in a DIP joint block?
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)
what is blocked in a navicular bursa block? what are the landmarks used?
navicular bursa, navicular bone, & caudal portions of the heel
spinal needle is inserted between the heel bulbs parallel to the sole of the foot
what is blocked in a PIP block? what are the landmarks used?
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
what nerves are blocked in a low 4 point? what are the landmarks used?
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
what structures are blocked in a low 4 point?
entire fetlock & all structures distal to it but may miss some skin on the dorsal fetlock
what structures are blocked in a high 4 point?
deep structures of the metacarpus & all structures distal to the block with the exception of the origin of the interosseus m.
what nerves are blocked in a high 4 point? what are the landmarks used?
medial & lateral palmar & palmar metacarpal/metatarsal nerves
same as low 4 point but performed just distal to the carpus
what nerves are blocked in a lateral palmar block? what are the landmarks used?
lateral palmar nerve proximal to its deep branch & medial and lateral palmar metacarpal nerves
medial to the accessory carpal bone
what structures are blocked in a lateral palmar?
origin of the interosseus m. & other deep structures of the palmar metacarpus/metatarsus
what nerve block is pictured here?
low 4 point
what nerve block is pictured here?
high 4 point
what sort of anesthetic agent would you use to perform a lameness exam & why?
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
how would you block out the entire foot?
abaxial sesamoid nerve block - check for sensation at the dorsal coronary band to make sure the entire foot is blocked
what are 2 blocks you could use to block the fetlock?
low 4 point & fetlock joint block
what block would you use to block out the suspensory ligament?
regional infiltration, high 4 point, or lateral palmar
how would you evaluate a horse for bone spavin?
inject the tarsometatarsal +/- distal intertarsal joints
what are 2 ways you could block the tibiotarsal joint?
intra-articular block or tibial & peroneal nerve blocks
there are 3 joint pouches in the stifle - do you need to block all 3 separately?
usually the medial femorotibial & femoropatellar joints communicate
but
only 1 in 4 lateral femorotibial joints communicate with the femoropatellar joint
there are 3 joint pouches in the carpus - do you need to block all 3 separately?
intercarpal & carpometacarpal joints communicate
there are joint pouches associated with the hock in the horse - do you need to block all 3 separately?
sometimes the tarsometatarsal & distal intertarsal joints communicate
proximal intertarsal & tibiotarsal joints usually communicate
what risks are associated with local anesthetic procedures?
local irritation & swelling
risk of creating a septic joint
hemorrhage
breaking a needle off
