Exam 1 - 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

what medication is most commonly used for nerve blocks in horses? how long does the block last?

Answer 3

mepivacaine (carbocaine) - 90-120 minutes

Question 4

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

Answer 4

bupivacaine - chondrotoxic

Question 5

what are some indications for using bupivacaine for nerve blocks in a horse?

Answer 5

may use in hostile patients, sending patients for a long ride home, or prior to surgery - has the longest duration of action 4-6 hours

Question 6

what is regional/perineural diagnostic anesthesia useful for?

Answer 6

blocks articular & extra-articular structures - requires a systematic approach from distal to proximal but less prep/materials are needed

Question 7

what is synovial diagnostic anesthesia useful for?

Answer 7

intra-articular/intra-thecal - more specific of a block that can target extra-articular structures

requires more prep/materials - aseptic technique

Question 8

T/F: a synovial block may not block subchondral bone pain

Answer 8

true

Question 9

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

Answer 9

quick prep - chlorohex/betadine for 3-5 minutes

removes surface debris

Question 10

how should you prep a patient for a synovial structure block?

Answer 10

aseptic technique - prep for 10 minutes

can clip or not clip - doesn’t make a huge difference

Question 11

what nerves are blocked by a PD block?

Answer 11

palmar/plantar digital nerves

Question 12

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

Answer 12

vein is most lateral

artery is middle

nerve is medial

Question 13

where are your landmarks for a PD nerve block?

Answer 13

feel for the neurovascular bundle above the hoof cartilages

insert the needle distally about 1cm above the hoof cartilages

Question 14

what should you do ten minutes after performing a PD block?

Answer 14

check your block for skin sensitivity with hemostats - can check for loss of deep sensitivity after skin sensitivity is gone

Question 15

T/F: loss of skin sensitivity does not equal loss of deep sensitivity

Answer 15

true

Question 16

what does it mean if after a PD block is performed, a horse isn’t responsive to hemostats but is responsive to hoof testers?

Answer 16

deep sensitivity is still present - need to wait longer

Question 17

what structures are reliably anesthetized by a PD block?

Answer 17

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

Question 18

what are some potential complications associated with PD blocks?

Answer 18

hemorrhage

ineffective block - missed the nerve, not waiting long enough, injected IV/IA, or ineffective mepivacaine

blocking more than expected - diffusion

needle breakage - very very bad

inadvertent penetration of a synovial structure - digital flexor tendon sheath or palmar pouch of coffin joint

Question 19

why is a PD block with the dorsal branches likely ineffective?

Answer 19

the dorsal branches don’t innervate the DIPJ/contributes little sensation within the foot

Question 20

what is the benefit of performing a midpastern PD block?

Answer 20

allows for desensitization of the entire foot including the PIPJ

Question 21

what is another name for the basilar sesamoid block?

Answer 21

abaxial sesamoid block

Question 22

what nerves are desensitized by an abaxial sesamoid block?

Answer 22

palmar digital nerves at or near the proximal sesamoid bones

Question 23

what structures are anesthetized by the abaxial sesamoid block?

Answer 23

everything in the PD block

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

Question 24

what landmarks are used for an abaxial sesamoid block?

Answer 24

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

direct the needle distally at this level

Question 25

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

Answer 25

palmar/plantar 1/3-1/2

most of the foot

Question 26

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

Answer 26

from coronary band distal

same as PD

Question 27

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

Answer 27

from midpastern distal

complete foot/pastern joint

Question 28

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

Answer 28

from proximal pastern distal

complete foot, pastern region, & fetlock joint

Question 29

what nerve block is being done in this photo?

Answer 29

PD nerve block

Question 30

what nerve block is being done in this photo?

Answer 30

abaxial sesamoid block