Diagnostic analgesia Flashcards
how do local anaesthetics work?
blocking sodium channels to prevent depolarisation
what are two common local anaesthesia used in equine diagnostics?
mepivicaine
bupivicaine
when should diagnostic analgesia not be used?
suspected fractures
cellulitis
uncooperative horse
why shouldn’t diagnostic analgesia be used for cases with cellulitis?
could introduce further infection
local anaesthetics don’t worm as well because the tissue is slightly acidotic
what are some possible complications associated with diagnostic analgesia?
broken needles
severe lameness after block (flare, local reaction, synovial sepsis)
what may be a reason for poor responses to local anaesthesia?
severe pain
poor technique or inadequate volume
nerve variations
subchondral bone pain
previous neurectomy
if pain originates more proximal (from neck/back…)
neurological lameness (non-pain related lameness)
what are the possible perineurial blocks of the forelimb?
palmar digital nerve block
abaxial sesamoid nerve block
low 4 point block
high 4 point
median/ulnar
what are the possible perineurial blocks of the hindlimb?
palmar digital nerve block
abaxial sesamoid nerve block
low 6 point nerve block
high 6 point nerve block
tibial/peroneal
what are the possible synovial structures that can be blocked in the forelimb?
distal interphalangeal joint
navicular bursa
proximal interphalangeal joint
digital flexor tendon sheath
metacarpophalangeal joint
carpal joints
carpal sheath
elbow
shoulder
bicipital bursa
what are the possible synovial structures that can be blocked in the hindlimb?
distal interphalangeal joint
navicular bursa
proximal interphalangeal joint
digital flexor tendon sheath
metatarsophalangeal joint
tarsal joints
calcanea bursa
tarsal sheath
stifle
hip
what is usually the first block done in the forelimb?
palmar digital nerve block
what is usually the first block done in the hindlimb?
abaxial sesamoid nerve block
where is the site for a palmar digital nerve block?
just proximal to collateral cartilage abaxial to edge of DDFT (palpate neurovascular bundle then place needle angled distally over bundle)
is the palmar digital nerve block done with the horse weightbearing or not?
non-weightbearing
what volume of local is used for palmar digital nerve block?
1.5-2ml (medially and laterally)
what are the structures desensitised by the palmar digital nerve block?
navicular bone
navicular bursa
collateral suspensory ligaments
distal sesamoidean impar ligament
distal deep digital flexor tendon/sheath
insertion of superficial digital flexor tendon
digital cushion
palmar third of lamellar corium and corium of sole
palmar process of pedal bone
collateral cartilages
how can you check the palmar digital nerve block has worked?
testing sensation of the heel bulb
what is the site used for an abaxial sesamoid nerve block?
immediately palmar to neurovascular bundle at the abaxial surface of the base of the proximal sesamoid bone (insert needle distal and parallel to the neurovascular bundle)
what volume is used for an abaxial sesamoid nerve block?
2ml
what structures are blocked by the abaxial sesamoid nerve block?
(palmar digital nerve block)
rest of P3 and P2
palmar P1
collateral ligaments of distal and proximal interphalangeal joints
distal and proximal interphalangeal joints
distal sesamoidean ligaments
lamellar corium and coronary band
distal digital extensor tendons
dorsal suspensory ligament
what is the site for a distal interphalangeal joint nerve block?
dorsal approach palpating depression just proximal to coronary band (needle vertically through skin and extensor tendon)
what volume is used for a distal interphalangeal nerve block?
6ml
what structures are desensitised by a distal interphalangeal nerve block?
distal interphalangeal joint
collateral ligaments of DIP
navicular bone/bursa
toe region of sole
what is the coffin joint?
distal interphalagneal joint
what is the site for a navicular bursa nerve block?
between bulb of heel inserting needle horizontally on midline through DDFT
what volume is used for a navicular bursa nerve block?
2-4ml
what special consideration needs to be done for navicular bursa nerve blocks?
are done using radiography to guide needle
what does the navicular bursa nerve block desensitise?
navicular bone and bursa (specific)
what should always be done before blocking the foot?
put hoof testers on to check for pain in the actual foot rather than deeper pain
