Local Blocks to diagnose lameness Flashcards
what does abaxial/basisesamoid block anesthetize? (6)
Distopalmar P1 and down
- distopalamar P1
- P2
- proximal and dital interphalangeal joints
- distal SDFT/DDFT
- distal sesamoidian ligament
- digital annular ligament
landmarks for abaxial/basisesamoid block
abaxial border of each proximal sesamoid bone right along vascular bundle
criteria for using local blocks to diagnose lameness (3)
- is the horse lame enough? (not good for intermittent lameness)
- is the horse too lame? can risk injury/fracture
- will the horse tolerate the needle?
lateral palmar nerve block: where is it inserted and in what direction?
mediolateral direction on the medial side of the accessory carpal bone
done while weight bearing
High 4 point block anesthetizes…(3)
- suspensory ligament
- some flexor tendons
- some of MCIII and MCIV
reasons PD nerve block might fail (5)
- adhesions between navicular bone and DDFT
- OA of coffin
- concurrent proximal disease (suspensory apparatus issue)
- old anesthetic used
- accessory nerve supply from dorsal branches
what to remember when using low 4 point block on hindlimb?
must also direct and inject a little cranially
what position are abaxial/basisesamoid and PD nerve blocks administered?
hold limb up/non weight bearing
agents used for local blocks in equines (3)
- 2% lidocaine: cheap but burns; lasts 30 mins-2hours
- 2% mepivacaine/carbocaine: G.S. lasts 30mins-2hours; once open goes bad within 5-7 days; don’t let freeze
- 0.5% bupivacaine/Marcaine: duration 5-6 hours; only for shoeing/therapeutic; NOT for diagnostics
which nerve/nerves is targeted by abaxial/basisesamoid block and PD block?
palmar digital nerves
lateral palmar nerve block blocks _____
origin of suspensory ligament
which nerve block:
- distopalamar P1
- P2
- proximal and dital interphalangeal joints
- distal SDFT/DDFT
- distal sesamoidian ligament
- digital annular ligament
abaxial/basisesamoid block
which injection for the low 4 point block is more proximal and why?
-lateral and medial palmar nerves: between suspensory ligament and DDF (more proximal to avoid tendon sheath/flexor manica)
how much do you inject for low 4 point block?
- lateral and medial palmar nerves: between suspensory ligament and DDF (more proximal): 3 mL
- Lateral and medial palmar metacarpal nerves: find button on MIV and go just distal: 1 mL
needle usually used for nerve blocks?
25-23 G
which nerve block: coffin joint and down: -sole -navicular apparatus -soft tissues of heel -coffin joint -digital portion of DDFT
PD block
structures anesthetized by PD nerve block (5)
coffin joint and down:
- sole
- navicular apparatus
- soft tissues of heel
- coffin joint
- digital portion of DDFT
how long do most nerve blocks take before they have effect?
3-5 mins
intra-articular anesthesia: what to remember? (6)
- insert needle WITHOUT syringe
- collect synovial sample prior to anesthetizing
- MUST BE STERILE
- inject vol > than that taken -> DISTEND joint
- add 125 mg of amikacin
- allow 5-30 min for effect
true or false: presence of skin sensation does not mean block failed
true; skin first lost and first regained
what’s important to remember about the low 4 point block?
MUST be sterile because you might hit tendon sheath
where is high 4 point block injected?
below carpus in groove between DDFT and suspensory ligament
how many injections for the 4 point block?
1-2
most nerve blocks can be done with a clean prep. which must be sterile?
-low 4 point block: because you might hit the tendon sheath
also intra-articular anesthesia
direction in which the needles are inserted for low 4 point block?
perpendicular to ground
what’s important to remember about abaxial/basisesamoid block
must be superficial to DFTS
landmarks for low 4 point block
- lateral and medial palmar nerves: between suspensory ligament and DDF (more proximal)
- Lateral and medial palmar metacarpal nerves: find button on MIV and go just distal
PD nerve block: landmarks
groove between flexors and ergot, just proximal to the collateral cartilage; one injection medial and one lateral
VAN bundle there so redirect if you get blood
methods for using blocks to diagnose lameness (4)
- perineural: clean scrub; no sedation; use smallest volume possible
- regional
- direct infiltration of dite
- IA
how many injections needed for lateral palmar nerve block?
ONE
mediolateral direction on the medial side of the accessory carpal bone; anesthetizes lateral palmar nerve -> anesthetizing origin of suspensory ligament
number of injections needed for low 4 point block
2-4
- lateral and medial palmar nerves: between suspensory ligament and DDF (more proximal)
- Lateral and medial palmar metacarpal nerves: find button on MIV and go just distal
pro of the lateral palmar nerve block?
don’t have to inject directly into suspensory ligament (which can cause artifact on US)
which block?
- lateral and medial palmar nerves: between suspensory ligament and DDF (more proximal)
- Lateral and medial palmar metacarpal nerves: find button on MIV and go just distal
low 4 point
which nerve/nerves are targeted by the low 4 point block?
- lateral and medial palmar nerves
- lateral and medial palmar metacarpal nerves
