Nerve Blocks Flashcards
(30 cards)
What do nerve blocks do?
AKA perineural anesthesia
blocks sensory or afferent nerves (cannot transmit pain to spinal cord and brain)
localize source of lameness
direct further diagnostics or treatment to specific area
When are nerve blocks useful?
when lameness is obvious and not subtle, heabob, hip hike, not bearing weight on the leg well
What do local anesthetics do?
Block nerve’s ability to conduct impulse
Effective only at site of injection
What are the three anesthetics?
lidocaine
mepivacaine
bupivacaine
What are the qualities of local anesthetic?
Rapid onset of action
Good efficacy
Long duration of action
Very few side effects
What is the technique for nerve blocks?
No sedation (have an anti-pain effect, causing a difference in the lameness)
Patient restraint
Preparation of area (not a sterile prep, just a cleaning of the area)
§ Chlorhexidine or betadine
§ Isopropyl alcohol
Remove needle from syringe
Insert needle through skin
Re-attach syringe
Inject anesthetic in SQ space
Wait 5-10 minutes
Check for sensation
What are the perineural analgesia in the forelimb?
palmar digital (PD)
abaxial sesamoid
low four-point
high four-point
high palmar
proximal nerves (we are not really focusing on these)
What are the intrasynovial analgesia blocks?
go into a sterile structure, helps narrow down area to a particular structure
joints
bursa
tendon sheaths
Where is the PD nerve block?
mid to low palmar/plantar pastern
as far down as you can go in the horse (low as you can go)
What does the PD nerve block target?
medial and lateral palmar digital nn.
What does the PD nerve block desensitize?
palmar 1/3 of foot
navicular bone, navicular bursa, DDFT insertion, navicular bursa, digital cushion, part of coffin joint, whole sole of the foot (frog too)
does not get the structures in the horses toe (extensor tendon insertion on P3, lamina, some fractures to the coffin bone)
Where is the abaxial sesamoid nerve block?
outside of proximal sesamoid bones at fetlock (VAN)
What does the abaxial sesamoid nerve block target?
medial and lateral palmar digital nn. (before they give off dorsal branches) and dorsal branches
What does the abaxial sesamoid nerve block desensitize?
everything below fetlock joint
not including the fetlock joint
What structures are blocked in an abaxial nerve block?
Do the medial side first, and the lateral second
blocks: everything from PD nerve block, more parts of the tendons, distal sesamoidean ligaments, tendon sheaths, coffin joint, pastern joint
Where is the low four-point nerve block?
distal to splint bone button
where you can palpate the splint bone buttons
What does the low four-point nerve target?
medial and lateral palmar nerves: palmar to suspensory ligament, dorsal to DDFT. Towards the back of the horses distal limb
medial and lateral palmar metacarpal nerves: distal to splint bone buttons, careful to avoid palmar pouch of fetlock joint. In between the cannon bones, splint bones, and suspensory ligaments. Be careful because the palmar pouch of the fetlock joint is in this area.
4 nerves total!
What does the low four-point nerve block desensitize?
fetlock joint and below
distal cannon, flexor tendons, tendon sheaths, proximal sesamoid bones, suspensory branches
Where is the high four-point nerve block?
above communicating branch of palmar nerves
just below the horses carpus, proximal to the communicating branch of nerves
What does the high four-point nerve block target?
medial and lateral palmar nerves: palmar to suspensory ligament, dorsal to DDFT
medial and lateral palmar metacarpal nerves: between canon and proximal splint bones
4 nerves again, same as in the low four point
What does the high four-point nerve block desensitize?
desensitizes flexor tendons, suspensory ligament (not origin), mid-cannon, and below
most of the horses distal limb
Where is the high palmar nerve block at accessory carpal bone?
distal to accessory carpal bone
What does the high palmar nerve block at accessory carpal bone target?
lateral palmar nerve before it gives off medial and lateral palmar metacarpal nerves (blocks 3 of 4 nerves)
still need to block the medial palmar nerve
What does the high palmar nerve block at accessory carpal bone desensitize?
all structures distal to carpus, including origin of suspensory (important)
