Anesthesia of lameness evaluation (Forelimb)

Question 1

Anesthetics used for nerve blocks

Answer 1

Lidocaine (cattle)- 1-2 hr
Mepivacaine***** - 2-3 hr
Bupivacaine (special)- 3-6 hr

Question 2

Action of nerve blocks

Answer 2

Reversibly blocking fast voltage- gated sodium channels preventing AP

Question 3

What does DOA and quick action depend on

Answer 3

DOA: protein binding
Quick acting: lipid solubility

Question 4

What are the complications of placing the palmar digital NB too distal?

Answer 4

Fail to anesthesize branches of nerve and misinterpretation of the block

Question 5

What are the complications of placing the palmar digital NB too proximal?

Answer 5

Desensitize the proximal interphalangeal joint and other structures in the pastern joint

Question 6

What’s the purpose of blocking the ramus tori digitalis?

Answer 6

Selective desensitization of the navicular apparatus without loss of skin sensation in the heel region of the foot

Question 7

What is the reason fro ineffective desensitization after a PD NB?

Answer 7

Aberrant nerve branches

Question 8

Complication of the abaxial nerve block

Answer 8

Desensitizes partially or completely the metacarpophalangeal joint

Question 9

Potential complication of the palmar metacarpal NB

Answer 9

Inadvertent synoviocentesis of the MCP joint

Question 10

Ramus communicans

Answer 10

Carries sensory impulses in both directions and connects the medial and lateral palmar nerves

Question 11

Where should the palmar nerves be anesthetized and why?

Answer 11

Inserting the needle in a proximodistal direction, advancing the needle parallel with in the skin
Not too deep to avoid entering the digital flexor tension sheath

Question 12

Why should the palmar nerves be blocked proximal to the level of the metacarpal bones?

Answer 12

To avoid the risk of placing the needle in the digital flexor tendon sheath

Question 13

High four-point block

Answer 13

Anesthesia of the medial and lateral palmar nerves and the medial and lateral palmar metacarpal nerves in the proximal metacarpal region

Question 14

What prevents the palpation of the palmar nerves when performing the high four point block?

Answer 14

The presence of the palmar metacarpal fascia (carpal retinaculum flexorum)

Question 15

Subcarpal high four-point block

Answer 15

Med/Lat. palmar nerves: blocked subfascial with limb weight bearing, needle inserted perpendicular to skin beneath distal extent of the carpal flexor retinaculum and dorsal to the DDFT and distal to the CMC joint
Med/ Lat. palmar metacarpal: same level as CMC joint with capus flexed

Question 16

Ipsilateral high four-point block

Answer 16

Medial palmar: longer needle and advancing it from the lateral injection site to the medial palmar nerve dorsal to the DDFT
Medial palmar metacarpal: dorsomedial direction from a SQ position

Question 17

Alternative to the high four point nerve block

Answer 17

Lateral palmar NB

Question 18

Lateral approach to (Wheat block) lateral palmar NB

Answer 18

Needle inserted in a palmarolateral to dorsomedial direction @ the distal aspect of the accessory carpal bone

Question 19

Disadvantages to the ateral approach to (Wheat block) lateral palmar NB

Answer 19

Inadvertent injection of the carpal canal
Difficulty of injection because nerve runs with ligament

Question 20

Medial approach lateral palmar NB

Answer 20

Inserted perpendicular to the longitudinal vertical groove on the medial aspect of the distal third of the accessory carpal bone
Advanced in the mediolateral direction until needle contacts the bone

Question 21

Disadvantages to the medial approach to lateral palmar NB

Answer 21

Significant reaction from horse
Extensive proximal diffusion of local anesthetic solution → desensitization of the palmar carpus and distal forearm

Question 22

Cautions for median and ulnar NB

Answer 22

Result in forelimb weakness with risk of tripping and falling

Question 23

Dorsal parallel approach of the Distal interphalangeal joint

Answer 23

Easiest and most accurate
Inserted parallel to bearing surface of the foot or proximal to the coronary band →passing through digital extensor tendon → enters dorsal pouch of DIP joint

Question 24

Dorsal inclined approach of the Distal interphalangeal joint

Answer 24

Avoids sensitive coronary band and accommodates diverse foot shapes and positions
Inserted perpendicular to the skin surface proximal to coronary band

Question 25

Lateral approach of the Distal interphalangeal joint

Answer 25

Less painful
Inserted in the depression in the proximal border of the lateral cartilage → lateromedial direction penetrating the palmar pouch

Question 26

4 approaches to proximal interphalangeal joint

Answer 26

1. Dorsal
2. Dorsolateral
3. Palmar proximal
4. Palmar lateral* (DIP and PIP joint flexed → needle inserted proximal palmar border of middle phalanx → perpendicular to the sagittal plane, directed medially perpendicular to long axis of middle phalanx)

Question 27

Palmar/ Plantar axial sesamoidean approach to the digital flexor tendon sheath

Answer 27

Needle at lat. prox. sesamoid bone, 3 mm axial to border and neurovascular bundle → advanced through skin and annular lig of MCP joint aiming to central intersesamoidean region

Question 28

Advantage of palmar/ Plantar axial sesamoidean approach to the digital flexor tendon sheath

Answer 28

Accurate when the DFTS is not distended with synovial fluid

Question 29

Basilar sesamoidean approach to the digital flexor tendon sheath

Answer 29

MCP/MTP region in flight flexion → needle inserted distal to lat. sesamoid bone into depression → advanced in a lateromed. and distoprox direction

Question 30

Advantages of basilar sesamoidean approach to the digital flexor tendon sheath

Answer 30

More likely to result in retrieval of synovial fluid to verify accuracy of centesis

Question 31

Technique to avoid misinterpreting a positive response to the digital flexor tendon sheath

Answer 31

Testing for skins sensation at the lateral heel bulb after performing anesthesia of the DFTS

Question 32

Dorsal approach to the fetlock joint block

Answer 32

Limb bearing weight
Needle inserted under the lateraedge of the common digital extensor tendon @ the palpable joint space

Question 33

Collateral Sesamoidean Ligament approach to the fetlock joint block

Answer 33

Limb is held with joint slightly flexed
V-shaped gap between sesamoid and MCIII

Question 34

Proximal palmar/plantar pouch approach to the fetlock joint block

Answer 34

Vascular area that usually result in contaminate sample