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SP2 Musculoskeletal > Lecture 31 4/10/25 > Flashcards

Lecture 31 4/10/25 Flashcards

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1
Q

What are the indications for regional and synovial anesthesia?

A

-perform sx without needing general anesthesia
-provide temporary, humane pain relief
-localize pain causing lameness to a particular region (most common)

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2
Q

What are the most common anesthetics used for regional anesthesia?

A

-mepivacaine
-lidocaine
-bupivacaine

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3
Q

What are the characteristics of mepivacaine?

A

-preferred by most clinicians for regional anesthesia
-effects last 90 to 120 minutes
-duration of effects is good for identifying lameness in multiple limbs/sites
-causes little tissue reaction

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4
Q

What are the characteristics of lidocaine?

A

-effects only last 30 to 60 minutes
-more irritating than mepivacaine
-might be preferred when different techniques of diagnostic analgesia are likely to be used during lameness exam
-fast onset

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5
Q

What are the characteristics of bupivacaine/marcaine?

A

-provides anesthesia for 4 to 6 hours
-used to provide temporary pain relief rather than to isolate site of pain/lameness

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6
Q

Which needles are used for different regional anesthesia applications?

A

-nerves below carpus/hock: 23 or 25 gauge needle in a 5/8 in. length
-nerves more proximal than carpus/hock: 20 or 22 gauge needle in a 1 1/2 in. length

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7
Q

Why should luer-slip syringes be used instead of luer-lock syringes when doing regional anesthesia?

A

-needles are inserted detached from the syringe
-locking syringes are difficult to attach and cannot be detached quickly
-slip syringes prevent needles from being pulled out, bent, or broken with movement

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8
Q

Why should needles be inserted in a distal direction for PD nerve blocks and abaxial sesamoid nerve blocks?

A

proximal direction could cause increased proximal migration of the anesthetic agent and cause unintended anesthesia of more proximal nerve branches

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9
Q

What are the characteristics of anesthetic volume when doing injections below the carpus/hock?

A

-want to use 1 to 2 mL per nerve
-small amounts avoid inadvertent anesthesia of adjacent nerves and proximal migration
-even smaller volumes can be used when the neurovascular bundle or nerve can be palpated SQ

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10
Q

Why is it important for a horse to be consistently and sufficiently lame during the lameness exam?

A

it gives the best chance of detecting and interpreting the lameness so that improvements can be detected once regional anesthesia is applied

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11
Q

How can a subtle lameness be exacerbated prior to regional anesthesia testing?

A

lunging or riding

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12
Q

Why is it important to sufficiently exercise a horse prior to regional anesthesia?

A

some lamenesses improve or resolve with exercise (warmed out of) and can lead to a false positive with the regional anesthesia

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13
Q

How can the accuracy of regional anesthesia evaluation be improved?

A

using Equinosis Q with the inertial sensors to detect and quantify the lameness before and after injections

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14
Q

How long must you wait after a regional anesthesia injection before testing for lameness improvement?

A

-distal to carpus: around 5 minutes
-proximal to carpus: 20 to 40 minutes
*presents false results from assessing before pain relief

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15
Q

Why is it important to evaluate gait within 15 minutes of a block within the distal portion of the limb?

A

anesthetic migrates proximally with time; assessing too late after administration could lead to false results

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16
Q

How can the effectiveness of a nerve block be determined prior to gait testing?

A

checking for skin sensation within the dermatome that is expected to be anesthetized by the block; press tip of pen or similar instrument over the region

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17
Q

What is important regarding stoic patients and regional anesthesia?

A

stoic patients may not react to skin stimulation even if the regional anesthesia is ineffective; should check the other limb in these patients to determine effectiveness vs. stoicness

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18
Q

What can lead to a false negative with regional anesthesia?

A

-stoic horses that make you believe the block has taken effect when it has not
-injection of anesthetic into vessels or synovial structures instead of around the nerve

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19
Q

What are the characteristics of skin prep prior to regional anesthesia?

A

-clipping hair is unnecessary
-70% isopropyl alcohol applied for short-haired horses
-site should be scrubbed with antiseptic soap, esp. if dirty or close to a synovial structure

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20
Q

What are the characteristics of restraint for regional anesthesia?

A

-can be accomplished with minimal restraint
-may need a lip twitch/chain for some animals
-DO NOT restrain horses in stocks; increases likelihood of injury to clinician and patient

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21
Q

Which sedatives can be used without interference if needed when doing regional anesthesia?

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A

-acepromazine
-xylazine
-detomidine

22
Q

What is a potential benefit of sedation during regional anesthesia?

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A

sedation can cause horse to focus on pain rather than environment, making the lameness more apparent

23
Q

What is the safest way to perform blocks below the fetlock of the pelvic limb?

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A

have the limb stretched caudally and held on the thigh of the clinician performing the block

24
Q

What are the characteristics of the palmar digital nerve block?

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A

-most commonly performed block of the forelimb
-performed with limb held
-needle is inserted in a distal direction directly over the neurovascular bundle
-1 to 1.5 mL of anesthetic solution is deposited at the junction of nerve and cartilage
-medial and lateral sides can be done one at a time if suspicious of a unilateral lameness

25
What are the two methods for holding the forelimb for regional anesthetic application?
-facing the same direction and holding the foot between the knees; frees up both hands -facing the opposite direction and holding the limb with one hand while performing the procedure with the other
26
What is desensitized in the palmar digital nerve block?
-entire foot, including the coffin joint -possible partial desensitization of the pastern joint
27
What are the characteristics of the abaxial sesamoid nerve block?
-done in horses who have continued pain after a palmar digital nerve block -palmar digital nerves are anesthetized at the level of the proximal sesamoid bones in this block
28
What are the characteristics of the "basisesamoid" block?
-modification of abaxial sesamoid nerve block in which solution is deposited at base of sesamoid bones -more proximal deposition; may desensitize portion of fetlock -positive response localizes site of pain to pastern
29
What are the characteristics of a low 4-point nerve block?
-performed after neg. responses to abaxial sesamoid and PDN blocks -performed with horse bearing weight or with limb held -anesthetizes medial and lateral palmar nerves -anesthetizes medial and lateral palmar metacarpal nerves -want to stay below the ramus communicans
30
Where is the anesthetic injected for the low 4-point nerve block?
-palmar nerves: between suspensory lig. and DDFT -palmar metacarpal nerves: at the distal end of each splint bone
31
Why is it important to perform the low 4-point nerve block distal to the ramus communicans?
-sensory fibers travel in both directions in the ramus communicans to connect medial and lateral palmar nerves -anesthetizing below the ramus communicans prevents non-desensitized sensory fibers from travelling along this connection
32
What does a positive response to the low 4-point block localize to?
fetlock
33
What are the characteristics of the high 4-point block?
-done when there is a neg. response to the low 4-point block -anesthetizes same nerves as the low 4-point block but just slightly distal to the carpometacarpal joint -anesthetizes above the ramus communicans
34
What are the characteristics of a lateral palmar nerve block?
-done when site of pain is suspected to be proximal portion of suspensory lig. -lateral palmar nerve is anesthetized -lateral palmar n. gives rise to deep branch of lateral palmar n., which gives rise to the palmar metacarpal nerves
35
What is the technique for the lateral palmar nerve block?
2 mL of anesthetic injected at the distal 1/3rd of groove on the medial aspect of accessory carpal bone using a 25 gauge, 5/8th needle
36
What are the characteristics of synovial anesthesia on the forelimb?
-can perform blocks of the carpus, elbow, and/or shoulder if the regional blocks fail to localize lameness -order in which joints are desensitized is not important -elbow is typically blocked last because it is the least likely site of pain causing lameness
37
What are the characteristics of the low plantar nerve block?
-aka low 6-point block -dorsal metatarsal nerves supply additional innervation to this region, but only to the skin; blocking is technically unnecessary
38
What are the characteristics of the high plantar nerve block?
-aka high 4-point block -performed using similar techniques to high palmar nerve block -done about 1 cm distal to tarsometatarsal joint
39
How is the deep branch of the lateral plantar nerve anesthetized?
deposition of anesthetic 1 cm distal to the TMT joint, axial to the lateral splint bone, and between the DDFT and suspensory lig.
40
When would you want to anesthetize the deep branch of the lateral plantar nerve?
when the proximal aspect of the suspensory lig. is suspected to be the site of pain
41
what are the potential complications of regional anesthesia?
-broken needle shafts -SQ infection -infection of synovial structures -systemic detection of local anesthetic solution (competition horses)
42
What is the purpose of synovial injections?
-to instill medication into a diseased joint -to lavage an infected synovial structure -to examine the integrity of synovial structure(s) adjacent to a wound -to localize lameness to a particular site
43
What are the characteristics of synovial anesthesia?
-instillation of anesthetic into joint, bursa, or tendon sheath to verify or discount synovial pain as the cause of lameness -order in which joints are desensitized is not important -should check on the block within 8 to 10 minutes
44
What is a main drawback of synovial anesthesia?
diffusion of anesthetic into adjacent nerves can create a false interpretation
45
What are the preparation steps for synovial anesthesia?
-do not clip; can increase susceptibility to infection -thoroughly scrub site with antiseptic soap -spray or wipe area with 70% isopropyl alcohol
46
How is synovial contamination prevented?
-do not clip hair if using a hypodermic needle -do clip hair if using a needle with a stylet -use smallest gauge needle that is practical -do not reinsert the same needle if you miss the block -allow synovial fluid to drip from needle hub or aspirate fluid into a separate syringe before injecting medication -do NOT inject into a joint through inflamed tissue -use unused bottle of local anesthetic -can administer antimicrobials w/ anesthetic
47
Which antimicrobials are most commonly used in combination with local anesthetic solution?
aminoglycosides
48
What is a downside to using bupivacaine in the joints?
may induce chondrocytotoxicity when administered
49
What are the characteristics of the needles and syringes used for synovial injections?
-use only disposable needles -use a needle with a longer length than needed to enter joint -insert needle detached from syringe -only use luer-slip syringes; not luer-lock -redirect needle WITHOUT drawing back through skin if joint space is not entered with initial thrust
50
What is the most accurate indication of successful synoviocentesis?
synovial fluid exiting needle *important to note that needle can be placed correctly even without seeing/aspirating fluid
51
What are the techniques for restraining a limb for distal synovial injections?
-limb held -limb weight-bearing while contralateral limb is lifted

SP2 Musculoskeletal (43 decks)

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