Acute and Chronic pain management in horses

Question 1

Consequences of pain

Answer 1

-anxiety or fear
-behavioural changes
-contralateral limb laminitis
-ileus- cecal impactions
*orthopedic pain can occur from cecum
-QOL concerns

Question 2

Pain pathways (KNOW THIS!)

Answer 2

1. Transduction- touching something hot or cold
2. Transmission- brain gets the pain message and transmits it to the CNS for appropriate response
3. Modulation- brain and dorsal horn of spinal cord decides how much to react to this transmission
4. Perception- life experience and cultural environment influence this

Question 3

Degrees of pain

Answer 3

1. mild
2. moderate
3. severe-controllable
4. Severe- uncontrollable

Question 4

How to measure pain?

Answer 4

-horse grimace pain scale
-Obel laminitis grading scale

Question 5

Horse Grimace pain scale

Answer 5

Horse grimace pain scale
-stiff backwards ears
-orbital tightening
-tension above the eye area
-prominent strained chewing muscles (clenching jaw) focus on this one
-mouth strained and pronounced
-strained nostrils and flattened profile
-

Question 6

Obel laminitis grading scale

Answer 6

-horse shifting weight between limbs
-can vary when walking vs trotting
-difficulty turning
-horse is reluctant or refuses to move

Question 7

What medication to use for mild pain?

Answer 7

-NSAIDs

Question 8

What medication to use for moderate pain?

Answer 8

-NSAIDs
-Gabapentinoids
-opioids
-alpha 2 agonists
-local anesthetics
-CRI

Question 9

What medications to use for severe treatable pain?

Answer 9

-opioids
-opioids and alpha 2 agonists
-local anesthetics
-CRI
-surgery

Question 10

What medications to use for severe uncontrollable pain?

Answer 10

-euthanasia

Question 11

Uses for NSAIDs

Answer 11

-anti inflammatory
-anti pyretic
-analgesic
**visceral (GI) vs. musculoskeletal pain

Question 12

Flunixin meglumine

Answer 12

-NSAID; for visceral pain (GI)
-anti endotoxic, anti inflammatory, prevent intra abdominal adhesion formation

Side Effects: GI, renal, intestinal healing delayed

Question 13

Phenylbutazone

Answer 13

-used for musculoskeletal pain (acute and chronic)

-used for right dorsal colitis (but must consider patient weight and restrict owner access)

-side effects: GI and renal

Question 14

Firocoxib

Answer 14

Cox 2 selective
-spares GI and renal system; less complications/side effects

-Used for OA pain and long term pain management

Question 15

Acetaminophen

Answer 15

-adjunct therapy, analgesic, antipyretic
-best if used with NSAID

-used for laminitis, lameness

Dose: 30 mg/kg PO BID

Question 16

Gabapentinoids mechanism of action

Answer 16

Possibly:
-changes to voltage gated Ca channels
-changes to NDMA receptor expression and binding

Question 17

Gabapentin in horses

Answer 17

-typically poor oral bioavailability in horses

Question 18

Pregabalin

Answer 18

-better oral bioavailability in horses
-used for chronic pain (laminitis and trauma)

*usually start with high dose and then taper

Question 19

Alpha 2 agonists in horses

Answer 19

-Xylazine, detomidine, romifidine

-used as sedatives, visceral analgesics
-effects: reduce GI motility, cardiovascular effects

Question 20

Alpha 2 agonists components

Answer 20

1. Sedation- activates CNS alpha 2 receptors
2. Synergism with opioids- alpha 2 agonists and butorphanol

Question 21

Xylazine specific use

Answer 21

-short half life
-moderate to severe pain

-used to assess pain severity= diagnostic aid

Question 22

Butorphanol

Answer 22

-kappa agonist, mu antagonist
-most common opioid used in horses
-used as analgesic, mild to moderate visceral pain, sedation, reduced GI motility

*costly

Question 23

Buprenorphine

Answer 23

-partial mu agonist
-longer duration of action
-local anesthetic- include in nerve blocks

Question 24

Full mu agonists used in horses

Answer 24

-Morphine
-Fentanyl- patch
-hydromorphone

Question 25

Morphine use in horses

Answer 25

*IM, CRI, epidural
*can be given with alpha 2 agonist or acepromazine

Side effects severe in horses when given IV
-excitement, disorientation, ataxia, ileus

Question 26

Ketamine

Answer 26

-decrease glutamine binding to NMDA receptor in the dorsal horn. Linked with memory of pain.
-use in acute and chronic pain (block central sensitization)

-IM, CRI, epidural

-Side effects: excitement, stall walking

Question 27

Lidocaine

Answer 27

-local vs systemic administration (CRI)

-Potentiates analgesic actions of opioids and alpha 2 agonists
-Used to increase GI motility (post op ileus) and anti inflammatory, decrease need for inhalant and injectable anesthetics

-concurrent admin with flunixin allows for decrease in flunixin dose= improved intestinal healing

Question 28

Mepivacaine

Answer 28

-duration of action = 2-3hrs

Question 29

Bupivacaine

Answer 29

-duration of action= 6hrs
-can be used to block injured limb to have them stand on that one during procedure to give healthy limbs a break

Question 30

IV or IM drugs

Answer 30

-NSAIDs
-alpha 2 agonists
-butorphanol
-morphine
-buscopan

Question 31

CRI drugs

Answer 31

-butorphanol/morphine
-lidocaine
-ketamine
-dexmedetomidine

Question 32

Epidural

Answer 32

-can use ketamine, morphine, alpha 2 agonists

-both coccygeal or epidural catheter

Question 33

Where are drugs acting in pain pathway?

Answer 33

-notice multimodal approach

Question 34

Laminitis

Answer 34

-common; very painful
-separation of lamina and bone
see sinking/rotation of P3 into the hoof wall