Chapter 24 - Equine Pain Management Flashcards
What stimulates neuroendocrine responses in animals?
Tissue damage
Which hormones increase due to trauma or surgery?
- ACTH,
- cortisol,
- renin
What two adverse clinical effects can pain cause in the gastrointestinal system?
Colic, weight loss
What cardiovascular changes result from increased sympathetic tone?
Increased heart rate
What long-term adverse consequence can acute pain lead to?
Chronic pain
What types of pain may horses experience simultaneously (3)?
- Physiological
- Inflammatory
- chronic
What receptors are activated in response to acute pain?
Nociceptors
What two fiber types transmit superficial pain signals to the spinal cord (2)?
- Aδ
- C fibers
Which tract transmits superficial pain signals from somatic structures to the brain? And from deep?
Spinocervicothalamic tract for superficial and
spinoreticular tract for the deep
What part of the brain perceives pain?
Somatosensory cortex
Where do descending inhibitory pathways originate in the brain?
Periaqueductal grey, ventromedial medulla
Name 5 neurotransmitters involved in descending inhibitory pathways.
- Glutamate
- Gama-aminobutyric acid (GABA)
- Endogenous opioids
- Norepinephrine
- Serotonin
- GEENS -
What theory explains the balance between excitatory and inhibitory pain inputs?
Gate theory
What can peripheral sensitization lead to clinically?
Allodynia
What inflammatory mediators are released during peripheral sensitization?
Prostaglandins, bradykinin
What is the primary neurotransmitter involved in central sensitization?
Glutamate
Which receptor’s stimulation is key in central sensitization?
NMDA receptor
What term describes an exaggerated response to a noxious stimulus?
Hyperalgesia
What occurs in the surrounding non-injured area in central sensitization?
Secondary hyperalgesia
Why is pain control more difficult after central sensitization?
Enhanced transmission
What plays a key role in the development of chronic pain?
Central sensitization
What is the main welfare implication of chronic pain in horses?
Difficult diagnosis
Which common equine condition is associated with chronic pain?
Laminitis
What can reduce the incidence of chronic pain post-surgery?
Preemptive analgesia
What chronic condition can lead to humane destruction of a horse due to severe pain?
Laminitis
Why is it challenging to assess pain in horses using physiological variables alone?
Poor correlation
What facial feature changes are part of the equine “pain face”?
Ear position, tense stare, nostril dilation
Which scale is used to detect pain in horses following castration?
Horse Grimace Scale (HGS)
Name two subtle signs of pain that may not be visible from a distance.
Bruxism, muscle fasciculations
What should be monitored to assess pain in cases of dental pain?
Food and water consumption
What tool is used to assess induced back pain in horses?
Algometer pressure quantification
Pressure algometry in a horse. The algometer is applied to the horse’s skin in the area of interest and pressure is applied until a response (skin twitch, local muscle contraction, or movement of the horse) is observed: “threshold pressure.” The algometer is removed from the skin as soon as the response is observed.
Which class of drugs is recommended for preemptive analgesia on the morning of surgery?
NSAIDs
Name two drugs commonly used in multimodal analgesia for horses.
Opioids, ketamine
What non-pharmacological factors assist with pain management?
Immobilization, surgery
What role do NSAIDs play in equine pain management?
They inhibit cyclooxygenase (COX) enzymes, particularly effective against inflammatory pain.
What are the two types of COX enzymes, and how do they differ?
COX-1 is constitutive; COX-2 is inducible after tissue trauma.
Which NSAIDs are commonly used in horses?
Phenylbutazone, flunixin meglumine, and ketoprofen.
Other NSAIDS used in horses?
vedaprofen, suxibuzone (precursor of phenylbutazone), carprofen
What gastrointestinal issues can arise from NSAID administration in horses?
Gastric ulceration and right dorsal colitis.
Why should care be taken when administering NSAIDs to sick horses?
Due to their relatively low therapeutic index.
What is the recommended loading dose for firocoxib in horses?
0.3 mg/kg before the maintenance dose of 0.1 mg/kg once daily.
What form of diclofenac is FDA-approved for use in horses?
Liposome-based diclofenac cream (Surpass Topical Cream).
How do opioids produce analgesia?
By binding to mu (μ), kappa (κ), or delta (δ) receptors in the spinal cord and brain.
After surgery under general anesthesia, horses that received buprenorphine had lower pain scores than those that received butorphanol TRUE or FALSE
TRUE
What common side effect is observed with opioid administration in pain-free horses?
Excitement due to CNS stimulation.
What is a potential adverse effect associated with morphine in horses?
Postanesthetic colic.
What opioid is a μ-agonist and κ-antagonist and has shown promise for analgesia in horses?
Buprenorphine.
What method of opioid administration can be used for “needle-shy” horses?
Transmucosal or transdermal routes.
What is the advantage of using α2-adrenoceptor agonists in pain management?
They provide analgesia and sedation, enhancing multimodal analgesic techniques.
How do local anesthetics function in pain management?
By blocking sodium channels in excitable membranes, preventing nociceptive information transfer.
What is a common local anesthetic technique used for flank laparotomies in horses?
Paravertebral anesthesia.
What new method has been developed for long-term analgesia of the distal thoracic limb?
Continuous perineural blockade of palmar nerves.
What are potential adverse effects of segmental thoracolumbar anesthesia?
Ataxia of the pelvic limbs.
Floriano et al 2023 JAVMA The dilutional volume of morphine and xyla administered caudal epidural kt affects cranial spread of anesthesia in healthy standing horses - What substances were tested for epidural analgesia?
Morphine and xylazine with 0.2 mg/kg morphine and 0.2 mg/kg xylazine diluted to 20, 35, 50, 75, and 100 mL.
How many volumes of injectate were tested?
Five volumes
Main conclusion of Floriano et al 2023 JAVMA?
epidural volumes caused significant changes in thermal threshold testing at location hindlimb dorsal pasterns but only the largest volume resulted in a significant TT testing change at location withers.
**An 18-gauge to 20-gauge spinal needle (bevel facing craniad) is inserted through the skin (Figure 24-3). The angle of insertion may need to be altered to ensure that the needle passes through the interspinous and interarcuate ligaments and into the epidural space. A change in resistance to needle advancement may be appreciated as the epidural space is entered. The needle should be withdrawn approximately 5 mm if the floor of the vertebral canal is encountered. Needle placement can be verified by the “hanging drop” technique;
What is lidocaine often used for post-surgery in horses?
Reduce ileus
What is the dosage for conscious experimental horses to achieve antinociceptive effects in lidocaine?
2 mg/kg
What may prolong recovery during anesthesia with lidocaine?
Increased dosage
When should lidocaine infusion be terminated during anesthesia?
30 min befofre
What type of receptors does ketamine act on?
NMDA receptors
What adverse effects were noted during ketamine infusion in horses?
None detected
What are the conflicting results regarding tramadol in horses?
Efficacy uncertain
What is the dosage for tramadol that did not produce antinociception?
Up to 3 mg/kgbut the dosage is 10 mg/kg BID PO
What is the CRI dosage of ketamine in awake horseS?
0.4-0.8 mg/kg/hr
What may improve tramadol analgesia in chronic laminitis?
Co-administration with Low-dose ketamine
What does gabapentin modulate to reduce hyperalgesia? dosage?
Calcium channels
2.5 mg/kg
Butorphanol is what type of opioid? Pain dosage?
κ-receptor agonist and μ-receptor antagonist activity
dosage recommended for analgesia (0.1 mg/kg) is approximately 5 to 10 times that recommended for sedation.
Classify accordingly to κ-receptor agonist or μ-receptor agonist
Morphine μ-receptor agonist
Burprenorphine μ-receptor agonist
Fentanyl μ-receptor agonist
Butorphanol μ-receptor antagonist
What effect does intraarticular morphine have in horses?
Analgesic and antiinflammatory
What are the two sites for epidural injections in horses?
Lumbosacral space (cranial),
1st coccygeal interspace (caudal)
What is a contraindication for caudal epidural administration?
Infection
coagulopathies (risk of bleeding within spinal canal)
ataxia
neuro disease
septicemia (risk of spread infection into epidural space)
What technique verifies needle placement in the epidural space?
Hanging drop technique
Paravertebral anesthesia is performed at what level?
18th thoracic and 1/2nd o,bar dorsal and ventral branches
In the paravertebral anesthesia which structures are desensitized?
Skin, muscles and peritoneum of the flank region
What types of drugs are administered into the epidural space in horses?
Local anesthetics, opioids
What is recommended regarding drug solutions for epidural use?
Preservative free
What volume of local anesthetic should be limited to in a 500-kg horse?
8 to 9 mL
Which opioids can be preservative-free for epidural use?
Morphine, methadone
What dosage of morphine produced lower pain scores post-surgery?
0.1 mg/kg
What are potential adverse effects of epidural morphine in horses?
Pruritus, wheals
How long does analgesia last with epidural xylazine?
2 to 3 hours
What are the dosages of xylazine and detomidine for epidural analgesia?
0.17 mg/kg, 0.06 mg/kg
What is a useful combination for multimodal analgesia post-surgery?
Morphine and xylazine
What do acupuncture and electroacupuncture increase in cerebrospinal fluid?
β-endorphin concentration
Which ligaments do you have to pass during epidural analgesia?
Through interspinous
Interacurate ligaments
What are the indications of epidural?
Obstetric surgery,
Tail and perineum
Urogenital
Posoperative pain management
What condition was notably studied for ESWT effectiveness?
Navicular disease
de Oliveira et al EVJ 2020 Postop pain beahviour associated with surgical castration in donkeys - What was the only specific pain behavior observed in donkeys after castration?
A) Head shaking
B) Ear movements
C) Lifting pelvic limbs
D) Tail movements
C) Lifting pelvic limbs
de Oliveira et al EVJ 2020 Postop pain beahviour associated with surgical castration in donkeys -Which behavior increased after administering analgesia to the donkeys?
A) Pelvic limb lifting
B) Feeding and water intake
C) Head shaking
D) Ear movements
B) Feeding and water intake
de Oliveira et al EVJ 2020 Postop pain beahviour associated with surgical castration in donkeys -What were the main confounding factors influencing the expression of pain behaviors in donkeys?
A) Weather conditions and temperature
B) Dirty stall and insects
C) Time of surgery
D) Type of analgesic used
B) Dirty stall and insects
Mercer et al 2022 EVJ Pharmacokinetics and clinical efficacy of acetaminophen
(paracetamol) in adult horses with mechanically induced
lameness - What was the maximum plasma concentration (Cmax) of acetaminophen at 30 mg/kg?
A) 20.01 μg/ml
B) 30.02 μg/ml
C) 10.5 μg/ml
D) 25.5 μg/ml
B) 30.02 μg/ml
Mercer et al 2022 EVJ Pharmacokinetics and clinical efficacy of acetaminophen
(paracetamol) in adult horses with mechanically induced
lameness -At which time points was heart rate for acetaminophen 30 mg/kg significantly lower than phenylbutazone?
A) 1 and 3 hours
B) 2, 3, 4.5, and 7 hours
C) 0.5 and 2 hours
D) 6 and 8 hours
B) 2, 3, 4.5, and 7 hours
Mercer et al 2022 EVJ Pharmacokinetics and clinical efficacy of acetaminophen
(paracetamol) in adult horses with mechanically induced
lameness - What was the main limitation of the study?
A) High cost of treatments
B) Lack of objective lameness measurement
C) Inconsistent dosing schedules
D) Use of non-reversible lameness model
B) Lack of objective lameness measurement
Mercer 2021 EVE Which receptors are primarily involved in pain modulation within the endocannabinoid system?
A) CB1 and CB2
B) CB3 and CB4
C) GABA and serotonin receptors
D) Dopamine and norepinephrine receptors
A) CB1 and CB2
Mercer 2021 EVE What is the main issue with cannabinoid product manufacturing in terms of dosing?
A) Over-regulation of CBD concentrations
B) Inconsistent CBD concentrations
C) Lack of THC in products
D) High cost of production
B) Inconsistent CBD concentrations
Mercer 2021 EVE Which animal has shown increased sensitivity to cannabinoids due to higher cannabinoid receptor distribution in the brain?
A) Horses
B) Cats
C) Dogs
D) Rats
C) Dogs
Fogle 2021 EVE Ex vivo Cox1 and Cox2 inhibition - What is the primary advantage of COX-2 selective NSAIDs like firocoxib?
A) They completely inhibit COX-1.
B) They avoid COX-1 inhibition and reduce side effects.
C) They have a shorter half-life.
D) They only inhibit COX-1.
B) They avoid COX-1 inhibition and reduce side effects.
Fogle 2021 EVE Ex vivo Cox1 and Cox2 inhibition -Which NSAID had the longest plasma half-life in this study?
A) Phenylbutazone
B) Flunixin meglumine
C) Meloxicam
D) Firocoxib
D) Firocoxib
plasma half-lives of the drugs were 5.97 hours for pbz 4.74 hours for fluni 8.24 hours for meloxicam, and 47.42 hours for firocoxib.
Fogle 2021 EVE Ex vivo Cox1 and Cox2 inhibition - Which of the following drugs showed significantly higher TXB2 levels after the third dose compared to flunixin meglumine and phenylbutazone?
A) Firocoxib and phenylbutazone
B) Meloxicam and firocoxib
C) Phenylbutazone and meloxicam
D) Flunixin meglumine and phenylbutazone
B) Meloxicam and firocoxib
