Acute laminitis in horses

Question 1

What is laminitis?

Answer 1

Failure of the attachment of the epidermal cells of the epidermal (insensitive) laminae to the underlying basement membrane of the dermal (sensitive) laminae

Hoof to Pedal bone

Question 2

What can happen to the Pedal bone?

Answer 2

Tip of the Pedal bone can go through sole - rotation or the whole structure sinks

Question 3

What are some factors that increase the risk of laminitis?

Answer 3

• Diseases characterized by sepsis and systemic inflammation (post colic)
• Endocrine disorders - PPID, EMS
• Mechanical overload - too much pressure on PB + laminae
• Access to pasture
• Metabolic disorders
• Retained placental membranes (mares)

Question 4

What are some predisposing factors for pasture-associated laminitis?

Answer 4

• Pony
• Season (spring/summer) - grass growing
• Gender (females predisposed)
• Increasing age
• Obesity
• Insulin resistance

Question 5

What are the three stages in the pathogenesis of laminitis?

Answer 5

1. Developmental (contact with trigger, lasts up to 72 hours - No CS though
2. Acute laminitis - see CS
3. Resolution or chronic laminitis - prolonged changes + painful

Question 6

What is the role of the ECM in the laminae?

Answer 6

Responsible for the maintenance of structural support, movement, growth, remodeling, and healing along with the modulation of cytokines, inflammation, healing, and cell migration

Question 7

Why can laminar separation occur following an insult?

Answer 7

Failure of epithelial adhesion molecules (hemidesmosomes) which attach the epidermal cells to the basement membrane
LOSS OF FUNCTION

Question 8

What types of insults can cause laminar separation?

Answer 8

Inflammatory and/or hypoxic cellular injury

Question 9

How can inflammation predispose to laminitis?

Answer 9

Systemic inflamm response that accompanies hindgut carbohydrate overload - initiates lamellar inflammatory events

Question 10

What are two endocrinological disorders that may play a role in the predisposition to laminitis in certain horses?

Answer 10

• Excess glucocorticoids (PPID)

- Insulin resistance (EMS)

Question 11

What will exacerbate insulin resistance in horses?

Answer 11

Increased CHO consumption

Also vasoactive

Question 12

How does EMS predispose to laminitis?

Answer 12

Changes in insulin signalling, inflamm cytokines and endothelial dysfunction caused by adipose tissue-derived mediators

Question 13

What vascular events occur in the early stages of laminitis?

Answer 13

Digital veno-constriction and consequent laminar oedema

Venoconstriction caused by platelet activation/platelet neutrophil activation = release of vasoactive mediator 5-HT

Question 14

What are the aims when approaching a suspected case of laminitis?

Answer 14

1. Make a definitive diagnosis
2. Determine underlying cause
3. Determine if likely to recover to expected level of soundness

Question 15

How is a diagnosis of laminitis reached?

Answer 15

Clinical signs, RADs, Endocrine tests

Question 16

What are the cs of laminitis?

Answer 16

Lameness affecting 2 or more limbs
Characteristic stance of leaning on back on heels
Bounding digital pulses
Increased wall temp
Pain on hoof tester pressure at the frog region
Palpable depression at the coronary band

Question 17

What can you see on Rads for laminitis?

Answer 17

SANK P3 (nerve blocks to help?)

-Pedal bone rotation- Soft where Pedal bone should be
-Founder distance -sinking
-Angle between line of P3 and wall of hoof (should be parallel)
-Decreased sole thickness
Take Lateromedial radiographs of feet

Question 18

What endocrine tests can you carry out for laminitis?

Answer 18

PPID -CS, Basal ACTH, Dex suppression (NOT in autumn), TRH stim test
EMS- history, CS, Demostration of IR

Question 19

What are three therapies that can be done to medically treat laminitis?

Answer 19

Medical emergency!!

• Analgesia
• Vasodilation/vasoconstriction
• Foot support

Question 20

What can be used for analgesia in laminitic horses?

Answer 20

• NSAIDs (PBZ, flunixin, etc)

- Opiates (morphine, pethadine, fentanyl)

Question 21

How can you use vasodilation/vasoconstriction to treat laminitis?

Answer 21

Controversial
Vasodilator drug to affect digital blood flow is ACP - sedative effect, take weight off feet
Vasoconstriction - use ice

Question 22

What is the main treatment for PPID?

Answer 22

Pergolide

Question 23

What is the main treatment for EMS?

Answer 23

Weight loss, exercise, may or may not use pharmacological agents (Thyro-L, metformin)

Question 24

How can you support the feet?

Answer 24

• Increase bedding depth and all the way to the door (on box rest- will stand by the door)
• Frog support - bandages, lily pads
• Frog and sole support - styro foam, dental impression shoes

Question 25

What management changes should happen for laminitis cases?

Answer 25

Box rest
Changing diet - no grass, poor quality hay, no or minimal concentrates (HiFi, unmollassed sugar beet + oil (extra energy)

Question 26

What is the prognosis for laminitic cases?

Answer 26

Depends on clinical signs and radiographic signs - ie sinker - poor prognosis
Worse if has a history of laminitis

Question 27

How can you prevent laminitis?

Answer 27

For pasture-associated laminitis - reduce overconsumption of NSC

Question 28

a) When does NSC content of pasture decrease?
b) When does NSC content of pasture increase?
c) What can be done to high quality hay to decrease NSC content?

Answer 28

NSC- non-structural carbohydrates

a) When the plant is growing.
b) When the plant is photosynthesizing (high light intensity, low temp, lack of water)
c) Soak hay in water for at least 20 minutes; not reliable however

Question 29

What are some mineral supplements that can be added to the diet to help with insulin levels?

Answer 29

• Cinammon
• Magnesium
• Chromium

Question 30

What grazing options can you consider for laminitic cases?

Answer 30

Zero grazing - turn out in dirt field - esp for ponies
Turn out late at night, early am (no sun - no photosynthesis)
Restrict grazing in spring/autumn