Acute laminitis in horses Flashcards
What is laminitis?
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
What can happen to the Pedal bone?
Tip of the Pedal bone can go through sole - rotation or the whole structure sinks
What are some factors that increase the risk of laminitis?
- 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)
What are some predisposing factors for pasture-associated laminitis?
- Pony
- Season (spring/summer) - grass growing
- Gender (females predisposed)
- Increasing age
- Obesity
- Insulin resistance
What are the three stages in the pathogenesis of laminitis?
- Developmental (contact with trigger, lasts up to 72 hours - No CS though
- Acute laminitis - see CS
- Resolution or chronic laminitis - prolonged changes + painful
What is the role of the ECM in the laminae?
Responsible for the maintenance of structural support, movement, growth, remodeling, and healing along with the modulation of cytokines, inflammation, healing, and cell migration
Why can laminar separation occur following an insult?
Failure of epithelial adhesion molecules (hemidesmosomes) which attach the epidermal cells to the basement membrane
LOSS OF FUNCTION
What types of insults can cause laminar separation?
Inflammatory and/or hypoxic cellular injury
How can inflammation predispose to laminitis?
Systemic inflamm response that accompanies hindgut carbohydrate overload - initiates lamellar inflammatory events
What are two endocrinological disorders that may play a role in the predisposition to laminitis in certain horses?
- Excess glucocorticoids (PPID)
- Insulin resistance (EMS)
What will exacerbate insulin resistance in horses?
Increased CHO consumption
Also vasoactive
How does EMS predispose to laminitis?
Changes in insulin signalling, inflamm cytokines and endothelial dysfunction caused by adipose tissue-derived mediators
What vascular events occur in the early stages of laminitis?
Digital veno-constriction and consequent laminar oedema
Venoconstriction caused by platelet activation/platelet neutrophil activation = release of vasoactive mediator 5-HT
What are the aims when approaching a suspected case of laminitis?
- Make a definitive diagnosis
- Determine underlying cause
- Determine if likely to recover to expected level of soundness
How is a diagnosis of laminitis reached?
Clinical signs, RADs, Endocrine tests
What are the cs of laminitis?
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
What can you see on Rads for laminitis?
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
What endocrine tests can you carry out for laminitis?
PPID -CS, Basal ACTH, Dex suppression (NOT in autumn), TRH stim test
EMS- history, CS, Demostration of IR
What are three therapies that can be done to medically treat laminitis?
Medical emergency!!
- Analgesia
- Vasodilation/vasoconstriction
- Foot support
What can be used for analgesia in laminitic horses?
- NSAIDs (PBZ, flunixin, etc)
- Opiates (morphine, pethadine, fentanyl)
How can you use vasodilation/vasoconstriction to treat laminitis?
Controversial
Vasodilator drug to affect digital blood flow is ACP - sedative effect, take weight off feet
Vasoconstriction - use ice
What is the main treatment for PPID?
Pergolide
What is the main treatment for EMS?
Weight loss, exercise, may or may not use pharmacological agents (Thyro-L, metformin)
How can you support the feet?
- 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
What management changes should happen for laminitis cases?
Box rest
Changing diet - no grass, poor quality hay, no or minimal concentrates (HiFi, unmollassed sugar beet + oil (extra energy)
What is the prognosis for laminitic cases?
Depends on clinical signs and radiographic signs - ie sinker - poor prognosis
Worse if has a history of laminitis
How can you prevent laminitis?
For pasture-associated laminitis - reduce overconsumption of NSC
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?
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
What are some mineral supplements that can be added to the diet to help with insulin levels?
- Cinammon
- Magnesium
- Chromium
What grazing options can you consider for laminitic cases?
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
