Heaves: Recurrent Airway Obstruction Exam 2 Flashcards
What did RAO used to be called?
COPD: chronic obstructive pulmonary disease (now this is incorrect)
What is RAO/Heaves/Asthma?
inflammatory obstructive airway disease that afflicts older horses
What age does RAO affect?
horses 7 years old or older
What is RAO initiated by?
inhalation of organic dusts (dusts associated with hay, bedding, etc.)
Organic dusts
-allergens
-endotoxins
-molds
-other particles that can initiate lung inflammatory response
Can RAO be cured?
no, it can only be managed
How does a horse respond to the organic dusts?
very severe inflammatory process and bronchoconstriction
Where is RAO more prevalent?
in the northern hemisphere (horses are stabled more and fed more hay)
Is RAO genetic?
there is an apparent genetic component (horses housed in the same environment may get heaves while others may not)
What is the first step in the RAO disease process?
a massive influx of neutrophils invade the airway lumen
When does the first step of the RAO disease process happen?
when susceptible horses are moved from pasture to stable and fed hay
-it happens within 6-8 hours
What is the second step of the RAO disease process?
inflammatory mediators (IL, cytokines, leukotrienes) act on cholinergic nerves and are responsible for bronchospasm
What is the third step of the RAO disease process?
increased mucus production and thick viscosity leads to mucus accumulation (to capture the dust particles)
What is the fourth step of the RAO disease process?
airway wall thickening: edema (acute) - swelling that comes from inflammation - and remodeling (chronic) - the muscle becomes thicker (hypertrophy, painful as muscling increases)
Hyperresponsiveness
an exaggerated response
What is a horse’s immune response to organic dust particles with RAO?
a hyperresponse
What symptom of heaves is more important to treat?
the inflammatory process (more important than bronchoconstriction)
What are the clinical signs of an acute episode of heaves?
-flared nostrils
-increased resp. rate (14-16/min)
-use of abdominal muscles to assist expiration
-anxious appearance
-intolerance to exercise
Clinical signs of advanced stages of heaves:
-struggle to breath
-unable to eat
-weight loss
-heave lines (from consistent used of abdominal support in expiration)
How is heaves diagnosed?
based on history and typical clinical signs
What disease is RAO similar to?
summer-pasture associated obstructive pulmonary disease (warm and humid weather)
What is the first step you have to take to manage heaves?
changing and controlling the horses environment
What are the 3 principles of heaves management and prevention?
- environmental control
- corticosteroids to reduce inflammation
- bronchodilators to relieve respiratory distress
What can a horse with heaves not eat?
dry hay
Where does a horse with heaves have to live?
outdoors 24/7
What is the number one environmental elimination that needs to happen?
eliminating hay and bedding dust (even a little can trigger a heaves attack)
If it is impossible to keep horse outside year-round what measures should be taken?
-soak hay
-feed grass silage or pelleted feed
-keep horse closer to barn door
-use cardboard or flax bedding
-don’t blow or sweep barn aisles while horse is inside
Why are NSAIDs contraindicated?
they decrease production of PGE2, a prostaglandin that inhibits inflammation and prevents bronchospasms
What do corticosteroids do for heaves?
prevent pro-inflammatory process, prevent down-regulation of B2-adrenoceptors, increase appetite
How should dexamethasone be used in treatment?
gradually reduce dose to minimum necessary
-there should be improvement in 3-7 days (on lowest dose possible)
What two drugs used for treatment are not FDA approved?
-beclomethasone
-fluticasone
Beclomethasone and fluticasone treatment
must be given by use of aeromask (if the obstructions prevents inhalation (too severe) bronchodilators may have to be given first)
What are bronchodilators useful for?
acute heaves attacks
What are common Aeromask bronchodilators given?
-albuterol
-pirbuterol
-salmeterol
What is the common bronchodilator given (not with aeromask)?
clenbuterol (ventipulmin) - has side effects like heart palpitations
What are the two long lasting bronchodilators and how long do they last?
-clenbuterol and salmeterol
-6-8 hrs.
What are the two short acting bronchodilators and how long do they last?
-albuterol and pirbuterol
-1-2 hrs.
Side effects of bronchodilators:
-sweating
-trembling
-tachycardia
-agitation
Which bronchodilators are side effects mostly seen with?
systemic administrated drugs (clenbuterol) not drugs given via inhalation
B-1 =
heart
B-2 =
lungs
Prognosis depends on what?
the stage of disease at the time of diagnosis and the level of care provided to the horse
What is important to do all the time?
prevent; continual prevention of exposure to organic dusts
When should bronchodilators be used?
during acute heaves attacks or right before exercise
Horses with heaves can do what level of work when under the right conditions?
low-moderate work
