Equine Flash Notes - Recurrent Airway Obstruction Flashcards
what is the classic signalment of a horse with RAO?
mature horses over 7 years old with no sex predilection with exposure to organic dust, molds (poorly cured hay), mites, & endotoxins
what is the etiology of RAO? how is it diagnosed?
recurrent allergen induced neutrophilic inflammation of lower airways - diagnosed by thoracic auscultation, BAL with non-degenerate neutrophils, curschmann’s spirals (can’t differentiate between IAD with this), arterial blood gas, bronchodilator test, endoscopy, & pulmonary function testing
what are 4 ways to treat & prevent recurrence of RAO?
minimize allergen exposure, control airway inflammation, relieve airflow obstruction, & environmental changes
what is the primary difference between RAO & IAD?
only definitive difference from IAD is tachypnea at rest with RAO - not with IAD
what is the pathogenesis of RAO?
recurrent allergen induced neutrophilic inflammation of lower airways - diagnosed by thoracic auscultation, BAL with non-degenerate neutrophils, curschmann’s spirals (can’t differentiate between IAD with this), arterial blood gas, bronchodilator test, endoscopy, & pulmonary function testing
horses in what geographic locations are more commonly affected by RAO?
northern USA, europe - primarly stabled horses, & southeastern USA more prevalent in horses on pasture in the summer & fall
what is the most important component of treatment for a horse with RAO?
environmental changes
what is the goal of treatment for a horse with RAO?
minimize allergen exposure, controlling airway inflammation, & relieving airflow obstruction
what is heard on thoracic auscultation in a horse with RAO?
at rest & with rebreathing bag - expiratory wheezes, crackles, & tracheal rattle
what is seen on arterial blood gas analysis in a horse with RAO?
hypoxemia (decrease PaO2) & increased PaCO2 in chronic cases
what do you expect results on a bronchodilator test to be in a horse with RAO?
after administration of atropine, marked imrpovement in signs observed within 10 minutes
what results do you expect on pulmonary function testing in a horse with RAO?
treadmill with endoscopy - decreased airway compliance, increased pulmonary resistance, & increase in transpulmonary pressure during respiration
what is seen on endoscopy in a horse with RAO?
excessive mucopurulent tracheal exudate
how is pasture associated heaves treated?
change to a different pasture or move the horse indoors to a well ventilated stall
how is heaves associated with an indoor environment treated?
complete turnout is critical
what steroids are used for treating RAO?
oral prednisolone, parenteral dexamethasone for respiratory distress horses, & inhaled steroids such as fluticasone or nebulized dexamethasone
what is the benefit of using bronchodilators for horses with RAO?
relaxes smooth airway muscle - can use oral or inhaled b-2 agonists, and for emergency relief, atropine (anticholinergic)
what is the classic history of a horse with RAO?
signs that recur & wax/wane in response to season, specific food/allergen exposure
what are the clinical signs associated with RAO?
afebrile, exercise intolerance, coughing during exercise, exaggerated end-expiratory effort in a resting horse, mucopurulent discharge, & heave line
