Last Updated on March 29, 2022 by Allison Price
EIPH is a common condition in racehorses, as well as horses involved in equine sports such as polo, barrel racing and 3-day events. EIPH is rare in horses that have Epistaxis (5%). Endoscopic examination can identify blood in the tracheobronchial trees in between 45% and 75% of racehorses. Hemorrhage can be detected in >90% racehorses by cytologic examination.
Pathophysiologic mechanisms for pulmonary hemorhage include high pulmonary blood pressures during exercise maximal, which can cause thickening of the pulmonary vein walls, decreased luminal diameter, and an increase in intravascular pressure at level of the pulmonary capillaries.
Exercise-induced pulmonary hemorhage
EIPH can be confirmed by endoscopic observation of blood in the lungs for 30 to 90 minutes after exercise. Endoscopic examination must exclude other sources of hemorhage in upper airways, such as guttural pouch mycosis and ethmoid hemomatoma . EIPH can be suspected if the horse is unable to exercise. Cytologic examination of bronchoalveolar fluid is performed for semiquantitative assessment. These cells can be identified by staining that highlights iron-containing pigments (Prussian Blue). Thoracic radiography demonstrates alveolar or mixed alveolar-interstitial opacities in the caudodorsal lung fields; however, radiographic examination of the thorax has little impact on the diagnosis or management of EIPH.
Control and Treatment:
Furosemide decreases the severity and incidence of EIPH in Thoroughbred racehorses. Furosemide is equally effective in improving race performance for horses with and without EIPH. This suggests that furosemide may also be used to enhance performance through mechanisms not related to EIPH. The application of nasal dilator band reduces RBC counts from affected horses while they are running on a treadmill 33%. Other treatments such as procoagulant drugs (eg, vitamin K and conjugated estrogens), antihypertensive medications (pentoxyphylline), and rheologic agents(pentoxyphylline), bronchodilators (hepseridin–citrus bioflavinoids), have not been shown to be of therapeutic benefit.