blood by endoscopy of the airways is the gold standard for the diagnosis of EIPH and grading its severity. Epistaxis following exercise is strongly suggestive of EIPH (moderate quality evidence). However, the other clinical signs are not reliable signs of EIPH and the evidence of their association with EIPH is of very low quality. Treadmill studies have shown impaired blood-gas exchanges and higher blood lactate in horses with EIPH during exercise but the quality of evidence is very low.
bleeding by counting red blood cells in bronchoalveolar lavage fluid collected 1 hour after exercise but the strength of evidence is small because of the small sample size (3 studies; n = 46) and potential bias. Many other drugs have been investigated as prophylaxis for EIPH but all studies provide very low-quality evidence because of small sample size, exercise conducted on treadmill, or EIPH severity was not assessed. Furthermore, none of those studies demonstrated mitigating effects on EIPH.
Sudden death in racehorses occurs in 0.08-0.29 horses per 1000 starts. In a case series of Thoroughbreds that died suddenly within 1 hour of racing or training, 35% of deaths with a known cause were attributed to pulmonary hemorrhage (low-quality evidence). However, pulmonary hemorrhage may have been the primary cause of death or resulted from another cause of death (e.g. cardiac failure). In addition, there is no evidence that EIPH increases the risk of sudden death.
Four treadmill studies have shown that nasal strips resulted in a reduction of red blood cells in bronchoalveolar lavage fluid collected 1 hour after exercise, however, the strength of evidence is low.
Severe EIPH (grade 4 or epistaxis) is associated with shorter racing career but mild to moderate EIPH is not (moderate quality evidence). Studies have suggested that EIPH is a progressive condition related to career duration rather than age of the horse.
Effects of EIPH on Performance: Performance is difficult to measure in racehorses because there are many horse-related factors (e.g. gender, age, fitness level, horse quality) and external factors (e.g. jockey, track conditions, distance, environmental conditions, horse field) that may influence the outcome of the race. Therefore, it is important that studies attempt to control those factors in the analysis of data in order to compare performance between horses. Studies of higher quality conducted during normal racing have shown that EIPH is associated with worse-finishing (inferior position and farther-behind winner) and lower race earnings (moderate-quality evidence). Lower-quality studies failed to demonstrate an effect of EIPH on performance. There, lowquality evidence of a dose-response relationship between EIPH and performance, that is to say more severe EIPH, is associated with worse performance.
Prophylaxis for EIPH: There are no published studies on the effects of treatments aimed at decreasing severity of EIPH or progression of lung lesions in subsequent races. Similarly, no studies have examined if treatments or interventions during training may alleviate EIPH during subsequent racing. Therefore, we reviewed publications describing drugs or interventions administered prior to exercise in order to prevent EIPH. The outcome of interest (EIPH) was measured either by endoscopic visualization of blood in airways (yes/no or grading scale) or by quantifying red blood cells in bronchoalveolar lavage fluid following strenuous exercise. There is preponderance of evidence that administration of furosemide (0.5-1 mg/kg IV) 4 hours prior to exercise decreases the severity and the incidence of EIPH (high-quality evidence). The strongest evidence is coming from studies that quantified EIPH by grading bleeding in the trachea during endoscopy 1 hour following racing (2 studies; 422 horses). Some studies quantified WWW.FAEP.NET |
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Effects of Furosemide on Performance: Most studies conducted on racetracks have evaluated performance by measuring adjusted race time to cover a given distance. Treadmill studies have used distance covered or time to fatigue. The preponderance of evidence is that furosemide administered IV 4 hours prior to racing improves performance (moderate-quality evidence) and the magnitude of the effect varies from 0.12 to 1.1 s faster time per mile compared to horses not treated with furosemide.
References: 1. Hinchcliff KW, Couetil LL, Knight PK, Morley PS, Robinson NE, Sweeney CR, et al. Exercise induced pulmonary hemorrhage in horses: American College of Veterinary Internal Medicine consensus statement. J Vet Intern Med 2015 May;29(3):743–58. 2. Guyatt G, Oxman AD, Akl EA, Kunz R, Vist G, Brozek J, et al. GRADE guidelines: 1. Introduction-GRADE evidence profiles and summary of findings tables. J Clin Epidemiol. 2011 Apr;64(4):383–94.
Laurent Couetil, DVM, PhD, DACVIM (LA) Dr. Couetil is a professor of large animal medicine at Purdue University. He obtained his veterinary degree from the French National Veterinary School of Alfort and then worked for 6 years in equine private practice in Chantilly, France. Dr. Couetil completed a large animal medicine residency at Tufts University and a PhD in respiratory physiology at the University of Liege, Belgium. Dr. Couetil has been a faculty member at Purdue University College of Veterinary Medicine since 1995, where he is Director of the Equine Research Program and of the Equine Sports Medicine Center. Dr. Couetil is the current President of the Large Animal Internal Medicine specialty of the American College of Veterinary Internal Medicine (ACVIM). His research interest is investigating the causes and treatment of poor performance in athletic horses, in particular chronic respiratory diseases.
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