Prevalence and severity of exercise-induced pulmonary hemorrhage in 2-year-old Thoroughbred racehorses and its relationship to performance

Background: Little has been reported regarding the prevalence and severity of exercise-induced pulmonary hemorrhage (EIPH) in 2-year-old Thoroughbred racehorses. Objectives: Evaluate EIPH prevalence and severity and its association with performance, speed index, furosemide administration, race distance, and track surface. Animals: A total of 830 2-year-old Thoroughbreds. Methods: Prospective blinded observational study. Videoendoscopy was performed 30 to 60 minutes postrace at 15 American racetracks. Three blinded observers independently assigned an EIPH grade (0-4) to each video, and prevalence and severity of EIPH were determined. Relationships of EIPH grade to performance, speed index, race distance, track surface, and prerace administration of furosemide were evaluated using Pearson's chi-squared test for categorical variables and analysis of variance (ANOVA) for numerical variables. Multivariable logistic regression assessed relationships between EIPH prevalence and severity, respectively, and the aforementioned independent variables. A P < .05 was considered significant. Results: A total of 1071 tracheoendoscopies were recorded. The EIPH prevalence was 74% and for EIPH grade >= 3 was 8%. Speed index (P = .02) and finishing place (P = .004) were lower with EIPH >= 3. The EIPH prevalence and severity were lower at 2 tracks where postrace tracheoendoscopy was mandatory rather than voluntary (P < .001). Probability of observing EIPH was negatively associated with speed index (P = .01) at tracks where postrace tracheoendoscopy was mandatory. Prerace furosemide administration decreased the probability of EIPH occurrence (P = .007) and severity (P = .01) where study participation was voluntary. Conclusions and clinical importance: Prevalence and severity of EIPH in 2-year-old racehorses were consistent with that of older racehorses. An EIPH grade >= 3 was associated with decreased performance. Prerace furosemide administration was associated with a decreased likelihood, but not severity, of EIPH at most tracks.