Effect of Aminocaproic Acid on the Severity of Exercise-Induced Pulmonary Hemorrhage
ACVIM 2008
M.M. Durando; E.K. Birks
University of Pennsylvania, School of Veterinary Medicine
Kennett Square, PA, USA

Exercise-induced pulmonary hemorrhage (EIPH) is considered to be an important cause of reduced performance in racehorses. Numerous treatments are used to attempt to minimize EIPH and/or the consequences of bleeding. However few controlled scientific studies have evaluated the efficacy of most of the available treatments. The diuretic furosemide is commonly administered to limit EIPH. Because of perceived ineffectiveness of furosemide to prevent EIPH, the anti-fibrinolytic drug aminocaproic acid (Amicar®) has also been administered along with furosemide, in an attempt to decrease EIPH severity. This study was conducted to determine if the administration of Amicar® along with furosemide would have any effect on the incidence/severity of EIPH in TB racehorses.

Horses were voluntarily enrolled by their trainers and were required to participate in 2 races as part of the study. Participating horses received one of two treatments prior to each race in a blinded, randomized cross-over design. Treatments consisted of either furosemide + Amicar®) (F+A; 250 mg furosemide i.v. 4 hours prior to racing and 5 gm Amicar®) i.v. 2 hr prior to racing) or furosemide only (F). Of 43 horses completing both treatments, 22 received F+A and 21 received F as the initial treatment. All horses had videoendoscopy of their airways and bilateral bronchoalveolar lavage (BAL) 12-15 hours following each race. Lungs were lavaged with 200 ml sterile saline per side. Recovered BAL fluid was evaluated by clinical pathologists blinded to treatment, for RBC and nucleated cell counts, and WBC differential analysis. Data were analyzed by repeated measures ANOVA to examine possible effects of treatment and/or race order on RBC number, WBC number and differential cell count. Significance was P < 0.05.

No significant effect of treatment or race order was observed for total RBC numbers (mean±SEM, F 1271±530 vs F+A 1550±442 cells/µl, P=0.62). However, the right side had significantly greater RBC numbers than the left side after both treatments (mean±SEM right vs left; F 1833±999 vs 410±124 cells/µl and F+A 2330±703 vs 415±119 cells/µl, P<0.01). No significant effect on WBC numbers was observed with regard to either treatment/race order (right P=0.77, left P=0.47), or lung side (P=0.29).

This study demonstrated that pre-race administration of Amicar® in addition to the diuretic furosemide had no effect on the severity of EIPH, compared with furosemide alone. WBC enumeration and distributions were also not affected by treatment. Interestingly, significantly more RBC were recovered from the right lung. Whether this is related to the direction of the races or the predominant lead the horse races on, is unknown. Additional studies with larger numbers of horses racing at various racetracks are warranted. Variations in race direction/configuration and surfaces would also be important to study.

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Mary Durando

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