HEMOLYSIS AND HYPERCOAGULABLE STATE IN STANDARDBRED HORSES DURING A SHORT TERM - HIGH SPEED COMPETITION

In human medicine exercise-induced hemolysis and hemostatic alterations are commonly reported. The aetiology can be ascribed to various factors but oxidative stress seems to be the most important. Sports anemia could be a possible result of these changes during training or competition periods in humans. In equine medicine, targets of exercise-induced damage have been studied during exercise tests and occasionally during races. The oxidative response, with particular attention to blood rheology, plasma muscular enzymes (PMEs) and iron metabolism alterations, has been described. The aim of this study was to evaluate clinicopathological data associated to a racing competition (short-term, high-intensity) with a focus on hemostatic alterations and the potential erythrocyte damage. Thirty-four Standardbred racing horses (3 years old), participating at high speed races for a total distance of 1660 m in about 2 minutes, were studied. Three different competitions were evaluated and venous blood samples were collected immediately before the race, and within 30 minutes by the end of competition. CBC, Acute Phase Proteins, biochemical and hemostatic parameters including Uric Acid (UA), Haptoglobin (Hp), Fibrinogen (Fib) and D-Dimer (DD), were evaluated. DD and Hp were assayed by immuno-turbidimetric methods. The statistical analyses were carried out using one-way analysis of variance (ANOVA) with repeated measurements to compare variables pre- and post-competition. The post exercise data were corrected using an estimation of the plasma volume contraction according to the individual Albumin (Alb) concentration increase. A significant plasma volume reduction after the race was found (mean Alb +6.86%, p<0.01). Similarly, the mean hematocrit value (HCT) increased (+25.35%, p<0.01), however not proportionally to Alb. A potential influence of splenic contraction on these data should be considered; therefore the HCT was not utilized for the data correction. Once adjusted for plasma volume contraction, post competition Fib concentrations were significantly lower than pre-competition ones (mean -3.71%, p<0.01). Furthermore, DD concentrations were highly increased after competition (mean +22.79%, p<0.01). These results may suggest that this type of race induces a significant coagulation and fibrinolysis activation. The Hp concentrations decreased after the competition (mean -8.7%, p<0.01) and this result could be explained by an intravascular hemolysis associated to the race, as reported in human beings. Our study confirms a significant alteration of PMEs and UA linked to the race in horses and probably related to the oxidative response. Further studies are needed to better clarify pathogenesis and clinical relevance of these alterations in equine medicine.