Evaluation of hemorheologic variables as implications for exercise-induced pulmonary hemorrhage in racing thoroughbreds.

This research studies the changes in blood and flow characteristics in 49 Thoroughbred racehorses before and after racing, to assess potential links to exercise-induced pulmonary hemorrhage. Findings revealed significant changes in various measurements post-race, but these variables could not predict whether a horse may suffer from bleeding.

Study Overview

• The study observed hemorheologic (blood flow) variables in 49 Thoroughbred racehorses before and after completion of a competitive race to evaluate potential implications in exercise-induced pulmonary hemorrhage (EIPH) – a common but still poorly understood disease among racehorses characterized by bleeding from the lungs during intense exercise.
• Researchers were particularly interested in elements such as red blood cell (RBC) count, hemoglobin concentration, packed cell volume (PCV), and measures of blood viscosity, among other variables.

Key Findings

• The study found major changes between pre-race and post-race hematologic and rheologic parameters. Specifically, the average post-race values for RBC count, hemoglobin concentration, and PCV saw an increase ranging from 58 to 61%, and blood viscosity increased 2 to 3 times.
• The count of echinocytes (abnormally shaped red blood cells) was seen to increase by a significant 162% after the race compared to pre-race values.
• Significant, but statistically smaller changes were observed in values relating to mean corpuscular hemoglobin concentration (average amount of hemoglobin per red blood cell), red cell distribution width (variability of red blood cell size), plasma total protein concentration, total white blood cell (WBC) count, and counts of specific types of WBCs, like neutrophils and lymphocytes.

Findings’ Implications

• These shifts highlight the substantial impact that intense exercise can have on a horse’s hematologic and rheologic profile, particularly the surge in RBC count, echinocyte numbers, and blood viscosity, which can contribute to altered rheology and potentially influence the onset of EIPH.
• However, the research revealed that these measured variables were not effective in predicting whether a horse was a “bleeder” (a horse that experienced EIPH), whether they were treated with furosemide (a diuretic used to prevent or mitigate EIPH) or not, or a “non-bleeder” (a horse that did not experience EIPH).
• This inability to predict EIPH status indicates that the relationship between these hemorheologic parameters and EIPH is complex and not straightforward. Thus, further research is necessary to uncover more about the mechanisms behind EIPH and design preventive measures.