Fluid administration attenuates the haemodynamic effect of frusemide in running horses.

This research study examines the dampening effects of fluid administration on the haemodynamic responses of exercising horses to frusemide, a diuretic medication. The study finds that administering fluids diminishes the impact of frusemide on exercising horses’ cardiovascular responses and regulation of their blood volume.

Design of the Study

• The study focuses on understanding the impact of blood volume repletion, or refilling, after administering frusemide on the right atrial and pulmonary artery pressure responses of exercising horses.
• Scientists conducted this examination using an incremental exercise test on six Standardbred mares.
• The horses underwent three treatment scenarios, each in a cross-over design: one with an isotonic saline solution, one with the diuretic frusemide (at a dose of 1 mg/kg, intravenously), and another scenario with frusemide administration succeeded by lactated Ringer’s solution (given at a dose of 12 ml/kg, intravenously) three hours later.
• Three and a half hours after the administration of saline or frusemide, the horses underwent a standard exercise test.

Effects of Frusemide and Fluid Administration

• Frusemide had a significant impact on the right atrial and pulmonary artery pressure of the exercising horses, as well as their plasma atrial natriuretic peptide (ANP) responses.
• ANP is a powerful vasodilator, meaning it works to relax and widen blood vessels, which in turn releases water and sodium to the urine, reducing blood volume.
• Fluid administration, conversely, decreased the mares’ plasma total protein concentration both when resting and during running. Simultaneously, it also neutralized the effects of frusemide on the haemodynamic and ANP responses during exercise.

Conclusions

• The results of this study suggest that the haemodynamic effect of frusemide in running horses is largely mediated by a reduction in plasma and blood volume. Thus, the practice of fluid administration has the potential to mitigate these particular effects of Frusemide.
• This research advances our understanding of the physiological responses of horses to exercises especially under the influence of medication and how fluid administration can work to modify these effects.