Effect of frusemide on transvascular fluid fluxes across the lung in exercising horses.
Authors: Vengust M, Kerr C, Staempfli H R, Pringle J, Heigenhauser G J, Viel L
Journal: Equine veterinary journal
Summary
# Editorial Summary Exercise-induced pulmonary haemorrhage (EIPH) remains a significant concern in racehorses, and frusemide is routinely administered to mitigate fluid shifts across lung capillaries during high-intensity work—yet the mechanism by which it operates during actual exercise has been poorly characterised. Vengust and colleagues conducted a crossover trial with six race-fit Standardbred horses, administering either 250 mg intravenous frusemide or placebo four hours before high-speed treadmill exercise to fatigue, measuring arterial and venous blood parameters alongside cardiac output, oxygen uptake and carbon dioxide elimination to calculate transvascular and erythrocyte fluid fluxes across the lungs. Whilst cardiac output at fatigue was significantly reduced in the frusemide-treated group (301.8 versus 336.5 l/min), the drug produced no statistically significant difference in either erythrocyte fluid flux or transvascular fluid flux during exercise—both measured at approximately 12–15 l/min at fatigue in both groups. The finding that frusemide dampens cardiac output without meaningfully attenuating the pulmonary fluid shifts that directly precipitate EIPH challenges assumptions about its efficacy at this dose, suggesting that current dosing protocols may require reconsideration or that alternative mechanisms underlying EIPH management warrant investigation.
Read the full abstract on PubMed
Practical Takeaways
- •Frusemide 250 mg IV did not reduce pulmonary fluid leakage during high-intensity exercise in this study, questioning its efficacy for EIPH prevention at this dose
- •Despite reducing cardiac output, frusemide did not measurably improve transvascular fluid dynamics, suggesting alternative mechanisms or higher doses may be needed
- •Current data do not support frusemide as an effective treatment for regulating pulmonary pressures and fluid fluxes during racing in horses
Key Findings
- •Frusemide 250 mg IV did not significantly reduce erythrocyte fluid flux (J(ER)) during exercise compared to placebo (11.6 ± 2.2 vs 14.6 ± 2.3 l/min at fatigue, P = 0.6)
- •Transvascular fluid flux (J(V-A)) was not significantly different between frusemide and control groups during exercise (12.0 ± 2.2 vs 14.9 ± 2.3 l/min at fatigue, P = 0.8)
- •Frusemide significantly reduced cardiac output at fatigue compared to placebo (301.8 ± 8.5 vs 336.5 ± 15.6 l/min, P < 0.01)
- •At the tested dose of 250 mg, frusemide does not appear effective at regulating pulmonary transvascular forces during exercise in horses