Effects of frusemide on pulmonary capillary pressure in horses exercising on a treadmill.

The research study tests if the drug frusemide lessen the pressure in the lung’s small blood vessels (pulmonary capillaries) in horses when they’re exercising at maximum effort. The results indicate that frusemide does effectively decrease such pressures potentially limiting fluid accumulation in lungs during intense exercise thus could protect against exercise-induced pulmonary haemorrhage.

Research Methodology

• The study was conducted on seven horses who were administered either saline (control treatment) or frusemide.
• The dosage of frusemide given was 2mg/kg of horse body weight.
• Each treatment was given in a random order to each horse with a gap of at least one week between administrations
• The horses were tested in different physical states: resting, intensive exercise at 75%, 90% and 100% of their maximum heart rates, and walking 2 minutes after maximum exercise.
• The tests during exercise were done continuously for about 3 minutes with walking intervals between them.
• Several physiological parameters like pulmonary arterial pressure, pulmonary capillary pressure, pulmonary artery wedge pressure, breathing rate, heart rate and arterial blood gas tensions were recorded in each level of exercise.
• Pulmonary arterial wedge and pulmonary capillary pressures were determined from the pulmonary arterial waveform after dynamic occlusion (temporary blockage) of a branch of the pulmonary artery.

Key findings

• The study found a significant decrease in the pulmonary capillary and wedge pressures of horses that received frusemide, with the pressures averaging at 36 mmHg and 28 mmHg respectively.
• By comparison, the control group that received saline had higher pressure values, with the average pulmonary capillary pressure being 41 mmHg and wedge pressure being 35 mmHg.
• There was no notable difference in pulmonary arterial pressure, breathing rate, heart rate, or arterial blood gas tensions between horses that received frusemide and those that received saline (control group), regardless of the intensity of their exercise.

Conclusions

• The researchers concluded that administering frusemide reduces pulmonary capillary and wedge pressures in horses during strenuous physical activity.
• This indicates that frusemide can potentially reduce the accumulation of water in the lungs during exercise, which is consistent with a decrease in fluid passing through the capillaries (decreased “transcapillary filtration”).
• Consequently, this might account for the suggested protective effect of frusemide against exercise-induced pulmonary haemorrhage in horses.