Pulmonary artery and aortic pressure changes during high intensity treadmill exercise in the horse: effect of frusemide and phentolamine.

The research article investigates how frusemide and phentolamine, two commonly used drugs, influence the changes in the pulmonary artery and aortic pressures of horses during high-intensity exercise. It suggests that while frusemide can significantly reduce the mean aortic pressure, it fails to prevent horses from bleeding during exercise. On the other hand, phentolamine appears to not have a substantial impact on the aforementioned parameters, thereby not supporting the hypothesis that a decrease in both pressures could prevent exercise-induced pulmonary haemorrhage.

Methodology

• The study involved administering intravenous frusemide (1.0 mg/kg body weight) or phentolamine (0.33 mg/kg body weight) to seven horses one hour before initiating the exercise protocol.
• The impact of the drugs on the changes in pulmonary artery and aortic pressures during intense exercise was then closely observed and analyzed.
• Such rigorous exercise regime was simulated by a near-maximum treadmill exercise at a speed of 10 m/sec and a 3-degrees incline.

Results

• The exercise routine resulted in significant increases in various parameters including heart rate, mean pulmonary artery pressure, mean aortic pressure, and packed cell volume.
• Administering frusemide didn’t lead to any appreciable change in the heart rate, pulmonary artery pressure, or packed cell volume during exercise.
• However, frusemide did have a significant effect on the mean aortic pressure, reducing it by 10 to 15 mmHg during the exercise regime.
• Phentolamine administration led to an increase in heart rate only during the initial stage of exercise and had no substantial impact during the more intense part of the workout. The drug did not have any statistically significant effect on aortic pressure, pulmonary artery pressure, or packed cell volume.
• A notable reduction between 180 to 230 seconds of exercise was observed in standardized pulmonary artery pressure and aortic pressure when contrasted with the heart rate.

Conclusion

• The data indicated that the use of frusemide did not prevent the horses from bleeding during the exercise session.
• The application of phentolamine did not significantly decrease the pulmonary artery pressure and aortic pressure, thereby failing to validate the hypothesis that lowering these pressures could help prevent exercise-induced pulmonary haemorrhage (EIPH).