Effect of furosemide on pulmonary blood flow distribution in resting and exercising horses.

This research investigates how the drug furosemide influences the distribution of blood flow in the lungs of thoroughbred horses during both rest and exercise. The study found that although the drug redistributes blood flow, there is less flow to the back part of the lung during exercise after the drug is administered.

Study Methodology

• The research was conducted on five Thoroughbred horses.
• The spatial distribution of pulmonary blood flow (PBF), which is the blood flow within the lungs was tracked using 15-micron fluorescent-labeled microspheres.
• This tracking was performed at two times: when the horses were at rest and while they were exercising.
• Measurements were taken both before and 4 hours after the administration of furosemide (a drug commonly used to treat high blood pressure and edema).

Findings

• The drug caused a redistribution of blood flow from rest to exercise, although there was a reduction in blood flow towards the back part (dorsal portion) of the lungs during exercise after the furosemide was administered.
• Resting perfusion distribution was affected by furosemide, which increased the blood flow to the ventral (front) regions of the horse’s lungs. However, this increase was reduced during exercise.
• Furosemide did not affect gas exchange (the process of oxygen and carbon dioxide moving between the bloodstream and lungs) or cardiac output (the amount of blood pumped by the heart) during rest or exercise.
• The researchers noted a decrease in pulmonary arterial pressure (the pressure in the pulmonary blood vessels) following the administration of furosemide.
• The relationship between PBF and vertical height up the lung increased in steepness during exercise, irrespective of whether furosemide was administered.
• After furosemide was given, there was a decrease in the blood flow to the dorsal region of the lung while at rest.

Implications

• The results suggest that the variability of lung perfusion (blood supply to the lung) may be related to the anatomy of pulmonary vessels, causing a akin spatial pattern of blood flow distribution, whether at rest or exercising.
• This study provides veterinary and biological scientists with new insights into how the drug furosemide affects the pulmonary circulatory system in horses.