Pulmonary vascular pressures of strenuously exercising Thoroughbreds after administration of phenylbutazone

Murli Manohar From the Departments of Veterinary Biosciences (Manohar, Griffin, Sullivan) and Veterinary Clinical Medicine (Goetz), College of Veterinary Medicine, University of Illinois, Urbana, IL 61801.

Search for other papers by Murli Manohar in
Current site
Google Scholar
PubMed
Close
 BVSc, PhD
,
Thomas E. Goetz From the Departments of Veterinary Biosciences (Manohar, Griffin, Sullivan) and Veterinary Clinical Medicine (Goetz), College of Veterinary Medicine, University of Illinois, Urbana, IL 61801.

Search for other papers by Thomas E. Goetz in
Current site
Google Scholar
PubMed
Close
 DVM
,
Richard Griffin From the Departments of Veterinary Biosciences (Manohar, Griffin, Sullivan) and Veterinary Clinical Medicine (Goetz), College of Veterinary Medicine, University of Illinois, Urbana, IL 61801.

Search for other papers by Richard Griffin in
Current site
Google Scholar
PubMed
Close
 MS
, and
Eileen Sullivan From the Departments of Veterinary Biosciences (Manohar, Griffin, Sullivan) and Veterinary Clinical Medicine (Goetz), College of Veterinary Medicine, University of Illinois, Urbana, IL 61801.

Search for other papers by Eileen Sullivan in
Current site
Google Scholar
PubMed
Close
 BS

Click on author name to view affiliation information

Abstract

Objective

To determine the effects of phenylbutazone administration on heart rate and right atrial and pulmonary vascular pressures in Thoroughbreds during rest and during exercise performed at maximal heart rate.

Animals

7 healthy, exercise-conditioned Thoroughbreds.

Procedure

Horses were studied on 3 occasions: without medication (control), after IV administration of phen-ylbutazone (4.4 mg/kg of body weight) at 12-hour intervals for 2 days and a final dose given 1 hour before exercise, and after IV administration of phenylbutazone for 2 days in the same manner, but with the final dose given 24 hours before exercise. Horses were studied at rest and during exercise performed at maximal heart rate on a treadmill. Right atrial and pulmonary vascular pressures were measured with catheter-tip manometers referenced at the point of the shoulder.

Results

We did not detect significant differences in heart rate or right atrial and pulmonary vascular pressures among values recorded when horses were not given medication and values recorded when phenylbutazone was administered by either regimen. Exercise-induced pulmonary hemorrhage occurred in 6 of the 7 horses re-gardless of whether phenylbutazone was administered or the dosage regimen used.

Conclusions

In these Thoroughbreds, phenylbutazone treatment did not modify heart rate or right atrial and pulmonary vascular pressures at rest or during exercise capable of eliciting exercise-induced pulmonary hemorrhage. Thus, because phenylbutazone is a potent inhibitor of cyclooxygenase, prostaglandins probably do not play a role in mediating exercise-induced pulmonary hypertension in horses.

Clinical Relevance

Phenylbutazone administration did not modify the pulmonary capillary hypertension in the strenuously exercising Thoroughbreds, and therefore, is unlikely to alter the prevalence or severity of exercise-induced pulmonary hemorrhage in Thoroughbred race-horses. (Am J Vet Res 1996;57:1354-1358)

Abstract

Objective

To determine the effects of phenylbutazone administration on heart rate and right atrial and pulmonary vascular pressures in Thoroughbreds during rest and during exercise performed at maximal heart rate.

Animals

7 healthy, exercise-conditioned Thoroughbreds.

Procedure

Horses were studied on 3 occasions: without medication (control), after IV administration of phen-ylbutazone (4.4 mg/kg of body weight) at 12-hour intervals for 2 days and a final dose given 1 hour before exercise, and after IV administration of phenylbutazone for 2 days in the same manner, but with the final dose given 24 hours before exercise. Horses were studied at rest and during exercise performed at maximal heart rate on a treadmill. Right atrial and pulmonary vascular pressures were measured with catheter-tip manometers referenced at the point of the shoulder.

Results

We did not detect significant differences in heart rate or right atrial and pulmonary vascular pressures among values recorded when horses were not given medication and values recorded when phenylbutazone was administered by either regimen. Exercise-induced pulmonary hemorrhage occurred in 6 of the 7 horses re-gardless of whether phenylbutazone was administered or the dosage regimen used.

Conclusions

In these Thoroughbreds, phenylbutazone treatment did not modify heart rate or right atrial and pulmonary vascular pressures at rest or during exercise capable of eliciting exercise-induced pulmonary hemorrhage. Thus, because phenylbutazone is a potent inhibitor of cyclooxygenase, prostaglandins probably do not play a role in mediating exercise-induced pulmonary hypertension in horses.

Clinical Relevance

Phenylbutazone administration did not modify the pulmonary capillary hypertension in the strenuously exercising Thoroughbreds, and therefore, is unlikely to alter the prevalence or severity of exercise-induced pulmonary hemorrhage in Thoroughbred race-horses. (Am J Vet Res 1996;57:1354-1358)

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 38 38 15
PDF Downloads 16 16 5
Advertisement