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- Author or Editor: E. M. Raub x
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Abstract
Objective—To evaluate clinical response, pulmonary function, and adrenal gland response to incremental doses of beclomethasone dipropionate in horses with recurrent airway obstruction.
Design—Crossover trial.
Animals—8 horses with recurrent airway obstruction.
Procedure—Horses randomly assigned to 4 groups were treated twice daily via aerosol administration of placebo or 500, 1,000, or 1,500 µg of beclomethasone dipropionate in a crossover design with a 10-day minimum washout period. Subjective assessment of airway obstruction, serum cortisol concentration, and maximum change in pleural pressure during tidal breathing (ΔPplmax) were determined daily prior to morning drug administration, and ΔPplmax was reevaluated 15 minutes after morning drug administration. Pulmonary resistance and dynamic compliance were determined at baseline and approximately 12 hours after the final treatment.
Results—An immediate treatment effect was not identified. Within 24 hours, ΔPplmax and airway obstruction were lower in horses receiving beclomethasone. Onset and magnitude of response was similar among the 3 beclomethasone dose regimens. Pulmonary resistance was improved only after administration of all 3 doses of beclomethasone, whereas dynamic compliance was improved after administration of 1,000 µg and 1,500 µg of beclomethasone. Reduction in serum cortisol concentration occurred with all 3 beclomethasone dose regimens; however, the magnitude of adrenal gland suppression was greater in horses receiving 1,000 or 1,500 µg of beclomethasone.
Conclusions and Clinical Relevance—Low-dose (500 µg) beclomethasone administration caused similar improvement in pulmonary function, compared with high-dose beclomethasone (1,000 and 1,500 µg), with the exception of dynamic compliance, and caused less suppression of endogenous cortisol production. (J Am Vet Med Assoc 2000;217:359–364)
SUMMARY
Furosemide, which commonly is used as a prophylactic treatment for exercise-induced pulmonary hemorrhage in horses, may mediate hemodynamic changes during exercise by altering prostaglandin metabolism. To determine if furosemide's hemodynamic effects during exercise in horses could be reversed, cyclooxygenase inhibitors were administered with furosemide. Four treatments were administered 4 hours prior to treadmill exercise at 9 and 13 m/s. They included a control treatment (10 ml of 0.9% NaCl solution, iv), furosemide (1 mg/kg of body weight, iv) administered alone, and furosemide in combination with phenylbutazone (4 mg/kg, iv, q 12 h for 2 days) or with flunixin meglumine (1.1 mg/kg, iv, on the day of experiment). Five horses were randomly assigned to complete all treatments. Physiologic variables at rest prior to exercise were not influenced by treatments. Furosemide, administered alone, reduced mean right atrial pressure and mean pulmonary artery pressure during exercise. The combinations of furosemide and flunixin meglumine or furosemide and phenylbutazone, at both levels of exercise intensity, returned mean right atrial pressure and mean pulmonary artery pressure to the value of the control treatment. During rest and exercise, plasma lactate concentration, pcv, heart rate, mean carotid artery pressure, oxygen consumption, carbon dioxide elimination, and cardiac output were not altered by any of the treatments. At 5 minutes after exercise, the administration of furosemide, alone or with phenylbutazone, reduced mean right atrial pressure. Other measured variables were not significantly influenced by treatments during recovery from exercise. These results suggested that cyclooxygenase inhibition partially reverses the decrease in mean right atrial pressure or pulmonary artery pressure induced by furosemide during exercise. Furosemide may mediate some of its physiologic activities in exercising horses through the cyclooxygenase pathway.
Summary
Four hours prior to exercise on a high-speed treadmill, 4 dosages of furosemide (0.25, 0.50, 1.0, and 2.0 mg/kg of body weight) and a control treatment (10 ml of 0.9% NaCl) were administered iv to 6 horses. Carotid arterial pressure (cap), pulmonary arterial pressure (pap), and heart rate were not different in resting horses before and 4 hours after furosemide administration. Furosemide at dosage of 2 mg/kg reduced resting right atrial pressure (rap) 4 hours after furosemide injection. During exercise, increases in treadmill speed were associated with increases in rap, cap, pap, and heart rate. Furosemide (0.25 to 2 mg/kg), administered 4 hours before exercise, reduced rap and pap during exercise in dose-dependent manner, but did not influence heart rate. Mean cap was reduced by the 2-mg/kg furosemide dosage during exercise at 9 and 11 m/s, but not at 13 m/s. During recovery, only rap was decreased by furosemide administration. Plasma lactate concentration was not significantly influenced by furosemide administration. Furosemide did not influence pcv or hemoglobin concentration at rest prior to exercise, but did increase both variables in dose-dependent manner during exercise and recovery. However, the magnitude of the changes in pcv and hemoglobin concentration were small in comparison with changes in rap and pap, and indicate that furosemide has other properties in addition to its diuretic activities. Furosemide may mediate some of its cardiopulmonary effects by vasodilatory activities that directly lower pulmonary arterial pressure, but also increase venous capacitance, thereby reducing venous return to the atria and cardiac filling.
Abstract
Objective
To determine changes in clinical signs of disease and response to pulmonary function testing in horses with recurrent airway obstruction (heaves) after aerosol and parenteral administration of beclomethasone dipropionate and dexamethasone, respectively.
Animals
6 horses with inducible and reversible heaves.
Procedure
Episodes of heaves were induced by exposure (challenge) to moldy hay and straw for 7 days. Horses were assigned to treatment groups (aerosolized beclomethasone dipropionate, parenterally administered dexamethasone, aerosolized propellant [control]), and respiratory frequency and subjective assessment of respiratory effort were determined twice daily. Maximal change in pleural pressure (ΔPplmax), pulmonary resistance (RL), and dynamic compliance (Cdyn) was determined on days 0, 7, 10, 14, and 21.
Results
The RL and ΔPplmax were increased, and Cdyn was decreased in all horses in response to natural challenge. Beclomethasone reduced RL on day 10, reduced ΔPplmax on days 14 and 21 and increased Cdyn on day 14. Dexamethasone reduced RL and ΔPplmax on days 10, 14, and 21 and increased Cdyn on days 10 and 14. Respiratory effort (subjective assessment) improved after 2 and 3 days of beclomethasone and dexamethasone administration but rebounded to pretreatment values 1 and 3 days after discontinuation of drugs.
Conclusions
Pulmonary function testing responses and clinical signs of airway obstruction were improved by administration of beclomethasone. The magnitude of response to aerosolized beclomethasone generally was less marked than the response to parenterally administered dexamethasone. Higher or more frequent dosing of aerosolized beclomethasone may be necessary to achieve the anti-inflammatory response to parenterally administered dexamethasone. (Am J Vet Res 1998;59:1039–1043)
