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  • Author or Editor: David B. Tesarowski x
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Abstract

Objectives

To evaluate the degree of reproducibility in clinical variables, blood gas measurements, and lung function variables, and the changes in these variables caused by exposure to moldy hay in naturally sensitized and control horses.

Procedure

The magnitude of variation in arterial blood gas and pulmonary function measurements were evaluated in a model of naturally acquired heaves. Horses with heaves and similarly aged control horses were studied prior to moldy hay challenge and again after the horses with heaves manifested clinical signs of airway obstruction. This cycle of testing was repeated 3 times to determine the variation of the before and after challenge measurements. Variables evaluated for repeatability included: clinical score; arterial O2 and CO2 tensions; pulmonary function variables, such as breathing rate (f), tidal volumes, and flow rates; lung resistance (Rl); dynamic compliance; and work of breathing (Wb).

Results

Before challenge, significant differences observed between control horses and horses with heaves included clinical score, expiratory flow rate at near-end expiration, Rl, and Wb. After exposure to moldy hay, variables measured in control horses were largely unchanged. However, in the afflicted horses, significant changes were observed for clinical score, arterial O2 and CO2 tensions, breathing rate, peak tidal inspiratory and expiratory flow rates, dynamic compliance, Rl, and Wb, compared with prechallenge values and with control horses' postchallenge values. Analysis of the data revealed few statistically significant differences between repeats of challenges.

Conclusion

Horses afflicted with heaves manifest airway obstruction that can be measured in repeatable fashion. (Am J Vet Res 1996;57:1214-1219)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate a 5-hydroxytryptamine type-2 receptor antagonist, metrenperone (MET), in alleviating respiratory distress associated with experimentally induced Pasteurella haemolytica pneumonia in feedlot calves.

Design

Double-blind controlled clinical trial.

Animals

30 healthy 6- to 8-month-old Hereford-type calves (250 to 450 kg).

Procedure

Initial measurements were made of rectal temperature (RT), arterial blood gas (ABG) tensions, and pulmonary mechanics. Calves were then infected with P haemolytica in logarithmic phase of growth by intratracheal inoculation. 18 hours later, determination of RT and ABG tensions, and pulmonary function testing were repeated and calves were selected for inclusion in the study on the basis of having 2 of the following: respiratory rate > 50 breaths/mm, RT > 40 C, or Pao2 > 20 mm of Hg below the baseline value. MET (0.1 mg/kg of body weight, IM) or an equivalent vehicle dose was then administered. RT, ABG, and pulmonary mechanics measurements were repeated at 0.5, 1, 2, 3, 4, 6, 12, and 24 hours after treatment. Calves were then euthanatized, and gross necropsy scoring and histologic examination were performed on the lungs.

Results

Infection with P haemolytica caused significant increases in RT and respiratory rate, and reduction in Pao2 , Paco2 , and tidal volume 18 hours after inoculation. MET-treated calves had significantly reduced rectal temperature between 1 and 12 hours, compared with vehicle-treated calves. In addition, MET-treated calves had reduced respiratory rate with concomitantly increased tidal volume between 0.5 and 2 hours after treatment, compared with vehicle-treated calves. Necropsy revealed acute lobar bronchopneumonia in all 30 calves, but there was no difference in necropsy score between treatment groups.

Conclusions and Clinical Relevance

MET may have an antipyretic effect on calves with pneumonia caused by P haemolytica. Its influence on pulmonary mechanics was minimal however, and it did not induce lung lesions in the short term. (Am J Vet Res 1996;57:1034–1039)

Free access
in American Journal of Veterinary Research