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  • Author or Editor: Hélène Michaux x
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Abstract

Objective—To describe the optimal thoracoscopic approach to the bovine pleural cavity and evaluate the short-term effects of thoracoscopy on cardiovascular and pulmonary function of healthy cattle.

Sample—6 healthy adult Holstein cows (12 hemithoraxes).

Procedures—For each cow, thoracoscopy was performed in both the left and right hemithoraxes with a 24-hour interval between procedures. Cows were sedated and restrained in a standing position for each thoracoscopic examination. Examination of each hemithorax lasted for 30 minutes. Arterial blood gas variables, heart rate, and respiratory rate were assessed at predetermined times before, during, and after the procedures to monitor cardiovascular and pulmonary function. Thoracic ultrasonography was performed immediately and at 24 hours and 1 week after each thorascopic examination to evaluate the extent of residual pneumothorax.

Results—Insertion of the laparoscope into the pleural cavity at the ninth intercostal space 15 cm ventral to the transverse processes of the thoracic vertebrae provided optimal visibility of structures in both the left and right hemithoraxes. Most structures of the pleural cavity were equally visible from both sides except the esophagus and the dorsal branch of the vagus nerve, which were best observed in the left hemithorax, and the pericardium, which was best observed in the right hemithorax. Mild increases in heart and respiratory rates and moderate decreases in arterial oxygen saturation and Pao2 were detected during the procedures.

Conclusions and Clinical Relevance—Standing thoracoscopy was well tolerated in healthy adult dairy cattle and needs to be evaluated in cattle with pulmonary disease.

Full access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate left and right ventricular filling and ejection performances by use of Doppler echocardiography in healthy, conscious dogs submitted to dobutamine stress testing.

Animals

10 unsedated, healthy adult Beagles.

Procedure

Doppler echocardiography was performed during cardiac stress testing on each dog twice at 24-hour intervals. Dobutamine was infused in 10 µg/kg of body weight/min incremental dosages, from 12.5 to 42.5 µg/kg/min. Duration of each step was 15 minutes. Doppler measurements were recorded at baseline and at each stage of dobutamine infusion, whereas aortic diameter was measured at baseline and at peak dosage by use of two-dimensional echocardiography.

Results

Dobutamine infusion induced a significant increase in velocity time integrals and in peak flow velocities at the aortic, pulmonic, mitral, and tricuspid valves. Acceleration time-to-deceleration time ratio at the aortic wave also was increased significantly. On the other hand, ejection time, acceleration time, and deceleration time at the aortic and pulmonic valves and peak flow velocity of the E wave-to-peak flow velocity of the A wave ratio at the mitral and tricuspid valves decreased significantly during the test. The acceleration time-to-deceleration time ratio at the pulmonic wave was unchanged. A significant, progressive increase in cardiac index also was observed during dobutamine infusion, with a maximal increase of 104% from baseline. This was mediated initially by an increase in stroke index and, at higher dosages, by an increase in heart rate.

Conclusions and Clinical Relevance

Doppler echocardiography performed during dobutamine stress testing may be a reliable method of assessing myocardial function in dogs with cardiovascular disease. (Am J Vet Res 1999;60:865–871)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate response of various cardiovascular variables after administration of incremental doses of dobutamine in healthy conscious dogs, using standardized dobutamine stress echocardiography (DSE).

Animals

8 healthy dogs.

Procedure

A DSE was performed twice on each dog within 24 hours. Dobutamine was infused at a rate of 12.5 to 42.5 μg/kg/min, using incremental increases of 10 μg/kg/min. Doppler sphygmomanometry, electrocardiography, and echocardiography were performed. Left ventricular size, global ventricular performance, and left ventricular systolic myocardial function were measured by means of echocardiography.

Results

At the highest dosage, dobutamine induced an increase of 20 ± 3% and 109 ± 12% in systolic blood pressure and cardiac index, respectively. The latter was associated with a significant increase in heart rate and stroke index. Fractional shortening of the left ventricle, fractional thickening of the left ventricular free wall and interventricular septum, ejection fraction, and mean velocity of fiber shortening had a progressive and significant increase during dobutamine infusion. Preejection period and left ventricular ejection time had a progressive and significative decrease during the stress test.

Conclusions

The technique used was feasable, safe, and repeatable in healthy conscious dogs. Control values were determined.

Clinical Relevance

Data for these healthy dogs might be useful for comparison with results obtained from dogs with known or suspected cardiovascular disease. (Am J Vet Res 1998;59:1160-1165)

Free access
in American Journal of Veterinary Research

SUMMARY

The purpose of this study was to investigate the mechanism by which 5-hydroxytryptamine (5-ht) modifies respiratory function, specifically, hyperventilation, diffuse bronchoconstriction, and pulmonary arterial hypertension in cattle. We determined whether the IV response to 5-ht in calves was attributable to stimulation of 5-ht2 receptors.

Six healthy unsedated young bull calves of the Friesian (n = 4) and of the Belgian White and Blue (n = 2) breeds were used. A specific 5-ht2 antagonist (metrenperone, 0.05 mg/kg of body weight) was administered IM 30 minutes before the cattle were given a 5-minute IV 5-ht infusion. Pulmonary function values were registered before, during, and after the 5-ht challenge infusion. Minute volume increased significantly, because of an increase in respiratory rate. Conversely, lung dynamic compliance, total pulmonary resistance, and pulmonary arterial pressure were not changed.

We concluded that in cattle, 5-ht-induced ventilatory response is not mediated through activation of 5-ht2 receptors. However, the 5-ht2 receptors are involved in 5-ht-induced broncho- and pulmonary vasoconstriction.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether dobutamine stress tests (DST) can be used to detect cardiac dysfunction in dogs with early left ventricular dysfunction (ELVD) induced by rapid right ventricular pacing (RRVP).

Animals—7 adult male Beagles.

Procedure—A pacemaker was surgically implanted in each dog at the level of the right ventricular apex. Electrocardiography, Doppler sphygmomanometry, and Doppler echocardiography were performed before and during a DST prior to activation of the pacemaker and every 3 to 4 days during the period of RRVP. Dobutamine stress tests were performed by infusing dobutamine at incremental dosages ranging from 12.5 to 42.5 µg/kg of body weight/min.

Results—Clinical signs of congestive heart failure were not observed during the pacing period. However, all dogs developed ELVD associated with significant changes in values for most Doppler echocardiographic variables obtained prior to DST. Adverse cardiac effects were not detected during DST. Most Doppler echocardiographic indices of cardiac function were significantly altered in response to dobutamine infusion during the pacing period, compared with prepacing values. However, a dobutamine-induced 2-fold increase in cardiac output was maintained.

Conclusions and Clinical Relevance—Dobutamine stress tests can be safely performed in dogs with experimentally induced ELVD. Dobutamine stress tests may be a sensitive, noninvasive diagnostic method, complementary to standard clinical examinations, for detection of early cardiac dysfunction in dogs asymptomatic for dilated cardiomyopathy. (Am J Vet Res 2001;62:448–455)

Full access
in American Journal of Veterinary Research