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  • Author or Editor: Normand G. Ducharme x
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Abstract

Objective—To determine clinical and radiographic features of subchondral cystic lesions (SCL) of the proximal extremity of the tibia in horses that could be used to classify these lesions as being related to osteochondrosis or osteoarthritis and to evaluate results of surgical debridement.

Design—Retrospective study.

Animals—12 horses with 14 SCL.

Procedure—Medical records and radiographs obtained before and after treatment were reviewed.

Results—In 6 young horses (8 lesions), SCL were considered to be related to osteochondrosis; all involved the lateral tibial condyle. The remaining 6 horses were mature and had radiographic evidence of osteoarthritis in addition to SCL. Arthroscopic debridement was performed in 4 horses in which lesions were considered to be a result of osteochondrosis and in 3 horses with osteoarthritis. Three horses in which SCL were considered to be a result of osteochondrosis performed athletically after debridement. Two horses with moderate osteoarthritis returned to work after arthroscopic debridement but at a lower level of athletic performance. One horse with SCL related to osteochondrosis responded to medical treatment and went on to race.

Conclusions and Clinical Relevance—Results suggest that arthroscopic debridement of SCL is feasible in horses in which lesions involve the cranial portion of the lateral or medial tibial condyle, and that treated horses may be able to perform athletically. (J Am Vet Med Assoc 2001;218:408–413)

Full access
in Journal of the American Veterinary Medical Association

SUMMARY

To determine whether abnormal airway pressures have a role in development of dorsal displacement of the soft palate (ddsp), measurements of tracheal and pharyngeal pressures were correlated with nasopharyngeal morphology in exercising horses. Exercising videoendoscopy and measurement of tracheal and pharyngeal pressures were used in 14 clinically normal horses and 19 horses with intermittent ddsp. The pressure signals were superimposed on the videoendoscope image, and both images were saved simultaneously on a videocassette for slow motion analysis to determine the instant displacement occurred in the respiratory cycle. Horses were submitted to an escalating 8-minute high-speed test with a maximal speed of 14 m/s. Compared with clinically normal horses, horses with intermittent ddsp did not have excessively negative inspiratory pressures during exercise. Eight horses displaced the soft palate during inspiration, 4 horses displaced it during expiration, and 7 displaced it by swallowing. Some horses displaced the soft palate at the beginning of the exercise trial, before reaching maximal speed, some horses displaced it at the peak speed, and some horses displaced it when slowing down. Epiglottic size in horses with ddsp was within normal limits, ruling out epiglottic hypoplasia as a cause of ddsp during exercise. Airway pressures were significantly (P < 0.002) altered after ddsp. Pharyngeal and tracheal inspiratory pressures were less negative, whereas pharyngeal expiratory pressure became less positive and tracheal expiratory pressure became more positive after displacement, suggesting a decrease in airflow and an increase in expiratory resistance in the upper airway.

Free access
in American Journal of Veterinary Research

Summary

To assess right colic artery blood flow and relevance of xanthine dehydrogenase/xanthine oxidase after experimentally induced strangulation obstruction and reperfusion of the colon, 5 ponies were subjected to 2.5 hours of complete ischemia of the left dorsal and ventral colons, allowed to recover from surgery, and monitored during a 48-hour reperfusion period. Five ponies were subjected to sham surgery and served as controls. All ponies had a Doppler ultrasound blood flow monitor implanted on the right colic artery near the pelvic flexure 10 to 14 days prior to the ischemic period. Colic artery blood flow was monitored prior to, during and for 4 hours after surgery. Blood samples from the right colic artery and vein distal to the obstruction site were collected during surgery (prior to ischemia, after 1 and 2 hours of ischemia, and after 10 and 60 minutes of reperfusion) for determination of arterial and venous blood gas tensions and electrolytes. Prior to surgery, blood selenium and plasma vitamin E (α-tocopherol) concentrations and blood glutathione peroxidase (gpx) activity were determined to assess the status of endogenous antioxidants. Combined xanthine dehydrogenase (xdh) plus xanthine oxidase (xo) activity, and XO activity alone (nanomoles per minute per gram of tissue) were determined, using a dual-spectrophoto-metric technique. Xanthine dehydrogenase and oxidase activities were determined prior to ischemia, after 1 and 2 hours of ischemia, and at 1 and 48 hours after reperfusion.

Median blood flow in the experimental and control groups (156 ml/min and 110 ml/min, respectively) was not statistically different before surgery, and was significantly (P < 0.02) lower in the experimental (4 ml/min) vs the control group (72.5 ml/min) during the ischemic period. Experimental ponies had significantly (P < 0.03) lower right colic artery blood flow during the 4 hours immediately after recovery from anesthesia. Significant difference was not observed in right colonic venous bicarbonate concentration between groups at any time. Median right colonic venous Pco2 pH, and standard base excess were different (P < 0.001) between groups during the ischemic period only. Median venous oxygen saturation and median venous Po2 , were significantly (P < 0.001) lower in the experimental ponies at the end of 2 hours of ischemia, but were significantly (P < 0.05) increased during the reperfusion phase. Median venous potassium concentration was significantly (P < 0.01) higher in experimental ponies during the ischemic and reperfusion phases.

Vitamin E and gpx values were within normal limits for all ponies. Median selenium concentration was < 15 μg/dl; however, there were no significant differences between control and experimental ponies. Only 3 of 10 ponies had measurable XDH/XO activity at the beginning of the experiment. Enzyme activity was detected in 1 additional pony during the ischemic period. However, in all 4 ponies in which xdh/xo activity was detected, enzyme activity was low (10 to 36 nmol/min/g). On the basis of macroscopic and histologic examination of the large colon, evidence of reperfusion injury was not found in 4 of the 5 experimental ponies. The only pony with gross evidence of reperfusion injury did not have detectable xo activity. Results of the study indicate that hypoperfusion of the colon during the postischemic period may be a factor in deterioration of the colon observed clinically in equids with surgical correction of large-colon volvulus. Additionally, if reperfusion injury develops in the large colon, it probably is not mediated through the xanthine oxidase enzyme system: the activity of this enzyme in the large colon, when present, is negligible.

Free access
in American Journal of Veterinary Research

SUMMARY

We examined the electromyographic activity of the costal portion of the diaphragm and the transverse abdominal and external oblique muscles in 6 chronically instrumented awake adult horses during eupneic breathing, during 2 levels of hypercapnia (fractional concentration of inspired CO2; FI CO2 = 0.4 and 0.6), and during 2 levels of hypocapnic hypoxia (FI CO2 = 0.15 and 0.12). Using the inert gas technique, we also measured the end-expiratory lung volumes of the 6 horses during eupnea, 6% CO2 challenge, and 12% O2 breathing. During eupneic breathing, phasic electrical activity of these 3 muscles was always present and was preceded by the onset of mechanical flow. At progressive levels of hypercapnia, the magnitude of inspiratory and expiratory electrical activity increased, and for the expiratory muscles, this recruitment coincided with significant (P < 0.05) increases in peak expiratory gastric pressure. However, during hypocapnic hypoxia, differential recruitment patterns of the respiratory muscles were found. The electrical activity of the diaphragm increased in magnitude and occurred sooner relative to the onset of mechanical flow. The magnitude and onset of abdominal expiratory activity failed to increase significantly during these episodes of hyperpnea and this pattern of activity coincided with decrements in peak expiratory gastric pressure. Despite alterations in muscle recruitment patterns during these hyperpneic episodes, end-expiratory lung volume remained unchanged. Thus, we conclude that adult horses respond similarly to awake dogs during peripheral and central chemoreceptor stimulation.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate whether administering a tart cherry juice blend (TCJB) prior to exercise would reduce skeletal and cardiac muscle damage by decreasing the inflammatory and oxidative stress response to exercise in horses.

Animals—6 horses.

Procedures—Horses were randomly allocated into 2 groups in a crossover study with a 2-week washout period and orally administered either TCJB or a placebo solution (1.42 L, twice daily) in a double-masked protocol for 2 weeks prior to a stepwise incremental exercise protocol. Horses were tested for serum activities of creatine kinase and aspartate aminotransferase (AST) and concentrations of cardiac troponin I (cTnI), thiobarbituric acid reactive substances (TBARS; an indicator of oxidative stress), and serum amyloid A (SAA; an indicator of inflammation). To ensure that treatment would not result in positive results of an equine drug-screening protocol, serum samples obtained from each horse prior to and after 2 weeks of administration of TCJB or the placebo solution were tested.

Results—All horses had negative results of drug screening at both sample times. The exercise protocol resulted in a significant increase in TBARS concentration, SAA concentration, and serum AST activity in all horses. Administration of TCJB or placebo solution was not associated with an effect on malondialdehyde or SAA concentrations. However, administration of TCJB was associated with less serum activity of AST, compared with administration of placebo solution.

Conclusions and Clinical Relevance—Administration of TCJB may diminish muscle damage induced by exercise.

Full access
in American Journal of Veterinary Research