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  • Author or Editor: Lisa M. Mitchell x
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Abstract

Objective—To determine the effects of hypoglossal nerve block and electrical stimulation of the thyrohyoideus muscles on position of the larynx and hyoid apparatus in resting horses.

Animals—16 healthy horses that underwent hypoglossal nerve block and 5 healthy horses that underwent electrical stimulation of the thyrohyoideus muscles.

Procedures—Horses underwent bilateral hypoglossal nerve block or electrical stimulation of the thyrohyoideus muscles. Positions of the basihyoid bone, ossified part of the thyroid cartilage, and articulations of the thyrohyoid bones and thyroid cartilage were determined in radiographic images obtained before and after performance of hypoglossal nerve blocks or during thyrohyoideus muscle stimulation. Radiographic images were obtained with the heads of horses in neutral (thyrohyoideus muscle stimulation) or neutral and extended (hypoglossal nerve block) positions. Radiographic images of horses obtained after performance of hypoglossal nerve blocks were also evaluated to detect dorsal displacement of the soft palate.

Results—Hypoglossal nerve blocks did not induce significant changes in the positions of evaluated anatomic sites in radiographic images obtained in neutral or extended head positions. Hypoglossal nerve block did not induce dorsal displacement of the soft palate in horses at rest. Bilateral thyrohyoideus muscle stimulation induced significant dorsal movement (mean ± SD change in position, 18.7 ± 6.8 mm) of the ossified part of the thyroid cartilage; rostral movement of evaluated anatomic structures was small and not significant after thyrohyoideus muscle stimulation.

Conclusions and Clinical Relevance—Bilateral electrical stimulation of the thyrohyoideus muscles in horses in this study induced dorsal laryngeal movement.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine outcome in dogs and cats that underwent extensive (ie, > 50%) resection of the small intestine and identify factors associated with outcome.

Design—Retrospective case series.

Animals—13 dogs and 7 cats.

Procedure—Medical records were reviewed, and follow-up information was obtained.

Results—In all 7 cats and in 8 of the 13 dogs, extensive intestinal resection was performed because of a foreign body. Mean ± SD estimated percentage of intestine that was removed was 68 ± 14% (range, 50% to 90%). Two dogs were euthanized 3 days after surgery because of dehiscence of the surgical site and development of septic peritonitis; 1 dog died of acute respiratory distress syndrome 5 days after surgery. The remaining 10 dogs and 7 cats were discharged from the hospital, and follow-up information was available for 15 of the 17. Median survival time was 828 days, and 12 of the 15 animals for which long-term follow-up information was available had good outcomes. However, none of the factors examined, including percentage of intestine resected, were significantly associated with outcome.

Conclusions and Clinical Relevance—Most dogs and cats that underwent extensive resection of the small intestine had a good outcome. The amount of intestine resected was not associated with outcome. These data may be useful in providing prognostic information in cases of extensive small intestinal resection.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the phase and quantitate the electromyographic (EMG) activity of the genioglossus, geniohyoideus, hyoepiglotticus, omohyoideus, sternohyoideus, sternothyroideus, and thyrohyoideus muscles of clinically normal horses during strenuous exercise.

Animals—7 clinically normal adult horses (2 Thoroughbreds and 5 Standardbreds).

Procedures—Bipolar electrodes were surgically implanted in the aforementioned muscles, and horses were subjected to an incremental exercise test on a high-speed treadmill. The EMG, heart rate, respiratory rate, and static pharyngeal airway pressures were measured during exercise. The EMG was measured as mean electrical activity (MEA). The MEA values for maximal exercise intensity (13 or 14 m/s) were expressed as a percentage of the MEA measured at an exercise intensity of 6 m/s.

Results—MEA was detected during expiration in the genioglossus, geniohyoideus, sternohyoideus, and thyrohyoideus muscles and during inspiration in the hyoepiglotticus and sternothyroideus muscles. Intensity of the MEA increased significantly with exercise intensity in the genioglossus, geniohyoideus, and hyoepiglotticus muscles. Intensity of the MEA increased significantly in relation to expiratory pharyngeal pressure in the geniohyoideus and hyoepiglotticus muscles.

Conclusions and Clinical Relevance—Once exercise intensity reached 6 m/s, no quantifiable additional increase in muscular activity was detected in the omohyoideus, sternohyoideus, sternothyroideus, and thyrohyoideus muscles. However, muscles that may affect the diameter of the oropharynx (genioglossus and geniohyoideus muscles) or rima glottis (hyoepiglotticus muscle) had activity correlated with the intensity of exercise or expiratory pharyngeal pressures. Activity of the muscles affecting the geometry of the oropharynx may be important in the pathophysiologic processes associated with nasopharyngeal patency.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To investigate whether upper airway sounds of horses exercising with laryngeal hemiplegia and alar fold paralysis have distinct sound characteristics, compared with unaffected horses.

Animals—6 mature horses.

Procedure—Upper airway sounds were recorded in horses exercising on a high-speed treadmill at maximum heart rate (HRMAX) under 3 treatment conditions (ie, normal upper airway function [control condition], and after induction of left laryngeal hemiplegia or bilateral alar fold paralysis) in a randomized crossover design. Fundamental frequency, spectrograms using Gabor transform, and intensity characteristics of acquired sounds (peak sound level [soundpeak] and highest frequency of at least –25 dB sound intensity [F25max]) were evaluated.

Results—Evaluation of the fundamental frequency of the time domain signal was not useful. Sensitivity and specificity (83 and 75%, respectively) of spectrograms were greatest at maximal exercise, but the exact abnormal condition was identified in evaluation of only 12 of 18 spectrograms. Increased accuracy was obtained using soundpeak and F25max as discriminating variables. The use of soundpeak discriminated between control and laryngeal hemiplegia conditions and F25max between laryngeal hemiplegia and alar fold paralysis conditions. This increased the specificity of sound analysis to 92% (sensitivity 83%) and accurately classified the abnormal state in 92% of affected horses.

Conclusions and Clinical Relevance—Sound analysis might be a useful adjunct to the diagnosis and evaluation of treatment of horses with upper airway obstruction, but would appear to require close attention to exercise intensity. Multiple measurements of recorded sounds might be needed to obtain sufficient accuracy for clinical use. (Am J Vet Res 2002;63:1707–1713)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To identify factors associated with outcome in cats with extrahepatic biliary tract obstruction (EHBTO) that undergo biliary diversion surgery.

Design—Retrospective case series.

Animals—22 cats.

Procedures—Medical records of cats with surgically confirmed EHBTO that underwent cholecystoenterostomy were reviewed.

Results—Clinical signs and physical examination findings included vomiting, anorexia, icterus, lethargy, weakness, and weight loss. Common clinicopathologic abnormalities included high serum hepatic enzyme activities and serum bilirubin concentration. Abdominal ultrasonography was performed in 21 cats, and all 21 had findings consistent with EHBTO. Eleven of 15 cats in which blood pressure was monitored had intraoperative hypotension. Eighteen cats had anemia following surgery, and 14 cats had persistent hypotension. Extrahepatic biliary tract obstruction was a result of neoplasia in 9 cats and chronic inflammatory disease in 13. Fourteen cats survived long enough to be discharged from the hospital, but only 6 survived > 6 months after surgery, all of which had chronic inflammatory disease. Median survival time for cats with neoplasia (14 days) was significantly shorter than that for cats with inflammatory disease (255 days). No other variable was associated with outcome.

Conclusions and Clinical Relevance—Results suggest that cats with EHBTO secondary to neoplasia have a poorer prognosis than cats with EHBTO secondary to chronic inflammatory disease. However, the overall prognosis for cats with EHBTO undergoing cholecystoenterostomy must be considered guarded to poor, and the incidence of perioperative complications is high.

Restricted access
in Journal of the American Veterinary Medical Association

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

Abstract

Objective—To compare cardiac troponin I (cTnI) concentrations determined by use of a point-of-care analyzer with values determined by use of a bench-top immunoassay in plasma samples obtained from clinically normal horses with and without experimentally induced cardiac disease, and to establish a reference range for plasma equine cTnI concentration determined by use of the point-of-care analyzer.

Animals—83 clinically normal horses, 6 of which were administered monensin to induce cardiac disease.

Procedures—A blood sample was collected from each of the 83 clinically normal horses to provide plasma for analysis by use of the point-of-care analyzer; some of the same samples were also analyzed by use of the immunoassay. All 83 samples were used to establish an analyzer-specific reference range for plasma cTnI concentration in clinically normal horses. In 6 horses, blood samples were also collected at various time points after administration of a single dose of monensin (1.0 to 1.5 mg/kg) via nasogastric intubation; plasma cTnI concentration in those samples was assessed by use of both methods.

Results—The analyzer-specific reference range for plasma cTnI concentration in clinically normal horses was 0.0 to 0.06 ng/mL. Following monensin treatment in 5 horses, increases in plasma cTnI concentration determined by use of the 2 methods were highly correlated (Pearson correlation, 0.83). Peak analyzer-determined plasma cTnI concentrations in monensin-treated horses ranged from 0.08 to 3.68 ng/mL.

Conclusions and Clinical Relevance—In horses with and without experimentally induced cardiac disease, the point-of-care analyzer and bench-top immunoassay provided similar values of plasma cTnI concentration.

Full access
in American Journal of Veterinary Research