DOPPLER ECHOCARDIOGRAPHY IN THE NORMAL DOG: PART II

Doppler echocardiography was used to determine blood flow velocities in the normal canine heart. The areas examined were the mitral valve, left atrium, tricuspid valve, right atrium, aortic valve, left ventricular outflow tract, pulmonic valve and right ventricular outflow tract. This study then statistically evaluated the influence of breed, age, sex, heart rate, mass and various interactions of these factors on the cardiac flow values determined. Mass and heart rate had the most significant effect on the various determinations with decreasing mass and increasing heart rates generally resulting in increasing peak and mean velocities. The pulmonary artery was statistically judged as being the flow area most susceptible to such influences. Comparisons were made between pulsed and continuous wave Doppler for peak velocities over the four valve areas with only aortic flow, as measured from the left caudal view, showing a significant difference between the two techniques. Mitral flow as compared to tricuspid flow showed a statistically significant difference between peak late diastolic velocities only. The ratio of early mitral diastolic flow to late mitral diastolic flow was always greater than one. Pulmonary flow showed a number of statistically significant differences when compared to aortic flow.     

Half-Body Radiotherapy in the Treatment of Canine Lymphoma

In a Phase I-II study, half-body radiotherapy was used to treat 14 dogs with multicentric lymphoma. Using this technique, a radiation dose of 7 Gray (Gy) was delivered to one half of the body in a single exposure. The other half of the body was treated approximately 28 days later. Of 14 treated dogs, 11 (79%) had a measurable decrease in tumor size. Five dogs achieved a complete or partial remission with a mean duration of 102 and 54 days, respectively. In predicting response to therapy, poor prognostic factors included large tumor burdens, advanced disease stage, and chemotherapy-resistant tumors. Side effects of treatment were divided chronologically into acute (radiation sickness, tumor lysis), subacute (bone marrow suppression), and chronic (radiation pneumonitis, lymphoma-cell leukemia) syndromes. Complications were more severe in tumor-bearing dogs when compared with healthy control animals. Dogs with small tumor burdens and minimal internal disease had fewer complications compared with those with more advanced disease.     

Alterations in Carbohydrate Metabolism in Canine Lymphoma

Following an overnight fast, blood samples were obtained from 14 dogs with previously untreated lymphoma before and 5, 15, 30, 45, 60, and 90 minutes following an intravenous challenge with 500 mg/kg dextrose. Samples were assayed for glucose, lactate, and insulin concentrations and compared statistically with ten control dogs of similar weight and age undergoing an identical dextrose challenge. Dogs with lymphoma had similar glucose tolerance curves when compared with controls. Lactate concentrations were significantly higher (P less than 0.001) at baseline and all time periods of the glucose tolerance test in dogs with lymphoma when compared with controls. Rise in lactate concentrations over baseline levels in the first 30 minutes of the glucose tolerance test were significantly higher in dogs with lymphoma (P = 0.011). Insulin concentrations were significantly higher (P less than 0.001) at baseline and at the 5-, 45-, 60-, and 90-minute time periods of the glucose tolerance test in dogs with lymphoma. Rise in insulin concentrations over baseline in the first 5 minutes of the glucose tolerance test were also significantly greater in dogs with lymphoma (P = 0.021). These results indicate carbohydrate metabolism is altered in dogs with lymphoma. Many of these alterations parallel those observed in human patients suffering from cancer cachexia making canine lymphoma a potential model for further study of the pathogenesis and therapy of cancer cachexia.     

Hepatic Organelle Pathology in Dogs with Congenital Portosystemic Shunts

Diversion of portal blood in congenital portosystemic shunts (CPSS) results in liver atrophy and passage of toxins into the systemic circulation causing hepatic encephalopathy. In some dogs, there is indirect evidence for hepatic insufficiency, but histologic findings are equivocal. This study determined whether hepatocyte integrity in PSS is comprised at a subcellular level using analytical subcellular fractionation of liver biopsies. Six dogs with CPSS had hypoproteinemia (6/6), increased serum alkaline phosphatase (6/6) and alanine aminotransferase (4/6) activity, hypocholesterolemia (6/6), and decreased blood urea (2/6). Liver biopsy specimens had increased activities (mU/mg protein) of alkaline phosphatase (17.9 +/- 10.1; controls 5.1 +/- 5.3: P less than 0.01), but not of other plasma membrane enzymes. There were increased activities of endoplasmic reticular (neutral alpha-glucosidase: 1.67 +/- 0.7; controls 0.86 +/- 0.2: P less than 0.01) and lysosomal enzymes (N-acetyl-beta-glucosaminidase: 12.6 +/- 2.3; controls 6.24 +/- 2.7: P less than 0.01; alpha-mannosidase: 0.85 +/- 0.5; controls 0.39 +/- 0.3: P less than 0.05). Subcellular fractionation on reorientating sucrose density gradients showed a high-density peak of alkaline phosphatase suggestive of a specific increase in the biliary canalicular component of enzyme activity. Neutral alpha-glucosidase was shifted to denser fractions, indicative of an increase in the proportion of rough-to-smooth endoplasmic reticulum and consistent with enhanced synthesis of membranous enzymes. There was also evidence for increased fragility of intracellular organelles, particularly lysosomes. In contrast, histology showed either no abnormalities or minor degenerative changes compatible with hepatic underperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Autologous Platelet Concentrates as a Treatment of Horses with Osteoarthritis: A Preliminary Pilot Clinical Study

The clinical effect of the intra-articular injection of an autologous platelet concentrate (PC) in four horses with osteoarthritis was evaluated. The degree of lameness and joint effusion and clinical follow-up were recorded. Three injections of PC were performed at 2-week intervals. Horses were evaluated before each injection and two months after the last treatment. Clinical follow-up was conducted for 1 year. Count of platelets, leukocytes, and determination of transforming growth factor beta-1 (TGF-β₁) levels per milliliter PC were performed, as well as leukocyte count, cytology, and protein levels in synovial fluid. PC produced a statistically significant improvement in both the degree of lameness and joint effusion (P < .05). The most marked improvement was observed 2 months after the last treatment and apparently persisted for 8 months. A mean of 250 ± 71.8 × 10⁶ platelets, 8.68 ± 3.78 leukocytes × 10⁶, and 12,515 ± 2,443 pg of TGF-β₁ per milliliter PC were obtained. The evaluated synovial fluid parameters remained between normal values. No adverse clinical signs resulted from this treatment. Despite the seemingly positive effects of this substance, the clinical use of PC cannot be recommended until further studies with higher numbers of cases and longer follow-up can be undertaken.     

In Vitro Model for Testing Novel Implants for Equine Laryngoplasty

Objective— To develop an in vitro laryngeal model to mimic airflow and pressures experienced by horses at maximal exercise with which to test laryngoplasty techniques.
Study Design— Randomized complete block.
Sample Population— Cadaveric equine larynges (n=10).
Methods— Equine larynges were collected at necropsy and a bilateral prosthetic laryngoplasty suture was placed with #5 Fiberwire^™ suture to achieve bilateral maximal arytenoid abduction. Each larynx was positioned in a flow chamber and subjected to static flow and dynamic flow cycling at 2 Hz. Tracheal pressure and flow, and pressure within the flow chamber were recorded at a sampling frequency of 500 Hz. Data obtained were compared with the published physiologic values for horses exercising at maximal exercise.
Results— Under static flow conditions, the testing system produced inspiratory tracheal pressures (mean±SEM) of −33.0±0.98 mm Hg at a flow of 54.48±1.8 L/s. Pressure in the flow chamber was −8.1±2.2 mm Hg producing a translaryngeal impedance of 0.56±0.15 mm Hg/L/s. Under dynamic conditions, cycling flow and pressure were reproduced at a frequency of 2 Hz, the peak inspiratory (mean±SEM) pharyngeal and tracheal pressures across all larynges were −8.85±2.5 and −35.54±1.6 mm Hg, respectively. Peak inspiratory flow was 51.65±2.3 L/s and impedance was 0.57±0.06 mm Hg/L/s.
Conclusions— The model produced inspiratory pressures similar to those in horses at maximal exercise when airflows experienced at exercise were used.
Clinical Relevance— This model will allow testing of multiple novel techniques and may facilitate development of improved techniques for prosthetic laryngoplasty.     

Surgical and Conservative Management of Bilateral Dynamic Laryngeal Collapse Associated with Poll Flexion in Harness Race Horses

Objective— To test the hypothesis that in bilateral dynamic laryngeal collapse associated with poll flexion, vocal fold collapse (VFC) is the initial abnormal event that induces further laryngeal collapse, and that racing performance would therefore be substantially improved after bilateral ventriculocordectomy in affected individuals.
Study Design— Retrospective study.
Animals— Twenty-six horses.
Methods— Medical records (1998–2006) of harness racehorses admitted for high-speed treadmill videoendoscopy (HSTV) that had bilateral dynamic laryngeal collapse associated with poll flexion were reviewed. Race records, owner interviews, and follow-up HSTV were used to evaluate outcome after either surgical treatment including bilateral ventriculocordectomy or conservative management.
Results— Bilateral dynamic laryngeal collapse, defined as bilateral VFC with concurrent arytenoid cartilage collapse (ACC), was identified in 26 horses. Norwegian Coldblooded Trotters (NCT) were overrepresented. Sixteen horses had surgical treatment and 10 were treated conservatively. Return to racing and racing performance was not improved within or between groups after the treatment. On follow-up HSTV of 6 surgically treated horses, there was no residual soft tissue collapse in the ventral portion of the rima glottidis; however, ACC and other abnormalities were still evident.
Conclusion— Bilateral ventriculocordectomy resolved VFC, but failed to stabilize the arytenoid cartilages or to significantly improve racing performance.
Clinical Relevance— Bilateral dynamic laryngeal collapse associated with poll flexion is a serious performance-limiting upper respiratory tract disorder that is overrepresented in NCT racehorses. Our results suggest that VFC is not the initiating event in this complex obstructive airway disorder for which there is currently no consistently effective treatment.     

The influence of inflammation and hematocrit on clot strength in canine thromboelastographic hypercoagulability

Objective

To investigate parameters causing canine thromboelastographic hypercoagulability and to investigate whether thromboelastography (TEG) with Cytochalasin D (Cyt D) added is related to parameters of platelet activity.

Design

Prospective observational study on hemostatic and inflammatory parameters. Data were collected between November 2012 and July 2013.

Setting

University teaching hospital.

Animals

Twenty‐eight dogs suffering from diseases predisposing to thrombosis and 19 clinically healthy dogs. Diseased dogs were enrolled if they fulfilled inclusion criteria regarding age, size, informed client consent, and obtained a diagnosis of a disease that has been associated with thrombosis or hypercoagulability.

Interventions

None.

Measurements and Main Results

Parameters of coagulation and anticoagulation, fibrinolysis, and antifibrinolysis, platelet activity, inflammation, platelet count, and hematocrit were measured using CBC, TEG, platelet aggregation on multiplate, platelet activity on flow cytometry, and hemostatic and inflammatory markers on plasma and serum analyses. ANOVA and multilinear regression analyses indicated that especially hematocrit and the inflammatory parameters C‐reactive protein and interleukin‐8 showed best association with overall clot strength in diseased dogs with hypercoagulable TEG tracings. Ratios presumed to reflect platelet contribution to the TEG tracing obtained in TEG analyses with Cyt D were related especially with hematocrit and P‐selectin expression of platelets measured after γ‐Thrombin activation on flow cytometry.

Conclusion

Overall clot strength in TEG analyses of the hypercoagulable dogs included in the present study appears to be primarily associated with inflammation as well as hematocrit. Furthermore, the ratio between standard TEG analyses and TEG analyses with Cyt D may reflect some degree of platelet activity.