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Abstract

Case Description—A 7-year-old 23-kg (50.6-lb) spayed female Border Collie with a history of heartworm disease was evaluated for respiratory distress.

Clinical Findings—Computed tomography of the thorax revealed possible pulmonary bullae or blebs, and on the basis of these findings, a tentative diagnosis of bullous emphysema was made.

Treatment and Outcome—Exploratory median sternotomy revealed gross pathological lesions in the right caudal lung lobe; the most peripheral portion appeared discolored (pale pink), and a clear line of demarcation was observed. Upon excision of the affected lung lobe, a worm segment was noticed both on the remaining stump of the lung lobe in the dog and in the removed lobe. At this time, the dog had an anaphylactoid reaction. The reaction was successfully treated with fluid therapy, antihistamines, and corticosteroids. Lung lobectomy of the right caudal lobe resulted in clinical resolution of the bilateral pneumothorax. However, during the postoperative period, the dog developed a hemothorax and was returned to surgery. As no obvious cause for the hemothorax was seen at the second surgery, the dog was treated for a potential coagulopathy with fresh frozen plasma, which provided clinical resolution of the hemothorax. Parasitological examination of the worm segment confirmed a Dirofilaria immitis infection. The dog was discharged 5 days after surgery and treated with doxycycline for 30 days and monthly administration of heartworm preventative was prescribed.

Clinical Relevance—Heartworm infection should be a differential diagnosis in dogs with spontaneous pneumothorax. Anaphylactoid reactions associated with accidental dissection of adult heartworms should be managed with treatment aimed at cardiovascular stabilization.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To compare 5 radiographic views for the detection of osteochondritis dissecans (OCD) in dogs with signs of elbow joint pain.

Animals—53 dogs (100 elbow joints) with forelimb lameness and signs of elbow joint pain.

Procedures—Mediolateral (ML), flexed ML, craniocaudal (CC), craniolateral-caudomedial oblique (Cr15L-CdMO), and distomedial-proximolateral oblique (Di35M-PrLO) radiographic views of the 100 elbow joints were obtained. Four examiners graded radiographs with regard to elbow joint OCD. Joints were assessed by use of arthroscopy. Receiver operating characteristic (ROC) curves, kappa measure of agreement, and Fisher exact tests for association between median diagnostic value and actual status were computed.

Results—47 joints had an abnormal medial aspect of the humeral condyle (MAHC), and among them, 11 had OCD. The presence of fractures of the medial coronoid process was significantly and positively correlated with the presence of abnormalities of the MAHC (r = 0.40), but was negatively correlated with the presence of OCD (r = −0.32). At 95% specificity, median sensitivities to detect OCD were 57% for Cr15L-CdMO, 56% for CC, 10% for flexed ML, 7% for ML, and 4% for Di35M-PrLO views. The areas under the ROC curves were significantly larger for the Cr15L-CdMO and CC views than for the ML, flexed ML, and Di35M-PrLO views for the detection of OCD. Only the Cr15L-CdMO and CC views allowed accurate detection of OCD.

Conclusions and Clinical Relevance—In dogs with signs of elbow joint pain, the Cr15L-CdMO view is excellent and the CC view was good for detection of OCD.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To study the hemodynamic effects of marbofloxacin (MBF) in isoflurane-anesthetized dogs.

Animals—6 healthy 8-month-old Beagles.

Procedure—Anesthesia was induced with sodium thiopental and maintained with isoflurane. Cardiovascular variables were monitored throughout anesthesia. Marbofloxacin was administered by an IV bolus at 2 mg/kg, followed 10 minutes later by an infusion at a rate of 40 mg/kg/h for 30 minutes (total dose, 20 mg/kg). Plasma MBF concentrations were measured by high-performance liquid chromatography.

Results—The mean peak concentration during MBF infusion was 34.2 ± 6.4 µg/mL. The IV administration of the MBF bolus did not alter any cardiovascular variable in isoflurane-anesthetized dogs. Significant changes were found during infusion when a cumulative dose of 12 mg/kg had been given. The maximal decreases observed at the end of the infusion were 16% in heart rate, 26% in systolic left ventricular pressure, 33% in systolic aortic pressure, 38% in diastolic aortic pressure, 29% in cardiac output, and 12% in QT interval. All dogs recovered rapidly from anesthesia at the end of the experiment.

Conclusions and Clinical Relevance—MBF may safely be used at 2 mg/kg IV in isoflurane-anesthetized dogs, and significant adverse cardiovascular effects are found only when 6 to 8 times the recommended dose is given. (Am J Vet Res 2005;66:2090–2094)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the electrical impulse duration thresholds (chronaxy) for maximal motor contraction of various muscles without stimulation of pain fibers in dogs.

Animals—10 healthy adult Beagles.

Procedures—The dogs were used to assess the minimal intensity (rheobase) required to elicit motor contraction of 11 muscles (5 in the forelimb [supraspinatus, infraspinatus, deltoideus, lateral head of the triceps brachii, and extensor carpi radialis], 5 in the hind limb [gluteus medius, biceps femoris, semitendinosus, vastus lateralis, and tibialis cranialis], and the erector spinae). The rheobase was used to determine the chronaxy for each of the 11 muscles in the 10 dogs; chronaxy values were compared with those reported for the corresponding muscles in humans.

Results—Compared with values in humans, chronaxy values for stimulation of AA motor fibers in the biceps femoris and semitendinosus muscles and muscles of the more distal portions of limbs were lower in dogs. For the other muscles evaluated, chronaxy values did not differ between dogs and humans.

Conclusions and Clinical Relevance—Application of the dog-specific chronaxy values when performing electrical stimulation for strengthening muscles or providing pain relief is likely to minimize the pain perceived during treatment in dogs.

Full access
in American Journal of Veterinary Research

Abstract

Case Description—A 6-year-old Siberian Husky–mix dog was examined for episodes of collapse.

Clinical Findings—Physical examination, echocardiography, abdominal ultrasonography, ECG, and thoracic computed tomography with contrast were performed and revealed a 2.5 × 2.3 × 2.0-cm mass over the pulmonic valve leaflets, resulting in moderate pulmonic stenosis. Other abnormal findings included systemic hypertension, right bundle branch block, proteinuria, and a urinary bladder mass.

Treatment and Outcome—Pulmonary arteriotomy was performed under inflow occlusion, and the mass was resected with transesophageal echocardiographic guidance and direct visualization. Results of histologic examination of the mass revealed a vascular hamartoma. Sequential follow-up examinations and telephone contacts (at 0.5, 5, and 15 months after surgery) revealed that the patient had been free from episodes of collapse since surgery. No regrowth of the mass was noted on follow-up echocardiograms, and the pulmonic stenosis had resolved, although mild to moderate pulmonary insufficiency later developed. The bladder mass was excised 15 months after the first surgery when hematuria developed, and results of histologic examination of this mass revealed a vascular hamartoma. The dog was eventually euthanized 31 months after the initial surgery for reasons that could not be directly linked to any recurrence of the pulmonary artery mass.

Clinical Relevance—Hamartomas are benign tumors that can be located in various tissues, including large arteries. Computed tomography was helpful in predicting the resectability of the intracardiac mass in this dog. Treatment with arteriotomy under inflow occlusion and mild hypothermia resulted in a favorable outcome.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To assess the effects of moderate exercise on plasma creatine kinase (CK) pharmacokinetics and to estimate exercise-induced muscle damage in dogs.

Animals—6 untrained adult Beagles.

Procedure—The study was divided into 3 phases. In phase 1, dogs ran for 1 hour at a speed of 9 km/h, and samples were used to determine the area under the plasma CK activity versus time curve (AUC) induced by exercise. In phases 2 and 3, pharmacokinetics of CK were calculated in dogs during exercise and at rest, respectively. Values for AUC and plasma clearance (Cl) were used to estimate muscle damage.

Results—At rest, values for Cl, steady-state volume of distribution (Vdss), and mean retention time (MRT) were 0.32 ± 0.02 ml/kg of body weight/min, 57 ± 17.3 ml/kg, and 3.0 ± 0.57 h, respectively. During exercise, Cl decreased significantly (0.26 ± 0.03 ml/kg/min), MRT increased significantly, (4.4 ± 0.97 h), and Vdss remained unchanged. Peak of plasma CK activity (151 ± 58.8 U/L) was observed 3 hours after completion of exercise. Estimated equivalent amount of muscle corresponding to the quantity of CK released was 41 ± 29.3 mg/kg.

Conclusion and Clinical Relevance—These results revealed that exercise had a minor effect on CK disposition and that the equivalent amount of muscle damaged by moderate exercise was negligible. This study illustrates the relevance for use of the minimally invasive and quantitative pharmacokinetic approach when estimating muscle damage. (Am J Vet Res 2001;62:1375–1380)

Full access
in American Journal of Veterinary Research

Abstract

Objectives—To investigate and validate noninvasive methods for the quantitative evaluation of postinjection muscle damage.

Animals—5 adult sheep.

Procedures—Muscle lesions were induced twice in the lumbar region of the longissimus dorsi muscles (2 sides) by IM administration of a 20% formulation of long-acting oxytetracycline (20 mg/kg of body weight). Clinical signs and local cutaneous temperature above the injection site were recorded. Muscle lesions were quantitatively evaluated by ultrasonography and by use of pharmacokinetic analysis of plasma creatine kinase activity, and both were compared with a comprehensive planimetric computer-assisted analysis of the injection sites after euthanasia.

Results—Transient cutaneous hypothermia (temperature change, –3.9 ± 0.62 C) and subsequent persistent hyperthermia (3.1 ± 1.35 C) were observed after the administrations. Despite coefficient of variation < 10% for precision of ultrasonographic measurement of normal muscle, measurements of the lesions, with coefficient of variation > 60% for precision, were systematically underestimated. Quantitative evaluation of muscle damage by use of pharmacokinetic analysis of creatine kinase (12.1 ± 4.96 g) was in agreement with results of macroscopic planimetric evaluation (10.8 ± 3.64 g).

Conclusions and Clinical Relevance—Ultrasonography cannot be used for quantitative assessment of postinjection muscle damage. Pharmacokinetic analysis of creatine kinase provides an accurate quantitative evaluation of macroscopic muscle damage after IM administration of drugs. (Am J Vet Res 2001;62:1698–1705)

Full access
in American Journal of Veterinary Research