The effects of 2 different continuous rate infusions (CRIs) of medetomidine over an 8-hour period on sedation score, selected cardiopulmonary parameters, and serum levels of medetomidine were evaluated in 6 healthy, conscious dogs using a crossover study design. The treatment groups were: CONTROL = saline bolus followed by saline CRI; MED1 = 2 μg/kg body weight (BW) medetomidine loading dose followed by 1 μg/kg BW per hour CRI; and MED2 = 4 μg/kg BW medetomidine loading dose followed by 2 μg/kg BW per hour CRI. Sedation score (SS), heart rate (HR), respiratory rate (RR), temperature (TEMP), systolic arterial pressure (SAP), mean arterial pressure (MAP), and diastolic arterial pressure (DAP), arterial and mixed venous blood gas analyses, lactate, and plasma levels of medetomidine were evaluated at baseline, at various intervals during the infusion, and 2 h after terminating the infusion. Statistical analysis involved a repeated measures linear model. Both infusion rates of medetomidine-induced dose-dependent increases in SS and dose-dependent decreases in HR, SAP, MAP, and DAP were measured. Respiratory rate (RR), TEMP, central venous pH, central venous oxygen tension, and oxygen extraction ratio also decreased significantly in the MED2 group at certain time points. Arterial oxygen and carbon dioxide tensions were not significantly affected by either infusion rate. In healthy dogs, both infusion rates of medetomidine-induced clinically relevant sedative effects, accompanied by typical alpha2 agonist-induced hemodynamic effects, which plateaued during the infusion and subsequently returned to baseline. While additional studies in unhealthy animals are required, the results presented here suggest that medetomidine infusions at the doses studied may be useful in canine patients requiring sedation for extended periods.

Objective: To evaluate the precision and accuracy of assessing bone mineral density (BMD) by use of mean gray value (MGV) on digitalized and digital images of conventional and digital radiographs, respectively, of ex vivo bovine and equine bone specimens in relation to the gold-standard technique of dual-energy x-ray absorptiometry (DEXA). Sample: Left and right metatarsal bones from 11 beef cattle and right femurs from 2 horses. Procedures: Bovine specimens were imaged by use of conventional radiography, whereas equine specimens were imaged by use of computed radiography (digital radiography). Each specimen was subsequently scanned by use of the same DEXA equipment. The BMD values resulting from each DEXA scan were paired with the MGVs obtained by use of software on the corresponding digitalized or digital radiographic image. Results: The MGV analysis of digitalized and digital x-ray images was a precise (coefficient of variation, 0.1 and 0.09, respectively) and highly accurate method for assessing BMD, compared with DEXA (correlation coefficient, 0.910 and 0.937 for conventional and digital radiography, respectively). Conclusions and Clinical Relevance: The high correlation between MGV and BMD indicated that MGV analysis may be a reliable alternative to DEXA in assessing radiographic bone density. This may provide a new, inexpensive, and readily available estimate of BMD.

Objective: To determine the pharmacokinetics of ciprofloxacin in dogs, including oral absorption following administration of generic ciprofloxacin tablets. Animals: 6 healthy Beagles. Procedures: In a crossover study design, ciprofloxacin was administered as a generic tablet (250 mg, PO; mean dose, 23 mg/kg) and solution (10 mg/kg, IV) to 6 dogs. In a separate experiment, 4 of the dogs received ciprofloxacin solution (10 mg/mL) PO via stomach tube (total dose, 250 mg). Blood samples were collected before (time 0) and for 24 hours after each dose. Plasma concentrations were analyzed with high-pressure liquid chromatography. Pharmacokinetic analysis was performed by means of compartmental modeling. Results: When ciprofloxacin was administered as tablets PO, peak plasma concentration was 4.4 μg/mL (coefficient of variation [CV], 55.9%), terminal half-life (t1/2) was 2.6 hours (CV, 10.8%), area under the time-concentration curve was 22.5 μg•h/mL (CV, 62.3%), and systemic absorption was 58.4% (CV, 45.4%). For the dose administered IV, t1/2 was 3.7 hours (CV, 52.3%), clearance was 0.588 L/kg/h (CV, 33.9%), and volume of distribution was 2.39 L/kg (CV, 23.7%). After PO administration as a solution versus IV administration, plasma concentrations were more uniform and consistent among dogs, with absorption of 71% (CV, 7.3%), t1/2 of 3.1 hours (CV, 18.6%), and peak plasma concentration of 4.67 μg/mL (CV, 17.6%). Conclusions and Clinical Relevance: Inconsistent oral absorption of ciprofloxacin in some dogs may be formulation dependent and affected by tablet dissolution in the small intestine. Because of the wide range in oral absorption of tablets, the dose needed to reach the pharmacokinetic-pharmacodynamic target concentration in this study ranged from 12 to 52 mg/kg (CV, 102%), with a mean dose of 25 mg/kg, once daily, for bacteria with a minimum inhibitory concentration ≤ 0.25 μg/mL.

Objective: To determine reference values for kaolin-activated thromboelastography in echocardiographically normal cats. Animals: 30 healthy cats without evidence of cardiomyopathy on echocardiographic examination. Procedures: All cats underwent echocardiographic examination, the findings of which were reviewed by a board-certified cardiologist. Cats that struggled (n = 10) received mild sedation with butorphanol and midazolam IM to permit phlebotomy without interruption in jugular venous blood flow. Blood samples were collected for analysis of thromboelastography variables, PCV, total solids concentration, platelet count, activated partial thromboplastin time, prothrombin time, fibrinogen concentration, and antithrombin concentration. Results: All 4 thromboelastography variables had < 5% mean intra-assay variability. Mean values were as follows: reaction time, 4.3 minutes; clotting time, 1.6 minutes; α angle, 66.5°; and maximum amplitude, 56.4 mm. Compared with nonsedated cats, cats that required sedation had a significantly shorter clotting time and greater α angle, whereas reaction time and maximum amplitude were not significantly different. Conclusions and Clinical Relevance: Kaolin-activated thromboelastography was a reliable test with unremarkable intra-assay variability in echocardiographically normal cats. Sedation may affect certain thromboelastography variables, but the effect is unlikely to be clinically important. It remains unknown whether subclinical cardiomyopathy has a significant effect on thromboelastography variables in cats.

Objective: To identify cardiac mechanisms that contribute to adaptation to high altitudes in Tibetan antelope (Pantholops hodgsonii). Animals: 9 male Tibetan antelope and 10 male Tibetan sheep (Ovis aries). Procedures: Tibetan antelope and Tibetan sheep inhabiting a region with an altitude of 4,300 m were captured, and several cardiac variables were measured. Expression of genes for atrial natriuretic peptide, brain natriuretic peptide, and calcium-calmodulin–dependent protein kinase II δ was measured via real-time PCR assay. Results: Ratios of heart weight to body weight for Tibetan antelope were significantly greater than those of Tibetan sheep, but ratios of right-left ventricular weights were similar. Mean ± SD baseline heart rate (26.33 ± 6.15 beats/min) and systolic arterial blood pressure (97.75 ± 9.56 mm Hg) of antelope were significantly lower than those of sheep (34.20 ± 6.57 beats/min and 130.06 ± 17.79 mm Hg, respectively). The maximum rate of rise in ventricular pressure in antelope was similar to that in Tibetan sheep, but after exposure to air providing a fraction of inspired oxygen of 14.6% or 12.5% (ie, hypoxic conditions), the maximum rate of rise in ventricular pressure of the antelope increased significantly to 145.1% or 148.1%, respectively, whereas that of the sheep decreased to 68.4% or 70.5%, respectively. Gene expression of calcium-calmodulin–dependent protein kinase II δ and atrial natriuretic peptide, but not brain natriuretic peptide, in the left ventricle of the heart was significantly higher in antelope than in sheep. Conclusions and Clinical Relevance: Hearts of the Tibetan antelope in this study were well adapted to high-altitude hypoxia as shown by higher heart weight ratios, cardiac contractility in hypoxic conditions, and expression of key genes regulating cardiac contractility and cardiac hypertrophy, compared with values for Tibetan sheep.

Objective: To characterize clinical and behavioral changes in calves following inoculation with Mycoplasma bovis and evaluate relationships between those changes and pulmonary disease. Animals: 22 healthy Holstein steers. Procedures: 20 calves were inoculated intranasally with < 10(8) CFU or > 10(9) CFU of M bovis. Calves were assigned a clinical illness score (CIS) on a scale of 1 through 4 twice daily on the basis of severity of cough, labored breathing, and lethargy. For each calf, distance traveled and time spent near the waterer, feed bunk, or shelter were determined via a remote location monitoring device. Calves were euthanized and necropsied 22 days after inoculation. Results: 13 calves became clinically ill after challenge inoculation; 3 calves were euthanized within 20 days. Among all calves, consolidation was evident in 0% to 79.9% of the lungs; extent of lung consolidation did not differ between the challenge dose groups. Distance traveled and percentages of time spent in proximity to the feed bunk and shelter were associated with CIS; calves with more severe disease traveled less distance and spent less time at the feed bunk and more time in the shelter. Distance traveled by calves was negatively associated with extent of lung consolidation (< or ≥ 10% of lungs affected); this effect was modified by trial day. Conclusions and Clinical Relevance: Following inoculation with M bovis, calf behavior patterns were associated with both CIS and severity of pulmonary disease. Use of behavior monitoring systems may aid in recognition of respiratory tract disease in calves.

Objective: To evaluate aqueous humor flow rate in the eyes of clinically normal cats by use of a noninvasive technique successfully used in other species. Animals: 20 domestic shorthair cats. Procedures: 1 drop of 10% fluorescein sodium was instilled into both eyes of 5 cats every 5 minutes until 3 drops had been administered. Fluorophotometry was performed at 2, 4, 5, 6, 7, 8, 9, and 10 hours after fluorescein application to monitor fluorescein removal and determine aqueous humor flow rate. The 3-drop protocol was used for the remaining 15 cats, and fluorophotometry was performed at 5, 6, 7, and 8 hours after fluorescein application. Aqueous humor flow rates were calculated manually by use of established equations with minor adjustments to constant values to reflect feline anatomic features. Correlation coefficients and slope ratios were calculated to assess the legitimacy of the flow rate data. Paired t tests were calculated to assess for differences between the right and left eyes. Results: Mean ± SD calculated aqueous humor flow rate in the right, left, and both eyes of the 20 cats was 5.94 ± 2.30 μL/min, 5.05 ± 2.06 μL/min, and 5.51 ± 2.21 μL/min, respectively. Correlation coefficients and slope ratios revealed that the aqueous humor flow rates were accurate. No significant differences in values for the right and left eyes were detected. Conclusions and Clinical Relevance: Accurate aqueous humor flow values for cats can be determined by use of the fluorophotometric technique evaluated in this study.

Objective: To compare results of single-point kinetic gait analysis (peak and impulse) with those of complete gait waveform analysis. Animals: 15 healthy adult mixed-breed dogs. Procedures: Dogs were trotted across 2 force platforms (velocity, 1.7 to 2.1 m/s; acceleration and deceleration, 0.5 m/s2). Five valid trials were recorded on each testing day. Testing days 1 and 2 were separated by 1 week, as were days 3 and 4. Testing days 1 and 2 were separated from days 3 and 4 by 1 year. A paired t test was performed to evaluate interday and interyear differences for vertical and craniocaudal propulsion peak forces and impulses. Vertical and craniocaudal propulsion force-time waveforms were similarly compared by use of generalized indicator function analysis (GIFA). Results: Vertical and craniocaudal propulsion peak forces and impulses did not differ significantly between days 1 and 2 or days 3 and 4. When data were compared between years, no significant differences were found for vertical impulse and craniocaudal propulsion peak force and impulse, but differences were detected for vertical peak force. The GIFA of the vertical and craniocaudal force-time waveforms identified significant interday and interyear differences. These results were identical for both hind limbs. Conclusions and Clinical Relevance: Findings indicated that when comparing kinetic data overtime, additional insight may be gleaned from GIFA of the complete waveform, particularly when subtle waveform differences are present.

Objective: To evaluate use of a radiolabeled peptide nucleic acid–peptide conjugate (RaPP) targeting B-cell leukemia-lymphoma 2 (BCL2) mRNA for scintigraphic detection of neoplastic lymphocytes in dogs with B-cell lymphoma and to assess associations among RaPP uptake, time to tumor progression (TTP), and BCL2 mRNA expression. Animals: 11 dogs with B-cell lymphoma and 1 clinically normal dog. Procedures: Scintigraphic images were acquired 1 hour after IV injection of the RaPP. Regions of interest (ROIs) were drawn around lymph nodes, liver, and spleen; ROI intensity (relative to that of an equally sized region of muscle in the same image) was measured. Each ROI was also subjectively categorized as positive or negative for increased RaPP uptake. Expression of BCL2 mRNA was determined via quantitative reverse transcriptase PCR assay of a lymph node sample from dogs with lymphoma. Associations among imaging results, TTP, and BCL2 mRNA expression were evaluated. Results: Increased RaPP uptake was detected in affected tissues of dogs with lymphoma. Dogs with superficial cervical lymph node ROIs categorized as negative (n = 8) for increased RaPP uptake had a significantly longer TTP than did dogs for which this ROI was considered positive (2). Measured intensity of mandibular and superficial cervical lymph node ROIs was negatively associated with TTP. Associations among BCL2 mRNA and ROI intensity or TTP were not significant. Conclusions and Clinical Relevance: Increased RaPP uptake at mandibular or superficial cervical lymph node ROIs may be a negative prognostic indicator in dogs with lymphoma. A larger investigation is needed to determine clinical value of the RaPP for disease detection and prognostication.

Objective: To assess long-term effects and risk factors for the efficacy of hyperimmunization protocols against infectious bovine rhinotracheitis (IBR) during a longitudinal field study of dairy and dairy-beef mixed farms. Animals: Approximately 7,700 cows from 72 farms. Procedures: Farms were assigned to 3 treatment groups (hyperimmunization groups [HIGs] 1 and 2, which were hyperimmunized with glycoprotein E [gE]–deleted marker vaccines, and a nonintervention group [NIG]). Cattle in HIG 1 were initially vaccinated with an attenuated vaccine, whereas cattle in HIG 2 were initially vaccinated with an inactivated-virus vaccine. Cattle in both HIGs received booster inoculations with inactivated-virus vaccines at 6-month intervals. The risk for gE seroconversion was compared among experimental groups via a shared frailty model with a piecewise constant baseline risk to correct for seasonal and secular effects. Results: Risk for gE seroconversion significantly decreased over time for the HIGs, compared with the NIG. Seasonal changes in the risk of gE seroconversion were detected, with a higher risk during winter periods, compared with grazing periods. No significant difference was detected between HIGs 1 and 2. The only significant risk factor was the number of buildings for cattle on a farm; the higher the number of buildings, the lower the risk for gE seroconversion. Prevalence of IBR decreased over time in both HIGs but remained constant or increased in the NIG. Conclusions and Clinical Relevance: Hyperimmunization via repeated administration of attenuated and inactivated-virus gE-deleted marker vaccines as well as inactivated-virus vaccines may provide a method for control of IBR.