Search Results

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)

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)

Abstract

Objective—To measure the radial and longitudinal velocities of several myocardial segments of the left ventricular wall by use of tissue Doppler imaging (TDI) in healthy cats and determine the repeatability and reproducibility of the technique.

Animals—6 healthy cats.

Procedure—72 TDI examinations were performed on 4 days by the same trained observer. Radial parameters included left endocardial and epicardial myocardial velocities. Longitudinal parameters included left basal, middle, and apical myocardial velocities.

Results—All velocity profiles had 1 positive systolic wave (S) and 2 negative diastolic waves (E and A). Myocardial velocities were higher in the endocardial than epicardial segments during the entire cardiac cycle (systolic wave S, 4.4 ± 0.82 and 1.9 ± 0.55; diastolic wave E, 9.7 ± 1.70 and 2.2 ± 0.74; and diastolic wave A, 5.1 ± 1.56 and 1.4 ± 0.76, respectively). Velocities were also higher in the basal than in the apical segments (systolic wave S, 4.7 ± 0.76 and 0.2 ± 0.11; diastolic wave E, 9.7 ± 1.36 and 0.5 ± 0.17; and diastolic wave A, 3.7 ± 1.51 and 0.2 ± 0.13, respectively). The lowest within-day and between-day coefficients of variation were observed in endocardial segments (8.2% and 6.5% for systolic wave S and diastolic wave E, respectively) and in the basal segment in protodiastole (5.5%).

Conclusions and Clinical Relevance—Repeatability and reproducibility of TDI were adequate for measurement of longitudinal and radial left ventricular motion in healthy awake cats. Validation of TDI is a prerequisite before this new technique can be recommended for clinical use. ( Am J Vet Res 2004; 65:566–572)

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)

Abstract

Objective—To establish reference intervals of plasma biochemical values in healthy adult domestic shorthair (DSH) cats by use of controlled conditions.

Animals—95 healthy client-owned cats.

Procedures—Food was withheld from the cats overnight. All blood samples were obtained on the same day, at the same location, and by the same investigator. Blood samples were collected from a cephalic vein into lithium heparin tubes. After centrifugation of blood samples, plasma supernatants were harvested and stored at −20°C until assayed for total proteins, albumin, creatinine, urea, glucose, calcium, phosphates, sodium, chloride, potassium, and CO₂ concentrations and alkaline phosphatase and alanine aminotransferase activities.

Results—Reference intervals in healthy adult DSH cats were 65 to 85 g/L for total proteins, 27 to 39 g/L for albumin, 89 to 207 μmol/L for creatinine, 6.6 to 11.3 mmol/L for urea, 4.1 to 8.2 mmol/L for glucose, 2.4 to 2.9 mmol/L for calcium, 1.1 to 2.1 mmol/L for phosphates, 153 to 161 mmol/L for sodium, 120 to 127 mmol/L for chloride, 3.3 to 4.2 mmol/L for potassium, 15 to 21 mmol/L for CO₂, 32 to 147 U/L for alkaline phosphatase, and 34 to 123 U/L for alanine aminotransferase.

Conclusions and Clinical Relevance—This study provided reference intervals for plasma analytes in adult DSH cats. The influence of potential confounding factors was minimized through use of controlled preanalytic and analytic conditions. However, these results cannot be extrapolated to other feline breeds or used to interpret results from other biochemical analyzers.

Abstract

Objective—To determine left ventricular free wall (LVFW) motions and assess their intra- and interday variability via tissue Doppler imaging (TDI) in healthy awake and anesthetized dogs.

Animals—6 healthy adult Beagles.

Procedure—In the first part of the study, 72 TDI examinations (36 radial and 36 longitudinal) were performed by the same observer on 4 days during a 2-week period in all dogs. In the second part, 3 dogs were anesthetized with isoflurane and vecuronium. Two measurements of each TDI parameter were made on 2 consecutive cardiac cycles when ventilation was transiently stopped. The TDI parameters included maximal systolic, early, and late diastolic LVFW velocities.

Results—The LVFW velocities were significantly higher in the endocardial than in the epicardial layers and also significantly higher in the basal than in the midsegments in systole, late diastole, and early diastole. The intraday coefficients of variation (CVs) for systole were 16.4% and 22%, and the interday CV values were 11.2% and 16.4% in the endocardial and epicardial layers, respectively. Isoflurane anesthesia significantly improved the intraday CV but induced a decrease in LVFW velocities, except late diastolic in endocardial layers and early diastolic in epicardial layers.

Conclusions and Clinical Relevance—Left ventricular motion can be adequately quantified in dogs and can provide new noninvasive indices of myocardial function. General anesthesia improved repeatability of the procedure but cannot be recommended because it induces a decrease in myocardial velocities. (Am J Vet Res 2004;65:909–915)

Abstract

Objective—To evaluate the effects of positioning and number of repeated measurements on intra- and interobserver variability of echocardiographic measurements in dogs.

Design—Prospective study.

Animals—4 healthy dogs.

Procedure—Each observer performed 24 examinations, separately assessing each dog 6 nonconsecutive times (3 times with the dog in lateral recumbency and 3 with the dog in a standing position). Variables evaluated included M-mode measurements of left ventricular end-diastolic and left ventricular endsystolic diameters, left ventricular free-wall thickness in diastole and systole, interventricular septal thickness in diastole and systole, left ventricular shortening fraction, and 2-dimensional measurements of the left atrial diameter-to-aortic diameter ratio.

Results—All coefficients of variation (range, 3.4% to 26.6%) were similar between operators and positions and were < 15% for 27 of 32 values. For both operators, repeatability of the measurements was better for left ventricular end-systolic diameter, left ventricular free-wall thickness in diastole, left ventricular freewall thickness in systole, and the left atrial diameterto- aortic diameter in the standing position, and similar for both positions for shortening fraction and left ventricular end-diastolic diameter. No effect of cardiac cycle was observed.

Conclusions and Clinical Relevance—Within-day variability of conventional echocardiography performed with the dog in the standing position was at least as good as that obtained with the dog in lateral recumbency for most measured variables. Single measurements of each variable may be sufficient for trained observers examining dogs that do not have an arrhythmia. The standing position should be used, particularly for stressed or dyspneic dogs. (J Am Vet Med Assoc 2005;227:743–747)

Abstract

Objective—To determine left ventricular free wall (LVFW) radial and longitudinal myocardial contraction velocities in healthy dogs via quantitative 2-dimensional color tissue Doppler imaging (TDI).

Animals—100 dogs.

Procedure—TDI was used by a single trained observer to measure radial and longitudinal myocardial movement in the LVFW. Radial myocardial velocities were recorded in segments in the endocardial and epicardial layers of the LVFW, and longitudinal velocities were recorded in segments at 3 levels (basal, middle, apical) of the LVFW.

Results—LVFW velocities were higher in the endocardial layers than in the epicardial layers. Left ventricular free wall velocities were higher in the basal segments than in the middle and apical segments. Radial myocardial velocity gradients, defined as the difference between endocardial and epicardial velocities, were (mean ± SD) 2.5 ± 0.8 cm/s, 3.8 ± 1.5 cm/s, and 2.3 ± 0.9 cm/s in systole, early diastole, and late diastole, respectively. Longitudinal myocardial velocity gradients, defined as the difference between basal and apical velocities, were 5.9 ± 2.2 cm/s, 6.9 ± 2.5 cm/s, and 4.9 ± 1.7 cm/s in systole, early diastole, and late diastole, respectively. A breed effect was detected for several systolic and diastolic TDI variables. In all segments, systolic velocities were independent of fractional shortening.

Conclusions and Clinical Relevance—LVFW myocardial velocities decreased from the endocardium to the epicardium and from base to apex, thus revealing intramyocardial radial and longitudinal velocity gradients. These indices could enhance conventional echocardiographic analysis of left ventricular function in dogs. Breed-specific reference intervals should be defined. (Am J Vet Res 2005;66:953–961)

Abstract

Objective—To determine the within-day and between-day variability of regurgitant fraction (RF) assessed by use of the proximal isovelocity surface area (PISA) method in awake dogs with degenerative mitral valve disease (MVD), measure RF in dogs with MVD, and assess the correlation between RF and several clinical and Doppler echocardiographic variables.

Design—Prospective study.

Animals—6 MVD-affected dogs with no clinical signs and 67 dogs with MVD of differing severity (International Small Animal Cardiac Health Council [ISACHC] classification).

Procedures—The 6 dogs were used to determine the repeatability and reproducibility of the PISA method, and RF was then assessed in 67 dogs of various ISACHC classes. Mitral valve regurgitation was also assessed from the maximum area of regurgitant jet signal-to-left atrium area (ARJ/LAA) ratio determined via color Doppler echocardiographic mapping.

Results—Within- and between-day coefficients of variation of RF were 8% and 11%, respectively. Regurgitation fraction was significantly correlated with ISACHC classification and heart murmur grade and was higher in ISACHC class III dogs (mean ± SD, 72.8 ± 9.5%) than class II (57.9 ± 20.1%) or I (40.7 ± 19.2%) dogs. Regurgitation fraction and left atriumto-aorta ratio, fractional shortening, systolic pulmonary arterial pressure, and ARJ/LAA ratio were significantly correlated.

Conclusions and Clinical Relevance—Results suggested that RF is a repeatable and reproducible variable for noninvasive quantitative evaluation of mitral valve regurgitation in awake dogs. Regurgitation fraction also correlated well with disease severity. It appears that this Doppler echocardiographic index may be useful in longitudinal studies of MVD in dogs.

Abstract

Objective—To determine the intra- and interobserver variability of systolic arterial pressure (SAP) and diastolic arterial pressure (DAP) measurements obtained with 2 indirect methods in awake dogs and percentage of successful measurements.

Animals—6 healthy conscious adult dogs.

Procedures—4 observers with different levels of training measured SAP and DAP on 4 days by use of Doppler ultrasonography (DU) and high-definition oscillometry (HDO). The examinations were randomized. Measurements for each technique were recorded 5 consecutive times, and mean values (total, 720 measurements) were used for statistical analysis.

Results—All within- and between-day coefficients of variation (CVs) for SAP were < 15% irrespective of the observer or method (HDO, 3.6% to 14.1%; DU, 4.1% to 12.4%). Conversely, half the CVs for DAP were > 15% with the highest within- and between-day CVs obtained by the least experienced observer by use of DU (19.5% and 25.9%, respectively). All attempts with HDO were successful, whereas DAP could not be measured by use of DU by the least experienced observer in 17% of attempts.

Conclusions and Clinical Relevance—SAP may be assessed in healthy dogs by use of DU and HDO with good repeatability and reproducibility after a short period of training. Conversely, the variability of DAP is higher and longer training is required to assess DAP via DU than via HDO.