Contrast-enhanced ultrasonography to assess blood perfusion of skeletal muscles in normal dogs

This study evaluated perfusion of skeletal muscle using contrast enhanced ultrasonography in humerus, radius, femur and tibia in normal dogs. Contrast enhanced ultrasonography for each region was performed after injecting 0.5 mL and 1 mL of contrast medium (SonoVue) in every dog. Blood perfusion was assessed quantitatively by measuring the peak intensity, time to the peak intensity and area under the curve from the time–intensity curve. Vascularization in skeletal muscle was qualitatively graded with a score of 0–3 according to the number of vascular signals. A parabolic shape of time–intensity curve was observed from muscles in normal dogs, and time to the peak intensity, the peak intensity and area under the curve of each muscle were not significantly different according to the appendicular regions examined and the dosage of contrast agent administered. This study reports that feasibility of contrast enhanced ultrasonography for assessment of the muscular perfusion in canine appendicular regions.     

Dynamic MRI is reliable for evaluation of the lumbosacral spine in healthy dogs

Magnetic resonance imaging (MRI) is commonly used to diagnose degenerative lumbosacral stenosis; however, studies show limited correlation between imaging and clinical signs. The purpose of this prospective observer agreement study was to use dynamic MRI of the lumbosacral (LS) spine of healthy dogs to determine reliable reference ranges. Twenty‐two healthy large breed dogs were prospectively enrolled. MRI of the LS spine was performed in T2‐weighted, T1‐weighted, and T2‐weighted SPACE sequences in neutral, flexed, and extended positions. Four observers performed image analyses. Measurements included LS angle, vertebral canal height and area, and LS foraminal areas. Ordinal categorical assessment of loss of fat signal in the foramina, LS compression, intervertebral disc (IVD) degeneration, spondylosis, and IVD protrusion was also performed. The majority of values were significantly larger in flexion versus neutral position, and significantly smaller in extension versus neutral position (P < .05). Subclinical compression and IVD protrusion was noted in a neutral position in 45% and 55% of dogs and in an extended position in 85% and 73% of dogs, respectively. Interobserver agreement was strong (intracluster correlation coefficient [ICC] > .5) except for the L7:LS vertebral canal area ratio (ICC ≤ .03). Intraobserver agreement was high (rho > .5) for all measurements except for the mid‐L6:LS vertebral canal height ratio (rho = .38). There was poor interobserver agreement for loss of fat signal in the foramina and evidence of compression. This study provides the groundwork for future studies using dynamic MRI to evaluate dogs with signs of clinical LS disease.     

Femoral and sciatic nerve blockade of the pelvic limb with and without obturator nerve block for tibial plateau levelling osteotomy surgery in dogs

ObjectiveTo determine the effect of blocking the obturator nerve in addition to performing femoral nerve and sciatic nerve blocks on intraoperative nociception in dogs undergoing unilateral tibial plateau levelling osteotomy (TPLO) surgery.Study designProspective, blinded, randomized, placebo-controlled, clinical comparison.AnimalsA total of 88 client-owned dogs undergoing unilateral TPLO surgery (100 procedures).MethodsDogs were randomly assigned to either group FSO (femoral, sciatic and obturator nerve blocks) [n = 50; ropivacaine 0.75% (0.75 mg kg^–1)] or group FSP (femoral, sciatic and placebo) [n = 50; ropivacaine 0.75% (0.75 mg kg^–1) femoral and sciatic nerve blocks plus saline solution 0.9% (0.1 mL kg^–1) as a placebo injection around the obturator nerve]. The anaesthetic protocol was standardized. Data collection included intraoperative cardiopulmonary variables and opioid consumption. Rescue analgesia consisted of an intravenous bolus of fentanyl (2 μg kg^–1) and was administered when a change in cardiopulmonary variables (20% increase in mean arterial pressure or heart rate) was attributed to a sympathetic stimulus. Data were analysed using generalized linear mixed models, cross tables and multivariable binary logistic regression. Results were expressed as adjusted odds ratios with 95% confidence intervals and Wald p values (α = 0.05).ResultsThere were no clinically relevant differences between groups in intraoperative cardiopulmonary variables and need for rescue analgesia. The requirement for rescue analgesia was significantly higher in dogs with a body weight >34 kg.Conclusions and clinical relevanceAnaesthesia of the obturator nerve in addition to the femoral and sciatic nerves was not associated with clinically significant differences in cardiopulmonary variables or a reduced need for rescue analgesia. Therefore, the clinical benefit of an additional obturator nerve block for intraoperative antinociception in dogs undergoing unilateral TPLO surgery using the described anaesthetic regimen is low.     

Contrast-enhanced ultrasonography for characterization of focal splenic lesions in dogs

Background: Contrast‐enhanced ultrasonography with perflubutane microbubbles improves the diagnostic accuracy to differentiate benign and malignant focal liver lesions in dogs. Hypothesis: Perflubutane microbubbles‐enhanced ultrasonography is useful for differentiation of benign from malignant focal splenic lesions in dogs. Animals: Twenty‐nine clinical dogs with single or multiple focal splenic lesions detected by conventional ultrasonography. Methods: Prospective clinical observational study. Perflubutane microbubbles‐enhanced ultrasonography was performed in 29 dogs with focal splenic lesions. Qualitative assessment of the enhancement pattern was performed in the early vascular, late vascular, and parenchymal phases. Results: In the early vascular phase, a hypoechoic pattern was significantly associated with malignancy (P= .02) with sensitivity of 38% (95% confidence interval [CI], 25–38%) and specificity of 100% (95% CI, 84–100%). In the late vascular phase, a hypoechoic pattern was significantly associated with malignancy (P= .001) with sensitivity of 81% (95% CI, 66–90%) and specificity of 85% (95% CI, 65–95%). There was no significant difference between malignant and benign lesions during the parenchymal phase. Conclusions and Clinical Importance: Hypoechoic splenic nodules in the early and late vascular phases with perflubutane microbubbles‐enhanced ultrasonography are strongly suggestive of malignancy in dogs.     

Evaluation of gallbladder volume and contraction index with three-dimensional ultrasonography in healthy dogs

Three-dimensional (3D) ultrasonography has been shown to be an accurate and appropriate tool for measurement of gallbladder volume in humans. Therefore, we applied this novel technique for the first time to study fasting and postprandial gallbladder volume in 10 healthy dogs and compared the results with those of 2-dimensional (2D) ultrasonography. Fasting gallbladder volumes determined by 3D ultrasonography were significantly higher than corresponding volumes determined by 2D ultrasonography (P<0.01). Additionally, gallbladder volumes were significantly decreased in the postprandial state compared with the fasting state using 3D ultrasonography (P<0.001), but 2D ultrasonography showed no significant difference (P=0.189). The Gallbladder contraction index was higher in 3D ultrasonography than 2D ultrasonography; however, it did not reach statistical significance (P=0.25). In conclusion, 3D ultrasonography was able to measure gallbladder volume in healthy dogs in this study. It is suggested that 3D ultrasonography can be used to accurately estimate gallbladder volume and contractility.     

Use of needle enhancing software to improve injection technique amongst inexperienced anaesthetists performing ultrasound‐guided peripheral nerves blocks in dogs

ObjectiveTo determine if the use of needle enhancing software facilitate injection technique in ultrasound‐guided peripheral nerve blocks.Study designProspective, blinded, randomized controlled trial.AnimalsEight hind limbs from canine cadavers.MethodsThe limbs were randomly allocated to two groups; software on (group I) and software off (group II). Eight anaesthetists with no previous experience of ultrasound‐guided regional anaesthesia were recruited. Thirty‐six procedures were carried out (18 per group). After sciatic nerve visualisation via ultrasonography, the anaesthetist introduced a needle guided by ultrasonography. When the tip of the needle was considered by the anaesthetist to be as close as possible to the nerve without touching it, 0.05 mL of methylene blue dye was injected. Parameters evaluated included: number of attempts to visualise the needle with ultrasonography, time spent to perform the technique, subjective evaluation of ease of needle visualisation, proximity of the tip of the needle to the nerve, and, at dissection of the leg, inoculation site of the dye in relation to the nerve.ResultsSignificant differences between groups were identified in relation to the number of attempts (group I: median 1, IQR: 1 – 1 attempts versus group II: median 1, IQR: 1 – 4 attempts, p = 0.019), and the relationship between the dye and the nerve during hind limb dissection (72.2% of the nerves were stained in group I versus 16.6% in group II,p = 0.003). No significant difference between groups was observed with respect to the time taken to perform the procedure (group I: median 25.5, IQR: 18.4 – 44.3 seconds versus group II: median 35.7, IQR: 18.6–78.72 seconds, p = 0.31), subjective evaluation of the needle visualization (p = 0.45) or distance between the tip of the needle and the nerve as measured from the ultrasound screen (p = 0.23).Conclusions and clinical relevanceThis study identified greater success rate in nerve staining when the needle enhancing software was used. The results suggest that the use of this technique could improve injection technique amongst inexperienced anaesthetists performing ultrasound‐guided peripheral nerve blocks in dogs.     

Development and verification of saphenous, tibial and common peroneal nerve block techniques for analgesia below the thigh in the nonchondrodystrophoid dog

OBJECTIVE: To document simple and reliable local, infiltrating nerve blocks for the saphenous, tibial and common peroneal nerves in the dog. STUDY DESIGN: Laboratory technique development; in vivo blind, controlled, prospective study. ANIMALS: Twenty canine cadavers and 18 clinically normal, client-owned dogs. METHODS: A peripheral nerve blockade technique of the tibial, common peroneal, and saphenous nerves was perfected through anatomic dissection. Injections were planned in the caudal thigh for the tibial and common peroneal nerves, and in the medial thigh for the saphenous nerve. Cadaver limbs were injected with methylene blue dye and subsequently dissected to confirm successful dye placement. Clinically normal dogs undergoing general anesthesia for unrelated, elective procedures were randomly assigned to treatment (bupivacaine; n = 8) or control (saline; n = 8) nerve blocks of the nerves under study. Upon recovery from general anesthesia, skin sensation in selected dermatomes was evaluated for 24 hours. RESULTS: Cadaver tibial, common peroneal, and saphenous perineural infiltrations were successful in nonchondrodystrophoid dogs (100, 100, and 97%, respectively.) Intraneural injection was rare (1%; 1/105; tibial nerve) in cadaver dogs. In the treatment group of normal dogs, duration of loss of cutaneous sensation in some dermatomes (saphenous, superficial and deep peroneal nerve) was significantly different than control dogs; the range of desensitization occurred for 1-20 hours. No clinical morbidity was detected. CONCLUSIONS: This technique for local blockade of the tibial, common peroneal, and saphenous nerves just proximal to the stifle is easy to perform, requires minimal supplies and results in significant desensitization of the associated dermatomes in clinically normal, nonchondrodystrophoid dogs. CLINICAL RELEVANCE: This technique may be an effective tool for post-operative analgesia to the femoro-tibial joint and distal pelvic limb. Other applications, using sustained-release drugs or methods, may include anesthesia/analgesia in high-risk patients or as a treatment for chronic pelvic limb pain or self-mutilation.     

3 Tesla magnetic resonance imaging study of the normal canine femoral and sciatic nerves

Understanding the normal course and optimizing visualization of the canine peripheral nerves of the lumbar plexus, in particular the sciatic and the femoral nerves, is essential when interpreting images of patients with suspected peripheral neuropathies such as inflammatory or neoplastic conditions. The purpose of this prospective, anatomic study was to describe the magnetic resonance imaging (MRI) anatomy of the normal canine femoral and sciatic nerves and to define the sequences in which the nerves are best depicted. A preliminary postmortem cadaver study was performed to determine optimal sequences and imaging protocol. In a second step the optimized technique was implemented on 10 healthy Beagle dogs, included in the study. The applied protocol included the following sequences: T1‐weighted, T2‐weighted, T2‐Spectral Attenuated Inversion Recovery, T1‐weighted postcontrast and T1‐Spectral Presaturated Inversion Recovery postcontrast. All sequences had satisfactory signal‐to‐noise ratio and contrast resolution in all patients. The sciatic and femoral nerves were seen in all images. They were symmetric and of homogeneous signal intensity, being iso‐ to mildly hyperintense to muscle on T2‐weighted, mildly hyperintense in T2‐Spectral Attenuated Inversion Recovery, and iso‐ to mildly hypointense in T1‐weighted images. No evidence of contrast enhancement in T1‐weighted and T1‐Spectral Presaturated Inversion Recovery postcontrast sequences was observed. The anatomic landmarks helpful to identify the course of the femoral and sciatic nerves are described in detail. This study may be used as an anatomical reference, depicting the normal canine femoral and sciatic nerves at 3 Tesla MRI.     

Effect of benzodiazepines on the dose of alfaxalone needed for endotracheal intubation in healthy dogs

Objective

To evaluate the dose-sparing effect of midazolam or diazepam on the dose of alfaxalone required to achieve endotracheal intubation in premedicated dogs.

Renal perfusion parameters measured by contrast‐enhanced ultrasound in healthy dogs demonstrate a wide range of variability in the long‐term

Contrast‐enhanced ultrasound may be helpful for detecting early renal microvascular damage and dysfunction in dogs. However, before this noninvasive imaging method can be tested as an early‐stage screening tool in clinical patients, an improved understanding of long‐term variation in healthy animals is needed. In this prospective, secondary, longitudinal, serial measurements study, variability of contrast‐enhanced ultrasound renal perfusion parameters was described for eight healthy dogs, using seven time points and a period of 83 weeks. Dogs were sedated with butorphanol (0.4 mg/kg), and contrast‐enhanced ultrasound of each kidney was performed after an intravenous bolus injection of a microbubble contrast agent (0.04 mL/kg). Time‐intensity curves were created from regions‐of‐interest drawn in the renal cortex and medulla. Intensity‐related parameters representing blood volume and time‐related parameters representing blood velocity were determined. A random‐effects model using restricted maximum likelihood was used to estimate variance components. Within‐dog coefficient of variation was defined as the ratio of the standard deviation over the mean. Time‐related parameters such as time‐to‐peak, rise and fall time had lowest within‐dog variability. Intensity‐related parameters such as peak enhancement, wash‐in and wash‐out area under the curve, total area under the curve, and wash‐in and washout rates had high within‐dog variability (coefficient of variation > 45%). Authors therefore recommend the use of time‐related parameters for future studies of renal perfusion. Within‐dog variability for bilateral kidney measurements was extremely low, therefore contrast‐enhanced ultrasound may be particularly useful for detecting unilateral changes in renal perfusion. Future studies are needed to compare contrast‐enhanced ultrasound findings in healthy dogs versus dogs with renal disease.     

Reference intervals for echocardiographic measurements in healthy Chihuahua dogs

Chihuahuas are one of the most common small breed dogs in Japan, and this breed is known to be predisposed to myxomatous mitral valve disease (MMVD). Echocardiographic assessment is essential for definitive diagnosis of MMVD in dogs as well as determining the stage. Because the Chihuahua’s body size is the smallest among the dog breeds and the widely used echocardiographic reference range is established on the basis of larger dogs, it is unclear whether the existing reference range can be applied to the Chihuahua breed as well. Therefore, this study aimed to determine an echocardiographic reference range for Chihuahua dogs. The left atrial short-axis diameter (LA), aortic valve short-axis diameter, interventricular septum thickness at end-diastole, left ventricular internal dimension at end-diastole (LVIDd), and left ventricular posterior wall thickness at end-diastole from 47 healthy Chihuahuas were analyzed. These parameters increased logarithmically as body weight increased. Furthermore, LA and LVIDd were within the previously established reference range generated primarily from multiple breeds of moderate to large breed dogs.