Comparison of three techniques for paravertebral brachial plexus blockade in dogs

ObjectiveTo compare success and complication rates, based on staining of nerves and other structures, among three techniques of paravertebral brachial plexus blockade (PBPB) in dogs.Study designProspective randomized design.AnimalsA total of 68 thoracic limbs from 34 dogs.MethodsLimbs were randomly assigned to blind (BL) (n = 24), nerve stimulator-guided (NS) (n = 21) or ultrasound-guided (US) (n = 23) technique. Injections were made with 0.3 mL kg^?1 of lidocaine mixed with new methylene blue. Time to perform each block and current used during NS technique were recorded. Dogs were anesthetized during the blocks and euthanized once completed. Dissections were performed to evaluate staining of nerves, spinal cord, mediastinum, pleura and vessels. An anova and Tukey adjustment for time, logistic regression for association between current and nerve staining and a generalized linear mixed model for staining of different structures were used. Significance was considered when p ≤ 0.05.ResultsThe median (range) number of nerves stained was 2 (0–4) with BL, 1 (0–3) with NS and 1 (0–4) with US guided technique. No significant differences in staining of C6, C8 and T1 or other structures were found among techniques. Nerve C7 was more likely to be stained by BL (p = 0.05). Time to perform the blocks was significantly different among techniques, with mean ± SD duration in minutes of 3.6 ± 1.8 with BL, 6.3 ± 2.7 with US and 12.2 ± 5 with NS. The most common complication was staining of the spinal cord (29%, 38% and 39% with BL, NS and US, respectively).ConclusionsSuccess rates were low and complication rates were relatively high, based on staining, with the three techniques.Clinical relevanceThe use of more advanced techniques for PBPB in dogs is not justified according to this study. Clinical significance of the complications encountered in this study should be evaluated.     

Distribution of a lidocaine-methylene blue solution staining in brachial plexus, lumbar plexus and sciatic nerve blocks in the dog

ObjectiveTo determine the influence on the distribution of the volume of a local anaesthetic-methylene blue solution at three different nerve block sites in the dog.Study designRandomized, controlled, blinded experimental trial.Animals23 hound-cross dogs weighing 16–40 kg and aged 2 ± 0 years (mean ± SD).MethodsDogs were anaesthetized and randomly assigned to three groups of seven or eight dogs each, based on volume administered: low, medium and high volume (L, M and H). Using electrolocation, the injection was performed after a positive response was elicited (flexion of the elbow for the brachial plexus block, quadriceps contractions for the lumbar plexus and dorsiflexion/plantar extension of the foot for the sciatic nerve block). At the brachial plexus site, groups L, M and H received 0.075, 0.15 and 0.3 mL kg⁻¹, respectively. At the lumbar plexus site, groups L, M and H received 0.1, 0.2 and 0.4 mL kg⁻¹, respectively. At the proximal sciatic nerve site, groups L, M and H received 0.05, 0.1 and 0.25 mL kg⁻¹, respectively. Necropsies were performed immediately following euthanasia. Staining of ≥2 cm along the nerve was considered sufficient; the proportions sufficient were compared with Fisher's exact test. The volume was recommended when all the relevant nerves were stained sufficiently in all or all but one of the dogs within the group.ResultsIn the brachial plexus, only in group H were all the nerves stained sufficiently. In the lumbar plexus site, no statistical difference was found, but we suggest the H group volume to balance sufficient and excessive staining. At the sciatic nerve site, all volumes tested produced sufficient staining in all (or all but one) dogs.Conclusions and clinical relevanceVolumes of 0.3 and 0.05 mL kg⁻¹ produced sufficient distribution for performing brachial plexus, and sciatic nerve blocks, respectively. Additionally, a volume of 0.4 mL kg⁻¹ might also be adequate for a lumbar plexus block (no statistical significance was reached).     

Comparison of ultrasound- and electrostimulation-guided nerve blocks of brachial plexus in dogs

Objective

To compare the effectiveness of ultrasound- and electrostimulation-guided nerve blocks of the brachial plexus and to determine whether ultrasound guidance is feasible in conscious dogs.

Ultrasound‐guided approach for axillary brachial plexus,femoral nerve,and sciatic nerve blocks in dogs

Objective To describe an ultrasound‐guided technique and the anatomical basis for three clinically useful nerve blocks in dogs. Study design Prospective experimental trial. Animals Four hound‐cross dogs aged 2 ± 0 years (mean ± SD) weighing 30 ± 5 kg and four Beagles aged 2 ± 0 years and weighing 8.5 ± 0.5 kg. Methods Axillary brachial plexus, femoral, and sciatic combined ultrasound/electrolocation‐guided nerve blocks were performed sequentially and bilaterally using a lidocaine solution mixed with methylene blue. Sciatic nerve blocks were not performed in the hounds. After the blocks, the dogs were euthanatized and each relevant site dissected. Results Axillary brachial plexus block Landmark blood vessels and the roots of the brachial plexus were identified by ultrasound in all eight dogs. Anatomical examination confirmed the relationship between the four ventral nerve roots (C6, C7, C8, and T1) and the axillary vessels. Three roots (C7, C8, and T1) were adequately stained bilaterally in all dogs. Femoral nerve block Landmark blood vessels (femoral artery and femoral vein), the femoral and saphenous nerves and the medial portion of the rectus femoris muscle were identified by ultrasound in all dogs. Anatomical examination confirmed the relationship between the femoral vessels, femoral nerve, and the rectus femoris muscle. The femoral nerves were adequately stained bilaterally in all dogs. Sciatic nerve block. Ultrasound landmarks (semimembranosus muscle, the fascia of the biceps femoris muscle and the sciatic nerve) could be identified in all of the dogs. In the four Beagles, anatomical examination confirmed the relationship between the biceps femoris muscle, the semimembranosus muscle, and the sciatic nerve. In the Beagles, all but one of the sciatic nerves were stained adequately. Conclusions and clinical relevance Ultrasound‐guided needle insertion is an accurate method for depositing local anesthetic for axillary brachial plexus, femoral, and sciatic nerve blocks.     

Anatomical characterization of the brachial plexus in dog cadavers and comparison of three blind techniques for blockade

Objectives

To describe the ventral spinal nerve rami contribution to the formation of the brachial plexus (BP), and to compare ease of performing and nerve staining between three blind techniques for BP blockade in dogs.

A new brachial plexus block technique in dogs

Objective To evaluate the feasibility and efficacy of a new technique of brachial plexus anesthesia in dogs. Study design Prospective, experimental study. Animals Twelve adult mongrel dogs, six males and six females weighing 14.8 ± 1.75 kg. Methods The animals were sedated with acepromazine 0.05 mg kg^?1 and anesthetized with propofol (6 mg kg^?1, IV bolus) followed by an infusion of 212 µg kg^?1 minute^?1. The brachial plexus block technique was performed utilizing the brachial artery as an anatomic landmark, the needle was inserted from the axilla and a nerve stimulator was used to ensure the accuracy of needle placement. Bupivacaine (0.375% with 5 µg mL^?1 epinephrine) was used at a dose rate of 4 mg kg^?1. Dogs underwent mid‐diaphyseal osteotomies of the humerus followed by intramedullary pin fixation. Results Onset time to motor and sensory block were 9.70 ± 5.52 and 26.20 ± 8.86 minutes, respectively. Analgesia lasted for 11.11 ± 0.47 hours. The block was effective in 91.6% of the animals, being verified by anesthesia of the whole front limb distal to the shoulder. One animal became hypotensive after the block and did not undergo the surgery at that time. In the remaining 10 animals the heart and respiratory rates, blood pressure, blood gas parameters and plasma bicarbonate concentration did not show any statistically significant alterations during the surgical procedure. Conclusions This brachial plexus block technique is effective in most cases to provide surgical analgesia for the front limb distal to the shoulder. Clinical Relevance Various surgical procedures in the front limb can be performed with a regional anesthetic technique without the use and concomitant risks of general anesthesia in dogs. Long‐lasting analgesia associated with this technique may also provide a valuable tool for the management of pain in the forelimb.     

Computed tomographic anatomy of the canine cervical vertebral venous system

Computed tomographic (CT) venography of the cervical vertebral canal was performed in six, clinically normal, adult mixed-breed dogs from 14 to 23 kg. After dogs were euthanized and saline perfused, a gelatin and iothalamate mixture was injected into the right external jugular vein. Contiguous, 4-mm-thick CT images were obtained with dogs in sternal recumbency. Dogs were kept in the same position as for the CT scan and frozen to approximately -8 degrees C. All post-contrast CT images were analyzed using similar bone window and level settings. Additional multiplanar reformatted dorsal images were obtained in all dogs. The frozen cadavers were sectioned through the cervical region extending from the occiput to T1 at approximately 8-mm intervals. The frozen sections were then compared with the CT images. The CT appearance of the normal cervical vertebral venous system was described and illustrated. Components such as the internal vertebral venous plexus, interarcuate veins, intervertebral veins, and vertebral veins were clearly identified on the CT images.     

Anatomical and experimental studies of brachial plexus, sciatic, and femoral nerve-location using peripheral nerve stimulation in the dog

OBJECTIVE: To investigate the anatomy of the brachial plexus, sciatic, and femoral nerves for the use of a peripheral nerve-stimulator to perform nerve blocks in dogs. STUDY DESIGN: Prospective experimental trial. ANIMALS: Four canine cadavers and four healthy adult dogs weighing 23 +/- 2.5 kg. METHODS: Phase I: in four canine cadavers, an anatomical study was conducted to evaluate accurate needle-insertion techniques. Phase II: the utility of these techniques, and the value of electrostimulation, were evaluated in four anesthetized dogs in lateral recumbency (medetomidine, 5 microg kg(-1)/ketamine 5 mg kg(-1)) using an electrical stimulator and shielded needles. RESULTS: For the brachial plexus, the needle was inserted cranial to the acromion, medial to the subscapularis muscle, at an angle of approximately 20-30 degrees in relation to a plane vertical to the surface on which the animal was lying, oriented parallel to the long axis of the animal, in a ventro-caudal direction. For the sciatic nerve, the needle was inserted just cranial to the sacrotuberous ligament, through the gluteus superficialis muscle, at an angle of approximately 60 degrees in relation to the horizontal plane, in a ventro-cranial direction, and up to the level of the ischium. For the femoral nerve, the needle was inserted perpendicular to the skin, just cranial to the femoral artery, and directed a little caudally. Using a peripheral nerve-stimulator, all nerves were located, and muscle contractions were elicited at a current of 0.2-0.4 mA. No complications were observed during the procedures. CONCLUSION: Electrostimulation of peripheral nerves is useful in locating the branches of the brachial plexus as well as the sciatic and femoral nerves in dogs. CLINICAL RELEVANCE: Peripheral nerve stimulation increases the reliability of a nerve block when compared with blind needle-insertion.     

Electrical nerve stimulation to facilitate placement of an indwelling catheter for repeated brachial plexus block in a traumatized dog

A 10-year-old, 7 kg, male mixed breed dog was presented, following a dog fight, with open fractures of the radius and ulna and extensive skin and muscle lesions. Using electric nerve stimulation, an indwelling catheter was positioned in the axillary space and 2 mg kg(-1) bupivacaine was injected. Complete sensory and motor blocks were obtained allowing amputation distal to the non-traumatized tissue and debridement of the limb. The injection of bupivicaine was repeated 5 hours after the first bolus and a similar result was obtained in term of muscle relaxation and pain alleviation. Subsequent injections were not successful in providing the same effect, most likely as a result of catheter displacement and alternate means of analgesia were used.     

Computed tomographic evaluation of cervical vertebral canal and spinal cord morphometry in normal dogs

The height, width, and cross-sectional area of the vertebral canal and spinal cord along with the area ratio of spinal cord to vertebral canal in the cervical vertebra were evaluated in images obtained using computed tomography (CT). Measurements were taken at the cranial, middle, and caudal point of each cervical vertebra in eight clinically normal small breed dogs (two shih tzu, two miniature schnauzers, and four mixed breed), 10 beagles, and four German shepherds. CT myelography facilitated the delineation of the epidural space, subarachnoid space, and spinal cord except at the caudal portion of the 7th cervical vertebra. The spinal cord had a tendency to have a clear ventral border in the middle portion of the vertebral canal and lateral borders near both end plates. The height, width, and area of the vertebral canal and spinal cord in the cervical vertebra were increased as the size of dog increased. However, the ratio of the spinal cord area to vertebral canal area in the small dogs was higher than that of the larger dogs. Results of the present study could provide basic and quantitative information for CT evaluation of pathologic lesions in the cervical vertebra and spinal cord.     

Origin and distribution of the brachial plexus of the Van cats

Knowing the structure and variations of the plexus brachialis is important in neck and shoulder surgery. The knowledge of the brachial plexus reduces the injury rate of the nerves in surgical interventions to the axillary region. The major nerve trunks of the thoracic limb were the suprascapular, subscapular, axillary, radial, musculocutaneous, median and ulnar nerves. In Van cats, the brachial plexus was formed by the ventral branches of the spinal nerves, C6-C7-C8 and T1. The 7th cervical nerve was quite thick compared to the others. The subscapular nerve was the thinnest (on the right side, the average length was 6.55 ± 0.60 mm and on the left side was 6.50 ± 0.60 mm), and the radial nerve was the thickest (the average length on the right side was 28.48 ± 0.44 mm and on the left side was 29.11 ± 0.55 mm). The suprascapular nerve was formed by the ventral branch of the 6th cervical nerve. The subscapular nerves were formed by a branch originating from the 6th cervical nerve and the two medial and caudal branches originating from the 7th cervical nerve. No communicating branch between the ulnar nerve and the median nerve was observed in the palmar region. The axillary nerve was formed by the ventral branches of the 7th nerve, the musculocutaneous nerve was formed by ventral branches of the 6th and 7th cervical nerves, and the ulnar nerve was formed by ventral branches of the 8th cervical and the 1st thoracic nerves. The radial nerve was the thickest branch in the brachial plexus. In Van cats, the origin and distribution of nerves were similar to those reported in the literature for other species of cats, with the exception of the suprascapular, subscapular and axillary nerves.     

Dynamic computed tomography evaluation of the nasopharynx in normal Beagle dogs

Pharyngeal collapsibility has been used as diagnostic criteria in dogs, whereas the normal range and quantitative method have not been studied. Dynamic and static computed tomography (CT) was performed in 23 normal Beagle dogs to quantify the nasopharyngeal collapsibility at different locations. Using dynamic CT, maximum and minimum nasopharyngeal cross-sectional areas (CSAs) were measured at the level of the cranial end of the soft palate, pterygoid hamulus, foramen lacerum, bony labyrinth, and caudal end of the soft palate. The ratio of all maximum and minimum CSA to nasopharyngeal CSA at the level of the caudal hard palate (rCSAmax and rCSAmin) and the nasopharyngeal collapsibility were calculated. The differences of rCSAmax, rCSAmin, and nasopharyngeal collapsibility were analyzed at various locations. The nasopharyngeal collapsibility at the level of foramen lacerum, bony labyrinth, and caudal end of soft palate were higher than the others. At the level of the caudal end of the soft palate, rCSAmin was lower than that of the foramen lacerum and bony labyrinth, whereas rCSAmax at foramen lacerum was higher than that of the caudal end of the soft palate. These results indicated that the nasopharynx at the level of foramen lacerum and caudal end of the soft palate were considered notable locations for evaluating collapsibility. Dynamic CT could show the nasopharyngeal dynamic profile and will be an adequate modality for evaluating nasopharynx. Our results will be helpful for further comparative studies in dogs with and without nasopharyngeal collapse.     

Feasibility of computed tomography in awake dogs with traumatic pelvic fracture

In veterinary medicine, general anesthesia or sedation is generally required to immobilize patients during computed tomography (CT) scanning. This may not be suitable in all patients because of risks of anesthesia. We evaluated the feasibility of pelvic CT examination in 14 awake animals with pelvic trauma. Physical restraint was applied by wrapping the patient in a towel and then taping to the CT table or by directly taping the patient to the CT table. The effect of patient positioning, cooperation on the CT table, preparation time for scanning, scanning time, frequency of repeat scans, image quality, and complications related to physical restraint were evaluated. Fractures were recorded and compared between radiography and CT. Ten of 14 dogs were scanned in lateral recumbency and four in sternal recumbency. All patients were cooperative with the exception of one that moved slightly during the scan. Both physical restraint methods were adequate for CT scanning. Patient preparation took less than 5 min while the scan time was typically less than 1 min. No repeat scans were required in any patient. The transverse CT image quality was good (10/14) or fair (4/14) for interpretation. When comparing the CT images to radiographs, more pelvic fractures were identified with CT than with radiography and a few patients were overdiagnosed based on radiographs. No complications or additional injuries associated with physical restraint were noticed.     

Computed tomographic bronchioarterial ratio for brachycephalic dogs without pulmonary disease

The bronchoarterial (BA) ratio measured with computed tomography is widely used in human medicine to diagnose bronchial dilation or collapse. Although use of the BA ratio in veterinary medicine has been recently studied, this has not been evaluated in brachycephalic dogs predisposed to bronchial diseases including bronchial collapse. The purpose of this study was to establish BA ratios for brachycephalic dogs and compare the values with those of non-brachycephalic dogs. Twenty-three brachycephalic dogs and 15 non-brachycephalic dogs without clinical pulmonary disease were evaluated. The BA ratio of the lobar bronchi in the left and right cranial as well as the right middle, left, and right caudal lung lobes was measured. No significant difference in mean BA ratio was observed between lung lobes or the individual animals (p = 0.148). The mean BA ratio was 1.08 ± 0.10 (99% CI = 0.98~1.18) for brachycephalic dogs and 1.51 ± 0.05 (99% CI = 1.46~1.56) for the non-brachycephalic group. There was a significant difference between the mean BA ratios of the brachycephalic and non-brachycephalic groups (p = 0.00). Defining the normal limit of the BA ratio for brachycephalic breeds may be helpful for diagnosing bronchial disease in brachycephalic dogs.     

Assessment of brachial plexus blockade in chickens by an axillary approach

ObjectiveTo assess the brachial plexus block in chickens by an axillary approach and using a peripheral nerve stimulator.Study designProspective, randomized, double-blinded study.AnimalsSix, 84-week old, female chickens.MethodsMidazolam (1 mg kg⁻¹) and butorphanol (1 mg kg⁻¹) were administered into the pectoralis muscle. Fifteen minutes later, the birds were positioned in lateral recumbency and following palpation of the anatomic landmarks, a catheter was inserted using an axillary approach to the brachial plexus. Lidocaine or bupivacaine (1 mL kg⁻¹) was injected after plexus localization by the nerve stimulator. Sensory function was tested before and after blockade (carpus, radius/ulna, humerus and pectoralis muscle) in the blocked and unblocked wings. The latency to onset of motor and sensory block and the duration of sensory block were recorded. A Friedman nonparametric one-way repeated-measures anova was used to compare scores from baseline values over time and to compare the differences between wings at each time point.ResultsA total of 18 blocks were performed with a success rate of 66.6% (12/18). The latency for motor block was 2.8 ± 1.1 and 3.2 ± 0.4 minutes for lidocaine and bupivacaine, respectively. The latencies for and durations of the sensory block were 6.0 ± 2.5 and 64.0 ± 18.0 and 7.8 ± 5.8 and 91.6 ± 61.7 minutes for lidocaine and bupivacaine, respectively. There was no statistical difference between these times for lidocaine or bupivacaine. Sensory function was not abolished in nonblocked wings.Conclusions and clinical relevanceThe brachial plexus block was an easy technique to perform but had a high failure rate. It might be useful for providing anesthesia or postoperative analgesia of the wing in chickens and exotic avian species that have similar wing anatomy.     

Clinical evaluation of the anaesthetic sparing effect of brachial plexus block in cats

ObjectiveTo evaluate the isoflurane sparing effect and the post-surgical analgesia provided by a brachial plexus block (BPB) in cats undergoing distal thoracic limb surgery.Study designProspective randomized blinded clinical study.AnimalsTwenty client-owned cats.MethodsCats were assigned to receive either no BPB (group NB) or a nerve stimulator guided BPB (group BPB) using lidocaine (3.6 mg kg^?1) and bupivacaine (1.2 mg kg^?1). Pre-medication consisted of midazolam and ketamine intravenously (IV). Anaesthesia was induced with propofol IV to effect and maintained with isoflurane delivered in oxygen and a continuous rate infusion of fentanyl (2 μg kg^?1 hour^?1). End-tidal isoflurane concentration (Fe′ISO) was adjusted every 3 minutes guided by changes in cardiorespiratory parameters and reflexes present, to maintain a stable depth of anaesthesia. Five time points were chosen to record all parameters and compare values between groups. Recovery and post-operative pain assessment were performed using a visual analogue scale (VAS) at 15 and 45 minutes after extubation and thereafter at hourly intervals until 5 hours after placement of the BPB.ResultsNo clinically significant differences were seen for heart rate, respiratory rate and non-invasive blood pressure between groups. Mean Fe′ISO was significantly lower in group BPB compared with group NB at all time points. In group NB, all intraoperative measurements of Fe′ISO were significantly higher compared with baseline (3 minutes before start of surgery) measurements. During recovery, VAS scores for group BPB were significantly lower than for group NB. Additional analgesics were needed in all cats within the study period.Conclusion and Clinical relevanceIn cats undergoing orthopaedic surgery of the thoracic limb, BPB reduced intra-operative isoflurane requirement and pain during the early post-operative period when compared with procedures without a BPB. BPB is a useful adjunct to anaesthesia in such cases.     

Assessment of glomerular filtration rate with dynamic computed tomography in normal Beagle dogs

The objective of our study was to determine individual and global glomerular filtration rates (GFRs) using dynamic renal computed tomography (CT) in Beagle dogs. Twenty-four healthy Beagle dogs were included in the experiment. Anesthesia was induced in all dogs by using propofol and isoflurane prior to CT examination. A single slice of the kidney was sequentially scanned after a bolus intravenous injection of contrast material (iohexol, 1 mL/kg, 300 mgI/mL). Time attenuation curves were created and contrast clearance per unit volume was calculated using a Patlak plot analysis. The CT-GFR was then determined based on the conversion of contrast clearance per unit volume to contrast clearance per body weight. At the renal hilum, CT-GFR values per unit renal volume (mL/min/mL) of the right and left kidneys were 0.69 ± 0.04 and 0.57 ± 0.05, respectively. No significant differences were found between the weight-adjusted CT-GFRs in either kidney at the same renal hilum (p = 0.747). The average global GFR was 4.21 ± 0.25 mL/min/kg and the whole kidney GFR was 33.43 ± 9.20 mL/min. CT-GFR techniques could be a practical way to separately measure GFR in each kidney for clinical and research purposes.     

Computed tomography diagnosis of eight dogs with brain infarction

Objective Medical records of eight dogs presenting with acute onset of neurological signs and a diagnosis of brain infarction as determined by computed tomography (CT) imaging were reviewed. Design Retrospective single-centre case review Results Ischaemic infarction in the territory of the rostral cerebellar artery was identified in three spaniel-breed dogs. All cerebellar infarcts were non-haemorrhagic. Telencephalic infarcts were identified in five dogs, in the territories of the middle cerebral artery (2/5) and rostral cerebral artery (3/5). One of these dogs had an ischaemic infarction, but all other infarctions appeared haemorrhagic. All dogs were geriatric (≥8 years old), with concurrent medical conditions identified in six dogs. One dog was euthanased after diagnosis because of the severity of its neurological signs and one dog was euthanased as a result of associated renal disease 2 months after diagnosis. Six dogs were alive at least 1 year after diagnosis. Conclusions CT is useful in the diagnosis of cerebrovascular accident in dogs, which can present as a spectrum of images with early changes in attenuation and subtle mass effects detected after infarction. CT is particularly sensitive for detecting haemorrhagic infarction, but under-represent ischaemic and lacunar infarctions when compared with MRI.