Ultrasound-guided erector spinae plane block in canine cadavers: relevant anatomy and injectate distribution

ObjectiveTo investigate the distribution and nerve staining of two volumes of lidocaine–dye solution after ultrasound-guided erector spinae plane (ESP) injections in canine cadavers.Study designExperimental cadaveric study.AnimalsA total of nine canine cadavers.MethodsESP injections were performed between the longissimus thoracis muscle and the dorsolateral edge of the ninth thoracic transverse process. Two cadavers were transversally cryosectioned after unilateral ESP injections [0.6 mL kg^–1; high volume (HV)]. In seven cadavers, bilateral ESP injections with HV or low volume (0.3 mL kg^–1; LV) were performed. Gadodiamide was added to the injectate for two cadavers and magnetic resonance imaging (MRI) was performed pre- and post-injection. Injectate distribution and nerve staining of the branches of the spinal nerves were recorded after gross anatomical dissection. The thoracic paravertebral and epidural spaces were examined for dye solution.ResultsCryosections, MRI and gross dissections showed that the injectate spread dorsally to the transverse processes, over the ventromedial aspect of the longissimus thoracis muscle where the medial and lateral branches of the dorsal branches of the spinal nerves are located. LV and HV stained a median (range) of 4 (2–7) and 4 (3–8) medial branches, respectively (p = 0.52). LV and HV stained 4 (2–5) and 5 (4–7) lateral branches (p = 0.26), respectively. Ventral branches were not stained, and dye was not identified in the epidural or paravertebral spaces.Conclusionsand clinical relevance Medial and lateral branches were consistently stained over several spinal segments. The number of nerves stained was not different with HV or LV, and the ventral branches of the spinal nerves were not stained in any cadaver. ESP block may find a clinical application to desensitize structures innervated by the medial and lateral branches of the dorsal branches of the thoracic spinal nerves.     

Lumbar erector spinae plane block: an anatomical and dye distribution evaluation of two ultrasound-guided approaches in canine cadavers

ObjectiveTo examine the anatomy of the lumbar epaxial region and to describe two different ultrasound-guided approaches for the lumbar erector spinae plane (ESP) block in dogs.Study designAn anatomical and experimental cadaver study.AnimalsA group of 19 canine cadavers.MethodsThe anatomy was described following dissection of two cadavers. Bilateral ultrasound-guided ESP injections with 0.4 mL kg^–1 of contrast dye were performed in 17 adult Beagle cadavers using either transversal (TVS) or parasagittal (PST) approaches. Computed tomography was performed to measure the total length of the contrast dye column and the epidural, intravascular, hypaxial and intra-abdominal migration. Dissections were performed to assess the spread of the contrast dye and to determine the degree of staining of the dorsal branches of the spinal nerves (DBSN). Mann–Whitney U and chi-square tests were used to compare data between groups.ResultsUsing both techniques, the contrast dye was observed within the ESP compartment. There was no difference in the total length of the contrast dye column between TVS and PST approaches (p = 0.056). Using the TVS approach, multisegmental staining of the DBSN was visible with 100% (17/17) of injections, while complete staining of the DBSN was achieved at 94% of the injection sites. Using the PST approach, these values were 29% (5/17) and 23% (4/17), respectively. The TVS approach stained more DBSN than the PST approach (p = 0.001), with a median (range) of 2 (2–3) versus 0 (0–3) DBSN, respectively. Using the TVS approach, epidural and intravascular migration were present in 2/17 (p = 0.485) and 3/17 (p = 0.227) injections, respectively.Conclusions and clinical relevanceBoth ultrasound-guided approaches resulted in a spread of the contrast dye within the ESP compartment. Although there were no differences in the total length of the contrast dye column, the TVS approach was superior to the PST approach in staining DBSN.     

Self‐inflicted lingual trauma secondary to inferior alveolar nerve block in 3 horses

Exodontia is the typical treatment recommended in severe cases of dental disease where alternative treatment techniques fail to salvage the affected tooth. Exodontias are frequently performed in the standing horse with the benefit of sedation and regional anaesthesia in order to avoid the risks and expense of general anaesthesia. The inferior alveolar nerve block is commonly utilised when extracting diseased mandibular dentition. Because of the close anatomical relationship of the lingual and inferior alveolar nerves both may be desensitised following anaesthesia of the inferior alveolar nerve. Desensitisation of the tongue may result in horses traumatising it during mastication before sensation returns. This report describes 3 horses that sustained self‐inflicted lingual trauma following inferior alveolar nerve blocks performed for standing oral surgical procedures.     

A cadaver study comparing two approaches to perform a maxillary nerve block in the horse

Reasons for performing study: Anaesthesia of the maxillary nerve of the horse has been described using several approaches, but sparse data exist to evaluate the accuracy of these methods. Objectives: This study compared 2 previously described approaches to the maxillary nerve to assess their relative accuracies. Methods: Thirty severed heads from horse cadavers were arranged to approximate the position of a live horse. Methylene blue (0.25 or 0.1 ml) was injected using a 19 gauge 90 mm spinal needle by one of 2 approaches, the method used being randomly allocated in each instance. Method ANG: angulated needle insertion on the ventral border of the zygomatic process of the temporal bone and directed rostromedially. Method PER: needle inserted perpendicular to the skin surface, ventral to the zygomatic process of the malar bone, level with the temporal canthus of the eye. Accuracy of dye deposition was assessed following dissection. Placement was categorised as ‘full hit’ (complete nerve coverage or dye deposition centred on nerve), ‘partial hit’ (partial nerve discolouration but dye not centred on nerve) or ‘miss’ (no nerve discolouration). Deposition of dye relative to the nerve and whether injection was performed on the left or right side of the head was recorded. A Chi‐squared test was performed to examine the relationship between the 2 methods. Results: Method ANG was performed 31 times, Method PER 28 times. Full hits were 10/31 (32%) vs. 9/28 (32%), partial hits 15/31 (49%) vs. 14/28 (50%) and misses 6/31 (19%) vs. 5/28 (18%) (Methods ANG vs. PER, respectively). Results were not statistically significantly different between the methods. Dye was deposited in the deep facial vein once by each method. Bone was contacted consistently with Method PER and 8/31 times with Method ANG. Conclusion and clinical relevance: Both methods appeared equivalent in terms of accuracy. Aspiration should always precede injection.     

Ultrasound‐guided retrobulbar nerve block in horses: a cadaveric study

Objective To develop an ultrasound‐guided technique for retrobulbar nerve block in horses, and to compare the distribution of three different volumes of injected contrast medium (CM) (4, 8 and 12 mL), with the hypothesis that successful placement of the needle within the retractor bulbi muscle cone would lead to the most effective dispersal of CM towards the nerves leaving the orbital fissure. Study design Prospective experimental cadaver study. Animals Twenty equine cadavers. Methods Ultrasound‐guided retrobulbar injections were performed in 40 cadaver orbits. Ultrasound visualization of needle placement within the retractor bulbi muscle cone and spread of injected CM towards the orbital fissure were scored. Needle position and destination of CM were then assessed using computerized tomography (CT), and comparisons performed between ultrasonographic visualization of orbital structures and success rate of injections (intraconal needle placement, CM reaching the orbital fissure). Results Higher scores for ultrasound visualization resulted in a higher success rate for intraconal CM injection, as documented on the CT images. Successful intraconal placement of the needle (22/34 orbits) resulted in CM always reaching the orbital fissure. CM also reached the orbital fissure in six orbits where needle placement was extraconal. With 4, 8 and 12 mL CM, the orbital fissure was reached in 16/34, 23/34 and 28/34 injections, respectively. Conclusion and clinical relevance The present study demonstrates the use of ultrasound for visualization of anatomical structures and needle placement during retrobulbar injections in equine orbits. However, this approach needs to be repeated in controlled clinical trials to assess practicability and effectiveness in clinical practice.     

Description of a novel ultrasound-guided approach for a dorsal quadratus lumborum block: a canine cadaver study

ObjectiveTo describe an ultrasound-guided approach to the dorsal aspect of the quadratus lumborum muscle (D-QL) and to evaluate the spread of methylene blue dye in canine cadavers.Study designProspective, experimental anatomical study.AnimalsA total of 12 canine cadavers.MethodsThe ultrasonographic landmarks and injection technique for the D-QL approach were determined in two cadavers. Correct needle tip position was confirmed by computed tomography. Bilateral ultrasound-guided injections were performed in 10 cadavers between the QL muscle, the vertebral body and the ventrocaudal aspect of the transverse process of the first lumbar vertebra (L1) using two volumes of methylene blue: low volume (LV) 0.3 mL kg^–1 or high volume (HV) 0.5 mL kg^–1. Staining of the main thoracolumbar trunk, dorsal and ventral branches of the thoracic (T) and lumbar (L) spinal nerves, sympathetic trunk and epidural space were assessed following dissection. Data between groups were compared using Mann–Whitney U test. Data are presented as median (range).ResultsThe ventral branches of spinal nerves T12, T13, L1, L2, L3 and L4 were stained in 10%, 70%, 100%, 90%, 60%, 0% and 30%, 100%, 100%, 100%, 50% and 30% after LV and HV injections, respectively. Multisegmental spread of the sympathetic trunk was found on 3 (3–4) and 5 (3–6) vertebral spinal levels following LV and HV injections, respectively (p = 0.005). The T13 segment of the sympathetic trunk was stained after all HV injections. Epidural spread was found in 20% and 30% of LV and HV injections, respectively.Conclusions and clinical relevanceThe injection of HV versus LV dye using the D-QL approach provided more consistent staining of the thoracolumbar nerve structures which innervate the abdominal wall and viscera. Clinical studies are required to evaluate the analgesic efficacy of the D-QL block for abdominal procedures in dogs in vivo.     

Ultrasound-guided rectus sheath block: an anatomic study in dog cadavers

ObjectivesTo describe the ultrasound-guided rectus sheath block technique and the anatomical spread of two volumes of methylene blue injection in dog cadavers.Study designBlinded, prospective, experimental cadaveric study.AnimalsA total of eight dog cadavers weighing 8.9 ± 1.6 kg.MethodsUltrasound-guided rectus sheath injections were performed bilaterally 1 cm cranial to the umbilicus using 0.25 mL kg^–1 (low volume; LV) and 0.50 mL kg^–1 (high volume; HV) of 0.5% methylene blue dye. A total of 16 hemiabdomens were injected. The ultrasound image quality of the muscular and fascial plane landmarks and needle visualization were scored using a standardized scale. Cadavers were dissected to determine the distribution of the dye and to assess staining of ventral branches of the spinal nerves.ResultsFewer ventral spinal nerve branches were stained in the LV group than in the HV group, at 2.00 ± 0 and 2.90 ± 0.83, respectively (p < 0.01). Ventral branches of thoracic (T) and lumbar (L) spinal nerves (T10, T11, T12, T13 and L1) were stained 25%, 100%, 75%, 25% and 0% of the time in LV group and 12.5%, 87.5%, 100.0%, 75.0% and 13.0% in HV group. A lesser extent of cranial–caudal dye distribution was observed in the LV group than in the HV group (7.1 ± 1.8 cm and 9.2 ± 1.8 cm, respectively; p = 0.03). There was no significant difference in medial–lateral spread of dye, number of test doses or ultrasound image quality scores between groups.Conclusions and clinical relevanceThe results of this study suggest that, on an anatomical basis, this easily performed block has the potential to provide effective abdominal wall analgesia for the ventral midline. This study supports the potential of the rectus sheath block for abdominal procedures, and further investigations on its clinical efficacy are warranted.     

Ultrasound-guided dorsal approach for the brachial plexus block in common kestrels (Falco tinnunculus): a cadaver study

ObjectiveTo develop an ultrasound-guided dorsal approach to the brachial plexus and to investigate the nerve distribution and staining of a dyed injectate in common kestrel (Falco tinnunculus) cadavers.Study designProspective, cadaver study.AnimalsA group of three common kestrel cadavers (six wings).MethodsAll cadavers were fresh-frozen at –20 °C and thawed for 10 hours at room temperature before the study. The cadavers were placed in sternal recumbency and their wings were abducted. A 8–13 MHz linear-array transducer was placed over the scapulohumeral joint, at the centre of a triangle formed by the scapula and the humerus. The brachial plexus was identified between the scapulohumeralis muscle and the pectoralis major muscle, as hypoechoic structures lying just cranially to the axillary vessels. After ultrasound-guided brachial plexus identification, a 22 gauge, 50 mm insulated needle was advanced in-plane using ultrasound visualization. A volume of 0.5 mL kg^–1 of a 3:1 (2% lidocaine:methylene blue) solution was injected. Following cadaver dissection, the pattern of the spread was assessed, and the extent of nerve staining was measured with a calliper and deemed adequate if more than 0.6 cm of the nerve staining was achieved.ResultsThe brachial plexus was clearly identified in all wings with the dorsal approach. After dye injection, all the branches of the brachial plexus defined as nerves 1–5 (N1, N2, N3, N4 and N5) were completely stained in five (83%) and partially stained in one (17%) of the six wings.Conclusions and clinical relevanceThe ultrasound-guided dorsal approach allows a clear visualization of the brachial plexus structure. The injection of 0.5 mL kg^–1of a lidocaine/dye solution produced complete nerve staining in most cases. Further in vivo studies are mandatory to confirm the clinical efficacy of this locoregional anaesthesia technique in common kestrels (Falco tinnunculus).     

Description of a novel ultrasound guided peribulbar block in horses: a cadaveric study

BackgroundStanding surgery in horses combining intravenous sedatives, analgesics and local anaesthesia is becoming more popular. Ultrasound guided (USG) peribulbar nerve block (PB) has been described in dogs and humans for facial and ocular surgery, reducing the risk of complications versus retrobulbar nerve block (RB).ObjectiveTo describe a technique for USG PB in horse cadavers.MethodsLandmarks and PB technique were described in two equine cadaver heads (Phase 1), with computed tomography (CT) imaging confirming contrast location and spread. In Phase 2, ten equine cadaver heads were randomised to two operators naïve to the USG PB, with moderate experience with ultrasonography and conventional “blind” RB. Both techniques were demonstrated once. Subsequently, operators performed five USG PB and five RB each, unassisted. Contrast location and spread were evaluated by CT. Injection site success was defined for USG PB as extraconal contrast, and for RB intraconal contrast.ResultsSuccess was 10/10 for USG PB and 0/10 for RB (p < 0.001). Of the RB injections, eight resulted in extraconal contrast and two in the masseter muscle (p = 0.47).ConclusionsThe USG PB had a high injection site success rate compared with the RB technique; however, we cannot comment on clinical effect. The USG technique was easily learnt, and no potential complications were seen. The USG PB nerve block could have a wide application for use in horses for ocular surgeries (enucleations, eyelid, corneal, cataract surgeries, and ocular analgesia) due to reduced risk of iatrogenic damage. Further clinical studies are needed.     

Comparison of lameness scores after a low 4-point nerve block to lameness scores after additional desensitisation of the dorsal metatarsal nerves in horses with experimentally induced pain in the metatarsophalangeal joint

This study evaluated whether anaesthesia of the dorsal metatarsal nerves in addition to a low 4-point nerve block provides significantly more analgesia to the metatarsophalangeal joint than to a low 4-point nerve block alone. A wireless, inertial, sensor-based, motion analysis system was used to evaluate gaits of six horses before induction of lameness, after administration of interleukin-1β into a metatarsophalangeal joint, after anaesthesia of the medial and lateral plantar nerves and the medial and lateral plantar metatarsal nerves, and after additional anaesthesia of the lateral and medial dorsal metatarsal nerves. The magnitude of hindlimb lameness was analysed considering both the push-off component (diffmaxpelvis) and the impact component (diffminpelvis) of the lame limb for all trials. There was no significant difference in the sum of diffmaxpelvis and diffminpelvis (SDMPs) when comparing the horse's gait after the low 4-point nerve block to the gait after additional anaesthesia of the dorsal metatarsal nerves, indicating that there is likely no benefit of medial and lateral dorsal metatarsal nerve anaesthesia when using regional anaesthesia to localise pain to the metatarsophalangeal joint during a lameness examination.     

Retrospective clinical evaluation of ultrasound guided transverse abdominis plane block in dogs undergoing mastectomy

HistoryEleven female dogs of different breeds undergoing unilateral radical (n = 7) or regional abdominal mastectomy (n = 4) received an ultrasound guided transverse abdominis plane block (TAP-block).Physical examinationSubjects showed single or multiple mammary tumours. Serum biochemistry, CBC and electrocardiogram were unremarkable. Eight animals were classified as ASA physical status II and 3 as ASA III.ManagementDogs were premedicated with methadone [0.1 or 0.2 mg kg^?1 intravenously (IV) or intramuscularly respectively] or fentanyl (2.5 μgkg^?1 IV). Anaesthesia was induced with propofol and maintained with isoflurane or sevoflurane. Unilateral ultrasound guided TAP blocks were performed in the caudal and cranial abdomen with bupivacaine 0.25% (0.3 to 0.35 mL kg^?1). Intercostal nerve blocks (T₄ to T₁₁) with bupivacaine 0.25% (0.013 to 0.04 mL kg^?1) completed the blocked area in dogs undergoing radical mastectomy.Follow upThe median (range) of end-expired isoflurane and sevoflurane necessary to maintain anaesthesia was 1.15 (1.07–1.22) and 2.07 (2.05–2.2) vol% respectively. A single administration of fentanyl (2.5 μg kg^?1, IV) was administered to control nociception (defined as an increased heart rate or mean arterial blood pressure above 20% of the pre-incisional value) in four of 11 dogs. All dogs received carprofen (2 mg kg^?1 subcutaneously) at the end of surgery. Post-operative pain, assessed for 120 minutes using the short form of Glasgow Composite Pain Scale (0–24), was always lower than 3. No rescue analgesia (allowed by the protocol) was required in this time.ConclusionTransverse abdominis plane block combined with intercostal nerve blocks may be useful to produce intraoperative anti-nociception and short term post-operative analgesia in dogs undergoing unilateral mastectomy.     

A transorbital approach to the maxillary nerve block in dogs: a cadaver study

Objective

To describe a transorbital approach to the maxillary nerve block in dogs and compare it with a traditional approach.

An ultrasound-guided subparaneural approach to the sciatic nerve in the dog: a cadaver study

ObjectiveTo describe the gross and microscopic anatomy of the sciatic nerve paraneural sheath and to report an ultrasound (US)-guided subparaneural approach to the sciatic nerve in dogs, comparing two different volumes of injectate.Study designProspective, randomized, anatomical study.AnimalsA group of nine middle-sized adult Mongrel canine cadavers (18 limbs).MethodsThe sciatic nerves of three pelvic limbs of two canine cadavers were identified, exposed and isolated between the greater trochanter and the popliteal fossa for gross anatomical and microscopic examination. An additional three pelvic limbs were surgically dissected on the lateral surface of the limb; the sciatic nerves were isolated, and a 26 gauge over-the-needle catheter was inserted through the paraneural sheath under direct visualization. A methylene blue solution was then slowly injected into the subparaneural compartment through the catheter under US visualization using an 8–13 MHz linear-array transducer. Subsequently, 12 pelvic limbs (six cadavers) were randomly allocated to one of two groups; using US-guided percutaneous subparaneural approach, either 0.1 or 0.05 mL kg^–1of a 1:1 solution of methylene blue and 0.5% bupivacaine was injected. The spread of the dye solution and the amount of nerve staining were macroscopically scored. The stained sciatic nerves with their sheaths were then harvested for microscopic examination.ResultsThe paraneural sciatic nerve sheath was easily identified distinct from the nerve trunk both macroscopically and with US visualization, and microscopically. Complete staining was achieved in five of six (83.3%) sciatic nerves in each group; no difference was found in the amount of staining between the two groups. Microscopically, no signs of sciatic nerve intraneural injection were observed.Conclusions and clinical relevanceThe US-guided subparaneural injection of 0.05 mL kg^–1 of a dye injectate resulted in satisfactory nerve staining without evidence of sciatic nerve intraneural injection.     

The effect of erector spinae plane block on perioperative analgesic consumption and complications in dogs undergoing hemilaminectomy surgery: a retrospective cohort study

ObjectiveTo compare the perioperative use of analgesics and complication rates in dogs administered an erector spinae plane (ESP) block or a traditional opioid-based (OP) treatment as part of analgesic management during hemilaminectomy.Study designRetrospective cohort study.AnimalsMedical records of 114 client-owned dogs.MethodsGeneral data included demographics, duration of procedure, number of laminae fenestrated, perioperative use of steroid and non-steroidal anti-inflammatory drugs. Intra- and postoperative analgesics used in 48 hours and complications rates were compared between groups. Opioid use was expressed in morphine equivalents [ME (mg kg^?1)]. Continuous data were compared using the Mann–Whitney U test and incidence of events with a Fisher's exact tests. Multiple linear regression was used to evaluate association between perioperative ME consumption (dependent variable) with other independent variables. Data are presented as median (range). Differences were considered significant when p < 0.05.ResultsGroup ESP comprised 42 dogs and group OP 72 dogs. No differences were observed in the general data. Intraoperative ME was 0.65 (0.20–3.74) and 0.79 (0.19–5.60) mg kg^?1 in groups ESP and OP, respectively (p = 0.03). Intraoperative infusion of lidocaine was administered intravenously (IV) to 23.8% and 68% of groups ESP and OP, respectively (p < 0.0001). Intraoperative infusion of ketamine was administered IV to 21% and 40% of groups ESP and OP, respectively (p = 0.04). Regression analysis revealed the ESP block as the only independent variable affecting the perioperative ME consumption. Pharmacological intervention to treat cardiovascular complications was administered to 21.4% and 47.2% of dogs in groups ESP and OP, respectively (p = 0.008). There were no differences in postoperative complication rates.Conclusions and clinical relevanceESP block was associated with reduced perioperative opioid consumption, intraoperative adjuvant analgesic use and incidence of pharmacological interventions to treat cardiovascular complications in dogs undergoing hemilaminectomy.     

Ultrasound-guided posterior extraconal block in the dog: anatomical study in cadavers

Objective

To describe a novel ultrasound-guided posterior extraconal block in the dog.

Peripheral nerve block versus systemic analgesia in dogs undergoing tibial plateau levelling osteotomy: Analgesic efficacy and pharmacoeconomics comparison

ObjectiveTo compare the perioperative effects and pharmacoeconomics of peripheral nerve blocks (PNBs) versus fentanyl target-controlled infusion (fTCI) in dogs undergoing tibial plateau levelling osteotomy (TPLO).Study designRandomized clinical study.AnimalsA total of 39 dogs undergoing unilateral TPLO.MethodsAfter acepromazine and methadone, anaesthesia was induced with propofol and maintained with isoflurane. Dogs were allocated to group fTCI [target plasma concentration (TPC) 1 ng mL^–1] or group PNB (nerve stimulator-guided femoral-sciatic block using 0.2 and 0.1 mL kg^–1 of levobupivacaine 0.5%, respectively). If nociceptive response occurred, isoflurane was increased by 0.1%, and TPC was increased by 0.5 ng mL^–1 in group fTCI; a fentanyl bolus (1 μg kg^–1) was administered in group PNB. During the first 24 postoperative hours, methadone (0.2 mg kg^–1) was administered intramuscularly according to the Short Form Glasgow Composite Pain Scale, or if pain was equal to 5/24 or 4/20 for two consecutive assessments, or if the dog was non-weight bearing. The area under the curve (AUC) of pain scores, cumulative postoperative methadone requirement, food intake and pharmacoeconomic implications were calculated.ResultsIncidence of bradycardia (p = 0.025), nociceptive response to surgery (p = 0.041) and AUC of pain scores (p < 0.0001) were greater in group fTCI. Postoperatively, 16/19 (84.2%) and eight/20 (40%) dogs in groups fTCI and PNB, respectively, were given at least one dose of methadone (p = 0.0079). Food intake was greater in group PNB (p = 0.049). Although total cost was not different (p = 0.083), PNB was more cost-effective in dogs weighing >15 kg.Conclusions and clinical relevanceCompared with group fTCI, incidence of bradycardia, nociceptive response to surgery, postoperative pain scores, cumulative methadone requirement were lower, and food intake was greater in group PNB, with an economic advantage in dogs weighing >15 kg.     

Ultrasound-guided thoracic paravertebral block: cadaveric study in foxes (Vulpes vulpes)

Objective

To describe an ultrasound-guided thoracic paravertebral block in canidae.