Ultrasound‐guided ‘two‐in‐one’ femoral and obturator nerve block in the dog: an anatomical study

ObjectiveTo evaluate the dye extent and distribution at the lumbar plexus (LP) of three volumes of local anaesthetic-methylene-blue solution administered close to the femoral nerve (FN) by the use of a ventral ultrasound (US)-guided suprainguinal approach (SIA).Study designProspective experimental trial.AnimalsTwenty mongrel canine cadavers weighing 17.7 ± 3.8 kg (mean ± SD).MethodsThe left and right LP of two cadavers were dissected to identify the FN, obturator nerve (ON) and lateral femoral cutaneous nerve (LFCN). The extent and distribution of dye at the LP of each of three volumes of injectate of 0.2, 0.4 and 0.6 mL kg^?1 administered close to the FN by a ventral US-guided SIA then were studied in a further 18 dog cadavers (n = 6 per group). Staining of ≥2 cm along the target nerves was indicative of sufficient spread to produce a nerve block.ResultsThe ventral US-guided SIA allowed the observation of the FN within the iliopsoas muscle (IPM) in a total of 17 cadavers. The assessment of the dye extent and distribution revealed a similar pattern regardless of the injected volume. From the injection site, the spreading of injectate occurred in cranial, lateral and caudal directions. The FN and ON were effectively stained in all the cases. The LFCN was not effectively stained in any case.Conclusions and clinical relevanceA volume of 0.2 mL kg^?1 administered close to the FN by a ventral US-guided SIA produced a sufficient distribution of the injectate within the IPM to produce effective staining of the FN and ON. This US-guided technique may be an appropriate alternative to previously reported techniques based on electrolocation to block the FN and ON in the dog.     

Development of a lateral ultrasound-guided approach for the proximal radial,ulnar, median and musculocutaneous (RUMM) nerve block in cats

ObjectiveTo describe a lateral ultrasound (US)-guided approach to the radial, ulnar, median and musculocutaneous (RUMM) nerves through a single proximal in-plane insertion in cats and to determine whether one or two injection points are required to successfully stain all the target nerves.Study designProspective study.AnimalsA total of eight client-owned healthy cats and 12 cat cadavers.MethodsIn live cats, the US anatomy of the brachium, the landmarks and the site for needle accesses were determined. Then, 12 thawed feline cadavers were used to assess the spread of dye solution and nerve staining following the US-guided proximal-lateral-humeral RUMM injection using one and two injection points. Each cadaver was injected with 0.15 mL kg^–1 of a 0.25% new methylene blue solution in either a single injection aimed for the radial nerve of one limb (G1) or via two sites delivering 0.1 mL kg^–1 and 0.05 mL kg^–1 aimed for the radial and musculocutaneous nerves of the opposite limb, respectively (G2). Upon dissection, staining of the target nerves around their circumference for length of >1 cm was considered successful.ResultsSonoanatomy was consistent with anatomy upon dissection and target nerves were identified in all cadavers. Staining was 100% successful for the radial, median and ulnar nerves in both groups, and 41.7% and 100% for the musculocutaneous nerve in G1 and G2, respectively.Conclusions and clinical relevanceThis novel lateral US-guided approach for the proximal RUMM nerve block allowed a good identification of the nerves and related structures, and it provided a consistent muscular structure through which the needle could be easily guided. An injection performed in two aliquots (within the caudal and cranial compartments of the neurovascular sheath) appeared to be necessary to successfully stain all the target nerves.     

Development of an ultrasound-guided transgluteal injection of the pudendal nerve in cats: a cadaveric study

ObjectiveTo develop an ultrasound-guided interfascial plane technique for injection of the pudendal nerve near its sacral origin in cats.Study designProspective, randomized, anatomical study.AnimalsA group of 12 feline cadavers.MethodsGross and ultrasound anatomy of the ischiorectal fossa, the pudendal nerve relationship with parasacral structures, and the interfascial plane were described. Computed tomography was employed to describe a cranial transgluteal approach to the pudendal nerve. Bilateral ultrasound-guided injections were performed in eight cadavers using low [(LV) 0.1 mL kg^–1] or high volume [(HV) 0.2 mL kg^–1] of ropivacaine–dye solution. Dissections were performed to determine successful staining of the pudendal nerve (>1 cm) and inadvertent staining of the sciatic nerve, and any rectal, urethral, or intravascular puncture. Pudendal nerve staining in groups LV and HV were compared using Fisher's exact and Wilcoxon rank-sum test as appropriate (p = 0.05).ResultsThe pudendal nerve and its rectal perineal and sensory branches coursed through the ischiorectal fossa, dorsomedial to the ischiatic spine. The pudendal nerve was not identified ultrasonographically, but the target plane was identified between the sacral transverse process, the ischiatic spine, the pelvic fascia and the rectum, and it was filled with dye solution. Both branches of the pudendal nerve were completely stained 75% and 87.5% in groups LV and HV, respectively (p = 1.00). The dorsal aspect of the sciatic nerve was partially stained in 37% of injections in group HV. Rectal or urethral puncture and intravascular injection were not observed.Conclusions and clinical relevanceIn cats, ultrasound-guided cranial transgluteal injection successfully stained the pudendal nerve in at least 75% of attempts, regardless of injectate volume. Group HV had a greater probability of sciatic nerve staining.     

Description of an ultrasound-guided rectus sheath block injection technique and the spread of dye in calf cadavers

ObjectivesTo describe an ultrasound-guided rectus sheath (RS) block technique in calves with injections of methylene blue and assess the extent of injectate spread and nerve staining in calf cadavers.Study designProspective, experimental, blinded cadaveric study.AnimalsA total of 16 calf cadavers weighing 30.7 ± 7.1 kg.MethodsUsing an ultrasound-guided, in-plane technique, each cadaver was injected with both a low (LV; 0.25 mL kg^–1) and high (HV; 0.5 mL kg^–1) volume of methylene blue dye. Volumes were randomly assigned to the left or right hemiabdomen. Ultrasound imaging was scored based on landmarks and needle visualization, and duration to perform injections were assessed. Dissections were performed immediately after injections. Staining of ventral branches of spinal nerves and the extent of dye spread were recorded by an anatomist unaware of treatment allocation.ResultsThe number of nerves stained in treatments LV and HV were 2.3 ± 1.7 and 4.4 ± 1.3, respectively (p = 0.0001). Branches of thoracic nerves T7–13 and lumbar nerves L1–2 were completely stained 6.3%, 6.3%, 31.3%, 62.5%, 56.3%, 37.5%, 31.3%, 6.3% and 0%, respectively, in treatment LV and 0%, 12.5%, 50%, 93.8%, 100%, 93.8%, 62.5%, 25% and 6.3%, respectively, in treatment HV. Ultrasound imaging was scored excellent in most cadavers and needle visualization deemed excellent in all injections. The mean duration to perform RS injections in both treatments was 2 (range, 1–6) minutes.Conclusions and clinical relevanceNerve staining results from treatment HV suggest that this RS injection technique could be clinically useful in ventral midline surgical procedures, including umbilical procedures, in calves. This study supports future clinical trials in calves.     

Pericapsular hip desensitization in dogs: a cadaveric study and case series

ObjectiveTo develop and assess the efficacy of an ultrasound (US)-guided pericapsular hip desensitization (PHD) technique in dogs.Study designProspective, randomized, anatomical study and a case series.AnimalsA total of 30 healthy dogs, eight canine cadavers and seven dogs with hip osteoarthritis.MethodsAfter studying the US anatomy of the medial aspect of the coxofemoral joint and determining an acoustic window to perform an US-guided PHD in healthy dogs, the US-guided PHD was performed bilaterally in canine cadavers. A low [(LV) 0.1 mL kg^–1] and high [(HV) 0.2 mL kg^–1] volume of dye was injected per hip on each cadaver. The staining of the pericapsular nerves was assessed by anatomical dissection, and comparison between LV and HV was assessed using Fisher’s exact test. Then, the US-guided PHD was performed using a triamcinolone–bupivacaine solution in dogs with hip osteoarthritis. Dynamic pain response was assessed before and after injection. The canine brief pain inventory (CBPI) questionnaire was used to assess treatment efficacy and duration.ResultsThe US-guided PHD could be performed by inserting the needle between the iliopsoas muscle and the periosteum of the ilium. The articular branches of the femoral and obturator nerves were stained in all cadavers using both volumes. The main femoral nerve was never stained, but the main obturator nerve was stained in 37.5% and 100% of injections using LV and HV, respectively (p = 0.026). Treated animals showed decreased dynamic pain response after the injection. Compared with baseline, CBPI scores were reduced by ≥ 50% for ≥ 12 weeks in all but one dog.Conclusions and clinical significanceThe US-guided PHD with both 0.1 and 0.2 mL kg^–1 volumes stained the articular branches of the femoral and obturator nerves in canine cadavers and was associated with clinical improvement in dogs with hip osteoarthritis.     

Comparison of three ultrasound guided approaches to the lumbar plexus in dogs: a cadaveric study

ObjectiveTo assess the accuracy of contrast material injection and the dispersion of injectate following ultrasound guided injections at the level of L6 and L7, in canine cadavers.Study designProspective, randomized, experimental study.AnimalsTwenty nine mixed breed canine cadavers (28.9 ± 6.0 kg).MethodsThree ultrasound-guided approaches to the lumbar plexus (LP) were compared: 1) a dorsal pre-iliac approach at the level of L6; 2) a lateral paravertebral approach at mid-L6; and 3) a lateral paravertebral approach at mid-L7. An isovolumic mixture of iodine-based contrast with new methylene blue (0.1 mL kg⁻¹) was injected bilaterally in the juxta-foraminal region along the L6 or L7 nerve root. Computed tomography was performed followed by segmentation and 3D reconstruction of the lumbar spine and contrast material volumes using dedicated software. Distances between contrast material and the fifth through seventh lumbar foraminae, and length of femoral (FN) and obturator (ON) nerve staining were measured and compared between approaches (p < 0.05).ResultsInjectate moved cranial and caudal to the site of injection, and dispersed into an ovoid shape between the quadratus lumborum, iliopsoas and psoas minor muscles. Injections at L7 resulted in significantly closer contrast proximity to the L6 and L7 foraminae (p < 0.001). Femoral nerve staining was similar for all approaches, ON staining was more consistent after L7 injections (p < 0.001).Conclusion and clinical relevanceAn ultrasound-guided lateral paravertebral approach to the LP proved very practical and accurate, with easy visualization of the plexus and associated nerves. To ensure that the ON is covered by injectate, an approach at the level of L7 is recommended. Further studies are necessary to determine if this correlates with clinically effective local anesthesia.     

Ultrasound-guided retrobulbar nerve block in donkey cadavers

ObjectiveTo develop and describe an acoustic window to access and inject the retrobulbar region in donkey cadavers.Study designProspective cadaveric experimental study.AnimalsA total of 14 donkey cadaver heads.MethodsUltrasound landmarks for retrobulbar injection were identified by dissection of two cadavers. Ultrasound-guided retrobulbar injection of 3, 6 and 9 mL of contrast–lidocaine mixture (1:1) were evaluated using computed tomography (CT) in 12 cadavers for needle position and spread of injectate into the extraocular muscle cone.ResultsReal-time visualization of needle, extraocular muscle cone and optic nerve enabled successful intraconal instillation of injectate, as documented on CT images.Conclusions and clinical relevanceUltrasound-guided retrobulbar injections in cadaver donkeys provided adequate infiltration of the intraconal space.     

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.     

Femoral nerve block: a novel psoas compartment lateral pre‐iliac approach in dogs

ObjectiveTo describe a new approach to block the femoral nerve and to evaluate the distribution of a dye injected into the psoas compartment using a new femoral nerve block approach; to assess its clinical application, when combined with a sciatic nerve block, for surgical anaesthesia/analgesia of the pelvic limb in dogs.Study designProspective anatomical, research and clinical study.AnimalsTwo dog cadavers; two dogs that had to be euthanized for reasons unrelated to this study, and 15 dogs undergoing pelvic limb orthopaedic surgery.MethodsPhase 1: anatomical dissections were performed to determine a simple method to approach the femoral nerve within the psoas compartment. Phase 2: 0.1 mL kg^?1 of a lidocaine-new methylene blue solution was injected bilaterally after successful electrolocation of the femoral nerve in two anaesthetized dogs. Colorant spread was evaluated through femoral nerve dissections after euthanasia. Phase 3: in 15 dogs undergoing pelvic limb orthopaedic surgery under light general anaesthesia with isoflurane, intra-operative analgesic effect (cardiovascular responses) and early post-operative pain score, of the novel femoral nerve block combined with a sciatic nerve block as the sole analgesic protocol, were evaluated.ResultsPhase 1: a needle inserted from the lateral aspect of the lumbar muscles, cranially to the iliac crest and with a 30–45° caudo-medial direction, reaches the femoral nerve in the caudal portion of the psoas compartment. Phase 2: Four femoral nerves were stained >2 cm. Phase 3: this novel lateral pre-iliac approach, combined with the sciatic nerve block, blunted the intra-operative cardiovascular response to surgical stimulation in 13 out of 15 anaesthetized dogs. In addition, rescue analgesia was not required in the early post-operative 2-hour period.Conclusion and clinical relevanceThe lateral pre-iliac femoral nerve block technique may provide adequate intra- and early post-operative pain relief in dogs undergoing pelvic limb surgery.     

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).     

ULTRASONOGRAPHIC ASSESSMENT OF THE CANINE SCIATIC NERVE

To describe the ultrasonographic technique for investigation of the canine sciatic nerve, four canine cadaver pelvic limbs, two live healthy dogs, and five canine patients with suspected peripheral sciatic nerve lesions were examined with a high-resolution linear ultrasound transducer. The caudal part of the lumbosacral trunk and the origin of the sciatic nerve were visualized through the greater ischiatic foramen. The two components of the sciatic nerve, common peroneal and tibial nerves, were distinguished along the entire length of the nerve, until they branched at the level of the distal femur. In healthy live dogs they appeared as two adjacent hypoechoic tubular structures with internal echotexture of discontinuous hyperechoic bands, surrounded by a thin rim of highly echogenic tissue. The common peroneal component had a smaller diameter and was on the cranial aspect of the tibial component. An ultrasonographic lesion compatible with a peripheral nerve sheath tumor was found in one dog. Improved understanding of the ultrasonographic anatomy of the sciatic nerve supports clinical use of this modality.     

Comparison of dorsoventral and ventrodorsal approaches for ultrasound-guided quadratus lumborum block in cats: a cadaver study

ObjectiveTo assess the feasibility of an ultrasound (US)-guided quadratus lumborum (QL)-psoas muscle (Pm) interfascial plane injection using a dorsoventral (DV) approach, and to compare needle visualization and distribution pattern between DV and ventrodorsal (VD) approaches.Study designExperimental anatomical study.AnimalsA total of 14 cat cadavers.MethodsBilateral in-plane US-guided injections in the QL-Pm plane were performed at the level of the second lumbar (L2) transverse process. A spinal needle was inserted using either a VD or DV approach. A total volume of 0.4 mL kg^–1 of a solution of ropivacaine 0.18%, tissue dye and iohexol (350 mg mL^–1), in a proportion of 3:1:1, respectively, was injected bilaterally. Spread of injectate was compared and evaluated using US, computed tomography (CT) scanning and anatomical dissection. Presence of dye on the sympathetic trunk was compared between methods using Kappa (κ) coefficient of agreement.ResultsThe QL-Pm plane was visualized, and dye was present in the target plane using both approaches. Needle visualization in the VD approach was enhanced compared with the DV approach (p = 0.0005). Mean distribution along the sympathetic trunk was 4.8 and 4.1 segments in the VD and DV approaches, respectively, showing non-statistical differences. The ventral branches of L1, L2 and L3 were successfully stained in 11/14 and 6/14 using the VD and DV approaches, respectively. Substantial agreement (κ = 0.61) of sympathetic trunk staining was observed between CT scan and anatomical dissection. Dye was observed cranial to the diaphragm in 7/8 cases on CT with both approaches. Epidural and abdominal cavity dye distribution was not observed.Conclusions and clinical relevanceThe DV approach to the QL-Pm plane could be an alternative to the VD approach. Both approaches seem capable of reaching the spinal nerves, the sympathetic trunk and both splanchnic and coeliac nerves in feline cadavers.     

A cadaver study comparing two approaches for performing maxillary nerve block in dogs

Objective To compare the success by inexperienced anaesthetists of using a modified infraorbital approach to the maxillary nerve with the traditional percutaneous approach. Study design Prospective, randomized, blinded controlled study. Animals Heads from 37 euthanized Beagle and Beagle cross dogs. Methods Four anaesthetists were recruited to perform two different approaches to block the maxillary nerve of the cadavers. The infraorbital (I) approach advanced an intravenous catheter along the infraorbital canal. Earlier measurements from scans of similar heads were used to assess suitable catheter size. The percutaneous (P) approach introduced a needle percutaneously just below the ventral border of the zygomatic arch. The side of the head where the technique was to be performed was randomized. A total volume of 0.5 mL methylene blue was injected in each approach. After completion of injections, head dissections were performed by an investigator unaware of the approach used and staining of the maxillary and pterygopalatine nerves was evaluated. Chi squared analysis examined the relationship between the methods (p < 0.05). Complications related to the techniques, such as intravascular/intraneural injection and location of the dye, were evaluated macroscopically. Results Maxillary nerve staining >6 mm was found in 64.9% (I) versus 21.6% (P) attempts; staining <6 mm was found in 27% (I) versus 21.6% (P); and no nerve staining 8.1% (I) versus 56.8% (M). Pterygopalatine nerve staining was found in 70% (I) versus 21% (P). The infraorbital approach demonstrated significantly higher maxillary and pterygopalatine nerve staining compared to the percutaneous approach (p = 0.001 for both nerves). No evidence of intravascular/intraneural injections was found. Conclusion and clinical relevance The infraorbital approach was more successful than the percutaneous approach when performed by inexperienced anaesthetists. No macroscopic complications were observed.     

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.     

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.     

A non-inferiority study comparing the ultrasound-guided parasacral with a novel greater ischiatic notch plane approach in canine cadavers

ObjectiveTo describe the gross and ultrasound anatomy of the parasacral region and an ultrasound-guided greater ischiatic notch (GIN) plane approach aimed at staining the lumbosacral trunk (LST) in canine cadavers. To evaluate if the ultrasound-guided GIN plane approach is non-inferior to the previously described ultrasound-guided parasacral approach at staining the LST.Study designProspective, randomized, non-inferiority experimental anatomic study.AnimalsA total of 17 (23.9 ± 5.2 kg) mesocephalic canine cadavers.MethodsAnatomic and echographic landmarks, and the feasibility of performing a GIN plane technique were evaluated using two canine cadavers. The remaining 15 cadavers had each hemipelvis randomly assigned to be administered either parasacral or GIN plane injection of 0.15 mL kg^–1 dye solution. The parasacral region was dissected after injections to assess the staining of LST, cranial gluteal nerve, pararectal fossa and pelvic cavity. The stained LST were removed and processed for histological evaluation of intraneural injections. A one-sided z-test for non-inferiority (non-inferiority margin –14%) was used to statistically evaluate the success of the GIN plane versus the parasacral approach. Data were considered statistically significant when p < 0.05.ResultsThe GIN plane and parasacral approach stained the LST in 100% and 93.3% of the injections, respectively. The success rate difference between treatments was 6.7% [95% confidence interval, –0.6 to 19.0%; p < 0.001 for non-inferiority]. The GIN plane and parasacral injections stained the LST for 32.7 ± 16.8 mm and 43.1 ± 24.3 mm, respectively (p = 0.18). No evidence of intraneural injection was found.Conclusions and clinical relevanceThe ultrasound-guided GIN plane technique resulted in nerve staining that was non-inferior to the parasacral technique and may be considered an alternative to the parasacral approach to block the LST in dogs.