In-plane Technique Research Articles

Incidence of sub-perineural injection using a targeted intracluster supraclavicular ultrasound-guided approach in cadavers

BackgroundMulti-injection targeted intracluster injection ultrasound-guided supraclavicular brachial plexus block has been advocated to provide a faster onset of anaesthesia compared with a double injection technique. By placing the needle within clusters of hypoechoic structures, corresponding to neural tissue, this technique may increase needle trauma and the incidence of nerve injury. This study assessed the rate of sub-perineural needle placement with a single intracluster brachial plexus injection in the supraclavicular fossa of human cadavers. MethodsA single ultrasound-guided intracluster brachial plexus injection was performed bilaterally at the supraclavicular fossa on 21 lightly embalmed clinical grade cadavers. Using an in-plane technique, an echogenic needle was positioned to target the middle or lower trunk ‘cluster’, where 0.2 ml black India ink was injected. An effort was taken to avoid the hypoechoic structures with the needle tip. Tissue samples were assessed histologically by two experienced reviewers. ResultsAll 42 injections were sonographically assessed to be within the ‘main cluster’. Ink was extra-epineural in 13/41 (32%), sub-epineural but outside perineurium in 18/41 (44%), and sub-perineural in 10/41 sections (24%; 95% confidence interval, 13–41%). The histology from one injection was uninterpretable. Of the 10 sub-perineural deposits, the ink was intrafascicular in nine sections. ConclusionsWe observed a high rate of sub-perineural injection with a single intracluster injection. Thus the targeted intracluster injection supraclavicular block cannot be recommended until further evidence is available regarding the safety of this technique.

The effect of ultrasound guided superior cervical sympathetic ganglion block to abducens nerve palsy caused by microvascular ischemia-a case report

The abducens nerve palsy is most likely caused by microvascular issue. Spontaneous recovery of vasculopathic abducens nerve palsies was common at 3 to 6 months. But recovery time was longer when many risk factors were present. Several patients had residual esotropia or abduction deficit. Cervical sympathetic block has an established use in treating patients with disorders related to cranial circulatory insufficiency. It causes a significant increase in cerebral blood flow 1,2. We report a case of a 67-year-old man with acute horizontal diplopia and right periocular pain. He had been diagnosed with right abducens nerve palsy caused by microvascular ischemia. We performed ultrasound-guided superior cervical sympathetic ganglion blocks. The patient was placed in a supine position, and his head was turned approximately 45 degrees to the left side. A transducer was transversely oriented over the right side of his neck, and the transverse process of C6 was located to the cricoid cartilage level. The transducer was moved in the cephalad direction along the neck to locate the common carotid bifurcation. After identifying the oval-shaped and hypoechoic structure between the longus capitis muscle and the starting point to branch off the common carotid bifurcation, a 23-gauge needle was introduced slowly from a lateral approach with the in-plane technique using ultrasound guidance. The needle was inserted until it approached the target site, and it was positioned immediately adjacent to the structure appearing to be the SCSG. We performed the SCSG block with 5 cc of 0.2 % ropivacaine, and then we identified Horner's sign on the same side after the injection. He received blocks in the same manner once every three or four days due. After four weeks, the symptoms had been completely resolved. We introduce ultrasound-guided superior cervical sympathetic ganglion blocks for management of abducens nerve palsy caused by microvascular ischemia, which could be an effective novel method to promote recovery from diplopia. We think that the recovery of ischemic demyelination of a portion of the nerve is greatly assisted by an improvement in the cerebral blood flow.

Brachial plexus block of the posterior and the lateral cord using ropivacaine 7.5mg/mL.

We recently showed that the novel combination of a superficial cervical plexus block, a suprascapular nerve block, and the lateral sagittal infraclavicular brachial plexus block (LSIB) provides an alternative anaesthetic method for arthroscopic shoulder surgery. In this study, we hypothesised that the LSIB dose for this shoulder block could be significantly reduced by injecting only towards the shoulder relevant posterior and lateral cords. Our aim was to determine the minimum effective volume in 50% of the patients (MEV50 ) and to estimate the MEV95, when using ropivacaine 7.5mg/mL to block these cords. Twenty-three adult patients scheduled for hand surgery participated in the study. Considering the artery as a clock face with 12 o'clock ventral, the designated volume was injected immediately outside the arterial wall and between 8 and 9 o´clock. The in-plane technique was used. Block success was assessed 30minutes after withdrawal of the needle. Successful posterior cord block was defined as anaesthesia or analgesia of the axillary nerve. Successful lateral cord block was defined as either anaesthesia or analgesia, or >50% motor block of the musculocutaneous nerve. MEV50 was determined by the staircase up-and-down method. Logistic regression and probit transformation were applied to estimate MEV95 . MEV50 and MEV95 were 7.8mL [95% confidence interval (CI), 7.3-8.4] and 9.0mL (95% CI, 7.8-10.3), respectively. For single-deposit infraclavicular posterior and lateral cord block, the MEV95 of ropivacaine 7.5mg/mL was estimated to 9.0mL.

Over-discretized SENSE reconstruction and B0 correction for accelerated non-lipid-suppressed 1 H FID MRSI of the human brain at 9.4 T.

The aim of this work was to use post-processing methods to improve the data quality of metabolite maps acquired on the human brain at 9.4T with accelerated acquisition schemes. This was accomplished by combining an improved sensitivity encoding (SENSE) reconstruction with a B0 correction of spatially over-discretized magnetic resonance spectroscopic imaging (MRSI) data. Since MRSI scans suffer from long scan duration, investigating different acceleration techniques has recently been the focus of several studies. Due to strong B0 inhomogeneity and strict specific absorption rate (SAR) limitations at ultra-high fields, the use of a low-SAR sequence combined with an acceleration technique that is compatible with dynamic B0 shim updating is preferable. Hence, in this study, a non-lipid-suppressed ultra-short TE and TR1 H free induction decay MRSI sequence is combined with an in-plane SENSE acceleration technique to obtain high-resolution metabolite maps in a clinically feasible scan time. One of the major issues in applying parallel imaging techniques to non-lipid-suppressed MRSI is the presence of strong lipid aliasing artifacts, which if not thoroughly resolved will hinder the accurate quantification of the metabolites of interest. To achieve a more robust reconstruction, an over-discretized SENSE reconstruction (with direct control over the shape of the spatial response function) was combined with an over-discretized B0 correction. This method is compared with conventional SENSE reconstruction for seven acceleration schemes on four healthy volunteers. The over-discretized method consistently outperformed conventional SENSE, resulting in an average of 23±1.2% higher signal-to-noise ratio and 8±2.9% less error in the fitting of the N-acetylaspartate signal over a whole brain slice. The highest achievable acceleration factor with the proposed technique was determined to be 4. Finally, using the over-discretized method, high-resolution (97μL nominal voxel size) metabolite maps can be acquired in 3.75min at 9.4T. This enables the acquisition of high-resolution metabolite maps with more spatial coverage at ultra-high fields.

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

ObjectiveTo describe a novel ultrasound-guided posterior extraconal block in the dog. Study designProspective experimental cadaveric study. AnimalsA total of 13 Beagle Cross cadaver heads. MethodsAfter describing the ultrasound bony landmarks and posterior extraconal local regional technique in one head, 12 heads were used to evaluate the spreading of contrast and evaluate potential complications. A 5–8 MHz microconvex ultrasound probe was positioned caudal to the orbital ligament, with the beam orientated transversely, and then tilted caudally until the orbital fissure was visualized. After identifying the bony structures consistent with the orbital fissure, a needle was advanced using an in-plane technique and 0.5 mL of a 50:50 mixture of iohexol and methylene blue was injected. Computed tomography (CT) and dissection were used to evaluate successful injections and potential complications. The injection was considered successful if radiopaque contrast medium was 5 mm from the orbital fissure. Potential complications were defined as the presence of radiopaque contrast within the globe or the intracalvarial tissues. ResultsThe CT images confirmed contrast at the target site in 15/24 (63%) of the injections. Only two injections were found in the temporalis muscle; the rest of the injections were located in the extraconal space. No potential complications such as intracranial spreading of contrast, intravascular or intraocular injection were found. Conclusions and clinical relevanceThe technique can deliver contrast close to the main nerves which provide sensory and motor innervation to the eye. Further studies are needed to evaluate this technique in clinical cases.

Paths of femoral nerve catheters placed using ultrasound-guided in plane vs out of plane techniques: A randomized controlled clinical trial.

Background:Continuous blockade of the femoral nerve is widely used for postoperative analgesia after hip surgery. It can be achieved by ultrasound-guided placement of a femoral nerve catheter via either the in plane (IP) or out of plane (OOP) technique. On the basis of postoperative radiographs, we evaluated the paths of femoral nerve catheters with respect to both techniques and its effect on postoperative analgesia.Methods:Thirty-four patients were randomized to receive a radiopaque femoral nerve catheter via either the IP or OOP technique. The paths and tip position of the catheters were evaluated in postoperative frontal radiographs of the operated hip joint concerning a predefined target region and four neighboring regions. Pain scores were assessed using a numeric rating scale (0–10).Results:Sixteen IP patients and 18 OOP patients were included in the study. The catheter path was radiographically evaluated in 13 IP patients and in 10 OOP patients. The catheter tips were located within the target region in 39% of the IP group and in 50% of the OOP group. The catheter tip was 0.00 cm [−3.80 to 3.84] and −1.19 cm [−12.27 to 0.00] (median [range]) from the target region in the OOP group and IP group, respectively (P = .045). Catheters flipped distally more often in the IP group (IP: 61.5%, OOP: 10.0%; P = .01). There were no marked differences in the pain scores of either group.Conclusion:Femoral nerve catheters inserted by the ultrasound-guided IP technique flip distally more frequently than catheters inserted by the OOP technique. Moreover, the distance between the catheter tip and the trunk of the femoral nerve is greater for IP catheters than for OOP catheters. Despite these findings, postoperative analgesia did not seem to differ between the 2 techniques.

Coupled thermoelasticity analysis of carbon nano tube reinforced composite rectangular plate subjected to thermal shock

In the frame work of Lord-Shulman theory, transient response of a simply supported carbon nanotube reinforced composite (CNTRC) rectangular plate with different pattern of CNT distribution and under thermal shock is studied using generalized coupled thermoelasticity. Applying Fourier series expansion along the in-plane direction and state space technique along the thickness direction to the constitutive equations and governing differential equations of motion results in first state space differential equations which can be solved analytically in Laplace transform. Then response is obtained in time domain using inverse Laplace transform. Moreover, parametric study is conducted to assess the effect of pattern of CNT distribution, CNT volume fraction and pick of thermal shock on transient thermoelastic behavior of FG-CNTRC rectangular plate are examined.

A Cadaveric Study Investigating the Mechanism of Action of Erector Spinae Blockade.

Erector spinae block is an ultrasound-guided interfascial plane block first described in 2016. The objectives of this cadaveric dye injection and dissection study were to simulate an erector spinae block to determine if dye would spread anteriorly to the involve origins of the ventral and dorsal branches of the spinal nerves. In 10 unembalmed human cadavers, 20 mL of 0.25% methylene blue dye was injected bilaterally into the plane between the fifth thoracic transverse process and erector spinae muscle. An in-plane ultrasound-guided technique with the transducer orientated longitudinally was used. During dissection, superficial and deep muscles were identified, and extent of dye spread was documented in cephalocaudal and lateral directions. The ventral and dorsal rami of spinal nerves and dorsal root ganglion at each level were examined to determine if they were stained by dye. There was extensive cephalocaudad and lateral spread of dye deep and superficial to the erector spinae muscles. Except for 1 injection (from 20), the ventral rami were not stained by the dye. In only 2 injections did the dye track posteriorly through the costotransverse foramen to the dorsal root ganglion. In all other cases, the dorsal root ganglia were not involved in the dye injection. The dye stained the dorsal rami posterior to the costotransverse foramen. There was no spread of dye anteriorly to the paravertebral space to involve origins of the ventral and dorsal branches of the thoracic spinal nerves. Dorsal ramus involvement was posterior to the costotransverse foramen.

Efficacy of "over iliac crest method" for ultrasound-guided posterior lumbar plexus block: a comparison with manual palpation and sagittal positioning

Objective To evaluate the efficacy of over iliac crest for ultrasound-guided posterior lumbar plexus block by comparing with manual palpation and sagittal positioning. Methods A total of 75 patients, aged 25-64 yr, weighing 42-90 kg, with body mass index of 17-32 kg/cm2, of American Society of Anesthesiologists physical status Ⅰ-Ⅲ, scheduled for elective lower extremity surgery under ultrasound-guided posterior lumbar plexus block combined with parasacral sciatic nerve block, were divided into 3 groups (n=25 each) using a random number table method: manual palpation group (group M), sagittal positioning group (group S) and over iliac crest group (group O). Patients received ultrasound-guided posterior lumbar plexus block with in-plane technique using the corresponding positioning method in M, S and O groups.Successful blockade of each level was recorded at 30 min after injection.Time to determine the lumbar intervertebral space, puncture time for lumbar plexus block, the requirement for adjuvant drugs and block efficacy were recorded.The development of complications related to puncture and nerve block was also recorded. Results Compared with group M, the success rates of blockade at levels L1 and L2 were significantly increased, the success rates of blockade at levels L4 and L5 were decreased (P 0.05), the time to determine the lumbar intervertebral space was prolonged, and the requirement for adjuvant drugs was decreased during surgery in O and S groups, and the efficacy of block was significantly enhanced in group O (P 0.05). There was no significant difference in the puncture time for lumbar plexus block between the three groups (P>0.05). Complications related to puncture and nerve block were not found in three groups. Conclusion Over iliac crest provides higher success rate and better efficacy than manual palpation and sagittal positioning when used for lumbar plexus block. Key words: Lumbosacral plexus; Nerve block; Ilium

Quadratic Solid⁻Shell Finite Elements for Geometrically Nonlinear Analysis of Functionally Graded Material Plates.

In the current contribution, prismatic and hexahedral quadratic solid–shell (SHB) finite elements are proposed for the geometrically nonlinear analysis of thin structures made of functionally graded material (FGM). The proposed SHB finite elements are developed within a purely 3D framework, with displacements as the only degrees of freedom. Also, the in-plane reduced-integration technique is combined with the assumed-strain method to alleviate various locking phenomena. Furthermore, an arbitrary number of integration points are placed along a special direction, which represents the thickness. The developed elements are coupled with functionally graded behavior for the modeling of thin FGM plates. To this end, the Young modulus of the FGM plate is assumed to vary gradually in the thickness direction, according to a volume fraction distribution. The resulting formulations are implemented into the quasi-static ABAQUS/Standard finite element software in the framework of large displacements and rotations. Popular nonlinear benchmark problems are considered to assess the performance and accuracy of the proposed SHB elements. Comparisons with reference solutions from the literature demonstrate the good capabilities of the developed SHB elements for the 3D simulation of thin FGM plates.

Measurement of anisotropic coefficients of thermal expansion of SAC305 solder using surface strains of single grain with arbitrary orientation

The anisotropic coefficient of thermal expansions (CTEs) of SAC305 grain are measured using a full-field in-plane displacement measurement technique. Theoretical relationships among (1) the transversely-isotropic CTEs, (2) the surface strains of a specimen containing a single grain with arbitrary orientation, and (3) the direction of a grain orientation are derived first. Cube shape specimens that contain a single SAC305 grain are fabricated by controlling cooling rates. Thermally-induced displacements fields with a sub-micron resolution are documented on two perpendicular surfaces of the specimen as a function of temperature, and the engineering strains are calculated from the displacement fields. Two directional CTE values are determined from the theoretical relationships. The direction of the c-axis is also obtained during CTE calculations. The validity of the measurement is corroborated by comparing the c-axis direction obtained from the experiment with a grain orientation measured by the electron backscatter diffraction (EBSD) method.

Three-step procedure for safe internal jugular vein catheterization under ultrasound guidance.

Real-time ultrasound guidance for central venous catheterization has become a standard technique. This technique has been reported to yield high success rates and fewer complications compared with landmark techniques. However, it can be risky when the practitioner does not possess proper knowledge and skills. Lose sight of the needle tip can lead to severe complications such as arterial puncture or pneumothorax. Also, posterior wall penetration of the target vessels must be avoided. Misplacement of the catheter to other vessels can sometimes occur, and may only be discovered after the catheterization procedure. To avoid these complications, we perform a three-step procedure to place an internal jugular vein catheter under ultrasound guidance. The three steps are: (a) advance the needle tip to the internal jugular vein with a short-axis image with an out-of-plane technique, (b) rupture the anterior wall by using a long-axis image with an in-plane technique, and (c) confirm the guidewire position from the internal jugular vein to the brachiocephalic vein using a short-axis image, and a coronal image from the supraclavicular fossa. For safe needle advancement and penetration of the anterior wall of the vein, combined use of short-axis and long-axis images is helpful, and guidewire placement should be confirmed by scanning with the short-axis image and the coronal image.

Ultrasound-Guided Combined Interscalene-Cervical Plexus Block for Surgical Anesthesia in Clavicular Fractures: A Retrospective Observational Study.

Objective We aim to report our experiences regarding the implementation of the ultrasound-guided combined interscalene-cervical plexus block (CISCB) technique as a sole anesthesia method in clavicular fracture repair surgery. Materials and Methods Charts of patients, who underwent clavicular fracture surgery through this technique, were reviewed retrospectively. We used an in-plane ultrasound-guided single-insertion, double-injection combined interscalene-cervical plexus block technique. During the performance of each block, the block areas were visualized by using a linear transducer, and the needles were advanced by using the in-plane technique. Block success and complication rates were evaluated. Results and Discussion 12 patients underwent clavicular fracture surgery. Surgical regional anesthesia was achieved in 100% of blocks. None of the patients necessitated conversion to general anesthesia during surgery. There were no occurrences of acute complications. Conclusions The ultrasound-guided combined interscalene-cervical plexus block was a successful and effective regional anesthesia method in clavicular fracture repair. Prospective comparative studies would report the superiority of the regional technique over general anesthesia.

Efficacy of ultrasound-guided great auricular nerve block combined with general anesthesia for middle ear microsurgery in adult patients

Objective To evaluate the efficacy of ultrasound-guided great auricular nerve (GAN) block combined with general anesthesia for middle ear microsurgery in adult patients. Methods Sixty-four adult patients of both sexes, aged 18-60 yr, of American Society of Anesthesiologists physical statusⅠ or Ⅱ, scheduled for elective middle ear microsurgery, were assigned into 2 groups (n=32 each) using a random number table: GAN block combined with general anesthesia group (group GANB+ G) and general anesthesia group (group G). Patients received GAN block with 0.25% ropivacaine 2 ml using ultrasound-guided in-plane technique before anesthesia induction in group GANB+ G.Anesthesia induction and maintenance protocols (IV infusion of propofol and target-controlled infusion of remifentanil) were similar in two groups.Analgesia was performed with sufentanil, flurbiprofen axetil or parecoxib sodium after operation to maintain visual analog scale score <4 within 48 h after operation.The infusion duration and consumption of propofol and remifentanil, requirement for postoperative analgesia and occurrence of postoperative nausea and vomiting were recorded. Results Compared with group G, the consumption of remifentanil was significantly reduced, and the requirement for postoperative analgesia and incidence of postoperative nausea and vomiting were decreased in group GANB+ G (P<0.05 or 0.01). Conclusion Ultrasound-guided GAN block combined with general anesthesia provides better analgesic efficacy in the the perioperative period in adult patients undergoing middle ear microsurgery. Key words: Ear, middle; Ultrasonography; Nerve block

Ultrasound-Guided Posterior Antebrachial Cutaneous Nerve Block: Technical Description and Block Distribution in Healthy Volunteers.

The posterior antebrachial cutaneous nerve branches from the radial nerve proximal to the elbow and supplies sensation to the posterior aspect of the forearm. With a high-frequency linear transducer, the posterior antebrachial cutaneous nerve was identified in 8 healthy volunteers. Under aseptic conditions and with an ultrasound-guided in-plane technique, 1% lidocaine was injected circumferentially around the nerve. In each participant, the block was successful, and neither incidental blocks of other nerves nor any other complications were observed. These results demonstrate that the posterior antebrachial cutaneous nerve can be blocked to provide anesthesia or analgesia to the posterior forearm.

Ultrasonographical identification of the superficial circumflex iliac artery as a landmark for location of the femoral nerve in dogs

ObjectiveTo investigate the utility of identifying the superficial circumflex iliac artery (SCIA) via ultrasound as an anatomical landmark for ultrasound-guided femoral nerve block. Study designObservational study. AnimalsA group of six canine cadavers weighing >20 kg. MethodsPelvic limbs from six canine cadavers were examined to study the relationship between the SCIA and the femoral nerve. Ultrasonographic imaging of the SCIA in each limb was obtained with the transducer placed transversely in the medial aspect of the pelvic limb at the inguinal area. Subsequently, a needle was inserted in close proximity to the femoral nerve using an in-plane technique based on the anatomical relationship between the SCIA and femoral nerve. A total of 0.1 mL of colored latex was then injected at the location where the femoral nerve was expected to be in relationship to the SCIA. Gross dissection of the inguinal region in each pelvic limb was performed after injection. Positive nerve location was defined when the colored latex was in contact with the femoral nerve. ResultsA total of eleven pelvic limbs were injected because the SCIA could not be successfully visualized in one limb. Upon dissection, colored latex was found to be in direct contact with the femoral nerve in all 11 injected limbs. Conclusions and clinical relevanceWe concluded that the ultrasonographic visualization of the SCIA assisted in the accurate deposition of dye in proximity to the femoral nerve of canine cadavers. Further investigation will determine the efficacy of this technique for performing femoral nerve blocks.

Evaluation of the potential efficacy of an ultrasound-guided adductor canal block technique in dog cadavers

ObjectiveTo evaluate an ultrasound-guided technique for adductor canal (AC) block by describing the distribution of methylene blue around the AC, popliteal fossa, saphenous, tibial and common fibular nerves in dog cadavers. Study designProspective experimental trial. AnimalsTen mixed breed canine cadavers weighing 28.55 ± 3.94 kg. MethodsUltrasound scans of the AC were performed bilaterally in 10 canine cadavers. A high-frequency linear transducer was placed on the long axis of the pectineus muscle and using an in-plane technique, an insulated needle was introduced at a proximal to distal direction into the AC. Methylene blue 0.1% (0.3 mL kg−1) was administered followed by dissection. The presence of dye over the target nerves for ≥2 cm was considered successful distribution. Three of 10 cadavers were submitted to computed tomography (CT) and one of them to magnetic resonance (MR) evaluation. ResultsMethylene blue reached the AC in 20 (100%) and the popliteal fossa in 17 (85%) pelvic limbs. Staining was successful in the saphenous nerve (4.0 ± 1.57 cm) in 11 (55%) limbs, tibial nerve (2.65 ± 0.8 cm) in six (30%) and common fibular nerve (2.7 ± 0.9 cm) in four (20%). There was no evidence of staining around the motor branches of the femoral nerve. No intraneural or intravascular dye spread was found during dissections. Contrast distribution to the popliteal fossa was observed in three limbs (50%) in CT and in one (50%) MR image. Conclusions and clinical relevanceAlthough the tibial and common fibular nerves were not stained as often as the saphenous nerve, dye was encountered throughout the popliteal fossa near the nerves. The AC block may be useful for intra and postoperative analgesia in stifle surgery with minimal femoral motor dysfunction. However, further study is required to confirm its efficacy and safety in vivo.

Comparison of lumbar plexus block using the short\xa0axis in-plane method at the plane of the transverse process and at the articular process: a randomized controlled trial

BackgroundAlthough the safety and effectiveness of the short-axis in-plane method has been confirmed for lumbar plexus block, the operation is difficult and has a high rate of epidural spread at the plane of the articular process. Therefore, we developed a new in-plane technique, called the beach chair method, which displays images from the transverse process. We compared the operative difficulty and incidence of epidural spread of the beach chair method with those of the control method (at the plane of the articular process) in this randomized controlled clinical trial.MethodsSixty patients, aged 18 to 75 years, scheduled for unilateral arthroscopic knee surgery were randomized to receive double-guided lumbar plexus block by the beach chair method (n = 30) or the control method (n = 30) with 30 ml 0.5% ropivacaine hydrochloride; all patients received a sciatic nerve block with 10 ml 1% lidocaine hydrochloride and 10 ml 0.5% ropivacaine hydrochloride.ResultsThe incidence of epidural spread after lumbar plexus block was significantly lower in the beach chair group than that in the control group [1 case (3.3%) vs. 9 (30.0%), P = 0.006]. Moreover, the imaging time (34.2 ± 16.7 s vs. 48.9 ± 16.8 s, P = 0.001), needling time (85.0 ± 45.3 s vs. 131.4 ± 88.2 s, P = 0.013) and number of needle punctures (2.7 ± 1.3 vs. 4.5 ± 2.1, P = 0.000) were significantly lower in the beach chair group than those in the control group; the ultrasound visibility score of the beach chair group was better than that of the control group. There were no significant differences in the remaining indicators.ConclusionsThe beach chair method was easier and was associated with a lower incidence of epidural spread than the control method. Therefore, the beach chair method (at the plane of the transverse process) provides another promising option for lumbar plexus block for the non-obese population.Trial registrationChinese Clinical Trial Registry (ChiCTR), Registration number:ChiCTR-INR-15007505, registered on November 06, 2015.

In-plane x-ray diffraction for characterization of monolayer and few-layer transition metal dichalcogenide films

There is significant interest in the growth of single crystal monolayer and few-layer films of transition metal dichalcogenides (TMD) and other 2D materials for scientific exploration and potential applications in optics, electronics, sensing, catalysis and others. The characterization of these materials is crucial in determining the properties and hence the applications. The ultra-thin nature of 2D layers presents a challenge to the use of x-ray diffraction (XRD) analysis with conventional Bragg–Brentano geometry in analyzing the crystallinity and epitaxial orientation of 2D films. To circumvent this problem, we demonstrate the use of in-plane XRD employing lab scale equipment which uses a standard Cu x-ray tube for the analysis of the crystallinity of TMD monolayer and few-layer films. The applicability of this technique is demonstrated in several examples for WSe2 and WS2 films grown by chemical vapor deposition on single crystal substrates. In-plane XRD was used to determine the epitaxial relation of WSe2 grown on c-plane sapphire and on SiC with an epitaxial graphene interlayer. The evolution of the crystal structure orientation of WS2 films on sapphire as a function of growth temperature was also examined. Finally, the epitaxial relation of a WS2/WSe2 vertical heterostructure deposited on sapphire substrate was determined. We observed that WSe2 grows epitaxially on both substrates employed in this work under all conditions studied while WS2 exhibits various preferred orientations on sapphire substrate which are temperature dependent. In contrast to the sapphire substrate, WS2 deposited on WSe2 exhibits only one preferred orientation which may provide a route to better control the orientation and crystal quality of WS2. In the case of epitaxial graphene on SiC, no graphene-related peaks were observed in in-plane XRD while its presence was confirmed using Raman spectroscopy. This demonstrates the limitation of the in-plane XRD technique for characterizing low electron density materials.

Effect of anisotropy evolution on circular and oval hole expansion behavior of high-strength steel sheets

The circular and oval hole expansion behaviors of JSH440W and JSH590R high-strength steel sheets were investigated based on experiments and finite element (FE) simulations using three types of anisotropic yield functions: Hill48-r, Yld2000-2d, and 6-poly models. The effects of anisotropy evolution were specifically examined by performing FE simulation using the 6-poly anisotropic hardening (AH) model. Sheet-direction dependent workhardening characteristics were determined by using an in-plane stretch-bending technique. From this work, it was found that hole expansion behavior was strongly affected by anisotropy and its evolution. Thus, it is concluded that the use of AH model is essential for the accurate simulation of hole expansion processes.