Nerve Staining Research Articles

The comparison of spread of methylene blue after the Pericapsular Nerve Group block and a double injection selectively targeting the articular branches to the anterior hip capsule in human cadavers.

In this study, the spread of methylene blue was compared between an ultrasound-guided Pericapsular Nerve Group (PENG) block and a double injection technique, where the approach towards the inferomedial acetabulum was added to the latter. The two techniques were performed in 11 fresh frozen cadavers. The spread was measured after anatomical dissection in which the supplying femoral and obturator nerves were identified. Our study demonstrates adequate staining of the iliac bone with comparable distal and medial spread in both techniques, indicating that the PENG block with a single injection is adequate in blocking the hip capsule with 10 mL local anesthetics. Staining of the femoral nerve occurred in 2/6 specimens after the PENG block, and staining of the obturator nerve in 1 specimen in each group.

Ultrasound-Guided Proximal Radial, Ulnar, Median and Musculocutaneous (RUMM) Nerve Block Technique in Rabbit (Oryctolagus cuniculus) Cadavers: Medial vs. Lateral Approach

This prospective, experimental, randomised, assessor-blinded cadaveric study was undertaken to describe the sono-anatomical features of the radial, ulnar, median and musculocutaneous (RUMM) nerves in rabbits and to develop and evaluate an ultrasound (US)-guided proximal RUMM block technique comparing a medial versus a lateral approach. A total of 13 adult rabbit cadavers were used. In Phase I of the study, four cadavers were used for anatomical dissection and to design and test a lateral and medial single injection point US-guided proximal RUMM block technique, while in Phase II, the medial and lateral approaches were randomly performed on nine cadavers administering 0.1 mL kg−1 injectate. After dissection, nerve staining was categorised as adequate (all nerves stained ≥4 mm) or inadequate (at least one nerve not stained or stained <4 mm). Staining spread was compared with Fisher’s exact test, with p < 0.05 considered statistically significant. From Phase I, the axillary fascia containing all RUMM nerves was identified. The radial nerve exited the fascia right after the humeral head. In the lateral approach, the transducer was angled at 80° to the humerus longitudinal axis. In the medial approach, the transducer was placed perpendicularly to the humerus longitudinal axis. In both approaches, the brachial artery appeared as a rounded and anechoic structure, the musculocutaneous nerve as hypoechoic and oval and the radial nerve as a honeycomb, and the ulnar and median nerves were identified adjacent to each other. The radial nerve was selected as the injection point for both approaches using an in-plane technique. In Phase II, the injectate was found outside the axillary fascia in zero out of nine and five out of nine thoracic limbs, with an adequate staining in nine of nine and two of nine injections (p < 0.01) using the medial and lateral approach, respectively. Thus, a US-guided proximal RUMM block technique is feasible in rabbits, and the medial approach demonstrated evidence of a more consistent stain of the RUMM nerves.

Anatomical study of trigeminal‐facial nerve communications: Application to facial transplant surgery

AbstractUnderstanding the distribution of nerves in the superficial layer of the face and the communication (nerve anastomosis) between them is essential for preventing paralysis during tumor removal and for planning during nerve grafting. However, communication between the peripheral branches of the trigeminal and facial nerves has not been fully elucidated owing to the delicacy of their structures and the ambiguity of definitions in previous reports. In this study, we used whole‐mount nerve staining to differentiate between the two types of interaction between the trigeminal and facial nerves. “Nerve communication” is defined as an exchange of fibers between the two nerves, while “nerve crossing” indicates that only the epineuria are in close contact, with no exchange of fibers. The skin and soft tissues of six human faces were excised, and the nerves were stained using Sihler's method. The peripheral branches of the ophthalmic nerve showed no communication with the facial nerve. In half of the cases (3/6), the infraorbital nerve, representing the peripheral branch of the maxillary nerve, communicated with the facial nerve. Peripheral branches of the mandibular nerve communicated with the facial nerve via the auriculotemporal (6/6), buccal (6/6), and mental (3/6) nerves. Our findings demonstrate moderate communication between the peripheral branches of the trigeminal and facial nerves in the maxillary nerve region but more concentrated communication in the mandibular nerve region.

Anatomical assessments of injectate spread stratified by the volume of the intertransverse process block at the T2 level

BackgroundThis cadaveric study aimed to analyze injectate spread to target nerves during a single-injection, ultrasound-guided intertransverse process block.MethodsAn ultrasound-guided intertransverse process block with three different injectate volumes was administered to...

A Novel Ultrasound-Guided Cervical Plexus Block: A Cadaveric Canine Study.

The ultrasound-guided cervical plexus plane (US-CPP) block has proven effective in humans; yet its application in dogs remains unexplored. This study aimed to describe a novel US-CPP approach in canines. A local sonoanatomy was mapped, the injection technique was tested, and a gross anatomical dissection (GAD) was performed on one cadaver. The bilateral injectate spread and nerve staining were then evaluated via a CT scan and GAD in the six cadavers. The transducer was aligned parallel to the cervical spine, caudal to the atlas. After identifying the cleidocervical and omotransversarius muscles and the C2-C3 interfascial plane, a spinal needle was inserted in-plane, and 0.15 mL/kg of a dye-contrast solution was injected. CT imaging showed the contrast reaching the C1, C2, and C3 vertebral bodies in 3 out of 12 (3/12), 11/12, and 12/12 injections, respectively, and the C4, C5, and C6 vertebrae in 8/12, 5/12, and 1/12 injections, respectively. No contrast was detected in the epidural space. The C1, C2, C3, C4, and C5 nerves were stained in 3/12, 10/12, 8/12, 2/12, and 0/12 injections, respectively. No significant differences were observed between the groups (p > 0.05). A single US-CPP injection successfully stained the C2 and C3 nerves, indicating the potential clinical applicability, although the injected volume rarely reached C4 and C5.

Ultrasound-Guided Deep Serratus Plane Block in Cat Cadavers (Felis catus): A Description of Dye and Contrast Media Distribution.

The serratus plane block is an ultrasound-guided anaesthetic technique that aims to provide analgesia to the lateral thoracic wall cranial to the 8th rib. This block can be performed in a superficial (between the latissimus dorsi and the serratus ventralis thoracis (SVT) muscles) or deep plane (between the intercostales externi and the SVT muscles). This study aimed to assess the distribution and nerve staining of a mixture of 0.4 mL kg-1 of methylene blue and iopromide 50:50 performing a deep serratus plane (DSP) block at the level of the 5th rib. We hypothesise that this technique would be feasible and could stain the rami cutanei laterales (RCL) of the intercostales nerves cranial to the 8th rib in cat cadavers. This study was divided into two phases. Phase 1 consisted of an anatomical study of the thoracic wall (2 cadavers). Phase 2 consisted of the ultrasound-guided injection of the aforementioned mixture and the assessment of its distribution by computed tomography and anatomical dissection (12 cadavers). Contrast media spread a median of 5.5 (2.5-7.5) intercostal spaces. The dye stained a median of 3 (0-5) RCL, affecting RCL 2 (17.39%), RCL 3 (57.17%), RCL 4 (78.26%), RCL 5 (91.30%), RCL 6 (78.26%), and RCL 7 (8.70%) within the DSP. Occasionally, the rami dorsales laterales and the thoracicus longus nerve were stained. Based on these findings, the DSP block performed with a volume of 0.4 mL kg-1 of an anaesthetic could provide analgesia in the area innervated from T4 to T6.

Cimifugin Alleviates Chronic Constriction Injury of the Sciatic Nerve by Suppressing Inflammatory Response and Schwann Cell Apoptosis.

Inflammation and Schwann cell apoptosis play critical roles in neuropathic pain after sciatic nerve injury. This study aimed to explore the function and mechanism of cimifugin in lipopolysaccharide (LPS)-stimulated rat Schwann cells and sciatic nerves of rats treated with chronic constriction injury (CCI). Thermal, mechanical and cold hyperalgesia of rats in response to cimifugin or mecobalamin (the positive drug control) treatment were evaluated through behavioral tests. H&E staining of sciatic nerves was performed for pathological observation. ELISA was conducted to assess concentrations of inflammatory cytokines in rat serum and sciatic nerves. The intensity of S100β in sciatic nerves was determined using immunohistochemistry. Flow cytometry analysis was conducted for detection of Schwann cell apoptosis. RT-qPCR was performed to measure mRNA levels of inflammatory factors in Schwann cells. Immunofluorescence staining was performed to detect cellular p65/NF-κB activity. Western blotting was performed to quantify protein levels of apoptotic markers and factors associated with the NF-κB and MAPK pathways in rat nerves and Schwann cells. As shown by experimental data, cimifugin mitigated thermal, mechanical and cold hyperalgesia of CCI rats. Cimifugin repressed inflammatory cell infiltration, reduced proinflammatory cytokine levels while increasing anti-inflammatory factor (IL-10) level in serum or sciatic nerves of CCI rats. Cimifugin enhanced S100β expression and downregulated apoptotic markers in vivo. The anti-inflammatory and anti-apoptotic properties of cimifugin were verified in the LPS-stimulated Schwann cells. Moreover, cimifugin suppressed nuclear translocation of p65 NF-κB in vitro and repressed the phosphorylation of IκB, p65 NF-κB, p38 MAPK, ERK1/2, as well as JNK in CCI rats. In conclusion, cimifugin alleviates neuropathic pain after sciatica by suppressing inflammatory response and Schwann cell apoptosis via inactivation of NF-κB and MAPK pathways.

Sensory neuroimmune signaling in the pathogenesis of Stevens-Johnson syndrome and toxic epidermal necrolysis

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are life-threatening cutaneous reactions often triggered by medications. While the involvement of CD8+ T cells causing keratinocyte death is well recognized, the contribution of neural elements to the persistent skin inflammation has been largely overlooked. To investigate the potential neuroimmune regulation in SJS/TEN. Unbiased single-cell RNA sequencing and flow cytometry were performed using circulating CD8+ T cells from healthy controls and patients with SJS/TEN. ELISA and LEGENDplex assays were respectively used to detect neuropeptides and inflammatory mediators. Skin tissues were examined by immunofluorescence staining for neuropeptide-associated nerves and cytokine receptors. Calcium imaging, Smart-seq, and a 3D skin model were employed for cultured human CD8+ T cells. The unbiased RNA-sequencing revealed an upregulation of the receptor for neuropeptide calcitonin gene-related peptide (CGRP), known as RAMP1, in effector CD8+ T cells in SJS/TEN. Increased CGRP+ nerve fibers and CGRP levels, along with upregulated IL-15R and IL-18R on CD8+ T cells, were displayed in the affected skin of SJS/TEN. The CGRP-RAMP1 axis was necessary and sufficient to enhance receptors for IL-15 and IL-18 and cytotoxic activities in CD8+ T cells, ultimately resulting in keratinocyte apoptosis. Calcium influx was detected in CGRP-stimulated CD8+ T cells. HCN2, a hyperpolarization-activated cation channel, was required for this process and the subsequent cytotoxic effects. Our study highlights the role of neural elements in regulating CD8+ T cell-mediated inflammatory responses and provides new potential translational targets to improve the outcomes of severe cutaneous drug reactions.

Akkermansia muciniphila improve cognitive dysfunction by regulating BDNF and serotonin pathway in gut-liver-brain axis

BackrgroundAkkermansia muciniphila, a next-generation probiotic, is known as a cornerstone regulating the gut-organ axis in various diseases, but the underlying mechanism remains poorly understood. Here, we revealed the neuronal and antifibrotic effects of A. muciniphila on the gut-liver-brain axis in liver injury.ResultsTo investigate neurologic dysfunction and characteristic gut microbiotas, we performed a cirrhosis cohort (154 patients with or without hepatic encephalopathy) and a community cognition cohort (80 participants in one region for three years) and validated the existence of cognitive impairment in a 3,5-diethoxycarbonyl-1,4-dihydrocollidine-induced hepatic injury mouse model. The effects of the candidate strain on cognition were evaluated in animal models of liver injury. The expression of brain-derived neurotrophic factor (BDNF) and serotonin receptors was accessed in patients with fibrosis (100 patients) according to the fibrosis grade and hepatic venous pressure gradient. The proportion of A. muciniphila decreased in populations with hepatic encephalopathy and cognitive dysfunction. Tissue staining techniques confirmed gut-liver-brain damage in liver injury, with drastic expression of BDNF and serotonin in the gut and brain. The administration of A. muciniphila significantly reduced tissue damage and improved cognitive dysfunction and the expression of BDNF and serotonin. Isolated vagus nerve staining showed a recovery of serotonin expression without affecting the dopamine pathway. Conversely, in liver tissue, the inhibition of injury through the suppression of serotonin receptor (5-hydroxytryptamine 2A and 2B) expression was confirmed. The severity of liver injury was correlated with the abundance of serotonin, BDNF, and A. muciniphila.ConclusionsA. muciniphila, a next-generation probiotic, is a therapeutic candidate for alleviating the symptoms of liver fibrosis and cognitive impairment.Graphical

Successful treatments of idiopathic retinal vasculitis, aneurysms, and neuroretinitis (IRVAN) syndrome-related macular edema and exudation by intravitreal aflibercept injection in a senile patient: A case report.

The prevalence of idiopathic retinitis, vasculitis, aneurysms, and neuroretinitis (IRVAN) syndrome is <1/1,000,000, and it tends to occur in young women. Panretinal photocoagulation, focal laser photocoagulation, peripheral cryopexy, vitrectomy, and corticosteroid therapy are the traditional treatments. We reported a case of a senile patient with IRVAN syndrome who presented with severe exudation in both eyes and macular edema in the left eye, successfully treated by serial intravitreal aflibercept injections. A 77-year-old Taiwanese woman complained of progressive blurred vision in the left eye and ocular examinations revealed a visual acuity of 20/125 in the left eye. Indirect fundoscopy and fluorescein angiography showed bilateral multiple aneurysms, vasculitis, optic nerve staining, and neovascularizations. In addition, optical coherence tomography demonstrated macular edema with subretinal fluid and exudations in the left eye. Monthly intravitreal injections of antivascular endothelial growth factor with aflibercept 2.0 mg were administered in the left eye. The visual acuity in the left eye improved to 20/50 after 18 months of treatment. Macular edema and subretinal fluid regressed. Furthermore, vessel leakage and optic disc staining also improved. This case is the first to demonstrate successful treatment of IRVAN syndrome-related central macular edema and exudations, in the absence of neovascularization, using a series of intravitreal aflibercept injections as monotherapy.

Sihler's Staining of the Thoracic Cutaneous Nerve and its Significance

Sihler's Staining of the Thoracic Cutaneous Nerve and its Significance

Ultrasound-guided quadratus lumborum block in sheep: A cadaveric study.

This prospective anatomical study aimed to establish an ultrasound-guided technique to the quadratus lumborum (QL) plane in sheep cadavers. Thirteen cadavers, weighing less than 117 kg, were included. In phase 1, one cadaver underwent dissection and two cadavers underwent 3D computed tomographic reconstruction for anatomical evaluation of the thoracolumbar region. In phase 2, two cadavers were used to compare two ultrasound techniques to the QL plane: lateral to the QL muscle with a transversal approach (LQL) and transmuscular between QL and psoas muscles with a longitudinal approach (TQL). For LQL, the reference was the first lumbar transverse process, whereas for TQL, it was the intertransverse region between the first and second lumbar vertebrae. The needle was advanced in-plane towards the specific target for each technique and a total of four injections were performed using 0.4 ml kg-1 of a dye-lidocaine solution. In phase 3, 10 cadavers received bilateral LQL injections (n = 20). All cadavers were then dissected to evaluate spread of dye. In phase 2, following LQL injections, no dye was observed in undesired locations; however, the dye was noted in the retroperitoneal space (1/2) after TQL injections. In phase 3, the 13th thoracic, first, second, third lumbar nerves, and sympathetic trunk segments were stained in 80%, 95%, 100%, 45% and 35% of the injections, respectively. In conclusion, the LQL technique was feasible, allowing staining of the spinal nerves innervating the cranial abdomen in sheep cadavers. Further studies in live animals are warranted.

The Compartmental Tongue.

Tongue anatomy and function is widely described as consisting of four extrinsic muscles to control position and four intrinsic muscles to control shape. This myoarchitecture cannot, however, explain independent tongue body and blade movement nor accurately model the subtlety of observed lingual shapes. This study presents the case for a finer neuromuscular structure and functional description. Using the theoretical framework of the partitioning hypothesis, evidence for neuromuscular compartments of each of the lingual muscles was discerned by reviewing studies of lingual anatomy, hypoglossal nerve staining, hypoglossal motoneuron axon tracing, muscle fiber type distribution, and electromyography. Muscle fibers of the visible human female were manually traced to produce a three-dimensional atlas of muscular compartments. A kinematic study was undertaken to determine the degree of independent movement between different parts of the tongue. A simple biomechanical model was used to demonstrate how synergistic groups of compartments can control sectors of the tongue. Results indicated as many as 10 compartments of genioglossus, two each of superior and inferior longitudinal, eight of styloglossus, three of hyoglossus, and six each of transversus and verticalis, while palatoglossus may not have a significant role in tongue function. Kinematic analysis indicated independent control of five sectors of the tongue body, and biomechanical modeling demonstrated how this control may be achieved. Evidence is presented for a lingual structure based on neuromuscular compartments, which work together to position and shape sectors of the tongue and independently control tongue body and blade.

Ultrasound-guided sciatic nerve block injections in barred owl (Strix varia) cadavers

ObjectiveTo describe an ultrasound-guided approach to the sciatic nerve and the distribution of nerve staining using two injectate volumes of dye in barred owls. Study designDescriptive, randomized, assessor-blinded, cadaveric study. AnimalsTwelve barred owl cadavers. MethodsThe sciatic nerve was visualized with a 13-6 MHz linear ultrasound probe placed on the medial aspect of the proximal femur in barred owl cadavers. A needle was inserted at the proximal caudal thigh, and cranially advanced in-plane until the tip was immediately adjacent and ventral to the sciatic nerve. Eleven owls were injected bilaterally with a 1:1 solution of 1% methylene blue and 0.5% ropivacaine, with high-volume (HV; 0.4 mL kg–1) and low-volume (LV; 0.2 mL kg–1) treatments. Nerve staining ≥ 1 cm circumferentially was determined by dissection 15 minutes post-injection. The coelom was then opened to inspect for aberrant dye spread. In one barred owl cadaver, a 1:1 solution of 1% methylene blue and 74% ioversol contrast was injected, and computed tomography was performed immediately before and 15 minutes after injection for evaluation of injectate spread. ResultsThe HV treatment (0.4 mL kg–1) resulted in successful nerve staining in 100% of injections, whereas the LV treatment (0.2 mL kg–1) resulted in successful nerve staining in 91% of injections. There was no leakage of injectate into undesired locations (e.g. coelomic cavity) in any cadaver. Conclusions and clinical relevanceIn barred owls, the sciatic nerve can be visualized with ultrasound and injecting a ropivacaine/dye solution under ultrasound guidance successfully stained the sciatic nerve in the majority of cases. This technique holds potential for providing analgesia distal to the stifle joint; however, further investigations are necessary to evaluate its practical application in a clinical setting.

Comparison between Ultrasonographic-Guided Temporal and Coronoid Approaches for Trigeminal Nerve Block in Dogs: A Cadaveric Study.

The trigeminal nerve is responsible for innervating the periorbita. Ultrasound-guided trigeminal block is employed in humans for trigeminal neuralgia or periorbital surgery. There are no studies evaluating this block in dogs. This study aims to evaluate and compare two approaches (coronoid and temporal) of the trigeminal nerve block. We hypothesised superior staining with the coronoid approach. Thirteen dog heads were used. After a preliminary anatomical study, two ultrasound-guided injections per head (right and left, coronoid and temporal approach, randomly assigned), with an injectate volume of 0.15 mL cm-1 of cranial length, were performed (iodinated contrast and tissue dye mixture). The ultrasound probe was placed over the temporal region, visualising the pterygopalatine fossa. For the temporal approach, the needle was advanced from the medial aspect of the temporal region in a dorsoventral direction. For the coronoid approach, it was advanced ventral to the zygomatic arch in a lateromedial direction. CT scans and dissections were conducted to assess and compare the position of the needle, the spread of the injectate, and nerve staining. No significant differences were found. Both approaches demonstrated the effective interfascial distribution of the injectate, with some minimal intracranial spread. Although the coronoid approach did not yield superior staining as hypothesised, it presents a viable alternative to the temporal approach. Studies in live animals are warranted to evaluate clinical efficacy and safety.

Therapeutic Effect of Schwann Cell-Like Cells Differentiated from Human Tonsil-Derived Mesenchymal Stem Cells on Diabetic Neuropathy in db/db Mice.

Diabetic neuropathy (DN) is the most common complication of diabetes, and approximately 50% of patients with this disease suffer from peripheral neuropathy. Nerve fiber loss in DN occurs due to myelin defects and is characterized by symptoms of impaired nerve function. Schwann cells (SCs) are the main support cells of the peripheral nervous system and play important roles in several pathways contributing to the pathogenesis and development of DN. We previously reported that human tonsil-derived mesenchymal stem cells differentiated into SCs (TMSC-SCs), named neuronal regeneration-promoting cells (NRPCs), which cells promoted nerve regeneration in animal models with peripheral nerve injury or hereditary peripheral neuropathy. In this study, NRPCs were injected into the thigh muscles of BKS-db/db mice, a commonly used type 2 diabetes model, and monitored for 26weeks. Von Frey test, sensory nerve conduction study, and staining of sural nerve, hind foot pad, dorsal root ganglia (DRG) were performed after NRPCs treatment. Von Frey test results showed that the NRPC treatment group (NRPC group) showed faster responses to less force than the vehicle group. Additionally, remyelination of sural nerve fibers also increased in the NRPC group. After NRPCs treatment, an improvement in response to external stimuli and pain sensation was expected through increased expression of PGP9.5 in the sole and TRPV1 in the DRG. The NRPCs treatment may alleviate DN through the remyelination and the recovery of sensory neurons, could provide a better life for patients suffering from complications of this disease.

A Feasibility Study for a Novel Trans-infraorbital Canal Approach to the Maxillary Nerve in Pigs (Sus domesticus).

Experimental maxillofacial surgery is commonly performed in pigs; however, locoregional anesthesia of this area has not been described. This study evaluated the feasibility of a novel maxillary nerve block approach. In part I, cadavers were used to determine anatomic landmarks and assess maxillary nerve dye staining by using 0.03 mL kg-1 of a 1:10 mixture of commercial food dye and 0.5% bupivacaine. In part II, 10 additional pig cadavers underwent bilateral ultrasound-guided maxillary nerve blocks by using trans-infraorbital canal needle placement. The maxillary nerve was harvested and scored based on degree of staining (0 and 1, absent or incomplete staining; 2, staining; >1 cm circumferentially). Intracranial and intraconal spread of dye was evaluated. A Kruskal-Wallis test was used to compare infraorbital canal length estimated either externally via landmarks, internally via ultrasound, or actually measured after dissection. In 18 of 20 (90%) injections, successful staining (score = 2) of maxillary nerves was obtained for a nerve length of 2.4 ± 0.3 cm. Two of 20 cases (10%) had inadequate staining (score <2). At dissection of these 2 cases, the needle tip was observed to have collided with an unerupted tooth (third molar). No intracranial or intraconal spread of dye was observed. We detected no statistical differences between the estimated external, estimated internal, or actual dissection methods for measurement of infraorbital canal length (P = 0.3). Ultrasound-guided trans-infraorbital maxillary nerve block in pigs is a feasible technique, warranting further work to evaluate its in vivo efficacy and safety.

Ultrasound-guided external oblique intercostal block technique in rabbits (Oryctolagus cuniculus): a cadaveric study

BackgroundLocoregional anesthesia is an essential component of multimodal analgesic and anesthetic techniques. However, few are described in rabbits, especially those aimed at the cranial abdominal wall. The aim of this study was to describe the external oblique intercostal (EOI) block technique in rabbits and compare the spread of two injectate volumes across the paracostal region and cranial abdominal wall. MethodsEight rabbit cadavers (16 hemithoraces) were randomized to receive ultrasound-guided injections between the external abdominal oblique and external intercostal muscles. Each rabbit received 0.25 ml/kg (LV) and 0.5 ml/kg (HV) of 1% new methylene blue with immediate tissue dissection. Site of needle insertion, spread of injectate, and number of stained intercostal spaces and nerves were assessed by a blinded investigator. ResultsInjection points ranged from intercostal spaces 5-12. There were no differences between HV and LV groups in the number of covered intercostal spaces or dorsal, caudal, and total (cranial + caudal) spread. There was significantly more ventral and cranial spread in the HV group as well as staining of intercostal nerves. Conclusions and Clinical RelevanceInjection within the EOI fascial plane successfully stained intercostal nerves associated with the thoracic wall and cranial abdomen; higher volumes provided significantly more spread in the cranial and ventral directions and stained more intercostal nerves. While the EOI block using a volume of 0.5 ml/kg could be a technique used to provide regional anesthesia of the rabbit paracostal region and cranial abdomen, future studies would be needed to determine clinical safety and efficacy.

Ultrasound-guided and ‘blind’ sciatic nerve injection techniques: Comparison in rat cadavers

ObjectiveTo compare the success rate and extent of sciatic nerve staining with a bupivacaine–dye solution using two injection techniques: ‘blind’ or ultrasound-guided approach. Study designProspective, experimental, randomized, cadaveric study. AnimalsAdult female Wistar rat cadavers [n = 24, mass 352 g (323–374)]. MethodsEach sciatic nerve was randomly allocated to one of two groups: ‘blind’ (group B) or ultrasound-guided approach (group US) to injection. Following injection of bupivacaine–dye solution (0.1 mL), gross anatomical dissection was performed to visualize nerve staining, categorizing it as either positive or negative. The length of nerve staining was then measured and visual inspection conducted to identify potential nerve damage. Fisher's exact test was used to compare positive or negative nerve staining, and the Wilcoxon signed rank test used to compare the length of nerve staining between groups. ResultsIn group B, the bupivacaine–dye solution stained 16/24 sciatic nerves (67% success). In group US, staining was successfully observed in all 24 nerves (100% success, p < 0.004). The length of nerve staining [median (interquartile range)] was 2 (2–3) mm in group B and 5 (4–6) mm in group US (p < 0.001). One sciatic nerve in group B had injectate distributed over 16 mm, suggestive of an intraneural injection. No signs of laceration or nerve damage were visible under 6× magnification in either group. Conclusions and clinical relevanceThe ultrasound-guided approach for sciatic nerve injection demonstrated a higher success rate with superior injectate distribution when compared with the ‘blind’ approach. Ultrasound guidance is recommended over a ‘blind’ approach for sciatic nerve block in rats when possible.

Renal denervation improves cardiac function independently of afterload and restores myocardial norepinephrine levels in a rodent heart failure model

Renal nerves play a critical role in cardiorenal interactions. Renal denervation (RDN) improved survival in some experimental heart failure (HF) models. It is not known whether these favorable effects are indirect, explainable by a decrease in vascular afterload, or diminished neurohumoral response in the kidneys, or whether RDN procedure per se has direct myocardial effects in the failing heart. To elucidate mechanisms how RDN affects failing heart, we studied load-independent indexes of ventricular function, gene markers of myocardial remodeling, and cardiac sympathetic signaling in HF, induced by chronic volume overload (aorto-caval fistula, ACF) of Ren2 transgenic rats. Volume overload by ACF led to left ventricular (LV) hypertrophy and dysfunction, myocardial remodeling (upregulated Nppa, MYH 7/6 genes), increased renal and circulating norepinephrine (NE), reduced myocardial NE content, increased monoaminoxidase A (MAO-A), ROS production and decreased tyrosine hydroxylase (+) nerve staining. RDN in HF animals decreased congestion in the lungs and the liver, improved load-independent cardiac function (Ees, PRSW, Ees/Ea ratio), without affecting arterial elastance or LV pressure, reduced adverse myocardial remodeling (Myh 7/6, collagen I/III ratio), decreased myocardial MAO-A and inhibited renal neprilysin activity. RDN increased myocardial expression of acetylcholinesterase (Ache) and muscarinic receptors (Chrm2), decreased circulating and renal NE, but increased myocardial NE content, restoring so autonomic control of the heart. These changes likely explain improvements in survival after RDN in this model. The results suggest that RDN has remote, load-independent and favorable intrinsic myocardial effects in the failing heart. RDN therefore could be a useful therapeutic strategy in HF.