Comparison of two volumes for sciatic perineural injection using 1% methylene blue in rabbit cadavers

ABSTRACT The purpose of this study was to assess the efficacy of a blind technique for sciatic and femoral nerve block in rabbit cadavers by evaluating the spread of 1% methylene blue at two different volumes. Nine recently euthanized rabbits weighing 2.5(0.3kg were used. The sciatic (SN) and femoral (FN) nerves of each limb were randomly assigned for injection with 1% methylene blue at 0.2mL/kg (G0.2) or 0.3mL/kg (G0.3). Nerves were dissected and measured for depth and extension of staining (cm). Mean comparisons were performed using paired t test. The relation between volume and nerve staining ( 2cm was assessed using chi-square test. The mean depth of SN was 1.9±0.2 and 1.6±0.3cm and staining 1.9±1.4 and 2.0±1.2cm, respectively in G0.2 and G0.3. No relation was found between depth and dye spread and there was no association between nerve staining ( 2.0cm and volume of solution. The FN failed to be stained in all subjects. In conclusion, SN injection can be successfully performed without guidance in rabbits. The lower volume (0.2mL/kg) is recommended to avoid systemic toxicity.

Axillary ultrasound-guided approach for the brachial plexus in pig cadavers: A descriptive study

Effective multimodal analgesia techniques are required when pigs are used as models in orthopedic human research. Regional anesthesia is a widely used technique to provide perioperative analgesia in animals undergoing orthopedic surgery. The brachial plexus (BP) block is indicated to desensitize the forelimb in many species but has not been yet described in pigs. The main aims of this study were to develop an ultrasound-guided axillary approach for the BP and to evaluate injectate spread and nerve staining in pig cadavers. Eight fresh F1 cross breed German Large White and German Landrace male pig cadavers were enrolled. Two cadavers were used for anatomical dissection of the axillary space and to determine the disposition of the BP. Six cadavers were used to perform a bilateral axillary ultrasound-guided approach for the BP, and after injecting 0.3 ml/kg of a solution of 2% lidocaine and new methylene blue (L-NMB), these were dissected to determine injectate spread and nerve staining. Upon dissection, the BP was observed in all the cases surrounded by the axillary sheath and in close proximity to the axillary artery. Ultrasonographic scanning and guidance for the approach to the BP was feasible in all cadavers and upon dissection, all the nerves forming the BP were stained in all their quadrants and in all the cases. In conclusion, the injection of 0.3 ml/kg of L-NMB through an ultrasound-guided axillary approach to the BP was feasible and adequate to entirely stain the BP in all pig cadavers. Further clinical studies are required to evaluate the effectiveness of this technique in live animals.

Refining the rat sciatic nerve block: a novel ultrasound-guided technique

Murine translational models are an important tool to understand pain pathophysiology. One procedure used frequently in murine research is the sciatic nerve block. This study sought to demonstrate the use of ultrasound-guided sciatic nerve block in a cadaveric murine model. A total of 40 injections were performed in 20 Sprague–Dawley male 18-month-old rat cadavers. Necropsy was performed to identify staining of the sciatic nerve. Staining with methylene blue occurred in 40 of 40 ultrasound-guided injections. The extremely accurate nature of this block under ultrasound guidance is favorable for future translational studies in rats undergoing sciatic nerve blocks. This method may represent a significant improvement in current methods.

Adult Neurogenesis in Peripheral Nervous System

Although postnatal neurogenesis has been discovered in some regions of the peripheral nervous system (PNS), only indirect evidences indicated that some progenitors in the adult sciatic nerve and dorsal root ganglion (DRG) serve as a source of newly born sensory neurons. Here, we report the discovery of neurons and neuronal stem cells in the adult rat sciatic nerve. Lineage tracing detected a population of sciatic nerve neurons as progeny of adult neuronal stem cells. With the further finding of labeled DRG neurons in adult transgenic rats with local sciatic nerve staining, we propose a model of adult neurogenesis in the sciatic nerve in which neuronal stem cells in sciatic nerve mature as sensory neurons in adults along the sciatic nerve to DRG. This hypothesis provides a new way to understand sensory formation in adults. Those neuronal stem cells in the sciatic nerve may help to therapy of nerve trauma and disease in the future.

Novel ultrasound-guided lateral approach for femoral nerve block in cats: a pilot study

Objectives The aim of this study was to describe the technique for a novel lateral approach to femoral nerve block in cat cadavers. Methods Five feline cadavers were used in our prospective cadaveric experimental study. Ultrasonography was used to identify the anatomy injection site. Both pelvic limbs were injected with a volume (0.1 ml/kg) of methylene blue in each cat. The cadavers were placed in lateral recumbency, with the limb to be blocked positioned uppermost. The transducer was held perpendicular to the most proximal area of the pelvic limb, ventral to the greater trochanter and slightly cranial to the femur. Methylene blue was injected after the localisation of the femoral nerve. Immediately after the injection, the cat was turned and the technique was repeated on the contralateral side. After performing the ‘block’ in both limbs, the area was dissected bilaterally and the success was evaluated. A positive femoral nerve staining was considered for a coverage of ⩾1 cm. Results A total of 10 ultrasound-guided femoral nerve injections were performed. Ninety percent (n = 9/10) of the nerves were successfully dyed. Conclusions and relevance The novel ultrasound-guided lateral approach may be suitable and reproducible for a successful femoral nerve blockade in cats. Further investigations about the clinical usefulness and safety of this femoral nerve block in live cats are required.

Subzygomatic and infraorbital approaches for maxillary nerve blockade in cats’ cadaver

ABSTRACT: This study compared the accuracy of dye placement on the maxillary nerve by using the percutaneous subzigomatic (SBZ) and infraorbitary (IO) approaches in cats’ cadavers. A second aim was to compare the accuracy of dye placement on the maxillary nerve between different untrained anesthetists. This was a prospective, randomized, blinded study, performed in 40 heads obtained from feline cadavers. Three veterinarians (A, B and C) with no previous experience with the IO approach performed the experiments. The SBZ approach was randomly performed on one side of the head and the IO approach was performed in the contralateral side of the same head. For each approach, 0.2ml of 1% methylene blue dye was injected. Scores for length of nerve staining were as follows: 0 (failure), no staining; 1 (moderate), <6mm of nerve stained; and 2 (ideal), ≥6mm of nerve stained. Median scores (interquartile range) for the SBZ and IO approaches were 2.0 (0.3-2.0) and 1.0 (0.0-2.0), respectively. Scores for length of nerve staining were higher with the SBZ approach than the IO approach (P=0.016). Considering the scores for both the SBZ and IO approaches, there was a significant difference among the three veterinarians (P=0.002). Results of this study do not support the IO approach to perform a maxillary nerve block in cats. A greater accuracy of methylene blue dye placement was observed with the SBZ approach. A variable accuracy may exist between different veterinarians when performing a maxillary nerve block employing the SBZ and IO techniques in cats.

Paravertebral brachial plexus blockade in cats: a cadaver study

Objectives The aims of this study were to describe the paravertebral brachial plexus (PBP) blockade in cats, and compare the spread of bupivacaine–methylene blue solution (BMS) using two volumes of injection into the PBP. Methods Six cadavers (4.4 ± 1.8 kg) randomly received 0.15 ml/kg (LOW) or 0.2 ml/kg (HIGH) per injection of BMS into the PBP. The first injection was made ventral to the transverse process of the sixth cervical vertebra (nerves C6 and C7) at the emergence of nerve roots. A second injection was performed at the edge of the cranial border of the scapula and directed ventrally towards the first rib (C8 and T1). Cadavers were dissected and the presence of BMS in contact with the nerves (success rate) and length of staining were evaluated for each nerve (C6/C7/C8/T1). Length of target nerves in contact with BMS was measured and <15 mm was considered fair, ⩾15 mm sufficient and >40 mm excessive. Complications (aspiration of blood, staining of pleural space and/or spinal cord) were recorded. Paired t-test, Mann-Whitney U-test and χ2 test were used for statistical analysis when appropriate ( P <0.05). Results Eleven hemilateral brachial plexuses were injected. Aspiration of blood occurred during one injection. Inadvertent pleural or spinal staining was not observed. Success rates (positive nerve staining) in the LOW and HIGH groups, respectively, were as follows: C6: 83% and 80%; C7: 66% and 100%; C8: 66% and 100%; T1: 50% and 60% ( P >0.05). Median (range) length of nerve staining was 22 mm (15–39 mm) for LOW and 21 mm (13–35 mm) for HIGH ( P >0.05). Excessive nerve staining was not recorded. Conclusions and relevance This study describes the PBP blockade in cats with acceptable nerve staining and minimal complications. Success rate and length of nerve staining were not significantly different between the LOW and HIGH groups.