Prospective randomized comparison between ultrasound-guided saphenous nerve block within and distal to the adductor canal with low volume of local anesthetic

Background and Aims: The anatomic site and the volume of local anesthetic needed for an ultrasound-guided saphenous nerve block differ in the literature. The purpose of this study was to examine the effect of two different ultrasound-guided low volume injections of local anesthetic on saphenous and vastus medialis nerves. Materials and Methods: Recruited patients (N = 48) scheduled for orthopedic surgery were randomized in two groups; Group distal adductor canal (DAC): Ultrasound-guided injection (5 ml of local anesthetic) distal to the inferior foramina of the adductor canal. Group adductor canal (AC): Ultrasound-guided injection (5 ml local anesthetic) within the adductor canal. Following the injection of local anesthetic, block progression was monitored in 5 min intervals for 15 min in the sartorial branches of the saphenous nerve and vastus medialis nerve. Results: Twenty two patients in each group completed the study. Complete block of the saphenous nerve was observed in 55% and 59% in Group AC and DAC, respectively (P = 0.88). The proportion of patients with vastus medialis weakness at 15 min in Group AC, 36%, was significantly higher than in Group DAC (0/22), (P = 0.021). Conclusions: Low volume of local anesthetic injected within the adductor canal or distally its inferior foramina leads to moderate success rate of the saphenous nerve block, while only the injection within the adductor canal may result in vastus medialis nerve motor block

Ultrasound anatomy of the cervical paravertebral space: A preliminary study

Purpose: The aim of the study was to examine the ultrasound anatomy of the cervical paravertebral space in order to facilitate the implementation of sonographically guided regional anesthesia techniques for this region. Methods: Twenty volunteers were recruited, and the anatomic components of the cervical paravertebral space were sonographically examined. The transducer was positioned in the axial and coronal plane at the posterior cervical triangle. The cervical transverse processes with their respective nerve roots, the deep cervical fascia and the paravertebral muscles were identified. Results: There was excellent visualization of the C-3, C-4, C-5, C-6 and C-7 transverse processes in all cases. Excellent visualization of the scalene muscles, vertebral artery and deep cervical fascia was also achieved in all cases. Visualization of the levator of scapula muscle was difficult in 9 and excellent in 11 out of the 20 cases. In all cases, visualization of the C-1, C-2 and C-3 nerve roots was unfeasible. The identification of the C-4 nerve root was excellent in 3, difficult in 6 and unfeasible in 11 out of the 20 cases. The C-5, C-6 and C-7 nerve roots were excellently identified in all cases. The C-8 nerve root was identified only in 8 of the 20 cases. The cervical nerve roots also showed high variation, dividing into more than one branch as they exited the cervical transverse processes. Conclusion: Cervical paravertebral anatomy can be depicted with ultrasound imaging techniques. This could be highly clinically significant for the implementation of regional anesthesia techniques. © 2010 Springer-Verlag

Anatomic variations of the obturator nerve in the inguinal region: Implications in conventional and ultrasound regional anesthesia techniques

Background and Objectives: This study was conducted to provide a thorough description of the variability in the obturator nerve branching pattern in the inguinal region. Methods: The anatomic variability of obturator nerve branching among 84 dissected embalmed cadavers was investigated. Ultrasound examination of the inguinal region was undertaken in 20 cases and the location of the obturator nerve was identified. Results: The point of division for the obturator nerve into the anterior and posterior branches was intrapelvic (23.22%), within the obturator canal (51.78%), or in the thigh (25%). Most commonly, the anterior branch was divided among 3 major muscular branches (66.66%) that innervated the adductor longus, adductor brevis, and gracilis muscles. Four, and 2 subdivisions of the anterior branches were observed, in 4.76% and 28.57% of cases, respectively. The posterior branch predominantly separated into 2 divisions (60.11%), which provided innervation to the adductor brevis and adductor magnus muscles. In addition, either 1 (13.69%), 3 (19.04%), or 4 (7.14%) muscular divisions of the posterior branch were observed. The articular branch of the obturator nerve showed 9 different branching patterns, which most frequently arose from the common obturator nerve. The fascias medial to the femoral vessels and deep to the pectineus muscle were clearly visualized (100%) by ultrasound imaging. This region was used as an "imaging" landmark for localization (success rate of 80%) of the common obturator nerve. Conclusions: High anatomic variability in the obturator nerve's divisions and subdivisions does exist, and explains the difficulty frequently encountered in the application of regional anesthetic techniques. Copyright © 2009 by American Society of Regional Anesthesia and Pain Medicine

Thoracic paravertebral spread using two different ultrasound-guided intercostal injection techniques in human cadavers

The continuity between the intercostal and paravertebral space has been established by several studies. In this study, the paravertebral spread of a colored dye was attempted with two different ultrasound-guided techniques. The posterior area of the trunk was scanned with a linear probe between the level of the fifth and the seventh thoracic vertebrae in eleven embalmed human cadavers. In the first technique, the probe was placed transversely below the inferior margin of the rib, and a needle was inserted between the internal intercostal membrane and the pleura. In the second technique, the probe was placed longitudinally at the intercostal space 5 cm lateral to the spinous processes, and the needle was inserted between the internal intercostal membrane and the pleura. In both techniques, 1 ml of methylene blue was injected, and both the intercostal and paravertebral spaces were prepared. In total, 33 injections were performed: 19 with the transverse technique and 14 with the longitudinal technique. Successful spread of the dye to the thoracic paravertebral space was recorded in 89.5% cases using the transverse technique and 92.8% cases using the longitudinal technique. No intrapleural spread of the dye was recorded in either technique. Ultrasound-guided injection into the intercostal space may offer an alternative approach to the thoracic paravertebral space. © 2010 Wiley-Liss, Inc