Failure of supraclavicular block under ultrasound guidance: clinical relevance of anatomical variation of cervical vessels

Origin variations and brachial plexus relationship of the dorsal scapular artery

The dorsal scapular artery can either be a direct branch of the subclavian artery or a branch of the transverse cervical artery. Origin variation is related to its relationship with the brachial plexus. Anatomical dissection was performed on 79 sides of 41 formalin-embalmed cadavers in Taiwan. The origin of the dorsal scapular artery and the variations of its brachial plexus relationship were scrutinized and analyzed. Results showed that the dorsal scapular artery originated most frequently from the transverse cervical artery (48%), followed by the direct branch from the third part (25%) and the second part (22%) of the subclavian artery and from the axillary artery (5%). Only 3% of the dorsal scapular artery passed through the brachial plexus if its origin was the transverse cervical artery. However, 100% and 75% of the dorsal scapular artery passed through the brachial plexus when they were direct branches of the second and the third part of the subclavian artery, respectively. Suprascapular arteries were also found to pass through the brachial plexus when they were direct branches from the subclavian artery, but all passed over or under the brachial plexus if they originated from the thyrocervical trunk or transverse cervical artery. Variations in the origin and course of arteries around the brachial plexus are of immense value not only to the basic anatomical knowledge but also to clinical practices such as supraclavicular brachial plexus block and head and neck reconstruction with pedicled or free flaps.

Integrating a Cadaver Review Session into the Existing Regional Anesthesia Training for Anesthesiology Residents: An Initial Experience

The Department of Anesthesiology's Acute Pain Service (APS) places ultrasound-guided peripheral nerve blocks (PNBs) to manage acute peri-operative pain. PNB success is dependent on detailed anatomical knowledge which residents may not have formally reviewed since medical school. This study describes the integration of a cadaver review session (CRS) that reintroduces PNB-related anatomy into the existing APS rotation. During each CRS, an anatomist reviewed the major nerve and surrounding structures, while an APS attending integrated the anatomy with PNB techniques. During the pilot, 1st- and 3rd-year clinical anesthesia (CA) residents (9 CA1s, 7 CA3s) completed pre- and post-session surveys and rated the CRS's perceived value and impact on self-confidence with anatomical knowledge. Following the pilot, an additional 17 CA1s and 9 CA3s participated in the CRS and completed post-session surveys. Descriptive statistics were used to summarize responses and unpaired t tests were used to compare pre- and post-session responses and responses between cohorts. All participants were overwhelmingly positive about the CRS and its value to the APS rotation, with 98% agreeing they recommend the CRS and found it accessible. Residents believed participation would improve board exam (average = 4.83 ± 0.66) and clinical performance (average = 4.86 ± 0.65), and self-reported increases in confidence with anatomical knowledge. Residents in the pilot group reported significantly greater confidence (p < 0.01) in their perceived anatomical knowledge after the CRS. The CRS positively impacted resident confidence in their anatomical knowledge and perceived ability to identify anatomical structures. Residents reported the CRS was a highly valued addition to regional anesthesia training.

Dorsal Scapular Artery Variations and Relationship to the Brachial Plexus, and a Related Thoracic Outlet Syndrome Case

Rationale Knowledge of the relationship of the dorsal scapular artery (DSA) with the brachial plexus is limited. Objective We report a case of a variant DSA path, and revisit DSA origins and under-investigated relationship with the plexus in cadavers. Methods The DSA was examined in a male patient and 106 cadavers. Results In the case, we observed an unusual DSA compressing the lower plexus trunk, that resulted in intermittent radiating pain and paresthesia. In the cadavers, the DSA originated most commonly from the subclavian artery (71%), with 35% from the thyrocervical trunk. Nine sides of eight cadavers (seven females) had two DSA branches per side, with one branch from each origin. The most typical DSA path was a subclavian artery origin before passing between upper and middle brachial plexus trunks (40% of DSAs), versus between middle and lower trunks (23%), or inferior (4%) or superior to the plexus (1%). Following a thyrocervical trunk origin, the DSA passed most frequently superior to the plexus (23%), versus between middle and lower trunks (6%) or upper and middle trunks (4%). Bilateral symmetry in origin and path through the brachial plexus was observed in 13 of 35 females (37%) and 6 of 17 males (35%), with the most common bilateral finding of a subclavian artery origin and a path between upper and middle trunks (17%). Conclusion Variability in the relationship between DSA and trunks of the brachial plexus has surgical and clinical implications, such as diagnosis of thoracic outlet syndrome.

Lack of Sex Difference in Minimum Local Analgesic Concentration of Ropivacaine for Ultrasound-Guided Supraclavicular Brachial Plexus Block

Background

Sex differences, which may be an important variable for determining anesthetic requirements, have not been well investigated in the aspect of local anesthetic. This investigation aimed to compare the minimum local analgesic concentration (MLAC) of ropivacaine for ultrasound-guided supraclavicular brachial plexus block (US-SCB) between men and women.

Material/Method

Patients aged 18–45 years undergoing elective forearm, wrist, or hand surgeries under US-SCB were divided into 2 groups according to sex. The initial concentration was 0.375% ropivacaine 20 mL and the concentration for the next patient was determined by the up-down technique at 0.025% intervals. Success was defined as the absence of any pain in response to a pinprick in the region of all 4 terminal nerves and the skin incision within 45 min. The primary outcome was the MLAC of ropivacaine, which was estimated by the Dixon and Massey method. The analgesia duration, which was defined as the time from the end of the US-SCB injection to the time of feeling discomfort and need for additional analgesics, was observed for each patient.

Results

The MLAC of ropivacaine 20 mL for US-SCB was 0.2675% (95% confidence interval [CI], 0.2512–0.2838%) in men and 0.2675% (95% CI, 0.2524–0.2826%) in women. There was no significant difference in MLAC or the analgesia duration between the 2 groups (P>0.05).

Conclusions

We found no significant sex-related differences in MLAC or analgesia duration of ropivacaine for US-SCB.

Anatomic variation of subclavian artery visualized on ultrasound-guided supraclavicular brachial plexus block

Use of ultrasonography for performance of nerve and plexus blocks has made the process simpler and safer. However, at times, variant anatomy of the visualized structures can lead to failure of blocks or complications such as intravascular injections. This is especially true in case of novice operators. We report a case of a variant branch of subclavian artery, possibly the dorsal scapular artery passing through the brachial plexus nerve bundles in the supraclavicular area. Since this variation in anatomy was visualized in the scout scan prior to the performance of the block, it was possible to avoid any accidental puncture. Hence, a thorough knowledge of the ultrasound anatomy is important in order to identify various aberrations and variations. It is also prudent to perform a preliminary scan, prior to performance of the block to localize the target area and avoid any inadvertent complications.

Ultrasound-guided supraclavicular brachial plexus block in upper limb surgery

We examined the outcomes and levels of patient satisfaction in 202 consecutive cases of ultrasound-guided supraclavicular brachial plexus block (SBPB) in upper limb surgery performed between September 2007 and March 2010.

All blocks were performed by orthopaedic surgeons using ultrasound visualisation with a high-frequency linear probe. The probe was placed in the coronal–oblique plane in the supraclavicular fossa, and the puncture was ‘in-plane’ from lateral to medial. Most of the blocks were performed with 0.75% ropivacaine/1% lidocaine (1:1), with or without adrenaline in 1:200 000 dilution. In 201 patients (99.5%) the brachial plexus block permitted surgery without conversion to general anaesthesia. The mean procedure time for block was 3.9 min (2 to 12), the mean waiting time for surgery was 34.1 min (10 to 64), the mean surgical time was 75.2 min (6 to 232), and the mean duration of post-anaesthetic analgesia was 437 min (171 to 992). A total of 20 patients (10%) developed a transient Horner’s syndrome. No nerve injury, pneumothorax, arterial puncture or systemic anaesthetic toxicity were recorded. Most patients (96.7%) were satisfied with ultrasound-guided SBPB. This study demonstrates the efficacy and safety of ultrasound-guided SBPB for orthopaedic surgery on the upper limb.

Cite this article: Bone Joint J 2014;96-B:795–9.

Origin of the dorsal scapular artery and its relation to the brachial plexus in Thais

We investigated the variations of the origin of the dorsal scapular artery (DSA) and its relation to the brachial plexus in 252 sides of the posterior cervical triangles of Thais. The origin of this artery on each part of the subclavian artery or other arterial branches was examined with special reference to their course in relation to the brachial plexus. The results show that the DSA originated from three sites; most commonly from the transverse cervical artery (69%) followed by the direct branching from the second (2.8%) or the third part (28.2%) of the subclavian artery. When the DSA was branched from the transverse cervical artery, its course was always posterior or above the brachial plexus. When the DSA arose from the second or the third part of the subclavian artery, it always ran in the branches of the brachial plexus in various sites. The most frequent course was to pass between the upper and middle trunks of the brachial plexus (63.2%). Other courses were far less frequent and found to pass between the anterior division of the upper trunk and the middle trunk of brachial plexus or between the roots of C8 and T1 with the frequency of 1.3 and 2.6%, respectively.