Anatomical basis for ultrasound-guided regional anaesthesia at the junction of the axilla and the upper arm

Double axillary vein variation diagnosed with ultrasound guidance during infraclavicular nerve block intervention

The use of ultrasound guidance increases the safety of peripheral block interventions by allowing anaesthesiologists to simultaneously see the position of block needle, the targeted nerves and surrounding vessels. In this report, we represented three patients diagnosed with double axillary vein variation with ultrasound guidance during infraclavicular nerve block intervention. The patients were scheduled for different types of upper limb surgeries. All patients received infraclavicular nerve block for anaesthetic management. A double axillary vein variation was diagnosed with ultrasound during block interventions. Hydro-location technique was used in all cases and the procedures were completed uneventfully. In the current literature, there is limited number of reports concerning double axillary vein variation. Detailed knowledge of the axillary anatomy is important to avoid complications such as intravascular injection during peripheral nerve block interventions. The use of ultrasound guidance and hydro-location technique should be considered for nerve blocks, especially in the axillary area.

Ultrasound of the Normal Brachial Plexus

Ultrasound (US) allows a reliable examination of the brachial plexus except for the spinal nerve roots, located deep in the neuro-foramina, beyond the shadowing of the transverse processes of the vertebral bodies. All the other fascicles of the brachial plexus can be mapped by US from the roots of the spinal cervical nerves, from C5 to T1 to the branches at level of the axillary region. US can be considered as an alternative to Magnetic Resonance Imaging (MRI) when MRI is contraindicated, not readily available or in case of claustrophobia. US can be used for the assessment of the brachial plexus in case of trauma, tumours and fibrosis induced by radiation oncology treatments. US is also a valuable tool to perform imaging-guided blocks of the brachial plexus. A prerequisite for a reliable US examination of the brachial plexus is knowledge of its complex anatomy. The operator is also required to learn the appropriate US views in order to have an optimal depiction of the brachial plexus, especially the areas where the bone structure's interposition makes the visualisation of the brachial plexus more arduous. The aim of this review is to provide the reader with the basics principles of the US normal anatomy and technique for a reliable mapping of the brachial plexus.

Topographic pattern of the brachial plexus at the axillary fossa through real-time ultrasonography in Koreans

Background

The ability to explore the anatomy has improved our appreciation of the brachial anatomy and the quality of regional anesthesia. Using real-time ultrasonography, we investigated the cross-sectional anatomy of the brachial plexus and of vessels at the axillary fossa in Koreans.

Methods

One hundred and thirty-one patients scheduled to undergo surgery in the region below the elbow were enrolled after giving their informed written consent. Using the 5-12 MHz linear probe of an ultrasound system, we examined cross-sectional images of the brachial plexus in the supine position with the arm abducted by 90°, the shoulder externally rotated, and the forearm flexed by 90° at the axillary fossa. The results of the nerve positions were expressed on a 12-section pie chart and the numbers of arteries and veins were reported.

Results

Applying gentle pressure to prevent vein collapse, the positions of the nerves changed easily and showed a clockwise order around the axillary artery (AA). The most frequent positions were observed in the 10-11 section (79.2%) for the median, 1-2 section (79.3%) for the ulnar, 3-5 section (78.4%) for the radial, and 8-9 section (86.9%) for the musculocutaneous nerve. We also noted anatomical variations consisting of double arteries (9.2%) and multiple axillary veins (87%).

Conclusions

Using real-time ultrasonography, we found that the anatomical pattern of the major nerves in Koreans was about 80% of the frequent position of individual nerves, 90.8% of the single AA, and 87% of multiple veins around the AA.

[Ultrasound-guided axillary block: anatomical variations of terminal branches of the brachial plexus in relation to the brachial artery]

OBJECTIVES

To describe the distribution of the terminal branches of the brachial plexus at the axillary level and define distribution patterns after ultrasound evaluation.

MATERIAL AND METHOD

Fifty volunteers underwent ultrasound bilateral axillary brachial plexus scanning exploration. Nerve distribution around the humeral artery was described and the distance between each nerve and the center of the artery was measured. The distance and relationship between the ulnar nerve and the humeral vein were also recorded.

RESULTS

The median nerve was located in the anterolateral quadrant (-29±40°) and at a mean distance of 2.1±0.9mm from the artery (85%). The ulnar nerve was found at 53±26° and at 4.2±2.1mm from the artery in the anteromedial quadrant (90%), anterolateral to the vein in 46% of cases, and deep to it in 54%. The radial nerve was at 122±38° and at 3.3±1.7mm from the artery in the posteromedial quadrant (86%). The musculocutaneous nerve was found at -103±22° and 9.3±5.6mm from the artery in the posterolateral quadrant (90%) and in the anterolateral quadrant (-55±16°) at 4.8±2.7mm (10%). There were no differences regarding laterality, gender or overweight patients.

CONCLUSIONS

Our results allow defining four different anatomical patterns, two based in the position of the musculocutaneous nerve and two based on the disposition of the ulnar nerve with respect to the humeral vein. These patterns were not related to laterality, gender or body weight.