Aberrant artery within the brachial plexus: Doppler ultrasound as a savior

Abstract

Sir, Anatomical variations of the brachial plexus at the supraclavicular region are quite common, and it is important to identify such abnormalities for a successful block. The use of ultrasound to identify these variations will prevent potential adverse complications and will improve the safety and quality of the block.[1] Herewith, we report the case of an aberrant artery within the brachial plexus and the effective use of color Doppler ultrasound for the identification of the artery. A 28-year-old, male patient, a case of malunited fracture of right both bone forearms was posted for open reduction and internal fixation. Preoperative investigations and vitals were within the normal limits. In the operation theater, after attaching all standard monitors, preprocedural ultrasound was done in two-dimensional mode, and an abnormal structure was noticed within the plexus [Figure 1]. Subsequent color Doppler revealed that it was a blood vessel [Figure 2a] and a spectral Doppler also confirmed that it was an artery, but we could not identify its origin [Figure 2b]. After taking all precautions to treat local anesthetic systemic toxicity, brachial plexus block under ultrasound guidance was performed using linear probe by in-plane technique. Needle was inserted from lateral to medial direction, and the tip was placed above the artery. After confirming negative aspiration, injection bupivacaine 0.5% 10 ml was injected. The needle was then redirected below the artery, and the rest of the local anesthetic was injected (10 ml of injection bupivacaine 0.5%). A successful block was confirmed by the complete anesthesia of the upper limb, and the rest of the intraoperative period remained uneventful. Postprocedure, a scan on the other side (left) did not reveal any such aberrant vessel inside the brachial plexus.Figure 1: Two-dimensional image of brachial plexus in the supraclavicular a b region, with aberrant vessel inside the plexus. BP: Brachial plexus, SA: Subclavian artery, AA: Aberrant artery, ASM: Anterior scalenus muscle, MSM: Middle scalenus muscleFigure 2: (a) Color Doppler image of the brachial plexus with aberrant vessel and (b) Spectral Doppler view of the aberrant artery inside the brachial plexusSupraclavicular brachial plexus block under ultrasound guidance offers added advantages such as better anatomical interpretation, precise needle location, and avoidance of intravascular and intraneural injection.[2] Interpretation requires not only careful anatomical orientation, but also precise image optimization, the recognition of artifact, and the ability to distinguish nerves from the tendons, muscle, and vessels. It is important to note that not all circular hypoechoic structures seen on transverse scanning are nerves. Cadaveric studies have shown that vascular structures can be found within the brachial plexus in around 90% of general population, and the most common vessels include aberrant subclavian artery, dorsal scapular artery, and transverse cervical artery.[3] As these variations can compromise the success and safety of supraclavicular technique, we believe that careful preprocedural scanning, especially using color Doppler, is important to differentiate between vascular structures and nerves. Small noncompressible vessels can mimic proximal nerve roots during gray-scale ultrasound evaluations, making color Doppler imperative when sonographically evaluating the brachial plexus.[4] Hence, in addition to standard gray-scale imaging, color Doppler imaging should be done as a routine before selecting the optimal needle path and location of anesthetic placement, to reduce the possibility of inadvertent vascular injury or intravascular anesthetic deposition. Spectral waveforms obtained with Doppler ultrasonography of small arteries will show triphasic pattern but with a less diastolic flow as seen in our case.[5] Although we could not trace the origin and course of the vessel in our case, appreciation of such vessel within the brachial plexus by Doppler ultrasound enabled us to advance and place the needle tip close to the nerve without puncturing the vessel. Before attempting block in such cases, it is also equally important to take all standard precautions to treat local anesthetic systemic toxicity, as this complication may still occur with the use of ultrasound guidance.[6] Thus, in addition to standard imaging, anesthesiologists should consider preprocedural color Doppler to identify the presence of any abnormal vessel inside the plexus for a safe and successful block. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.