Chan, Vincent W. S. MD*; Perlas, Anahi MD*; Rawson, Regan RN†; Odukoya, Olusegun MD†
*Department of Anesthesia, University of Toronto; and
†Department of Anesthesia, Toronto Western Hospital, Toronto, Ontario, Canada
Supported by Toshiba of Canada, Ltd., Medical Systems and Philips Medical Systems (for the loan of ultrasound equipment).
Accepted for publication January 31, 2003.
Address correspondence and reprint requests to Vincent Chan, MD, Department of Anesthesia, Toronto Western Hospital, University Health Network, 399 Bathurst St., Toronto, Ontario, Canada M5T 2S8. Address e-mail to email@example.com.
Successful brachial plexus blocks rely on proper techniques of nerve localization, needle placement, and local anesthetic injection. Standard approaches used today, unfortunately, are all “blind” techniques (1–3) that rely on surface landmarks before needle insertion and elicitation of paresthesia or nerve-stimulated muscle contraction after needle insertion. Often, multiple trial-and-error needle attempts are necessary, resulting in procedure-related pain and complications (4). This is risky, particularly for the supraclavicular approach, because of the chance of pneumothorax (1).
Ultrasound guidance for brachial plexus blocks can potentially improve success and complication rates (5–8). We hypothesized that ultrasound imaging can help localize the brachial plexus accurately and guide needle advancement to the target nerves. This study examines the technique and clinical usefulness of state-of-the-art ultrasound technology for supraclavicular brachial plexus blocks.
After hospital ethics committee approval and written, informed consent, 40 healthy outpatients received ultrasound-guided supraclavicular brachial plexus blocks for elective upper-limb surgery. Excluded were patients with neurological deficit in the upper limb or contraindications to have supraclavicular brachial plexus blocks.
For the first 29 patients, a Toshiba Core Vision Pro unit (Toshiba Corp., Tokyo, Japan) equipped with a linear 8-MHz probe was used. For the remaining 11 patients, a Philips ATL HDI 5000 SonoCT unit (Philips Medical Systems, Bothell, WA) equipped with a linear 5- to 12-MHz probe, color Doppler, and compound imaging capability was used.
The brachial plexus and its spatial relationship to surrounding structures were scanned after the patients received IV access and routine anesthesia monitoring. With the patient lying supine and the head turned 45° to the contralateral side, the ultrasound probe was placed in the coronal oblique plane in the supraclavicular fossa to visualize the subclavian artery and brachial plexus in the transverse sectional view (i.e., at approximately 90°;Fig. 1). The brachial plexus, a cluster of hypoechoic nodules, was often found lateral to the round pulsating hypoechoic subclavian artery lying on top of the hyperechoic first rib (Fig. 1).
Next, after skin sterilization and anesthesia, a 22-gauge 50-mm insulated block needle (Stimuplex; Braun Medical) was placed on the outer (lateral) end of the probe (now inside a sterile cover) and advanced along the long axis of the probe and in the same plane as the ultrasound beam (Fig. 2). Needle movement was observed in real time. Once the needle reached the brachial plexus cluster (Fig. 3), a nerve stimulator (Stimuplex) was turned on, starting from 0.5 mA and increasing up to 1.5 mA (maximum) to elicit muscle twitch. The minimum stimulating current, the site of muscle twitch, and the presence of paresthesia were checked and recorded. Thereafter, 20 mL of lidocaine 2% containing 1:200,000 epinephrine and 20 mL of bupivacaine 0.5% were injected incrementally over 3–5 min. Local anesthetic spread at the time of injection was observed in real time. If spread did not reach some parts of the brachial plexus, the needle was repositioned once before depositing the remaining half of the local anesthetic dose.
Pinprick anesthesia to a 23-gauge needle and motor block were checked by an independent observer every 5 min for 30 min in the median, ulnar, radial, and musculocutaneous nerve locations. A successful block was defined as complete sensory and motor block in all regions assessed within 30 min of local anesthetic injection. Anesthetic failure in the surgical area was supplemented with local anesthetic infiltration or general anesthesia if necessary.
Also monitored were the time required for block performance (the time elapsed from probe positioning to the end of local anesthetic injection), the number of needle attempts, the pattern of local anesthetic spread, postblock complications, visual analog pain scores in the postanesthesia care unit (PACU), and patient satisfaction. Continuous data are expressed as mean ± sd.
Forty patients (26 men and 14 women, 45 ± 15 yr old, 170 ± 11 cm, 77 ± 15 kg, with a body mass index of 26 ± 5 kg/m2) completed the study. Surgical time was 77.9 ± 40.4 min for 2 forearm, 9 wrist, and 29 hand and finger procedures. Ultrasound showed in all cases the transverse view of the brachial plexus as hypoechoic nodules in clusters of varying size, consistently lateral, posterior, and often cephalad to the subclavian artery.
Blocks performed by 5 anesthesiologists (1 staff, 1 fellow, and 3 residents) were successful in 95% (38 of 40) of the cases. The block procedure took 9.0 ± 4.4 min after 1 attempt (median; range, 1–2), even though only 2 investigators had prior ultrasound experience (≤5 cases). Contraction was elicited by a stimulating current of 0.46 mA (range, 0.2–0.7 mA) in one or more muscle groups, corresponding to stimulation of the radial, median, musculocutaneous, and ulnar nerves in 55%, 30%, 10%, and 8%, respectively. Sensory and motor block appeared within 5.4 ± 1.8 min, was completed within 16.7 ± 5.5 min, and resolved in 11.4 ± 4.2 h. Postoperative PACU pain scores were low (mean, <0.3 of 10), and patient satisfaction with pain control was high (median, 9 out of 10).
One failure was attributed to subcutaneous injection that we failed to recognize despite an unusual spread pattern observed on ultrasound at the time of injection. The second failure, an incomplete block at 30 min, was attributable to partial intravascular local anesthetic injection but was subsequently found to be complete at the end of surgery. Postoperative complications included one case of Horner’s syndrome and one transient paresthesia (<48 h), but no pneumothorax.
Our preliminary results suggest that ultrasound guidance for supraclavicular brachial plexus block is clinically useful for accurate nerve localization and to minimize the number of needle attempts. Nerve localization was confirmed by two methods in this study: ultrasound and electrical stimulation. Whether ultrasound alone can offer the same success deserves further study. Unlike estimates by conventional techniques, ultrasound can determine the size, depth, and exact location of the brachial plexus and its neighboring structures. Preblock anatomical examination can define the optimal site and depth of needle insertion, avoid vascular and pleural puncture, and impart confidence to anesthesiologists performing the block.
Real-time ultrasound imaging can help guide the block needle to reach target nerves with fewer attempts. Under visual guidance, needle movement is purposeful and based on constant image feedback, thus avoiding nerve localization by trial and error. Our technique of needle insertion is unique and drastically different from those conventionally taught. With one hand holding the probe, the other advances the block needle from the outer end of the probe in a lateral to medial direction (Fig. 2), for two main reasons. First, when positioned in the supraclavicular fossa, the probe leaves limited space on the medial side for needle maneuvering. Second, the brachial plexus is situated lateral to the subclavian artery; thus, the lateral approach is most logical and direct. Although Kapral et al. (5) and Yang et al. (6) both reported block success with ultrasound guidance, the technique of needle placement was not disclosed. Furthermore, the brachial plexus was scanned in the sagittal (longitudinal) plane as opposed to the coronal oblique (transverse) plane in this study.
Real-time observation of needle movement is an important feature of the ultrasound technique we describe. The needle is advanced intentionally in the same plane as the ultrasound beam, i.e., along the along axis of the probe, where the linear array of ultrasound crystals is situated. With proper needle-probe alignment, movement of the needle shaft and tip (a hyperechoic line seen in Fig. 3) can be tracked continuously during the block procedure. When the needle does not trespass the first rib or pleura on ultrasound, the risk of pneumothorax is virtually eliminated. However, without proper alignment, the needle tip cannot be fully visualized, and penetration can be deeper than anticipated, as with the case of unrecognized subclavian artery puncture in this study.
Ultrasound imaging shows nerves as mobile structures that move away from the needle or local anesthetic injection. Two patterns of local anesthetic spread have been observed. In the first pattern, bolus injection within the nerve cluster pushes the nerves to the periphery, suggesting circumferential spread (Fig. 4). Expansion of the nerve-containing compartment is lined by a hyperechoic perimeter, possibly representative of the plexus sheath. In the second, spread is asymmetrical, with local anesthetic in contact with only some part of the nerve cluster without the apparent sheath (Fig. 5). When this happens, we intentionally make a second injection, but it is unclear whether double injection is necessary to guarantee complete anesthesia.
In summary, we found that ultrasound guidance is clinically useful for supraclavicular brachial plexus block. It confers confidence and accuracy of needle placement for nerve localization and examines the pattern of local anesthetic spread.
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