 PAIN AND REGIONAL ANESTHESIA Anesthesiology 2003; 99:429 –35 © 2003 American Society of Anesthesiologists, Inc. Lippincott Williams & Wilkins, Inc. Brachial Plexus Examination and Localization Using Ultrasound and Electrical Stimulation A Volunteer Study Anahi Perlas, M.D.,* Vincent W. S. Chan, M.D.,† Martin Simons, M.D.‡ Background: Current techniques of brachial plexus block are “blind,” and nerve localization can be frustrating and time con- suming. Previous studies on ultrasound-assisted brachial plexus blocks are mostly performed with scanning probes of 10 MHz or less. The authors tested the usefulness of a state-of-the-art, high-resolution ultrasound probe (up to 12 MHz) in identifying the brachial plexus in five locations of the upper extremity and in guiding needle advancement to target before nerve stimulation. Methods: In this prospective observational study, 15 volun- teers underwent brachial plexus examination using an L12–L5 MHz probe and a Philips-ATL 5000 ultrasound unit in the inter- scalene, supraclavicular, infraclavicular, axillary, and midhumeral regions. Thereafter, an insulated block needle was advanced under direct ultrasound guidance to target nerves before confirmation by electrical nerve stimulation in five vol- unteers in each of the interscalene, supraclavicular, and axil- lary regions. The quality of brachial plexus images, anatomic variations, and the technique of needle advancement for nerve localization were recorded. Results: The brachial plexus components were successfully identified in the transverse view as round to oval hypoechoic structures with small internal punctuate echos in all regions examined except the infraclavicular area (visualized in 27% of the cases). The authors’ technique of advancing the needle in-line with the ultrasound beam allowed moment-by-moment observation of the needle shaft and tip movement at the time of nerve localization. Hypoechoic structures were stimulated elec- trically and confirmed to be nerves. Conclusions: These preliminary data show that the high-res- olution L12–L5 probe provides good quality brachial plexus ultrasound images in the superficial locations i.e., the inter- scalene, supraclavicular, axillary, and midhumeral regions. The needle technique described here for ultrasound-assisted nerve localization provides real-time guidance and is potentially valu- able for brachial plexus blocks. BRACHIAL plexus block is indicated for upper extremity surgery, and many techniques are available. The key to success depends on the accuracy of needle placement, nerve localization, and local anesthetic injection. Cur- rent techniques of nerve localization rely on surface anatomic landmarks for estimating brachial plexus loca- tion. However, at the time of needle insertion, the search for target nerves remains “blind”; thus, nerve localization can be frustrating and time consuming. Most often, block failures result from imprecise needle placement, and even in experienced hands, the failure rate can be as high as 10 –15%. 1 Blind techniques can also cause complications, patient discomfort, and long procedure times. Although infre- quent, direct or indirect needle injury may cause serious complications such as nerve damage, 2 spinal cord injury (with interscalene block 3 ), pneumothorax (with the su- praclavicular approach 4 ), vascular puncture, 5 and sys- temic local anesthetic toxic reactions. 6 Complications aside, the trial-and-error approach to nerve localization often requires multiple needle attempts, leading to pa- tient anxiety and operating room delay. In recent years, there has been growing interest in the development of image-guided brachial plexus blocks. Both magnetic resonance imaging 7 and computed tomo- graphic scanning 8 provide excellent anatomic images of the brachial plexus, but they are expensive and inacces- sible to the operating room. Fluoroscopy is another option, 9,10 but its usefulness is limited to visualization of bony landmarks and contrast dye spread near to the neurovascular bundle within the plexus sheath. Ultra- sound, on the other hand, is noninvasive, portable, and moderately priced. This real-time imaging technology can aid in brachial plexus blocks in the interscalene, 11 supraclavicular, 12 and infraclavicular regions. 13–15 Most previous ultra- sound studies examining brachial plexus anatomy used scanning probes with frequency in the range of 5–10 MHz. Advanced ultrasound technology today offers high- resolution probe (12–15 MHz) and compound imaging. Such new image-enhancing capability allows clear visu- alization of nerves and can potentially improve the tech- nique of ultrasound-assisted brachial plexus block. The purposes of the current study are to evaluate the usefulness of a state-of-the-art, high-resolution ultrasound probe in identifying the brachial plexus and evaluate the This article is accompanied by an Editorial View. Please see: Greher M, Kapral S: Is Regional Anesthesia Simply an Exercise in Applied Sonoanatomy? Aiming at Higher Frequencies of Ultrasonographic Imaging ANESTHESIOLOGY 2003; 99:250 –1.  * Resident, † Associate Professor, Department of Anesthesia, ‡ Assistant Pro- fessor, Department of Medical Imaging. Received from the Departments of Anesthesia and Medical Imaging, Toronto Western Hospital, University Health Network, University of Toronto, Toronto, Ontario, Canada. Submitted for publication October 10, 2002. Accepted for publication February 7, 2003. Study equipment support was provided from institutional sources and Philips Medical Systems ATL Ultrasound, Bothell, Wash- ington. Study funding was provided solely from departmental sources. Address reprint requests to Dr. Chan: Department of Anesthesia, Toronto Western Hospital, University Health Network, 399 Bathurst Street, Toronto, Ontario, Canada M5T 2S8. Address electronic mail to: vincent.chan@uhn.on.ca. Individual article reprints may be purchased through the Journal Web site, www.anesthesiology.org. Anesthesiology, V 99, No 2, Aug 2003 429 Downloaded from http://pubs.asahq.org/anesthesiology/article-pdf/99/2/429/408800/0000542-200308000-00025.pdf by guest on 05 November 2021