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INTRODUCTION

Regional nerve and plexus blocks have been integral to the practice of anesthesiology for over 60 years and are commonly used for hand, arm, hip, knee, and foot surgery. Initially, training in regional anesthesia relied on identification of anatomic landmarks and the perception of various clicks and pops as fascial planes were traversed by a blunt-tipped needle. Several decades later, nerve stimulators were incorporated into the block procedure to assist with more precise placement of the anesthetic delivery needle as close to the target nerve or nerve plexus as possible. The success of these regional anesthetic blocks was highly operator dependent, however, and even with the use of a nerve stimulator in skilled hands, block failure rates of 10–30% were not uncommon, depending on the site of the block.1,2

Over the past 15–20 years, an emerging body of anesthesiology and emergency medicine literature has demonstrated the important role ultrasound can play in enhancing the performance characteristics and success rates of various regional blocks.1−11 The development of more portable ultrasound equipment, higher resolution and smaller footprint transducers, and improved picture-processing technology, such as compound imaging and enhanced needle recognition software, have all helped accelerate this process. Not surprisingly, the utilization of ultrasound for performance of regional anesthetic blocks is gradually becoming the new standard. For the commonly performed nerve blocks, ultrasound imaging allows for real-time visualization of the target nerve in most patients. With sonographic guidance, the operator can guide the anesthetic delivery needle under direct visualization and deposit the local anesthetic agent in a very precise fashion, with a lower dosing volume. This enhances all of the desirable operating characteristics of the procedure and minimizes complications.

CLINICAL CONSIDERATIONS

In a series of 40 patients undergoing forearm or hand surgery, one study reported an ultrasound-guided brachial plexus block success rate of 95% at both the supraclavicular and axillary sites with no reported complications; this compares with an historical 70–80% success rate at these sites using a nerve stimulator. More importantly, the ultrasound-guided supraclavicular brachial plexus block provided the additional advantage of reliable anesthesia of the musculocutaneous nerve with a minimal risk of associated complications such as pneumothorax.8

In a study of 40 patients with hip fractures receiving a femoral nerve block for analgesia prior to surgery, the onset of femoral nerve sensory blockade was noted to be significantly faster in the ultrasound group (16 minutes) compared with the nerve stimulator group (27 minutes), and overall block success improved from 85% in the nerve stimulator group to 95% with ultrasound guidance.9 In a subsequent study, 60 patients with hip fractures were randomized to receive a femoral nerve block guided by either ultrasound or nerve stimulator. The ultrasound group had a higher procedural success rate (95% with ultrasound compared with 80% with the nerve stimulator technique), an improved onset time (of sensory loss), and a smaller ...

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