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The duration of the surgical procedure, patient comorbidities, and postoperative factors, such as the early need for the use of the operative extremity and potential for significant postoperative discomfort, should all be used to determine the selection of local anesthetic and technique.
The lowest clinically effective dose of a local anesthetic should be used whenever possible to minimize toxicity.
Studies to date have shown that ultrasound decreases the time for placement of peripheral nerve blocks, increases the speed of block set-up, and improves the "quality" of the block by modest amounts when compared with the traditional landmark techniques or nerve stimulation.
Because the frequency of neurologic injury is low with peripheral nerve blocks, no single technique has been shown to be "safer" than another.
The use of ultrasound does not replace the need for a fundamental understanding of anatomy when placing peripheral nerve blocks.
The interscalene approach to the brachial plexus, unlike the supraclavicular approach, will most likely miss the ulnar distribution of the hand; thus it is not suitable as a complete anesthetic distal to the elbow.
Femoral nerve block is a relatively easy block to perform and its success rate is high. A femoral nerve block is usually performed in conjunction with other lower-extremity blocks.
The popliteal approach to the sciatic nerve can be done with the patient supine or prone and is ideal for surgeries involving the lower leg and/or foot. If the medial aspect of the lower leg or foot is required for surgical anesthesia, then the saphenous portion of the femoral nerve must be included.
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Peripheral nerve blocks are a powerful component of the practice of anesthesia. No other anesthetic technique allows a precise targeting of anesthetic to the surgical site while sparing non–procedure-involved locations. This not only allows one to create tailored area of surgical anesthesia, but also to avoid, or reduce, the risk of systemic complications from general anesthesia such as nausea and vomiting.1,2 To perform a peripheral nerve block, one must have a local anesthetic, a means to administer the anesthetic, and a target nerve structure.
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The modern knowledge of anatomy can be traced to the Renaissance, when scholars once again began using cadavers to teach their students anatomy after the Church banned cadaveric dissection during the Middle Ages. It was the "reawakening" of such scholars as Andreas Vesalius and the publication of his De Humani Corporis Fabrica (On the Structure of the Human Body) that shaped the modern day study of anatomy.3 However, the mapping of dermatomes and the understanding of peripheral nerve anatomy would not begin until the late 1800s. The combination of the observations of French neurologist Jean Martin Charcot and the American scholar Silas Weir Mitchell would begin to suggest the need for "cutaneous nerve mapping."4 Mitchell especially seemed to be a keen observer and was interested in peripheral nerve anatomy as he cared for injured veterans from the American Civil War.4...