BACKGROUND AND OBJECTIVES: Ultrasound-guided nerve blocks are based on the direct visualization of nerve structures, needle, and adjacent anatomic structures. Thus, it is possible to place the local anesthetic precisely around the nerves and follow its dispersion in real time, obtaining, therefore, more effective blockades, reduced dependency on anatomic references, decreased anesthetic volume, and increased safety. CONTENTS: The aim of this paper was to review the physical mechanisms of image formation, ultrasound anatomy of the neuro axis and of the brachial and lumbosacral plexuses, equipment and materials used in the blockades, settings of the ultrasound equipment to improve the image, planes of visualization of the needles, the techniques, and training in ultrasound-guided nerve blocks. CONCLUSIONS: The steps for a successful regional block include the identification of the exact position of the nerves, the precise localization of the needle, without causing injuries to adjacent structures, and, finally, the careful administration of the local anesthetic close to the nerves. Although neurostimulation is very useful in identifying nerves, it does not fulfill all those requirements. Therefore, it is believed that ultrasound-guided nerve blocks will be the technique of choice in regional anesthesia in a not too distant future.
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