Far lower volumes of local anesthetic: What for?

One of the advantages attributed to the use of ultrasounds in regional anesthesia is the possibility of applying low volumes of local anesthetic. Some studies report the efficient use of extremely low volumes in certain types of blocks. Those results are not easy to extrapolate to general practice because of, among other reasons, the big differences in technical skills among professionals (which are crucial to the ability to reduce the volume used). However, the term “intraneural injection” is currently being redefined based on histology, anatomy, physiology, and on clinical and experimental results. The possibility and advisability of using intraneural-extrafascicular injections to obtain efficient and safe blocks with minimum volumes is now widely studied and debated, as well as the idea that it could be safe in certain selected locations (mainly at the popliteal sciatic level). The purpose of this article is to present the current status of this topic and to share our opinion and elicit debate on the true repercussions and usefulness of a hypothetical reduction of the local anesthetic volumes to their minimum, based on both the reports published and our own clinical experience.