New paraspinal blocks: a narrative review

The neuraxial approach has long been used as a sole anesthetic technique, as well as as part of multimodal postoperative analgesic management. In this context, epidural anesthesia and later paravertebral anesthesia became alternative techniques for providing analgesia in thoracoabdominal surgeries. However, both techniques have been associated with complications that limit their use in all cases. With the support of ultrasound and the constant search for safer and more reproducible techniques, multiple alternative blocks to the thoracic paravertebral block have been described in the last decade. Although these regional techniques are based on an anatomical foundation, the evidence in cadaveric studies of consistent diffusion into the paravertebral space has not been resolved. We review the origin, techniques, and approaches of these new paraspinal blocks and group them based on the evidence found against paravertebral block, no block, or erector spinae plane block. Regarding clinical evidence, the heterogeneity of both study models and described blocks hinders adequate interpretation of published works. Also, the limited evidence from publications comparing them with a gold standard shared by the anesthesiology community (epidural anesthesia, paravertebral block, or adequate multimodal systemic management). However, it is expected that after the latest DELPHI consensus, where several of these regional blocks were grouped as a single block, clearer evidence may emerge on the usefulness of these paraspinal blocks in certain scenarios.