Spread of local anesthetic during erector spinae plane block

• The purple shading shows posterior spread, between the erector spinae muscle and the transverse process. This is the most common, extensive, and reliable area of spread of local anesthetic. It anesthetizes the dorsal rami of spinal nerves.
• The green shading shows anterior spread into the paravertebral space and laterally into the intercostal space. Anterior spread is more variable and less extensive than posterior spread. It anesthetizes the dorsal rami, ventral rami, and sympathetic nerves.
• The orange shading shows medial spread to the epidural space and spinal foramina. Medial spread is less common, less extensive, and less reliable than posterior spread, and likely less than anterior spread as well. Medial spread anesthetizes dorsal rami, ventral rami, and sympathetic nerves.

For further information on ESP block, refer to UpToDate content on this block.