Crossing the midline: How the unilateral erector spinae plane block may provide bilateral visceral analgesia.

The erector spinae plane block (ESPB) is frequently performed for a variety of indications both in the perioperative setting and the emergency department (ED). There remains controversy, however, regarding whether a single unilateral ESPB can provide bilateral visceral analgesia. In this discourse, we discuss the anatomical basis of the ESPB and describe several potential mechanisms for how a large volume unilateral thoracic ESPB may provide analgesia to the abdominal viscera to manage a variety of painful conditions encountered in the ED.