35 Lumbar Somatic Block
Perspective
Lumbar somatic block is often used to complement multiple intercostal nerve blocks, thus allowing anesthesia for lower abdominal and even upper leg surgery. For example, lumbar somatic block of T12, L1, and L2 will cover most of the requirements for inguinal herniorrhaphy. Likewise, individual blocks of lumbar nerves (including block of T12 off the L1 spine) may allow differentiation of lower abdominal and post-herniorrhaphy pain syndromes. Because this nerve block is carried out in a paravertebral location, it can be considered a form of paravertebral nerve block. The paravertebral block described in Chapter 37, Paravertebral Block, is a large-volume, single-injection method.
Placement
Anatomy
It is useful to conceptualize paravertebral lumbar somatic block as an intercostal block in miniature. Using this concept, the short vertebral transverse process (a “rudimentary rib”) becomes the principal focus and landmark for needle position. Lumbar somatic nerves leave the vertebral foramina slightly caudad and ventral to the transverse process of its respective vertebral level (Fig. 35-1).
As Figure 35-2 illustrates, from the intervertebral foramina the lumbar somatic nerves angle caudad and anteriorly and hence pass anterior to the lateral extent of the transverse process of the next-lower vertebral body (see Fig. 35-1
