How I Do It: Ultrasound-Guided Bilateral Rectus Sheath Blocks
Highlights
- Schleich first described the use of bilateral rectus sheath blocks (BRSBs) in 1899 (View Highlight)
- The sensorimotor innervation of the anterior abdominal wall is supplied by the ventral rami of the thoracolumbar spinal (T7-L1) segmental nerves (View Highlight)
- The thoracolumbar nerves course along the anterolateral wall within the transversus abdominis plane (TAP), and continue anteromedial within the TAP, eventually encroaching upon the lateral aspect of the rectus sheath (View Highlight)
- The nerves then enter the lateral aspect of RAM and contribute to the formation of a nerve plexus that runs cranio-caudally within the muscle in close relation to the lateral branch of the deep epigastric artery (View Highlight)
- The thoracolumbar nerves typically pierce the posterior border (89%) and less commonly the lateral border (11%) of the RAM, with the nerves piercing the posterior border within 1.6 to 2.6 cm from the lateral edge of the RAM (View Highlight)
- The nerves provide both muscular and cutaneous branches to innervate the muscle fibers and overlying skin. Notably, the branches of the thoracolumbar nerves do not cross midline. (View Highlight)
- The external oblique (EOM), internal oblique (IOM), and transversus abdominis (TAM) muscles each form a bilaminar aponeurosis at its medial border (Figure 1) converging to form the lateral border of the RAM, termed the linea semilunaris (View Highlight)
- The anterior and posterior lamina of the EOM and the anterior lamina of the IOM fuse together and continue further medially over the ventral surface of the RAM to form the anterior portion of the rectus sheath (View Highlight)
- the posterior lamina of the IOM and anterior and posterior lamina of the TAM fuse together and continue medially dorsal to the RAM to form the posterior portion of the rectus sheath (View Highlight)
- At the medial border of the RAM, the anterior and posterior portions of the rectus sheath come together, with the fibers coursing further medially toward the medial border of the contralateral RAM forming the midline linea alba (View Highlight)
- The anterior portion of the rectus sheath extends along the entire vertical length of the RAM. In contrast, the posterior portion of the rectus sheath extends only along the upper two-thirds of the RAM. In the lower one-third, the posterior portion of the rectus sheath stops approximately midway between the umbilicus and symphysis pubis. (View Highlight)
- The target site for local anesthetic deposition is deep to the RAM**,** but superficial to the posterior aspect of the rectus sheath (View Highlight)