Transversus Abdominis Plane Block: An Updated Review of Anatomy and Techniques

Abstract

Purpose of review: Transversus abdominis plane (TAP) block is a regional technique for analgesia of the anterolateral abdominal wall. This review highlights the nomenclature system and recent advances in TAP block techniques and proposes directions for future research.

Recent findings: Ultrasound guidance is now considered the gold standard in TAP blocks. It is easy to acquire ultrasound images; it can be used in many surgeries involving the anterolateral abdominal wall. However, the efficacy of ultrasound-guided TAP blocks is not consistent, which might be due to the use of different approaches. The choice of technique influences the involved area and block duration. To investigate the actual analgesic effects of TAP blocks, we unified the nomenclature system and clarified the definition of each technique. Although a single-shot TAP block is limited in duration, it is still the candidate of the analgesic standard for abdominal wall surgery because the use of the catheter technique and liposomal bupivacaine may overcome this limitation.

Summary: Ultrasound-guided TAP blocks are commonly used. With the unified nomenclature and the development of catheter technique and/or liposomal local anesthetics, TAP blocks can be applied more appropriately to achieve better pain control.

Figure 1

The thoracolumbar spinal nerves (T6~L1) innervating the anterolateral abdominal wall. (a) Distribution of neurovascular structure in the anterolateral abdominal wall. (b) The pathway of the thoracolumbar spinal nerves (T12). This is the cross-sectional view of the left abdomen. The anterior primary ramus of the segmental nerves divides into anterior and lateral cutaneous branches, which supply the anterolateral abdominal wall. (c) The segmental distribution of cutaneous nerve on the anterolateral trunk.

Figure 2

The muscular structure of the anterolateral abdominal wall. RA: rectus abdominis; TA: transversus abdominis; IO: internal oblique; EO: external oblique; LS: linea semilunaris. The red dotted line: the lateral border of rectus abdominis.

Figure 3

Four approaches of ultrasound-guided transversus abdominis plane (TAP) blocks. Red dashed line indicates the oblique subcostal line, from the xiphoid to the anterior part of the iliac crest.

Figure 4

Ultrasound identification of the transversus abdominis plane. RA: rectus abdominis; TA: transversus abdominis; IO: internal oblique muscle; EO: external oblique muscle; QL: quadratus lumborum; L. alba: linea alba; L. semilunaris: linea semilunaris.

Figure 5

Subcostal approach of transversus abdominis plane (TAP) block. (a) The probe position and needle direction. The probe is parallel to the costal margin near the xiphoid. The needle is inserted in plane. (b) The corresponding ultrasound images. The TAP is between rectus abdominis and transversus abdominis, and the local anesthetic is deposited in this plane to cover the upper TAP plexus. White dashed line: the needle trajectory. Light blue area: the deposition sites of local anesthetic. RA: rectus abdominis; TA: transversus abdominis.

Figure 6

Lateral approach of transversus abdominis plane (TAP) block. (a) The probe position and needle trajectory. The probe is near or at the midaxillary line between the costal margin and the iliac crest. The needle is inserted in plane. (b) Corresponding ultrasound images. The TAP is between internal oblique and transversus abdominis. The local anesthetic is deposited in this plane to cover the lower TAP plexus. White dashed line: needle trajectory. Light blue area: the deposition site of local anesthetic. TA: transversus abdominis; IO: internal oblique; EO: external oblique.

Figure 7

Posterior approach of transversus abdominis plane (TAP) block. (a) The probe position and needle trajectory. The probe is placed posterior to the midaxillary line between the costal margin and the iliac crest. The needle is inserted in plane. (b) Corresponding ultrasound images. Posteriorly, transversus abdominis tails off and turns into the aponeurosis. The quadratus lumborum can be seen posteromedial to the aponeurosis. The injection site is at the TAP between internal oblique and transversus abdominis posterior to the midaxillary line and near the aponeurosis. White dashed line: needle trajectory. Light blue area: the deposition site of local anesthetic. TA: transversus abdominis; IO: internal oblique; EO: external oblique; QL: quadratus lumborum.