Ultrasound-guided transversus abdominis plane (TAP) block has become a common analgesic method after surgery involving the abdominal wall. Because TAP blockade is limited to somatic anesthesia of the abdominal wall and highly dependent on interfascial spread, various newer techniques have been proposed to enhance analgesia, either in addition to TAP block or as a single modality. In particular, variants of quadratus lumborum blocks (QLBs) have been proposed as more consistent methods with an aim to accomplish somatic as well as visceral analgesia of the abdomen. The present evidence, mainly case reports, suggests that different variants of QLB have different analgesic effects and mechanisms of action, although this has not been formally validated. In particular, transmuscular QLB and the so-called QLB2 may result in wider and longer sensory blockade compared to TAP block (T4–L1 for QL block vs. T6–T12 for the TAP blocks) (Figures 34–1 and 34–2). This chapter focuses on underlying principles for TAP blockade and the newer QLB techniques, with an understanding that the information about the latter is based on sparse evidence of limited quality as outcome-based studies are not yet available.
The transverse abdominis plane (TAP) and quadratus lumborum 1 (QL1) blocks: anterior view. Injection of 20 mL of contrast in the TAP block resulted in the posterolateral spread from the 12th rib to the iliac crest. The QL1 block after injection of 20 mL of contrast resulted in the spread of the contrast toward the transverse process cephalad alongside the thoracolumbar fascia to the 11th and 10th intercostal spaces.
Transverse abdominis plane (TAP) and quadratus lumborum 1 (QL1) blocks: posterior view. Injection of 20 mL of contrast in the TAP block resulted in the posterolateral spread from the 12th rib to the iliac crest. After injection of 20 mL of contrast, the QL1 block resulted in the spread of the contrast toward the transverse process cephalad alongside the thoracolumbar fascia to the 11th and 10th intercostal spaces.
The transversus abdominis plane is the fascial plane superficial to the transversus abdominis muscle, the innermost muscular layer of the anterolateral abdominal wall. The upper fibrous anterior part of the muscle lies posterior to the rectus abdominis muscle and reaches the xiphoid process. The posterior aponeuroses of the transversus abdominis and internal oblique muscles fuse and attach to the thoracolumbar fascia (TLF). In the TAP, the intercostal, subcostal, and L1 segmental nerves communicate to form the upper and lower TAP plexuses, which innervate the anterolateral abdominal wall, including the parietal peritoneum. Therefore, TAP blockade requires anesthesia of the upper (also known as the subcostal or intercostal) TAP plexus, as well as the lower TAP plexus, located in the vicinity of the deep circumflex iliac artery.