Transversus Abdominis Plane Blocks

Anatomic Background

The key to using transversus abdominis plane (TAP) blocks for abdominal surgery analgesia is a thorough understanding of the anatomy.

The abdominal wall nerves from T7 to T9 emerge under the costal margin into the TAP and then penetrate the rectus abdominis muscle. Nerves T10 and T11 emerge from the end of the intercostal space, have a longer course within the plane, and then penetrate the rectus sheath and rectus abdominis muscle. The T12 and L1 nerves run from the anterior surface of quadratus lumborum muscle initially deep (inside) the transversus abdominis muscle. T12 penetrates to the TAP in a similar course to T11. However, the L1 nerves (ilioinguinal and iliohypogastric nerves) do not enter the TAP until they are superior to the anterior half of the iliac crest. A continuous line from the xiphoid process to the iliac crest, just posterior to the anterior superior iliac spine (ASIS), is termed the oblique subcostal line , and it defines the anatomically optimal site for TAP block.

As minimally invasive surgery has shown, a large part of the pain following abdominal organ surgery is derived from the incision (the area of analgesia covered by the TAP approaches). In a similar fashion to other nerve block techniques such as epidural and paravertebral blocks, it targets specific nerves that innervate the incision. The extent of block can be measured on the skin using sensory testing, and deficits in the block coverage are reflected in the areas of analgesia.

Indications and Contraindications for the Procedure

TAP blocks can be used for any surgery with pain derived from the abdominal wall. Very few complications have been reported after extensive worldwide experience. However, precautions should be taken regarding bleeding, infection, needle trauma to the abdominal structures, and local anesthetic toxicity. The only contraindications to TAP block are severe coagulopathy or the inability to adequately image and identify the target.

Suggested Technique