Transversus Abdominis Plane Block

Indications and Clinical Considerations

The transversus abdominis plane (TAP) block is a straightforward technique that can be used as a diagnostic and therapeutic maneuver as well as to provide surgical anesthesia for abdominal surgeries below the umbilicus. It can aid the clinician in the differential diagnosis of abdominal pain by helping to distinguish abdominal wall pain from pain of intraperitoneal origin. This technique has great clinical utility in both children and adults when managing acute postoperative and posttrauma pain, including postcesarean section pain that emanates from the abdominal wall below the umbilicus. The TAP block has recently been used to provide surgical anesthesia for abdominal and pelvic surgical procedures, including laparoscopy, radical prostatectomy, inguinal hernia repair, and nephrectomy. Pain of malignant origin involving the anterior abdominal wall has been successfully managed by the placement of a catheter for continuous infusions of local anesthetics using this technique ( Fig. 117.1 ).

FIG. 117.1, A, The transversus abdominis plane block catheter was secured to the skin. B, Straight course of the block catheter was confirmed by an abdominal x-ray, lateral view.

Clinically Relevant Anatomy

The intercostal and subcostal nerves provide innervation to the skin, muscles, ribs, and the parietal pleura and parietal peritoneum. The anatomic basis of the TAP block is that the innervation of the anterolateral abdominal wall is provided by the lower 6 intercostal nerves and the first lumbar nerve. The anterior branches of these nerves pass within a fascial plane between the internal oblique muscle and the transversus abdominis muscle, making them easily accessible for blockade with local anesthetic by placing a needle into this fascial plane ( Fig. 117.2 ). Within this fascial plane there are many interconnections between the various intercostal nerves, and it is thought that these interconnections form a pseudo-plexus contributing to the efficacy of this block ( Fig. 117.3 ).