Difficult Case Review: TAP Block

Articles featured in this month’s issue were submitted from Pelvic Pain SIG. The most difficult/or unusual case presented here to deal with TAP block.  The transversus abdominis plane (TAP) block is one of the most common abdominal wall blocks and can be used for postoperative analgesia after abdominal and laparoscopic surgeries¹, as well as for treatment of chronic abdominal wall pain². The transversus abdominis plane compartment contains the T6–L1 thoracolumbar nerves and can be found between the internal oblique and transversus abdominis muscles³. Anteriorly, the nerves lie between the transversus and rectus abdominis muscles and posterolaterally, as the rectus abdominis tapers to an end, the transversus abdominis plane lies between the internal oblique and transversus abdominis muscles.

Thank you to all the AAGL SIG chairs, vice-chairs, and members – for the informative articles and for supporting this popular series and special thanks to the Pelvic Pain SIG for the submission!

A 52-year-old female presented to our chronic pain clinic with over 10 years of chronic right-sided abdominal wall pain following her abdominal hysterectomy in 2010. She had trialed centrally acting medications and received approximately 50% pain improvement with Duloxetine titrated to 60 mg po daily. On exam she has allodynia and hyperalgesia at the right lateral aspect of the pfannensteil incision. An intralesional steroid injection along the scar did not result in relief, nor did an anatomic guided ilioinguinal nerve block.

Based on the neuropathic findings on exam, the decision was made to proceed with diagnostic and therapeutic right-sided TAP block. Three approaches have been described: subcostal, lateral and posterior approaches.  Ultrasound block guidance is gold-standard and allows the operator to directly visualize the needle. With somatic abdominal pain below the umbilicus, our preferred approach is the posterior approach via the lumbar triangle of Petit⁴. This triangle is defined by the iliac crest as the inferior border, the latissimus dorsi as the posterior border, and the external oblique as the anterior border. Patient should be supine, and a high-frequency linear or curvilinear ultrasound transducer should be used.

Using the ultrasound, the skin and subcutaneous fat are visualized superficially, followed by three muscular layers, from superficial to deep: external oblique, followed by the internal oblique, and lastly, the transversus abdominis muscle. The internal oblique muscle is usually the thickest muscle layer and the transversus abdominis muscle is usually the thinnest. Ultrasound movement medially will show that the aponeurosis of the three muscle layers come together to form the rectus sheath⁵. Upon identifying the TAP compartment with the ultrasound probe, the area is prepped.  Using a 22-gauge 3.5-inch spinal needle, an in-plane technique is used to visualize the needle tip via ultrasound during the entire block. Once in the TAP compartment is entered between the internal oblique and the transversus abdominis muscles, the local anesthetic is introduced after negative aspiration for heme. On ultrasound, the injection hydrodissects the muscles and this is visible on ultrasound. While the dose and volume are limited by weight-based toxicities of the selected anesthetic, often 10-20 ml total volume are used to fill the compartment on each side performed.

Our patient had complete resolution of her persistent right lower quadrant pain immediately following the right TAP block local anesthetic with 10 ml of 0.25% bupivacaine plain and 40 mg of triamcinolone. We have repeated this injection intermittently every 3-6 months for the management of her chronic pain disorder with success. TAP blocks should be considered as an intervention for chronic abdominal wall pain, particularly in patients with an abdominal neuralgia following open surgery.

1. Rafi AN. Abdominal field block: a new approach via the lumbar triangle. Anaesthesia. 2001 Oct;56(10):1024-6.
2. Baciarello M, Migliavacca G, Marchesini M, Valente A, Allegri M, Fanelli G. Transversus Abdominis Plane Block for the Diagnosis and Treatment of Chronic Abdominal Wall Pain Following Surgery: A Case Series. Pain Pract. 2018 Jan;18(1):109-117.
3. Rozen WM, Tran TM, Ashton MW, Barrington MJ, Ivanusic JJ, Taylor GI. Refining the course of the thoracolumbar nerves: A new understanding of the innervation of the anterior abdominal wall. Clin Anat. 2008; 21:325–33
4. Tsai HC, Yoshida T, Chuang TY, Yang SF, Chang CC, Yao HY, Tai YT, Lin JA, Chen KY. Transversus Abdominis Plane Block: An Updated Review of Anatomy and Techniques. Biomed Res Int. 2017;2017:8284363.
5. Tran, D. Q. , Bravo, D. , Leurcharusmee, P. & Neal, J. M. (2019). Transversus Abdominis Plane Block. Anesthesiology, 131 (5), 1166-1190.