Transversus Abdominis Plane Block 

Updated: May 31, 2018
Author: Michael T Wiisanen, MD; Chief Editor: Meda Raghavendra (Raghu), MD 

Overview

Background

The transverse abdominis plane (TAP) block is a peripheral nerve block designed to anesthetize the nerves supplying the anterior abdominal wall (T6 to L1). It was first described in 2001 by Rafi as a traditional blind landmark technique using the lumbar triangle of Petit (see the image below).[1]

Anatomical depiction of the triangle of Petit from Anatomical depiction of the triangle of Petit from the lateral view.

Local anesthetic is then injected between the internal oblique and transverse abdominis muscles just deep the fascial plane between (the plane through which the sensory nerves pass; see the images below).

Cross-section of the abdominal wall layers. The TA Cross-section of the abdominal wall layers. The TAP block is performed by deposition of local anesthetic between the transversus abdominis muscle and the fascial layer superficial to it.
Illustration depicting the placement of the ultras Illustration depicting the placement of the ultrasound probe along the abdominal wall, and the ideal placement of local anesthetic.

In a recent meta-analysis, the TAP block was shown to reduce the need for postoperative opioid use, increase the time to first request for further analgesia, and provide more effective pain relief, while decreasing opioid related side effects such as sedation and postoperative nausea and vomiting.[2] Studies included a combination of both general abdominal and gynecologic procedures.[3, 4] The introduction of ultrasound has allowed providers to identify the appropriate tissue plane and perform this block with greater accuracy under direct visualization.[5]

Indications

The TAP block is a simple procedure that can be used as an adjunct for postoperative pain control in abdominal, gynecologic[6] , or urologic surgery involving the T6 to L1 distribution.[1, 3, 4, 5] Surgical procedures investigated by randomized clinical trials include large bowel resection, caesarean delivery, abdominal hysterectomy, open appendectomy, and laparoscopic cholecystectomy.[1, 7]

However, the TAP block has also found clinical utility in procedures such as abdominal and inguinal hernia repair[8] , radical prostatectomy, nephrectomy[9] , and many different laparoscopic procedures in general.[10] Bilateral TAP blocks can be used for midline incisions. This technique is also useful for procedures in which epidural analgesia is contraindicated (ie, anticoagulated patients). In addition, if prolonged analgesia is desired, a continuous TAP block technique with placement of a catheter has been described.[11]

Contraindications

Very few contraindications exist to performing a TAP block. Absolute contraindications include infection at the site of injection, patient refusal or inability to cooperate, and allergy to local anesthetics.

Relevant Anatomy

The abdominal wall is composed of 5 paired muscles: 2 vertical muscles (the rectus abdominis and the pyramidalis) and 3 layered, flat muscles (the external abdominal oblique, the internal abdominal oblique, and the transversus abdominis muscles).

The internal abdominal oblique muscle is the intermediate layer of the 3 paired, flat abdominal muscles. It originates broadly from the anterior portion of the iliac crest, lateral half of the inguinal ligament, and thoracolumbar fascia. The internal abdominal oblique inserts on the inferior border of the 10th-12th ribs, the linea alba, and the pubic crest via the conjoint tendon. The muscle fibers of the internal abdominal oblique course upward in a superomedial orientation, perpendicular to the muscle fibers of the external abdominal oblique.

The transversus abdominis muscle is the deepest of the 3 paired, flat abdominal muscles. It originates on the internal surfaces of the 7th–12th costal cartilages, thoracolumbar fascia, anterior three fourths of the iliac crest, and lateral third of the inguinal ligament. As with the other flat muscles, the transversus abdominis forms a broad aponeurosis that helps make up the rectus sheath before it fuses in the midline to the linea alba. Above the arcuate line, the transversus abdominis aponeurosis contributes to the posterior rectus sheath. Below the arcuate line, it is fused with the other flat muscles as the anterior rectus sheath.

For more information about the relevant anatomy, see Regions and Planes of the Abdomen.

 

Periprocedural Care

Patient Education & Consent

Patient Instructions

Patients must be educated first about the expected length of analgesic effect. The duration of action of this block is variable, with one source reporting up to 36 hours of effective analgesia from a single injection.[3] Anecdotally, we find the TAP blocks to last anywhere from 18-24 hours. An expectation should be given to patients that this procedure is intended to eliminate somatic abdominal incision pain due to the procedure, but that visceral pain will not be affected. Patients should also be educated regarding any signs or symptoms of possible complications. These would include bruising at the injection site or signs of infection (ie, redness, fever, or chills).

Pre-Procedure Planning

Equipment

The equipment needed includes syringes for local anesthetic (the authors use 0.5% bupivacaine, 15-20 mL per side), a 21-gauge 100-mm needle with tubing, antiseptic for skin disinfection, and, if using ultrasound guidance, an ultrasound machine with high-frequency probe (10-5 MHz) and ultrasound gel (see the image below).

Equipment needed for TAP block (ultrasound probe n Equipment needed for TAP block (ultrasound probe not shown).

Patient Preparation

The TAP block can be performed preoperatively, intraoperatively, or postoperatively. The patient does not need to be awake for the procedure, and in fact, the authors prefer to do it while the patient is under either general or spinal anesthesia.

Monitoring & Follow-up

The type and duration of monitoring for this block do not differ from other peripheral nerve blocks preformed today. These include standard ASA monitors with ECG, blood pressure, and oxygen saturation. Additional monitoring beyond the acute time frame to perform the block is not required.

Complications

Overall, the TAP block is a relatively safe procedure with minimal complications. In addition to the common complications associated with any peripheral nerve block (ie, local anesthetic toxicity, intravascular injection, nerve injury, bleeding, and infection), inadvertent peritoneal puncture is a risk with this block.

The exact incidence of peritoneal puncture is unknown. One investigator who has preformed several hundred TAP blocks reported no complications related to peritoneal puncture.[3] A review article on this subject reported only an allergic reaction upon injection with no other listed complications.[1] However, one source does cite the incidence in intraperitoneal injection as 2%.[12] Bowel hematoma, enlarged liver laceration, and transient femoral nerve palsy are among serious but very rare reported complications.[13] Other organ injury, namely spleen and kidney, are also possible complications.

 

Technique

Approach Considerations

Ultrasound-Guided (Posterior Approach)

With the patient in the supine position, the ultrasound probe is placed in a transverse plane between the lower costal margin and the iliac crest in the midaxillary line (see the image below).

Illustration depicting the placement of the ultras Illustration depicting the placement of the ultrasound probe along the abdominal wall, and the ideal placement of local anesthetic.

The needle is advanced using in-plane technique with an anteromedial-to-posterolateral direction (see the image below).

Positioning of the patient and ultrasound probe fo Positioning of the patient and ultrasound probe for TAP block (posterior approach).

The needle is advanced between the aponeurosis of the internal oblique and transversus abdominis muscles. With intermittent aspiration, the local anesthetic is deposited and seen as a hypoechoic shadow pushing the 2 layers apart (see the image below).

TAP block (posterior approach) demonstrating depos TAP block (posterior approach) demonstrating deposition of local anesthetic between transversus abdominis muscle and its fascial plane. EO - external oblique muscle, IO - internal oblique muscle, TA - transversus abdominis muscle, P - peritoneum

Visualizing hypoechoic spread, with the fascial layer above and the muscle layer below, ensures proper deposition.

A video depicting the posterior approach can be seen below.

Ultrasound-guided TAP block (posterior approach).

Ultrasound-Guided (Subcostal Approach)

With the patient supine, the ultrasound probe is placed parallel to the subcostal margin near the xiphoid process. The transversus abdominis muscle is identified as the more hypoechoic muscle layer just beneath the rectus abdominis muscle near the xiphoid (see the image below).

Ultrasound image of abdominal layers for subcostal Ultrasound image of abdominal layers for subcostal approach. SC (subcutaneous tissue); RA (rectus abdominis); TA (transversus abdominis); L/M (lateral and medial)

Between the lateral edge of the rectus and the medial edges of the internal and external oblique muscles, the aponeurosis above the transversus abdominis is the first layer below the subcutaneous tissue. With the probe near the xiphoid, the needle is advanced in-plane, passing just below the rectus to the TAP. As with the posterior approach, local anesthetic is deposited with intermittent aspiration and visualized as a hypoechoic layer transecting the TAP.[11]

Traditional (Blind) Approach

In this approach, the lumbar triangle of Petit is identified. The triangle of Petit is formed by the iliac crest as the base, the external oblique muscle as the anterior border, and the latissimus dorsi muscle as the posterior border.[1] The floor of the triangle is made up of the fascia from both the external and internal oblique muscles (see the image below). A needle is inserted perpendicular to the skin just cephalad to the iliac crest near the midaxillary line. The TAP is identified using a 2-pop sensation (loss of resistance). The first pop indicates penetration of the fascia of the external oblique muscle, and the second indicates penetration of the fascia of the internal oblique muscle. Local anesthetic is then injected with multiple aspirations.

Anatomical depiction of the triangle of Petit from Anatomical depiction of the triangle of Petit from the lateral view.
 

Questions & Answers