This chapter, provides an overview for pediatric truncal blocks. The author describes the nerve distribution and ultrasound Sonoanatomy for the common truncal blocks (transversus abdominis plane, rectus sheath, Ilioinguinal, Iliohypogastric, paravertebral, quadratus lumborum, and erector spinae blocks. Indications and contraindications as well as discussion of perineural catheters are discussed.
A three-year-old, former 33-week premature infant with a history of an omphalocele presents with a ventral hernia. She is now scheduled for repair. Her laboratory testing is unremarkable. The surgeon is requesting a regional block for this procedure and wants to discuss the options.
The anterior abdominal wall extends from the costal margin of the seventh to tenth ribs and xiphoid process to the iliac crests, inguinal ligament, and pubic crest/symphysis. The lateral borders are demarcated by the bilateral mid-axillary lines.
The anterior abdominal wall is made up of three concentric muscle layers. From superficial to deep, they are the external oblique muscle, internal oblique muscle, and the transversus abdominis muscle.
The rectus abdominis muscle is a pair of vertical muscles that run down the midline of the anterior abdominal wall.
Some individuals may also have a second midline muscle known as the pyramidalis.
The anterior abdominal wall is innervated by the T6–T12 thoracoabdominal nerves. These nerves originate from the T6–T12 spinal nerves and traverse across the neurovascular transversus abdominis plane that lies between the internal oblique muscle and the transversus abdominis muscle (Figure 53.1).
The ilioinguinal and iliohypogastric nerves arise from the L1 spinal nerve. These nerves emerge from the lateral border of the psoas muscles and travel superior and parallel to the iliac crest. They both eventually pierce the transversus abdominis muscles, though there is variability in the location at which they enter the transversus abdominis plane.
The rectus sheath encompasses the rectus abdominis muscle anteriorly and posteriorly. The anterior rectus sheath is formed from the aponeurosis of the external oblique and the internal oblique muscles. The posterior rectus sheath is formed from the aponeurosis of the internal oblique and transversus abdominis muscles.
What Changes Occur in the Rectus Sheath below the Arcuate Line?
The lower limit of the posterior rectus sheath is the arcuate line. Inferior to this point, the aponeurosis of the external oblique, internal oblique, and transversus abdominis muscles all pass anterior to the rectus abdominis muscles.
The muscles of the posterior abdominal wall include the latissimus dorsi muscle, erector spinae muscle, quadratus lumborum muscle, and the psoas major.
The erector spinae muscle is comprised of three paraspinal muscles: the iliocostalis muscle, the longissimus muscle, and the spinalis muscle.
The thoracolumbar fascia encloses the deep muscles of the back. It is comprised of three layers: anterior, middle, and posterior. The anterior layer is often referred to as the “transversalis fascia” and lies on the anterior surface of the quadratus lumborum muscle. It is thought that the thoracolumbar fascia may serve as a conduit for local anesthetic spread when performing the quadratus lumborum block.
Transversus abdominis plane block
Rectus sheath block
Quadratus lumborum block
Erector spinae block
What Is a Transversus Abdominis Plane Block?
A transversus abdominis plane (TAP) block provides somatic analgesia for the anterior abdominal wall by targeting the thoracoabdominal nerves (T6–L1). There are multiple approaches to performing the TAP block including the subcostal, oblique-subcostal, and lateral techniques. The lateral technique is used more commonly and is the easiest to perform. The patient is placed in the supine position for all approaches. The probe is held in the transverse position (i.e., parallel to the costal margin and iliac crest) and lies anywhere between the midaxillary to midclavicular line. The needle is inserted lateral to the probe, with the ultimate target for local anesthetic deposition being the transversus abdominis plane – which lies deep to internal oblique muscle and superficial to the transversus abdominis muscle (Figures 53.2–53.4).
What Are the Indications for a TAP Block?
The TAP block provides somatic analgesia for abdominal surgeries including laparoscopic surgeries, laparotomies, and caesarean sections.
The rectus sheath block provides somatic analgesia for midline incisions in the anterior abdominal wall by targeting the terminal branches of the thoracoabdominal nerves (T9–11). These nerves lie in the plane deep to rectus abdominis muscles and superficial to the posterior rectus sheath. The probe is held in the transverse orientation – superior to the umbilicus and lateral to the linea alba (Figures 53.5–53.7).
Figure 53.5 Ultrasound probe and needle position for rectus sheath block.