Ultrasound-Guided Rectus Sheath Block in a Pediatric Patient

Abstract

Rectus sheath block (RSB) is a regional anesthesia technique in which a local anesthetic is injected between the posterior aspect of the rectus abdominis muscle and the posterior rectus sheath to block the anterior cutaneous branches of the thoracoabdominal nerves. In pediatric patients, RSB is particularly useful for surgeries performed through umbilical or circumumbilical incisions, such as umbilical hernia repair, laparoscopic surgery with umbilical port placement, pyloromyotomy for hypertrophic pyloric stenosis, and surgery for duodenal atresia, intestinal malrotation, or ovarian cysts. Ultrasound guidance improves the precision and safety of the block by enabling direct visualization of the rectus abdominis muscle, posterior rectus sheath, and underlying peritoneum.

This video demonstrates ultrasound-guided bilateral RSB in a 27-day-old, 3.9-kg neonate undergoing circumumbilical pyloromyotomy for hypertrophic pyloric stenosis. The video highlights the key technical aspects of the procedure, including the identification of the posterior rectus sheath, continuous visualization of the needle tip, appropriate lateral placement of the local anesthetic within the posterior rectus sheath plane, and measures to avoid peritoneal puncture and vascular injury. Particular attention is also given to the conservative dosing of ropivacaine in neonates to minimize the risk of local anesthetic systemic toxicity.

Keywords

Infant; newborn; rectus abdominis; ultrasonography, interventional; analgesia; punctures.

Case Overview

Background

Rectus sheath block (RSB) is a regional anesthesia technique in which a local anesthetic is injected between the posterior aspect of the rectus abdominis muscle and the posterior rectus sheath to block the anterior cutaneous branches of the thoracoabdominal nerves. It provides effective analgesia for surgeries involving a midline abdominal incision.

In pediatric patients, RSB is particularly useful for surgeries performed through umbilical or circumumbilical incisions, such as umbilical hernia repair, laparoscopic surgery with umbilical port placement, pyloromyotomy for hypertrophic pyloric stenosis, and surgery for duodenal atresia, intestinal malrotation, or ovarian cysts. Randomized studies have demonstrated that RSB provides better postoperative analgesia than local wound infiltration in children undergoing umbilical hernia repair and laparoscopic inguinal hernia repair,^1–3 and an observational study suggested its effectiveness in neonatal pyloromyotomy.⁴

This video demonstrates ultrasound-guided bilateral RSB in a neonate undergoing circumumbilical pyloromyotomy for hypertrophic pyloric stenosis and highlights the practical technical considerations for safe and effective block performance.

Focused History of the Patient

The patient was a 27-day-old male neonate weighing 3.9 kg with hypertrophic pyloric stenosis who was scheduled to undergo pyloromyotomy through a circumumbilical incision. Bilateral ultrasound-guided RSBs were performed to provide perioperative analgesia for the surgical incision. General anesthesia was maintained with 2% sevoflurane and a remifentanil infusion at 0.3–0.4 μg/kg/min. A total of 5 μg of fentanyl was administered intraoperatively. No rescue analgesics were required postoperatively.

Physical Exam

An abdominal wall examination revealed no evidence of local infection, abdominal wall abnormalities, or previous surgical scars that would preclude a bilateral RSB.

Imaging

No preoperative imaging was performed. Immediately before the block, real-time ultrasonography was used to identify the rectus abdominis muscle, posterior rectus sheath, underlying peritoneum, and epigastric vessels, allowing for safe planning of the needle trajectory. In the present case, the imaging depth was set at 1.9 cm.

Options for Treatment

Several options are available for perioperative analgesia, including intravenous opioids, acetaminophen, local anesthetic wound infiltration, caudal epidural block, and ultrasound-guided peripheral nerve blocks, such as RSB. The choice among these techniques depends on the location of the surgical incision, expected postoperative pain, patient characteristics, and institutional practice.

Rationale for Treatment

Bilateral ultrasound-guided RSBs were selected to provide effective analgesia for circumumbilical incisions while reducing the need for systemic opioids. Ultrasound guidance facilitates accurate needle placement and local anesthetic injection within the posterior rectus sheath plane, particularly in neonates with small anatomical structures.

Special Considerations

The abdominal wall is thin in neonates and young infants, and the peritoneum lies immediately deep to the posterior rectus sheath. Therefore, continuous visualization of the needle tip is essential to avoid inadvertent peritoneal puncture. Color Doppler may help identify and avoid the inferior epigastric vessels, and careful calculation of the total local anesthetic dose is necessary to minimize the risk of systemic toxicity.

Discussion

Ultrasound guidance has improved the precision and safety of RSB by enabling direct visualization of the rectus abdominis muscle, posterior rectus sheath, and underlying peritoneum. This is particularly advantageous in neonates and young infants, in whom the abdominal wall is thin and inadvertent peritoneal puncture may occur if the needle tip is not continuously visualized.

At our institution, a 25-gauge regular-bevel needle is routinely used for neonatal RSB. In our experience, compared with a 22-gauge short-bevel regional block needle, a regular-bevel needle causes less tenting of the rectus abdominis muscle, facilitating accurate placement of the needle tip between the posterior aspect of the rectus abdominis muscle and the posterior rectus sheath. Because the needle may advance into the peritoneal cavity with little resistance beyond the target site, meticulous real-time visualization of the true needle tip is essential throughout the procedure.

An important technical consideration is the site of local anesthetic injection. As the anterior cutaneous branches may penetrate the rectus abdominis muscle before reaching the midline, injection at the lateral aspect of the posterior rectus sheath may improve block success by increasing the likelihood of anesthetizing the target nerves before they enter the muscle.

According to the New York School of Regional Anesthesia (NYSORA),⁵ the maximum recommended ropivacaine dose is 2.5 mg/kg. However, because plasma concentrations of α1-acid glycoprotein are lower in neonates, resulting in a higher unbound fraction of ropivacaine,⁶ a 50% dose reduction is recommended in this population.⁵ In the present case, 0.1875% ropivacaine was administered at 0.2 mL/kg per side (total 0.4 mL/kg), corresponding to a total dose of 0.75 mg/kg.

Bilateral RSB was successfully performed without block-related complications and provided effective analgesia for the circumumbilical pyloromyotomy. Careful attention to needle tip visualization, appropriate injection site selection, and conservative local anesthetic dosing may help optimize the safety and efficacy of ultrasound-guided RSB in neonatal and pediatric patients.

Equipment

• High-frequency linear ultrasound transducer (13–6 MHz)
• Sterile ultrasound probe cover
• Sterile ultrasound gel
• 25-gauge, 38-mm regular-bevel needle

Disclosures

The author reports no conflicts of interest, financial relationships, funding, sponsorship, equipment support, or other relationships that could be perceived to influence the content of this article.

Statement of Consent

The parent of the patient referred to in this video article provided informed consent for the patient to be filmed and is aware that information and images will be published online.

Acknowledgments

The author thanks the operating room staff and perioperative team for their assistance with patient care and video production.