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Ultrasound-Guided Pudendal Nerve Block for Intra and Postoperative Pain Management in Pediatric Penoscrotal Surgery

In this video, a bilateral ultrasound-guided pudendal nerve block is demonstrated on a 15-month-old healthy child undergoing circumcision and penoscrotal fusion repair. After the induction of general anesthesia, a nerve block time-out is conducted. Subsequently, the patient is positioned in the frog-leg stance by an assistant, and the perineum is cleaned using chlorhexidine. Using a high-frequency linear ultrasound probe, the ischiorectal fossa is identified between the ischial tuberosity and the anus at the 3 and 9 o’clock positions relative to the anus. A 22-gauge, 50-millimeter-long Pajunk needle is then inserted using an out-of-plane technique, advanced 1-2 cm deep and medial to the ischial tuberosity, until a subtle change in resistance or “pop” is felt, confirming the correct placement below the sacrospinous ligament. The local anesthetic (0.3 to 0.5 mL/kg of 0.2% Ropivacaine or 0.25% Bupivacaine on each side) is then incrementally injected, observed as spreading medially and beneath the ischial tuberosity. The block is then repeated on the other side. Our patient tolerated the procedure well and did not require any opioids intraoperatively, postoperatively in the post-anesthesia care unit, or at home following discharge.

Traditionally, caudal and penile blocks have been standard for managing postoperative pain in pediatric circumcision and hypospadias repair surgeries. However, the emergence of ultrasound-guided pudendal nerve block has gained favor due to its longer-lasting effect compared to caudal block, its suitability for patients with sacral anomalies and larger body sizes, and its ability to minimize issues like urinary retention and leg weakness. At our institution, in line with the consensus among our urologists and supported by literature, we shifted our procedural approach from caudal block to ultrasound-guided pudendal nerve block for pediatric penoscrotal surgeries. Despite a brief learning curve, this technique was quickly embraced by our acute pain team, who appreciated its simplicity and effectiveness. Following surgery, our acute pain nurses monitored opioid analgesic administration by caregivers, revealing a significant decrease in opioid usage. In light of this reduction, our urologists ceased prescribing opioids upon discharge for these patients.
Ultrasound-guided bilateral pudendal nerve block has emerged as an alternative for postoperative pain management in circumcision and hypospadias repair surgeries, offering extended pain relief and suitability for patients with sacral deformities while mitigating the risk of urinary retention and leg weakness seen with caudal block.¹ Here, we are describing this technique being utilized for a 15-month-old healthy child presenting for circumcision and penoscrotal fusion repair, following parental consent.

Equipment needed: - High-frequency linear ultrasound probe - Sterile ultrasound probe cover - 50 mm hyperechoic nerve block needle - Ropivacaine 0.2% or Bupivacaine 0.25% - 10 mL syringe - Normal saline syringe for hydro dissection - Chlora Prep sticks - Sterile gloves Procedure: Following induction of anesthesia and securing the airway, position the patient in frog leg position. This can be easily achieved in small children by having someone flex the legs upward and bringing the soles of the feet together. Place a folded towel underneath the pelvis to raise the perineum from the OR bed. This will allow better access for hand and ultrasound maneuvering. Begin by placing the ultrasound transducer on the perineum at the 9 o'clock position in relation to the anus. Scan this area to visualize the ischial tuberosity, recognizable as a hyperechoic dome. At this level, the pudendal nerve and artery traverse through Alcock's Canal, typically located medially and 1-2 cm deep to the ischial tuberosity, although rarely visible under ultrasound. The needle is introduced medially to the ischial tuberosity, parallel to the ultrasound beam. Although considered an out-of-plane technique, due to the parallel alignment of the needle and ultrasound beam, the entire distal portion of the needle can be visualized throughout the procedure. Upon advancing the needle 1-2 cm deep and medial to the ischial tuberosity, a noticeable change in resistance or "pop" may be felt. Our target, or the plane where the pudendal nerve travels is found under the sacrospinous ligament. Inject 0.2 to 0.3 mL of 0.2% Ropivacaine or 0.25% Bupivacaine into this plane. Correct anesthetic spread is confirmed when local anesthetic tracks medially and beneath the ischial tuberosity. Incorrect site of injection is observed when the spread of local anesthetic tracks laterally or superficial to the ischial tuberosity. For a left pudendal nerve block, position the ultrasound transducer at 3 o'clock on the perineum and follow the same steps.

The peripheral nerve block was successfully completed without any complications. The patient tolerated the procedure well.
Regional anesthesia plays a crucial role in managing intraoperative and postoperative pain in pediatric patients presenting for circumcision and hypospadias surgery. Traditionally, caudal epidural has been the primary technique for pain control, but pudendal block has gained popularity recently due to its long-lasting effect compared to caudal block.³ Moreover, it can be utilized in patients with sacral deformities and older children without concerns about motor weakness or urinary retention as potential side effects.¹ The pudendal nerve arises from the anterior rami of the second, third and fourth nerves of the sacral plexus. It's a mixed nerve and provides sensory innervation to the external genitalia, skin around the anus, anal canal and perineum and motor innervation to pelvic muscles, the external urethral sphincter and the external anal sphincter. It courses through the ischiorectal fossa, passes in between the sacrospinous and sacrotuberous ligaments and then branches into the dorsal nerve of penis or clitoris, the perineal nerve and the inferior rectal nerve. Historically, landmark-based techniques have been employed for pudendal block, where the needle is introduced in trans perineal plane at midpoint between the anus and the ischial tuberosity, with a sudden loss of resistance indicating passage through the sacrospinous ligament and local anesthetic is deposited there. However, this method had limitations due to anatomical variability and potential for incomplete nerve blockade. Over time, nerve stimulation was incorporated into the landmark-based technique to assist in confirming needle placement.⁴  Nerve stimulation typically uses a stimulation current of 2.5–5 mA at 2 Hz. Nerve stimulation typically employs a current of 2.5–5 mA at 2 Hz, with correct positioning confirmed by eliciting contractions in anal or perineal muscles. Nonetheless, risks such as intravascular or rectal puncture remain. Hence, ultrasound-guided techniques have gained popularity for their improved accuracy and precision in targeting the pudendal nerve.²
There are no conflicts to disclose in this case.
None.

1. Hecht S, Piñeda J, Bayne A. Ultrasound-guided Pudendal Block Is a Viable Alternative to Caudal Block for Hypospadias Surgery: A Single-Surgeon Pilot Study. Urology. 2018;113:192-196. 

 2. Boisvert-Moreau F, Turcotte B, Albert N, Singbo N, Moore K, Boivin A. Randomized controlled trial (RCT) comparing ultrasound-guided pudendal nerve block with ultrasound-guided penile nerve block for analgesia during pediatric circumcision. Reg Anesth Pain Med. 2023;48(3):127-133. 

3. Naja Z, Al-Tannir MA, Faysal W, Daoud N, Ziade F, El-Rajab M. A comparison of pudendal block vs dorsal penile nerve block for circumcision in children: a randomised controlled trial. Anaesthesia. 2011;66(9):802-807. 

 4. Gaudet-Ferrand I, De La Arena P, Bringuier S, et al. Ultrasound-guided pudendal nerve block in children: A new technique of ultrasound-guided transperineal approach. Pediatr Anesth. 2018; 28: 53-58. 

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