Pudendal Nerve Block vs Penile Nerve Block for Analgesia During Pediatric Circumcision

Overview

Pediatric circumcision has been realized since the beginning of human civilization. In the United States, a 2014 review revealed a 81% prevalence of men 14-59 years old being circumcised. Circumcision surgery is mostly performed on an ambulatory basis. The best analgesia technique for this procedure has yet to be determined. Local, regional, general anaesthesia or even combinations have been described. The Dorsal Penile Nerve Block (DPNB) has been shown to be superior to topical analgesia in neonatal circumcision. A 2008 Cochrane review showed no difference in pain scores between caudal block and DPNB, but described more motor block with caudal block. For this reason, the 2017 Canadian Urological Association guidelines review recommends using DPNB with a ring block as a standard of care for neonatal circumcision with-out general anaesthesia. However, DPNB does not provide reliable coverage of the ventral surface of the penis and frenulum. Pudendal nerve block (PNB) is another regional anaesthesia technique gaining in popularity with the now widespread use of ultrasound guidance. However, it is still unclear if PNB can give better outcomes than DPNB. The ultrasound-guided pudendal nerve block has only been recently described and was not reviewed as an option at the time of the guidelines writing. PNB can be performed using surface landmarks, with nerve stimulation or with ultra-sound-guidance. It has already been proven to have lower surgical complication rates than caudal block for hypospadias surgeries. Regarding DPNB, a variety of techniques have been described using either surface landmarks or ultrasound guidance. In the past ten years, two RCTs in Lebanon and Turkey compared PNB and DPNB for penile surgeries, showing lower pain scores and lower narcotics consumption in the pudendal nerve block group. None of these studies used ultrasound-guidance. The investigators perform more than a hundred pediatric circumcisions yearly for medical indications. The surgery is done under general anaesthesia in association with either PNB or DPNB, depending on the anesthesiologist's preference. The primary objective is to compare analgesia between the two blocks during and after pediatric circumcisions to minimize post-operative pain. The research team will compare peri and postoperative pain in children receiving either ultrasound-guided pudendal nerve block or ultrasound-guided dorsal penile nerve block for circumcision surgery.

All patients will receive inhalational anaesthesia induction with a mixture of oxygen/nitrous oxide and 6% sevoflurane. Nitrous oxide will be discontinued after loss of consciousness. Standard monitoring will be applied including electrocardiography, pulse oxymetry, capnography and non-invasive blood pressure monitoring. After establishing intravenous access, anaesthesia will be deepened using propofol 1 to 3 mg/kg and fentanyl 1 mcg/kg before laryngeal mask airway insertion or intubation. Neuromuscular blockade will not be administered. Maintenance of anaesthesia will be provided with sevoflurane with an end tidal sevoflurane between 1 and 1,5 MAC. Five regional anesthesia experienced anesthesiologists not involved in the subsequent intraoperative or postoperative care of the patient will perform blocks. Pudendal nerve block patients will be positioned dorsally with the legs in the " frog " position (hips in abduction, knees flexed and sole of the feet together). An ultrasound-guided technique will be used as described previously. A linear probe will be positioned horizontally between the ischiatic tuberosity and the rectum. The ischiorectal fossa is then located between these two landmarks. Using a sterile technique, an echogenic 22 gauge, 50 mm block needle will be inserted out of plane on the superior edge of the probe, midline between the ischiatic tuberosity and the rectum. After feeling two distinct fascial " clics " and confirmation of correct needle positioning in the ischiorectal fossa under ultrasound, 0,2 mL/kg (max 10mL) of ropivacaine 0,25% will be injected under real-time ultrasound-guidance after negative aspiration. The same technique will be repeated on the contralateral side. Penile nerve block patients will be positioned in the supine position. An ultrasound-guided technique will be used as described previously. A linear probe will be placed transversely at the base of the penis while an assistant applies caudal traction to the penis. The penile neurovascular sheath is then located just above the corpus cavernosum. The dorsal penile nerve, dorsal penile artery and penile deep dorsal vein are visualized deep to Buck's fascia. Using a sterile technique, a 25 gauge, 1,5 inch needle will be inserted in-plane from lateral to medial so that the needle tip is placed into the penile neurovascular sheath, 0,1 mL/kg (max 4 mL) of ropivacaine 0,25% will be injected under real-time ultrasound guidance while retracting the needle so that the local anaesthetic solution spreads bilaterally filling the neurovascular space. The heart rate and blood pressure will be recorded before the block and every 5 minutes after block completion by the anaesthesiologist unaware of block assignment involved in the intraoperative and postoperative care of the patient. Surgical incision will be delayed for a minimum of 15 minutes after block completion. Three surgeons will perform all circumcisions using the same surgical technique. Any in-crease in blood pressure or heart rate of more than 20% above baseline within 20 minutes of block completion will be treated with an additional propofol bolus (1mg/kg) or by increasing end-tidal sevoflurane to allow for onset of the block. Any increase in blood pressure or heart rate of more than 20% above baseline 20 minutes or more after the block will be considered inadequate analgesia and will be supplemented with fentanyl 1 mcg/kg. All patients will receive dexamethasone 0,1 mg/kg (max 8 mg) and ondansetron 0,1 mg/kg (max 4 mg). Ketorolac 0,5 mg/kg (max 30 mg) will also be administered at the end of the surgery. Pain scores using the FLACC score(16) will be recorded in the post-anesthesia care unit (PACU) and ambulatory step down unit at 5, 30, 60 and 120 minutes postoperatively by trained and blinded nurses. A pain score of 4 or higher in the PACU will lead to analgesic administration. A first dose of nalbuphine 0,1 mg/kg will be administered. If inadequate, incremental doses of morphine 0,05 mg/kg will be given until adequate analgesia is achieved. Pain will also be evaluated by parents at home using the parent postoperative pain measure (PPPM) scale at 6, 12 and 24 hours postoperatively. The parents will be instructed by a trained nurse on how to assess the child's pain using this pain measure. Patients will be prescribed acetaminophen 15 mg/kg q 4h regularly (maximum 5 doses/24 hours), ibuprofen 10 mg/kg q 8h regularly and morphine 0,1 mg/kg q 4h as needed.