Randomized Controlled Trial Comparing Ultrasound-guided Pudendal Nerve Block to Ultrasound-guided Penile Nerve Block for Analgesia Following Pediatric Circumcision

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.