Background and Aims Ultrasound (US)-guided trans-perineal pudendal nerve block (TPNB) is a novel regional anesthesia technique for pediatric perineal surgery. However, a non-specific needle target under ultrasonography leads to high failure rate and affects analgesic outcomes. This two-center randomized trial aims to compare the analgesic effects of US in combination with neurostimulation (NS) versus US alone for TPNB. We hypothesized that addition of NS enhances the efficacy of US-guided TPNB.

Methods After approval by the hospital’s ethics committee (ANE-256105992), forty children undergoing circumcision were randomly allocated to US-NS (n =20) or US-alone (n =20) group. Both groups received TPNB with 0.2 ml/kg/side of 0.25% bupivacaine after induction of general anesthesia. Primary outcome was the proportion of patients receiving intravenous fentanyl in post-anesthesia care unit (PACU). Secondary outcomes were block performance data, postoperative oral acetaminophen and pain intensity within 24 hours, success rate, block-related complications including vascular and rectal punctures, and parental satisfaction.

Results Eleven percent of patients in US-alone group received fentanyl, while none of those in US-NS group required analgesics in PACU (p=0.230). FLACC score at 30 minutes in PACU was significantly higher in US-alone group (p=0.032). When NS was combined, a median (IQR) duration of block performance was longer (7.0 (5.8–8.1) vs. 3.2 (2.5–3.5) minutes, p<0.001). No significant difference was observed between the two groups in postoperative acetaminophen consumption, pain scores at ward, block success, block-related complications, and parental satisfaction.

Conclusions TPNB guided by US alone or in combination with neurostimulation shows similar analgesic efficacy within the first 24 hours after pediatric circumcision.