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Abstract

Abstract Background: The integration of Ultrasound (US) and Peripheral Nerve Stimulation (PNS) is often used to enhance the safety and success of peripheral nerve blocks (PNB). However, the added clinical benefit of PNS in the era of high-resolution ultrasound remains a subject of debate. We aimed to compare the procedural efficiency and clinical efficacy of US-guided PNB versus US supplemented with PNS. Methods: In this prospective, randomised controlled trial, 44 adult patients scheduled for upper limb surgery were randomised 1:1 to Group US (n = 22) or Group US + PNS (n = 22). Three were excluded after randomisation and before intervention, leaving 41 patients for per-protocol analysis (Group US, n = 20; Group US + PNS, n = 21). Participants were not informed of their allocation. The primary outcome was the success rate of the block. Secondary outcomes were the time to onset of sensory and motor blockade, the duration of block performance, the frequency of needle re-adjustment, the rate of complications, and the requirement for rescue analgesia or conversion to general anaesthesia. Results: The mean duration of block performance was shorter in the US group than the US + PNS group (8.5 ± 2.7 vs 18.0 ± 3.5 minutes; p < 0.001). Median sensory (18 vs 18 minutes; p = 0.67) and motor block onset (25.5 vs 24 minutes; p = 0.77) did not differ significantly between groups. Within the US + PNS group, needle re-adjustment was required in 66.7% of cases, primarily triggered by an initial motor response below 0.4 mA (p < 0.001). The overall success rate was 95% in the US group and 100% in the US + PNS group (p = 0.30). No block-related neurological complications occurred in either group, no patient required conversion to general anaesthesia, and the single partial block in the US group was managed successfully with local infiltration of the surgical field. Conclusion: The use of ultrasound guidance alone for peripheral nerve blocks significantly reduces procedural time without affecting the onset or success rate of the blockade. The addition of PNS frequently necessitates corrective needle re-adjustments to maintain safety thresholds, thereby increasing the technical burden and performance time without offering a superior clinical outcome. Trial registration ClinicalTrials.gov NCT07083934, registered 13 June 2025. Available at https://clinicaltrials.gov/study/NCT07083934