Background and objectivesDistal upper extremity surgery is commonly performed under regional anaesthesia, including intravenous regional anaesthesia (IVRA) and ultrasound-guided forearm nerve block. This study aimed to investigate if ultrasound-guided forearm nerve block is superior to forearm IVRA in producing a surgical block in patients undergoing carpal tunnel release.MethodsIn this observer-blinded, randomized controlled superiority trial, 100 patients undergoing carpal tunnel release were randomized to receive ultrasound-guided forearm nerve block (n = 50) or forearm IVRA (n = 50). The primary outcome was anaesthetic efficacy evaluated by classifying the blocks as complete vs incomplete. Complete anaesthesia was defined as total sensory block, incomplete anaesthesia as mild pain requiring more analgesics or need of general anaesthesia. Pain intensity on a numeric rating scale (0–10) was recorded. Surgeon satisfaction with hemostasis, surgical time, and OR stay time were recorded. Patient satisfaction with the quality of the block was assessed at POD 1.ResultsIn total, 43 (86%) of the forearm nerve blocks were evaluated as complete, compared to 33 (66%) of the forearm IVRA (p = 0.019). After the forearm nerve block, pain intensity was lower at discharge (-1.76 points lower, 95% CI (-2.92, -0.59), p = 0.0006) compared to patients treated with forearm IVRA. No differences in pain experienced at the start of the surgery, during surgery, and at POD1, nor in surgical time or total OR stay were observed between groups. Surgeon (p = 0.0016) and patient satisfaction (p = 0.0023) were slightly higher after forearm nerve block.ConclusionAn ultrasound-guided forearm nerve block is superior compared to forearm IVRA in providing a surgical block in patients undergoing carpal tunnel release.Trial registrationThis trial was registered asNCT03411551.