Background and Aims Ultrasound-guided obturator nerve block is performed to prevent adductor muscle spasm during transurethral resection of bladder tumors. The aim of the study was to compare the effectiveness of a single-proximal injection protocol versus a double-distal injection protocol for obturator nerve block.

Methods A total of 60 obturator nerve blocks were conducted (NCT05540847) and the patients were divided into two groups. The first group received an ultrasound-guided single injection for obturator nerve block (proximal group), while the second group received a double-injection technique for obturator nerve block in transurethral resection of bladder cancer under spinal anesthesia (distal group). In proximal group, the local anesthetic solution (10ml bupivacaine 0.25%) was administered into the interfascial plane between pectineus and obturator externus muscles. In distal group, first injection was administered into the interfascial plane between the adductor longus and adductor brevis muscles and the second injection between the adductor magnus and adductor brevis muscles (10ml bupivacaine 0.25% for each). The grade of adductor muscle spasm, clinical effectiveness rate, duration of the block procedure, and any complications were documented. Patients who experienced grade four adductor spasms were transferred to general anesthesia.

Results The number of patients who did not experience adductor muscle spasms in the proximal group was significantly higher than in the distal group. The procedure time was shorter in proximal group.

Conclusions There was no significant difference in clinical effectiveness between the two groups. The proximal group which provşdes nerve block with less local anesthetic, maybe a strong alternative to the distal technique.