Comparative Evaluation of Obturator Nerve Block in Lithotomy versus Supine Position to Prevent Adductor Muscle Contraction during Transurethral Resection of Bladder Tumours- Randomized Controlled Trials (RCT)

Abstract

Background: Transurethral resection of bladder tumour (TURBT) is often complicated by obturator nerve stimulation which may cause adductor muscle contraction. Obturator nerve block (ONB) is used to prevent this reflex. However, the optimal patient positioning for ONB remains unclear. Aim: To compare the efficacy, ease, and safety of ONB performed in the lithotomy position (interadductor approach) versus supine position (classical pubic approach) under peripheral nerve stimulator (PNS) guidance during TURBT.

Methods: In this prospective, randomized, double-blind study, 64 patients (ASA I–II) undergoing TURBT under spinal anaesthesia were equally divided into two groups. Group A received ONB in the lithotomy position (interadductor approach), and Group B in the supine position (classical pubic approach), using 15 mL of 0.25% bupivacaine with a PNS. Parameters assessed included block performance time, number of needle pricks, needle depth, adductor spasm grade, hemodynamic stability, and complications.

Results: The lithotomy group showed a significantly higher success rate in preventing adductor spasm (Grade 0: 87.5% vs 65.6%; p = 0.039). The mean block performance time and needle depth were shorter in Group A (4.37 ± 0.79 min vs 7.25 ± 1.64 min; p < 0.001) and (4.21 ± 0.27 cm vs 4.88 ± 0.40 cm; p < 0.001), respectively. Surgeon satisfaction was significantly higher in Group A (87.5% vs 65.6%; p = 0.039). Hemodynamic parameters remained stable and no adverse events were reported.

Conclusion: ONB using the interadductor approach in lithotomy position is easier, faster, and more effective in preventing adductor spasms during TURBT than the classical pubic approach in supine position, with a comparable safety profile.