Comparison of Nerve Stimulating Approach and Interfascial Injection Approach During Sono-guided Obturator Nerve Block

Transurethral resection of bladder tumor (TURB) has been essential treatment for bladder tumours. Direct electrical stimulation of an obturator nerve during the TURB procedures can trigger an inadvertent adductor muscle spasm, which can cause a serious complication like bladder perforation. General anesthesia with muscle relaxants for TURB does not guarantee a prevention of the adductor muscle spasm. Spinal anesthesia with selective obturator nerve block (ONB) can be an alternative anesthesia for TURB, but adductor spasm can also be induced because of incomplete ONB. Recently, ultrasound guidance with nerve stimulator has been used to enhance the safety, efficacy and shortening the onset time of ONB. Some papers describe that comparable ONB can be done using ultrasound only without nerve stimulator, in which there is a principle that obturator nerve runs along a given pathway. Basically, obturator nerve is divided into two branches after exiting the obturator canal. The anterior branch is located in the fascial planes among adductor longus, adductor brevis and pectineus muscles, and the posterior branch is located between the adductor brevis and adductor magnus muscles at the inguinal area. But it has been known that there are many branching patterns of obturator nerve and high anatomic variability in the inguinal area in a cadaver study. And subdivisions of obturator nerve in the inguinal area have been described. Therefore, this study was conducted to investigate the success rate of ultrasound-guided obturator nerve block with interfascial injection approach group (US-IFI; experimental group) was comparable to ultrasound-guided obturator nerve block with nerve stimulating approach group (US-NS; control group) in TURB under spinal anesthesia. And we also evaluated adductor muscle twitching patterns at the inguinal region when the ONB was performed.