Trans-resectoscope stimulation predicts the need to block adductor response during bladder tumor resection.

ABSTRACT

BACKGROUND: Obturator nerve block is performed on patients who undergo transurethral resection of inferolateral bladder tumors to prevent thigh adductor muscle contraction. However, other than the tumor site, we have no criteria to judge whether this block is necessary in all patients. Moreover, it is difficult to predict the efficacy of obturator nerve block before resection. To solve these problems, we have devised a trans-resectoscope stimulation technique that involves delivering several single-twitch electrical stimuli to the inside wall of the bladder via a resectoscope to elicit contraction of the thigh adductor muscle. METHODS: Trans-resectoscope stimulation was performed in 51 cases on 45 patients for which urologists had requested obturator nerve block. If no thigh adductor muscle contraction was observed with trans-resectoscope stimulation (i.e., negative result), tumor resection was performed without further investigation. If the result was positive, we performed obturator nerve block or administered a muscle relaxant until the result turned negative. Positive or negative responses to the initial trans-resectoscope stimulation and thigh adductor muscle contraction during subsequent resection were recorded. RESULTS: The initial trans-resectoscope stimulation result was negative in 29 of the 51 cases (57%). In these cases, tumor resection was allowed to proceed, and no thigh adductor muscle contraction occurred (rate of incidence [95% confidence interval] 0% [0%-5.7%]). In cases with a positive initial trans-resectoscope stimulation result (22/51 or 43%), we performed an obturator nerve block or administered a muscle relaxant after which we once again stimulated to verify the lack of adductor response before proceeding with the resection, and no thigh adductor muscle contraction was observed during resection. CONCLUSIONS: Trans-resectoscope stimulation is beneficial not only to predict the need to block the contraction of the thigh adductor during tumor resection but also to avoid unnecessary obturator nerve block.