BACKGROUND: The obturator nerve passes in close proximity to the inferolateral bladder wall. Transurethral resection of bladder tumors close to these areas may stimulate the obturator nerve, causing violent adductor contraction and possible inadvertent bladder perforation. To avoid this reaction, local anesthetic blockade of the obturator nerve as it passes through the obturator canal is effective to stop adductor spasm during spinal anesthesia. The use of nerve stimulator for the obturator nerve block is simple and well described. We investigated the dosage of local anesthetics and the depth of skin to nerve in obturator nerve block using nerve stimulator.

METHODS: We performed obturator nerve block in 87 cases by use of spinal needle and nerve stimulator, and measured the intensity of stimulation, the dosage of local anesthetics and the depth of the skin to the obturator nerve.

RESULTS: The overall success rate of obturator nerve block was 95.4%. Body Mass Index (BMI) was positively correlated with the depth of skin to the obturator nerve. However, no correlation was found between BMI and the intensity of stimulation. The dosage of local anesthetics was 198.6 ± 7.3 mg of lidocaine. The depth of the skin to nerve was 60 ± 12 mm in men, 54 ± 11 mm in women.

CONCLUSIONS: Use of nerve stimulator for obturator nerve block is accurate, and safe. BMI was positively correlated with the depth of the obturator nerve.