Life-threatening haemorrhage following obturator artery injury during transurethral bladder surgery: a sequel of an unsuccessful obturator nerve block.

In spite of prior blockade of the obturator nerve with 1% mepivacaine (8 ml) utilizing a nerve stimulator, violent leg jerking was evoked during transurethral electroresection of a bladder tumour approximately 1 h after the blockade in a 68-year-old man. The patient became severely hypotensive immediately following the jerking, and a large lower abdominal swelling concurrently developed. The urgent laparotomy indicated that the left obturator artery was severely injured by the resectoscope associated with the bladder perforation, causing acute massive haemorrhage. The patient recovered uneventfully after adequate surgery. Investigation of the literature suggested that both our nerve stimulation technique and anatomical approach were appropriate. It was therefore unlikely that our block resulted in failure because of an inappropriate site for deposition of the anaesthetic. However, consensus does not appear to have been obtained as to the concentration and volume of the anaesthetic necessary for prevention of the obturator nerve stimulation during the transurethral procedures. The concentration and volume of mepivacaine we used might have been too low and/or small, respectively, to profoundly block all the motor neuron fibres of the nerve. Alternatively, stimulation of the obturator nerve might occur because of the presence of some anatomical variant, such as the accessory obturator nerve or its abnormal branching. In conclusion, some uncertainty appears to exist in the effectiveness of the local anaesthetic blockade of the obturator nerve. In order to attain profound blockade of the motor neuron fibres of the obturator nerve and thereby prevent the thigh-adductor muscle contraction which can lead to life-threatening situations, we recommend, even with a nerve stimulator, to use a larger volume of a higher concentration of local anaesthetic with a longer duration in the obturator nerve block for the transurethral procedures.