Preventing the Obturator Nerve Reflex

Transurethral resection of bladder tumor (TURBT) is a urologic surgery used in the treatment
of non-muscle invasive bladder cancer. A potential complication of this procedure is bladder
rupture or injury secondary to adductor muscle contraction from obturator nerve stimulation.
This risk is increased in resection of lateral wall tumors, as electrosurgical resection of
these lesions is more likely to inadvertently stimulate the obturator nerve.

There are several mechanisms for preventing the obturator reflex. Pharmacologic paralysis can
reliably inhibit thigh adduction. However, TURBT is often a short procedure that is not
amendable to intermediate duration neuromuscular blocking medications. The use of
succinylcholine is another option but is limited by its short duration of action which may
not be adequate for the time needed to resect the tumor. Additionally, many patients have
contraindications to the use of succinylcholine. Spinal anesthesia does not reliably prevent
the obturator reflex.

Regional anesthesia is another potential treatment modality to prevent the obturator reflex
during TURBT. Motor blockade of the obturator nerve will prevent this adduction in the event
of inadvertent nerve stimulation. Peripheral blockade of the obturator nerve can be combined
with either general or spinal anesthesia. Historically, obturator nerve block (ONB) has been
considered a technically challenging procedure. Recently, however, successful ultrasound
guided ONB techniques have been reported. To the best of our knowledge there has been no
study to date comparing the effectiveness of ONB achieved by anatomic landmarks (with nerve
stimulation) versus ultrasound guided ONB (with nerve stimulation) at preventing the
obturator reflex during TURBT surgery.

The key objective of this study is to compare success rates of ultrasound guided obturator
nerve block and anatomic guided obturator nerve block as determined by neuromonitoring
endpoints and surgeon observations.

Inclusion Criteria:

- Patients undergoing TURBT for lateral wall bladder tumors at risk for electrical
stimulation as determined by the attending surgeon.

Exclusion Criteria:

- Pre-existing obturator nerve injury

- Thigh adductor muscle weakness

- Neuropathy

- Local anesthetic allergy

- Infection at the site of injection

- Abnormal coagulation studies

- use of neuromuscular blocking medications (if deemed necessary by attending
anesthesiologist caring for the patient).