Preventing the Obturator Nerve Reflex

Penn State Health

Status: Completed

Conditions: Bladder Injury

Treatments: Procedure: Obturator nerve block

Study type: Interventional

Funder types: Other

Identifiers

NCT01547637

PRAMS039186EP

Details and patient eligibility

About

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

Full description

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.

Enrollment: 40 patients

Sex: All

Ages: 35+ years old

Volunteers: No Healthy Volunteers

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).

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: Single Blind

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40 participants in 2 patient groups

Ultrasound Guided

Experimental group

Description:

Ultrasound guided obturator nerve block will be performed after induction of general anesthesia. The anterior and posterior divisions of the obturator nerve will be identified with ultrasound. A stimulating needle will be inserted under direct ultrasound visualization. The anterior division will be blocked first. When adductor twitches are present at less than or equal to 0.5 mA, 10 ml of 2% lidocaine will be injected. Next, the needle will be re-directed under direct ultrasound visualization towards the posterior branch of the obturator nerve. After twitches \< 0.5 mA are achieved then 10 mL of 2% lidocaine will be injected when the needle tip is visualized in proximity of the posterior branch.

Treatment:

Procedure: Obturator nerve block

Procedure: Obturator nerve block

Anatomic landmark

Experimental group

Description:

Obturator nerve block will be performed after induction of general anesthesia. The adductor magnus tendon approach will be used. A 4 cm insulated stimulating needle will be used to verify location of the obturator nerve by contraction of the thigh adductor group. The needle will be advanced until nerve stimulation is still present at less than or equal to 0.5 mA. When the appropriate nerve stimulation is achieved 10 ml of 2% lidocaine will be injected in divided doses with frequent aspiration. Nerve conduction studies will be repeated once a minute for the first 10 minutes after block completion.

Treatment:

Procedure: Obturator nerve block

Procedure: Obturator nerve block