Preventing the Obturator Nerve Reflex

Study Overview
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Brief Summary
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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.

Detailed Description
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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.

Official Title
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Preventing the Obturator Nerve Reflex: A Comparison of Ultrasound Guided Obturator Nerve Block and Classic Anatomic Block Technique.

Conditions
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Bladder Injury

Intervention / Treatment
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* Procedure: Obturator nerve block
* Procedure: Obturator nerve block


Participation Criteria
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Eligibility Criteria
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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).

Ages Eligible for Study
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Minimum Age: 35 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Ultrasound Guided<br>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. | Procedure: Obturator nerve block<br>* Ultrasound guided peripheral obturator nerve block<br>* Other names: ultrasound guided obturator nerve block;|
| Experimental: Anatomic landmark<br>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. | Procedure: Obturator nerve block<br>* Peripheral obturator nerve block using 10 ml of 2% lidocaine<br>* Other names: anatomic obturator block;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Nerve conduction velocity | Neuromonitoring technician will measure and record obturator nerve conduction velocity in pre-defined time intervals after performance of obturator nerve block. | 1 day | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Obturator nerve block, Regional anesthesia, TURBT