What is the recommended technique for administering an obturator nerve block (ONB) during Transurethral Resection of Bladder Tumor (TURBT)?

Obturator Nerve Block Technique During TURBT

The inguinal approach for obturator nerve block is the recommended technique during TURBT, as it demonstrates superior success rates (96.1% vs 84.0%), requires fewer needle attempts, and offers better anatomical accessibility compared to the classic pubic approach. 1

Why Obturator Nerve Block is Essential

• ONB prevents adductor muscle spasm when resecting lateral wall bladder tumors, which can cause violent thigh adduction leading to bladder perforation and incomplete tumor resection 1, 2
• Combining spinal anesthesia with ONB significantly reduces bladder perforation (RR = 0.24), decreases obturator nerve reflex incidence (RR = 0.22), shortens hospital stay, and lowers tumor recurrence rates compared to spinal anesthesia alone 3

Recommended Inguinal Approach Technique

Anatomical Landmarks and Needle Insertion

• Insert the needle at the midpoint between the femoral artery and the inner margin of the adductor longus muscle, 0.5 cm below the inguinal crease 1
• Use a nerve stimulator to identify the obturator nerve by observing adductor muscle contraction 1, 2
• Administer 10 ml of 2% lidocaine once proper nerve stimulation is confirmed 4

Technical Advantages

• The inguinal approach provides easier anatomical access because the obturator nerve is more superficial at this location compared to the deep-seated position in the classic pubic approach 1, 5
• Requires significantly fewer needle attempts (1.3 ± 0.6 vs 1.8 ± 0.9 attempts) 1
• Lower risk of vascular injury compared to the classic approach 5

Alternative: Classic Pubic Approach

When to Consider

• If inguinal approach fails after 3 attempts, the classic pubic approach may be attempted 1

Technique Details

• Insert needle at a point 1.5 cm lateral and 1.5 cm inferior to the pubic tubercle 1
• Use nerve stimulator guidance with the same local anesthetic dosing 1
• Be aware this approach has lower success rates (84.0%) and higher needle attempt requirements 1

Alternative: Transvesical (Intravesical) Approach

Technique

• Performed through the cystoscope during the procedure by injecting local anesthetic directly around the obturator nerve under direct visualization 2, 4

Critical Limitations

• Significantly less effective than the inguinal approach with higher rates of bladder perforation (6 perforations vs 2 perforations in inguinal group) 4
• Lower overall efficacy in preventing adductor spasm 2, 4
• Should be considered a last resort rather than a primary technique 2

Timing and Integration with Anesthesia

• Perform ONB immediately after establishing spinal anesthesia and before beginning the TURBT procedure 1, 2
• Bilateral ONB is recommended for comprehensive coverage 5
• Verify block success by testing for absence of adductor muscle response before proceeding with lateral wall resection 2

Common Pitfalls to Avoid

• Do not proceed with lateral wall tumor resection without confirming successful ONB, as this dramatically increases perforation risk 3
• Avoid the transvesical approach as a first-line technique due to inferior outcomes 2, 4
• If block fails after 3 attempts with one approach, switch to an alternative technique rather than persisting 1
• Ensure nerve stimulator settings are appropriate to elicit visible adductor contraction for proper nerve identification 1, 2