A Comparison Between Blind and Nerve Stimulation Guided Obturator Nerve Block in Transurethral Resection of Bladder Tumor

Introduction

T he obturator nerve passes in close proximity to the lateral bladder wall. ¹ As a result, transurethral resection of bladder tumor (TURBT) in the lateral bladder wall may provoke obturator reflex and consequently adductor contraction and leg jerking. ¹

Bladder perforation is a disastrous event in this scenario. As a matter of fact, general anesthesia (GA) and injection of muscle relaxant agents is the preferred method of anesthesia in these patients. ^1,2 When GA is high risk because of cardiopulmonary diseases, spinal analgesia (SA) plus local blockade of the obturator nerve is an alternative. ^3,4

Recently, a new technique of obturator nerve block (ONB) has been introduced. In this technique, the obturator nerve is detected by nerve stimulation during cystoscopy. Then, 15 mL of lidocaine HCl 2% is injected around the nerve by a needle through the working channel of the cystoscope (Fig. 1).

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FIG. 1.

Nerve stimulation and lidocaine injection using a needle electrode through the working channel of the cystoscope.

Using a nerve stimulation device is sophisticated. In this study, we performed transurethral ONB considering anatomic landmarks without nerve stimulation and compared it with the previous methods.

Patients and Methods

After consensus, 112 patients with lateral bladder wall tumors who were at high risk for GA were included in the study. Patients were categorized randomly in three groups. All the patients underwent SA before TURBT. After SA, ONB was performed by injection of 15 mL lidocaine HCl 2% using a needle through the working channel of the cystoscope in the first and third groups. In the first group, the obturator nerve was detected by nerve stimulation, but in the third group, we only used anatomic landmarks to determine the position of the obturator nerve. In the second group, we used physiologic saline instead of lidocaine as a placebo. All injections were performed at a tumor-free area of the lateral bladder wall. In cases of bladder tumor compromising the integrity of the bladder, the patients were excluded from study. One minute after ONB, TURBT was started, and leg jerking and the duration of the procedure were reported.

Results

The median ages in the three groups were not statistically different. These were 55.4, 57.8, and 58.4 years in the first, second, and third groups, respectively. Also the male/female ratios in the groups were similar. These were 79.5% male in the first, 80.9% in the second, and 80.7% in the third groups (P=0.986). Table 1 shows the final pathology results of tumors in each cohort of study.

Obturator reflexes and leg jerking were reported in 5.8% (2 patients), 34% (11 patients), and 6.3% (3 patients) in the first, second, and third groups, respectively. The occurrence of leg jerking was not different in the first and third groups.

The average tumor sizes seen in the preoperative ultrasonography were not significantly different. In the first group, it was 3.32±1.16 (1.5–5) cm; in the second group, it was 3.54±1.17 (1.7–5) cm; and in the third group, it was 3.64±1.32 (2–5) cm (P=0.544).

The procedure from the start to the end of ONB took on average 6.7, 6.1, and 5.2 minutes in the first, second, and third groups, respectively (P=0.0001). This was statistically equal in the first and third groups.

There was no case of bladder perforation or severe bleeding. Twenty-three cases of muscle invasion were detected after pathologic examination, and in 85 patients, the tumors were superficial.

Discussion

The obturator nerve is a motor neuron originating from T12–L2. The obturator nerve passes in close proximity to the prostatic urethra, bladder neck, and inferolateral wall of the bladder. ¹

Obturator nerve stimulation during TURBT causes adductor muscle contraction and leg jerking. This can lead to bladder perforation, bleeding, and incomplete resection of tumor or hematoma and consequently may increase morbidity and mortality of the procedure. ^3,5,6 Therefore, ONB should be considered in association with SA in patients who are at high risk for GA. ³

A few techniques have been introduced for ONB. Transcutaneous blockade using anatomic landmarks is performed by anesthesiologists, and it may be time consuming. The success rate of this technique in different studies is 60% to 91%.^{(2,6 –8)}

There is a variety of modifications to increase the efficacy of ONB. ^{9 –13} Ultrasonography and nerve stimulation are modalities to determine the exact site of the obturator nerve and increase procedure efficacy. The method proposed by Winnie and associates ¹⁴ (injection of local anesthetic into the femoral nerve sheath) has been debatable because of its efficacy for obturator nerve block. Some anesthesiologists use ultrasonography to find the exact place of the anterior branch of the obturator nerve to block it selectively. ¹⁵

Introduction of the bipolar system and laser for TURBT has lowered adductor contraction and leg jerking.^{(16 –19)} These modalities, however, are expensive and not available in many centers.

In this study, lidocaine injection in the extraperitoneal space around the obturator nerve even without applying nerve stimulation had sensible results. Lidocaine injection in this study was totally safe, and no prominent side effect related to lidocaine was reported in this study.

To show the distribution of injected material, in one of our patients, we added contrast agent to the lidocaine. In Figure 2, you can see the pelvic CT of that patient immediately after the procedure; the injected material has covered the posterolateral side of the bladder.

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FIG. 2.

Distribution of lidocaine and contrast along the posterolateral wall of the bladder (arrow).

ONB without nerve stimulation has some pitfalls. First, there may be variations in the track of the obturator nerve. Second, the probability of tumor seeding is a scary flaw.

In spite of that, we believe that ONB based on anatomic landmarks and without nerve stimulation is effective and safe enough to be proposed in urologic centers. In contrast to transcutaneous techniques, this technique is performed by an urologist, not an anesthesiologist.

Conclusion

Transvesical ONB is a new technique in local blockade of the obturator nerve. This nerve blockade may be performed by the guide of nerve stimulation or anatomic landmarks. Relying on anatomic landmarks is effective and less sophisticated than applying nerve stimulation.