Current Intensity for the Obturator Nerve Block (Current_ONB)

The Difference in the Current Intensity for the Obturator Nerve Block According to the Presence or Absence of Neuromuscular Blockage

The purpose of the present study was to find out the difference in current intensity required for nerve stimulation according to the presence or absence of neuromuscular blockade during the obturator nerve block procedure for TURP.

During the transurethral resection of bladder tumors (TURBT) procedure under spinal anesthesia, the obturator nerve block is required to prevent the accidental movement of adductor longus muscles by electrical stimulation. However, during general anesthesia, the contraction of the adductor longus muscle would be lost due to deep neuromuscular blockade. However, some reports showed that the contraction of the adductor longus muscle occurs even in the deep neuromuscular blockade. The current intensity for the nerve stimulation during nerve block is 0.3--0.5 mA when the needle tip is near the nerve. However, it is still unknown what current intensity is required to show the contraction of the adductor longus muscle when the patient is in a deep neuromuscular blockade. Therefore, in this study, investigators aimed to determine the difference in current intensity required for nerve stimulation according to the presence or absence of neuromuscular blockade during obturator nerve block for TURP. In addition, investigators aimed to determine that the obturator nerve block is required during the TURP procedure in patients with deep neuromuscular blockade during general anesthesia.

Transurethral Resection of Bladder, Obturator Nerve, Nerve Block, Neuromuscular Blockade, Anesthesia, General

An I-gel mask is inserted for the mechanical ventilator of the patient who is sedated with propofol. For the ultrasound-guided obturator nerve (ON) block, and needle tip gradually advanced to the anterior branch of the ON. The current intensity for the stimulation of ON starts at 1.0 mA (using the sequential electrical nerve stimulation mode), and the needle is advanced gradually to the location where the contraction of the adductor longus muscle (ALM) occurs at 0.3-0.5 mA. After fixing the needle in that position, measure the current intensity. Then, rocuronium (0.6 mg/kg) is administered under quantitative neuromuscular-blockade monitoring. When the train-of-four count becomes 0, the current intensity is increased until the contraction of the ALM occurs. The current intensity is measured when the contraction of the ALM occurs.

After measuring the initial current intensity, quantitative neuromuscular blockade monitoring is applied, and rocuronium (0.6 mg/kg) is administered.

Measuring the minimum current intensity for the stimulation of the obturator nerve to show the contraction of the adductor longus muscle.

The current intensity for the stimulation of the obturator nerve starts at 1.0 mA (using the sequential electrical nerve stimulation mode), and the needle is advanced gradually to the location where the stimulus response occurs at 0.3-0.5 mA. After fixing the needle position in a position where contraction of the adductor longus muscle responds to the minimum current intensity, measure the current intensity.

After administration of rocuronium (0.6 mg/kg), when the train-of-four count becomes 0, the current intensity for the stimulation of the obturator nerve is increased until the contraction of the adductor longus muscle occurs. The current intensity is measured when the contraction of the adductor longus muscle occurs.

After administration of rocuronium (0.6 mg/kg), the quantitative neuromuscular blockade monitoring using train-of-four is observed with 12 seconds interval. At each time point, the current intensity for the obturator nerve is increased until the contraction of the adductor longus muscle occurs. The current intensity at each time point is measured.

Inclusion Criteria: Patients undergoing TURP procedure Exclusion Criteria: Patients with anatomical or functional anomaly in the upper airways Patients with neuromuscular disease Patients with hip joint disorders BMI of < 18.5 or > 30.0 kg/m2

Koo CH, Ryu JH. Anesthetic considerations for urologic surgeries. Korean J Anesthesiol. 2020 Apr;73(2):92-102. doi: 10.4097/kja.19437. Epub 2019 Dec 17.