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Following standard monitoring (ECG, non-invasive blood pressure, SpO2, perfusion index), the patient will be prepared in a sitting position. Under aseptic conditions, the L3-L4 or L4-L5 intervertebral space will be identified using a midline approach; a 25-gauge Quincke spinal needle will be inserted into the subarachnoid space. After confirmation of free CSF flow, hyperbaric bupivacaine 0.5% will be administered intrathecally.

After standard monitoring (ECG, non-invasive blood pressure, SpO2, perfusion index), the patient will be placed in the supine position. Under aseptic conditions, a high-frequency linear ultrasound probe will be placed under the inguinal ligament to visualize the iliac fascia compartment; then, the probe will be slid cephalad over the inguinal ligament to identify the supra-inguinal approach point. Using the in-plane technique, a 22-gauge, 50 mm block needle will be passed through the iliac fascia under real-time ultrasound guidance. Negative aspiration will be confirmed by ultrasonographic visualization of the characteristic hydrodissection between the iliac fascia and the iliopsoas muscle. 40 mL of 0.20% bupivacaine local anesthetic will be injected.