This prospective, randomized study is aimed to assess the efficacy and safety of paravertebral block compared to epidural anesthesia for percutaneous nephrolithotomy. The investigators suppose that paravertebral block is not inferior in controlling the perioperative pain for percutaneous nephrolithotomy compared to epidural block.

Background: Percutaneous nephrolithotomy (PCNL) is generally performed under general or neuraxial anesthesia. The investigators have reported three patients who were at high risk of both general anesthesia and neuraxial anesthesia received percutaneous nephrolithotomy with ultrasound guided paravertebral block. Then，The investigators performed ultrasound guided paravertebral block for 45 patients who received percutaneous nephrolithotomy successfully. The investigators' impression is that paravertebral block is as effective as epidural anesthesia for surgical anesthesia of percutaneous nephrolithotomy.

Objectives:To assess the efficacy and safety of paravertebral block compared to epidural anesthesia for surgical anesthesia of percutaneous nephrolithotomy.

Methods: Fifty adult patients undergoing elective percutaneous nephrolithotomy will be randomized to receive ultrasound guided paravertebral block or epidural anesthesia. The primary outcome will be the pain score 12h postoperation. The secondary outcomes will include: time spent to perform block, dose of intraoperative opioids, rate of hypotension need for vasoconstrictors, muscle Power Grading of the lower legs at the end of the operation, anus exhaust time, opioid consumption postoperation, postoperative PONV score and the frequency of vomiting , hospitalization duration and patient satisfaction.

Clinical Implications: Ultrasound guided paravertebral block could be an equally effective and safe alternative to epidural block for surgical anesthesia of percutaneous nephrolithotomy.

Inclusion Criteria:

• American Society of Anesthesiologists physical statusⅠ-Ⅲ
• Undergo first stage percutaneous nephrolithotomy
• Informed consent

Exclusion Criteria:

• BMI>35
• Coagulopathy, on anticoagulants
• History of surgery on spine
• Spine deformity
• A known allergy to the drugs being used
• Tumor or infection at the site of puncture
• inability to provide adequate informed consent
• refusal to participate in the study

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