compare the efficacy of Lower Thoracic Epidural with Erector spinae plane block (ESPB) for post-operative analgesia after Percutaneous Nephrolithotomy with a hypothesis that both Lower Thoracic Epidural and Erector spinae plane block are effective in providing post-operative analgesia.

Percutaneous nephrolithotomy (PCNL) is the treatment of choice for patients with multiple or complex kidney or upper urinary tract stones, which necessitates the meticulous multi-modality analgesia due to mild to moderate pain originated from renal capsule dilation or nephrostomy-tube-related stress during the first 24 h after operation.

The main sources of the acute pain after PCNL are visceral pain originating from the kidneys and ureters, and somatic pain from the site incision. Renal pain is conducted through T10-L1 spinal nerves while ureter pain is conducted through T10-L2. Moreover, cutaneous innervation of the site of the incision is predominantly supplied by T10-T11 (T8-T12) because the incision site and tract for PCNL is usually used in the tenth to eleventh intercostal space, or in the subcostal area Blockade of both somatic and visceral nerves that innervate skin, muscle, kidneys, and ureters is required for the achievement of adequate analgesia after PCNL. Complete blockade of unilateral spinal nerves from T10 to L2 can provide sufficient analgesia during PCNL. This can be achieved by several regional techniques such as Lower Thoracic Epidural , Thoracic paravertebral block, Transversus abdominis block, Erector spinae block, and peri-tubal local anaesthetic infiltration .

PCNL surgery also has an increased risk for postoperative pulmonary complications because the procedure is performed near the diaphragm, especially, when approached through the upper pole of the kidney which increases the possibility of pleural and lung injuries. with poor control of the postoperative pain, this can result in decreased inspiratory and vital capacities and increase the incidence of lung atelectasis and postoperative hypoxemia. Multimodal analgesia techniques are utilized broadly to manage postoperative pain. The concept of multimodal analgesia implies not only providing analgesic drugs, but also performing nerve blocks with local anaesthetics.

Since Forrero et al. first described the Erector Spinae Plane Block (ESPB), the indications and clinical use of the block for different surgical interventions have been growing . Although, ESPB is an interfascial plane block, anatomical studies support the idea that some of its clinical benefit may derive from spread to the paravertebral and epidural space. Regional anesthesia may reduce the rate of chronic pain after surgery . Thoracic epidural blockade (TEB) using local anesthetic agents has been widely regarded as the gold standard for analgesia and reduction of associated complications following surgery.

Epidural analgesia was first accomplished by blockage with local anesthetics, and bupivacaine has been called the local anesthetic of choice for epidural infusion.. Epidural local anesthetics have been administered by continuous infusion in an attempt to minimize side effects , Nevertheless, hypotension as well as motor block , numbness , nausea and urinary retention have occurred.

Good analgesia from an epidural block can result in relieving postoperative pain , early extubation, better ventilatory mechanics and gas exchange and reduced rates of lung collapse, pneumonia and pain . However, the technique requires highly trained medical staff not only for insertion and removal of the epidural catheter but also for the management of the continuous infusion of pain medication. The risks associated with insertion of the epidural include accidental dural puncture, inadvertent high block, local anesthetic toxicity and total spinal anesthesia (inadvertent spinal injection of an epidural dose of local anesthetic), nerve injury, epidural hematoma and abscess are rare but serious complications.

Epidural is not a suitable technique for all patients and is contraindicated in patients with local infection, previous spinal surgery, disorders of blood clotting and in those taking anti-coagulant and anti-platelet therapy .

Thus, in the current study the investigators aim to compare the post-operative analgesic effect of Lower Thoracic Epidural with that of ESPB after Percutaneous Nephrolithotomy.

Inclusion Criteria:

• Age between 18 and 65 years with a body mass index (BMI) of 18-35 kg/m2
• patients with the American Society of Anesthesiologists (ASA) physical status I/II,
• Patients scheduled for elective Percutaneous Nephrolithotomy.

Exclusion Criteria:

• Contraindication to local anesthesia :

Allergy to local anaesthetics , Infection at the site of injection , Coagulopathy

• Chronic pain syndromes
• Prolonged opioid medication
• Patients who received any analgesic 24 h before surgery.