The aim of this study is to compare the addition of intrathecal dexmedetomidine or fentanyl as adjuvants to hyperbaric bupivacaine in the onset and duration of sensory and motor block, and postoperative analgesia.

The aim of this study is to compare the addition of intrathecal dexmedetomidine or fentanyl as adjuvants to hyperbaric bupivacaine in the onset and duration of sensory and motor block, and postoperative analgesia. All patients will be assessed preoperatively by careful history taking, full physical examination, and laboratory evaluation. An informed written consent will be taken from every patient just before the surgery. On arrival to the operating room, baseline parameters such as ECG, mean arterial blood pressure, heart rate, and oxygen saturation will be recorded. Intravenous line will be inserted and IV Ringer's solution will be started, 500ml bolus will be given as a preload over 20 min before performing spinal anesthesia and maintenance volume of 10ml\kg.

For each group, patients will be put in sitting position, lumbar puncture will be performed under complete aseptic precautions, local anesthesia will be administered by infiltration of the skin and subcutaneous tissues with 3-5 ml lidocaine 1% at L3-L4 and A 25-G needle will be used.

• Group 1: (Control group) (20 cases): patients will receive 3 ml (15mg) of 0.5% hyperbaric bupivacaine+0.5 ml of normal saline intrathecally.
• Group 2: (Fentanyl group) (20 cases): patients will receive 3 ml (15 mg) of 0.5% hyperbaric bupivacaine+0.5 ml (25μg) of fentanyl intrathecally.
• Group 3: (Dexmedetomidine group) (20 cases): patients will receive 3 ml (15 mg) of 0.5% hyperbaric bupivacaine+0.5 ml (5μg) of diluted dexmedetomidine intrathecally.

Inclusion Criteria:

• • ASA I or ASA II patients Scheduled for pott's, of either sex.

  • Age 21-55 years.
  • Height 160 to 190 cm.
  • BMI ≤40.
  • Procedure duration ≤ 90 minutes

Exclusion Criteria:

• • Patients with known neurologic and psychiatric illness.

  • Contraindications for spinal anesthesia as patient refusal, bleeding or coagulation test abnormalities, local skin infection at spinal lumbar region, raised intracranial pressure and hypovolemia.
  • Spine abnormalities.
  • Systemic disorders like hematological, respiratory, cardiac, renal or hepatic insufficiency.
  • Allergy to any of the drugs used in the study.
  • Women with pregnancy and lactation