This study is a comparative study will be carried out after approval by the Local Ethical Committee in Al-Azhar University hospital (Assiut) and after obtaining patients' written informed consent.

50 ASA physical status I-II aged 20-60 years of both sexes scheduled for lower abdominal surgery with an expected duration of 90-120 min under spinal anesthesia will be enrolled in this study

Primary outcome :

- The onset and duration of sensory and motor blockade ,Postoperative analgesic efficacy .

Secondary outcomes :

- to assess the effect on hemodynamics and postoperative analgesic requirement All patients will be assigned randomly into two groups :group 1 (the I.V group ) Patients in the I.V group (n = 25) received intrathecal hyperbaric bupivacaine 15 mg together with NSS 0.5 ml, followed by an I.V bolus dose of dexmedetomidine 0.5 μg/kg over 10 min and then an I.V infusion of a maintenance dose of 0.5 μg/kg/h (200 μg dexmedetomidine in 2 ml added to 48 ml NSS yielded dexmedetomidine 4 μg /ml) for the entire period of surgery. intrathecal group (n = 25) patients received intrathecal 15 mg hyperbaric bupivacaine (Marcaine 0.5%; Astra Zeneca, UK) together with 5 μg Dexmedetomidine (Precedex; Abbott; Chicago, IL, USA, 100 μg/ml diluted with normal saline solution (NSS) to 10 μg/ml), followed by an NSS I.V bolus and an I.V infusion of maintenance volume equivalent to that of the I.V group throughout the entire period of the surgery.

Neuraxial anesthesia and analgesia provide a solid analgesic effect by inhibiting nociceptive transmission from peripheral to the central neuronal system . However, their analgesic advantages might be limited by the short life of current local anesthetics (LAs). Therefore, adjunct analgesic strategy is an alternative to prolonging the analgesic duration and decreases the potential risk of side effects by reducing the dose of LA.

This study is a comparative study will be carried out after approval by the Local Ethical Committee in Al-Azhar University hospital (Assiut) and after obtaining patients' written informed consent. inclusion criteria will be: 50 ASA physical status I-II aged 20-60 years of both sexes scheduled for lower abdominal surgery with an expected duration of 90-120 min under spinal anesthesia will be enrolled in this study. Exclusion criteria

• Patient refusal.
• history of cardiac, hepatic, neurological, or renal disease.
• BMI ≥30kg/ m2 (Morbid obesity).
• Patients with diabetes mellitus.
• history of allergy to study drugs, any contraindication for regional anesthesia
• Coagulopathy.
• failed or unsatisfactory spinal block. Study tools All patients will be assigned randomly into two groups :group 1 (the I.V group ) Patients in the I.V group (n = 25) received intrathecal hyperbaric bupivacaine 15 mg together with NSS 0.5 ml, followed by an I.V bolus dose of dexmedetomidine 0.5 μg/kg over 10 min and then an I.V infusion of a maintenance dose of 0.5 μg/kg/h (200 μg dexmedetomidine in 2 ml added to 48 ml NSS yielded dexmedetomidine 4 μg /ml) for the entire period of surgery.

intrathecal group (n = 25) patients received intrathecal 15 mg hyperbaric bupivacaine together with 5 μg Dexmedetomidine100 μg/ml diluted with normal saline solution (NSS) to 10 μg/ml), followed by an NSS I.V bolus and an I.V infusion of maintenance volume equivalent to that of the I.V group throughout the entire period of the surgery.

Inclusion Criteria:

• ASA physical status I-II
• lower abdominal surgery
• Aged 20-60 years of both sexes

Exclusion Criteria:

• Patient refusal.
• history of cardiac, hepatic, neurological, or renal disease.
• BMI ≥30kg/ m2 (Morbid obesity).
• Patients with diabetes mellitus.
• history of allergy to study drugs, any contraindication for regional anesthesia
• Coagulopathy.
• failed or unsatisfactory spinal block.

analytical data will be available