Effect of Intravenous or Intrathecal Dexmedetomidine on Bupivacaine Spinal Block in Lower Abdominal Surgery

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.