Comparison of Effectiveness of Dexmedetomidine versus Nalbuphine as an Adjuvant with Intrathecal 0.5 Percent Isobaric Levobupivacaine in Lower Limb Orthopaedic Surgeries – A Randomized Double - Blind Controlled trial.

All patients will be kept fasting for 6 hours prior to surgery.In the operating room, each patient will be identified and then placed on a operating table, routine non-invasive monitor will be applied. Baseline pulse rate, ECG, respiratory rate, blood pressure (SBP and DBP) and oxygen saturation will be recorded Intravenous access will be gained using 18G venous catheter and preloading will be done with 10mL/kg Ringer Lactate solution within 20 minutes of procedure. Premedication inj. Ondansetron 0.08mg/kg IV will be given before the administration of spinal Anaesthesia. All equipment and drugs necessary for resuscitation and general Anaesthesia will be kept ready. One member of the team (other than PI and Co-PI) will be assigned to prepare the drug under aseptic precautions as per the group while the anaesthesiologist performing the block and the patient, both will be unaware about the drug. Study drug : 0.5% Isobaric Levobupivacaine(3ml)+Dexmedetomidine 5 µg(0.05 ml drug from tuberculin syringe diluted in Distilled water (0.05ml) ) or Nalbuphine 1mg (0.1ml drug from tuberculin syringe). Under all aseptic and antiseptic precautions, patient placed in sitting position, in  L3-L4 interspace, overlying skin will be anaesthetized by  local infiltration with  xylocaine 2%. After that subarachnoid block will be attempted with 23G Quincke spinal needle with midline approach and the total 3.1 ml of study drug will be injected after ensuring the free and clear flow of cerebrospinal fluid from the needle. Desirable level of spinal anaesthesia will be considered T10. After injection of drug, patient will be immediately turned supine. All patients will be given supplemental oxygen by Nasal prong  at the flow rate of 2L/min. The time of injection will be noted as Time “0” and assessment of sensory and motor characteristics of subarachnoid block will be done and  vitals will be noted at every 2 minutes till 10 minutes, every 15 minutes till regression to S1 level of sensory block, every 30 minutes till Bromage “0”.Segmental level of sensory block to pin prick will be assessed by using a sterile hypodermic needle bilaterally along the midclavicular line.