Influence Of Low Dose Intrathecal Naloxone On Bupivacaine - Fentanyl Spinal Anaesthesia For Lower Limb Orthopedic Surgery In Elderly Patients

"Bupivacaine-Fentanyl (BF) group (46 patients): will receive spinal anaesthesia with 12.5 mg hyperbaric Bupivacaine 0.5% (2.5 mL) plus 25 µg Fentanyl (0.5 mL) and (0.5 mL) normal saline added in the same syringe in a total volume of 3.5 mL.~Bupivacaine-Fentanyl-Naloxone (BFN) group (46 patients): will receive spinal anaesthesia with 12.5 mg hyperbaric Bupivacaine 0.5% (2.5 mL) plus 25 µg Fentanyl (0.5 mL) and 20 µg Naloxone (prepared in 0.5 mL normal saline) added in the same syringe in a total volume of 3.5 mL."