Dexmedetomidine and Fentanyl As Adjuvants to Hyperbaric Bupivacaine for the Prevention of Post-spinal Shivering in Hip Arthroplasty Surgeries

the preservative-free dexmedetomidine 100 μg/ml will be loaded into a 100-unit insulin syringe (1 μg/unit) and 5 units will be added to 4 ml (20 mg) of 0.5% hyperbaric bupivacaine

Fentanyl (Fentanyl Hameln® 0.1mg/2ml) 25 mcg will be given intrathecally added to 4 ml (20 mg) of 0.5% hyperbaric bupivacaine