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

Inclusion Criteria: * ASA I, ASA II or ASA III patients scheduled for hip arthroplasty surgeries under spinal anaesthesia. Age \> 20 years. Exclusion Criteria: * Patient refusal * Patients with known neurologic and psychiatric illness. * Contraindications for spinal anaesthesia as bleeding or coagulation test abnormalities, local skin infection at spinal lumbar region, raised intracranial pressure and hypovolemia. * Height \<150 cm. * Systemic disorders like hematological, respiratory, cardiac, renal or hepatic insufficiency. * Allergy to any of the drugs used in the study.