ED50 of Dexmedetomidine as an Adjuvant to 0.5% Hyperbaric Bupivacaine 12.5 mg for Spinal Anesthesia in Hip and Knee Surgery: An Up-and-Down Method Approach

Inclusion Criteria: * 18-60 years old * Pelvic or knee surgery patient with American Society of Anesthesiologists physical status I - III with epidural spinal anesthesia * Body mass index 18-35 kg/m2 * Body height 150-180 cm * Willing to become a research participant Exclusion Criteria: * Have a history of allergy to bupivacaine or dexmedetomidine * Have sensory or motoric disabilities in the lower extremity contralateral to the surgery area * Have a history of congestive heart failure and/or heart rhythm disorder * Have regional anesthesia contraindication