Efficacy and Safety of 5 µg and 10 µg Dexmedetomidine With Hyperbaric Levobupivacaine in Lower-Limb Surgeries Under Spinal Anesthesia: A Randomized Controlled Study.

BACKGROUND: Dexmedetomidine is used as an intrathecal adjuvant to enhance the quality and duration of spinal anesthesia (SA). However, the extent to which different intrathecal doses affect the characteristics of the block and hemodynamic responses remains unclear. OBJECTIVE: To compare the efficacy and safety of intrathecal 5 µg versus 10 µg dexmedetomidine added to 0.5% hyperbaric levobupivacaine in patients undergoing lower-limb surgery. METHODS: 60 American Society of Anesthesiologists (ASA) I-II adults scheduled for elective lower-limb orthopedic and soft-tissue procedures were randomized into two groups. Group D5 received 5 µg dexmedetomidine, and Group D10 received 10 µg intrathecally with hyperbaric levobupivacaine. Sensory and motor block characteristics were assessed every three minutes until maximum levels were achieved. Hemodynamic parameters, including heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP), were monitored at predefined intervals. The primary outcome was the duration of sensory block; secondary outcomes included onset time, motor block duration, and intraoperative hemodynamic changes. RESULTS: Group D10 reached maximum sensory block (3.65 ± 1.15 vs. 4.40 ± 1.22 min; p = 0.017) and maximum motor block (6.05 ± 1.30 vs. 7.90 ± 2.12 min; p = 0.0001) significantly faster than Group D5. The duration of sensory block was also longer in Group D10. Bradycardia and hypotension occurred more frequently in Group D10 but were transient and managed without complications. CONCLUSION: Both doses enhanced SA characteristics. The 10 µg dose produced faster onset and longer duration of block but with a higher incidence of manageable hemodynamic effects. Selection of dose should balance the need for prolonged anesthesia with safety considerations.