Background: Intravenous dexmedetomidine may prolong spinal anesthesia but can reduce heart rate and blood pressure. This study evaluated its effect on sensory and motor block characteristics and perioperative hemodynamics during lower-extremity orthopedic surgery.

Methods: In this single-center randomized controlled study, 25 adults with American Society of Anesthesiologists physical status I-II undergoing lower-extremity surgery under spinal anesthesia were allocated by sealed-envelope selection to dexmedetomidine (Group D; n=12) or saline control (Group C; n=13). All patients received 10 mg intrathecal isobaric bupivacaine. Group D received intravenous dexmedetomidine 1 µg/kg over 10 minutes followed by 0.2 µg/kg/h; Group C received volume-matched 0.9% saline. Sensory block was assessed by pinprick, motor block by the Bromage scale, and heart rate and blood pressure at prespecified perioperative time points. Between-group comparisons used the Mann-Whitney U test.

Results: Median sensory block onset was 1.0 versus 1.2 minutes (p=0.040) and motor block onset was 2.0 versus 2.5 minutes (p=0.025) in Groups D and C, respectively. Sensory block duration was 125 versus 85 minutes (p<0.001), and motor block duration was 102.5 versus 65 minutes (p=0.002). Heart rate was lower in Group D after the spinal technique and at 15 minutes, 40 minutes, the end of infusion, and 40 minutes after infusion (all p<0.05). Between-group blood pressure differences did not meet the prespecified p<0.05 threshold. No severe hemodynamic events were reported in the source study.

Conclusions: Intravenous dexmedetomidine was associated with longer sensory and motor block duration and modestly faster block onset, but also with lower perioperative heart rate. Given the small sample, absence of reported blinding, and multiple time-point comparisons, these findings should be confirmed in larger, prospectively registered trials.