Effect of intravenous dexmedetomidine on sensory block duration in spinal anesthesia for lower limb surgery: a randomized controlled trial

Study objective

To study the effect of Intravenous (IV) dexmedetomidine during spinal anesthesia on duration of sensory block and postoperative analgesia in patients undergoing lower limb orthopedic surgery.

Design

Prospective randomized double blind controlled trial.

Intervention

Patients in intervention (DX) group received 0.5 mcg.kg^-1 IV dexmedetomidine over 10 min. Spinal anesthesia was administered and an infusion of dexmedetomidine 0.5 mcg.kg^-1.h^-1 was given throughout surgery.

Measurements

Onset time of sensory and motor block, maximum height of sensory block and duration of sensory and motor block were assessed. Intraoperative Heart Rate (HR), Blood Pressure (BP), Peripheral Oxygen Saturation (SpO₂), sedation scores, postoperative pain scores, time to requirement of first analgesic and analgesic consumption over first 24h were noted.

Results

Data of 58 ASA I/II adults was analyzed. Duration of sensory block, defined as time to two-dermatome regression, was 137.03 ± 25.02 min in DX group and 79.45 ± 11.27 min in the NS group (p = 0.000). Onset of sensory and motor block and maximum height of sensory block were similar. Postoperative VAS scores were lower in the DX group at 4h and 24h (p = 0.001, p 0.0001) and comparable at 0h, 8h and 12h. Time to requirement of postoperative analgesia was longer in the DX group (p < 0.001) and requirement of postoperative analgesics was higher in the NS group. Sedation scores and incidence of bradycardia were higher in the DX group, but hypotension was similar.

Conclusion

IV dexmedetomidine (0.5 mcg.kg^-1 followed by 0.5 mcg.kg^-1.h^-1) resulted in extended sensory and motor block, prolonged postoperative analgesia and reduced postoperative analgesic consumption with minimal side effects.