Effect of intravenous versus intrathecal low-dose dexmedetomidine on spinal block in lower limb orthopedic surgery

Abstract EN

Objectives The aim of this study was to investigate the effect of dexmedetomidine administered intravenously or intrathecally in prolonging spinal anesthesia using bupivacaine in patients undergoing lower limb orthopedic surgery.

Patients and methods Sixty adult patients classified as ASA I or II and scheduled for lower limb orthopedic surgery under spinal anesthesia were enrolled in this study.

Patients were randomly assigned into one of the three groups.

Group B (n = 20) was injected with 10 ml isotonic saline intravenously over 5 min immediately after patient has received intrathecal hyperbaric bupivacaine 12.5 mg; group IV (n = 20) was injected with dexmedetomidine 0.5 µg / kg intravenously diluted in 10 ml isotonic saline over 5 min immediately after patient has received intrathecal hyperbaric bupivacaine 12.5 mg; and group IT (n = 20) was injected with 10 ml isotonic saline over 5 min immediately after patient has received intrathecal hyperbaric bupivacaine 12.5 mg and dexmedetomidine 3 µg.

The onset time, maximum block level, time to maximum sensory and Bromage 3 motor block, duration of sensory and motor anesthesia, time to first analgesic request, and total analgesic consumption in the first 24 h were recorded.

Hemodynamics, side effects, and sedation scores were assessed.

Results Patients in groups IV and IT had a highly significantly longer sensory and motor block duration than patients in group B.

Both durations were significantly longer in the IT group than in the IV group.

The time to reach Bromage 3 motor block was significantly shorter in the IV and IT groups than in the B group, with no statistically significant difference between each other.

The systolic and diastolic blood pressures were comparable in the three groups intraoperatively and postoperatively.

Mean heart rate values were significantly decreased at 20–60 min in the IV group in comparison with the other two groups.

The time to first analgesic needed was significantly prolonged in groups IV and IT in comparison with group B.

The mean total consumption of intravenous tramadol postoperatively in the first 24 h was significantly decreased in groups IV and IT in comparison with group B.

Conclusion In bupivacaine spinal block, dexmedetomidine whether administered intravenously at a dose of 0.5 µg/kg or intrathecally in addition to bupivacaine at a dose of 3 µg produced a significant prolongation in the durations of the motor and sensory block, but that administered intrathecally produced more significant prolongation of effect than that administered intravenously, with preserved hemodynamic stability and lack of sedation.