The study aims to compare the efficacy of different doses of intrathecal dexmedetomidine on hemodynamic parameters and block characteristics after ropivacaine spinal anesthesia in lower-limb orthopedic surgery. In a double-blind trial, 90 patients undergoing spinal anesthesia for lower-limb orthopedic surgery were included and then randomly assigned to three groups; dexmedetomidine 5 μg/kg, dexmedetomidine 10 μg/kg and placebo. Blood pressure, heart rate, and oxygen saturation were recorded in the three groups at the first 15 minutes and then every 15 to 180 minutes at recovery by a resident anesthesiologist, as well as sensory-motor block onset. The visual analog scale scores for the assessment of pain were recorded at recovery, and 2, 4, 6, and 12 hours postoperatively and the data were analyzed by Stata software. The onset and time to achieve sensory block to ≥ T8 were faster in the 10 μg/kg dexmedetomidine group than the other groups (P = 0.001). The Bromage score was higher in the 10 μg/kg dexmedetomidine group (P = 0.0001) with lower pain score as compared with the 5 μg/kg dexmedetomidine and placebo groups (P = 0.0001). Therefore, an increase in dexmedetomidine hastens the onset of sensory-motor block but not causes side effects. This study was approved by the Ethical Committee of Arak University of Medical Sciences in 2017 (Ethical Code: IR.ARAKMU.REC.1396.37), and the trail was registered and approved by the Iranian Registry of Clinical Trials in 2017 (IRCT No. IRCT2017070614056N12).
Keywords: block characteristics; blood pressure; dexmedetomidine; heart rate; hemodynamic changes; motor block; oxygen saturation; randomized clinical trial; ropivacaine; sensory block.