Dexmedetomidine combined with midazolam vs. dexmedetomidine alone for sedation during spinal anesthesia

BACKGROUND: Dexmedetomidine is a useful sedative agent for spinal anesthesia. However, it has been reported that dexmedetomidine decreases heart rate in a dose-dependent manner. In the current study, we compared the administration of a bolus dose of midazolam and bolus loading of dexmedetomidine over 10 min with the goal of identifying an additional method of sedation. METHODS: Ninety patients classified as American Society of Anesthesiologists physical status I-II who were undergoing spinal anesthesia were divided into two groups. In the midazolam and dexmedetomidine combined group (group MD), 10 min after bolus loading of 0.05 mg/kg midazolam, 0.5 µg/kg/h dexmedetomidine was continuously infused. In the dexmedetomidine group (group D), 1 µg/kg dexmedetomidine was infused over 10 min, and then 0.5 µg/kg/h dexmedetomidine was continuously infused. RESULTS: At 10 min, the sedation depth of the two groups was almost equal. In both groups, the bispectral index was within the optimal score range of 55-80 and the Ramsay Sedation Scale score was within the optimal range of 3-5. Satisfaction with sedation for both patient and surgeon did not differ between the two groups. At 10 min, heart rate was significantly lower (P < 0.010) in group D and mean blood pressure was significantly lower (P < 0.010) in group MD. The prevalence of bradycardia, hypotension, and hypoxia did not differ statistically between the two groups (P = 0.714, P = 0.089, P = 0.495, respectively). CONCLUSIONS: Midazolam bolus and dexmedetomidine continuous infusion (the regimen of group MD) may be an additional sedation method for patients who have severe bradycardia.