Comparison of several dosing schedules of intravenous dexmedetomidine in elderly patients under spinal anesthesia

BACKGROUND: Many clinicians have probably used subjective, unscientific methods for dose reduction to avoid overdose in elderly patients. The aim of this study was to compare several dosing schedules of intravenous dexmedetomidine (DEX) to identify the appropriate dosing schedule within the therapeutic dose range for adequate sedation of elderly patients under spinal anesthesia. METHODS: After administration of spinal anesthesia, a loading dose of DEX was injected over 10 min in three groups with the following dosages: group A, 1.0 μg/kg of actual body weight; group B, 1.0 μg/kg of ideal body weight (IBW); and group C, 0.8 μg/kg of IBW. Then, a maintenance infusion (0.5 μg/kg of each BW/h) was administered. The bispectral index score (BIS), the time required to reach BIS 80, airway obstruction score, and the occurrence of bradycardia were recorded. RESULTS: The changes in the BIS among the groups over time were found to have statistically significant differences (P < 0.001). The times required to reach BIS 80 were 6.1 ± 5.3 min, 5.0 ± 3.6 min, and 11.0 ± 8.6 min in groups A, B, and C, respectively (P < 0.001). The airway obstruction score and the frequency of bradycardia did not have statistically significant differences among the groups. CONCLUSIONS: An initial loading dose of DEX that is 0.8 μg/kg of IBW over 10 min, followed by an infusion rate of less than 0.5 μg/kg of IBW/h may be adequate for sedation in elderly patients receiving spinal anesthesia.