A Comparison of Intravenous Sedation With Two Doses of Dexmedetomidine: 0.2 µg/kg/hr Versus 0.4 µg/kg/hr
The present study investigated the physiologic and sedative effects between two different continuous infusion doses of dexmedetomidine (DEX). Thirteen subjects were separately sedated with DEX at a continuous infusion dose of 0.2 µg/kg/hr for 25 minutes after a loading dose of 6 µg/kg/hr for 5 minutes (0.2 group) and a continuous infusion dose of 0.4 µg/kg/hr for 25 minutes after a loading dose of 6 µg/kg/hr for 5 minutes (0.4 group). The recovery process was then observed for 60 minutes post infusion. The tidal volume, mean arterial pressure, and heart rate in both groups decreased significantly during infusion, but they were within a clinically acceptable level. A Trieger dot test plot error ratio in the 0.4 group was significantly higher than that in the 0.2 group until 15 minutes post infusion. Sedation appears to be safe at the infusion doses of DEX studied. However, increasing maintenance infusion doses of DEX from 0.2 µg/kg/hr to 0.4 µg/kg/hr delays some recovery parameters.Abstract
Time course of the investigation. The same subjects were sedated separately with dexmedetomidine (DEX) at a continuous infusion dose of 0.2 µg/kg/hr for 25 minutes after a loading dose of 6 µg/kg/hr for 5 minutes and a continuous infusion dose of 0.4 µg/kg/hr for 25 minutes after a loading dose of 6 µg/kg/hr for 5 minutes. Then, recovery process was observed for 60 minutes after the end of DEX infusion. (Baseline value was not measured in Ramsay score and one-leg standing with eyes closed test [O-L test] in the 0.4 group was observed for 90 minutes.)
Changes in tidal volume (TV), respiratory rate (RR), minute volume (MV), and end-tidal carbon dioxide (ETCO2). TV in both groups decreased significantly from 5 minutes to 30 minutes after the start of dexmedetomidine (DEX) infusion in spite of no significant changes in RR, MV, and ETCO2. TV in the 0.2 group decreased significantly from an average of 559 mL (baseline value) to 430–470 mL (P < .05). TV in the 0.4 group decreased significantly from an average of 551 mL (baseline value) to 410–460 mL (P < .05). However, there was no significant change in TV, RR, MV, and ETCO2 between both groups.
Changes in mean arterial pressure (MAP) and heart rate (HR). In both the 0.2 group and the 0.4 group, the transient increase in MAP was observed at 5 minutes after the start of dexmedetomidine (DEX) infusion (not significant). MAP in the 0.2 group decreased significantly from an average of 86 mm Hg (baseline value) to 70–77 mm Hg over an 80-minute time period since 10 minutes after the start of DEX infusion (P < .05). MAP in the 0.4 group decreased significantly from an average of 83 mm Hg (baseline value) to 67–75 mm Hg over an 80-minute time period since 10 minutes after the start of DEX infusion (P < .05). HR in both groups decreased significantly since 5 minutes after the start of DEX infusion, and from an average of 65 beats per minute (baseline value) to 53–57 beats per minute (P < .05). However, there was no significant change in MAP and HR between both groups.
Changes in bispectral index (BIS) and Ramsay score (RS). BIS in both groups decreased significantly from 10 minutes after the start of dexmedetomidine (DEX) infusion to 30 minutes after the end of DEX infusion (P < .05). However, there was no significant change on the BIS monitor between both groups. RS in the 0.4 group reached the optimal sedation level earlier than that in the 0.2 group, and there were significant differences between groups at 25 and 30 minutes after the start of DEX infusion (P < .05).
Changes in Trieger dot test plot error ratio (TDT p.e.r.). TDT p.e.r. in the 0.2 group increased significantly at 5 and 10 minutes from the end of dexmedetomidine (DEX) infusion (P < .05), and that in the 0.4 group increased significantly at 5, 10, and 15 minutes from the end of DEX infusion (P < .05). TDT p.e.r. in the 0.4 group was significantly higher than that in the 0.2 group at 5, 10, and 15 minutes from the end of DEX infusion (P < .05).
One-leg standing with eyes closed (O-L) test. In the 0.2 group, all subjects passed the O-L test at 60 minutes after the end of DEX infusion. However, all subjects in the 0.4 group passed the O-L test at 90 minutes after the end of DEX infusion.
Amnesia of 27-gauge needle prick test at 21 minutes after the start of dexmedetomidine (DEX) infusion was recognized in 69% of subjects in the 0.2 group and in 85% of them in the 0.4 group. In the comparison between both groups, no significant difference was recognized in amnesia of 27-gauge needle prick test.
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