Abstract

Time course of the investigation. Subjects were sedated with dexmedetomidine (Dex) at a loading dose of 6 mcg/kg/h for 5 minutes and a continuous infusion dose of 0.2 mcg/kg/h for 25 minutes. The recovery process was observed for 60 minutes after cessation of the Dex infusion. (Control value was not measured in Ramsay score.)

Changes in tidal volume (TV), respiratory rate (RR), and minute volume (MV). TV decreased significantly from 5 minutes to 30 minutes after the start of dexmedetomidine (Dex) infusion. However, RR and MV did not show significant changes. TV decreased significantly from an average of 580 mL (control value) to approximately 430 to 470 mL (P < .05).

Changes in end-tidal carbon dioxide (E_TCO₂) and oxygen saturation (SpO₂). Respiratory rate (RR) and SpO₂ did not show significant changes. Sedation with dexmedetomidine (Dex) had no effect on E_TCO₂ and SpO₂.

Changes in mean arterial pressure (MAP) and heart rate (HR). The transient increase in MAP was observed at 5 minutes after the start of dexmedetomidine (Dex) infusion (not significant); MAP decreased significantly from an average of 86 mm Hg (control value) to approximately 70 to 77 mm Hg over 80 minutes since 10 minutes after the start of Dex infusion (P < .05). HR decreased significantly since 5 minutes after the start of Dex infusion, and HR decreased significantly from an average of 65 beats per minute (bpm) (control value) to approximately 53 to 57 bpm (P < .05).

Changes in bispectral index (BIS) and Ramsay score (RS). BIS decreased significantly from 10 minutes after the start of dexmedetomidine (Dex) infusion to 30 minutes after the end of Dex infusion (P < .05). RS showed the optimal sedation level from 10 minutes to 30 minutes after the start of Dex infusion.

Changes in Trieger dot test plus error ratio test (TDT p.e.r.) and 1-leg standing with eyes closed test (O-L test). TDT p.e.r. increased significantly at 5 and 10 minutes from the end of dexmedetomidine (Dex) infusion (P < .05). All subjects passed the O-L test at 60 minutes after cessation of Dex infusion.

Amnesia. Amnesia was recognized with a 27-gauge needle prick test performed in 69% of subjects at 21 minutes after the start of dexmedetomidine (Dex) infusion.