title: Effective dose of dexmedetomidine to induce adequate sedation in elderly patients under spinal anesthesia.
abstract: BACKGROUND
  During sedation with dexmedetomidine, a dose adjustment may be needed based on the invasiveness of the procedure, the patient's general condition, and their age. We aim here to determine the effective dose (ED) of dexmedetomidine to induce an adequate depth of sedation in elderly patients undergoing spinal anesthesia.
  
  
  METHODS
  In this study, 47 patients aged 65 years or older, American Society of Anesthesiologists physical status I or II, undergoing spinal anesthesia were included. Patients were randomly allocated into group I, II, III, IV or V according to the dexmedetomidine loading dose of 0.1, 0.3, 0.5, 0.7 and 1.0 µg/kg, respectively. After spinal anesthesia, the assigned loading dose of dexmedetomidine was infused intravenously for 10 minutes, after which infusion was maintained at a rate of 0.3 µg/kg/h for the next 10 minutes in all groups. We assessed the depth of sedation with the Ramsay sedation scale every five minutes and measured vital signs and the oxygen saturation. The ED50 and ED95 of dexmedetomidine to obtain adequate sedation (Ramsay sedation score ≥ 3) upon the completion of the loading dose were calculated with logistic regression.
  
  
  RESULTS
  The ED50 and ED95 of dexmedetomidine for adequate sedation were 0.29 µg/kg (95% confidence intervals [CI] 0.14-0.44) and 0.86 µg/kg (95% CI 0.52-1.20), respectively. Hypotension was frequent in groups IV, V compared to groups I, II, III (31.6 vs. 3.6%, P = 0.013).
  
  
  CONCLUSIONS
  ED95 of dexmedetomidine loading dose for adequate sedation is 0.86 µg/kg. However, dose higher than 0.5 µg/kg can lead to hemodynamic instability.
authors.affiliation: Department of Medicine, Jodo Subcenter, Jindo Public Health Center, Jindo, Korea.
authors.forename: Ki-Ho
authors.initials: KH
authors.lastname: Ko
authors.affiliation: Department of Anesthesiology and Pain Medicine, Sanggye Paik Hospital, Inje University College of Medicine, Seoul, Korea.
authors.forename: In-Jung
authors.initials: IJ
authors.lastname: Jun
authors.affiliation: Department of Anesthesiology and Pain Medicine, Sanggye Paik Hospital, Inje University College of Medicine, Seoul, Korea.
authors.forename: Sangseok
authors.identifier: 0000-0001-7023-3668
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Anesthesiology and Pain Medicine, Sanggye Paik Hospital, Inje University College of Medicine, Seoul, Korea.
authors.forename: Yunhee
authors.initials: Y
authors.lastname: Lim
authors.affiliation: Department of Anesthesiology and Pain Medicine, Sanggye Paik Hospital, Inje University College of Medicine, Seoul, Korea.
authors.forename: Byunghoon
authors.initials: B
authors.lastname: Yoo
authors.affiliation: Department of Anesthesiology and Pain Medicine, Sanggye Paik Hospital, Inje University College of Medicine, Seoul, Korea.
authors.forename: Kye-Min
authors.identifier: 0000-0003-1298-7642
authors.initials: KM
authors.lastname: Kim
keywords: Aged; Dexmedetomidine; Sedation; Spinal anesthesia